TEXASAGRIBIJLTIJRAL rxrnnmrnr fifféiiifiqdmo B. YOUNGBLOOD, DIRECTOR COLLEGE STATION, BRAZOS ‘COUNTY, TEXAS JULY, 1926 BULLETIN NO. 343 DIVISION OF PLANT PATHOLOGY AND PHYSIOLOGY STUDIES OF A NEW’ FUSARIUM WILT OF SPINACH IN TEXAS o a 0 0 I Q Q 0 co 4 PM: ,3 p ivJ , . \ Q Q no =1 4 nWHIIrHI/no hlflmuhwu. A ,1 I: . ‘ A , IMWWHUA . IUrUUMlJ/I/lw. ‘if AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. WALTON, Preside_nt STATION STAFFT ADMINISTRATION: ' B. YoUNcBLooD, M. S., Ph. D., Director A. B. CoNNER, M. S., Vice-Director R. E. KARPER, B. S., Assistant Director A. S. WARE, Secretary M. P. HoLLEiviAN, JR., Chief Clerk J. K. FRANCKLOW, Assistant CfiiefC/erk J. M. SciiAEDEL,Executive Assistant C. B. N EBLETTE, Technical Assistant VETERINARY SCIENCE: _ *M. FRANcis, D. V. M., Chief_ _ H. SCHMIDT, D. V. M., Veterinarian W. L. BLACK, D. V. 1W Veterinarian CHEMISTRY: G. S. FRAPS, Ph. D., Chief; State Chemist S. E. ASBURY, M. S., Assistant Chemist WALDO H. WALKER, Assistant Chemist J. K. BLUM, B. S., Assistant Chemist J. E. TEAGUE, B. S., Assistant Chemist VELMA GRAHAM, Assistant Chemist ADAH E. PROCTOR, B. S., Assistant Chemist N. J. VoLK, M. S., Assistant Chemist E. C. CARLYLE, B. S., Assistant Chemist R. O. BRooKE, M. S., Assistant Chemist HORTICULTURE: W. B. LANHAM, M. A., Chief H. N Ess, M. S., Berry Breeder RANGE ANIMAL HUSBANDRY: J. M. JoNEs, A. M., Chief; Sheep and Goa Investigations J. L. LUSH, Ph. D., Animal Husbandman; Breeding Investigations FRANK GRAYsoN, Wool Grader ENTOMOLOGY: F. L. TrioiviAs, Ph. D., Chief; State Entomologist _ H. J. REiNnARD, B. S., Entomologist W. L. OWEN, JR., M. S., Entomologist S. E. McGREGoR, JR., Acting Chief Foulbrood Inspector GILLis GRAHAM, Apiary Inspector OTTo MAcKENsEN, Foulbrood Inspector AGRONOMY: E. B. REYNQLDs, M. S., Chief F, ])_ F - A. B. CoNNER, M-. S., Agronomist; Grain S. D. PEJARgE" Selcrgtarghlef Sorghum Research _ _ J_ H_ ROGERS’ Feed Ins “for R. ERKARPIZR, B. S., Agronomist; Small Grain W. H. W0oD ’Feed Insppigctop esearc K_ L_ K ’ . D. T. Kgmouan M. S., Agronomist; Cotton ‘W. D. légg¥gggiwéfi§£ gag Ig-‘igfidlogspe HBT“ ‘f’? B S A . . C V. C. GLASS, B. S., Feed Inspector ' R. . STANSEL, . ., ssistant in rops E. H. GARRETT, Feed jnspedo, SUBSTATION S No. 1, Beeville, Bee County: R. A. HALL, B. S., Superintendent No. 2, Troup, Smith County: W. S. HOTCHKISS, Superintendent No. 3. Angleton, Brazoria County: V. E. HAFNER, B. S., Superintendent No. 4, Beaumont, Jeflerson County: H. WYCHE, B. S., Superintendent No. 5, Temple, Bell County: H. E. REA, B. S., Superintendent No. Denton, Denton County: P DUNKLE, B. S., Superintendent 6, . B. No. 7, Spur, Dickens County: . E. DICKSON, B. S., Superintendent No. 8, Lubbock, Lubbock County: D. L. JoNEs, Superintendent FRANK GAiNEs, Irrigationist and Forest Nurseryman No. 9, Balmorhea, Reeves County: A J. J. BAYLEs, B. S., Superintendent Teachers in the School of Agriculture Carrying Cooperative Projects on the Station: . ADRiANcE, M. S., Associate Professor of Horticulture . BILSING, Ph. D., Professor of Entomology _ D., Professor of Agricultural Economics . GROUT, M. S., Professor of Dairy Husbandry _ . LEE, Ph. D., Professor of Agricultural Economics M ., Assistant Professor of Agronomy. Sc0ATEs, A. E. Professor of Agricultural Engineering _ _ P. Smith, B. S. Associate Professor of Agricultural Engineering W W A. BUECHEL, Ph. P P O G S. F. G. V. E. . POLLOCK, A. D. H. TAs of June 30, 1926._ _ _ *Dean, School of Veterinary Medicine. **In cooperation with SOIL SURVEY: _** U. S. Department of Agriculture. ***In cooperation with the School of Agriculture. PLANT PATHOLOGY AND P J. J. TAuEENnAvs, Ph. D., Ch HYsioi. . ief P FARM AND RANCH ECONOMICS: L. P. GABBARD, M. ., Chie B. Yowvazazooa M S., P . D., Farm: Ranch Economist. . G. L. CRAWFORD, M. S., Research Mar I Specialist . V. L. CORY, M. S., Grazing Research Bot **T. L. GAsToN, JR., S., Assistant, F, Records and Accounts **J. N TATE, B. S., Assistant, Ranch and Accounts " W. T. CARTER, B. S., Chief H. W. HAWKER, Soil Surveyor E. H. TEMPLiN, B. S., Soil Surveyor T. C. REiTcR, B. S., Soil Surveyor BOTANY: H. NEss, M. S , Chief PUBLICATIONS: A. D. JAcKsoN, Chief . SWINE HUSBANDRY: FRED HALE, M. S., Chief DAIRY HUSBANDRY: '_'—————-—-——, Chief POULTRY HUSBANDRY: R. M. SHERWOOD, M. S., Chief ***AGRICULTURAL ENGINEERING: MAIN STATION FARM: G. T. McNEss, Superintendent APICULTURAL RESEARCH LABORATORIES (San Antonio) 1* . - B- PARKS, B- 45“ Apiculturist in Charge; E A- H- ALEX, B- $-. Queen Breeder FEED CONTROL SERVICE: N°- l9» Feeding d B - - College Statioaiil,‘ BraéfigdCuiiigmtsyitzatlon’ IQ‘ SiiERwooD, M. S., Animal H, L man in Charge of Fqrm_ , _ . J . McCALL, Farm Superintendent N°- 11» Nacogdlwhes, Nacogdoches County’? A H. F. Monnrs, M S., Superintendent **No. l2, Chillicothe, Hardeman Cou t ' ‘kad- R- QUINBY, B- 3-. Superintendent“ y . C. STEPHENS, M. A., Junior Agronomist ‘ No. 14, Sonora, Sutton-Edwards Counties: E- W. THOMAS, B. S., Superintendent - D- H. BENNETT, D. V. M., Veterinarian V. L. CoRY, M. S., Grazin Research Botan **0- G- BABCOCK, B. S., Co laborating ' Entomologist a . L. CARPENTER, Shepherd No. 15, Weslaco, Hidalgo County: W. H. FRIEND, B. S., Superintendent No. 16, Iowa Park, Wichita County: E. J . WiLsoN, B. S., Superintendent ‘s 3 Www-‘wwvr "1\"'x*\' Y"wv"vfit—"lf'. ww“ x~wywwwm~ww , , . . . observation for several years. SYNOPSIS Spinach is an important truck crop in Texas, and is grown mostly as a winter crop. A new spinach wilt has been under This trouble causes serious 3 losses, especially on spinach which matures during the late spring or early summer. , occurring in Idaho. s», Atfirst it was thought that this disease as it aifects spinach in Texas was the same as the one However, as indicated in this Bulletin, this disease was found to be hitherto undescribed, and is caused by a fungus, Fusarium solani, which is commonly found on decayed tubers of Irish potatoes. I was definitely established by inoculating healthy spinach with pure cultures of Fusarium solani from spinach and Irish pota- ' toes. * ship to soil temperatures, becoming worse as the temperatures The cause of the disease It was shown that this disease has a definite relation- of the air and soil increase. The causal organism was studied 7 and comparisons were made with the Fusarium spinaciae f which causes a spinach wilt in Idaho. =» were found to _be distinct, and both pathogenic to spinach. The two organisms Practically all varieties of spinach are susceptible to this wilt i except the New Zealand spinach, which was found to be wholly resistant not only to wilt but also to high temperatures and is, therefore, well adapted to summer weather conditions. Con- trol methods would consist in not planting this crop on land previously devoted to spinach or Irish potatoes, but if possible to have it follow some graminaceous crop. CONTENTS i PAG__ Introduction . . . . . .' . . . . . . . . . . . . . . . . . . . .1 . . . . . . . . . . . . . . . . . . . . .p ' Distribution of the disease in Texas . . . . . . . . . . . . . . . . . . . . . . . i. . . . . i! Economic importance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. a Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Parts of the plant affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Evidences that Fusarium solani is the cause of the disease. . ._ . . . . . . Physiology of the causal organism . . . . . . . Q. . . . . . . ..- . . . . . . . . . . .. Susceptibility of different varieties of spinach . . . . . . . . . . . . . . . . . .. 1' l: Effect of temperature on spinach wilt. . . . . '. ». . . . . . . . . . ; . . . . . . . . . 1 Rhizoctonia associated with Fusarium Wilt . . . . . . . . . . . . . .' . . . . . . Methods of control . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q . . . . . . . . . . . . Summary . . . . . . . . . .’ . . . . . . . . . . . . . . . . . . . . . . . . Q . . . . . . . . . . . Acknowledgment . ._ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ‘. . . . . . . 23F References . . . . . . . . . . . . . . . . t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . BULLETIN N0. 343 JULY, 1926 STUDIES OF A NEW FIJSARIUM WILT OF SPINACH IN TEXAS BY J. J. TAUBENHAUS INTRODUCTION For the last five years the writer has studied a serious disease of spinach as it occurs in many parts of Texas. The trouble was first found by the writer in 1921 at College Station. Cultures made from roots of infected plants yielded in nearly every case a pure culture of a Fusarium. Hungerford (2) in 1923 called attention t0 a Fu- sarium wilt of spinach in Idaho. He submitted the organism to Dr. Sherbakoif, who pronounced it a new species of Fusarium, which he named Fusarium spinaciae. In 1924 the author ('7) made brief men- tion of the spinach wilt as it occurs in Texas. The present bulletin _ sets forth the results of our studies on this disease, which was found to be different from the one occurring in Idaho. DISTRIBUTION OF THE DISEASE IN TEXAS After this new disease had been found on spinach grown at College Station, a careful survey by the