'A47-221-4M -L TEXAS AGRICULTURAL EXPERIMENT STATION AGRICULTURAL AND MECHANICAL COLLEGE 0]? TEXAS ' w. n. BIZZELL, President BULLETIN NO. 273 JANUARY, 1921 DIVISION OF PLANT PATHOLOGY AND PHYSIOLOGY I PINK ROOT DISEASE OF ONIONS AND ITSCONTROL IN TEXAS B. YOUNGBLOOD, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS STATION STAFFT ADMINISTRATION B. YOUNGBLOOD, M. S., Director_ CHAS. A. FELKEB, Chief Clerk A. S. WARE, Secretary _ _ A. D. JACKSON, Executive Assistant CHARLES Sosoux. Technical Assistant VETERINARY SCIENCE _ *M. FRANCIS, D. V. M., Chief _ H. Scrmmr, D. V. S., Veterinarian _ D. H. BENNETT, V. M. D., Veterinarian CHEMISTRY _ G. S. FRAPS, Ph. D., Chief; State Chemist S. E. AsBURY, M. S., Assistant Chemist S. LOMANITZ, B. S., Assistant Chemist J. B. SMITH, B. S., Assistant Chemist . WALDO WALKER, Assistant Chemist HORTICULTURE H. NEss, M. S., Chief W S. HOTCHKISS, Horticulturist ANIMAL INDUSTRY J. M. Jorms, A. M., Chief; Sheep and Goat Investigations R. M. SRERWooD, B. S., Poultry Husband- man ....... .. . Dairy Ifusbandmon G. R. WARREN, B. S., Animal Husbandman in Charge of Swine investigations _ R. A. BREWER, B. S., Assistant AnimalHus- bandman ENTOMOLOGY _ M. C. TANQUARY, Ph. D., Chief; State, Ento- moloaist H. J. REmRARn, B. S., Entomologist L. R. WATSON, A. M., Apiarist _ C. S. RUDE, B. S., Assistant Entomologist AGRONOMY _ A. B. CONNER, B. S., Chief A. H. LEIDIGH, B. S., Agronomist E. B. REvNoLns. M. S., Agronpmist E. W. GEYER, B. S., Agronomist PLANT PATHOLOGY AND PHYSIOLOGY J. J. TAUBENHAUS, Ph. D., Chief FEED CONTROL SERVICE F‘. D. FULLER, M. S., Chief S. D. PEARCE, Executive Secretary FORESTRY ‘ E. O. SIECKE, B. S., Chief; State Forester PLANT BREEDING .......................... ..,......, Chief FARM AND‘ RANCH ECONOMICS A. B. Cox, Ph. D., Chief SOIL SURVEY **W'. T. CARTER, JR.. B. S., Chief T. M. BusnNELL, B. S., Soil Surveyor H. W. HAWKER, Soil Surveyor SUBSTATIONS No. 1. Beeville, Bee County ‘ I. E. COWABT, M. S., Superintendent No. 2. Troup, Smith County V W. S. Horcmuss, Superiutenaent No. 3. Angleton, Brazoria County V. E. HAFNER, B. S., Superintendent No. 4. Beaumont, Jeflerson County A. H. PRINCE, B. S., Superintendent No. 5. Temple, Bell County D. T. KILLOUGR, B. S., Superintendent No. 6. Denton, Denton County C. H. McDowEnL, B. S., Superintendent No. 7. Spur, Dickens County B. E. DICKSON, B. S., Superintendent 1'As o_f February 1, 1921. iReslgned. ** No. 12. No. 8. Lubbock, Lubbock County R. E. KARPER, B. S., Superintendent No. 9. Pecos, Reeves County V. L. CORY, B. S., Superintendent No. 10. (Feeding and Breeding Substation), College Station, Brazos County / L. J. IVICCALL, Superintendent No. 11. Nacogdoches, Nacogdoches County G. T. McNEss, Superintendent Chillicothe, Hardeman County A. B. CRON, B. S., Superintendent No. 14. I Sonora, Sutton-Edwards Countlel E. M. PETERS, B. S., Superintendent flu cooperation with the School of Veterinary Medicine, A. 8c M. College of Texas. "In cooperation with the United States Department of Agriculture. BULLETIN’ No. 273. . JANUARY, 19211. PINK ROOT DISEASE OF ONIONS AND ITS CONTROL IN TEXAS BY J. J. TAUBFNHALUS AND FREDERICK WV. 1\IALLY* INTRODUCTION Onions are considered an important economic crop in Texas. Ber- muda. onions are grown especially in the Rio Grands Valley and in Webb, Dimmit, Zavala, La Salle, and Frio Counties. During the last fifteen years a disease, popularly known as pink root, has caused con- siderable damage, and it seriously threatens the profitable culture of onions on (liseased lands. The acuteness of the situation in 1915 made the junior Writer call on the Texas Agricultural Experiment Station for assistance in. solving this problem. An arrangement Was accord- ingly made, whereby the Division of Plant Pathology and Physiology of the Texas Agricultural lflxperiment Station, in cooperation with the growers and the county agent of Webb County, agreed to undertake the Work ‘JV1II1 the hope of determining the cause of the pink root dis- ease, and, if possible, to devise practical methods of control. With the exception of all the laboratory experiments. the junior author has whole- heartedly cooperated in all the field Work for which he shares equal responsibility. - There is no doubt but that pink root has existed a long time in the onion district of Texas, and probably in other states of the Union. Its economicimportance was recognized when the Texas acreage of Ber- muda onions had expanded, and the Texas Bermuda onic-n was recog- nized among the northern markets as a very desirable early crop. Dr. O. M. Ball, Professor of Biology of the Texas A. and M. College, claims that he saw this disease some fifteen or twenty years ago. There seems no doubt but that he then observed the same trouble which is described in the present bulletin. A careful search through the literature, how- ever, shows no mention whatsoever of any description before of an onion trouble that would correspond to the pink root disease now under dis- cussion. It seems that at an earlv date Mr. W. M. Gilbert of the United States Department of Agriculture had at one time worked on this disease. In ansuter to our inquiry, under date of May 15, 1918, as to whether or not he ever published anvthing on it, Mr. Gilbert stated, “So far as I know, there are no publications on this disease.” The senior authorI in 1917 and later in 1918f was first to call atten- tion to it in literature. *County Agent, Webb County, Laredo, Texas. ITaubenhaus. IT. J. Pink root, a new disease of onions in Texas, Phytopatli, 7:59, 1917 (Abstract). TDiseases of Truck Crops, 1918. (E. P, Dutton Co, New You-Ir.) 4 TEXAS AGRICULTURAL EXPERIMENT STATION. ECONOMIC IMPORTANCE It is not possible to state definitely the money loss incurred from pink root in Texas during the last fifteen years. Our studies date back only four years, and our estimates necessarily apply to that time. In gen- eral, the conservative estimator may easily place the losses from pink root, in badly diseased fields, from 35 0r 4-3 per cent. t0 an occasional total failure. Assuming a normal yield on a healthy field to average about 400 crates per acre, one may see that the losses from pink root, all things being equal, will vary according to the following conditions: (1) The yields will be reduced When slightly or badly infected sets are planted in a healthy soil, Specific instances in many cases have shown a decided decrease in yield from 25 to '75 crates per acre or a direct loss of 6 to 18 per cent. i-Similar losses will occur when healthy sets are planted in a soil which is infected with pink root. (2) Heavy loss Will occur when badly- diseased sets are planted on badly infected pink root land, in which ease there will be a decrease of from 100 t0 200 cirates per acre or a direct loss of 25 to 50 per cent. Assuming that the average normal price to the onion growers the past few years to be $2.00 per crate in the April market and $1.50 per crate in the May market, one can readily see that a loss of 100 to 200 crates per acre will represent a total net Waste to the Texas grower of from $7200 to $400 per acre for April, and $150 to $300 for May. These estimates are given as a basis so that every grower will be able to figure his an- nual losses from pink root. relatively and according to current annual prices. As a result of our investigations, it can be definitely stated that pink root of onions is primarily a field disease, and its eifect is to re- duce directly the yields of marketable onions. Although pink root is only a field trouble, evidences tend to show that it is of economic importance as a transit disease. No extended investigations have as yet been carried out to determine definitely whether or not onions infected with the disease and coming from pink root land, have poorer carrying qualities in transit than those which are free from the disease and are groxvn on healthy soil. Recent ob- servations, however, tend to indicate that onions from pink root soil are more subiect to attacks of black mold decay, Aspergillus n/iger, and soft rot, Bacillus carato/vorus, than those which were grown on healthy land. This is especially true when the onions are dug during a wet spell, or when shipped under improper conditions of ventilation. In 191'?’ two crates of onions affected with pink root and two crates of healthy onions were secured from Laredo and shipped to Bryan, Texas. These were stored in crates under the living-house of the senior writer, and they were well protected from the sun. Within a period of four weeks the onions from pink root land decayed to the extent of 80 per cent. The nature of the (lecay was that of black mold, A. niger, and later it was followed by soft rot, B. ccmttororus. There were 11o indi- cations whatsoever that the pink root organism was the cause of any decay of the bulb itself. The onions from the healthy land kept four weeks longer, but finally rotted from the same cause as above. Further studies are now in progress to determine the effect of pink root on stor- age qualities of onions. For thepresent, it is safe to suggest that PINK Roor DISEASE OF ONIONS AND ITs OoNTRoL IN TEXAS. 5 onions grown on pink-root infected land have somewhat poorer carry- ing qualities, and they rot earlier under storage conditions. GEOGRAPHIC DISTRIBUTION OF PINK BOOT Pink root is Widely distributed, although its economic importance has not as yet become generally recognized in other states. The writer has had typical specimens of pink root sent to him by Professor Eliza- beth Smith of California. Likewise, Dr. J. C. Walker, in a letter dated September 11, 1919, states that he found pink root of onions near Stockton, California, in a. 2500-acre onion field, of which thirty acres were badly affected. with pink root. Yields on that area were reduced 50 per cent. He further states that pink root is common on matured bulbs on old onion soil in the Wisconsin onion section, but apparently the disease has done little damage as the roots only turn pink near harvesting time. In 1917‘ the junior writer personally col- lected typical specimens of pink root of onions in Des Moines, Iowa. The disease, which. was apparently doing but slight damage, was found on matured onions. Pink root of onions is prevalent in the Bermuda Islands, the original home of the Bermuda onion. Typical specimens of pink root of onions were collected by Professor Whetzel in the muck lands of New York and in the Bermuda Islands. Typical specimens of onions affected with pink root were received from Professor Leonard M. Outerbudge of the Department of Agriculture, East Bermuda. Cul- tures made from these specimens yielded a species of Fusarium which morphologically and physiologically seems to be identical with F. malli, the cause of pink root of onions in Texas. The writers have collected specimens of pink root of onions from practically every place visited in Texas where onions are grown, either commercially, or on a small scale. Table 1 indicates the present definite recorded distribution of the pink root disease of onions. Table 1.~—Distributi0n of Pink Root. State. County or City. Collector. Identified by. Date. Iowa... . . Des Moines . . . . . . . . F. W. Mally . . . . . . . . . J. J. Taubenhaus . . . . . . Aug. 9, 1917 Bermuda Paget East . . . . . . . . L. M. Outerbudge. . . . J. J. Taubenhaus . . . . .. April 14, 1920 _ June 16, 1920 Texas. . _. . Valley We_lls . . . . . . . I. A. Hiatt . . . . . . . . . . J. J. Taubenhaus . . . . . . Dec. 11 , 1920 California San Francisco . . . . . . R. Watsupka . . . . . . . . J. J. Taubenhaus . . . . . . Feb. 7, 1920 California Berkeley . . . . . . . . . . E. H. Smith . . . . . . . . . J. J. Taubenhaus . . . . . . Sept. 1919 Texas. . . . Webb, Laredo . . . . . . B. Richardson . . . . . . . R. H. Pond . . . . . . . . . . . Mar. 22, 1911 Texas. . . . Big Wells . . . . . . . . . . McFadyen . . . . . . . . . . . J. J. Taubenhaus . . . . . . April 10, 1916 Texas. . . . Pearsall . . . . . . . . . . . Ira Durrenberger. . . . . Ira Durrenberger . . . . . . April 25, 1915. Texas. . .. Mission . . . . . . . . . .. J. C. Walker . . . . . . . . . J. . ker . . . . . . . . .. April 3, 1918 Texas. . . . Webb. Laredo . . . . . . F. W. Mally . . . . . . . . . J. J. Taubenhaus . . . . . . Repeatedly Louisiana New Orleans. i . .. F. W. Mally . . . . . . . .. F. W. Mally . . . . . . . . . . Mar. 22. 1918 Texas. . . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and Mally. 1915 Texas. . . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and Mally. 1916 Texas. . . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and hdally. 1917 Texas. . . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and Mally. 1918 Texas. . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and Mally. 1919 Texas. . . . Webb and vicinity . Taubenhaus and Mally Taubenhaus and Mally. 1920 New York . . . . . . . . . . . . . . . . . . H. H. Whetzel . . . . . . . H. H. Whetzel . . . . . . . . 1920 a l It is, of course, speculative at this time to try to determine the place from which pink root was first introduced in Texas. Mention has al- ready been made of the presence of pink root of onions in Bermuda, \ O 6 . TExAs AGRICULTURAL EXPERIMENT STATION.