fiullelin 843 - Kesisfance 0/ flatten to - Pink Karl/Warm Qamage \__\ Ag; A RY A/aaendm I956 TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. D 111111 R. C LLLL GE S TTTT ON". TEXAS SUMMARY AND CONCLUSIONS This bulletin gives results 0f studies conducted at College Station in 1954-55 to screen a species and varieties of cotton for resistance to pink bollworm damage. e Bolls of a Stoneville 2B x Gossypium tomentosum cross possessed a high de-gree of antib developing pink bollworm larvae. The mechanism of this resistance appeared‘ to be a physi, response of the seed to insect injury. When seed were attacked, large mass/es of cells liferated which engulfed and killed many larvae. e Bolls of G. thurberi appeared to be less resistant to pink bollworm larvae than Stone x G. tomentosum. However, results obtained for bolls of G. thurberi were distorted because. extremely small boll size. » Hexaploid Z-64 bolls exhibited a lower degree of resistance to pink bollworm larvaed two cottons mentioned above. The mechanism of this apparent resistance was not determ Morphological differences of the vegetative and fruiting parts of the cotton plant modification of the egg-laying habits of the pink bollworm moths. A tight-fitting calyx t straight along the outer margin or had flared bracts or both, discouraged pink bollworm, o_v" on cotton bolls. Pink bollworm moths were attracted to vegetative parts having heavy, pubescence and leaves with heavy veins for oviposition. f Physical characteristics of the vegetative and fruiting parts of G. thurberi were such J eggs were laid on plants of this cotton. This resulted in high percentages of the bolls escape; bollworm injury in all tests, even when other cottons were not available for oviposition. thurberi possessed resistance to the pink bollworm because it was not preferred by ad oviposition. J The easiest and most logical approach to development of a cotton variety with resis’ pink bollworm damage would be modification of the structural characters of the cotton p cotton variety having flared or deciduous bracts, tight, straight calyx, coarse pubescence; vegetative parts and heavy leaf veins should result in the vegetative parts being more if to the pink bollworm moths for oviposition than the fruiting parts. Presumably, the dev of a cotton of this type is feasible since all the characteristics are found among various s, cotton. . e A variety of cotton having these physical characteristics would exert several benefici on pink bollworm control. Mortality from weather and other environmental factors should" higher since the first instar larvae would have to migrate over the cotton plant in search Eggs would be more accessible to predators and parasites on the vegetative parts than boll calyx, which should give increased natural control. Insecticides applied to the plants S, more effective since the larvae migrating in search of food would have a better chance ofc contact with the chemicals deposited on the plants. e- CONTENTS , Summary and Conclusions 2 Field Plot Experiments ................. -;_ Introduction 3 Experimental Design ----------------- —- Review of Literature 3 Culture pf Plantsm‘""""""""""” Infestation of Plots < General 3 Examination 0f Bells ___________ ____ : Pink Bifllworm 4 Oviposition Experiments.---___-_-_____ * Procedure 5 Experimental Design -------------- n, " Genera] 5 Characteristics of Cottons ______ ___- M . . Infestation of Plots .................. -- j eth0d 0f Obtalnlng MQthS ------------------ -- 5 Examination of Bolls________________ 1 Method 0f Obtaining """"""""""""""""""" “ 6 Results and Discussioni______ _____________________". Greenhouse Screening Experiment ............. __ 6 Greenhouse Experiment ; Culture 0f Plants 6 Figld Plgt Experiments ________________ ___h I Infestation of Bolls 8 Oviposition Experiments ............. --_‘ ‘ Examination of Bolls ................................. -- 8 Bibliography ______________________________________________ "if . PINK BOLLWORM, Pectinophora - gossypiella Saund.), is one of the most destructive of cotton and one of the six most important ‘; attacking cultivated crops. Entomologists tton farmers of the Unied States are par- rly concerned about the pink bollworm be- it is difficult to control by chemicals and ues to spread into the cotton areas to the v and east of Texas. fective chemical control is difficult because , oviposition habits of the adult and the h; habits of the larvae. Adults require only A to complete the functions of