TEXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR College Station. Texas BULLETIN NO. 627 FEBRUARY 1943 COTTONS RESISTANT TO WILT AND ROOT KNOT AND THE EFFECT OF POTASH FER- TILIZER IN EAST TEXAS P. A. YOUNG Division of Plant Pathology and Physiology AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. O. \VALTON, President B31-143-6M-L180 In East Texas sandy-loam fields, Fusarium wilt, nematode root knot, and potash hunger frequently decrease cotton yields to a serious extent. Two or more of these troubles may be associated in the same field and these factors in combination present unusually difficult problems to the grower. As a result of 6 years’ tests in East Texas, the following cotton varieties (listed in decreasing order of‘ probable value) were found to show high resistance to Fwsarium wilt: Coker 4-in-1, Ooker 100 Wilt Resistant Str. 39-5, Delta Dixie W. R. Str. 2, Tifton Dixie Triumph, Dixie Triumph 25-12, Dixie 14-5 Str. 2, Delfos 425, Miller 610, Deltapine 12, and Stonewilt.‘ In addition, (Joker 4-in-1, (Joker 100 W. B» Str. 39-5, and three strains of Dixie varieties were found to be resistant to wilt and root knot together. The Miller 610 variety lost much of its wilt resistance when Toot-knot nematodes were abundant in the same field. In these experiments, wilt resistance usually was lowered when the plants suffered from potash hunger (“rust”), and applications of 24 to 48 pounds of potash per acre increased the wilt resistance of most of the varieties tested. Potash also prevented symptoms of potash hunger, and greatly increased the yields. Phosphate had no apparent effect on wilt resistance of cotton. The experiments indicate that by growing only the varieties of cot- ton that are resistant to the combination of wilt and root knot, by using high-potash balanced fertilizers, and by rotating cotton with Crotalaria and sorghum, farmers can prevent wilt and root knot from becoming a limiting factor in cotton production 0n their farms. COVNTENTS i Page a a Introduction v ' ' 5 fiymptoms of Fusarium wilt M 6 Symptoms of potash hlrnger or “rust” _ - i 8 ‘é Symptoms of _. root knot _ g 9 1 Experimental procedure 9 _ A Controliof wilt by potash fertilizers and resistant varieties ______- 10 i Testing phosphate fertilizers‘ in relation to wilt ______________________ -_ 14f Effects of phosphate and potash fertilizers on yields ----_--___--______- 14 QWilt resistance test ‘at College Station \ 14 s x 7 . Resistance of cotton varieties to root knot ' 16 lejCombined resistance tot wilt“ and root knot,_______._____________-___-____-_--___ 13 ? Methods of disease control _ 23 sLiterature cited 4 _ _ I p 25 i; lv-ryrfiv1 COTTONS RESISTANT TO WILT AND ROOT KNOT AND THE EFFECT OF POTASH FERTILIZER IN EAST TEXAS P. A. Young, Plant Pathologist Division of Plant Pathology and Physiology Wilt, root knot, and potash hunger are closely associated troubles that seriously reduce the yield of cotton in East Texas each year. Many fields that are otherwise desirable are infested with disease-causing fungi and nematodes in such abundance that the land remains unprofitable and uncultivated much of the time. Fusarium wilt alone may kill as much as 50 percent of the plants in many East Texas cotton fields an- nually. Root knot decreases cotton yields usually without killing the plants and is especially destructive in sandy loam fields. Where cotton receives little or no potash fertilizer, potash hunger or “rust” dwarfs the plants and decreases the yields and wilt resistance in many of the sandy fields. On account of their importance, these three disorders of cotton were studied near Jacksonville from 1937 to 1942, and the results are given in this bulletin. The setting of infested tomato or cabbage plants or fruit‘ trees into disease-free fields often introduces root-knot nematodes and other dis- ease-producing organisms. Fields may also become contaminated by in- fested sced, wind, and erosion water. The continued growing of cotton varieties that are susceptible to wilt, and the growing of many crops sus- ceptible to root knot help to increase the causal organisms in the soil so that they greatly decrease the yields of certain crops, and consequently lessen the value of the land. The literature on cotton wilt, root knot, and potash hunger is exten- sive, and the following information is summarized’ mainly from recent references in which many other articles are cited. The statement was made by Neal (10) that wilt is the most destructive disease of cotton in the United States. Young and Tharp (38) concluded that increased severity of potash hunger was associated with increased susceptibility to Fusarium wilt, and that there were large differences in percentages of wilt from year to year. Increases of nitrogen and phosphate ferti- lizer increased wilt, but increased potash fertilizer decreased wilt, ac- cording to Tharp and Wadleigh (27). However, Neal (13) concluded that increasing phosphate fertilizer did not increase wilt or the yield. Tables presented by Ware and Young (30) compare wilt resistance and agronomic quality of many varieties of cotton. Neal and Brown (12) determined that Delfos" 425, Deltapine 12, and Miller 610 had strong resistance to wilt. There is apparently only one physiologic race of Fusarium vastnfelctum according to the data given by Tisdale and Dick (28). Similarly, Sher- bakoff (16) and Cralley (3) determined that dissimilar varieties of cot- ton showed the same relative resistance to the respective isolates of the 6 BULLETIN NO. 627, TEXAS AGRICULTURAL EXPERIMENT STATION wilt fungus, although there was much difference in the virulence o, ferent isolates. Apparently one species of Fusarium caused the w‘ cotton, okra, Cassia, and tobacco in the tests by Armstrong, Hawkins g Bennett (1). 