writer revealed its presence in numer- ous parts of Brazos County, where spinach is generally grown on a small scale in home gardens. It was also found in East Texas, notably in Smith County in the vicinity of Tyler, and in Cherokee County around Jacksonville and Alto. The disease was also found in abun- dance in the spinach districts of South Texas around San Antonio, Laredo, Dilley, Carrizo Springs, Crystal City, Big Wells, Asherton, Eagle Pass, and in the lower Bio Grande Valley in the vicinities of Harlingen, Mercedes, Weslaco, Edinburg, McAllen, Pharr, Browns- ville, and around Corpus Christi and Robstown. It is probably preva- lent wherever spinach is grown in Texas and possibly in other spinach- growing states. ECONOMIC IMPORTANCE The main commercial spinach crop of Texas is grown in South Texas. The seed is sown in the early and late fall and the crop harvested from January to the latter part of March. This is of interest on account of the fact that the disease does not seem to cause severe damage on early spinach. The economic importance of the disease is shown by estimates made by the writer which place the losses from Fusarium wilt at 2 to 10 per cent of the early crop, and 20 to 70 per cent of the late plantings. The disease has been found on virgin- land on all types of soils. However, the greatest damage occurs on old land devoted to spinach for a succession of years. 6 ' BULLETIN NO. 343, TEXAS AGRICULTURAL EXPERIMENT STATION SYMPTOMS The disease is very characteristic and resembles a typical wilt. i,‘ fected plants first attract attention by their stunted and dwarfed co’ dition. As the season advances, such plants turn pale, the lower leav wilt, and gradually die.‘ Affected plants may be readily pulled on from the ground without much difiiculty. The roots of such plants : of a pale dead color accompanied by a loss in turgor. When cut Ht? crosswise or lengthwise the interior tissue appears brown in color. a, The spread of the disease becomes more pronounced with the -.1 proach of warm weather, when the soil temperature rises. At tha time healthy, vigorous plants suddenly become infected and wilt. Th" will be referred to later. I The Fusarium wilt of spinach is frequently mistakeii by growers f0 damage caused by the onion maggot. With the latter, however, thf chief injury is in the center of the plant though the outside leav i turn yellow and may even wilt. By cutting into such affected plants one or more maggots may be found in the rotted center. Not infre quently the maggot injury opens the way to infection by Fusari 44' wilt. In Texas, spinach is also found to be attacked by a Rhizoctoni which causes numerous deep, dark lesions on the roots, and this resulwl 1n a. stunting of the plant. Like maggot injury, Rhizoctonia root ro frequently opens the way to infection by Fusarium Wilt, thus mate’ rially shortening the life of the plant. 3? Table 1. Isolations from Field-Infected Spinach. Number of Percentage Pathogenicity‘ Source of Infected Date Parts of Plant Plate of Plates of Fusarium, Spinach Cultured Cultures Showing Established 7 ade Fusarium ’ College Station, Texas April 28 , 1924 Roots . . . . . . . 298 94 Yes, on spinac " College Station, Texas April 29 , 1924 Leaf petioles. 115 ,3 - College Station, Texas April 29 , 1924 Leaf veins. . . 49 0 ’ College Station, Texas June 16, 1924 Seed stalks. . 98 0 ? College Station, Texas April 30, 1925 Roots . . . . . . 70 9O Yes, on spinach Colle e Station, Texas April 30, 1925 Leaf petioles. 72 0 3 Lare o, Texas._ . . . . .. May 2, 1924 Roots . . . . . .. 207 98 Yes, on spinach; Laredo, Texas . . . . . . . . May 3, 1924 Leaf petioles. 93 0 r . Laredo, Texas. . . . . . . May 3 , 1924 Leaf veins. . . 57 0 _ < Crystal City, Texas. . April 26, 1924 Roots. . . . . 206 80 Yes, on spinach“ Crystal City, Texas. . April 27 , 1924 Leaf petio‘es. 105 O _ Crystal City, Texas. . April 27, 1924 Leaf veins. .. 