A416-220-8m-175-L TEXAS AGRICULTURAL EXPERIMENT STATION AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS ‘ W. B. BIZZELL, President BULLETIN NO. 260 ' JANUARY, 1920 DIVISION OF PLANT PATHOLOGY AND PHYSIOLOGY WILTS OF THE WATERMELON AND RELATED CROPS (Fusarium Wilts of Cucurbits) B. YOUNGBLOOD, DIRECTOR, COLLEGE STATION, BRAZOS COUNTY, TEXAS ‘ . STATION STAFF? ADMINISTRATION B. Yotmauuoon, M. S., Director A. B. CONNER, B. S., Vice Director J. M. Jones, A. M., Assistant Director CHAS. A. FELKER, Chief Clerk A. S. WARE, Secretary , Executive Assistant CHARLES Sosoux, Technical Assistant VETERINARY SCIENCE *M. FRANCIS, D. V. M., Chief H. SCHMIDT, 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. Losmwrrz. B. S., Assistant Chemist F. B. SCHILLING, Assistant Chemist J. B. SMITH, B S , Assistant Chemist WALDO WALKER, Assistant Chemist HORTICULTURE H NFSS, M. S., Chief W. S. HOTCHKISS, Horticulturist ANIMAL INDUSTRY . J. M. Joni-ts, A. M., Chief; Sheep and Goat Investigations IJ. C. BURNS, B. S., Animal Husbandman in Charge of Reef Cattle Investigations (on leave) J. B. McNULTY, B. S , Doiryman R. M. SHERWOOD, Pouttryman O. E MECONNELL, Animal Husbandman in Chan/e o] Swine Investigations . R.G. BREWER, B. S., Assistant Animal Hus- ENTOMOLOGY I‘ M. C. TANQUARY, Ph. D., Chief; State Ento- mnlouist ‘ H. J. REINHARD, B. S., Entomologist H. B. PARKS, B. S., Apiculturist C S. RUDE, B. S., Assistant Entomologist AGRONOMY A. B. CONNER, B. S., Chief A. H. LEimcn, B. S., Agronomist E. W. GEYER, B. S., Agronomist H. H. LAUDE, M. S., Agronomist PLANT PATHOLOGY AND PHYSIOLOGY J. J. TAUBENHAUS, Ph. D., Chief ~ ' FEED CONTROL SERVICE F. D. FULLER, M. S., Chief J AMES SULLIVAN, Executive Secretary FORESTRY E. O. SIECKE, B. S., Chief, State Forester PLANT BREEDING E. P. IluiviBERT, Ph. D., Chief FARM AND RANCH ECONOMICS H. M. EuOT, M. S., Chief SOIL SURVEY - **\V. T. CARTER, JR.. B. S., Chief T. M. BUSHNELL. B. S., Soil Surveyor W. B PR‘\ClS. B S.. Soil Surveyor bandman H. W. HAWKER, Soil Surveyor SUBSTATIONS No. 1. Beeville, Bee County No. 8. Lubbock, Lubbock County I. E. COWART, M. S., Superintendent No. 2. Troup, Smith County W. S. HOTCHKISS, Superintendent No. 3. Angleton, Brazoria County E. B. REYNOLDS, M. S., Superintendent No. 4. Beaumont, JelTerson County A. H. PRINCE, B. S., Superintendent No. 5. Temple, Bell County D. T. KJLLOUGH, B. S., Superintendent No. 6. Denton, Denton County _ C. . MCDOWELL, B. S., Superintendent No. 7. Spur, Dickens County R. E. DXCKSON, B. S., Superintendent TAs of February 1, 1920. R. E. KAnPER, B. S., Superintendent D. L. JONES, Scientific Assistant No. 9. Pecos, Reeves County_ J. W. JACKSON, B. S., Superintendent No. 10. (Feeding and Breeding Substation), College Station, Brazos County .............................. Superintendent E. C ~ MEROv, Scientific Assistant No. ll. Nacogdoches, Nacogdnches County G. T. McNEss, Superintendent ‘No. 12. Chillicothe, Hardeman County A. B. CRON, B. S., Superintendent V. E. HAFNER, B. S., Scientific Assistant No. l4. Sonora, Sutton-Edwards Count!” E. M. PETERS, B. S., Superintendent {In cooperation with School of Agriculture, A. dz M. College of Texas *In cooperation with the School of Veterinary Medicine, A. & M. College of Texas. "In cooperation with the United States Department of Agriculture. BULLETIN N0. 260. FEBRUARY, 1920. WILTSCOF THE WATERMELON AND RELATED CROPSY (Fusarium lllilts of Cueurbits.) BY J. J. TAUBENHAUS. Watermelons constitute an important agricultural crop in Texas and are grown mainly in light sandy soil. The United States census esti- mated the area devoted t0 watermelons in Texas in 1910 as 18,466 acres, with a value of $539,313. Since then the acreage has increased at least 20 per cent. Of late, Texas watermelon growers, especially those in Waller County, experienced considerable difliculty in producing a normal crop. The failure was due primarily to several important fungous diseases. A conservative estimate may place the money lo-sses from these diseases at not less than 20 per cent. of the total crop in the State. This does not take into consideration the waste from diseases of squashes, cashaws, pumpkins, cucumbers, and cantaloupes, which are of no little economic concern. Of the many diseases which affect watermelons and other cucurbits in Texas, the Fusarium wi.lts are by far the most important. Water- melon wilt especially is not only prevalent in Texas, but according to Orton (15) it is also found from Maryland to Florida, in Alabama, Iowa, Oklahoma, California, and Oregon. On account of its economic im~ portance, investigations were begun in 1916. The results obtained, and here presented, deal with studies on the Fusarium wilts of water- melons and related crops. The other diseases of eucurbits are now being studied and the results obtained will be presented in a later pub- lication of the Texas Agricultural Experiment Station. The field ex- periments on this project were carried out at the Prairie View Normal School. and grateful acknowledgment is due to the authorities of that institution and especially to Professors Waller and Ed Williams for whole-hearted assistance and cooperation. The writer was also assisted by different laboratory helpers, who, because of the war, did not remain long enough with the work. In this connection, however, mention should be made of the valuable assistance rendered by lllr. Albert Johnson, formerly a graduate student of the Texas Agricultural and Mechanical College and now captain inthe U. S. army. Ilrsronrcxr. The investigation of the Eusarium wilt of watermelon received first attention from Dr. Erwin Sniith(2l l, xvho in 1899 devoted considerable study to it. However, Dr. Smith’s claim that the fungus Alerosmospora 4- TEXAS AGRICULTURAL EXPERIMENT STATION. easinfecta was the perfect or ascus stage of B’1Lsa1*i2¢11z easinfectuivz, orig- inally’ described by Atkinson(1) as causing a wilt disease of cotton was the cause, of much confusion. At first no one seemed to question these results, as’ they were accepted by most Workers, among whom may be mentioned Martin(14), Stuckey'(24i), and others. Of those to chal- lenge the validity of Dr. Smitlfs conclusions was Higgins(12), who showed that Fusariunz tiasinfecietm Atk. and Alecosmospora vasinfecta (Atk.) Eur. Sm. were not genetically related. Furthermore, Higgins(12) has shown that the watermelon fu.ngus referred to by Dr. Smith as Necosmospora vas/inlfccta var. ’I’l/l:’L-’6’lt-7IZ was really a distinct species, to be referred to as Fusariurrr» niveum Ew. Sm.) Later, Butler(2), Dela~ croix(6), and Wollen\veber(25), like Higgins, also proved that N ecos- mospom easi-nfecia. was not in any way related to the Fusamhtm rvasinfeetzz/m or to any other pathogenic Fusaria. Pnnsnnr WonK. It was already mentioned previously that Fusarium wilt is one of the serious drawbacks to profitable xvatermelon culture in Texas. This is also true with the squash and the cashaw’, which suffer from a serious Fusarium_ wilt, but this wilt, as will be shown later, is caused by a Fusarium which is distinct from the fungus that causes wilt of the watermelon. The scope of the present work attempted to answer the following points relative to wilt diseases of cueurbits and other crops: (1) Is N ec0s1n0sp01'a- easinfecta the ascus (winter-resting spore stage) stage of Fursa-riu-m vasinfectum which causes a wilt of cotton? (2) Is Fusarrivtinz nivelztm the conidial or summer fruiting stage of Alecosmospora {tia-si/zzfecta or is it a distinct- species? ( 3) Is Fusarizv/n easinfeciztlm the cause of watermelon wilt (-1) Is the Fusaritim wilt of squash and cashaw similar to or dis- tinct from the Fusarium wilt of the watermelon? (5)) Is Fusarilzzm. ni/veuvn in any xvayr related to the wilts of cotton, okra, eowpea, Irish potatojtomato, cabbage, or sweet pea? (6) Is watermelon wilt induced by more than one species of Fusarium? ('7) Are cotton and okra wilts induced by the same fungus, Flusariu m earsinfectzvm .9 ’ (8) What is the life history of the wratermelon wilt fungus? (9) What is the effect of soil temperature on the prevalence of the watermelon wilt? Blnrrron or Pnoenntnn. In order to definitely establish the above ‘points, three series of experi- ments were planned. namely: (l) Field tests: (f3) fgreenhouse experi- ments; (3) laboratory technic. ‘See also Taubenhaus, J. J. Diseases of truck crops: 244-246, 1918. (E. P. DHttOH Co., New York.) . WrLrs OF WATERMELON ANDO RELATED CnoPs. o A. FIELD TESTS. As previously mentioned, the field work was carried out at the Prairie View Normal College (luring four consecutive seasons. The above place was chosen because of the severity of cucurbit wilts there. Field tests were also carried out on the farms of Messrs. Garret and Robinson, to whom grateful mention is here due. At Prairie View College, the field tests were planned as follows: (a) One-half acre of watermelon “sick” soil, designated as plot A ' ' (chosen because watermelons had died badly there), was planted to watermelon, squash, cashaw, pumpkin, cucumber, cantaloupe, gourd, citron, cotton, cowpea, okra, and Irish potato, all being arranged in the order as shown in Table 1. Plot A was set aside as a permanent water- melon “sick” field in order to study the watermelon wilt and its rela- tionship to the wilts of the other hosts mentioned in Table 1. (b) One-half acre designated as plot B was chosen because of the fact that squashes and cashaws had died there for a number of years. This plot was planted to squash, cashaw, watermelon, gourd, cucumber, cantaloupe, cowpea, cotton, okra, and Irish potato. The arrangement of these hosts was made as indicated in Table 2. The object here was to determine whether or not the wilts of the squash and eashaw were the same as the‘ wilt ofwatermelon, or if possibly related to the wilts of the other hosts indicated in Table 1. (c) One-half acre designated as plot C was chosen because of its being virgin land and was planted to Watermelons for the first time in 1916. This field was a pasture for a large number of years and was, as far as known, never planted to watermelons. Plot O was divided in equal halves, one part of which was fertilized with manure and the other half with commercial fertilizers. At the end of the summer season all the old watermelon vrines and fruit culls in both parts of the plot were l turned under with the plow (see Table 3). The object in plot O was to determine how many years it would take for a supposedly virgin land to become infected with watermelon wilt. ‘ - (d) One acre of watermelon “sick” soil designated as plot D was divided into three equal parts. One part was devoted to watermelon, the second to oats and cowpeas, the third to corn, a basis for a three~ year rotation being thus formed. The object of this field (see Table 4) was to determine the effect 0t a three-year rotation on the control 0t watermelon Wilt on sick soil. y (e) One acre oi’ virgin land designated as plot E was divided in the same way as in D (see Table 5). The object in this plot was to de- termine whether a three-year rotation practiced on a virgin land would keep out watermelon wilt indefinitely. (f) One-half acre of virgin land rglesignatedas plot F was planted to cucumber and re-antaloupe, in which was also intermingled watei" melon, squash, gourd, and cashaw. The object in this plot was to de- termine what would be the eitect of growing various cucurbits on the same land and which of the cucurbit diseases would be common to all. 6 TEXAS AGRICULTURAL EXPERIMENT STATION. As no wilt; appeared, further mention of this plot will, therefore, be omitted in this bulletin. (s) was planted to various varieties of Watermelons. This was done in crder to determine the existence, if any, of resistant varieties. (h) One acre of “tilt-infected squash land designated as plot H was planted t0 various varieties of squash, pumpkin, gourd, cantaloupe, and cucumbers so as to determine the presence, if any, of resistant varieties. (i) One acre designated as plot I at the Robinson farm (in which cowpeas died badly from Fusarium wilt and okra only slightly), was planted to cowpeas, okra, cotton, squash, gourd, cashaw, Watermelon. tomato, and cabbage. The object in this plot was to determine the relationship, if any, of the cowpea and okra Wilts to the other hosts grown there. The experiments in plots A to I were carried on during 1916, 1917', 1918, and 1919 and the results obtained follow: Table 1.