1 Smith (17) gave a general report on the regional cotton varietyl studies, of which the tests at Jacksonville, Texas, were a'part. 5 article stated that wilt decreased the staple length and seed weig the cotton, and that potash fertilizer decreased Wilt. Prelimina ports on the regional cotton variety wilt studies were given by (32, 33, 34, 35). Smith (19) and Smith and Taylor (20) sepa cotton varieties on the basis of their resistance to root knot and s‘ that resistance to root knot was found only in varieties that wer veloped in regions where the disease was severe. Smith (18) concl; that Coker 4-in-1 and Early Wilt varieties were resistant to both and root knot, and that phosphate fertilizer had little effect on wiltf centages. Tisdale and Dick (28) classified cotton varieties on the,’ of wilt susceptibility, andfound that tolerant varieties may give the" yields where the wilt fungus is not very abundant. Studies in Texas by Taubenhaus, Ezekiel, and Killough (21) shop that cotton wilt Was most prevalent in fields with acid soils, while benhaus and Christenson (24) secured evidence that several speci insects were natural carriers of the wilt fungus. Ezekiel and Dul (4) reported the distribution of cotton wilt in Texas in the 1939 s) Concerning root knot, cotton is the sixth most susceptible kin plant as listed by Watson and Goff (31), who regard root knot most destructive disease of crop plants in the old cultivated sandy fig’ of the South. Barker (2), King (7), and Tyler (29) reported that land cotton (Gossypium hirsutum L.) generally tolerates root knot todes, but Sea Island and Egyptian cotton (Gossypium barbadense j are, more susceptible. Sea Island 13B3 cotton had no wilt and on, minimum of root knot according to Miles (9) who compared the ance of cotton varieties to wilt and root knot. Using three resistant", one susceptible variety of cotton, Neal (11) found that all four vari, developed abundant wilt when grown with F. vasinfectum and H. f rioni together. Coker 4-in--1 and Cook 307 varieties survival combil wilt and root-knot attack longer than did the other varieties tested: Taylor, Barker, and Kime (25). Johnson (6) recommended Cook cotton for fields with both the wilt fungus and root-knot nemato Rotation with Velvet beans, bare fallow, oats and bare fallow, Crotalaria decreased tobacco root knot below 1.0 percent, according Shaw (14). King and Hope (8) controlled root knot on cotton by sf l mer fallowing with deep tillage for 3 years. v SYMPTOMS OF FUSARIUM WILT Wilt is caused by a parasitic fungus named Fusarium vasinf ‘ Atk. It enters cotton roots from the soil and grows mainly in the w _ CO'T‘T‘ONS RESISTANT‘ TO‘ WILT AND ROOT‘ KNOT 7 iconducting vessels of the roots and stems, causing the plants to wilt and shed their leaves (Fig. 1). An early symptom of wilt consists of large Syellow or brown areas near the margins of the leaves (Fig. 1). Stunting is another early symptom of wilt affecting some plants, with the stem fnodes (joints) enlarged and the internodes abnormally short. Wilting i, plants more than three inches tall usually show some black or brown rdiscoloration in the woody parts of the roots, leaf petioles, and lower f parts of the stems (Fig. 2). Small plants commonly wilt and die quickly, jbut large plants with wilt may remain alive for many days. In severe "gcases, wilt may kill most of the plants in a field of susceptible cotton (Fig. 5). fig. 1. Early symptoms of Fusarium wilt in cotton. At left, a small stunted plant with wilted leaves growing beside a normal plant. At right, an i affected leaf with withered tip. The dead part of the leaf is brown with a yellowish border. » Fusarium wilt was the only wilt disease involved in this work. An- other kind of cotton wilt, caused by a different fungus (Verticillium), curs locally in neutral or calcareous soils of Central and West Texas. gotton varieties at Jacksonville were not tested for resistance to Verti- illium. However, Ezekiel and Taubenhaus (5) reported that some cot- in varieties resistant to Fusarium wilt are susceptible to Verticillium iWaxahachie) wilt. Taubenhaus, Ezekiel, and Rea (22) showed that intral blackening of cotton stems was an important symptom of Verti- ' illum wilt. ; It is important to distinguish wilt from cotton root rot, caused by i: fungus, Phymatotmlchum omnivorum (Shear) Duggar. In the case é} wilt‘, the bark remains normal on the large roots and on the base of 4e stem until the plant dies. In contrast, root rot soon kills the bark i,» the large roots and base of the st'em and the brown fuzzy strands of the ngus often may be seen on the surface of the bark. The bark becomes ‘gay and decayed, and soil often clings to the dead bark. A reddish- V. d, V. , , W,‘ ‘firs’. I Pig. 2. The most reliable symptom for identifying Fusarium wilt in cotton ll the black or brown streaks in the woody part of the stem. brown discoloration usually may be seen beneath the bark near the mar— gin of infected tissue. the leaves usually remain on the plants for many days. Fields often? show large areas of plants killed by root rot, While plants with Fusariuml: wilt often occur scattered among healthy plants throughout the field. All known cotton varieties are susceptible to root rot. SYMPTOMS OF POTASH HUNGER OR “RUST” When cotton plants suffer from insufficient potassium (designated as ‘ potash in fertilizers) in the soil, the leaves usually develop distinct Plants with root rot commonly die quickly andify; symptoms after the plants are several inches tall. Yellowish-white mot- tling appears, and large yellow spots or irregular areas develop between the veins. sues between the veins and around the margins of the leaves. leaf margins sometimes curl downward. lowed areas of the leaves. early in the summer (Fig. 4). The plant's usually are dwarfed and bear J’ . Many brown spots varying in size develop in the yellowed tis- Breaking f of the browned leaf margins gives the foliage a ragged appearance and the l Black leaf spot caused by the i’ fungus, Macrosporium nigricantium Atk., frequently develops in the yel- Potash hunger causes the leaves to fall off“ OOTTONS RESISTANT" TO‘ WILT AND ROOT KNOT 9 ismall, defective bolls. Plants with serious potash deficiency commonly ilie in July and August, and the yield is seriously decreased. is SYMPTOMS OF ROOT KNOT a‘ l: y Root knot is caused by a parasitic species of nematode Worm of microscopic gsize. These nematodes (Heterodera mariom‘ (Cornu) Goodey) live in the soil iéand penetrate the roots of cotton and other plants. The feeding of the éiworms irritates the tissues, causing swellings 1/32 to ML- i.nch in diameter gin the roots of upland cotton (Fig. 3). When the root knots become large or numerous on plants, they decrease the yield and may cause early death of the plants. The nematodes cause the tufted root symptom ._on some varieties of cotton (Fig. 3). 1g. 3. Symptoms of i nematode root knot, on cotton. symptom on Dixie Triumph 5-5-85yariety. On right, 1 on a susceptible variety. " EXPERIMENTAL PROCEDURE In these studie T: ‘o year and various tests were located in different fields. ~ he diseases involved W easons, the results of each experiment or group of i e given more or less _ hich each experiment lsults for that experiment. On left, the tufted-root arge root knots s, the type of experiment varied somewhat from year Furthermore, ere different in the various experiments. For these similar experiments, separately and the particular conditions under Was carried out are discussed along with the j Moderately susceptible varieties of cotton may appear to be resistant {o mild attacks of disease-producing organisms. Hence, disease resistance ‘L! ‘ l. 10 BULLETIN No». e27, ‘TEXAS AGRLCULTURAL. EXPERIMENT STATION _. was determined accurately only under epidemic conditions whenji causal agents were abundant. Fields containing abundant parasites were ‘ in this work. " Control of wilt by potash fertilizers and resistant varieties Fertilizers and wilt resistant varieties of cotton were studied in to 1941 in experiments which were a part ‘of a series of studies condu’, in several states in cooperation with the Division of Cotton and Fiber Crops and Diseases of the U. S. Department of Agriculture._,-_"'-': H. D. Barker and Dr. A. L. Smith of that Division furnished the.