97 O PARTS OF PLANT AFFECTED To determine the parts of the plant affected, diseased spinach plants‘ were secured from three separate sections of this State, namely, Col-i lege Station, Laredo, and Crystal City. Cultures were made from the‘ roots, petioles, leaves, leaf veins, and seed stalks. The method of iso-T lation was as follows: Affected material was thoroughly washed in running tap water to remove adhering particles of soil, and then cut‘. up into small pieces about one-eighth of an inch in length. These were then dropped in a test tube and immersed one-half to one minute ; STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXAS Figure 1. a. Early infected plants as they are commonly met with in the field showing wilting and stunted condition. b. Normal healthy plant of same age for comparison. c. Mature spinach plants suddenly wilting and show- ing collapsed condition. d. Two branches of New Zealand spinach, which is wholly resistant to the wilt disease. e. Practically a pure culture of Fusarium solan/L isolated from roots of infected spinach grown in the field. g. Spinach seedlings artificially infected with Fusarium solaml showing wilting. f. Practically a pure culture of Fusarium solam‘ recovered from artificially infected seed- lings shown in g. I 8 BULLETIN NO. 343, TEXAS AGRICULTURAL EXPERIMENT STATION in a solution made up of equal parts of 111000 mercuric chloride and 50 per cent alcohol. The material was rinsed five times in sterile water to remove all traces of the disinfectant. Individual pieces of the tissue were taken out aseptically, placed in a tube which contained i melted but properly cooled agar, and crushed with sterile forceps. The agar containing the crushed tissue was poured from the tube into a sterile Petri dish. In order to keep out contamination from bacteria, a drop of a 5 per cent lactic acid was added to each Petri dish. As soon as growth appeared transfers were made to slants of agar tubes and the resulting pure growth was used for inoculation or study. It is seen in Table 1 that the causal organism was recovered from the roots only of affected spinach plants. This was true not only of speci- mens secured locally, but also from other parts of Texas. From this it would seem that in Texas the Fusarium wilt of spinach is entirely a root trouble. Hungerford (2) does not state whether in Idaho spinach wilt infects any of the parts of the plant above ground, although he points out that Fztsarium sp/inaciae is an organism which invades the vascular system of the spinach root. The Fusarium here described, on the other hand, is found to invade not only the vascular bundles but other tissues of the root as well. A further study of the Texas spinach Fusarium brought out the fact that it is identical with F. solani. b EVIDENCES THAT FUSARIUM SOLANI IS THE CAUSE OF THE DISEASE In order to determine the pathogenicity of ~ this organism, pure cul- tures were secured from infected spinach grown in various parts of Texas. Likewise, a tube culture of F. sola-ni from decayed Irish pota- toes was secured from Dr. Sherbakoff from Tennessee and a tube cul- ture of F. sprinaciae from Professor Hungerford from Idaho. These strains were tested as to their pathogenicity on spinach. The method of inoculation was as follows: 8-inch pots were filled with a good sandy loam. The pots and soil were sterilized for four hours at 20 pounds steam pressure. After properly cooling, the soil in the pots was. in- oculated with a ten-day tube culture of Fusarium, which grew in tube slants of oatmeal agar. The entire content of the tube was broken cup in sterilized water and worked in the soil in the pot, and allowed to stand undisturbed for one week. This was intended to permit the organism to grow and thoroughly invade the inoculated soil, which. was then planted with spinach seed. After germination, the spinach plants were watched for the appearance of disease, and the causal organism recovered from the plants. Checks were also used in which the pots and soil were sterilized but not inoculated with any organism. From Table 2 it is seen that whenever Fusarvium salami is isolated from spinach roots it is pathogenic. to spinach. The symptoms of the arti- ficially infected plants appeared identical with those of naturally in- fected spinach. Table 2 further indicates that Fusav-"ium solan/i ob- . tained from I-rish potatoes from Tennessee waslikewise pathogenic to spinach. From these experiments it is evident that Fusarmm solaml is the cause of the spinach wilt disease in Texas. STUDIES OF A NEW FUSARIUM WIILT OF SPINACH IN TEXAS Figure 2. a. Spinach seedlings artificially infected with Fusarium sp/maciae from Idaho. b. Healthy check, uninoculated. c. Spinach seedlings artificially inoculated with Fusarium ' salami from spinach. d. Check, healthy, uninoculated. f. Spinach seedlings artificially inoculated with Fusar/ium solam’ from decayed tubers of Irish potatoes from Idaho. e. Check, healthy, uninoculated. g. Portion of spinach ’ root artificially inoculated with Fitsar/iuon sp/inaciae from Idaho, planted in a Petri dish of agar agar and showing Fusarium growth. h. Two sections of spinach roots arti- ficially inoculated with Fusar/iuwz salami from spinach planted in Petri plates of agar agar showing Fusarium growth. i. Young Petri dish culture of Fusarium solaml from spinach grown on potato agar and showing radial growth. J. 