- the home of the Bermuda onion. It is possible, or even probable that the disease has been brought in from there to Texas writh dry sets. Nowadays only onion seeds, and n0 dry sets, are purchased from the Bermuda Islands for seed-bed purposes 1n Texas. Texas growers do not plant dry sets extensively because of the fact that these produce an uneven crop with too many “splits” and “doubles.” It seems quite certain that in the early history of the onion culture i11 Texas, pink root, with imported dry sets, Was introduced from Bermuda. It is likely that pink root has been introduced in the same manner from Bermuda to the other states indicated in Table 1. RANGE OF HOBTS SUSCEPTIBLE TO PINK ROOT Mention has been made of the fact that practically all varieties of onions and garlic are susceptible to pink root. In order to determine definitely how many of the genera and species of Liliaceous plants are susceptible to pink root, various varieties were secured and planted as indicated in Table From Table 2, it is seen that neither the Nar- cissus, Tulip, Funkia, Iris, Fresia, Lillium, nor the Callas are subject to pink root. However, the onion, the shallot, the multipliers, and garlic, are all susceptible to the disease. In order to determine the susceptibility of various varieties of onions to pink root, tests were made in a field which was badly infected with pink root. The varieties tested were: The Yellow Dutch, Strasburg, the Yellow Denvers, Australian Brown, Large Red Globe, Large Red WVethersfield, Large White Globe, White Portugal (Philadelphia), White Silverskin, and Extra Early Bed. W'itl1 the exception of the last, all of the others showed a very high percentage of pink root, ranging from 21 to 36 per cent. in the seed bed, up to 100 per cent. in the field. The Extra Early Bed variety of onions showed a very small percentage of pink root, and it is probable that the seed under this name may have been the same, or similar to the Red Bermuda variety, which is fairly resistant to pink root. All the others tested were strictly north- ern varieties. RIumerous other field trials and observations have shown beyond doubt that the Denia onion, a Spanish variety, is especially sus- ceptible to pink root when transplanted in an infected pink root soil. It is safe to state that on badly infected soil, neither the Denia nor any other of the Spanish varieties should be planted. It is fortunate for the onion growers in Texas that the true Bermuda Crystal White Wax and the White (Yellow) Bermuda are decidedly more resistant to pink root than any other group or class of onion is. ‘Practically all of the “multiplier” varieties of onions, as well as shallots, are all highly susceptible. ‘Of the varieties of garlic, it appears that several strains of ‘the Mexican and Italian are more susceptible to pink root than the large growing varieties known as the Chinese. Hence on a pink root-infected soil the latter should be preferred. Of the Mexican and Italian varieties, the pink type of garlic seems to be more sus- ceptible than the white. The Mexican or Italian Whites are not so resistant the large Chinese white types previously mentioned. Like the onion, the pink root of garlic is carried with the bulbs that are used for seed, and for planting purposes. Hence all the methods of PINK Roor DISEASE OF ONIONS AND ITs CoNTRoL IN TEXAS. 7 _ controlling pink root of garlic are practically the same as those which apply to onions. Table 2.—Range of Liliaceous Hosts Susceptible to Pink Root.* Date of Date and PerCent Host Used. Planting. Pink Root. Healthy dry Egyptian onion sets . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, 71 per cent 15 Denia, healthy green sets . . . . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, 72 per cent 15 healthy shallots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, 48 per cent 15 healthy garlic bulbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, 78 per cent 15 healthy onion sets, ‘ multipliers” . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, 70 per cent 15 healthy bulbs, Narcissus Beauty . . . ._ . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Narcissus, Glory of Leiden . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Narcissus, Double Camperncll . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Narcissus, Queen of Holland . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Narcissus, Victoria . . . . . . . . . . . . . . . . . Mar. 10, 1917 July .28, no pink root 15 healthy bulbs, Narcissus, Empress . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Narcissus, Emperor . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Tulip, Mon Tresor . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Tulip, Dream . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Tulip, Faust . . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 2S, no pink root l5 healthy bulbs, Tulip, Psyche . . . . . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy rhizomes, Funkia Subcordata . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy rhizomes, Funkia Undulata Variagata . . . . . . Mar. 10, 1917 July 28. no pink root 15 healthy rhizomes, German lris, mixed . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Fresia, var. Purity . . . . . . . . . . .* . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Lillium Trifolium . . . . . . . . . . . . . . . . . . Mar. 10, 1917 July 28, no pink root 15 healthy bulbs, Calla Lily . . . . . . . . . . . . . . . . . . . . . . . . . Mar. 10. 1917 July 28, no pink root *Greenhouseltests injpink root-infected soil. SYMPTOLIS OF THE DISEASE The symptoms of pink root disease of onions are very striking. The trouble is confined only to the growing roots, bulb plate and crown, but not to the onion or garlic bulb itself. Affected root crowns frequently have yellowish roots. These may later turn pink or they may remain yellow indefinitely. The yellow, however, does not seem to be a stage of the pink root disease, but merely indicates an unhealthy condition. Yellow root invariably opens the way to later infections of the" pink root disease. ‘ The name pink root best describes the symptoms of the malady. Affected roots are dry, dead, and possess a distinct pink color which fades slightly as the roots are exposed to thesun. The disease may appear at an early stage in the seed bed. It is found in the field dur- ing all the stages of the development of the plant, but it checks growth more severely as. the plants begin bulbing or the bulbs approach ma— turity. In light stages of infection, only a few roots may show the pink color, whereas in advanced stages, every root of the bulb mav be affected. In severe cases, the roots become pink as fast as new ones are formed. Such plants, at the end of the season, have spent all their energy in producing new roots. Thus they become permanently stunted, and fail to produce a marketable sized bulb (Fig. 1, a a.nd b). In this case, a projecting nipple is formed at the bottom plate of the bulb (Fig. 1, c to f), the nipple merely indicating the area in which the old roots were produced and died, and the outer demarcation where new roots were continually being formed. In the seed bed, the disease is seldom severe enough to stunt the green sets. Hence, outwardly, there is little to indicate the presence of 8 TEXAS AGRICULTURAL EXPERIMENT STATION. Figure 1. . (a) Extreme case of onion plant infected with pink root. This plant is of the same age as the onion shown in (b). (b) Healthy,_ mature onion bulb for comparison. _ _ (c) “Multiplier” onion affected by pink root, showing the typical nipple format1on._ (d) and (e) Two young green onion sets badly infected with pink root and showing the nipple formation. _ _ b lThe same plants as (d) and (e) cut longitudinally to show the nipple and the diseased u p ate. (g) Onion sets, the roots ofiwhich are affected by root knot. PINK Roor DISEASE OF ONIoNs AND 11's CONTROL IN TEXAS. 9 pink root until the green sets are pulled and the roots examined. Dis- eased plants are quickly and easily recognized, and hence the extra expense in culling out and discarding them Will be money Well invested. _ In the main field, too, there are few outward symptoms to indicate the presence of pink root. In severe infections, however, the plants are stunted and seem to make little or no headwav. It is during harvest- ing that the serious result 1s noticed. Diseased bulbs are Slightly to severely undersized. The roots are either few or all pink and dry with the characteristic nipple present. After the bulbs have been exposed to the sun for drying, the pink color on the diseased roots, although slightly faded, contrasts strongly with the white of the healthy ones. Frequently, and due largely to favorable cultural conditions, the growth of the onion plant in a pink-root infected soil is faster than the disease can destroy the roots. In that case, the bulb matures, producing an average fair sized onion, with only a portion of its roots showing the disease. It is cases like these which tend to mislead the grower into believing that pink root is not a serious disease in reducing materially the final yields. CAUSE OF THE DISEASE For a long time, onion growers in Texas have maintained that pink root was not a disease; but that it was brought about through alkali in the soil, through the attack of thrips, or through working into the soil of a green cover crop, particularly black-eyed peas. In order to de- termine definitely whether or not the attack of thrips will bring about pink root, virgin land was secured in Laredo. This was planted first into an onion seed bed.. Later some of the healthy green sets were transplanted on this virgin soil for the main crop. Neither the seed- lings nor the transplanted sets were sprayed with any insecticide, s( that in both cases a severe attack of thrips took place. At the end oi the season and at digging time, it was found that the yield was reduced to a minimum, but that there was not a single matured bulb which was affected with pink root. This test and many similar observations conclusively show that thrips by themselves do not cause pink root. Thrips, however, are sometimes a irery important factor in favoring the development of the disease i.n the sense that the plants are badly weak- ened and root growth decidedly retarded. Such a condition is most favorable for the attack of pink root. It believed by some growers that pink root of onions is induced by alkali in the land. Careful chemical analyses were made by Dr. G. S. Fraps of the Chemistry Division of the Texas Agricultural Ex- periment Station. These results are shown in Table 3, which gives alkali analysis of pink root-infected soils. From Table 3 by Dr. Fraps, it is evident that all of these samples of soil contain some alkali. The alkali content is higher where pink root is present, excepting with sample No. 1155?’. Surface soil 11528 and 115-10 are both high in alkali, and this alkali consists largely of nitrate. Alkali was found near the surface in some of the soils suffering from pink root, such as soils 11532 and 11542, as well as 11588. Soil 11557 did not have much alkali, but this soil received an unbalanced fertilizer consisting of 1000 pounds acid phosphate and 200 pounds of nitrate of soda. It 10 TEXAS AGRICULTURAL EXPERIMENT STATION. is possible that this unbalanced fertilizer contributed to the tendency of the plants to have the disease. From these analyses, as will be shown later, alkali may be developed in the onion districts, but its association with pink root is only inci- dental. To keep down alkali, the land must be provided with ample drainage, and then the water should be used in such quantities as to wash it otit of the soil. Mlanure, or a rotation of crops which will add vegetable matter, should be used on heavy soils such as Laredo silty loam or Laredo clay loam. This will make the soil more porous and allow the surplus water to penetrate deeper. into the subsoil. For alkali soils which are infected with the pink root disease, and in which the alkali is due mostly to nitrates, it is best not to use nitrate of soda as a top dressing, but to use some other form of nitrogen, preferably sul- phate of ammonia. Table 3.—Alkali in parts per million of soil. . _ _ Kind of Alkali. Sample Kind of Soil. _ Total No. Nitrates Sulphates Chlorides Alkali. 11528 Webb fine sandy loam, surface soil, much pink t roo . . . . . . . . . . . ._ . . . . . . . . . . . . . . . . . . . . . . . 1050 237 114 1401 11529 Subsoil 11528. 6 to 12 inches . . . . . . . . . . . . . . . . . . 750 258 125 1133 11530 Subsoil 11528, 12 to 24 inches . . . . . . . . . . . . . . . . . 1050 95 166 1311 11531 Subsoil 11528, 24 to 36 inches . . . . . . . . . . . . . . . . . 300 208 197 705 11532 Alkali scrapings . . . . . . . . . . . . . . . ._. . . . . . . . . . . . . 5650 1465 2501 9616 11533 Webbfine sand, near road, some pink root . . . . . . 120 286 284 690 11534 Subsoil 11533, 6 to 12 inches . . . . . . . . . . . . . . . . . . 90 204 148 442 11535 Subsoil 11533, 12 to 24 inches . . . . . . . . . . . . . . . . . 0 201 99 300 11536 Webb fine sandy loam,_ no pink root . . . . . . . . . . . 30 300 191 521 11537 Subsoil 11536, 6 to 12 in_ches.. ._ . . . . . . . . . . . . . . . 30 296 172 498 11538 Webb_fine sand, good soil, no pink root. . . . . . . . 30 216 147 393 11539 Subsoil to 11538, 6 to 12 inches . . . . . . . . . . . . . . . 8 200 218 226 11540 Laredo silty loam, much pink root . . . . . . . . . . . . . 4200 0 472 4672 11541 Subsoil to 11540, 6 to 12 inches . . . . . . . . . . . . . . . 1500 54 417 1971 11542 Alkali scrapings . . . . . . . . ._ . . . . . . . . . . . . . . . . . . . . 450 570 345 1365 11543 Laredo clay loam, some pink root . . . . . . . . . . . . . 3 438 429 860 11544 Subsoil to 11543, 6 to _12 inches . . . . . . . . . . . . . . . i, 302 261 563 0 11545 Laredo silt loam, no pink root . . . . . . . . . . . . . . . . . 5 11546 Subsoil to 11545, 6 to 12 inches. . . . .' . . . . . . . . . . 5 11547 Laredo silt loam, no pink root . . . . . . . . . . . . . . . . . 3 11548 Subsoil 11547, 6 to 12 inches . . . . . . . . . . . . . . . . . . 0 11549 Webb fine sandy loam, no_ pink root . . . . . . . . . . . 3 213 180 396 11550 Subsoil to 11549, 6 to 12 inches . . . . . . . . . . . . . . . O 11557 Laredo silt loam, much pink root . . . . . . . . . . . . . . 0 11558 Subsoil to 11557 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O 11559 Webb fine sandy loam, much pink root. . . . . . . . . 8 11560 Subsoil to 11559, 6 to 12 inches . . . . . . . . . . . . . . . 