-—Watermelon sick field. One acre of wilt-infected watermelon land designated as plot G u Host 1916 1917 1918 1919 Squash . . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . l-hQuotgvlqz, % of 1% killed** 1 e Cotton . . . . . . . . . . . 100% healthy.. . . 100% healthy. . . . 100% healthy. . . . 100% healthy Cowpeas . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy Watermelon... . . . . 97% killed* .... 4% killed* . .. 98% k1ll6d* . . . . 96 kil d Cucumber . . . . . . . . 100% healthy.. . . 100% healthy 100% healthy 100% health Watermelon... . . . . 92% k1lled* . . . . 90% k1lled* . . . . 92 killed* . . . 99 killed* ,Cantaloupe . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy kra . . . . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy Gourd . . . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . 100% healthy Watermelon... . _. . 98% k1lled* . . .. 97 k1lled* . . .. 9 % k1lled* .. . 92% killed* Citron._ . . . . . . . . . . . 100% healthy . . 100% healthy. . . . 100% healthy. . . . 100% healthy Pumpkin . . . . . . . . . 100% healthy . . 100% healthy.. . . 100% he thy. . . . 100% healthy Cotton . . . . . . . . . . . 100% healthy . 100% healthy. . . . 100% healthy. . . . 100% healthy Watermelon. . . . . . . 79 k1lled* . . 89% k1lled* . . . . k1lled* . . . . 98% killed* Okra . . . . . . . . . . . . . 100% healthy. . . . 1007 healthy. . . . 100% healthy. . . . 100% healthy Citron . . . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% health Cashaw . . . . . . . . . . . 100% healthy.. . . 100% healthy. . . . % of 1% killed** y o4‘ 11% kil ed** Watermelon... . . . . 95% k1lled* .. .. 92% k1lled* .. .. 97% killed . . . . .. 96%ki led Irish potato . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy Tomato. . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy Errnocr: OF A Sick Sort. 0N WATERMELONS. In studying Table 1, it will be seen that during four seasons’ trials, Watermelons persistently died from Fusarium wilt on a watermelon sick soil. During 1916 and 191'?’ none of the squash, cucumber, cantaloupe, gourd, citron, pumpkin, cashaw or any of the other hosts mentioned in Table 1 were affected in any way by the watermelon wilt. This, from a practical consideration, proved conclusively that the wilt-producing fungus in the Watermelon sick soil was responsible for the dying of the watermelons in that land- During 1918 and 1919, however, a slight per cent. of the squash and cashaw died from a Fusarium wilt which upon isolation proved to- be different from the Fusarium wilt of Water- "’"I'*The fungi isolated from the dead watermelon plants corresponded to Fusarium niveum, F. citrulli and F. poolensis. W**The fungus isolated from the dead squash and cashaw was identical with Fusarium cucurbitae. ' WILTs or WATERMELON AND RELATED CBors. '7 melon but identical with the organism of squash Wilt. In this case the Fusarium of the squash and cashaw was evidently introduced from the squash-wilt-infected land to the Watermelon sick soil. Table 2.-—Squash, Fusarium sick soil. i Host 1916 1917 1918 y 1919 Squash . . . . . . . . . . . 78% killed* . . . 82% killed* . . . . 77% killed* . . . 90% killed* Cotton . . . . . . . . . . . 100% healthy. . . . 100% helathy. . . . 100% healthy. . . . 100% healthy Squash . . . . . . . . . .. 81% killed* ... 92% killed* . . . . 78% killed* . . . . 91% killed* Cowpeas . . . . . . . . . . 100% healthy 100% healthy . . 100% healthy. . . . 100% healthy Watermelons . . . . . . 100% healthy 100% healthy . 100% healthy. . . . 100% healthy Gourd . . . . . . . . . . . . 100% healthy. . . 100% healthy.. . . 100% healthy . . 100% healthy Cotton . . . . . . . . . . . 100% he thy. . . 100% healthy. . . . 100% healthy . . 100% healthy Watermelons . . . . . . 100% healthy . . 100% healthy. -. . . 1 ant died** . . 3 plants died** Cowpeas. . . . . . . 100% healthy. . . 100% healthy. . . . 100% healthy . . 100% healthy Pumpkin . . . . . . . .. 100% he thy. . . 100% healthy.. . . 100% he t v . . 100% healthy Cucumber . . . . . . . . 100% healthy . .'100% healthy. . . . 100% healthy . . 100% healthy Watermelons . . . . . . 100% healthy . . 100% healthy.. . . 100% healthy . . 2 plants died** Okra . . . . . . . . . . . . . 100% healthy. . 100% healthy. . . . 100% healthy . 2 plants died** Cashaw. . . kil d* . . . . 81% killed* . . . . 82% killed* 96% killed* Cahtalonpe . . . . . . . 100% healthy. . . . 100% healthy.. . . 100% healthy. . . . 100% healthy Cashaw. . .. . . . . . .. 72% killed* .... 77% killed* . . .. 73% killed* .... 92% killed* Irish Potatoes. . . .. 100% healthy. . . . 100% healthy. . . . 100% healthy. . .. 100% healthy Tomatoes . . . . . . . . . 100% healthy.. . . 100% healthy. . . . 100% healthy. . . .|100% healthy Earner or A SIoK Son. ON THE SQUASH AND CASHAW. In studying 'I‘able 2, we find that during the four seasons? trials, both the squash and the cashaw which grew on a sick soil persistently died from a Fusarium Wilt which only attacked these two hosts. How- ever, in this same field, neither the Watermelon, the cucumber, the canta- loupe, the pumpkin, the gourd, or any other of the hosts mentioned in Table 2 Was affected by the squash and cashaw Wilt. This conclusively proves that the wilt of the squash and cashaw is in no Way related to the Watermelon Wilt. During 191.6, 1917, and 1918 the watermelons in field B remained healthy. However, in 1919 a very small number of Watermelon plants died from the typical watermelon wilt); In this case, evidently, the Watermelon Wilt fungus was eventually introduced in the wilt-infected squash field. From the results obtained in plots A and B it is evident that it is practically safe to grow squashes and cashaws in the same field Where watermelons die from Watermelon Fusarium ‘wilt. The same is true also in growing watermelons in a Wilt-infectced squash land. *The fungus isolated from the dead squash and cashaw plants was identical with Fusarium cucurbitae. **The fungus isolated from the dead watermelon plants was identical with F. niveum. tIsolation cultures yielded Fusarium mtieizm which upon inoculation into healthy watermelon seedlings caused them to die. 8 TEXAS AGRICULTURAL EXPERIMENT STATION. Table -3.-—Virgin soil planted in Tom Watson watermelon. Cultural 191s 1917 l 191s l 1919 treatment l l l l Olfi V1116; dand 100% healthy... . 1' plant died froml% of 1%died from. cu s wor e un- der at end season. 8% died from l Fusarium wilt Manure alone.——- l l l i l l I l l Fusarium wilt l Fusarium wilt Fertilizer_alone.—- l i l ‘ _ Old vines and l100% healthy. . . . 100% healthy. . . .12 plants died from, lé of 1% died from culls worked un- ~ Fusarium wilt Fusarium wilt der‘ at end of 1 l l l $638011. l M01311 or INFECTION OF l-HRGIN LANDS. In studying Table 3, it will be noticed that on a virgin land where manure was applied. and where watermelons were grown there for four consecutive seasons, only one diseased Watermelon appeared during the second season in 1917. During the third year the wilt increased to one-half of one per cent., and the fourth year, in 1919, the wilt was prevalent to the extent of 8 per cent. On the other hand, where fer- tilizer alone was applied to a virgin land, two watermelon plants died from wilt during the third summer in 1918 and only one-half of one per cent. during the fourth season in 1919. This, then, indicates that manure favors earlier infection and the more rapid spread of the water- melon wilt in a virgin land than is the case where commercial fertilizers alone are used. It is further evident from Table 3 that continuous cropping of watermelons on a virgin land will soon introduce the Fusarium wilt. If the practice of continuous growing of watermelons on that land is persisted, that land will become sick to and unfit for watermelons. This fact has actually happened in many counties (espe- cially Waller County), where, in numerous instances, watermelons were grown consecutively on the same land for twenty years or more. This resulted in the wholesale infection of the land, thus making watermelon culture precarious and unprofitable. Table 4.-—\Vatermelon Fusarium sick soil, 3 year rotation. 1917 ' 1917 1917 l . l _ 1-3 acre in corn. Goodcrop. ll-3 acrein oats and cowpeas. l1-3_acre in waterrnelons, 93% l Good crops. l killed by Fusarium wilt. 1918 1918 1918 l l 1-3 acre i_n waterrnelons._ 40% l 1-3 acre in corn. Good crop. l-3 acre in oats and cowpeas. died from Fusarium wilt. l Good crops. 1919 l 1919 l - 1919 1-3 acre oats and cowpeas. l1-3 acre in watermelonsfi“ l1-3 acre in corn. Good crop. Good crops. l l *In May 20, 1919, a careful count showed 23% watermelon plants died from watermelon wilt. By June 10, 1919, and owing to BX_C€SSlV€_ rains most of the watermelon plants were drowned out (see also Fig. 9). This made it impossible to complete the year’s work in that plot. ~ WILTS or WATERMELON AND RELATED Caors. .9 Earner or Itoriirrox ox S101; LAND. In studying Table 4, it is seen that a three-year rotation on a badly infected watermelon sick soil was instrumental in reducing the wilt the third season from 93 to e10 per cent., and the fourth season to 30 per cent. Unfortunately, however, during the fourth season (the summer of 1919) the l1eavy' rains during May and June (see Fig. 9) drowned out the field the latter part of the season, so that complete data could not be obtained. It was evident, however, that a three-year rotation consider- ably reduced the amount of wilt on infected land. Table 5.