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Results of these inoculations are shown in Fig. 2, a-h. Fusarium salami, according to Sherbakoff (6), is usually found on 1% otted potato tubers and on decaying organic matter. It is surprising, i" erefore, to find that this organism is pathogenic to spinach. In a f nversation with Dr. Shcrbakoff, the writer understood him to say at he found Fusafium solaml to be parasitic on plants other than the 'sh potato. _ In addition to establishing the pathogenicity of Fusarium salami as h spinach and Irishpotatoes, it was also necessary to determine the ‘rulency of these organisms on potato tubers. From Table 3, it is vident that Fusarium solaml, whether isolated from spinach or from 'sh potatoes, is pathogenic to Southern spring-grown Irish potatoes. ‘ owever, infection was rather slight when inoculations were made on orthern-grown winter varieties. s N 0 I T A T S T N E M I R E P X E L A R U T L U C I R G A S . 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Mo oo5ow .53:oo5~ Mo ooooom Mo ooofl Ho oon5sz doooooom GO muofifiooofli .m oEmP PHYSIOLOGY OF THE CAUSAL ORGANISM _~ To determine the possible relationship or differences between Fusarium lam} and Fusarium spinacwiae, the two organisms were grown on a iety of media in both Petri dishes and Erlenmeyer flasks. Best re- _» were obtained with potato starch agar, steamed rice, and corn meal. was found that Fusariam salainl from Texas spinach and Fusarium y ani from decayed tubers from Tennessee were practically identical on . media grown, but were distinct from Fasarlum spvinaciae. On tatoi starch agar in Erlenmeyer flasks, Fusariuim sp/inaciae makes a _» t, shiny, superficial growth with no discoloration of the substrata and ssesses a strong fermenting odor (Figure 3, a). On the other hand, , amium salami makes a restricted, fluffy growth, with distinct browning i, the substrata and no odor of fermentation. Similar conditions were :| found on corn meal (Figure 3, b). When grown in Petri dishes ' soft potato agar, FUSLLTTiUT/l salami from Texas spinach and Fasarium mi from decayed potatoes are very much alike; that is, growth is ial and raised, whereas the Fusaflum spinaciae growth is flat, a haps the greatest differences appear when these organisms are grown Petri dishes on hard potato agar. Here Fasarium salami from Texas _'ach and Fusarium salami from decayed Irish potatoes are distinctly ‘al. With age, Fasarlam salami from decayed potatoes produces 7 do-pionnotes in concentric rings, which did not appear ‘in F. salani i Texas spinach (Figure 3, d). But this slight difference is not i1 sidered by the writer to be of sufficient justification to consider the arium affecting Texas spinach a new variety of F. salami. On the er hand, Fusarium- s-pinaciae on hard potato agar in Petri dishes 'tains its flat, glossy characteristic growth (Figure 3, d). In ble 4, the salient differences of Fusar/ium salami and F. spinaciae are L" arized. In this table it is seen that both F. salami and F. spirzaciae Fe microconidia, the latter being slightly larger in F. solani. The roconidia in both organisms are mostly three septate, but these comparatively shorter in F. salani. Furthermore, chlamydospores F. salami are from one to three septate and rough-surfaced, whereas F. spinaciae they are slightly smaller, smooth and mostly zero septate. 'ther F. salami nor F. splna-ciaa were found to produce sclerotia on ' many media tried. Pionnotes are formed by F. salami and none ' I F. splnaciae. Sporodochia are formed on both organisms, although y are slightly larger in F. salami. As already stated, perhaps the test distinguishing characteristic between the two is the whitish or ' ' cream, glossy, shiny growth of Fusarium sp/inamae as contrasted i! the superficial, raised, fluffy, white to olive, buff, greenish, blue of Fusariam salani. In addition, F. spinaaiae is characterized by , ong odor of fermentation on various starchy media and this is not ‘I; case with F. salani. STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXAS 13X. ricted, glossy to dirty cream color (Figure 3, c, lower three plates). _ 14 BULLETIN N0. 