1 217 256 483 11588 Soil near peeler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9950 9950 11589 Subsoil to 11588 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3298 3298 It is probable that the alkali increases the liability of the onion to disease by decreasing its resistance. Other adverse influences could have a similar effect. In order to determine definitely whether traces of alkali in the soil will induce pink root of onions, infected soil was secured at Laredo from nearly the- same spots where the samples for the chemical analyses were taken and which were referred to in Table 3. This soil was distributed in five-inch pots and disinfected with for- maldehyde at the rate of one pint in twenty gallons of water. Three pots were untreated and left as a check. Ten davs after treatment, the pots were sown to onion seeds, which sprouted normally. The seedlings were then allowed to remain in these pots for nearly ten weeks, and they were thinned as they grew larger. Ultimately, as the plants were PINK Roorr DISEASE or ONIoNs AND ITs CONTROL IN TEXAS. 11 pulled out for final examination, all in the check pots showed a high _ percentage of pink root, whereas those i11 the soil treated with for- maldehyde were all healthy. This proved conclusively that, although these soils show traces of alkali as indicated in. Table 3, this alkali is apparently not suificiently strong to injure plant growth, and it does not develop pink root where the soil is sterilized with formaldehyde. But in the check pots where the soil was not sterilized, pink root was present on many of the seedlings. This proved definitelv that the trace of alkali in the soils of Table 3 was not responsible for pink root, but that the latter was induced by a definite parasite in that soil. Further- more, alkali in the soil is not a constant factor. It varies, rising and falling with the increase or decrease of water in the soil; whereas pink root is on the increase where onions are grown too long on the same land. To determine definitely the cause of pink root, the following experi- ments were carried. out: Artificial Inoculat/ion. In order to obtain the causal organism of pink root, over 1000 plate cultures were made from onion roots which showed typical pink root disease. Over twenty-five various fungi were isolated, among which were two species of Fusaria. (Fig. 2, d to g). Each of the organisms was tested out as to its pathogenicity. The method employed was as follows: Typical onion soil was secured from Laredo and steam sterilized at fifteen pounds pressure, for three hours at two-day intervals. When the soil in the pots cooled down, pure cul- tures of each organism were introduced in each of a set of two pots which were planted with healthy onion sets. These plants were allowed to grow for two months. After that time, the plants were taken out and examined for pink root. Of all the organisms tested, only one species of Fusarium, which is here referred to as Fusarium No. 1, was capable of reproducing pink root. The general results of the inocula- tions with this Fusarium. is shown in Table 4. From this table it is seen that Fusarium No. 1 was able to induce pink root infection, al- though the percentage was small compared to the infections ob-tained when healthy plants were planted in pink root soil. There seems no doubt but that Fusarium No. 1, tentatively named F. malli, is one of the organisms which is the cause of pink root. In nature, however, it seems probable that other organisms, especially species of Fusaria in combination with F. malli help to increase its virulence. This is per- haps why small percentages of infection are secured withF. malli in artificial inoculations and high percentages of infection are secured by merely planting healthy sets in a pink root-infected soil. The role of the possible association of other organisms with F. mall/i in increasing i.ts virulency is now being further studied and will be reported at a later date. At the present time it is sufficient to state definitely that the cause of pink root of onions, shallots and garlic is a fungus, Fusarium malli, and that possibly other fungi, especially Fusarium No. 2, may be associated with it to increase its virulency. 12 TEXAS AGRICULTURAL EXPERIMENT STATION. .5555 055 50 005000 055 55 05.05 0550 055 55 5 .075 555500555 50 5555.00.55 50 0555 055550055 55 5.0505050... 50550550055 50500550200520 .5005 5555 5553 500500.555 5505053055 050.3 5055055 50005 0 50 50055000 05555 055 050050 0555 50.5.5 5055 550505.30 05 55+ .050.505 5.0350050 5005 005 505/0: 5005 5555 05053 5050 =00 55.503 050055 0 50 3050 050550 50555505 0.55 05053 00050.5. 05550.5. .5 .075 5055050555 50.5.5 50055000 0503 0500 0005.512. . 050.5055 5050-035 50 05505 00555 50.5 05500055 0505505 m5 50 5000555050 50050 003 5500 05.5.0. .3555005 50505505505 .5005 0M5I5Q5050M< 555 5.0050005. 0555505 N .05 . 5< .5055 052550504 .55 5005505 50505505505 $555005 m .05 525w $555005 =0 50.5 55555. .5500 505 50m d5 55555. $555005 =0 d5 550w .5500 505 m5 .N .5555. .5555005 :0 d5 .0000 .5500 505 0505 .5 550m .5500 505 005 6N .035 .5500 505 m zm .03.. .5500 .505 5.5 .05 .054 . . . . . . . . . . . . . . . . 153.3055 0555. . . . . . . . . . . . . . . . . . . . . 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(a) Green onion_ sets treated for various lengths of time in formaldehyde solution. (b) Tanks for dipping onion sets against thrips. _ _ (c) Crush culture_from onion roots infected with pink root, showing Fusarium growth and a few bacterial colonies. , d) Fusarium No. 2 on potato plug. _ (e) Fusarium malli on potato plug for comparison and showing the thick mass of plonnotes. (f) Plate culture of Fusarium malli on hard bean agar. o (g) Plate culture of Fusarium No. 2 on hard bean agar. 14 TEXAS AGRICULTURAL EXPERIMENT STATION. CARRIERS AND CONDITIONS WHICH FAVOR PINK ROOT Careful studies both in the field and in the laboratory have shown that the spread of pink root and the amount of loss from this disease depend on many factors, chief of which are as follows: The Soil. It is a well known fact that the largest onions and the heaviest yields are produced on lands which are rich in humus and plant food, and which have not as yet been exhausted through a sys- tem of one-crop farming. Likewise, the greatest damage from pink root is actually met with on lands known to be deficient in plant food, chief of which may be mentioned nitrogen and humus, especially where onions were grown on the same land for a period of years. In order to determine Whether or not the soil is a possible carrier of pink root, experiments ivere planned as indicated in Table 5. From this table there seems no doubt whatsoever that the soil is a carrier of this disease. This means that if a soil. once becomes infected with pink root, and if onions or garlic are grown successively for a period of years, the disease will become so serious as to threaten the profitable culture of these two crops. This condition has actually happened in many onion sections in Texas, and many growers are now confronted with the sad experience of dealing with badly infected land. The Sets. In Webb County, and in Texas in general, dry sets are not planted to produce the main crop for market. It is found by most growers that the use of dry sets results in producing too many “splits” or “doubles” which the market does not want. Hence onion seeds are planted in seed beds and the resulting green sets transplanted in the field. That the soil is a carrier of pink root has already been shown on page 15. In this connection, it was not very difficult to show that seed beds, when made on infected land, produced pink-root diseased sets; and that these in turn carried the malady to. new land. Fre- quently, because of poor germination, or of unfavorable weather con- ditions, or of a severe attack of thrips, the seed beds are ruined, and the grower is compelled to buy his green sets elsewhere and from un- known sources. In this way, pink root may be introduced into one’s land without his even suspecting it. In order to determine definitely whether or not green or dry sets are possible carriers of pink root, experiments were carried out as indi- cated in Table 6. From this table it is conclusive that when green sets are grown on soil known to be infected with pink root, they will actually become infected and carry the disease from place to place. This in reality is a condition which is prevalent; namely, the onion seeds are frequently planted on pink-root infected soil. Later the infected green sets are transplanted to the field, and the disease is introduced. In this way pink root is spread broadcast without the grower’s suspecting it. Furthermore, when such sets are planted in the fields, they are handi- capped in the sense that they have to struggle hard to overcome the effect of the pink root. T_his isonly possible when soil and climatic conditions are favorable. Sudden freezes, or a sudden drouth due to an unavoidable breakdown of the irrigation plant, will invariably result in further weakening of the plants and eventually in poor yields or total failure. Any shock which will set back the diseased onion plant will only increase pink 15 PINK Roots DISEASE OF ONIONS AND Itrs CONTROL IN TEXAS. .0000: .:0::0:w 5:300: ::0 d: 0.0003: 0:0: 5m :23. 000:0 :: 080:0 0:00 000:0 >:.::_‘00: mm 000:0“: .::00 0:00:00 00:00:: :00N::::0:0:D . . . . . 4 . . . . . . . . . . . . . . . 0:02 5:300: :0 d: 0.0003: 0:0: .0 33. 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:00 030.0 16 TEXAS AGRICULTURAL EXPERIMENT STATION. 0030000 w03 wm 00.0 w0 w0000000 300w 0003000 000w 200F020 .0000 0000000 00003 000000000 0w0000 w0000000 00000 w00w 0000300090. .w0000 300003 00000 0000000 000 .mN 300000000. .0000 300000» 00000 0.000000 000.. .mN 0000000000. .0000 30000.00 00000 0000000 000 6N 300000000. .0000 0.000000 @000 30000..» 00< $000000: 00¢. .0000 30000.» 000000.00 000 N02 .mN >0000000w .0000 0000000 00000 3000000 0000000000 000 K0000 .00 0000000000. .0000 0000000 0000 30000.» 000000.000. 000 .2000 .00 300000000. .0000 0000000 00000 3000000 3000w 004 .0000 0000000 w000000 000 .0000 0.000000 00000 300000» 00000 0000 0» .0000 0.000000 00000 0000 om .0000 0000000 00< .0000 0.000000 .00 0w00 00000 >003 004 .0000 0.000000 .00 00000 0 002 .0000 00.00000 004 .0000 0.000000 000 N200 .NN 300000000. 0035000202 $000.0 0000000 . 000w 0000 0000000 00003 0000000000000 000w 000N000000w 000000w 000 0000000000 .000 0000 0000 w0000 .0002 6 000000000302 000w 0000 0000000 00003 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PINK Roor DISEASE OF ONIONS AND ITs CONTROL IN TEXAS. 1'7 root. The only appreciable way of assisting infected sets to overcome "the disease is to encourage rapid growth so that new roots may ‘be developed faster than they are destroyed by the disease. For practical purposes, therefore, it is essential always to begin with a healthy soil and healthy sets. When one pulls sets for transplanting he should carefully inspect them, and discard those which show pink root, even though. this process of selection would mean a loss of diseased sets and extra labor. Under normal labor conditions, culling would cost about from $6 to $10 per acre. 1n buying green sets, one should secure them from localities known to be free from pink root, or he should see that the sets are accompanied with a certificate as to freedom from disease. Poor Leveling. Repeated field observations have shown that wher- ever infected soil. in the seed bed, or in the beds of the main crop, is not properly leveled, a condition which prevents the even distribution of water, pink root is very prevalent. Improper leveling results in numerous high spots where water cannot reach. Pink root is actually more prevalent and more severe in these higher spots. Sets growing in these dry higher spots are naturally weakened and hence become a ready prey to pink root. Irrigation. It is very essential from the point_ of view of preventing pink root to encourage rapid and vigorous growth of the plant, once it has been set out in the field. A. vigorous young onion set, when trans- planted in the field, will develop new roots within three days after the transplanting, provided, however, that the soil contains sufficient mois1 ture and nourishment. Hence it is important that irrigation should be given immediately after the transplanting. It is not desired to con- vey the idea that there is danger of losing plants from slight delay in following with irrigation after the setting out of the young onions, but that an appreciable delay i.n irrigation immediately after the trans-p planting will delay the formation of new roots, and this is favorable to a severe infection of pink root. Vl/eather Uonrditions. It is a known fact that weather conditions have , a direct influence on the spread or the limitation of pink root. While it is desirable to plant seed beds early, this should not be done too " early in the season. On the other hand, too late sowing is undesirable because the crop will have to make most of the growth for bulbing (luring the hot weather. A. check in growth of the crop brought about by freezing, or delaying bulbing and maturity into the season of ex- treme hot weather, is equally’ favorable to pink root. An attempt is, frequently made to grow green onions during the entire year to supply the table demands of the local market. Observations have shown that when this is done under Webb County conditions, which practically means groxving onions during the hot summer months, these onions suffer very severely from pink root, much more so than when they are grown in the same soil early in the season. Furthermore, the land itself becomes badly infected and unfit for another crop of onions. From a practical consideration, therefore, only one crop of onions should be grown on the same land during the year. -- If possible, the crop should he matured and harvested before the hot weather strikes it. E67. Worm. ‘ Tt is believed by many, that eel worm causes pink root. This is not the case because, as was alreadylshown in Table 4:, pink root is caused by a definite parasitic Fusarium. Eel worm is a para-' 18 TEXAS AGRICULTURAL EXPERIMENT STATION. p site ‘infesting the roots which is distinct and should not be mistaken for pink root. Eel worm infestations are characterized by swellings on the growing roots (Fig. 1, g). These swellings are induced by the presence of minute Worms (H eterodcra. raidicicola) Within the tissue of the attacked roots. While