—-Virgin land, 3 year rotation. 1917 1918 1919 1-3 acre in corn. Good crop. 1-3 acre in oats and cowpeas. 1-3 acre in watermelon. Good I Good crops. crop, no Fusarium wilt. 1917 t 1918 1919 1-3 acre in watermelon. Good <1-3 acre in corn. Good crops. 1-3 acre in oats and cowpeas. crop, no Fusarium wilt. Good crops. 1917 1918 1919 1-3 acre in oats and cowpeas. 31-3 acre in watermelons. 1-3 acre in corn. EFFECT or ROTATION ION HEALTHY VIRGIN LAND. In studying Table 5, one sees that on a virgin land, where a three- year rotation has been practiced, no Watermelon wilt appeared during the third season’s culture. This clearly and forcibly brings out the necessity of (1) using virgin lands for watermelons, and (2) of prac- ticing on that land a definite system of rotation in order to keep out the wilt. a ' vllRlETA]. RESISTANCE IN WAmEnMELoNs. In studying Table 6, which is self-explanatory, it Will be seen that of the twenty varieties of watermelons tested, none showed complete resist- ance. Furthermore, but very few came in the class B, while most of them were over 90 per cent. susceptible to wilt (see Fig. 1a). Similar re- sults were obtained by Orton(16), who tried out 100 American and Russian varieties and not any of them proved to be resistant. It is probable, however, that through selection of individual resistant hills, a resistant strain may be developed. Because of the dry seasons of 1917 and 1918 the selected hills in the field failed to produce fruit. Selec- tions of resistant hills were made, however, during the season of 1919 and enough seed saved for future work. It is probable that by cross- ing any of the watermelon varieties with the citron, which is immune to wilt, one may obtain a resistant strain more expeditiously. This was actually done by Orton(16), who crossed the citron with the Georgia Rattlesnake. This strain tested out at Prairie View, Texas, proved to be 100 per cent. resistant but of little value because of its thick rind and spherical shape. The average watermelon growers in Texas prefer 1O TEXAS AGRICULTURAL EXPERIMENT STATION. e882: $8 .5>O.lU 63009:: $00 fiY/OILM ézxmmmuk §oo~| . . . IwUOQ/W G-Sbnm . . . . . . . . . . . . . . . .®Q@h Em‘? .O_HHT~Q WQQ> . “Awm. . . . . . . . . . . . . . . . WQOA . . . . .v:~Nm . . . . . . . . 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U IIASQU . . . . . . . 1.30m . . . . . . . . . . . . ..QWM%%U E2155 wcw wzom 11.9: mm . . . . . . . . . . . . Iwcsom 1138mm . . . . . . ... . .022 Sxwsw U . . . . . .hOOfi% . . . . . . . . . mvOOU na-mz/ GNP: Fbaivfi “Owim .. . . . UQN . . . . . . . . . . . . . . . . . . . .wQO1.~ .. . . .xiflm ...mm0~h0Uh* MO Eflwku Qbw *3 . . . . . . goon Iluoozfm mix. . . . . . . . . . . . , . 525.0 .55 was 23in >$> . . . 1w“: mm 682E E52 3 wcoq . . . . 453w . . . . . . . . . 42.3w suEoi ommwmm. o» @2232. . vat we :22: .3 £399. vuzmgmwmvfl wEmQEm po>m7~ £35 we 0.51am. Ecmamumconv Qmsmmo? :22: ._o unmsm Mo 0.532 .332; .6 QENZ o m$>< J13. Efizpmmsh Ow moioi?» coiEhfimB MO QOGNQmWmOMWIAV 0~£flbw FIGURE 1. a. Watermelon sick field planted in 2O varieties of watermelons, nearly all of them wiped out by Fusarium wilt. This is indicated by the bareness of the field. The rows remaining healthy are okra, cowpeas, Irish potatoes, tomatoes and cabbage. b. .Early stages of squash wilt. . c. Watermelon seedlings killed by FUSUTTWHTI» citrulli. TEXAS AGRICULTURAL EXPERIMENT STATION. I 12 the Tom Watson variety; hence it might be crossed with the citron t0 obtain quality and resistance. This is planned to be carried o-ut by us in the future. are far superior in flavor to the Tom Watson; however, the latter variety has been well introduced, and, besides, it is a good shipper and is packed economically in the cars when shipped long distances. VARIETAL RnsIsrANcE 1x" OTHER Cuotmsrrs. Of the ri1any' squash varieties tested, the Mammoth White Bush, Yel- low Summer Crookneck, New Giant, Summer Crookneck, Long White Marrow, and the Boston Marrow seem to possess considerable resistance. Of the other squash varieties tested which were practically‘ 100 per cent- susceptible to wilt may be mentioned the Early NVhite Scalloped Bush, “Bush” Fordhook, New Red or Golden Hubbard, Chicago Warted Hub- bard, Mammoth Chili, Essex Hybrid, Mammoth Whale, Delicious, Deli"- cate, Pike’s Peak, Yellow Pathy Pan, and Mammoth Yellow Bush. It is worthy of note that of the seven varieties of pumpkin tested all showed to be highly resistant to Fusarium wilt. Of the varieties tested may be mentioned Big Tom or Imported Large Field PumpkimLarge Cheese Kentucky Field, Small Sugar, Genuine Mammoth, Burpee’s Golden Oblong, Japanese Pumpkin, andlBurpee’s Quaker Pie. Like the pumpkin, all the varieties of gourds tested were highly re- sistant to Fusariuni wilt. This is the case for the cultivated as Well as for the ornamental varieties. In Texas there seems to be an inherent prejudice against eating gourds. It is true that because of unpleasant taste most of the edible varieties are not well suited for cooking; how- ever, the variety “Sugar Through” (Fig. 2a and b) obtained from Burpee’s Seed Company prov-ed not only resistant to wilt but also highly adapted to cooking and when prepared properly, cannot be distinguished in taste from any of the superior varieties of squashes, pumpkins, or cashaws. In fact. the domestic science department of Praivie View Normal College cocked the “Sugar Through” gourd in various ways and served it to many visitors and to the students without their being told what ‘it was. The dish was relished as though it were pumpkin, squash, or cashaw. “Sugar Through” gourd was also cooked by several farmers as well as by the writer at his home without telling what it was and the fruit was consumed and taken for squash. Furthermore, this gourd is well adapted for canning purposes as well as for pies. On account of the prolific nature of the “Sugar Through” variety of gourd and the size of its fruit, it could take an important place with the pumpkin or any other cucurbit both as a food for humans and for stock. This variety is, therefore, strongly recommended to the people of Texas, I especially in localities where the land is badly infected with Fusarium wilt. It true that there are many watermelon varieties which i W11xi‘s OF “TATITERMELON AXD Rumnyren CRoPs. 13 b. -~ -.,_,,...,,....-.-~.v__ FIGURE 2. a. ‘(Sugar Through Gourd” growing in a watermelon sick soil. “Sugar Through Gourd” growing in a squash sick soil, exhibiting in both ‘ cases 100 per cent resistance. 14 lfiixas i-Xeiircr-Irrrnar. EXPERIMENT Sixrriox. In addition to the “Sugar 'l‘lirotigh” gourd the following varieties of gourd have been tested and proved entirely immune to Fusarium wilt: White Egg, Dipper, Dish Cloth or Chuffa, Orange, Apple, Spoon, and Calabash. Four seasons of field trials seem to indicate that the cucumber is not host to the Fusarium Wilts which attack the watermelon 0r the squash. Cucumbers are frequently subject to the same bacterial blight (Bacillus trachieiplziilus Eur. Sm.) which affects eantaloupcs. Cultures made from freshly wilted cucumber plants yielded in most cases a pure growth of B. tracheiphilus. On the other hand various Fusaria were often iso- lated from infected cucumber plants which had wilted and died long since. These fungi resembled in no way the pathogenic Fusaria of the watermelon and squash wilts. Furthermore, cucumbers grown in in- fected squash or watermelon sick soil remained healthy during the entire season. The same also holds true for the cantaloupe (Fig. 3a), which in Texas is frequently wiped out not by Fusarium wilt but by bacterial blight (Bacillus tracheiphllus) or by Sclcrotium rolfsii Sacc. Stone(23) reports a serious vascular disease of greenhouse cucumbers and attrib- utes it to a species of Pltisarium. It is probable, however, that he either dealt with a new disease or vrith bacteria] blight (Bacillus iracheipltilus), and that the Fusarium was only a secondary invader. Lewis(l3) re- ports the following Fusaria to cause a rot on cucumber fruit: Fusanium» orthoceras, F. reticulatum, and F. argillacezl~m.. In Texas, however, we have not met with any of these Fusarizt on the cucumber. Table 7.—Cowpea Fusarium sick soil, Robertson’s farm. Host 1916 1917 1918 1919 Cowpea . . . . . . . . .. 79% killed* . . .. 76% killed* . . . . 83% killed* . . . . 86% killed* Squash . . . . . . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy.. . . 100% healthy Cotton . . . . . . . . . . . 100% healthy.. . . 100% healthy. . . . 100% healthy. . . . 100% healthy Cowpea . . . . . . . . . . 82% killed* . . .. 79% killed* . . .. 76% killed* . . .. 82% killed* Okra . . . . . . . . . . . .. 38% k1lled* . . .. 33% k1lled** .. .. 20% k1ll6d* . . .. 29% k1lled** Cotton . . . . . . . . . . . 100% healthy. . . . 100% healthy . 100% healthy.. . . 100% healthy Watermelon . . . . . . 100% healthy. . . . 100% healthy 100% healthy . . 100% healthy Squash . . . . . . . . . . . 100% healthy. . . . 100% healthy 100% healthy... . 100% healthy. . . . Cashaw . . . . . . . . . . 100% healthy. . 100% healthy 100% healthy . . 100% healthy Cowpea . . . . . . . . .. 81% k1lled** .... 78% k1lled** .... 83% kil * .. 9117 killed* Okra . . . . . . . . . . . .. 22% k1lled** . . . 36% k1lled** . .. 24% k1lled** .. 18% k1lled** Cotton . . . . . . . . . .. 100% healthy. . .. 100% healthy. . . . 100% healthy... . 100% healthy Watermelon . . . . . . 100% healthy. . . . 100% healthy. . . . 100% healthy. . . . 100% healthy Okra . . . . . . . . . . . .. 10% k1lled** . . . 36% ki1led* .. . . 29% k1lled** . .. 21% k1lled** In studying ‘died badly in the field from Fusa. of 1916, 1917, 1918, and 1919. lphlla F. malvacearum. TProved by isolation cultures and artificial inoculation on healthy cowpea plants in the l1 aboratory. A NEW OKRA Wnrr. Table 7' it will be seen that cowpeas (var. Lady Finger), rlum tra-clteiphilat during the seasons On the other hand, the same wilt did _*Isolations made from infected cowpea plants yielded pure cultures of Fusarium lrachei- **Isolations made from infected okra plants yielded not Fusarium vasinfectum, but WILTS OF \V.»xTER.\1;EI.0N AND RELATED CROPs. FIGURE 3. a. Row of cantaloupes growing in a squash sick field, resistant 100 per cent. b. Squash plant dying from Fusarium wilt in sanle field as a. ~ mained healthy. 