~ii.. and outline for planting. The part of these studies carried out in"I‘_ were made on the B. Pippin farm near Gallatin in Cherokee County. 4 ,1‘ results for East Texas are included in Tables 1, 2, 3, and 8. Thesefie; were practically free from root-knot nematodes. Boll weevils were trolled by dusting the cotton plants with calcium arsenate. h" Variety-fertilizer tests (1937-1939). These experiments were conduc on the Sawyer fine sandy loam soil in which the Fusarium wilt fungus w present and root-knot nematodes were practically absent. Single- ' plots were used with rows 100 feet long and 42 inches apart. The v ties and fertilizers were randomized together and each combinati was used in three replicates. Fertilizers were used at a rate of _ pounds per acre in 1937 and 600 pounds per acre in 1938 and 1939." of the nitrogen fertilizer was applied as a side dressing early in Ju Ceresan treated seed was planted by hand during the latter part of Apm each year:- The plants were thinned to an average spacing of 5 inc in the row. Counts were made of the wilted and de-ad plants in M June, July and August and the cotton was picked in August and Septemb The following varieties of cotton showed adequate wilt resistance wi large yields of good-staple cotton (Table 1) : Clevewilt, Cook 144-68, D‘. Triumph 25-12, Dixie 14-5 Str. 2, Dixie Triumph 55-85, Miller 61 Rowden 2088, Coker 4-in-1, and Deltapine 12. Miller 610 showed t highest average yield. Cook 307, Toole, and Half and Half were sho. staple varieties. Sea Island cotton was immune to wilt but most of bolls fell off in dry weather. The cotton rows without potash fertiliz '9 (6-8-0) usually showed severe symptoms of potash deficiency while the“; symptoms of potash hunger were practically absent from the rows‘ “ with 6-8-8 fertilizer, and were mild and uncommon in the rows wit}; 6-s-4 fertilizer (Fig. 4), The following nine varieties in Table 1 were used in calculating thee fects of potash fertilizers: Clevewilt 6, Cook 144-68, Cook 307, Triumph 25-12, Dixie 14-5-2, Dixie Triumph 55-85, Miller 610, Cok 100, and Half and Half. The use of fertilize-rs containing 4 perce potash resulted in increases of 18 to 53 (Av. 28.5) percent in the average yield of the nine main varieties as compare-d with a 6-8-0 fertilizer. In- creasing the potash to 8 percent gave additional increases of 3 to 2 (Av. 10.5) percent in the 3-year average yields. The average yield of, all nine varieties for three years was 677 lb. of seed cotton per acre: ~9- .1’ . _, y... , Jr“ .. ...1;,§-.f¢:‘.~>v. :1». , .1551.» ‘1.1 ‘ flfif-f‘ .;-:.. I a v . I y" _ M.” _ ‘ I Data on wilt and yield-average of 3 rows Percent yield increase over 1937 1931s 1939 Average Variety l‘ Fertilizer ——- --— —"' _-' 1 —-'—*—j-"—' ; i Seed Seed 1 Seed l Seed H t Plants ‘ cotton, cotton, Plants i cotton, Plants cotton, a1 i wilted, l. lbs. per ' lbs. per wilted, lbs. per 1 wilted, ‘ lbs. per 6-8-0 and ‘. % \ Acre Acre % Acre % Acre Half é ~ 1 1 — ~~ -" _** H lt d H 1L ______________________ __\ e . 46s 485 31-8 499: 1° 1 482 ° ° Q a a?» a _ ______________________ __\ 6&3 l 54g 74,2 193 769 21 3 6814 42 0 " _______________________ __i 6_8_8 2.4 l 570 842 12_9 7852 \ 11 2 731 52 0 EU - ———- — t ~— e: Olevewilt e and 7 _____________________ 6-8-0 0.9 56a P519 0-7 7 0 6 685 0 42 2 " _____________________ -_ 6-8-4. 0.9 974 986 0 4 1023 0 5 861 26 26 g " ..................... -- 9-9-9 9.3 714 1008 1 7 1015 1 1 912 33 25 b, .___ _.___ ~—— ‘ z Ooker 4-in-1 ___________________________ __ 6_s_0 ___- ‘ ---— ---- 1-3 786 i -—-- ---— K 0 m‘ *3 1» ___________________________ __ 6,84 _--_ __-_ ____ 1.1 925 \ ____ -__- 19 20 a _ 7' ___________________________ __‘ 6__8___Q ‘ ____ __:__ ____ 1.0‘ ____ __.__ ‘ Q 00km. 1B§j____________________ _______ __ - w“ 6-89 5.6 528 421 9.0 555 17.0 535 0 11 H _____________________ __, ----- __ 6—8—4 2.5 559 s31 8.9 777 10.8 722 35 6 b‘ ~ _____________________________ -- 6-8-8 3 1 6-58 1972 5.7 l 771 7.7 s94 5e 14 E ______-_._______ —————~——~—~— —-—*———— __- ——"-_~ ——————— —-— 1 ——— 1, J10"- __________________________ _- 6-841 01-8 569 539 1 2 75s 0 s 619 . 0 2s Z CO0 "U4 ___________________________ -- 6-84 01.4 604 951 0 9 s93 1 o s19 32 19 A U " ........................... __ 6-8-8 0.3 725 1094 ‘ 1 0 991 o 5 937 51 29 50° 000k 307 (Rhyme) .................... -- 53-9 0.7 929 e57 1 7 759 1 2 ass 0 42 S ” ____________________ -- 643-4 0.9 747 994 1 3 922 o s s89 29 30 " ____________________ _- 6—8~8 0.1 696 1017 0 7 915 0 3 s76 28 20 Q ~———.—~-—— ——~——--—— — ~———-— ---~ -- --»-—- o Deltapine 11A (D&PL) ............... -- 6-99 --_- . 459 ____ ____ ____ o i _5* H ” ............... -- 6-94 -___ l -_-_ . s95 -___ ___- ____ __-_ 9a 21 " _______________ __ 6~8~8 -___ | -___ . 942 __-_ -___ _-__ -__- 106 12 Deltapine 12; ......................... -- 6-841 i ____ 1.2 e52 ____ ____ o 95 ” __________________________ __ 6-84 ____ -___ 1.6 318 --__ _-__ 24 6 ” _ ------------------------- -_ 6-8-8 ---- ---_ __-_ 2.1 978 --__ \ _-__ 48 25 *Minus sign means yield less than Half and Half variety. i, I Havirdgfliiaaiaiwsi . 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H3 d2 63H!» H3 .2: .222» H3 .8: 62E» I “Hum & éofiou wuinHhH éopuoo wfHSnH 5030a $52M 5030a 323m m Hawm 8% EH5 EH5 L nwNHSHfHwuH H325; L Qwanmrvfl QMHWH $2 Hm? U .85. mmfimnuHHH _ B HHHS» HHHQPHQHH mBOh m Ho wmahté n35 UHHQ uHHB no wfiHQ .UOHflH0flOUll 12 -OMQH|BMQH HMHQNmnnP-HOH HnMQPOHH HQ. MPOOnuO 0.8a, Ufifi #00000 HO oofldwmHmon PHuB QNFOFHGP 1n OQHGH- ~ -'=~'vw=wwiv.w OOTTONS RESISTANT TO WILT ANHD ROOT KNO-T 13 Control of potash hunger. A. Row in left center was Dixie 14-5-2 cotton with 6-8-8 fertilizer. Note freedom from potash hunger as compared with the severe symp- toms in the next row (right center) of Cook 144-68 variety with 6-8-0 fertilizer. Only 3 plants had Pusarium wilt in these two rows. 3. The two center rows were Half and I-Ialf (left) and Coker 100 (fight), both rows with 6-8-0 fertilizer, and both show severe symptoms 01 wilt and potash hunger. Beside these, on the left is a row of Toole cmton and on the right Miller 610 variety, both of which showed but lithe wilt and no potash hunger with the 6-8-4 fertilizer. with 6-8-0 fertilizer, 870 lb. per acre with 6-8-4 fertilizer, and 948 lb. Der ecre With 6-8-8 fertilizer. In Table 