it is certain that the eel Worm does not cause pink root, it frequently opens the way for pink root infection ( 1) by weakening the plants, (2) by wounding the roots and by thus opening the Way for infection. Growers should, therefore, make doubly l certain not to plant onions in a soil known to be infested With both pink root and eel Worm. To disregard this would mean extremely poor yields or certain failure. Furthermore, the treatment to sterilize soil infested With eel worm is too expensive on a large scale to justify the cost. Such land should be devoted to the culture of the true type of Hairy Peruvian alfalfa, which has proved so valuable in Webb County. It is claimed that cyanamid Will rid a soil of eel Worm and also act as a ifertilizer, because of the nitrogen Which it contains. A quantity of cyanamid Was sent to the Writers With the request to try out its effect on nematode control. Some of this Was applied outdoors to an onion field infested With nematode and pink root. The field treatment with cyanamid amounted to 300 pounds per acre, given at two intervals. The first 150 pounds were applied November 22, and the second amount, January 19. The field effect of the cyanamid is shown in Table 7. From this table it is evident that cyanamid at the rate of 300 pounds per acre actually increased the total yield of marketable onions per acre. However, in the carefully checking up its effect on nematode, it was plainly evident that it did not control this pest. Its beneficial effect in increasing the general yield was probably due to the available nitrogen which it contains; hence in this respect it deserves consideration. Further outdoor trials with cyanamid in the seed beds, using it at the rate of 250 pounds, 500, 1000 and 2000 pounds per acre, showed no ill effect on germination, or on the general groyvth of green sets. It also _ failed to reduce or control either nematode or pink root. It has been stated. that field applications of cyanamid at the rate of 2000 pounds ton) per acre exerted no ill effect on germination, or on the gneral growth of the onion plants in the field. It was, therefore, thought desirable to try stronger applications of cyanamid with the hope of controlling nematode and perhaps pink root. Accordingly, experiments were carried out, in the greenhouse, on onion plants and on coWpeas (blacfk-eyred variety), both growing in badly infested soil. The amount of cyanamid is indicated in Tables 7 and 8, which varied from 3%‘ tons to 402% tons per acre. The results of these amounts on onions is shown in Table '7. From this table it is seen that cyanamid, when applied at the rate of 331.7, *7, 10%, 1%, and 17% tons per acre, re- tarded the growth of the plants, and neither the pink root nor the nematode was kept in check. Furthermore, applications varying from 35 tons to el0‘2% tons per acre actually killed outright the green onion sets. From this experiment, it is evident that cyanamid up to one ton may be safely applied in field conditions where it would probably exert a stinuilating effect on the general growth and on yield, but it will not control nematode. Applications stronger than one ton per acre Will result in severe injury to the crop. The effect of strong applica- tions of cyanamid on the black-eyed peas is well shown in Table 8. PINK Roor DISEASE or ONIONS AND ITs CONTROL IN TEXAS. 19 From this table it is seen that with an application of 3% tons, growth is gradually checked, and this checking of growth varies directly as the number of tons per acre were increased from 3%; t0 In the further increasing of the amount from 7-} t0 410.2% tons per acre, the growth was practically inhibited. As to the effect of cyanamid on nematode control in the black-eyed pea, it was found that an application vary- ing from 3.1, to 11> tons per acre had no effect whatsoever in reducing the amount of. root knot. Ifowever, when applied at the rate of 17% tons up to 140 tons, the nematode was actually reduced, and its activity was only confined. to the few surface rootlets. Furthermore, with an application at the rate of 1'75 tons to 4,02% tons per acre, the root sys- Table 7.—Effect of cyanamid on control of pink root and nematode.* Amount Amount ' Cyanamid Cyanamid Date of Planting and Number Used in Tons and Kind of Host Used. Results and Date. Per Pot. Per Acre. _ 1 gram 3.5 Feb. 11, 1918, 35 pink root and March 20, 1918, 100% nematode nematode affected green sets. and pink root. Door growth. 2 grams 7 Feb. 11. 1918. 35 pink root and March 20. 1918, 100% nematode nematode affected green sets. and pink root, poor growth. 3 grams 10.5 Feb. 11, 1918. 35 pink -root and March 20, 1918, 100% nematode nematode affected green sets and pink root, poor growth. 4 grams 14 Feb. 11. 1918. 35 pink root and March 20, 1918, 100% nematode nematode affected green sets. and pink root, poor growth. 5 grams 17 5 ' Feb. 11, 1918, 35 pink root and March 20, 1918, 100% nematode nematode affected green sets. and pink root, poor growth. 10 grams 35 Feb. 11, 1918, 35 pink root and Plants all dead. ' nematode affected green sets. 20 grams 70 Feb. 11, 1918. 35 pink root and Plants all dead. nematode affected green sets. 30 grams 105 Feb. 11, 1918. 35 pink root and Plants all dead. nematode affected green sete. 40 grams 140 Feb. 11, 1918, 35 pink root and Plants all dead. nematode affected green sets. 5O grams 175 Feb. 11, 1918. 35 pink root ‘and Plants all dead. nematode affected green sets. 60 grams 210 Feb. 11. 1918. 35 pink root and Plants all dead. nematode affected green sets. '70 grams 245 Feb 11. 1918. 35 pink root and Plants all dead. . nematode affected green sets. 80 grams 280 Feb. 11; 1918, 35 pink root and Plants all dead. nematode affected green sets. 90 gramS 315 Feb. 11. 1918. 35 pink root and Plants all dead. nematode affected green sets. 100 grams 350 Feb. 11. 1918. 35 pink root and Plants all dead. nematode affected green sets. 115 grams 402.5 Feb. 11. 1918. 35 pink root and Plants all dead. nematode affected green sets. v Ch€Ck**- - ~ Check. . . . . 35 healthy green sets grown in green- house. Feb. 11. 1918. *Soi_l used i_n this experiment was from a pink root and nematode infected field from Laredo, in duplicate 5 inch pots. _ _ **Soil used was steam sterilized. tem was practically burned, and. in no case could there be found a single root knot sxvelling; indicating apparently that, at the rate of these enormous applications, the nematode was actually controlled, but growth as well as root system was nearly destroyed. In general, therefore, it may be safely stated that cyanamid is not able to control root knot as far as the tender herbaceous crops are concerned, but its use as a fer- tilizer for onions (leserves further trials. Tit-rips. Like eel worm, thrips are not responsible for the direct cause of pink root. but merely weaken the plants and open up the way for this disease. When young sets are attacked by a large number of thrips, the vitality’ of these plants is decidedly undermined, and they 20 TEXAS AGRICULTURAL EXPERIMENT STATION. frequently die out or produce undersized and unmarketable onions, even though the crop grows i.11 an otherwise healthy soil. If, in addition to thrip injury, the soil is also infected with the organism of pink root, the result is usually disastrous, since in this case the infected plants “have neither root- to afford support nor top growth to supply vigor. It may therefore be said With certainty that when thrip infestation occurs on onions grown on a healthy soil, the effect is bad enough, although there is a possible chance for a fair yield. An attack of thrips, however, becomes disastrous on plants grown in pink root in- fected soil. 1n this case, then, it is practically useless to attempt to produce a marketable onion after it has been badly attacked by thrips, and spraying or dusting would be wasting time and money. ' In prac- tice it has been repeatedly demonstrated that, if the soil is free from pink root, if it is well supplied with rapidly acting fertilizer, and if at at the same time the plants are thoroughly sprayed or dusted to hold down thrips, other things being equal, the chances are for a good normal yield. On the other hand, when the plants are grown on a pink root infected soil which is deficient in proper fertilizer elements, no amount of treatmentjo destroy thrips will help the infested plants to regain their vigor and produce a normal yield. i That thrips do reduce the yield of onions grown on pink root soil is better shown in Table 11. The plants in Table 11 were grown on a badly infected pink root soil which was variously treated with fer- tilizers. The plants on this soil, however, were badly attacked by thrips before any spraying or dusting could be carried out, and the result as far as the yield was concerned was practically negligible. When the onion grower is compelled to grow his onion crop on pink root-infected soil, every precaution should be taken not to allow the thrips to get the upper hand. I-Iere spraying or dusting should be carried out arly and repeatedly as the thrips appear. In practice, to control thrips the plants are sprayed with Black Leaf 40. This solu- tion is prepared as follows: Three to fiVG pounds of good laundry soap are dissolved in boiling water. This is then slowly mixed in a barrel of cold wivater, making a total of forty gallons. To this soap solution is added 11- pint of Black Leaf 40, also known as Nicotine Sulphate. For securing best results, high-power spraying machines are required, and these should be equipped with Vermorel nozzles. The onion plants should be thoroughly sprayed from side and top, entering into the crotch so as to reach every thrip, young or adult which may be crawl- ing around any portion of the exposed. parts of the host. This spray- ing should be repeated every three or four days after the thrips appear so as to control completely the pest. Frequently i.t is desirable to dip the sets in Black Leaf 40 solution, iust as they are pulled from the seed beds and before they are planted in the field. In that case the same solution of Black Leaf 40 is used as mentioned above. To treat plants for about thirty acres by dipping, one ten-pound can of Black Leaf 4O to every 50 or 60 pounds of ordinary yellow soap dissolved in water will suffice. The soap is dissolved in galvanized tin tanks (Fig. 2, b) and poured into 1000 gallons of water, to which is then added the ten pounds of Nicotine Sulphate. The green sets are soaked for one hour and are then ready for immediate planting. - / 21 PINK Roocr DISEASE OF ‘ONIONS AND ITs CONTROL IN TEXAS. 8882222828 2228828 883 2.88: 22o..w** .8222 228222 m 82882282222. 222 62.8282 222822 22o8 2.8288222 8252822222 2.228 2oo2 2222222 22202.2 883 22282222282288 82222 222 2.8822 22om* .. 88.2208 UOuOQuflm QUOQQEQG GO 28222282282222 a0 wOQMwm|.w 82228.2. .U@QFNEQHM QOQG@H~H#Q< . . . . . . . . . . . . . . . . .WU£UHM@ Aw . . . . . . . .QHBQ.M@ @OQW 2.2.22 w . .w@O®m NQQ @O%QIV2UN@Q 8@@ KANE . . . . . . .V%QD§U - . . . .** U950 . . . . . . . . . 2282838 2882 872 . . . . . . . . . 28228222222288 872 282.888 8822 2.828-828.8222 mm £2222 dm .282 9N2? 822282 m22 . . . . . . . . . .222o28228 2oo.2 072 . . . . . . . . . .22o2282222222ow o72 382.888 8822 288282288222 mm 2228.2 6m .282 22mm 8828.28 002 . . . . . . . . . 222828228 2oo2 o72 . . . . . . . . . .22o2282222222ow oZ . .82.o88 822 282282288222 mm @2222 dm .282 m2m 8222828 om . . . . . . . . . 2228288 2oo.2 oZ . . . . . . . . . . .22o2282222222ow o72 . .82.8o8 822 2882282288222 mm .w2m2 6m .282 owm 82228.8. ow 82528222822 oZ . . . . . . . . . .222o28228 2oo2 072 . . . . . . . . . 88228222222288 oZ 282.888 8822 882282288282 mm .2282 dm .282 mwm 8222828 o“. .82.o28222o22 872 2.2222222 322.822 222828.28 288M . . . 28228222222288 28822 2 ..82...888 822 88228-288222 mm £2222 6m .82 02m 882828 02.2 882822222228 88828222822 oZ .8828? 2882 o22 8222882288282 82.888 o32 3222c r222 $2 . .82.8o8 8822 2282282288222 mm £2222 6m .282 m: 82228.28. om .2oo2 2o 88822228 28822 282822888 22:2 8222.2 82288 82528222872 . . . . . . . . . . . . . 188228222 8km . . . . . . . .2223o2w .2822 r222 m 182.888 822 282282288222 mm £2222 dm .282 0222 8222828 ow .2882 2o 88822228 28822 282822888 2:22 8222.2 8228m 82828222872 . . . . . . . . . . . . . . . . 88228222 8 . . . . . .2223o2m 20822 r222 2m . .82.o88 8822 2.828-822.8222 mm $2222 dm .282 n02 8.22828 om .2002 2o 88822228 .2822 2.8282888 22222 82222 82288 8232822282 . . . . . . . . . . . . . . . . 822222 m. . . . . . . . .5228 28822 r222 N . 82.888 8on2 882228288222 mm £2222 6m .282 o2. 8282M on .2802 2o 88822228 .2822 282822888 22222 222.2 82288 828828222872 . . . . . . . . . . . . . . . . .88228222 o . . . . . .2223o2m .2822 . 222 2m . .82.8o8 8822 282282288222 mm @2222 .022 .282 mm 82228.28. o2 .2oo2 2o 88822228 .8822 . 282822888 22222 222.2 8228...... 82.828282 . . . . . . . . . . . . . . . . 8228222 .21 . . . . . . . . . .2o2o8 28822 r222 m . 82.888 822 282288288282 mm £2222 6m .282 m $2 82228228 m .82.o28222o22 22223 2.828258 228 828882 . . . . . . . . . . . . . . . . 8228222 w . 28288 28822 22228.2 r222 8km . .82.888 8822 282282288222 mm .2222 dm .282 2 8.22828 2» 828828222822 22223 2.8282888 228 828982 . . . . . . . . . . . . . . . . 8228222 w . . . . . . . . .2223o.2w 2282 r222 w . 828888 822 28822812288222 mm .w2m2 dm .282 m .02 82228.22... m 82.822822 2222.3 2.8282388 228 828982 . . . . . . . . . . . . . . . 18228222 w . . . . . . . . 2223828 228.2 r222 h 282.888 8822 282282288222 mm. 222222 dm .282 N. 82228.8 N 82528222822 22223 2.828258 222. 8288282 . . . . . . . . . . . . . . . . 8228222 w . . . . . . 422388 .2282 r222 82> . .82.8o8 8822 2.828-222.8222 mm £2222 dm .282 m .28. 282m 2 . 8288.82 2o 22282282 .88222> 2o 22282282 . 8228.2. 