16 ‘fnxas AGRIeULTURAI. EXPERIMENT Srxrron. not attack the squash, the watermelon, the cashaw, the cotton, the tomato, _ the cabbage Which were planted during the four seasons in the sick cowpea fiel.d. However, the only other crop which was dying from a Fusarium Wilt was the okra. This was observed during the summer seasons of 1916, 191T, 1918, and 1919. It should be noticed that the Fusarium wilt which killed the okra at the Robertson farm did not affect the cotton. From experiments referred to later (p. 20), it will _ be seen that this okra wilt is different from the common wilt of okra and as proved by CarpenterQL) is attributed to Fusarium vasinfectum, which also attacks the cotton. As will be seen on page 20 the okra wilt at the Robertson farm was found to be induced by an apparently new species of Fusarium, which for convenience was named FusarIiunz malvacea/mzm, Taub. No attempt has as yet been made to determine the prevalence and distribution of this new okra xvilt in Texas. B. GREENHOUSE EXPERIMENTS. In connection with, and in order to duplicate the field experiments, a large series of tests were started in the greenhouse during 1917 and 1918. The experiments WQTG arranged as follows: EXPERIMENT 1. One bench, one-half of which was filled with sick soil, brought from. a watermelon sick field from Prairie View, Texas, was designated as plot 1. The other half of the bench which was separated by a solid partition was filled with sick soil taken from a sick squash field from Prairie View, Texas, and designated as plot 2. Roth of these plots were planted with seeds* of watermelon, squash. pumpkin, okra, gourd, and cowpeas. The seeds were planted in rows. 100 to a row. Germination proceeded nor- mally within six to twelve days after sowing. After ten days growth, 80 per cent of the watermelon seedlings in plot 1 died from Fusarium wilt (Fig. 4b). On the other hand, all the other hosts in this plot re- In plot 2, 65 per cent. of the squash plants died from Fusarium wilt (Blig. 4a) while the xvatermelon and the other hosts re- mained healthy. This test, carried out for two years, practically yielded similar results, thus proving‘ that the watermelon sick soil contained Fusarium of watermelon wilt which killed the watermelon, but none of the other cucurbits or the okra or cowpea. Likewise, the squash sick soil whichwas infected with Fusarium wilt was killing the squash only, but none of the other cueurbits nor the okra and cowpea. In order to definitely determine whether the watermelon and squash seedlings in plots 1 and 2 were killed by Fusaria, isolation cultures were made of freshly wilted plants of both hosts, using all the known aseptic rules. Pure cultures of Fusaria were obtained from both the wilted watermelon seedlings from plot 1 and from the squash seedlings from plot 2. The ' *Before planting, the seeds were soaked for one minute in a 1-2000 corrosive sublimate solution. then rinsed in sterilized water. ii.- . _. i: b. .;._»..v..b|~i.14.v.7-x.4-e:-'7fw.mnfikJix 1.1L. wamiaaaan"aa~mm~.i in)‘. m he... -l a . .s.. _ Wrrxrs or \V-»\'rn11l\r;ar,oX AND RELATED Cnors. FIGURE 4. a. Squash sick soil in the greenhouse, to the right and middle only, squash plants die from Fusarium wilt; t0 the left, watermelon plants remain healthy. b. Watermelon sick soil in the greenhouse, t0 the right squash plants re- main healthy; to the left, watermelon seedlings badl C". Plate culture of F. cvitrulli on potato agar. d. Plate culture of F. niqeuvn on potato agar. Squash bug. y die from Fusarium wilt. e f. Cucumber striped beetle. mr-riers of “Yatermelon and squash wilt.) g. Lady bug. -(e. to g., all l7 18 iucxp-is AoR1cL'1.'ri;n.iL hXPERIMENT bipyriox. pure culture of lflisziriiini obtainerl from the xvaternielon seedlings was then inoculated in sterilized soil which was planted to healthy disinfected Watermelon seed. Likewise the pure culture of Fusarium originally iso- lated from the squash wilted seedlings of plot 2 was inoculated in the pots with sterilized soil and planted to squash. Within fifteen days the watermelon seedlings and later during blossoming the ‘squash plants were killed by their respective Ifusaria inoculated in the pots. In each case, whenever infection became apparent the causal organisms were recovered again. A » EXPERIMENT 2. ARTIFICIAL Son. Inrncrron. Healthy soil was secured and filled in ten 5-inch pots, both soil and pots being twice steam sterilized for two hours at 20 lbs. pressure. Three pots of these were inoculated* with a pure culture of Fusarium obtained from a wilting watermelon stem- and two were left as checks. These five pots were then planted with healthy disinfected squash seeds. Of the remaining five pots, three were inoculated with a pure culture of Fusarium which was originally isolated from wilted squash plants and two were left as checks. These five pots were then planted with ' healthy disinfected seed of watermelon. The seedlings in the ten pots all germinated and both squash and watermelon plants grew and re- mained healthy during four months in the greenhouse without ever ex- hibiting signs of wilt. On the other hand, watermelon seedlings soon wilted when healthy watermelon seeds were planted in the pots inocu- lated with watermelon Fusarium. clusively proved that both squash and watermelon Wilts are distinct and that it is possible to grow healthy watermelons in a squash sick land provided the watermelon Fusarium is kept out. Likewise, it is possible to grow healthy squash in a sick watermelon field provided the squash ' Fusarium is kept out. Exrunnrnnr 8. PATHOGENICITY or FUSARIA STUDIED. To further prove the pathogcnicituvr of the Fusaria here considered, 264- 5-inch pots were filled with good watermelon soil which was shipped in from Prairie View. The pots and soil were sterilized in ‘the auto- clave for three hours at 15 lbs. pressure. might be in the soil were killed. To further make certain of the absence of microorganisms, isolations were made from the soil, the method used being indicated on page 25. No growth whatever appeared from the 5; platings of the steamed soil, proving that no microorganisms remained. alive there. The 264- pots were then divided into eleven series, nine of 4‘ The elev- f which were inoculated with eight distinct species of Fusaria. enth series was used as a check. Three pots were used for each species *The method of inoculation consisted in introducing in the soil pure cultures of solution, then rinsed in sterilized water. From these experiments it was con-- This was done twice with an. . interval of two clays so as to make sure that any microorganisms that ~_ A . .. ..._..‘_u..\...-.am~_ i»; ~(u.1..-i.. WILTs or “lirERirELoN AND RELATED Onors. 19 of lclusarium, making a total of 240 inoculated pots and 2% of checks. The following organisms were used for inoculation: F. nivetun, F. Ctffttllt, and F. yioole-nsils, all three of which ‘ivere isolated from diseased Watermelon plants; F. czacurbitae was originally isolated from diseased squash plants; F. vasinfectzuiz was isolated from diseased cotton plants; F. malracearam- (Fig. 8g). from diseased okra plants from Robertson’s farm; F. tracheigi/tiltz Was isolated from cowpea; F. coregltttinarts was isolated from diseased cabbage plants; F. Zycopcrsici was isolated from diseased tomato plants; F. Zathiyri from diseased sweet pea plants. The method of inoculation consisted in breaking up in sterilized water young iive-days-old cultures of each particular Fusariuin and then worked in With the soil. After inoculation, the pots Were allowed to stand two days, after which time every pot in all the series, including the checks, was planted alike with five seeds of each of watermelon, squash, cotton, okra, cowpea, tomatoes, cabbage, and sweet pea (Fig. 5a and c). The resultsiof these experiments are indicated in Table 8, which is self- explanatory. It thus seen that pure cultures of-F. niveum, F. citrulli and F. poolemsis were all capable of producing a wilt disease of water- melon. None of these organisms, however, were capable of producing a wilt on squash, cotton, okra, cowpea, tomato, cabbage, or sweet pea. Likewise, F. cuc1ii'bitae,’*‘ originally isolated from the squash, was only _ capable of infecting the squash and the cashaw‘, but none of the other hosts, as shown in Table 8. The same was also true for F. vasinfectumi,‘ which has proved to be parasitic on the cotton and the okra only. Fur- thermore, F. maJ/vacear/‘zton, originally isolated from okra plants, proved to be a Weak parasite on okra but was unable to infect cotton or any of the other hosts indicated in Table 8. In a further study of Table 8, it will be seen that F. tracheiplznlla is parasitic on the cowpea only, F. congluiinansa parasitic on the cabbage only, F. lycopersici parasitic on the tomato and F. Zafliy/ri parasitic on the sweet pea only. Table 8.-Greenhouse pot inoculationsit Period of Percentage Pot Series No. Species and Strain No. Host Used incubation of dying (days) No. l, including 24 pots. . Fusarium niveum, 1071" Waterme‘0n. . . . . 1O l 82 m do** . . . . . . . . . . . . . . Squas . . . . . . . . . . O O _ s do** . . . . . . . . . . . . .. Cotton . . . . . . . . .. O I 0 ‘ do** . . . . . . . . . . . . . . Okra . . . . . . . . . . . . O u O do** . . . . . . . . . . . . ..iCowpea . . . . . . . .. 0 1 O i. do . . . . . . . . . . . . . . ..|Tomatoes....... 0 l O I i do** . . . . . . . . . . . . .. Cabbage... ._... 0 o i do** . . . . . . .._ . . . . .. Sweetpea . . . . . . .. O 1 » 0 *Fusarium cucurbijae seerrs to be distinct and different fromF. helianlhj, F. reticulalum, and F. culmoru m, which Lewis (l3) reported to produce a rot on squash fruitf. TRepreseriting results of average of two years experiments. . iFusarium citrulli and F. poolensfs of pot series No. 2 and 3 behaved like F. niveum, that is, they produced disease on watermelon, but not on squash. cotton, okra, cowpea, t omato, cabbage or sweet peas. i **No infection took place when fungus was placed in soil, nor_when abrasian was made on stem end or on roots and not even when fungus mycelium was inserted in stems or roots. **No infection took p ace when fungus was p‘aced in soil, 20 PExA-s AGRICULTURAL EXPERIMENT STATION. Table 8.—-(Continued). x; l ' . _ _Period of Percentage Pot Series No. Species and Strain No. \ Host Used. 1n(cé1bat)ion of dying ays No. 4, including 24 pots. . F. cucurbitae, 103 . . . . . . Squash . . . . . . . . . . 41 67 do** . . . . . . . . . . . . . . Watermelon. . . . . O 0 do** . . . . . . . . . . . . . . kra . . . . . . . . . . . . 0 O do** . . . . . . . . . . . . . . Cotton . . . . . . . . .. O 0 do** . . . . . . . . . . . . .. Cowpea . . . . . . . .. 0 0 do** . . . . . . . . . . . . . . Tomato . . . . . . . . . 0 0 do**. . . . . . . . . .. Cabbage . . . . . . .. O 0 do**. . .’ . . . . . . . . . . . Sweet pea . . . . . . . 0 O N0. 5, including 24 pots. .‘ F. vasinfectum, 101*. . . . Cotton . . . . . . . . . . 32 78 do** . . . . . . . . . . . . . . ra . . . . . . . . . . . . 40 62 do** . . . . . . . . . . . . . . Watermelon. . . . . O 0 do** . . . . . . . . . . . . .. Squ; sh . . . . . . . . . . O 0 do** . . . . . . . . . . . . . . Cowpea . . . . . . . .. 0 ~ 0 do** . . . . . . . . . . . . . . Tomato . . . . . . . .. 0 0 do** . . . . . . . . . . . . . . Cabbage . . . . . . . . O O do** . . . . . . . . . . . . . . Sweet pea . . . . . . . 