1, percentages of wilted plants are shown in association with different percentages of potash fertilizer and cotton Variexies differing in resistance to wilt. By a special method 0f calcllletien (381, for showing the proportion of wilt that was associated With each grade oi potash fertilizer, the above mentioned nine varieties showed the followiig proportions; 45.7 Percent 0f the wilt was associated with 6-8-0 fertilizer, 33.3 H 9’ n n n n as 6_8_4 s: H H n n n 29 n 6_8_8 n Thus, the 4 percent Dvtash in the fertilizer decreased the wilt 12.7 per- cent, and 8 percent Deter-h decreased the wilt an additional 11.7 percent. The Dcteeh fertilizer decreased the percentages of wilted plants in 24 of the 27 tests and in 8 of tie 9 varieties. Clevewilt showed the strongest Wilt resistance and this Wee the only variety that did not show a response to the potash fertilizers. Studies in 1941. Wilt resistant varieties were planted on land which had been fertilized with 5'8'8 fertiiilYc-r at the rate of 500 pounds per acre. Each of. the six "arieties were replicated sight times. The plants suf- fared fro“. drought and aphid injury during um, Summel; AS may be Seen ,-.. "Fable 4, Coker 100 W. R. Str. 39-5, Coker 4-1114, M11161- 510, and miton Dixie Triumph all showed strong wilt resistance and produced large yields of good staple cotton. The 6-8-8 fertilizer appare1~.+_1y mini mized the percentage of wilt as compared with previous seasons. a 14 BULLETIN NO. e217, TEXAS AGRICULTURAL EXPERIMENT silvriox Testing Phosphate Fertilizer in Relation to Wilt (1940) Applications of phosphate fertilizer were accompanied by increases in cotton wilt in some soils according to Tharp and Wadleigh (27). In 1940, the effect of fertilizer with 6 percent phosphate was compared with fertilizer with 12 percent phosphate. Fertilizers at the rate of 600 pounds per acre were applied in the row on April 18 and the seed was planted on April 22. The plants received abundant, well-distributed rains through- out the summer (except for a short drought in July). Examination of the data in Table 2 shows no important differences in the percentages of wilt between the 6-6-6 and the 6-12-6 fertilizer. How- ever, this field had received much phosphate-containing fertilizers during previous seasons, and probably had abundant phosphate in the soil. Effect-s of Phosphate and Potash Fertilizers on Yields (1941) In this test, conducted in the other half of the field concerned in Table 4, each combination of varieties and fertilizers was arranged in dilllieate with the fertilizers applied at the rate of 500 pounds per acre. The yields of the four vareities were combined in summarizing the yield on a fertilizer basis (Table 3) Potash hunger symptoms were serious in the rows with 6-8-0 fertilizer and in the rows without fertilizer. Even without potash, the cotton yielded more with 6-8-0 fertilize‘ than it did without any fertilizer. Because the soil was deficient in pofash the yield was further improved by 6-8-20 fertilizer. In contrast with Table 2, the data in Table 3 show r0 evidenee that cotton yields were decreased by phosphate fertilizer, especially as Sum- marized for all four varieties. A leaf test (by Dr. N D- MOYgaII of the American Potash Institute) using leaves of cotton from rows to which no phosphate was added this year, revealed adequate DhOSDhOPHS in the leaves. Apparently this soil had adequate phosphate fertilizer. The large yield of cotton resulting from the use of 10-0-10 fertilizer indicated that the cotton did not need the phosphate added With the 6-6-6 and 6-12-6 fertilizers. This land was planted in tomatoes in 1940 whiih apparently deereased the infestation by the wilt fungus below its deyree 0f abundance in the adjacent land with continuous crops of cotton 501‘ SiX years. Thus, Half and Half cotton showed more wilt in Table 4 With 6-8-8 fertilizer than it did in Table 3 with 6-8-0 and 0-0-0 fertilize“ applications in these tWo parts of the same field and the same year- ACCOYdiIIglY, a retation of only one year seemed beneficial in decreasing the infestation of the soil with the wilt fungus. Wilt had littl~ effect 011 the yields of the four varieties included in Table 3. wilt Resistance Studies at College Station (1942) Five varjptiGS of cotton (Coker 100, Deltapine 14, Rogers Acala 111, Stoneville 2B and Coker 4-in-1) were planted in Lufkin sandy loam soil 1 GOTTONS RESISTANT‘ TO‘ WILT AND ROOT KNOT 15 Table 2. Eifects of wilt and. phosphate fertilizers on the yield of cotton varieties--1940. Seed Yield Plants cotton, increase Variety Fertilizer wilted* lbs. per over Half % Acre and Half % Half and Half _________________________________ __ 6-6-6 41.4 1147 0 ” ___- 6-12-6 37.0 1084 0 Coker 4-in-1 ____________________________________ __ 6-6-6 4.1 1850 61 ” ____________________________________ __ 6-126 8.4 1762 63 Delfos 425 ______________________________________ __ 6-6-6 3.4 1801 57 ” _ _____________________________________ - _ 6-12-6 1 . 5 1698 56 Dixie Triumph 06-366 __________________________ __ 6-6-6 ' 2.6 1925 68- " __________________________ -- 6-12-6 2.0 1870 73 Early Wilt (Wann.) ........................... __ 6-6-6 2.3 1857 62 ” ___________________________ _- 6-12-6 2.1 1800 66 Miller 610 ____ __ ___ 6-6-0 4.0 2090 82 ” _______________________________________ -- 6-12-6 4.1 1964 81 *EXclusive of dead plants many of which presumably were killed by wilt; calculation based on 200 plants per row. Table 3. Varietal resistance to wilt and. effects of different fertilizers on cotton-—1941. Seed Yield Plants cotton, increase Variety Fertilizer wilted lbs. per over Half % Acre and Half % Halt and Half _________________________________ __ 0-0-0 5.3 578 0 ” ___ .... -- 6-8-0 8.0 801 0 ” -___ 6-8-20 4.7 1036 0 " _________________________________ -- 6-6-6 7.3 1171 0 " _________________________________ -- 6-12-6 8.7 1048 0 " _________________________________ __ 10-0-10 6.0 120'? 0 M11161‘ 610 ---- -_ _--- ___ 0-0-0 0.0 828 43 ” _______________________________________ __ 6-8-0 0.7 1004 25 " _______________________________________ __ 6-8-20 0.7 1501 45 ” _______________________________________ -- 6-6-6 0.7 1349 15 ” _______________________________________ __ 6-12-6 1.6 1385 32 ” _______________________________________ __ 10-0-10 1.0 1362 13 Stonewilt (Wannamakerr) ______________________ __ 0-0-0 0.0 801 39 ” --______e _____________ __ 6-8-0 0.3 1024 28 ” ---------------------- __ 6-8-20 0.0 1322 28 " ______________________ __ 6-6-6 0.3 1238 6 ” ______________________ _- 6-12-6 0.7 1324 2'6 ” ______________________ __ 10-0-10 0.3 1230 2 Tiiton Dixie Triumph _________________________ -- 0-00 0.0 762 32 " _________________________ __ 6-80 0.3 1029 28 ” _________________________ __ 6-8-20» 0.0 1297 25 ” _________________________ _- 6-645 0.3 1280 9 ” _________________________ __ 6-12-6 0.3 1362 30 " ------------------------- _- 10-0-10 0.0 1429 18 (Average of 4 varieties) ________________________ -_ 0-04) 1.3 742 ___- " ________________________ __ 6-8-0 2.3 965 ___- ” ________________________ _- 6-8-20 1.4 1290 ____ " ........................ -- 6-6-6 2.2 1260 ___- ” ________________________ -_ 6-12-6 2.8 1280 ____ " ........................ __ 10-0-10 1.8 137T ___- 16 BULLETIN NO. 627, TEXAS AGRICULTURAL EXPERIMENT STATION '.l'ab1e 4. Wilt resistance of cotton varieties and yie1ds—1941. l] Seed . Yield Plants - cotton, l increase Variety wilted lbs. per l over Halt % Acre l and Half ‘l _, % . l l Half and Half _______________________________________________ __ 11.3 i 956 0 Coker 4-in-1, Str. 4 ___________________________________________ n‘ 3.1 I 1135 l9 Coker 10o W. R. Str. 39~5 ................................... -- 1.2 l 1185 24 Miller e10 ______________________________________________________ _-| 1.3 _ 115s 21 Stonewilt (Wannarnaker)- ___________________________________ _- 0.4 1061 11 Tifton Dixie Triumph ________________________________________ u} 1.1 11015 16 in the Field Plot 0f the Division of Plant’ Pathology and Physiology at College Station in 1942. The seed was planted on April 14, and 200 to 300 pounds of 6-12-6 fertilizer per acre was distributed in the row with thetseed. Each variety was replicated 16 to 22 times in single-row plots 25 feet long. The cotton was picked from September 22 to 25. As will killed a large percentage of the plants of the susceptible varieties, the ex- periment showed the value of the- resistant Coker 4-in-1 cotton in this region (Table 5, Figs. 2, 5). After harvest, data on wilt infection were obtained by cutting the stems and noting the presence of wilt symptoms. (Data furnished by Dr. A. A. Dunlap). Table 5. Effects of wilt on cotton varieties at College Station-1942. l Yield Plants 1 of seed Variety with wilt l cotton, l % = lbs. per l Acre ——~ ~~~~ ~—-——l~———~——l—~———— Coker 100-5 ________________________________________________________________ __ 9‘? 61S Deltapine 14- ______________________________________________________________ __ 92 , 82-8 Rogers Acala 111 __________________________________________________________ ___ 46 ‘ 1019 Stoneville 2B ______________________________________________________________ _-l 92>’ i 1062 Coker 4-in-1, Str, 4_ ______________________________________________________ __; 34 5 1443 Resistance of Cotton Varieties to Root Knot (1939-1941) These experiments were conducted at the Jacksonville Laboratory on Norfolk fine sandy loam soil abundantly infested with the root-knot nematode but in which the wilt fungus was absent. The soil had re- ceived liberal applications of a complete fertilizer. Three to five replica- tions-of the varieties were planted late in April in randomized plots. The plants were plowed out and the roots were classified for root knot in September and October. Based on root-knot susceptibility, the plants were placed in three classes: (1) plants without root knot, (2) plants with only one or a few small knots, and (3) plants with large or num- erous knots. ' The following varieties showed all plants with severe root knot: Cleve- wilt 7, Coker 100, Cook 144-68, Delfos 425, Deltapine 12,, Deltapine 44-51, “vwsqrhwmvivw COTTONS RESISTANT TO‘ WILT AND ROOT KNOT 17 Potcgraph taken in a field infested with the wilt, fungus at College Station showing the following varieties: Row A, Coker 100-5; B, Rogers Acala 111; D, Rogers Acala 111; E, Deltapine 14 all seriously affected with wilt. In row C the superior stand and yield of the Coker 4-in-1 cotton was due to its wilt resistance. Deltapine 11A (D&PL), Dixie 14-5-2, Dixie Triumph 25-12, Dixie Triumph 55-85, Half and Half, Lankart, Lone Star, Mebane, Miller 610, Qualla, Rogers Acala 111, Rowden, Stoneville 2B, and Texacala. Coker 4-in-1, Rhyne’s Cook, and Hi-Bred showed some resistance to root knot. All varieties tested showed serious amounts of root knot although some varieties showed fewer and smaller knots than others. Because of varia- tions in nematode populations, varietal resistance was judged mainly on thelargest percentages of severe root knot in any field in any year. Thus, one test in an area with heavy infestation of nematodes gave more infor- mation about resistance than was learned from several tests over a 3-year period in areas with light infestations. Evidence of ho-st specialization. These studies were conducted in a field used for soil fumigation tests from T936 to 1939. Wooden borders were built on the experimental plots 21/,» x 20 ft. Fourteen of these en- closed plots were checks with untreated soil in which 4O to A100 percent of the watermelon test plants had severe root knot in 1939. However, only 0 to 4 percent of the cotton plants (15 varieties) showed severe root‘ knot in these same plots in 1940. This indicated that the nematodes which had been living on the waterme-lons for three years did not severely attack cotton the following year. Sherbakoff (15) found evidence of 18 BULLETIN NO. 627, TEXAS AGRICULTURAL EXPERIMENT STATION similar host specialization of the root-knot nematode. However, a plot in which tomatoes had severe root knot in 1936 to 1939 also showed severe root knot on several varieties of cotton in 1940 and 1941. Combined Varietal Resistance to Wilt and Root Knot (1941-1942) The resistance of cotton varieties to heavy infestations of both the wilt fungus and root-knot nematodes was studied on the Ault farm near Crafts in Cherokee County, in cooperation with Superintendent P. R. Johnson of Substation No. 2, Tyler, and Dr. N. D. Morgan of the American Potash llnstitute. Two-thirds of this field is Ruston loamy fine sand, and the remainder is Bowie fine sand. The field was planted in cotton in 1936, and in alternate crops of corn and cotton thereafter. Wilt was general in the field in 1940. In 1941, the central portion of the field was planted to Bryant Mebane cotton and the guard rows (2 and 101- 106) were planted with other varieties as shown in Table 6 (Fig. 6). Table 6. Effect of root lmot on wilt resistance of cotton varieties. Ault farm—1941. l Number Plants Variety Row of Fertilizer wilted on i number g plants August 5 i Half and Half _________________________________ __ 103 i761 (Ml-O 34-3 Coker 4-in-1, Str. 4 ____________________________ __ 101 337 6-8-8 0-3 Coker 100 W. R _______________________________ __ 2 320' 6-8-20 0 Mebane (Bryant) _______________________________ __ 3 176 0-0-0 30. Mebane (Bryant) _______________________________ _- 98 209 6—8—8 722* Miller 610- ______ __ ____ 102 341 6~8—20 29-0’! ‘Tifton Dixie Triumph! ________________________ __ 104 l 249' 6'64; 2-0 000k 3m (Rhyne’s Obok) ______________________ __ 105 I 7a 0-0-0 0 Stonewilt (Wannamaker) ______________________ _- 106 l 220' 6~6—6 45.01‘ ‘Most of the Mebane cotton plants died of wilt and disappeared before and after August 5. iWilt resistance was greatly decreased by root knot. IThis variety probably is the same as Dixie "Triumph Wilt Resistant Str. 21, used in 1942. Coker 4-in-1 and Cook 307 (Rhyne’s Cook) cotton showed strong re- sistance to the combined wilt and root-knot disease. Similarly, Coker 100 Wilt Resistant Str. 39-5 and Tifton Dixie Triumph were practically un- injured by wilt. In contrast, nearly 90 percent of the Mebane cotton was killed by wilt‘ in the center of this field. Miller 610 and Stonewilt cotton lost much of their wilt resistance due to nematode infection in this field. Young (37) previously stated that root knot increased the severity of wilt. Cotton varieties were tested (Table 7) in the same field on the Ault farm in 1942 to add to the information obtained in 1941. The 66 rows were 200 feet long and 48 inches apart. On April 18, 333 pounds per acre of 6-8-8 fertilizer was placed in each row. Ten varieties of cotton were randomized and replicated six times, and two other varieties (Harper U Mebane and Rhyne’s Cook) were planted in triplicate guard rows. The seed was planted on April 27 and a thick stand of seedlings emerged which were thinned to 500 plants per row On May 15. OOTTONS RESISTANT’ TO‘ WILT AND ROOT‘ KN OT 19 Above: iBryant Mebane cotton (center row) dwarfed or killed by Eu- sarium wilt, in contrast to Dixie Triumph Wilt Resistant Str. 21 on left, and Delta-Dixie Wilt Resistant Str. 2 on right (1942). Below: Same field in 1941 with MeJoane cotton (n11 left) ruined by Wilt and wilt-resistant Goaer 4-in-1 variety on right without visible injury. This field was infested with root-knot nematodes in addition to the Pusarium wilt fungus. An application of 400 lb. per A. of 6-8-3efer- tilizer prevented potash deficiency symptoms in this field. BULLETIN NO. 627, TEXAS AGRICULTURAL EXPERIMENT STATION .322; HEHH H25 58w; wBoH w E uwuinoucmp Him? HEN s53 $2 E2.» @535 ENE mHEQi mEfiFHH; oH .550 o5 HSPH 932w m n? d!“ Hlfinfi fi F4 fionsanfiu HOQMIPOOH Una.“ uHnB UOQMREOO gm m2“ m? .......................... {Qm siafisw N5 w?“ wdH - |||||||||||||||||||||||||||| ldHw SHHQH .93. wmyw H}... .................. 12D Hfibwmv wnfifié Ham 8E mé. ..................... {SHEEHHV @5232 W2 SQ“ W5 .......... :5 .m .B .5. 2x5 amuse?» 9m mg 9m ............. 25w 1m <3 QHHHHHHHZH Hi5 maH 3% Hww ................... 1w ..~H .3 wHNHD-GHHQC ¢ an $2 m5 .................... LE4... 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H53 Ho 32w am o» mm Hvnfifiawm no c313 3H5 $.39 OP moHaoHns> fiOHPQO HO ooflsamHmofi .5 0.5.38 A w, OOTTONS RESISTANT TO’ WILT AND ROOT KNOT 21 The wilted plants were counted at five different times in June and July, and these were removed from the field in June, but not in July. Due probably to the removal of wilted plants and the hot, dry weather from June 25 to August 15, there was little spread of wilt after July 15. The cotton was picked four times from August 13 to September 24. After harvest, all of the cotton plants were loosened with a sweep blade and pulled, and the roots were classified for abundance of root knots, using a system (19) based on the percentage of lateral roots with root knot per plant. The plants in each row were divided into six classes as follows: Plants without root knots. Plants with knots (usually 1 to 10 apiece) on only 1 to 25 percent of the lateral roots or with knots on the tap root only. Class 0 1 2 Plants with 26 to 50 percent of the roots knotted. 3 4 Plants with 51 to 75 percent of the roots knotted. Plants with 76 to 100 percent of the roots knotted. 5 Dead plants with decayed roots. The degrees of varietal resistance to root knot are shown by the per- centages of plants in the different classes (Table 7). The following method was‘ used to combine these class percentages into a Weighted symbol of root-knot resistance for each variety to give a simple numerical expression in each case. The percentage of plants in Class O was multi- plied by 5; in Class 1, by 4; in Class 2, by 3; in Class 3, by 2; and the percentage in Class 4 was multiplied by 1. These product‘ percentages were added to give the weighted symbol of resistance for the variety. Using Bryant Mebane for example in Table 7 the formula is used as follows: 1.0 4.0 9.3 20.1 65.6 x5 x4 x3 x2 x1 5.0 + 16.0 + 27.9 + 40.2 + 65.6 I 154.7 (155) The value 155 is the weighted symbol that is useful in expressing root- knot resistance in one figure. A sufficient number of plants (820 to 1438) of each variety remained alive to provide an adequate basis for showing any resistance- to root knot. It may be assumed that large percentages of the roots of the other plants bore knots before the plants died. Some of the cotton seedlings showed nematode infection when they were thinned in May. Root knot probably did not decrease cotton yields seriously on the plants in Class 1. However, there usually were 50 to 100 or more knots on the roots of each plant in Classes 3 and 4, and such plants were evidently damaged by the disease. The effects of wilt and root knot were insep- arably associated in decreasing the cotton yields in this field. Miller 610 and other very susceptible varieties showed large root knots and some of the susceptible varieties including Miller 610, Coker 100 W. R., and Dixie Triumph W. R. Str. 21 showed a large percentage of the plants with the tufted root symptom of root knot (Fig. 3). However, the tufted-root symptom was rare on the susceptible Mebane and Delta- 22 BJULLETIN NO. 627, TEXAS AGRICULTURAL EXPERIMENT STATION pine 14 varieties. Some of the Wonder Dixie Triumph and Rhyne’s Cook plant's showed enlarged roots with irregular swellings probably due to nematode infection. Coker 4-in-1 variety was outstanding in its resistance to root knot be- cause most of its roots were classified in the first three groups. Rhyne’s Cook was the only other variety that showed prominent resistance to this disease.