222 .2022 2on2 .222288w2 2.8822 288E 2.2232 8284 2on2 222228228220 2223826 2o 2882.312 2.228 28222222272 82222228222 2o 828D 22222828220 222222224 222222224 _ 22 TEXAS AGRICULTURAL EXPERIMENT STATION. Instead of spraying for thrips with Black Leaf 4L0, they may be con- trolled by dusting with what is known as 3-in-1 Contact Insecticide and Fungicide. This is called 3-in-1 because its action is claimed to be threefold: 1)' as a repellant; ('2) as a contact insecticide; and (3) as a fungicide on account of its sulphur. For purposes of best results with this product, a good powder gun of the latest design is required for dusting, the operation being repeated at intervals of from three to five days, depending upon the severity of the attack. ' Where the soil is known t0 be infected with pink root, and‘ When the grower has reason to fear an attack from thrips, it would be ad- visable to plant the crop reasonably early and make every effort to in- duce early maturity. Likewise, spraying should begin early, and one should avoid any possible delav with repeated. treatments, the lack of which may result in a rapid spread of the thrips. TIME OF APPEARANCE OF PINK ROOT Ordinarily, under seed-bed conditions, no pink root becomes appar- e11t soon after the seed sprout. In fact, very little pink root is notice- able after the first few waterings and under thirty days. However, the disease increases after thirty to forty days, and with the later water- ings it becomes very abundant at the age of seventy days. With the main crop, pink root becomes very bad in the field as the season ad- vances, and especially when the soil temperature rises. The severity of the disease in the field. will also depend on any serious check to the growth of the crop. EFFECT OE SOIL TEMPERATURE‘ ON THE PREVALENOE OF PINK ROOT Mention has already been made above that in the seed bed, pink root generally appears after thirty to forty days. Since the seeds are planted in the seed bed early in September, and at a time when the soil temperature is fairly high, the pink root disease finds favorable conditions for rapid spread. Furthermore, in closely watching the prevalence of pink root in the field, one is convinced that the disease is at its height at the time when the onion plants are about to begin bulbing. The disease reaches its maximum at about harvest time. In studying this effect and its correlation with soil temperatures as indi- cated in Tables 9 to 12-, one will notice that the higher soil temperatures occur during May, at which ‘time the pink root is at its height in an infected soil. PINK ROOT DISEASE OF ONIONS AND ITs CONTROL IN TEXAS. 23 Table 9.— Soil temperature readings for December, 1917. Outside. One Inch. Three Inches. I)ec, 1917. 7:00 2:00 5:00 7:00 2:00 5:00 7:00 2:00 5:00 A A4. P.L4. P.L4. A L4. P.h4. P.h4. AIDA. P.h4. P.h4. 1 . . . . . . . . . . . . . . . . . . . . .. 36 72 68 48 72 70 52 70 72 2 . . . . . . . . . . . . . . . . . . . . .. 48 84 80 49 84 80 54 76 74 3 . . . . . . . . . . . . . . . . . . . . .. 48 82 70 48 82 72 59 74 72 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 57 86 80 58 78 . . . . H 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 79 . . . . .. 62 74 . . . . H 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 70 . . . . .. 63 70 . . . . H 7 . . . . . . . . . . . . . . . . . . . . .. 50 76 . . . . .. 54 68 . . . . .. 54 68 . . . . H 8 . . . . . . . . . . . . . . . . . . . . .. 50 93 . . . . .. 54 85 . . . . .. 58 76 . . . . .. . . . . . . . . . . . . . . . . . . . . .. 57 82 76 59 80 79 64 72 76 10 . . . . . . . . . . . . . . . . . . . . .. 50 68 64 60 64 60 56 61 62 11 . . . . . . . . . . . . . . . . . . . . .. 59 74 65 58 68 66 58 68 66 12 . . . . . . . . . . . . . . . . _ . . . .. 50 69 64 56 68 66 59 57 56 13 . . . . . . . . . . . . . . . . . . . . .. 62 64 55 59 63 60 61 64 63 14 . . . . . . . . . . . . . . . . . . . . .. 46 70 65 52 62 59 54 63 60 15 . . . . . . . . . . . . . . . . . . . . .. 65 74 63 60 73 64 62 71 64 16 . . . . . . . . . . . . . . . . . . . . .. 63 65 65 63 62 62 63 62 63 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 65 70 63 67 70 18 . . . . . . 4 . . . . . . . . . . . . . .. 60 70 68 62 68 66 64 70 69 19 . . . . . . , . . . . . . . . . . . . . .. 60 74 70 63 73 70 66 71 68 20 . . . . . . . . . . . . . . . . . . . . .. 50 80 70 55 77 70 55 74 70 21 . . . . . . . . . . . . . . . . . . . . .. 70 85 74 68 81 75 67 72 76 22 . . . . . . . . . . . . . . . . . . . . .. 75 83 75 65 74 70 64 73 72 23 . . . . . . . . . . . . . . . . . . . . .. 68 87 79 65 82 78 68 78 77 24 . . . . . . . . . . . . . . . . . . . . .. 68 90 80 65 77 74 68 76 72 25 . . . . . . . . . . . . . . . . . . . . .. 60 64 66 63 67 65 67 68 67 2s . . . . . . . . . . . . . . . . . . . . . . 50 70 62 59 s9 69 s2 70 70 27 . . I . . . . . . . . . . . . . . . . . .. 51 77 64 55 80 66 61 72 66 28 . . . . . . . . . . . . . . . . . . . . .. 58 77 71 58 77 74 62 73 71 29 . . . . . . . . . . . . . . . . . . . . .. 46 60 57 52 58 58 56 58 58 30 . . . . . . . . . . . . . . . . . . . . .. 32 67 62 43 67 62 49 63 61 31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48 84 . . . . .. 52 77 . . . . H hdean ten1perature..... 65, 3/13 65, 9/31 65, 5/31 Table 10.——Soi1 temperature readings for January, 1918. Outside. One Inch. Three Inches. Jan, 1918. ———————— 7:00 2:00 5:00 7:00 2:00 5:00 7:00 2:00 5:00 A B4. P.h4. P.h4 A.h4. P.h4. P.h4. A L4. P.h4. P.h4. 1 . . . . . . . . . . . . . . . . . . . . .. 36 72 68 48 76 70 52 70 72 2 . . . . . . . . . . . . . . . . . . . . .. 39 83 80 48 84 80 55 76 74 3 . . . . . . . . . . . . . . . . . . . . .. 55 82 70 55 82 72 59 74 73 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54 86 . . . . .. 58 78 . . . . H 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 79 . . . . .. 62 74 . . . . .. 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 69 . . . . .. 63 70 . . . . .. 7 . . . . . . . . . . . . . . . . . . . . . . 50 76 . . . . . . . . . . . . . . . . . . . . . . . . 54 68 . . . . . . 8 . . . . . . . . . . . . . . . . . . . . .. 50 93% . . . . .. 54 841/2 . . . . .. 58 75 . . . . .. 9 . . . . . . . . . . . . . . . . . . . . .. 5614 82 74}é 5614 80}§ 79 64 72 76 1O . . . . . . . . . . . . . . . . . . . . .. 72% 96 . . . . . . 70 91 . . . . . . 73 84 . . . . . . 11 . . . . . . . . . . . . . . . . . . . . .. 1 90 . . . . .. 42 65 . . . . .. 47 64 . . . . .. 12 . . . . . . . . . . . . . . . . . . . . .. 29 46 41 46 55 53 54 57 58 13 . . . . . . . . . . . . . . . . . . . . .. 40 76 . _ . . .. 51 75}§ . . . . .. 52}é 70 . . . . .. 14 . . . . . . . . . . . . . . . . . . . . .. 45 62 . . . . .. 53 59 . . . . .. 55 60 ...n 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 47 72 . . . . .. 52 65 . . . . H 1% . . . . . . . . . . . . . . . . . . . . .. 42 73 . . . . .. 50 79 . . . . .. 54 72 . . . . .. 18 . . . . . . . . . . . . . . . . . . . . .. 51 91 . . . . .. 52 72}§ . . . . .. 56 72}§ . . . . .. 19 . . . . . . . . . . . . . . . . . . . . .. 71 72 . . . . .. 86 . . . . .. 66 3 . . . . .. 20 . . . . . 1 . . . . . . . . . . . . . . .. 70 9735 . . . . .. 62 83 . . . . .. 64 81 ..... 21 . . . . . . . . . . . . . . . . . . . . .. 46 82 . . . . .. 48 68 . . . . .. 51 65 . . . . .. 22 . . . . . . . . . . . . . . . . . . . . . . 53 8O . . . . . . 45 72 . . . . . . 47 68 . . . . . . 23 . . . . . . . . . . . . . . . . . . . . .. 55 75 . . . . .. 55 70 . . . . .. 55 70 . . . . .. 24 . . . . . . . . . . . . . . . . . . . . .. 41 72 . . . . .. 49 72 . . . . .. 54 66 . . . . .. 25 . . . . . . . . . . . . . . . . . . . . .. 36 76 . . . . .. 48 69 . . . . .. 52 68 . . . . .. 26 . . . . . . . . . . . . . . . . . . . . .. 57 88 . . . . .. 56 72 . . . . .. 57 71 . . . . .. 3; . . . . . . . . . . . . . . . . . . . . .. 45 48 . . . . .. 54 52 . . . . .. 58 56 . . . . .. 29 . . . . . . . . . . . . . . . . . . . . .. 54 66 . . . . .. 56 70 . . . . .. 58 66 . . . . H 30 . . . . . . . . . . . . . . . . . . . . .. 43 86 . . . . .. 51 81 . . . . .. 55 74 . . . . .. 31 . . . . . . . . . . . . . . . . . . . . .. 47 57 . . . . .. 55 65 . . . . .. 56 65 . . . . .. hdean hnnperature..... 64, 37/50 63, 9/16 ‘ 63, 1/2 24 TEXAS AGRICULTURAL EXPERIMENT STATION. Table 1l.—-Soil temperature readings for February, 1918. Feb., 1918. Mean temperature. . . . . Outside. One Inch. Three Inches. 7:00 2:00 5:00 7:00 2:00 5:00 7:00 2:00 5:00 A.M. P. M. P.M. A.M. P. M. P. M. A. M. P.M. P. M. 45 . . . . . . 42 45 . . . . . . 54 . . . . . . 42 50 . . . . . . 57 . . . . . . 40 57 . . . . . . 68 . . . . . . 42 63 . . . . . . 62 . . . . . . 52 65 . . . . . . 78 . . . . . . 52 72 . . . . . . 79 . . - . . . . 52 78 . . . . . . 79 . . . . . . 60 76 . . . . . . 55 . . . . . . 56 57 . . . . . . 50 . . . . . . 52 53 . . . . . . 58 . . . . . . 52 56 . . . . . . 73 . . . . . . 48 70 . . . . . . 71 . . . . . . 53 71 . . . . . . 80 . . . . . . 63 73 . . . . . . 78 . . . . . . 66 76 . . . . . . 68 . . . . . . 66 69 . . . . . . 56 . . . . . . 58 59 . . . , . . 82 . . . . . . 61 80 . . . . . . 78 . . . . . . 60 75 . . . . . . 86 . . . . . . 66 81 . . . . . . 72 . . . . . . 70 70 . . . . . . 61, 4/21 60, 13/42 60, 29/42 Table 12.—Soil temperature readings for May, 1918. ' Outside. One Inch. Three Inches. May, 1918. 7 :00 2 :00 5 :00 7 :00 2 :00 5 :00 7 :00 2 :00 5 :00 A.M. P.M. P.M. A.M. P.M. P.M. A.M. P. M. P. M. 52 54 . . . . .. 59 59 60 60 50' 60 . . . . . . 55 65 . . . . . . 58 62 . . . . . . 56 75 . . . . . . 58 75 . . . . . . 58 75 . . . . . r . . . . . . . . . . . . . . . . .. 60 82 63 75 65 92 . . . . . . . . . . . . . . . . . . . . . . . . 67 85 . . . . . . 66 90 . . . . . . . . . . . . . . . . . . . . . . . . 67 84 . . . . . . 65 93 . . . . . . . . . . . . . . . . . . . . . . . . 68 86 . . . . . . 65 95 . . . . . . . . . . . . . . . . . . . . . . . . 68 87 . . . . . . 68 88 . . . . . . . . . . . . . . . . . . . . . . . . 68 82 . . . . . . 65 70 . . . . . . 66 68 . . . . . . 67 68 . . . . . . 65 82 . . . . . . . . . . . . . . . . . . . . . . . . 66 76 . . . . . . 66 90 . . . . . . . . . . . . . . . . . . . . . . . . 68 83 . . . . . . 66 97 . . . . . . . . . . . . . . . . . . . . . . . . 66 90 . . . . . . 67 85 . . . . . . 66 84 . . . . . . 69 73 . . . . . . 60 60 . . . . . . . . . . . . . . . . . . . . . . . . 64 62 . . . . . . 45 57 . . . . . . 49 56 . . . . . . 57 59 . . . . . . 51 70 . . . . . . 52 75 . . . . . . 57 71 . . . . . . 47 75 . . . . . . . . . . . . . . . . . . . . . . . . 53 69 . . . . . . 45 83 . . . . . . . . . . . . . . . . . . . . . . . . 53 73 . . . . . . 57 88 . . . . . . . . . . . . . . . . . . . . . . . . 62 80 . . . . . . 65 74 . . . . . . . . . . . . . . . . . . . . . . . . 66 70 . . . . . . 62 82 . . . . . . . . . . . . . . . . . . . . . . . . 62 77 . . . . . . 50 83 . . . . . . . . . . . . . . . . . . . . . . . . 64 77 51 83 . . . . . . . . . . . . . . . . . . . . . . . . 65 77 51 84 . . . . . . . . . . . . . . . . . . . . . . . . 64 78 60 85 . . . . . . . . . . . . . . . . . . . . . . . . 65 81 . . . . . . . . . . . . . . . . . . 66 88 . . . . . . 66 82 . . . . . . . . . . . . . . . . . . 72 84 . . . . . . 73 81 65 82 . . . . . r 68 8O . . . . . . 68 77 60 75 . . . . . . 62 73 . . . . . . 67 7O 6O 83 . . . . . . . . . . . . . . . . . . . . . . . . 65 80 . . . . . . Mean temperature. . . .. 69, 2/7 69, 7/12 69,» 28/31 l PINK Roor DISEASE or ONfoNs AND Itrs CONTROL IN TEXAS. 25 It is unfortunate that complete data on soil temperature under Laredo conditions, Where most of these studies were made, are not as yet fully available. More soil temperature studies are now being made under greenhouse conditions in soil temperature boxes, such as are used at the Wisconsin Agricultural Experiment Station, Where the temperature may actually be maintained at any desired degree. From the brief studies presented above it may be safely stated that the grower should do everything pos- sible to plant his crop at such a time that the greatest amount of growth will be made when the soil temperatures are fairly low, ranging from 60 to '75 degrees Fahrenheit. Avoid sowing seed beds so early that soil temperatures vrill yet be too high, and hence be favorable for pink root development. Also, avoid seeding too late, which would throw the period of bulbing during the hot months of the year, at a time when a high percentage of pink root may be developed. Furthermore, great attention should be paid to the necessity of frequent waterings during the bulbing period. This will encourage rapid growth and will help to keep the soil fairly cool.. When planting is done late, everything possible should be done during the hot months of the year, so as to reduce the soil temperature by several degrees just preceding the bulb- ing period. This, of course, will be accomplished by irrigation. THE CAUSAT, ORGANISM From previous discussion it becomes evident that a Fusarium fungus, tentatively named Fusariuim maltli Taub.,* is the cause of pink root of onions. The organism was grown on a variety of media, chief of which were potato plugs, hard lima bean agar (Fig. 2, d to g), and hard rice agar. It should be stated that u‘. nwlli somewhat resembles Fusariunt occysporuwz, but differs sufliciently to make it distinct from the latter. The mycelial growth of F. malli varied very little on the three kinds of media above mentioned. The spore measurements,however, that is, the macroconidia, seemed to be greatly influenced in size by the media on which the fungus grew. The largest sized spores were obtained on hard bean agar and the smaller sized on potato plugs. Furthermore, microeonidia were apparentlyformed only on hard bean agar on the scant mycelium which grew on the border near the glass of the tube. A description of FUSLITZDIMW, stall/i. fellows. Microconidia (Fig. 3, d) formed on aerial mycelial branches, vary- ing in shape and in size and slightly pedicellate. Of the macroconid.ia, the three septate type seems to dominate (Fig. 3, e). probably over . 98 per cent. The remaining 2 per cent. are four septate; five septate spores being almostrare. On potato plugs, pionnotes numerous, and assuming the color and consistency of butter, thus distinguishing it from FusM/ium oxy/sporuvn which. only has pseaudopionnotes. Three sep- tate eonidia vary from 3O X 4l-u to 40 X 5u. The four septate eonidia (Fig. 3, b) have about the same measurements as the three septate. hilycelial growth scant, flat, being replaced early by a heavy layer of pionnotes. Absence of sclerotia, and very little color on starchy media is especially noticeable, except on potato plugs, where the color varies p *F. malli was named in honor of the Junior Author. 