mating and ‘ition. The preferred site for oviposition is the calyx and carpel wall of the cotton flhere the eggs are well protected from l eous and parasitic enemies. Many of the * hatching in these protected sites enter Ill immediately Without moving about over ed parts of the cotton plant. Larvae do not ‘n the external parts of the plant or bolls. i entering the cotton boll, larvae are well - ted from currently used insecticides. i; ause of these habits of the insect, only it insecticides are considered practical for ical control. Since many larvae may not in contact with the insecticide, control with 'cals usually is difficult. Therefore, cultural ices designed to lower overwintering larval ations are strongly recommended for the ’ 1 of this pest. combination of cultural practices and chemi- ntrol measures has given moderate success. sible supplement to these measures is the nce of cottons to pink bollworm damage. rous authors in the past 40 years have 'oned cases in which cottons appeared to istant to attack by the pink bollworm. Most se reports referred to wild or Asiatic cottons _ ed from the general area in which the ~bollworm is believed to have originated. In j cases, these reports were made from casual observations without conclusive supporting v e present study was designed to screen ble species and varieties of cotton for re- ted from a dissertation in entomology submitted to aculty of the Graduate School of the A&M College exas in partial fulfillment of the requirements for egree of Doctor of Philosophy. ctively, formerly research assistant, Department tomology, College Station, Texas, now entomologist, iana Agricultural Experiment Station, Baton Rouge, 'ana; and professor, Department of Entomology, u; Agricultural Experiment Station, College Station, Resistance a/ flatten ta Pink Kai/Warm Damage ’ J. R. Brazzel and Dial F. Martin* sistance to pink bollworm damage according to two mechanisms of resistance as advanced by Painter (1951): (1) antibiosis or a tendency to affect adversely the biology of the insect by lengthening the life cycle, lowering fecundity, de- creasing size or increasing mortality; (2) pre- ference or nonpreference of the insect for certain species and varieties of cottons for oviposition or food. The influence of differences in calyxes, bracts and pubescence was particularly observed in the study of preference for oviposition. A cotton possessing properties antibiotic to the larvae, or possessing morphological modifications that make vegetative parts more desirable for oviposition than fruiting parts, would aid existing methods of control of the pink bollworm. REVIEW OF LITERATURE General Reports of the resistance of host plants to insect attack have been on record for over 100 years (Painter, 1951). One of the most effective and well-known-examples as a means of insect control is the use of resistant rootstock to control the grape phylloxera, Phylloatera vitifoliae (Fitch), on grapes, Davidson (1921). Parnell (1935) and Parnell et al. (1949) reported ex- cellent control of leafhoppers of the genus Empoasca on cotton in Africa by the use of resist- ant varieties. -Only a few examples of such a high degree of host plant resistance to insect damage are known. Painter (1951) stated that the most important role of insect resistance in crop plants was to aid other control measures. The term “insect resistance” is used in this study in the sense that Painter (1951) and Snell- ing (1941) used it. Painter classifies the causes of resistance as: (a) antibiosis—adverse effect of the plant on the biology of the insect; (b) pref- erence—-choice of certain plants by the insect for oviposition, food or shelter; and (c) tolerance —repair, recovery or ability of the plant to with- stand insect attack. One, or a combination of any of the three, produces most cases of re- sistance. While little is known about the cause of host plant resistance to insects, many workers have noted a relationship between physical characters of the host and insect resistance. Cunliffe and Hodges (1946) found that resistance of oats to Oscinella frit (L.) was connected with some factor of plant attractiveness which determined the extent of oviposition on theplants. Thrips 3 --‘t resistance in onions was found in varieties with the thickest leaf epidermis, which apparently offered more mechanical resistance to feeding punctures (Peterson and Haber, 1942). Mum- ford (1931) reported that resistance of citrus to mealy bug attack was found in the