343, TEXAS AGRICULTURAL EXPERIMENT STATION Figure 3. a. To right, Fusczriwm spinaciae on potato starch. To - ° left, Fusarium solam‘ from spinach on potato starch. b. To right, Fusarium. solani from spinach on corn meal. To left, Fusarium spinaciae on corn meal. c. Top row, to l; right, one plateFusarium spinaciae on potato agar. To left, two plates of FlLSCZTiQLTH solaml from spinach on potato Q53 agar. Bottom row, to right, one plate Fusarium spinaciae on rice agar. To left, two plates Fusarium solani fro-m “ spinach on rice agar. d. To right, one plate Fusarium salami from spinach on hard potato agar. Center plate, Fusarium salami from decayed Irish potatoes on hard potato agar. To left, one plate Fusarium spinaci-ae on hard potato agar. STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXA-S 15 Table 4. Salient Differences Between Fusarium solani and F. spinaciae. I _ . ‘ F usarium solqni from Fusarium spingzciae from Characteristics . .Texas Spinach Idaho Spinach Always present, zero septate 8123- Always pr sent, zero septate 10.5 u. 7.5x — .4 u. F. croconidia " Mostly 3 septate, comparatively Mostly _3 septate, 27—45x4.5x6.4u short 27—I_34_x5.4-5.8 u, slightly or pedlcillate, apex broader, but not edicillate, rounded to abruptly constricted, 4 to 5 slighty constricted at apex, 4r septate infrequent to rare. septate not very prevalent, septate rare. I 3: croconidia i‘ amydospores 1-3 septate 5-11 u, terminal or Mostly zero septate, mostly intercalary, rough surfaced. smooth, 5.5—18.6 u. erotia None None ' nnotes Numerous, bluish None yrodochia Frequent, larger than in F. spinaciae. Small, whitish, and scarce to rare. or of mycelium White to olive, buff to greenish blue. In media, without su ar, white_to L ' s _ dirty cream, or g ossy. With sugar occasionally light lilac. yr of fermentation None On potato plugs, rice. SCEPTIBILITY OF DIFFERENT VARIETIES OF SPINACH Under field conditions practically every variety of spinach grown is ject to Fusarium wilt. On the other hand, there seems to e-xist cient evidence of individual resistance. Where the disease is very valent, one notices healthy individuals growing here and there next many others which have died from the wilt. This resistance is espe- pf ly, apparent in the late season when the greatest number of the f ts die as a result of the disease. No attempt was made to carry any selection of these resistant individuals, although there seems to , great promise in that direction. In order to definitely determine the p eptibility or resistance of various spinach varieties to the wilt dis- seeds of as many varieties as could be secured were planted on _ y infected land in the writefs home garden. The varieties tested as follows: King of Denmark, Bloomsdale Savoy, Victoria, Im- ived Thick Leaved (Virofiay), and Long Season. None of these vari- is, however, showed any more resistance than the other. On the er hand, New Zealand spinach (Tetragonia expansa) proved to be pletely resistant. However, New Zealand spinach (Figure 1, d) is a true spinach. New Zealand spinach is grown by truckers and sold Ilocal markets in Texas. It is resistant not only to the Fusarium t, but it can also withstand a great dealof hot weather. EFFECT OF TEMPERATURE ON SPINACH WILT t is generally conceded that soil temperature is an important factor either favoring or retarding the spread of certain plant diseases, the 'al organism of which is soil-inhabiting. This has been demon- 16 BULLETIN NO. 343, TEXAS AGRICULTURAL EXPERIMENT STATION ‘,4 4‘ rmuxfix-h 14$. Figure 4. a. Spring-grown Irish potatoes artificially inoculated with Fwsarium salami from spinach. b. Spring-grown Irish potatoes artificially inoculated with Fusarium salami from decayed tubers of Irish potatoes from Tennessee.- c. Spring-grown Irish potatoes inoculated with Fusarium spinaciae but remaining healthy. d. Spring-grown Irish potatoes inoculated with Fusarium solani from decayed Irish potatoes from Virginia. l’ srunrns OF A NEW FUSARIUM WILT OF SPINACH IN TEXAS 17 by Gilman (1), Jones (<1, 5), Johnson and Hartman (3), and others. We have already mentioned the fact that the Fusarium pf spinach is more prevalent on late- than on early-planted spinach. undoubtedly is due to the fact that the later plantings mature at ie of higher soil temperatures. In order to determine this more ‘itely, the outdoor temperatures of the soil of infected spinach land fistudied. Soil temperature studies were made in the W1'iter’s gar- fhere spinach was known to suffer very badly from wilt. One ther- i" was used to study the temperature of the air and two others installed at depths ranging from two to four inches. Temperature