26 TEXAS AGRICULTURAL EXPERIMENT. STATION. from green to purple. The organism produces an abundance of chlamy- dospores, which are both terminal and intercalary (Fig. 3, a, c and f) ; the zero septate dominate. Frequently and in old cultures, they are found in chains or in large masses as thougdi held together by niucilage. F. mrllli is pathogenic on onions and garlic, causing a disease known as pink root. h i J Figure 3. (a, c an_d_f) Chlamydospores of Fusaritzm mallj._ (b and e)_ Three and four sea macroconidia of Fusarzum malli. (d) Microconidia of_ Fusarium mallz. (g and h) Microlilang macroconidla of Fusarium No. 2. (i and J) Chlamydospores of Fusa- num o. . OTHER FITSARIA ASSOCIATED WVITH F. LIALLI Of the many other species of Fusaria isolated from pink root of onions is one carried in the laboratory as F usarium N0. 2 (Fig. 2, d and g; Fig. 3, g to which invariably seems to be associated with F. malli, and which resembles somewhat Fuisarium martii. H0'.'.'C“F?l‘, PINK ROOT DISEASE 0F ONIONs AND Icrs CONTROL 1N TEXAS. 27 it seems to differ from the latter by the fact that it produces macro- conidia very sparingly. These when present are three and four septate, varying in size from 32 IX 5u to 5O X 5J3u; microconidia predominat- ing; absence of pionnotes and pseudopionnotes; sclerotia numerous, sin- gle or in groups varying in color from dark green to dirty gray green; mycelial growth abundant, fluffy, thick, slightly raised, imparting prac- tically no color to substratum. However, a distinct brownish gray color is imparted to hard rice agar media; chlamydospores numerous, large, terminal or intercalary. Fusarium No. 73 is apparently non-parasitic but seems to increase the virulency of F. stall/i. The parasitism, on Irish potatoes, of Fus/zrvlum malli and Fusarium No. 2 has not been definitely ascertained because of the fact that of the numerous inoculations made, the checks rotted as readily as those that were inoculated, although every aseptic condition was observed. It was difficult,‘ however, to secure, O11 the local market, potatoes which were absolutely sound and free from bruises or blemishes. This ac- counts for the negative results of these inoculations. This parasitism is now being further investigated. FALSE BLIGIIT In plants suffering from piiik root, or during seasons of extreme heat and drouth, the tender tips of the rapidly growing onion leaves are sometimes inclined to wither and to die down gradually from the top to the bottom of the plant; withering which gives the plant the appearance of having blight resembling that which is known in the northern states as downy mildew (Peronospiora schZeidenwla-nat). Such withered‘ leaves turn white and dry up. The term blight, therefore, in this case is misleading, primarily because the downy mildew blight is not known to occur in the Iiaredo onion districts in Texas, and also because the trouble, as far as is known, does not seem to be caused by any parasitic organism, but may be brought about by various condi- tions. The trouble becomes apparent: (l) When the plants suffer from lack of moisture and are suddenly supplied with an abundance of water. (2) Attacks from Onion thrips will reduce the vigor of the plant, and thus cheek its groyvth and result in the premature dying of the tips of the foliage. (3) Badly diseased plants suffering frompink root, and hence lacking in vigor, will often manifest the symptoms of the false blight just mentioned. Not infrequently the blighted foliage later becomes covered with a number of various fungi, chief of which may be mentioned ZlIaCIIOSJOOTVII/ILW/l/ parasiticum Thuem. and Macrospo- riu/m porri- Ell. These species of fungi are never found on healthy foliage, hence they probably are saprophytes or semi-parasites. STUDIES OF POSSIBLE CONTROL METHODS From a practical consideration it is important to know not only the cause of the disease, but also the best means of control. Various meth- ods were tried out with a view of determining which of these could be best carried. out in practice, requiring the minimum expense and labor. Effect of Fertilizer. Claims are frequently made by growers that certain fertilizers will cause pink root. In order to determine whether 28 TEXAS AGRICULTURAL EXPERIMENT STATION. or not fertilizers have any effect in controlling or favoring pink root, tests were carried out 0n two different farms, and 0n soils known to be infected with the pink root disease. The fertilizers were applied in dry land ahead of seeding. Irrigation followed soon after the seed was sown. The seeds were sown September 1'7, 1917. A count of the per- centage of pink root plants was made when the sets in the seed bed were 60 days old. The general results of these tests are shown in Table 13. From Table 13 it appears that the use of certain fertilizers, such as tepary bean ashes, acid phosphate, on plats 1 and 2, Farm No. 1. would tend to reduce considerably the amount of pink root in the seed bed. However, from the results on plats 1 and 2, Farm No. 2, it is seen that the same fertilizers showed about as much pink root develop- ment as did the other fertilizers on the remaining plats. From these tests it is plain that no general conclusion can be reached as to the difference in effect of the various fertilizers. Furthermore, plats 1 and 2, Farm N o. 2, were much more seriously infected with pink root than plats 1 and 2 of Farm No. 1. This probably explains the apparent difference in results. All things being equal, it seems that fertilizers do have a tendency to retard the development of pink root in the seed ‘bed, and this is done, not in reducing the amount of disease, but by accelerating growth and encouraging formation of new roots faster than old ones are destroyed by the disease. N o fast rules, however, can be laid down as to the kind of fertilizer to use for the seed bed. Each grower should make a close study of this problem and test the various fertilizers in various places on his farm, in order to determine which combination is best under his own particular conditions. Table 13.—Comparison of effect of fertilizer on pink root soil used in seed bed at Farm No. I and Farm N0. 2. Farm No. 1* Farm No. 2* Per _cent _ _ Per cent Fertilizer Used Per Acre. Plat Pink Fertilizer Used Per Acre. Plat Pink No. Root. No. Root. Tepary bean ashes . . . . . . . . . . . . 1 4.2 Tepary bean ashes . . . . . . . . . . . . 1 19.6 - Acid phosphate 1180 lbs. .. . . . . 2 7. 5 Acid phosphate 1180 lbs . . . . . . . 2 31.4 Mesquite wood ashes 5225 lbs.. 3 4. 5 lVIBSQUItC wood ashes 5225 lbs.. 3 14.1 Tankage 1140 lbs . . . . . . . . . . . . . 4 17. 5 Tankage 1140 lbs . . . . . . . . . . . . . 4 13. 5 eck . . . . . . . . . . . . . . . . . . . . . . 5 24. 13 Check . . . . . . . . . . . . . . . . . . . . . . . 5 22 Acid phosphate 450 lbs.. Arid phosphate 450 lbs, Nitrate of soda 110 lbs. . '. . . . 6 27 Nitrate of soda 110 lbs . . . . .. 6 19.3 Manure only, 24 tons . . . . . . . . . 7 24. 13 Manure only, 24 tons . . . . . . . . . 7 28.9 Cotton seed meal 570 lbs . . . . . . 8 21.5 Cotton seed meal 570 lbs . . . . . . 8 20.5 *Names of owners are purposely omitted. ln ciomparing Table 13 with Table 14-, one sees some effects of fer_- tilizer on growth in a healthy soil. From Table 14 it is found that there are traces of diseased plants in various fertilized plats on sup- posedly healthy land which has never grown onions before. No doubt this is due to the fact that the tools which were used in plowing and preparing the seed beds, and later for the cultivation, had been pre- viously used on the pink-root infected fields on the same farm; hence, introducing the fungus to the healthy seed beds by carrying soil par- ticl.es which adhered to the plows and other implements. PINK Roor DISEASE or ONIONS AND Irs CONTROL IN TEXAS. 29 Eficct of Lime and Sulphur. It is often claimedthat applications of lime or sulphur 0n pink-root infected soil will control the disease. The results of various applications of lime and sulphur, singly and in com- bination, on pink-root infected soil at three different farms, showed that neither lime nor sulphur had any effect whatsoever in reducing the amount of pink root in the seed bed. Table 14.—Effect of fertilizer on pink-root free land in seed bed at Farm N0. 3. _ _ Not Limed, Limed, No. of Fertilizer Used Per Acre. Per Cent Per Cent Plat. Pink Root. Pink Root. 1 . . . . . . Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trace . . . . . . . Trace 2;. . . . . Nitrate of soda 150 lbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . None . . . . . . . None 3 . . . . .. Sulphate of ammonia 120 lbs . . . . . . . . . . . . . . . . . . . . . . . . . None . . . . . . . None 4 . . . . . . Sulphate of ammonia 245 lbs . . . . . . . . . . . . . . . . . . . . . . . . . 1 plant . . . . . . 1 plant 5 . . . . . . Nitrate of soda 230 lbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 plant . . . . . . 1 plant 6 . . . . .. $6 Cyanamid 500 lbs.,** % check . . . . . . . . . . . . . . . . . . . 1 plant, none 1 plant, none 7 . . . . . . 8 tons manuret . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 plant . . . . . . 2 plants 8 . . . . . . Cotton seed meal 1000 lbs . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 plant . . . . . . 2 plants ‘ 9 . . . . . . Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 plant . . . . . . 1 plant 10 . . . . . . Cotton seed meal 1000 lbs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 plants. . . . . 4 plants 11*. . . . . Mesquite wood ashes 4700 lbs’ . . . . . . . . . . . . . . . . . . . . . . . . 2 plants. . . . . 2 plants *In Plat 11 the plants were decidedly burned as a result of an excess of wood ashes. **Cyanamid shows distinct stimulation. _ _ tThe application of fresh manure just ahead of seeding does not ‘seem to be so beneficial. In this test, drilling in the seed followed immediately after the application of quickly acting fertilizer without any apparent ill effect on germination. his was also true with an appli- cation of 245 pounds sulphate of ammonia and 230 pounds nitrate of soda per acre. From this it seems that as long as the land is irrigated immediately after the application of fertilizer and frequently enough thereafter that there is no ill effect from such a practice. Effect 0f Fertilizers 0n Y ields in a Pink Root Soil. Repeated ob- servations have shown that the best yields of onions, assuming that healthy sets are used, are obtained from lands which have been recently brought into cultivation and which have never produced a crop of onions, or at least lands which have not produced a crop of onions for a long period of years. Yields on new lands frequently average 400 crates per acre. There are, of course, records where 1000 bushels' per acre were produced. Such yields are secured only by the use of heavy ap- plications of fertilizer, coupled with special care in the preparation of the land and the management of the crop. On lands affected with pink root, the yields are reduced considerably. Hence special care and fer- tilizers are needed, to nurse and urge the crop along, in order to obtain reasonable yields. If this is not done, the crop onbadly infected soil will be a failure in the sense that yields are too small to be profitable. In dealing with infected land one finds that the problem is a com- plicated one, since it is necessary to choose fertilizers that will force rapid growth and produce healthy roots faster than the disease can destroy, in order that the bulbs may attain a reasonable market size. To determine just what are the best fertilizers for accomplishing that purpose, three series of field experiments were carried out on three different farms, all of which were known to be badly infected with the pink root "fungus. The results of these experiments are shown in Tables 15, 16, and 1'7. From Tables 15 and 16 it is noticed that yields are extremely low. This, however, was due to the fact that both fields were early infested by thrips. This severe attack, together with pink root infected soil, resulted in low yields. 30 TEXAS AGRICULTURAL EXPERIMENT STATION. 63: HOG ma? kONZmMHQm H053 MOJWmJ 32a M0030 Cm .315 3 “BEE Qohi. 60355 Eowoesa hwnBo we vEwZw. . . . . . . . . . . 