0 O No. 6, including 24 pots. . F. malvacearum, 102*.. . Okra . . . . . . . . . . . . 14 a 57 do** . . . . . . . . . . . . . . Cottonl . . . . . . . 0 0 do** . . . . . . . . . . . . . . Watermelon. . . . . 0 O do** . . . . . . . . . . . . . . Squash . . . . . . . . . . O 0 do** . . . . . . . . . . . . . . Cowpea . . . . . . . . . 0 0 do** . . . . . . . . . . . . . . Tomato . . . . . . . . . 0 0 do** . . . . . . . . . . . . . . Cabbage . . . . . . . . 0 0 do** . . . . . . . . . . . . . . Sweet pea . . . . . . . 0 0 No. 7, including 24 pots. . F. tracheiphila, 103. . . . . Cowpea . . . . . . . . . 24 83 do . . . . . . . . . . . . . . . . kra . . . . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Cotton . . . . . . . . . . 0 0 _ do . . . . . . . . . . . . . . . . Tomato . . . . . . . . . 0 O do . . . . . . . . . . . . . . . . Cabbage . . . . . . . . O 0 do . . . . . . . . . . . . . . . . Watermelon. . . . . 0 0 do . . . . . . . . . . . . . . .. Sweet pea . . . . . .. 0 0 do . . . . . . . . . . . . . . . . Squash . . . . . . . . . . 0 O No. 8, including 24 pots. . F. conglutinans. 100. . . . Cabbage . . . . . . . . 15 75 . do . . . . . . . . . . . . . . . . Tomato . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Cowpea . . . . . . . . . O 0 do . . . . . . . . . . . . . . . . Okra . . . . . . . . . . . . O 0 do . . . . . . . . . . . . . . . . Cotton . . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . .' Watermelon. . . . . 0 0 do . . . . . . . . . . . . . . . . Squash . . . . . . . . . . O 0 - do . . . . . . . . . . . . . . . . Sweet pea . . . . . . . 0 0 No. 9, including 24 pots. . F. lycopersici, 111*. . . . . Tomato . . . . . . . . . 37 43 do . . . . . . . . . . . . . . .. Cabbage . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Cowpea . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Okra . . . . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Cotton . . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Watermelon. . . .. 0 0 do . . . . . . . . . . . . . . . . Squash . . . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Sweet pea . . . . . . . 0 0 No. 10, including 24 pots. F. lathyri . . . . . . . . . . . . . Sweet pea . . . . . . . 12 79 do . . . . . . . . . . . . . . . . Tomato . . . . . . . . . O 0 do . . . . . . . . . . . . . . . . Cabbage . . . . . . . . 0 0 do . . . . . . . . . . . . . . . . Cowpea . . . . . . . . . O 0 do . . . . . . . . . . . . . . .. kra............ 0 0 do . . . . . . . . . . . . . . .. Cotton . . . . . . . . .. O ‘t 0 do. , . . . . . . . . . . . Watermelon. . . .. O 0 do . . . . . . . . . . . . . . . . Squash . . . . . . . . . . 0 '0 No. 11, including 24 pots. Check . . . . . . . . . . . . . . . . . Watermelon. . . . . Noinoculai All healthy tron. do . . . . . . . . . . . . . . ..Squash.......... do. d0 do . . . . . . . . . . . . . . .. Cotton . . . . . . . . .. do. do do . . . . . . . . . . . . . . ..Okra............ do. do do . . . . . . . . . . . . . . . . Cowpea. .. . . . . . .. do. d0 do . . . . . . . . . . . . . . ..Tomato.......... do. d0 do . . . . . . . . . . . . . . .. Cabbage . . . . . . .. do. do do . . . . . . . . . . . . . . .. Sweet pea . . . . . . . do. do *N o infection took place when fungus was inoculated in the soil, but only through abrasian at the stem end or 11'] the roots. nor when abrasian was made ‘on stem end or on roots and not even when fungus mycelium was inserted in stems or roots. WILtrs or WATERMELON AND RELATED ORoPs. 21 As a result of these soil inoculations it was thought that the reason perhaps certain hosts, as indicated in Table 8, were susceptible only to cer- tain specific Fusaria, ivas probably due to the fact that the inoculurn was put in the soil Without injuring the roots of the hosts. Accordingly, and after a period of six weeks, the various hosts which did not become sus- ‘ceptible to infection by the Fusaria, as shown in Table 8, were bruised at the stem ends and roots. This was done by scratching deeply with a sterilized knife and yet no infection took place, thus further proving that certain Fusaria can attack only specific hosts and no others and this restriction to host is not necessarily influenced by wounds. Not being content with the above results we planned another experiment, as follows: Tlhirtjv-two 5-inch pots were filled with sandy loam soil and Table 9.—Greenhouse pot experiments?“ _ Kind of Host» N0. Kind of Fungus _Result _of Series and pot No. planted in pots pot inoculated inoculation A. 1, 2, 3, 4 . . . . . . . . . Watermelon. . . . . 1 Fusarium_niveum.. . . . 5097 dead** 2 F. cucurbitae . . . . . . .. All healthy 3 F. vasinfectum . . . . . . . All healthy 4 Cher-k. . . . . . . . . . . . . . All healthy B. 5, 6, 7, 8 . . . . . . . . . Squash . . . . . . . . . . 5 F. ciicurbitae . . . . . . . . 287 dead** 6 F. niveum . . . . . . . . . . . All healthy 7 F. vasinfectum . . . . . . . All healthy 8 Check . . . . . . . . . . . . . . . All healthy C. 9, 10, 11, 12 . . . . . . Cotton . . . . . . . . . . 9 F. vasinfectum . . . . . . . 417 dead** 1O F niveum . . . . . . . . . . . All healthy 11 F. cucurbitae . . . . . . . . All healthy 12 Check . . . . . . . . . . . . . . . All healthy D. 13, 14, 15, 16. . . . . Okra . . . . . . . . . . . . 13 F. Vasin‘ectum . . . . . .. 18% dead** 14 F. malvacearum . . . . .. 9'7 dead** 15 F. niveum . . . . . . . . . . . All healthy 16 heck . . . . . . . . . . . . . . . All healthy E. 17, 18, 19, 20. . . . . Cowpea . . . . . . . . . 17 F. niveum. ._ . . . . . . . .. All healthy 18 F. tracheiphila . . . . . . . 81% dead** 19 F. Vasinfectum . . . . . . . All healthy 20 Check . . . . . . . . . . . . . . . All healthy F. 21, 22, 23, 24. . . . . Tomato . . . . . . . . . 21 F. Iycopersici . . . . . . . . 73% dead** . 22 F. niveum . . . . . . . . . . . All healthy 23 F vasinfectum . . . . . . . All healthy ' 24 Check . . . . . . . . . . . . . . . All healthy G. 25, 26, 27, 28. . . . . Cabbage . . . . . . . . 25 F conglutinans . . . . . . 95% dead** 26 F. niveum . . . . . . . . . . . All healthy 27 F. vasinfectum . . . . . . . All healthy 28 heck . . . . . . . . . . . . . . . All healthy H. 29, 30, 31, 32. . . . . Sweet pea . . . . . . . 29 F. lathyri.. .. . . . . . . .. 30% dead** 30 F. niveum . . . . . . . . . . . All healthy 31 F. vasinfectuni . . . . . . . All healthy 32 Check . . . . . . . . . . . . . . . All healthy steam sterilized as indicated on page 18. in eight series, each series consisting of four pots. The pots were then divided The pots in each series were planted as indicated in Table 9, ten seeds being used to each pot. The seeds in all the pots came up regularly and the plants were allowed to grow undisturbed for ten weeks. The pots in this experi- ment were all watered with sterilized water to prevent accidental in- *Average results of two years experiments. **The fungus was recovered from the infected plants. I TEXAS AtmitfvUrifiin, EX1>FRIM1<:;\"1‘ STATTUX. FIGURE 5. a. From left to 'right—pot 100 inoculated with Fusariunz congZut/inaizs in which cabbage seedlings are dying while other hosts remain healthy. Pot 106 inoculated with F. citrulli, all watermelon seedlings dying, but other hosts remain healthy. Third pot with no- number, inoculated with F. niveum, watermelon seedlings dying, all other hosts healthy. Pot 111 inoculated with F. Zycopersici, tomato plants wilting, all other hosts re- maining healthy. Four series of pots in the greenhouse, first row at bottom. Pots 105 WiLrs 0F WivrERiiELoN AND RELATED Liters. 23 and 106 inoculated with F. citrulli, all watermelon seedlings dying. Pot 107 inoculated with I", 1tiveum, and pot 114 inoculated with F. poolensis, watermelon seedlings dying in both. Second row, pot 100 inoculated with F. conglutiiitans, pot 101 inoculated with F. tracheiphila, pot 102 inocu- lated with F. vasinfectum, pot 103 inoculated with F. oacysporum. Third row, pot 104 inoculated with Fusarium from cucumber fruit, pots 108 and 109 inoculated with Fusarium from blossom end rot of watermelon fruit, pot 110 check, no inoculation. Fourth row on top, pot 112A and 111 in- oculated with F. malvaceammn. Notice watermelon seedlings are all healthy in the upper three rows. c. Six pots all inoculated with F. lycopersici. Notice that tomato plants in last pot to the left are all wilting and have lost most of their foliage; on the other hand, the squash, cowpea, watermelon, pumpkin, and cabbage planted in the other pots are all ‘healthy. fection. At the end of ten weeks the plants in each pot were inoculated with Fusarium fungi as indicated in Table 9, the customary ‘check being allowed to each series. The method of inoculation consisted in inserting a copious amount of young, actively growing mycelium at the base of the healthy host through a wound made with a sterilized scalpel. Ster- ilized moistened cotton ivas then applied around the inoculated area and covered with the sterilized soil from the pot and kept damp for two days without, however, placing it under bell jars. The results of these inoculations are shown in Table 9, which is self-explanatory and which further substantiates the results recorded in Table 8. In order to (letermine whether the species-of Fusaria recorded in Table 9 are pathogenic to tubers of Irish potatoes, the following experi- ments were tried: Healthy Irish Cobbler potatoes were secured, care- fully washed and dipped for one minute in a solution of one part cor- rosive sublimate in two thousand parts of water. After this treatment the tubers were rinsed in sterile water to remove all traces of the dis- infectant. The potatoes were then divided into series of three each and in each series two tubers were inoculated with a Fusarium species and the third one left as a check. The Fusaria used in this experiment ivere: F. nicemn, F. malvaceairuinz, F. cuc-urbitaie, F. lycopersicii, F. con- gluii-nansi, F. Zathiyri, and F. orysporum. In thirty days after inocu- lation, F. orcjz/sporuivz. produced a slight rot while all the others failed to cause any infection. o. LABORATORST EXPERIMENTS. In connection xvith field and greenhouse studies of plant pathogens it is, of course, necessary to carry on laboratory experiments. These consisted in: (l) Isolation work; culture work; (3) life history, physiological and morphological studies of the organisms under ob- servation. ISOLATIONS. Experiments have already been referred to on page 18, where actual inoculations were carried out in the greenhouse with pure cultures of the organisms here studied. The sources of isolation of these Fusaria were also indicated on page l8. The method of isolation was as follows: Wilted seedlings or vines were cut with sharp scissors into small pieces 24 a. b. TEXAS AGRICULTURAL EXPERIMENT STATION. \ FIGURE 6. Healthy okra plant growing in same hill of wilted squash plant ‘in field. Plate ‘culture 0t isolation of F. cucurbitae from wilted squash vine. n WILTS or WATERMIELON AND RELATED CRoPs. 