thick-skinned varieties, Which were more difficult for the in- sect mouthparts to penetrate. Painter (1951) stated that it was doubtful whether differences in tissue hardness of varieties of one species of plant would be great enough to affect the degree of feeding by insects normally attacking that plant species. Richardson (1925) pointed out that the physical character of plant surfaces in many cases may condition the oviposition response 1n insects. Thus, a plant variety that did not possess the necessary structural characters to stimulate the insect to oviposit could escape insect injury. Painter (1951) stated that various morphological differences found in plants elicit ‘different re- sponses from insects through mechanical stimuli. These mechanical stimuli are most likely to be- come a factor in host plant resistance to an insect by affecting the egg-laying response of the in- sect. Hairy leaves of corn were found by Mc- Colloch (1920) to contain more corn earworm eggs than smooth-leaved varieties. Other insects, such as roaches (Folsom, 1922) and Drosophila (Adolph, 1920), require a certain type of mechanical stimulus before oviposition occurs. The bur seed fly, E/uaresta aequalis Loew., was reported by Currie (1932,) to be unable to oviposit in the bur of Xanthium sp. from which the recurved tips of the spines had been removed. Poos and Smith’s (1931) studies of oviposition and nymphal development of Empoasca fabae (Harris) revealed that adults deposited eggs freely on all species of plants tested, but fewer nymphs developed on the plants with the most pubescence. " Jones et al. (1934) reported that the more open-type onion plant provided less suitable con- ditions for thrips development, resulting in lower populations and less damage to the host. Hinds (1906) reported that cell proliferation, a physiological response of the cotton boll to insect injury, caused the death of many boll weevils, Anthonomus grandis Boh., by mechanically crush- ing them. Pink Bollworm Marlatt (1918) advanced the theory that the pink bollworm originated in India and offered as supporting evidence the apparent resistance of native Indian cottons to this insect. Imported commercial cottons were much more susceptible to attack than the indigenous cottons. Husian et al. (1940) conducted experiments that supported Marlatt’s theory of resistance of Old World cot- tons. In field plot and cage tests in the Punjab, he found significantly fewer bolls attacked. and 4 fewer larvae per boll in two Old World A of Gossypium arboreum L. than in t World varieties of G. hirsutum L. The pink bollworm was described by ‘ (1842) from specimens of the insect se from India. The report accompanying’ sects stated that native cotton somet" affected by the pest and added that im *1 land cotton was damaged severely on light soils. Both Hunter (1926) andfl (1912) cited this report as evidence of " to pink bollworm damage in Old Worl Hilson (1925) stated that it was definit‘ in Madras Presidency that the stem " spotted bollworm and possibly the pink , showed a decided preference for hirsut over the indigenous species. Harlan pointed out that workers on cotton i. observed that the pink bollworm prefe, World to Old World cottons. He bel' preference was caused by a chemotropic. of the insect which resulted in the layi“ eggs on the plant species with the more. 1f odor. Wolcott (1927, 1928) found native‘, Haiti much less attractive to pink boll commercial varieties grown there. y, mercial cotton was harvested, the insec‘ native cotton nearby, but resulting i ‘ steadily declined as the season advanced; stated that although the cause of resis i, unknown, it seemed to be inherent in P itself and not -due to environmentey Audant et al. (1937) stated that one l, of growing native cotton in Haiti was? ance to pink bollworm. The natural f, proved so effective that negligible d sulted while imported commercial co f forced out of production after the intr s, the pink bollworm in 1925. When ‘only = ton was grown commercially, the pink» practically disappeared, infestations u exceeding 1 or 2 percent. , Fenton (1927) reported only a 3.". infestation of G. thurberi Todaro |____ grown near commercial varieties of c\ had approximately 100 percent of the. fested by pink bollworm. No adults ‘ served to emerge from samples of t when held overwinter. ‘ Reports of Chapman (1937, 1938, , resistance of commercial varieties of I pink bollworm damage indicated no -..