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It has been indicated, in a general way throughout the discussion of the control methods, that with pink-root infected plants, especially when these are again planted on pink-root -infected soil, the only hope of a commercially profitable crop consists in the ability of the grower to supply quickly available plant food in quick succession. The plants must be kept vigorous enough to produce new rootlets as quickly as diseased ones die. By this method the crop will go on through the Winter season, reach the bulbing stage, and have a fair chance to produce marketable sized onions. This general proposi- tion is cl.early sustained by a study of Table 1'7, which was the only one of the fertilizer plats which Was not so badly attacked with thrips as to interfere seriously with a fairly safe interpretation of the results. The first result indicated in Table 1'7 is that growers with pink-root infected soil, or pink-root infected plants, should begin with the trans- planting of their crops to apply quickly available fertilizers; then in succession to the hulbing and maturing of the crop. The correctness of starting early to give quickly available fertilizers is indicated by the results shown in plats 10, 11, and 22 of Table 17. Two of these were given treatment with nitrate of soda and sulphate of ammonia, about even amounts, at the time the onions were transplanted. Plat 11 of Table 1'7’ was given a slightly larger portion of cyanamid because a longer period of time is required to give up its nitrogen. The second application, of similar amounts, was given each plat in January, about mid-season of the growth of the crop. The third application was given just about the beginning of the bulbing period. The theory of these three tests Was to show the value of continuous feeding of diseased plants, and of encouraging a new root growth as fast as others died= The results show the method." to be, correct for the reason that plat 10 gave a yield of 290.2 crates per acre, with 45 pounds nitrogen having been applied. Plat 22 produced 312.1 crates per acre, with 412 pounds nitrogen applied; and plat 11, 357.8 crates per acre‘, with about 48 pounds nitrogen applied. These three yields compared show the highest yields of any amounts of fertilizers, where equal amount, or‘ even double amounts of nitrogen were applied, but which had been applied as is usually done, by heavy applications just ahead of transplanting, or soon after transplanting. l For comparison it is seen that in plat 3, Table 17, about 137 pounds of nitrogen had been applied per acre, with only 332.5 crates per acre yield. This is only slightly above the yields of plats 10 and 22*, even though more than three times as much nitrogen had been supplied. Ap- proximately the saine result is seen from plat '7, where tankage had been used, and where about twice as much nitrogen had been supplied. This suggests the theory which has been proved in practice where pink root plants, or pink root soils are involved; namely, the liberal supply of nitrogenous fertilizers is not calculated to carry a pink root crop through to maturity, even though the plants boost a disproportionate growth in the beginning. From a study of plats 1, 2, and '7, inclusive, and in- cluding plats 15 and 16, Table 1'7, it is evident that they have all failed to produce a yield in keeping with. the amount of nitrogen supplied to the pink root soils and pink root plants, because they failed to give enough nitrogen during the latter part of the growth. In‘ other words,‘ the important fact which must be impressed upon every grower who 34 TEXAS AGRICULTURAL EXPERIMENT STATION. has diseased lands or sets, is that he cannot hope to compete with the, disease unless he applies such quickly available nitrogen fertilizers as were used in plats 10, 11 and 22, Table 17, so that a supply of nitrogen is available at every stage of the growth of the crop from the beginning to the end. An over supply of nitrogen which may be available faster than the development of the disease, serves no purpose in the control of pink root. On the contrary, that cron will be carried through a diseased soil best which has constantly enough nitrogen fertilizers avail- able to be used by the plants as rapidly as the encroachment of the disease demands. For that reason it must be again repeated and en- forced that nitrate of soda, sulphate of ammonia, or cyanamid are the fertilizers which best enable the grower to meet this condition. How- sever, the authors Wish to make it clear that they understand the danger of developing what the growers call a “soft” or “tender” growth of the plant by using these fertilizers so early in the growth of the crop. If we were advising concerning the management of a crop of onions on healthy soils, where sets had been used which were free from disease, we would agree that the use of such quickly available fertilizers should not begin until later in the groxvth of the crop. However, a grower who has infected soil and infected plants has no alternative. He takes greater chances from loss from the disease if he does not use these quickly available fertilizers from the beginning of the growth of the crop, than he takes from the danger of loss to the crop from setbacks of climatic conditions which may injure the tender growth somewhat more seriously than if the nitrogenous fertilizers had not been used so earlv. ’ It is also clear from plat 11, Table 17, that with a fertilizer which is rich in nitrogen but which at the same time gives it off gradually for a longer period of time, it is much safer to use liberal quantities of it in the beginning of the crop. Cyanamid usually shows about 16 per cent. nitrogen, wihich it gives off over a period of fifty to seventy days under Webb County soil conditions, with irrigation. Sulphate of ammonia would probably give off the same amount in twenty to thirty days less time, whereas nitrate of soda distributes itself over a still lesser period of time. Hence. if the growers understand this difference and exercise judgment accordingly, they will secure better results with sulphate of ammonia than with nitrate of soda, provided the soils are rich in lime and hence not acid in their reactions. Practically all the Texas Ber» muda onion soils are rich in lime, and usually alkaline in reaction. For the same reason cyanamid will give better results than sulphate of ammonia. To sum up, there seems to be no doubt but that it is advisable and necessary to use fertilizers on pink-root infected land to obtain profit- able yields. This is especially true when diseased green sets are used. As a general guide it might be stated that for the average soil infected with pink root. it is necessary to use fertilizer, not less than 1000 pounds per acre, and. of a brand which shows an analysis of about 7 per cent. acid phosphate, 5 per cent. nitrate of soda, and 2 per cent. potash. (In general, Webb County onion soils contain suflicient avail- able potash.) In addition, liberal applications of nitrate of soda should be given, at intervals, during the bulbing season. PINK Roor DISEASE OF ONIONS AND ITs CONTROL IN TEXAS. 35 For purposes of best results, the fertilizer should be applied about thirty days ahead of transplanting time and should be Well worked into the soil. As soon as the green sets are transplanted from the seed bed to the field, and after they have become well rooted and well started out, it is advisable to apply the first amount of nitrate of soda to the extent of about 100 pounds per acre. The second application of nitrate of soda should be given in like amount at about the middle of February, provided, of course, the crop shows need of it. The third and last application of nitrate of soda should be given about March 1, at the rate of 100 pounds per acre. From this, it would appear that one heavy application of fertilizer and three of nitrate of soda are recom- mended for pink-root infected soils. It should, however, be under- stood that such recommendations are given only to growers who are unable to secure healthy plants or who, for the most part, must depend on pink-root infected sets as well as diseased soil. It should not be "n forgotten that the use of nitrate of soda will promote rapid, tender growth, and that such plants may suffer severely from sudden frost, or drouth as happens in case of a sudden breakdown in the irrigation plant. This element of risk, however, is not so great in the final re- sults, as it is in taking a chance of producing a profitable crop on a pink-root infected soil which lacks plenty of quickly available plant food. There is no doubt but that soils deficient in humus are doubly unfit ifor onions. Such soils do not promote rapid growth, which means the development of more pink root. They also fail to take up the usual amount of irrigation water, which in turn is unfavorable to the crop. It is soil deficient in organic matter which needs the maximum amount of fertilizers. FORMALDEHYDE TREATMENT OF PINK-ROOT INFECTED SETS Since pink root is carried with the green sets which have previously grown in an infected pink root soil in the seed bed, it becomes evident that some form of treatment is necessary so as to kill without injuring the green sets the disease producing organism. Two standard fun- a gicides were tried, namely, formaldehyde and copper sulphate, and the treatments were carried out on greenhouse-grown sets. The strength of formaldehyde tested was 2 and 5 per cent, respectively. The diseased plants were soaked from five minutes to four hours (Fig 2, a). Some of the diseased roots of the green sets were cut off before treatment, while others were left undisturbed. The results of the treatment are shown in Table 18. From Table 18 it is seen that pink root was reduced considerably in the 5 per cent. formaldehyde treatment, when the sets were soaked for five minutes. Hon/ever, at this strength the treated sets were retarded severely in growth and in root formation. Hence, for practical pur- poses this strength cannot be recommended. With soaking the infected sets for ten minutes, injury was more noticeable; with longer soakings, from fifteen minutes to four hours, the sets were practically all killed (Fig. 2, a). A 2 per cent. formaldehyde solution does not seem to injure appreciably the sets, and apparently destroys the pink root fun- gus in the sets when soaked for ten minutes, provided the treated sets are planted into a soil free from pink root. From Table 18 it is fur- 36 TEXAS AGRICULTURAL EXPERIMENT STATION. took vkckn kkm .2“ .5: QB kookoon 3mkn of ko 53.32 33 wkkkoEkmvkk okrflkokokmkkkkok kkw 5C ékokon kk?okm coon v25 mkkokkko o: okmkk? kkokkmkm om»: .kkom kook .Mu®£o 3 UQkmnkEOO Mk3? woo @3533 n3?okU._. oU Eokk c313 mo? kkkokkkkkonxo mkkkk 5 kkow: kkom* Ckg QN~FMUW k Q . . . . . . . . . . . . . . . . . . .. .... . . . . . . . . . . ... Tcogasggzik; kmHk.kTkkmkkwwkkkwowasmmm ................. .5” iwwkmmwk .... .. Mwmkkmkkkkmwkmm ..... 55mm Qook vkckn k? . .kkow kook vkckn kooukkkkokmkkD . . . . . . . . . . . . . . . . . . .502 . . . .3555 m . . . . .. 23 mkosckkomk >523: mm . . . . . . 355 kvn m 000k vkckn kk< . . . . . . kkow wook vkckn UQNZWkQQmGD . . . . . . . . . . . . . . . . . . 6502 . . . @3515 m . . . . .. $3 mkoskkkkomk k523i mm . . . . . . .53 kun HOOH . . . . . . .Z°w Foch %vmvN:TmQ#wcD . . . . . . . . . . . . . . . . - . .QH~OZ . . . .WUPH~G+E @ . . . . .. 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Swfiwwmkmm . . . . . . .53 kon m 53k. kk< .*kkom kovwkkkkoukmkk: 5 .92 4N .>oZ . kko 5o kokk mkook wommowkfl . . . . . rkkkokk k Mkkknk 5k? kooaookck nkoskkk..wnk.omokkmm . . . . . . .58 kon m . . . . . . éook .._.k~..~k.okkkw?kom5k hwfikaokk wkmookkflkkkak ikow wonkkkkvfikk: 5 okmk w >02 to 5o “on fiook koommomkfik . . . .w@.._5kk5 om vkkkkn 5k? @3035 wkoskkkmflwokkmm . T . . . . Qcoo kon m 3 x5 k ._.kkoo_muoflkowm>mwkkwkkk.knk w ikow koonkkkkokwc: 5 wkmk v .>oZ . kko 5o Ho: 300k koomwvmknk . . . 53:55 om xokn 5k? kookookck mkonkkkkkomwkmm . . . . . . .53 kon m >595 “Esknvwkwkammokww m .28 kofikifiés E .22 Q .>QZ . k6 :6 2E B2: @3825 . . .3255 5 i3 5k? @382: “Eékkwm m.» . . . . . . 4E: k8 m, km . .> , , . . . .. . . . 300k 52-35 wkokfio 53k. wkcwkn m ikow koonkkkkokvo: 5 £2 q >oZ to k5. kokk wkook koomwomknk . . . .3555 ok vkckn kkkk? kxbookkkk wkoskkwmflmwkmm . . . . . . .53 kon m kxnkkfirokk mkokkko kook vkkkkn k .*kk.ow kooskkkkvkmc: 5 .32 .k\ .>oZ . Jkko 5o ko: wkoom koowmomkfik . . . .mok5kk5 m Mkkkkk kkkk? kookookck wfikkkkknkvm mm . . . . . . JQQOLQQ m $253M dokkkwknk okokk>> 5km 55>? akcmknk ko .5o5o.wuk.fi 53D $52k dkomkkokokmkkkkok fikockkmokk. $50 ko kimkkvk ko konkkksZ 5km kEkvk ko kkkucokkm .33 coukm kookookck 5o kkkofikkwoko. okkzkkokokmkkkkok ko Hookkmklwk 25k PINK Rootr DISEASE or ONIONS AND ITs CONTROL IN TEXAS. 3'7 ther seen that when healthy onion sets are treated in 5 per cent. for- maldehyde for ten minutes and then planted in a pink-root infected soil, they may later show 100 IJQI’ cent. infection with pink root. This again indicates that the ten-minute treatment in the 5 per cent. formaldehyde decidedly weakens the plants. The bulb plate in diseased plants ac- tually peels and falls out as a result of treatment with the 5 per cent. strength. — Formaldehyde treatment of diseased sets was also carried out in the field. It was found that the using of formaldehyde at the rate of one pint of the chemical in three to four gallons of water, then clipping the roots and dipping the sets in the solution so as to thoroughly wet them, and then placing the treated sets in sacks and within an hour planting them in the field, would completely kill all the treated plants. It was further found that formaldehyde, at the rate of one pint in twenty gallons of water, and one pint in fifty gallons of water, putting the plants in crates and soaking in barrels of these solutions for ten minutes, decidedly injured the diseased treated plants. Furthermore, one pint of formaldehyde in one hundred gallons of water, the sets being soaked for ten minutes, would kill about 25 per cent of the weaker plants, while the others would start new roots very slowly. Finally, when pink- root infected green sets were soaked for ten minutes in formaldehyde at the rate of one pint in two hundred gallons of water, only one-half of 1 per cent. of the plants were killed; the sprouting or starting of new roots was delayed fully a week. In all the above field experiments the tops of the treated plants were cut off. The use, however, of similar strength of formaldehyde, that is, one pint in twenty-five gallons of water, one pint in fifty gallons of water, one pint in one hundred gallons of water, and one pint in two hundred gallons of water, with the leaves of the sets unclipped, resulted in less serious injury to the plants. When irrigation‘immediately follows the planting of dipped sets, the injury is decidedly lessened. The weaker sets are invariably killed. In the summing up of the effects of formaldehyde on pink root sets, it should be stated that such treatment is dangerous, even though weaker strengths, consisting of one pint in two hundred gallons of water are used. Therefore, until further work is carried on, the treating of dis- eased pink root sets in various lengths of time is not advocated, and should not be attempted by the grower. It is safest to discard diseased sets. From a practical consideration, no treatment is considered use- ful if it retards growth and the ouick formation of new roots. Such a setback exposes the plants to reinfection, which, if it occurs again, is more serious than using untreated diseased plants. The laboratory treatments of copper sulphate solutions were 1 gram in 500 c.c. of water and 1 gram in 2000 c.c. of water. The results of these treatments are