“ All of the other 1O varieties were very susceptible to root knot (Table 7). Coker 100 W. R, Str. 39-5 and the three Dixie varieties were very susceptible to root knot, but this disease did not greatly decrease their wilt resistance. These four varieties, although showing a high percentage of knotted roots, were very tolerant to root knot. Root-knot nematodes had the general effect of decreasing the wilt re- sistance of cotton varieties probably by wounding the roots and by decreasing the vigor of cotton plants. This effect was very prominent in the Miller 610 variety in which root knot greatly decreased the wilt re- sistance (Tables 1, 6, 7). In contrast, root knot showed only a moderate effect in decreasing the wilt resistance of Coker 100 W. R. Str. 39-5 and the three Dixie varieties, probably because these varieties are tolerant to root knot as indicated by their satisfactory yields (Table 7). Despite the extremely large amount of root knot, plants of Dixie Triumph W. R. Str. 21 retained their leaves unusually well during the drought and were apparently drought‘ resistant. Apparently due to their resistance to both wilt and root knot separately and in combination, Coker 4-in-1 and Rhyne’s Cook showed little decrease in wilt resistance through nematode infection, Wilt resistance was so low in Mebane, Deltapine 14, Half and Half, and Stoneville 2B varieties that root knot caused no further apparent decrease in their wilt resistance. Stoneville 2B merited favorable mention because of its fair yield under these severe conditions. Staple Lengths and Lint Percentages The staple length and lint percentage of many of the varieties used in these studies are given in Table 8. This table was summarized mostly from data supplied by Dr. H. D. Barker from eleven-boll samples taken from each row every year from the fields mentioned in Tables 1 and 2. The staple lengths, originally calculated by Dr. Barker to hundredths of a thirty-second part of an inch, were changed to inches and fractions thereof for this table. Discussion of Wilt Resistance The wilt fungus, Fusarium vasinfectum, is a facultative parasite that is naturally most destructive in weak plants. Accordingly, plants that are weakened by potash hunger or by root knot are usually more suscep- tible to wilt than plants having adequate fertilizer, normal roots, and good growing conditions. Although tests of many varieties may show in- tergradations it is helpful to arrange the cotton varieties in four groups COTTONS RESISTANT" TO‘ WILT AND ROOT‘ KNOT‘ 23 based 0n their resistance to the combination of wilt and root knot‘: (1) Mebane and Half and Half cotton are very susceptible to both wilt and root knot, and root knot had little effect‘ in decreasing their low wilt resistance. (2) Three of the Dixie varieties were resistant to wilt and tolerant to root knot, and root knot‘ did not greatly decrease their wilt resistance. ,(3) Miller 610 and Stonewilt were resistant to wilt but sus- ceptible to root knot, and root knot‘ greatlydecreased the wilt resistance of these varieties. (4) Coker 4-in-1 and Rhyne’s Cook were resistant to wilt and root knot separately and together, and root knot had little effect in decreasing their wilt resistance. Table 8. Staple length and percentage of lint of cotton varieties. Years Average Average Variety in staple percentage test length, inches of lint Clevewilt 6-- ________________________________________________ __ 2 1 36.6 Olevewilt 7__ _________________________________________________ __ 1 1 34.1 Ooker 4-in-1 ___________________________________________________ __ 3 1 2/32 36.6 Coker 100 W. R. Str. 39-5 __________________________________ __ 1 1 1/32 37.5 Coker 100_ ____________________________________________________ __ 3 1 1/32 36.3 Cook 144-68 ___________________________________________________ __ 3 31/32 36.6 Cook 30"? (Rhyne’s Cook) ____________________________________ __ 3 27/32 37.6 Delfos 425 _____________________________________________________ __ 1 1 3/32 34.4 Deltapine 11A (D&.PL)_ ______________________________________ __ 1 1 41.6 Deltapine 12 ___________________________________________________ __ 1 1 38.0 Deltapine 14* _____ __ 2 1 39.0 Dixie 14-5 Str. 2 _____________________________________________ __ 3 1 33.7 Dixie Triumph 06-366- _______________________________________ __ 1 30/32 37.5 Dixie Triumph 25-12 _________________________________________ __ 3 1 1/32‘ 33.6 Dixie Triumph 5-5-85 _________________________________________ __ 3 29/321 34.1 Early W. R. (Wann.) _______________________________________ __ 1 30/32 39.6 Half and Half __________ __-_ ___________________________________ __ 5 25/32 45.1 Hi-Bred* ______________________________________________________ __ 2 251/312 42.0 Miller 610 _______________________________________________________ _- 5 31/32 38.2 Rogers Acala 111* _____________________________________________ __ 2 1 1/32 36.0 R-owden 2088- _________________________________________________ __ 2 30/32 34.6 Sikes_ _________________________________________________________ __ 1 1 33.0 Stoneville 2B* _________________________________________________ __ 2 1 1/32 34.0 Stonewilt ______________________________________________________ __ 1 1 2/32 35.9 Tiiton Dixie Triumph ________________________________________ __ 1 1 1/32 37.1 Toole __________________________________________________________ -_ 2 29/32 36.2 *Data. by Division of Agronomy, based on experiments at Substation 11, Nacogdoches, and Substation 2, Tyler. METHODS OF DISEASE CONTROL Based on local experience and the recorded work of others, the follow- ing methods are recommended for controlling wilt, root knot‘, and potash hunger under East Texas conditions. Special care should be taken to control these diseases in sandy loam soils because they are more destruc- tive in such soils than in clay soils. Crop rotations should be planned (36) so "that only immune or resistant’ crops are planted in soil that is badly infested with the disease-causing organisms. Root knot can be con- trolled in one year by planting disease-immune crops in rows, hand weed- ing and hoeing the seedlings, and cultivating the crop every 10 to 14 days throughout the growing season. If weeds are allowed to grow, how- 24 ' BULLETIN NO. 627, TEXAS AGRICULTURAL EXPERJMENT STATION ever, it may require several years to accomplish the same purpose even if immune crops are planted. Orotala-ria spectabiZ-is, sorghum, and Velvet bean are practically immune to root knot and are recommended for starving the nematodes out of the soil. Although not a forage crop, crotalaria produces a large yield of nitrogenous organic matter for plowing into the soil. It should be planted in March, and the green plant's should be disked and plowed into the soil in the fall. Sorghum has the, advantage of producing a forage crop in addition to starving the nematodes, but commonly adds little humus to the soil. Texas Agr. Exp. Sta. Progress Rept. S37 by G. H. Godfrey showed that‘ root knot was profitably controlled by p1OWi11g land 3 times to dry the nematodes in hot weather. v Certain nematode-resistant crops grow well and produce good yields in infested soil. Such resistant crops adapted for use in East Texas are corn, Bermuda grass, oats, Iron and Brabham cowpeas, Porto Rico sweet potatoes, peanuts, and Laredo soybeans. Moderately resistant crops may maintain nematodes in the soil so that following susceptible crops may be seriously affected by root knot. Cultivating land often enough to keep it free from green plants, and keeping the soil crust broken will