25 about one-eighth of an inch in length. These pieces of plant tissue were then rinsed in distilled water, dropped in a test tube and dis- infected for one-half minute in a solution containing equal parts of 1-1000 mercuric chloride and 50 per cent. alcohol. The bichloride solu- tion was poured off and the plant material rinsed five times in sterile water to wash off all traces of the disinfectant. With this method of isolation each host was, of course, done separately. Tubes with agar medium were melted and cooled down to the proper temperature. With a flamed and cooled forceps a piece of the plant material was placed at the mouth of the tube and thoroughly crushed with the forceps and then shaken up ivith the media. The content of the entire tube was then poured in a sterile petri dish and allowed to cool. In order to keep out contamination from bacteria, a drop of 5 per cent. lactic acid was added to each petri plate. As soon as growth appeared, transfers were made to slants in tubes and the resulting pure growth was used for inoculation or study. More than five thousand platings were made from these various hosts here mentioned andin the majority of cases a pure culture of Fusarium was obtained from tissue of wilted water- melon or squash plants, thus showing the association of the Fusariuni with the wilt. The pathogenicity’ of these Fusaria was already shown in Tables 8 and 9. Son. Isonlrrroxrs. It has been previously stated that Fusaria growths were isolated from tissue of wilted roots or vines. It further] became necessary to determine whetheror not the Fusaria-urilt-producing fungi also live in the soil. , Accordingly isolation cultures were made from sick watermelon and squash soils at the following depths: one, three, six, nine, twelve, twenty-- four, thirty-six and forty-eight inches. The method of isolation was as follows: One grain of sick soil was placed in a sterilized eight-ounce baby bottle, to which was added 50 c.c. of sterilized water equivalent to 1/50. The bottle was corked with aTflamed stopper and shaken with an electric-revolving apparatus for thirty minutes. Then with a sterile pipette 1 c.c. of the 1/50 solution was taken out and placed in another sterilized baby bottle which contained 20 c.c. of sterilized water. This was equivalent to 1/ 1000, that is, one gram of soil in 1/1000 c.c. of water. Again with a sterile pipette, 1 c.c. of. the original 1/50 was now put in a baby bottle which contained 2-00 c.c. of sterile water, mak- ing it equivalent to 1/ 100, that is, 1 grain of soil to 14/100 c.c. of water. I Platings were now made by adding 1 c.c. of the 1/ 100 dilution to tubes of melted media and then pouring it in a ‘sterile petri dish. Similarly, the same was done by adding 1 c.c. of the 1/1000 dilution of melted agar and poured in sterile petri dishes to which was added a drop of 5 per cent. lactic acid to inhibit bacterial growth. The plates from 1/100 dilution were marked A and those from_1/1000, B. Over 1000 soil isolation plates were made. No attention or counts were made of any other growth except Fusaria. As soon as the latter appeared they ' were transferred to slants and simultaneously the pathogenicity of some i 26 TEXAS AGRICULTURAL EXPERIMENT STATION. of these organisms tested byinoculating them in pots of sterilesoil and planted with squash or watermelon as the case might be. From these isolations it was determined that vvilt-producing Fusaria from a water- melon sick soil are very abundant t0 a depth of the first t0 the twelfth inch. However, the number of Fusaria colonies decreased with a depth below twelve inches. Finally, at forty-eight inches deep the number of colonies was about 60 per cent. less than in the first twelve inches of soil. The strains of Fusaria isolated from a depth of forty-eight inches were as virulent upon watermelon seedlings as those from the upper twelve inches. Isolations of the same depths as for sick watermelon soil were also made for Iilusarium squash sick soil with nearly similar results. CULTURE Wonk. Anyone who has worked with Fusaria will appreciate the difficulty‘ and the dilemma in which one finds himself when trying to identify these organisms. With our present meager knowledge of the Fusarium group/one is at sea when it comes to classifying or describing new species. At times one is inclined t0 believe that such an undertaking is a hope- less task. The writer agrees with Sherbakotf(20) that it is useless to try out many culture media for Fusaria fungi. Of the large variety’ of media tried those adapted in our work were, therefore, few and con- sisted of potato plugs, cornmeal, and rice agar. The results of the culture work on the Fusaria here studied are shown in Table 10. From the above Table (see also Fig. 8a to j) it is seen that Fusarium citrulli and F. malvacearzlwz belong to the type Discolor, whereas F. nivemn and F. poolensiis are of the Elegans type. The characteristics of the other Fusaria are also indicated in Table 10, which is self-explanatory. ‘As to odor, Carpenter(3), Cronnvell(5), and Woolényveber(25) state that F. raisinfcciuim, F. liTtlChfllijJi/‘Lil/Il, F. ly/c0_7)crsici~ and F. niveum pro- duce none. Tn our work on steamed rice, it was found that this was not always the case. F. nicminz and F. congluiinnns always produced an odor of ripe banana, F. citrulli and F. CZLCILTZH-Jifl/G an odor of strong alcohol, F. tracheiphila an odor of slight fermentation and later of rotting cabbage, F. ly/copcvzsici medium lilac. It is therefore verv doubtful‘ if odor is of any taxonomic value in determining species of Fusaria. Fre- quently a culture seems to have no odor; however, as soon as the mycelium in the test tube or flask is slightly disturbed. its odor is at once lib- crated. The odor is usually strongest when the culture is seven to ten days old, but gradually disappears and is completely gone with age. In our work and as found by others, rice is the best medium for deter- mining color (Fig. 7a to g). T-loyvevcr. the latter can only be studied in young cultures, as color, like odor, generally disappears with age. Some species impart a strong color, which becomes permanent. The color of F. poolemsis, for instance, which is a deep blue, does not change though the cultures become yiery‘ old. Ilsuallv with the disappearance of the color. there is a large amount of water of condensation formed on: .., _.‘ I 27 WILTs 01* \\V.»\1'ER.\II<‘.I.OX AND RELATED Gnors. dm-miv lohxmwomfia. .122 dsohofisc .2» an . . . . . . a _ ti.» moAmfiMflBm o3: mcofim ..m:oS.~a2 xm.wm|om 30h xwbfi “N12: ow QD IE5; >582 uoouuom 3 w>fihon< . . . . . 6Zion< E-zpmmsh i2...“ minuflim dm-Qm . Bmlmb ._wc_.E.$~ .@u."m.~®QOo%~ ~13 ofiwEoP . :02: Eiwwg . . dcwmonm xwmév Bob xwqficm QABm 8. 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AWN @502 3 Q3 was HEEil. ...wu..::.3_ . . . . . . .>._:.._.4 . .=::%..........J. .112 zSzmmF; .\Cm__w@.:5cm , . 5m MWNN dmum xox 1:1. 12:55.. dm .: 23E 4:3 smmzrw. ._o__o..._... "$6.2m . . dcsuon; zmw-mv 3cm 5m §oo~ 3 .5 Jcwwcss< . . . . 5:02 . . . . . . .0502 . . . . . . . . .252 A252... E:_..:~m:..~ 5.23 . égfinmffl ._w:_..E.~o~ . dm .C w..wca_ooflw 5:922:35 . . . .22: mcofim . . dcmwfim xmmrmm omfi 0H QD . . . . . . . diionx» ccw TmEPSfiS . o2???» 0:5 oZioQ< . . . . . . . . r352 isimmPm dJPS um o: dwc: ind-m gobo k wfia wwiwm ‘moo... c205 xow|om “Raw . 295m |QQ mfivofi .3 am d 5:33 335d? we 3S5 . 10E: 65:52 . . xwopoummfl 3 m: oifiaom m . . . . duos .5 25h . . . . . QwEESF . . Iguofiwm mDOaQESZ uvwlsm 0.5mm Esimwsb 2a . . .§.....-@.m 45-9....“ .3525. . . .2. Q . co_oE._o..w>> . . dcwcmn 3E . . écwmflm xooéw “REA 3 QD xmmém “Raw ow QD wcm >EE22=~ . . wuuswwfl . . .mso.$E:Z 3 52w d .84 Gavin Esmbwmsh Efifiwfimm .510 o9»? 22%.» mLw 82.3w m mohoamov mofloccomm mioowfilonm mfiopfiom @062? mzzbouokoag mflxcouchum§ lficmiU duzism mimmzh we mvsmmhowuwamnnvltofi “snap. 28 TEXAS AGRICULTURAL fixPnzanvl RNT S1\'. FIGURE 7. a to d-—~F1ask cultures on rice. a. ’ F. nzfrrnwnz. (i. e to g——PIate cultures rice agar. e. F. \ Fusarium vasinfectuvn. b. F. (1. F. 77I)I)IP7?,SI'»9. \ poolensis. f. F. n/ivezzm. g. citrulli. F. citrulli. \ WILTS OF WATERMELON AND RELATED CRoPs. 29 the sides of the glass as Well as on the surface of the mycelium and later the entire medium becomes soft, the mycelium disintegrates, and the whole mass becomes bathed in a clear vinegar liquid. Lrrn Ilrsronr. In order to determine the life history of Fwsarirzm nireum and Fusariunz cucurbiiae and if possible to discover an ascagenous stage, a large number of dead watermelon and squash vines were collected dur- ing June, 191'? and 1918, and each placed separately 1n a heap in the field and exposed to Weather conditions at Prairie View. Similarly, Wilt-infected watermelons and squash vines were placed in wire cages and exposed to weather conditions in the writer’s home garden. Cul- tures were then madc every month from the/above material. These monthly cultures were started in July, 1917, and in July, 1918, and were continued during August, September, October, November, Decem- ber, January, February, March, April, and May for these two years. In each case, no difficulty was experienced in isolating Fusaria from the watermelon and squash vines from July to December. However, after January the vines were partially decayed and it became very diffi- cult to obtain a satisfactory pure growth. This was especially true with the vines set in a heap in the field, although less so with the vines put away in wire cages; It should be added that the wire cages were set in the garden, exposed to the weather, lying on broken pieces of brick to insure drainage and prevent decay. Drops of 5 per cent. lactic acid added to the media helped in part to exclude large numbers of bac- teria. Fusaria obtained from wintered-over wilted watermelon and squash vines, respectively, were then inoculated into sterilized pots and soil, which were separately planted in watermelon and squash seed. In no ‘case did the Fusarium isolated from wintered watermelon vines fail to infect watermelon seedlings. The same was also true for the Fusarium isolated from urintcr-ecl-ovei‘ squash vines thus proving definitely that the vines from wilted watermelons or squash help to carry over winter the Fusaria wilts of these hosts. When we realize that the average farmer, after picking his melons, abandons his fields until spring, we can readily see that the old watermelon and squash vines, especially in diseased fields, should offer the most favorable means of carrying over from season to season the Fusaria which produce Wilts. Likewise, many watermelon growers, after picking the melons turn the field over to.