a- were taken three times a day, namely, 7:00 a. m., 12:00 m, I; :00 p. m. A careful check was also kept of the daily percentage t, and records of the daily precipitation were secured from the ' on of Entomology of the Texas Experiment Station. The spinach lanted in the middle of February and the soil temperature “read- 5 and Figure 6 clearly show that the rise in percentage of spinach es hand in hand with a corresponding rise in both the air and » u peratures. p ' interesting to note that in Webb County and in the Winter J District of Texas where spinach is grown on a commercial scale, ‘ p is planted during the fall months and harvested during the spring. The later plantings are those to show greater losses from It appears from this that soil temperature is an important factor _ spread of the spinach wilt in Texas. ygan March 18, 1925, and continued during April, May, and June. . 8 ma. _ w . 8 up mm m . a.» ow m3 w . mm w» o: 2.3. 3 NT w . E. mm 8 w .3 wm 3 w. 3 mm w“: >22 m 3 . ~ m. E. 3 8 m . R S wm w . w.» 3 wm =S< _ mm. fi m . 3 mm 5 w . o» mm ww m . m» ww aw .382 mvnfii GNQE EUEWGWE Eiamflflz smog EBEMQME 858352 G502 EDEWGM: EDEMMQE fir’? c223 mwflcown 135.2 IIIIIIII >EE¢2 wnoU pom wirooam moiofixm moiobxfl noiofixmm ficow/H > o 2:82 5E E @235 w 8:2: m kooBso \‘ I T A T S T N E M I R E P X E L A R U T L U C I R G A S A X E T 3 4 3 O N N I T E L L U B 18. 6N2 5.53m owv=oU .315 Esimgm mo vwwwnouhom 3 vu-ZQHQQEQH» mow Mo soflfiom .m 05mm. STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXA§ 19 Figure 5. a. Macrospores of Fusarium solam‘, from spinach. ‘ b, c, and d. Chlamydospores of Fusarium salami from spinach. k. Microspores of Fusarium solani from spinach. e. Macrospores of Fusarmm spinaciae. f, g, and h. Chlamydospores of Fusarium spinaciae. i and j. Mycelium of spinach Rhizoctonia. 20 BULLETIIN NO. 343, TEXAS ‘AGRICULTURAL EXPERIMENT STATION‘, ,".;$"...;' ‘n “n” ‘ ""1 l"! am gnwrzcg: f» 3“ an / . 1o _ / N 2' B" so so so 4" 4n \ an .p _ . 3|, ~20 ' m 1|! / m __--4 —0-—O—-O-—O—Q—o— 01mm’ 3 1N1"! 4 ma" Mr out dluuod Figure 6. Graph showing the relationship of average, mean out- floor temperature and soil temperatures 0t two and tour inches depth for March, April, May, and June, 1925, and the relationio the percentage of Fusarium wilt during these months. STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXAS 21 RHIZOCTONIA ASSOCIATED WITH FUSARIUM WILT our studies of the Fusarium wilt of spinach we frequently found “zoctonia root rot disease more 0r less serious. This trouble was yifested by typical cankered lesions, which were confined to the foot he plant or its roots. In many cases the Rhizoctonia was associated . Tl the Fusarium wilt. In other cases it was found independent of ‘t disease. In either case, the Rhizoctonia was found to cripple seri- ly the root system and to inhibit the normal development of the u No studies were made to compare the Rhizoctonia of spinach f‘: the same organism as it occurs on the Irish potato. Comparative w 'es were made of the spinach Rhizoctonia and a species of Rhizoctonia ted from cotton seedlings affected with sore shin. When grown sterilized rice the spinach Rhizoctonia was found to penetrate and ow within the entire substratum, coloring it a distinct light brown. ythe other hand, the cotton Rhizoctonia was found to grow super- lly and did not color the substratum. Whether or not We are jus- ,d' in considering both the spinach and cotton Rhizoctonia distinct n each other and from the Rhizoctonia of potatoes remains to be Imined. At present, the spinach Rhizoctonia is mentioned only .~= use of its importance in causing a serious root trouble and because its opening the way to infection by Fusarium wilt. n order to determine the pathogenicity of the spinach Rhizoctonia, Tl. seeds were planted in pots and inoculations carried out as for spinach Fusarium previously discussed. In referring to Table 6, be seen that the spinach Rhizoctonia is highly pathogenic, as it ;-= 100 per cent infection every time it wasinoculated into steril-. ' soil. Table 6. Rhizoctonia Inoculation on Spinach. _ Per Cent ‘ Number Germination Date and Per Cent 1 Date of Inoculation of Pots of Spinach of Infection Inoculated Seed i" l 11, 1924 8 93 April 15, 1924. 100 i . No inoculation 4 10o April 1s, 1924. All healthy. 3, 1924 6 84 November 15, 1924. 