starve out the nematodes completely or nearly so within a year, but this method is expensive and leaves the loose soil exposed to erosion and loss of organic matter. Hence, growing an immune crop on the land for a few years, keeping it practically free from weeds, and plowing the refuse plant ma- terial into the soil is the preferable method of controlling the nematodes. Such a procedure enriches the soil at the same time. With cotton, the use of 300 to 400 pounds of 6-8-8 or 4-10-7 fertilizer per acre provides adequate potash to prevent serious potash hunger (defi- ciency) symptoms. ' In the case of cotton, it is best to avoid land that is badly infested with disease-causing parasites. For land with slight or no infestation by these soil parasites, tests in East Texas by the Texas Agricultural Experiment Station have resulted in the recommendation of the Stone- Ville 2B and Deltapine 14 varieties (Table 8). When it is necessary to use land in which only the wilt fungus is abun-dant, the Miller 610, variety is preferable because it has adequate wilt resistance, high yield- ing capacity, and is easy to pick. Coker 100 W. R. Str. 39-5, Tifton Dixie Triumph, Delta Dixie Wilt Resistant Str. 2, Clevewilt, Cook 144-68, Dixie Triumph 25-12, Dixie 14-5 Str. 2’ and Deltapine 12 are also good wilt-resistant varieties for such fields. If it is necessary to plant‘ cotton in soil that is seriously infested with parasites causing wilt and root knot, however, only the Coker 4-in-1 variety is recommended. This variety is resistant to the combination of wilt and root knot, and produces fair yields of good-length fiber. Rhyne’s Cook has much of this double resist- ance also, but it has a short staple length. OOTTONS RESISTANT TO‘ WILT AND ROOT‘ KNOT 25 LITERATURE CITED (1) Armstrong, G. M., B. S. Hawkins, and C. C. Bennett. Cross inoculations with isolates of Fusaria from cotton, tobacco, and certain other plants subject to wilt. Phytopath, 32: 685-698. 1942. (2) Barker, H. D. Relation of nematodes to wilt. Proc. Assoc. S. Agr. Wonk- ers. 39: 147. 1938. (3) Cralley, E. M. A study of virulence in relation to cultures of Fusarium" vasmfectum. Phytopath. 29: 757. 1939 (4) Ezekiel, W. N. and A. A. Dunlap. Cotton diseases in Texas in 1939. U.S.D.A. Pl. Dis. Rptr. 24; 434-439. 1940. (5) Ezekiel, W. N. and J. J. Taubenhaus. Variety tests in the differentiation of two cotton Wilts. Phytopath. 24: 292-295. 1934. (6) Johnson, P. R. Cotton. Texas Agr. Exp. Sta. Ann. Rept. 53: 145. 1940. (7) King, C. J. Comparative injury of root-knot nematodes t0 different varie- ties and species of cotton in control experiments under. irrigation. Phy- topath. 28: 664. 1938. (8) King, C. J. and Claud Hope. Field practices affecting the control of cot- ton root knot in Arizona. U. S. Dept. Agr. Circ. 337, 1934; also Phytopath. 30: 709. 1940. (9) Miles, L. E. Some tests of varietal susceptibility to a combination of root-knot nematode and cotton wilt. Phytopath. 29: 974-978. 1939. (10) Neal, D. C. Cotton Wilt. Miss. Agr. Exp. Sta. Tech. Bul. 16. 1928. (11) Neal, D. C. Artificial inoculation with the cotton-wilt fungus, Fusarium vz:.s'iz1._/cvtimn. Phytopath. 29: 755. 1939. (12) Neal, D. C. and H. B. Brown. Wilt resistance of the new cottons. Better Crops with Plant Food 24(10): 16. 1940; also Phytopath. 30: 705. 1940. (13) Neal, D. C. Regional cotton-wilt studies: phosphate-variety tests in Louisi- ana. Phytopath. 31: 769. 1941. (14) Shaw, K. J. The effect of crop rotation on the control of Heterodera marioni on Norfolk sandy loam. Phytopath. 30: 710. 1940. (15) Sherbakoff, C. D. Root-knot nematodes on cotton and tomatoes in Ten- nessee. Phytopath. 29:751. 1939. (16) Sherbakoff, C. D. Pathogenicity tests of different isolates of Fusarium vasinfectum in 1940. Phytopath. 31: 770. 1941 . (17) Smith, A. L. A regional study of the relationship of potash treatments to_the development of cotton wilt under widely varying conditions of S011 and environment. Phytopath. 30: 707. 1940. (18) SnéilthTzA. L.94Regional cotton-variety-wilt-phosphorus study. Phytopath. : . 1 1. (19) Smith, A. L. The reaction of cotton varieties to Fusarium wilt and root- knot nematode. Phytopath, 31: 1099-1107. 1941. (20) Smith, A. L_. and A. L. Taylor. Nematode distribution in the 1940 regional cotton wilt plots. Phytopath. 31: 771. 1941 (21) Taubenhaus, J. J., W. N. Ezekiel, and D. T. Killough. Relation of cotton root rot and Fusarium wilt to the acidity and alkalinity of the soil. Texas Agr. Exp. Sta. Bul. 389. 1928. (22) Taubenhaus, J. J., W. N. Ezekiel, and H. E. Rea. A new cotton wilt. Phytopath. 19: 171-173. 1929. (23) Taubenhaus, J. J. and W. N. Ezekiel. Seed transmission of cotton wilt. Science 76: 61-62. 1932. (24) Taubenhaus, J. J. and L. D. Christenson. Role of insects in the distribu- tion of cotton Wilt caused by Fusarium. vasinfectum. Jour. Agr. Res. 53: 703-712. 1936. (25) Taylor, A. L., H. D. Barker, and P. H. Kime. Further observations on the nematode-Fusarium-wilt experiments at Lumberton, N. C. Phytopath. 30:710. 1940. (26) Tharp, W. H. and V. H. Young. Relation of soil moisture to Fusarium wilt of cotton. Jour. Agr. Res. 58: 47-61. 1939. (27) Tharp, W. H. and C. H. Wadleigh. Effects of nitrogen, phosphorus, and potassium nutrition on the Fusarium wilt of cotton. Phytopath. 29: 756-757. 1939. (28) Tisdale, H. B. and J. B. Dick. Cotton Wilt in Alabama as affected by potash supplements and as related to varietal behavior and other im- portant agronomic problems. Jour. Amer. Soc. Agron. 34: 405-426. 1942, (29) Tyler, J. Plants reported resistant or tolerant to moot-knot nematode in- festation. U. S. Dept. Agr. Misc. Publ. 406. 1941. 26 BULLETIN NO. 627, ‘TEXAS AGRICULTURAL EXPERIMENT STATION (30) Ware, J.‘ O. and V. H. Young. Control of cotton wilt and rust. Ark. Agr. Exp. Sta. Bul. 308. 1934. (31) Watson, J. R. and C. C. Goff. Control of root knot in Florida. Florida Agr. Exp. Sta. Bul. 311. 1937. (32) Yrzsibng, 1339A. Wilt-resistant cotton. Texas Agr. Exp. Sta. Prog. Rept. 4. 1 . (33) Young, P. A. Millen 610, a commerciai variety of wilt resistant cotton for East Texas. Texas Agr. Exp. Sta. Ann. Rept. 53: 222. 1940; also 52: 224, 1939; 51: 193, 1938; 50: 102, 1937. (34) Young, P. A. Potash helps cotton resist wilt, rust, and drought. Better Crops with Plant Food 24(4): 6-7. 1940. (35) Young, P. A. Two kinds of resistance to cotton wilt as affected by root knot. Texas Agr. Exp. Sta. Ann. Rept. 54: 146. 1941. (36) Young, P. A. and H. F. Morris. Crop rotation to control plant diseases 1n East Texas. Texas Agr. Exp. Sta. Prog. Rept. 821. 1943. (37) Young, V. H. Cotton wilt studies. Ark. Agr. Exp. Sta. Bul. 226. 1928. (38)‘ Young, V. H. and W. H. Tharp. Relation of ferftilizer balance to potash ilélfigel‘ and the Fusarium wilt of cotton. Ark. Agr. Exp. Sta. Bul. 410.