- cattle. This, no doubt, is a good practice only in healthy fields, as in ’ this case the cattle eat up all vines and culls, at the sam_e time fertiliz- ing the land. On infected land such a practice, however, is objection- able, as the cattle in roaming about actually help to spread the disease by carrying on their hoofs some of the infected soil particles. It is also likely that the wilt organisms may pass unharmed through the digestive tract, as the cattle feed on the diseased vines. Experiments to determine this WGTQ not carried out. Harter and Jones(11) suggest this as a possibility when cattle feed on wilt (Fatsarium conglutinans) 30 TEXAS AGRICULTURAL EXPERIMENT STATION. FIGURE 8. a. Macroconidia of Fmsariuvn vasinfectum. b. Chlamydospores of F. vasmfectum. c and d. Macroconidia and chlzunydnsqwores of F. omysporuvn. e. Micro and‘ macroconidia of F. conglutiazavzs. f. Micro, macroconidia and chlamydospores of F. niveum. g. Micro, macrocondia. and chlamydospores of F. malvacearum. h. Micro, macroconidizi and chlanrvdospores of F. citruZl-i. i. Micro, macroconidia. and chlamydospores of F. poolcnsis. j. Micro, macroconidia and chlamydospores o1.’ F. cucurbitae. WILTs or WVATERMELoN ANn RELATED UIiOPb‘. 31 l ' infected cabbage. As-faras possible infected watermelon or squash vines should not be turned under but should be destroyed. This, of course, will involve extra cost and labor, but no progressive grower will con- sider this an obstacle, especially so where the farm depends to a large extent on the success of the watermelon as a cash crop. To further prove that Fusarium wilt of the watermelon is carried over with infected. vines which are plowed under, the following experi- ment was tried: Several 5-inch pots were filled with good watermelon soil and twice sterilized in the autoclave for three hours under 15 lbs. pressure. When the soil was cooled, several watermelon vines coming from a hill known to be killed by Fusarium and proved so through culture isolation, were worked in the sterilized soil and‘ then covered with a layer of paraffin. These pots were then placed outdoors, at College Station to pass the winter over in the open. Early in the spring, these pots were taken into the laboratory, the parafiin cover re- moved, and healthy watermelon seeds which were first disinfected for one-half minute in a solution of bichloride of mercury of the same strength as described on page 16 were planted in the pots. The seed had gierminated normally but after eight days started to wilt. Isola- tion cultures were made from these wilted seedlings and a Fusarium which corresponded to F. niveunt was also isolated from the soil of these pots. Both" strains of Fusaria when reinoculated into sterilized soil planted with watermelon seeds produced the typical wilt. a This proved that wilted watermelon plants when worked in the soil will help to infect it. It should be added that at no time was an aseogenous stage discovered on wintered-over infected watermelon or squash vines. Neither have we been able to find _the N ecnosnzos-pora vas-inlfecta stage‘ on any of the cucurbits studied. TEMPERATURE STUDIES. It generally concederl that temperature studies both of the air and of the soil are important factors in favoring or retarding the spread of certain important disease-producing organisms which are carried over in the soil, Gilman(]0) has shown the important relationship of tem- perature to cabbage wilt (Fu-sarium. COTI/fIZQL-lfiflélllé’). Likewise Johnson and I-lartman(9) have demonstrated that soil temperature is the most important factor in (letermining the extent of the root rot (Thield/l/‘Tfl basicola) of tobacco In our present work on cucurbit diseases it was necessary to determine whether or not. there exists any relationship be- tween outdoor temperature of the air and that of the soil to the Fusarium wilt of cucurbits. It was also necessary to (letermine the possible effect of these temperatures on the life history of the cucurbit wilt-producing Fusaria. Hence, especially built soil thermometers were secured from the Henry Green Company of Brooklyn, New York. These thermome- ters were placed in the soil to a depth of 1, 3,’ 6, 12, 24, 36, and 48 inches. They were installed in a typical watermelon soil at Prairie View. The thermometers were stuck in the soil in a straight row and at a foot and a half distance from each other. The parts protruding 32 TEXAS AGRICULTURAL EXPERIMENT STATION. I above ground were protected by a cage, the Walls of which consisted of loose ordinary chicken wire. This was done in order to prevent the breaking of the instrumentsby the field workers or by possible roaming animals. The soil around these instruments Was carefully hoed, and this was done each time the field was cultivated. An outdoor ther- mometer was also hung up on the outside of the cage and readings were taken three times ‘daily, that is, '7 a. m., 12 m., and 5 p. m. These readings started’ April 20, 1918, and are still being taken. It is expected that these soil temperature studies will be further continued for at least ten to fifteen years. It is believed that soil temperature data will be of importance not only to interpret occurrence of plant diseases, but it will also be of value to the agronomist, horticulturist, and to the practical trucker. It is unfortunate that facilities were lacking for recording soil-moisture data in connection with the soil-tem- RAIII PRECIPITATION 1918 FIGURE 9. a. Monthly rainfall for 1918. b. Monthly rainfall for 1919. perature readings. No records were kept of the rainfall at Prairie View. These" data, however, were obtained from the chief of the U. S. Weather Bureau, to whom credit is here given. In referring to» Figure 9a and b one will see that the rainfall data for 19-18 and 1919 are recorded for H empstead, a town‘ about four miles distant from Prairie View, and both in Waller county. In studying Figure 10 we see that the out- side temperature as well as the temperature as indicated by the ther- mometers of one and three inch under the soil fluctuate for April, 1919,. but fluctuate equally. However, on the other hand. the tem- peratures as indicated bv the twelve, twentywfour, thirty-six, and fortyi-eieht-inch thermometers remained fairly uniform. It is further seen that the temperatures of the deeper thermometers, especially the \ i“ s, 2* 1 i: u‘ - n: .. "J ‘Elvin? m- 12s.; u; m... w QLUZIQLWZ»; Lanai‘, bu». 33 W ILTS 0F \\‘-»\'rr:1%_\1mux -\.\'1) HHLATIGI) Cnors. =q=¢¢= _ =§n= w~ m 2 _» ~\ ~h,~\ um .\ L.» I. ll N H I’. G7 ‘IIITIUOWP u u smozm mflmcwm w». wmBEQ oxamwiwm mo: Qsgwwnmficflm wmmmmumm 5. own mmw F owl. Enid 5. Z 8a flu. > wo I wowwnmmsfimm Kwzévowmiid 835mm. mcgvmww wogowosfinm Qmmwmm m. m2». @0555 wouwwuabfim m: wfifiwmm SBumwmSim o». 2:60 835% v2 mm? 34 TEXAS AGRICULTURAL EXPERIBIBYT STATION. a -_- I.‘ #1.?- . lmmnr urllllllnn: £27,737. p", 111a: n flvtZ-‘I/r. n‘ mmumm mmnemm --/-/. - z:- s ‘21 gs 29 A s! Z. ._5 3223212 uh;- nu. ' . 1 ,.¢.<': umnlnrnl '1 - rz. FIGURE 10. TKIIII1YJQ7 nimmnnunv ‘791 : 4/»; mmmm ‘m , -d./d"4t?//,€'m V :x:.'||:1I|ltut11rf1IIX":=I c: l “ ' mew run ‘ 1 tmnperaturv studies for Apxiil and May 0f 1918 and 1919 at Pra ievw, Texas‘. irie V Sui ‘magA Qgagmd 112 ‘$161 [me 3161. ‘Xlnf pa? atmf .10; saypms eammadmax 110s TI EIHIIDRI ~1nx,~1w<;r..@;»:< .»s.:<13 RELATED CROPS. in u n: .-,- . z 22ZZ1/1I;$'I/II/I//" »///. vmnnnmn ‘um-n ' , w”; -1 I ".1 w r.> P111111. --~ n-ul nu rrr/r/I/J/Izml, - .1 #411? | In 'r/1.rr/ "arr/m. 4 ‘ I n Jurfllnvnnurfll. . ;... .. ,.u'.1/,- v n, r’ 41bit: Juan-v -.:-.r-.v-.r-,e:nu-zurr 4,), .4 -' . a? v 1 ‘ 3:I:'.!!5::xv:1I nu I IAIISIIIFIII"JSKIIHDHVIIL. 1|! m - belnnr/Atavx - JI/Ju/r. w». '.— 1 _ v/f zr/flz". YYIIJIIIVIIPIIIHIFIUn; u n ,.““,,“ u“ 1 - v -//-'~' *1 . 2/’ -’r’-ZI-VI'p'IIJ'IZ 14, 4 a nnluunnl I ravzcw/r/zxz1/i - m . - v mu! m- 1 . " _ ' 4,,,W’_,,,._ , " . v-w-'1-J/-r’J-’II/ v . I n 1., nll ma’ - II m: I - - ;11~-/.:v.-~ w. -r JIJJJaa1 Jrzrr av,‘ . unnmnmumnu 1.- » . . - ' - - . ‘ —- -- '1 - 1 -, a’//¢11:¢r;.'~»,...>..:, _ v » - » -_ k -- ltd: 11,-1.3 mun a n nun; n rJ/zr/rd- 1 ' - ' '1 ’ _ vv,’,,"‘: _ )—’.1v. Jruuuv y a 1 . ». I ““___u_-‘-"n _ . niillliJlil-XIIIIIIIX 2 v I x - - » “.4.- JJJv4J5U :.w.r FIJWA.‘ J/ILP” ,i - I luilcatnlluln s-z-azas-v-waafl In! u n: I»FIIJ"'J’A'.IL'ZIII4FJ.'J \ - . ’ null-avg. 1AA; van ' v unauauunsn: nanny- n. _ ,'\) ..., - - . . ' ' ' - IIJJIJEFJJIIIIIIII nuuunnn z 1 n zrrJvI/rrrr/lrz/n z. '1;;;;;;,|-_ v;-,~--.r:.r . saunas: nuymlnau xllltlrllyvavta-ra-r ' 111/: rrr a 11:11:. IJ-PI- a z :,-1.-.-n-/n. , a u a » I 1 4 nu t. w- '»- l." I z urn: 1. . 'fdJ.P'-I!£I'4-'2F.'_"t: ‘F ' z .1: n ucannnu -.—;__ gtal: u; u. x a ht-I n‘. 1:1. II nnaznnuaum uuucllun » 36 TEXAS AGRIOULTLTiAL EXPERIMENT STATION. twenty-four, thirty-six, and forty-eight-ineh, did not go below 55 or above 7O degrees F. The same was practically true for April, 1919. In further studying Figure 10 we see both in May, 1918, and 1919 the deeper temperatures gradually rose to almost 70 degrees F. and fluc- tuated very little above or below. On the other hand, the temperature indicated by the three and six-inch thermometers fluctuated ‘more or less closely with the rise or fall of the outside temperature. Rainy days Would frequently, cool off the temperature of the outside as well as the temperature of the one, three, and six-inch thermometers, whereas the temperature of the twelve to forty-eight-inch thermometers would re- main more or less constant. Again referring to Figures 9 and 11 we see that May, 1918, Was a very dry month; whereas May, 1919, had considerable rainfall. This was also true of June, 1918, which was exceedingly dry, and June. 1919, which was very wet. It became, there- fore, evident that in a dry month such as June, 1918, the deeper tem- peratures. especially those of the twelve, twenty-four, thirty-six, and forty- eight-inch thermometers would practically remain constant at 80 de- grees F. o-r a little above. In June, 1919, with considerable rainfall, the deeper temperatures, although remaining constant, were consider- ably lower, i. e., 7O degrees F. or slightly above, a difference of about ten degrees. The same was practically true of August, 1918, and 1919 i (see Figs. 9 and I2). No temperature data are available for January; 1918, since the read- ings were started only on April 20 of that year. However, in studying Figure 12 for January, 1919, we see that the outside temperature as well as the temperature indicated by one, three, andsiX-ineh thermom- eters fluctuated considerably and this depended on the outside tem- perature. Hoxvever, the deeper temperatures, especially those from twelve to ‘fortyj-eight inches, remained more or less constant at 55 to 6O degrees F. Furthermore, during the coldest days in January, 1919, the temperature of the one, three, and six-inch thermometers never went down to the freezing point and the temperatures of the deeper thermom- eters remained high enough to maintain the acrtivities of soil organisms in these depths see Table 11). ln Figure 12, for February, 1919, we also see that that month was considerably xvarmer than January, and the outside temperature as well as the temperature of the three and six- inch thermometers fluctuated much more than it did during January, 1919. However, thetemperatures from the twelve to forty-eight-inch thermometers remained more or less constant at 50 to 55 degrees F., thus permitting microorganism activities in the deeper strata of the soil. Further interpretation of Figures 1O to 12 will be referred to under life history; as well as soil isolation studies. Figure 13 will be interpreted under the discussion of the prevalence and spread of wilt. It is to be observed from the foregoing (liscussions that the (leencr temperatures remain more or less constant and that during the coldest months of January and February during 1919 in Waller county the temperature did not drop low (enough to interfere with soil microorganism activities. ‘S8191, ‘M8fA BIJYBJd 1'8 ‘$161 ‘Lmruqag pm; Amenuuf ‘3161 ptm 3161 ‘qsnfinv .10; salpnqs eammadme; [[03 ‘ZT HEIIIDLI WILTS OF WATERMELON AND RELATED CROPS. l r’. - = x xx : : : mun». I navy’. 