100 . No inoculation 3 99 Nov. 15, 1924. All healthy. p METHODS OF CONTROL definite methods of control have been worked out for either the arium wilt or Rhizoctonia root rot of spinach. The growing com- }'ci.a1 importance of spinach now demands attention to this problem. as already been pointed out that the Fusarium wilt, especially, is _i e prevalent and serious on late-planted spinach; hence the chief meth- or spinach growers is to plant early enough to avoid the high soil tem- fcures. Frequently, however, late-planted spinach brings as good a 22 BULLETIN NO. 343, TEXAS AGRICULTURAL EXPERIMENT STATION price or ev-en better than early-planted spinach. Late—planted sp' crop should not be planted 0n newly cleared land or land previousl. voted to Irish potatoes. It would seem advisable to plant late spina South Texas after corn or sorghum. Furthermore, late-planted sp' should be given all possible care, especially in irrigation to prevent, setback, which favors infection. ' _. SUMMARY In 1921, a new spinach wilt was first found and reported by the " ‘a at College Station, Texas. In 1923, Hungerford (2) reported a ‘ spinach wilt in Idaho. Studies were made with a view of determl the cause of the spinach wilt in Texas and its possible identity ~- that of Idaho. A summary of our studies brings out the follof salient features: 1. Spinach wilt in Texas is caused by the fungus Fusarium so‘ which is ordinarily found on decayed tubers of Irish potatoes and i causes decay of spring-grown Irish potatoes. f 2. The spinach wilt of Texas, although apparently similar in' pearance to that of the Idaho spinach wilt, was found to be dis n? from the latter, and prevalent in many parts of the State. ' 3. The disease is less severe on winter-grown spinach, but n‘ serious on spinach planted in the early spring or late summer. 4. The symptoms of the spinach wilt are typical of a Fusari He. which the causal organism is confined to the root. Where infe occurs early, plants remain stunted and dwarfed. When older pl become affected, they seldom recover, but generally die within a days. Frequently this disease may be mistaken for injury bro _ about by root maggots. Q 5. The causal organism of spinach wilt is confined to the ri We have never been able to isolate the causal organism from anyp of the leaves, stems, or seed stalks. 1 6. Fusarium solani from Texas and Fusarium, spinaciae from a,‘ are both pathogenic to spinach, but the two organisms are very t, ferent when grown in pure culture on media rich in carbohydra All varieties of spinach are subject to spinach wilt in Texas, with: exception of New Zealand spinach, which is not a true spinach. j '7. Soil temperature is an important controlling factor in the sp _‘ of the spinach wilt. Under Central Texas conditions the disease not spread under the average outdoor temperatures of '72 de _ Fahrenheit, or of 70 degrees in the soil at a depth of two inches, 68 degrees in the soil at a depth of four inches. The disease grad increases with the increase of soil temperature above these temperat g ' 8. In connection with the Fusarium wilt, a new Rhizoctonia. _ rot has been found and preliminary studies reported. The Rhizoct‘ causes a serious root rot and it also opens the way to infection . Fusarium wilt. The spinach Rhizoctonia seems to be different f the Rhizoctonia which causes sore shin of cotton in Texas. STUDIES OF A NEW FUSARIUM WILT OF SPINACH IN TEXAS 23 9. Control methods of Fusarium wilt would consist in not planting ‘inach during the months of high soil» temperatures. ACKNOWLEDGMENT 1 The writer wishes to express his indebtedness to Dr. Sherbakoff for 's identification of, our organism, and for a culture of Fmarium ilaml from Tennessee. Thanks are also due to Dr. Leonian for a i» ture of F. solani from Virginia, and to Professor Hungerford for a I ture of F. spinaciae from Idaho. REFERENCES 1. Gilman, J. C. Cabbage yellows and the relation, of temperature its occurrence. In Annals Missouri Botanical Garden, Vol. 3 :25-84=, a 16. ’ 2. Hungerford, Chas. W. A Fusarium wilt of spinach. In Phyto- th. Vol. 13 z205-209, 1923. ' _3. Johnson, J ., and Hartman, R. E. Influence of soil environment ‘the root rot of tobacco. In J ourn. of Agr. Research, Vol. 17 A1486, 119. .4. Jones, L. R. Soil temperatures as a factor in phytopathology. Plant World. Vol. 20z229-237, 1917. . ,5. Jones, L. R. Experimental work on the relation of soil tem- rature to disease in plants. In Transactions Wisc. Acad. of Science, . , Letters, Vol. 20 :433-459, 1922. i‘ .6. Sherbakoff, C. D. Fusaria of potatoes. In New York Agr. pt. Sta. (Ithaca) Mem. 6z97-270, 1915. ,7. Taubenhaus, J. J. Studies on Fusarium wilt of spinach in Texas bstract), In Phytopath. Vol. 14 :29, 1924.