indicated in Table 19. _ From this table it is seen that the dipping of diseased plants in copper sulphate solution at the rate of 1 to 500 for fifteen minutes to five hours did not cure the pink root. In every case the sets were either iniured or killed. This is explained by the fact that the treatment was too strong. As to‘ the treatment in the weaker solution, 1 to 2000, copper sulphate, the roots of the treated sets were not destroyed, even though the treatment was prolonged for four hours. However, pink root was not controlled. Hence, as far as this experiment goes, it is evident that copper sulphate 38 TEXAS AGRICULTURAL EXPERIMENT STATION. at the rate of 1 t0 500 and 1 to 2000, cannot be recommended. It is possible that fungicides other than formaldehyde or copper sulphate may be found which would destroy pink root in green sets Without in- jury to them. This possibility is now being investigated. SOIL STERILIZATION OF SEED BED It has already been stated on page 15 that the pink root organism lives in the soil from year to year. This is true for seed beds as well as for field conditions. When onion seeds are planted in a diseased seed-bed soil, the green sets will become infected and thus carry the pink root fungus to the field. It is imperative, therefore, that the seed should be planted on a healthy seed-bed soil. As far as possible, land which has never been devoted to onions should be used for seed-bed purposes. When this is not possible and the onion grower finds him- self compelled to use infected soil, it will, of course, be necessary to sterilize that soil in order to free it from the pink-root germ. Experi- ments were carried on in the laboratory and in the field with formal- dehyde. Steam sterilization experiments were carried on in the labora- tory only, as no facilities were at hand to try this sterilization in the field. Several pink-root infected seed beds were treated outdoors with formaldehyde at the rate of one pint in twenty gallons of water and applied at the rate of one gallon to the square foot of bed space. After treatment, the soil was covered with a canvas for twenty-four hours in order to retain the formaldehyde fumes. The seed was sown a week after the treatment. The germination of these seeds was normal when compared. to the check. In the treated beds (see Table 20) the per- centage of pink root was reduced to 0.6 per cent. The check or un-. treated plats showed over 80 per cent. pink root on the sets, and this percentage increased rapidly as the season advanced. In the treated beds, pink root did not increase further than a mere trace. This dis- tinttly shows the advantage of treating infected soil with formaldehyde. Similar experiments carried on in the laboratory, in which the same strength of formaldehyde as above was used, yielded 100 per cent. healthy sets in diseased soil. The trace of pink root in the treated beds in the field was, undoubtedly, brought in through accidental in- fection. In treating the seed-bed soil with formaldehyde, one should carry out the operation in practice as follows: The seed beds are prepared in the usual way, with the exception that they are made to average not m.ore than eight feet in width. As the bed is being flooded, a quantity of 40 per_ cent. formaldehyde is placed in a container and allowed to drip into "the water as it enters from the ditch through the cut in the border. The dripping should be so regu- lated that it will fall at the rate of one pint to twenty gallons of water. With a little experience and calculation, the inflow of Water and rate of dripping may be readily figured out. It is best to carry out the for- maldehyde treatment after the last preparation of raking, leveling, and harrowing of the bed. This means from five to eight days before sow- ing the seed. Laboratory experiments on sterilizing pink-root infected soil with steam have shown that the causal fungus may be killed by steaming 39 PINK ROOT DISEASE OF ONIONS AND ITs CONTROL IN TEXAS. .0000. =0 .00 .02 .0©000A 0© .00 .>0Z . . 11.0000: .00 E000 00000000005 0000 x50 0050000 0m . . .. . . . . . 1.00mi: .0000 0050 .0©0001_ 5000 .00 0000 00003 050 ©0300? 0005B 02.0 0000000 ©00© :4 0© . . . . . . 00:05 .00 0000000 ©000005 0000 x50 005 0:0? mm . . . . . . . . . . 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Table 20.——Effect of formaldehyde treatment on pink-root infected soil. Time of Strength of " No. 0 Formaldehyde Formaldehyde Amount Per Per Cent Plat. Treatment. Used. Square Foot. Pink Root. a . . . . . . . . . . . . Sept. 10, 1917 . . . . . . . . 1 pt. to 2O gal. water.. 2 gallons*1'. . . . Trace b . . . . . . . . . . .. Sept. 10, 1917 . . . . . . .. 1 pt. to 20 gal. water.. 1 gallon*T. . . . . Trace c . . . . . . . . . . . . Sept. 10, 1917 . . . . . . .. 1 pt. to 20 gal. waten. 1 gallon*'|'. . . .. Trace d . . . . . . . . . . . . Sept. 10, 1917 . . . . . . . . 1 pt. to 20 gal. water.. 11/2 gallons. . . . Trace e . . . . . . . . . . . . Check . . . . . . . . . . . . . . . Check . . . . . . . . . . . . . . . Check. . . .. . . . . 8O per cent _f . . . . . . . . . . . . Check J .- . . . . . . . . . . . . Check . . . . . . . . . . . . . . . Check . . . . . . . . . 80 per cent E . . . . . . . . . . . . Dec. 7, 1917 . . . . . . . . . 1 pt. to 2O gal. water.. 1 gallonT . . . . . . Trace . . . . . . . . . . .. Dec. 7, 1917. . . . . . . .. 1 pt. to 2O gal. water.. 1 gallonT. . . . .. Trace ' TFormaldehyde dripped into water as it_ flowed in the bed during irrigation. *Formaldehyde applied just before sowing seed. the soil at fifteen pounds pressure for two hours. It is, of course, probable that a shorter steaming will accomplish the same results. On a commercial scale, therefore, it is advised that the seed-bed soil should be treated With steam i11 the same way as the tobacco growers in other states are doing to rid. the soil of Thielavia root rot. The method of steam sterilization as recommended by Johnson* is as follows: “The most practical method yet devised for the sterilization of seed beds by steam is the ‘inverted pan method.’ This method was first used by Shamel for sterilizing nematode infested soils in Florida. A gal- vanized iron pan, six feet by ten feet and six inches deep, is inverted over the area to be sterilized after it has been prepared for seeding. As the edges of the pan are sharp, they can be pressed into the soil an inch or more, thus forming a tight compartment under the pan into which the steam is run 30-60 minutes from a boiler at a pressure of 80-] 50 pounds. The time of steaming depends largely upon the type of soil and its moisture content and compactness. Loose sandy, moist, but not wet soils, are more easily and rapidly steamed than heavy and wet soils. The p251 is made eight inches in depth, which is probably more desirable in some cases. The pan could be made twelve feet in length without losing any efficiency where large boilers are used. The handles should preferably be placed on the sides instead of on the ends, so that the pan could be moved from one section of the bed to another without the operator’s walking on the sterilized soil. The weight of such a. pan is approximately 400 pounds. A one-inch steam hose should be used to connect it with the boiler. Atraction engine such as is used for threshing is most convenient to furnish the steam.” SEED DISINFECTION Since most of the onion seeds planted in the vicinity of Laredo, and in fact all through the Rio Grande Valley’, are mostly secured from the Bermuda Islands, it became necessary to determine whether these seeds _ were carriers of pink root. Accordingly, a large quantity of untreated seed was planted in pots of steam sterilized soil. This was done for nearly three seasons, and never did a single plant show pink root. *Johnson, James. The control of damping-off disease in plant beds. Wis. Agr. Expt. Sta. Research Bul, 31:29-61, 1914. PINK RooT DISEASE OF ONioNs AND ITs CONTROL 1N TEXAS. 41 Thus for all practical purposes, this experiment proved that the seed* do not carry pink root. Hence, it is not necessary t0 treat the seed with formaldehyde as is recommended for seed treatment of other dis- eases. Oni.on seeds, when treated with forn ildehyde solution stronger than one part in three hundred of ivater, Will actually be delayed in germinating. Hence, it is Worse than. a Waste of time and money to give onion seeds the formaldehyde treatment with a view of controlling pink root since the seed appear not to be carriers of the disease. EFFECT OF ROTATION Field observations (lefinitely show that the rotation of crops is bene- ficial in reducing the amount of pink root, although rotation Will not eliminate it altogether from the soil. From a practical consideration, pink rpot lanélsbshoiuld bei given 1a rest from 31y lking p; oniocnsgshallots, or gar ic, an e evote to ot er crops. t eas ree o our-year rotation is recommended. It is popularly believed that onions are the one crop that can be grownicontinuously on the same land for a number of years. This ‘may be true provided good attention is given to keeping out disease and to maintaining the fertility by applying manure and plowing it under. Great danger lies in the fact that When onions are grown too long on the same land, pink root may eventually be introduced and spread, and in the long run seriously reduce the profitable culture of the crop. When starting with a virgin land, one should not grow onions for more than three or four consecutive. years, even though healthy plants are always used. A two-year rotation every fourth year, during which no onions are grown, is strongly recommended for lands free from pink root. In dealing with infected soils, the grower is urged that a. four-year rotation without onions be adopted before he may reasonably expect anything like a normal yield, even though he uses healthy plants. GENERAL CONTROL RECOTNTlYEENDiVXTIONS 1. When selecting the soil for onion.s, the grower should make every effort to secure only virgin lands; that is, soil which has never grown onions, or at most but one or two crops. 2. It is safer to produce one’s own green sets than to buythem else- where without knowing the soil, and its freedom from pink root. 3. If diseased soils must be used for seed-bed purposes, the bed should be disinfected by drenching with formaldehyde at the rate of one pint in twenty gallons of water applied, one gallon of the solution to the square foot of soil area. Steam sterilization is equally effective and should be used whenever steam facilities are at hand. 4. Since pinkroot is a disease which is carried over in the soil from year to year, an onion crop should only be grown on land free from pink root. 5. With no alternative, and when onions must be grown on sick soil, the land should receive liberal applications of quickly acting fer~ *Here seed means not the dry sets or bulbs, but true seed resulting from the fertilization of blossoms. 42 TEXAS AGRICULTURAL EXPERIMENT STATION. tilizer so as to encourage and maintain vigorous growth and a rapid development of root system. No one fertilizer will suit all soils and conditions. In general, the soils of the Bio Grande Valley, Where onions are grown extensively, lack humus. Hence, it XVlll be desirable for each grower to apply plenty of well rotted manure, or plow under cover crops so as to increase materially the supply of organic matter. A11 analysis of the soil will also assist one to select the proper commercial fertilizer intelligently. i 6. Badly infected pink root soils should not be used for onion cul- i ture. Such lands should be given a rest from onions, by adopting a four-year rotation in which onions, shallots, and garlic are omitted. 7. In dealing with healthy and pink-root infected soils on the same farm, the grower should not use the same set of tools 011 both. S. Everything should be done to avoid a check in the growth of an onion crop. 9. As far as possible, soils low in organic matter, and hence in a poor physical condition, should not be planted to onions until they are built up and their physical condition properly developed. 10. Planting of onion seed should be done not too early in the fall while the soil and climate is still hot and favorable for pink-root de- velopinent in the seedlings. Neither should seeding and transplanting be so late as to force the crop to bulb and mature during the hot Weather of spring, especially during May. Any severe check, or stunting of the plants during the growth and development of the crop Will be favor- able to more serious pink~root infection. 11. It is especially advisable to avoid late planting of fields known to be infected with pink root. Transplanting of green sets in the field should be followed immediately by an irrigation so as to avoid delay in the development of new roots and new growth. Any such delay will favor pink root getting the upper hand. 12. No fertilizer, or alkali, is directly the cause of pink root. Un- favorable soil conditions may Weaken the plants and make them more susceptible to the disease. A CKNO\VLEDG1\1 LIN TS The authors desire to acknowledge especially their obligation to the demonstrators, Steve Simon, Geo. W. Derby, and L. J. Christen of Laredo, Texas, who assigned suitable blocks of their farms for experi- mental and demonstration purposes. Except for their liberality in the assignment of the use of tools, necessary labor, and other minor local expenses, as well as for their hearty cooperation, it would have been ini- possible to conduct the field trials upon anything like an adequate basis. To the lilarrett Company we acknowledge the donation of the liberal amounts of Arcadian brand of sulphate of ammonia for the tests. Perth Amboy‘ Chemical Company donated the necessary supply of formaldehyde for the extensive field tests.‘ We further acknewrlcclge the donation of an ample supply of cyanamid by the Cyanamid lilanufacturing Company. Finally, the Armour Company donated sufficient quantities of both sulphate and muriate of potash, to make the chain of tests complete, at a time when ‘it was practically impossible to secure these elements.