1rr’J-/.r Znflfrzfib qwnrnvasl-nu: snwmu: r x..fi-'l.r.-rr)z.-_rwe.v.nrlr irtnm: - an: "-0 w; _ =., v V -“.......,.=..,-a.,-;-.a-q=..;=w. rn-rmarllmzxwrlh: IFJ-PI-“t/ rxzm - -- ~ - » -- - ~ wwww an _ uinmn Inn's." its!’ irunrrrrnrzrlrrrrnvrara/z _mnu- »» ~ - i ‘A TIIIIIBLFIIITIIASZIJQVJ -_—- y; - F” ‘LO m1,,,,.-,,..,,.»;.v-,m-,,,.» .._...__.._.. N O b _ I I s u IIIi n a n H ZIIIAQJIQII-rrrafryirzrg 1,,” ‘I! IIII Illl aznl: uwp;::a~ :-w/,4‘.r.¢¢-',_,,,_ )4 4- llajullunxl - 1.1-’; ~91‘. . r1145?’ f; lilnrlxlttlnzsiniilvrl sly:- =>uunlunrazrJIIIIJ-fltzfirp/lnf .-m-.--.-.- w’) v.4 . '. -. 1-1::nn-nqnvnnnanrznn-znrxr . . ° vzmfi; z z x uuunll v .~,—.r-l.rlr4zr.r.r ,4- . . , . v.27. < . mu via-Fm: ‘caning .mv@%»@¢m-T¢r z Illullnlillali: Bill u»: v.v.r/Ir4-.-zr/.r.rr4-r.-.> S5535 r2200 E22 .Em2e22wwao v.2 022w 222m .3012 223$ v.2 . 2.22 222w .04. 22.20220 030222 @222 2: 22.222552 2:222 .5222 22582.2: 522E352 mm 26202225222 20.222.22.222. .553 822.2532 mm 26052502. 202222.22... o 002222.. 0222 2o 0252.22 92w? B2200... e71. #000 22w n . ¢ . I . - . - . . . . . - . 000M000... . 000M000 000..000.2 000000.“. 000.000.0 000000.22 . . . . . . . . . . . . . .0202 M0224 000.000 000.000 600x00 . 000.00“) 000.0002“ 000.0000. 000.0000 000000.02 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0202 .054 000.20“. 000.000 0.000.000 000.0000 200.0050 000200.02 000000.02 000.000.“.2 . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . .202 .2222. 000.22 0000.000 602.000. 0000.000}. 000.0000 000000.02 005000.02 000.20“..02 . . . . . . . . . , . . . . . . . . . . . . . . . . . 1.0202 .2202. 000 200 020.000 000.000 2 300.000.“. 000.000 0 000200.02 000000.02 000000.02 . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . .0202 .0252. 000.000 000.000 000.000 _000.200.N 0000.802. 000.2020 200.2000 000000.02 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0202 .352. 000.000 200.0210 000.000 0000.222 N _000.2m0.0 000.0000 000.0000 000000.02 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.202 .002 000.000». 000.002 000.000 0022.000 000.2002 000.0000 000.2000 000000.03. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .022 .0022 2022.000 000.200 000.20“. 0000.200. 000.000.2 000.0020 002000.22 000.000.“. . . . . . . . . . . . . . . . . . . . . . . . . . . . . I202 .754 000.00“. .000.00“. 200.000 000.000 2 000.0“.0 0 000.0000 000.000.“. 000.000.02 . . . . . . . . . . . . . . . . . . . . . . . . . . . .1022 0.2224 000.002 200.002 000.000. 200.000 02300.2. 000.2“.“. 000.000 000.0000 . . . . . . . . . . . _ . . . . . _ . . . . . . . . . .0202 .2292 000 000* 000 002*... 0000 00m 402.21 000 000“. 00w 000.000 000.0002 000.0000; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0202 2E2. .0 0 _ I 1'11! vilulvl! Q32. 22222 2 0. 222522 f 22232. @250 . 22002. 22000 22322 222322 222222.22. 22.3 02222232212 $22322 02. _ $2202: 00 $22222 2.0 @0222: N2 $22222 0 wo22o222 0 220E 2 +20 m22222u22 222 22cm 202m 220205.822“? >22. 22w 522w .522 mo222o2ou 22.892.211.22 20220.2. WILTS or WAIERAiELoN AXD RELATED Cnorsf 4:1 11 and Figure 9. It seems, therefore,ithat the prevalence of Fusaria in sandy soils, both in diseased andhealtliy fields, is directly influenced by the prevalence of soil moisture brought about by greater precipitation. ' CONDITIONS Rivoiuxc Wrrr INFECTION. l There seems no doubt but that numerous biting insects. (Fig. 4e to g) in the field, especially the cucumber-striped beetle, plays an important part in starting infection and in (lisseminating the Fusarium Wilts of watermelon and other cucurbits. This beetle usually feeds on the very young seedlings, biting-into the cotyledons and into the young stems, thereby opening: the way- to infection. Numerous striped cucumber" - beetles (Diabrozfica mftfam Fab.) were collected alive from the water- incelon sick field at Prairie View and placed in sterilized test tubes that were plugged with sterilized cotton. These were brought to the lab— oratory, taken out with sterilized forceps and allowed to crawl on a sterile-poured plate containing potato agar. In-three to four days, a Fusarium as well as several other fungi appeared on the tracks where the beetles were crawling. This Fusarium growth was purified, then transferred to slants, and inoculated into sterilized soil in pots which were planted with healthy watermelon seeds. The young seedlings later wilted in these pots and the Fusarium fungus was reisolated, proving definitely that the striped-cucumber beetle is one of the carriers of Fusarium which causes wilt in watermelon. Striped-cucumber beetles as well as a large ladybeetle (Epilaclswrrta borealvls- Fab.) were also col- lected from a sick squash field at Prairie View and treated in the same way as the striped beetle collected in the watermelon sick field with the same results, namely: that these insects which feed on squash plants were active carriers of the Fusarium squash wilt fungus. Many of the collected striped beetles from the watermelon sick field were let loose in a wired cage containing healthy watermelon plants which grew in a‘ sterilized soil in pots. The striped beetles immediately started" to feed on the plants, and after three days wilting began where these beetles were allowed to feed. The cheek plants ivhich were allowed to be fed on by the beetles collected at College Station from rose plants did not show any evidences of wilt but the plants were finally destroyed by the beetles as a result of the feeding. This showed conclusively that the striped cucumber beetle, as well as other insects, may carry the cucurbit Fusaria wilts from plant to plant. There seems to be no evidences as yet that these insects carry the causal organisms of the watermelon or squash wilts internally in their bodies. Numerous striped cucumber beetles were collected in a diseased watermelon field as they were feeding on young watermelon seedlings. These insects were then placed in a sterilized test tube and brought to the laboratory and disinfected; for methods employed, see page 25. Each beetle was then crushed up in a. tube of melted and properly- cooled agar and poured into sterilized petri dishes. Over fiftv plates‘ were made but no fungus growth appeared. This seems to indicate,- I 42 TEXAS AGRICULTURAL ExrrRtME-Nr STATION. although-not very conclusively,-—that the striped beetle does not carry the causal organism internally in its body. EFFECT or Son. 'l_lE1\[PE1€ATUHF AND Blorsrtinn on THE OCCURRENCE or Wnxr. ‘ It has already been pointed out that the increase in Fusaria in the soil is governed, all things being equal, by the greater abundance of moisture in that soil. In referring to Figure 9 and Table 11 one will see that a largernumber of Fusaria colonies in the soil were actually found during the months of greater rainfall. This is true not only in the summer but also during the winter months. The prevalence of Fusarium Wilts of cucurbits does not seem to follow the same general lines; that is, the greatest amount of disease is found during June, July, and August, when the temperature is the highest. Moisture does not seem to be an absolute necessity since the Wilts are slightly more severe in a dry season (see Fig. 13). IIourever, it should be added that in a dry season infected plants linger but little. In a wet season the infected plants remain alive a much longer period and frequently even during the entire growing season. The untrained eye will, therefore, be apt to overlook the disease. In both cases, however, the yields in a sick field are reduced 50 to 100 per cent. It seems, therefore, that the severity of cucurbit wilts goes hand in hand with the highest favorable soil temperature for the host. This seems why wilt is worse during June, July, and August because at that time the soil temperatures are highest and these temperatures are also best for the fullest development of the host in the field. i Syivrrroivrs OF Wairnnivrenon WILT. The field symptoms of the watermelon wilt are manifested by a grad- ual wilting of the cotyledons and youhg leaflets of the seedlings. This is especially true with seedling infection in the field by Ftzsairium citrulli (Fig. 1c), and F. poolensis. F. niveum also attacks young seedlings but it is more frequently associated ‘with the wilting of older plants. Infection may start at an early age but the diseased-plant will appar- ently’ keep on growing, this being especially true during wet weather. In dry weather, however, the leaves of the affected plants begin to wilt. gradually resume their turgiditv over night, wilt again the next morn- ing, and in two to three days the affected plant usually dies (Figs. 14a and b and 15a and b). Frequently the disease is confined to one or two vines of the plant, in which case the infected vine wilts while the others in the same hill remain healthy. Here the causal fungus is confined only to the vascular bundles of the wilted vines. Later, however, in- fection spreads from the roots to the other vines of the plant. Con- trary to the wilts of some other crops, an example of which is the cab- bage which sheds its leaves, the foliage of dead watermelon vines does not drop off but remains clinging to the plant. The causal fungus is WiLiifis or \\'-\'ri~;.u,\ii<:Lo_\' AND RELATED CROPS. 43 found. in laoth the vascular liuutlles of the roots, stems, and petioles, ivhich become more or less yellowed to liroivned. Isolation cultures were made from a largw: number of wilted. plants and FU-86ZtT4iu47’b' niveum Was obtained from, ziny part 0t the roots, stems, petioles, and leaf veins. The causal fungus xvas also isolated from the tip ends of the longest FIGURE 14. a. Watermelon field badly affected with Fusarium Wilt. b. Watermelon plant wilted by Fusarium. c. and e. Female blossom of the squash. d. and f. Male blossoms of the squash. vines of ir1lecte