- the varieties studied. He stated, ho '5; the early-maturing varieties escaped f‘ heavy, late-season pink bollworm dam ' ‘rs n1 an e-o-naa er‘ Q nuke-Info: rs " 4;..p,.n.~i._fl r5 na x. a 5-11 ran-ya ' mlav-u-Fnaese-i Squire’s (1939) experiments to de nature of resistance to pink bollworm, okra, Hibiscus esculentus L., indicat_ to 41 percent of the total mortality W a able to slime engulfing the larvae. He __ the survival of pink bollworm larvae“ hr-o-n-nm ‘g- ssypium trilobum (DC) Kearney and Sea Is- d cotton and found that approximately the q e percentage of larvae entered each cotton f none developed on G. trilobum. . According to Knight (1944), Harland report- ‘that G. thurbewl was not attacked by the pink ‘llworm in Trinidad or Brazil. Knight further i ed that G. thurberi planted at Shambat in the glo-Egyptian Sudan showed a complete ab- _-= of pink bollworms, although surrounding p mercial varieties had a 97 percent infestation. i was of the opinion that G. thurberi was im- ‘ne to pink bollworm attack under the con- ions at Shambat. Crosses were made with x el (a variety of G. barbadense) to determine the immunity could be transferred to New agrld cottons. {Several investigators attempted to breed cotton istant to the bink bollworm at Shambat. Anson 945) reported that G. armourianum Kearney peared markedly resistant and included it in - breeding program. He crossed G. armouria- (m and Sakel and called the resulting hexaploid armadense. He considered this cotton a true i ies. The following year, Knight (1946) re- rted G. armadense to be free of pink bollworm qestation in the field. He suspected the resist- ce to be caused by the large supply of essential s or resins, or both, found in oil glands over i‘ plant and bolls. During the 1945-46 season, Q thurblwwi was crossed successfully with Sakel d the resulting hexaploid plants were called G. _r rbadense. None of these plants showed any a of resistance to pink bollworm attack, and ight (1947) concluded that the resistance of ‘ thurberi was recessive. - Knight’s (1948) report from Shambat for the 46-47 season lists eight species of Gossypium t were surveyed during the season to deter- _'ne the percentage of bolls infested by the pink llworm. The results indicated that G. thurberi, p armourianum and G. somalense (Giinke) were hly resistant and G. anomalum Wawya and yvitsch less resistant to the pink bollworm. a During the 1947-48 season, G. thurberi and inarmourianztm crosses with Sakel were tested ' the field for pink bollworm resistance at ambat. Knight (1949) reported that no appre- ble resistance to pink bollworm was apparent 1 acre of G. thurberi x Sakel crosses. He ncluded that either the resistance could not ‘nifest itself in a New World tetraploid cotton, that not enough parents were used in the p vious generation to insure reasonable certainty g including resistant plants. He considered the st possibility the more likely. Of the G. ourianzam x Sakel crosses, two plants appear- resistant and were selected for further test- .8’- -‘ The breeding program at Shambat for resist- A to pink bollworm was discontinued from 47 to 1953 (Knight et al. 1953). The work om 1953 through 1955 consisted of selecting plants that appeared to suffer the least insect injury in the field and back-crossing them with commercial varieties (Knight et al. 1954 and Dark et al. 1955). Few techniques have been developed for a study of this sort. Some workers, however, have conducted detailed studies in an attempt to deter- mine if resistance to the pink bollworm existed in selected cottons. Squire (1939) described a tech- nique in which each cotton boll was subjected to the same initial insect infestation by transfer- ring freshly hatched larvae to the green bolls. He did not take into account differences in boll sizes when he recorded his results as larvae recovered per boll. Differences in boll size influence the number of larvae surviving in each boll. Brazzel and Martin (1955) showed that when cotton bolls were heavily infested with pink bollworms, many larvae were killed as they came in contact with each other. Thus, fewer larvae would be expected from smaller than from larger bolls when the initial infestation was the same. Husian et al. (1940) described a technique for small plot tests under cages for studies on resistance of cotton to pink bollworm. The technique em- ployed in small plot tests in this study is similar to his. Additional information on biology and host plants of the pink bollworm may be found in reports by Hunter (1926), Ohlendorf (1926), Loftin (1921), Ballou (1918) and Heinrich (1928). PROCEDURE General Method oi Obtaining Moths Pink bollworm adults used for egg production and for infesting the caged plots were obtained from infested seed cotton collected during the fall of the previous season when most of the larvae were in the long cycle stage.» The seed cotton was stored at approximately 40°F. and removed from storage and placed under pyramid- type emergence cages as adults were needed. The emergence cage was 3 feet square at the bottom and 2 feet high, with a collecting jar 2 inches in diameter which screwed into a holder at the top of the cage. A screen cone was placed in the mouth of the collecting jar with the concave portion of the cone pointing upward and provided with a 5-millimeter hole at the top to facilitate entrance of the moths into the jar. Moths enter- ing the jar from the cage below were trapped. Moths would begin to emerge from the seed cotton in about 2 weeks if the material was kept moist and warm. The collection jars were inspected daily and moths removed. Carbon dioxide was used to immobilize the moths for handling. Emergence cages were placed in a shady area outside the laboratory during the summer and in 5 the greenhouse during the winter. The seed cot- ton was kept moist by spraying it with water at Weekly intervals. Moths emerged from a cage for 6 t0 8 weeks, then the spent cotton was re- placed with fresh cotton from storage. A con- tinuous supply of pink bollworm adults was main- tained by using a battery of emergence cages and replacing the spent cotton in a different set of cages every 2 weeks. Method oi Obtaining Eggs Pink bollworm adults collected from en1er- gence cages were placed in a plywood box approx- imately 8 inches square which was coated inside with paraffin. A hole 4 inches in diameter in the top of the box was covered with 14 x 18 mesh galvanized screen wire. Another piece of 32 x 32 mesh plastic screen was placed over the coarser these screens and held tight against them. The moth would inse abdomen through the screens and oviposit o moistened towel. green cotton leaf. Greenhouse Screening Experime» Culture o1 Plants ments. Table 1. Seed of 139 species and varieties of Goss were planted in 1-gallon tin cans filled ' suitable soil medium. Plants were thin ‘ one plant per pot and grown in the gree , throughout the 2-year period of the experi) Five potted plants of each cotton were up obtain the records desired. used as a standard for comparison in all g The origin of the cottons is Classification is according to H \ 1 Deltapine '_ a _~. screen. A green cotton leaf was placed over son et al. (1947). h TABLE 1. RESULTS OF GREENHOUSE SCREENING EXPERIMENT FOR RESISTANCE OF COTTONS TO PINK BO LARVAE AT COLLEGE STATION. 1954-55 - 3 Percent larvae Larvae _ . Total Mean boll _ recovered Comparison _ _ V Cotton bolls weight Entered suiivtged pei; grcltlm D lwith 15 Origin of cotton . in grams o o e tapine . ‘ _ bolls entry weight Deltapine 15 307 13.7 71.6 71.8 .1892 United States G. anomalum Southwest Africa f G. arboreum Asia 6. Africa . Garo Hill (a) 31 13.3 73.5 82.5 .2277 East BengaIGAss Garo Hill (b) 24 15.4 77.5 92.5 .2333 East BengaIG-Assg Nanking G-10 86 6.6 83.7 70.3 ~ .4303 1 China 1» Neglectum (a) 35 4.4. 65.7 66.1 .4897 1 India Neglectum (b) 79 4.9 65.1 66.1 .4431 1 India Okinawa 50 3.3 64.8 75.3 .7376 1 Okinawa Sanguineum (a) 72 4.5 65.8 70.0 .5070 1 India g Sanguineum (b) 50 4.3 56.0 66.4 .4294 1 India u A G. armourianum Gulf of California 1' G. barbadense South America » Darwinii 14 3.4 67.1 63.8 .6263 1 Galapagos Island! Kidney cotton Tropical South -- _ Pima 42 8.2 71.9 82.8 .3638 1 Americas " Crosses Diploid Z-783 College Station " Hexaploid Z-64 19. 6.3 80.0 44.1 .2988 College Station ' ’ Hexaploid Z-66 52 3.8 67.3 61.1 .5371 1 College Station Hexaploid Z-73 College Station Hexaploid Z-77 College Station q Hexaploid 8 Cgllege Slqfion .1' Hexaploid Z-721 College Station 1 Igexaplolid 223-784 College Station tonevi e x ' G. tomentosum 79 4.7 58.9 24.7 .1564 College Station {- Tetraploid 1 28 4.9 62.9 53.4 .3396 1 College Station Tetraploid 2 College Station Tetraploid 3 College Station Tetraploid 4 College Station Tetraploid 5 27 6.7 73.3 58.6 .3183 1 College Station . Tetraploid 6 College Station 1 G. gossypioides Mexico G. harknessii Gult of Caliiorn G. herbaceum 79 .28 67 6 74 2 908 lAlsia 6. Airlca ‘ Kuljianum . ‘. . . 7 1 ongolia Persicum 57 5.0 60.4 75.6 .4577 1 Persia . Wagad 44 6.4 69.5 64.7 .3543 1 Southwestern A’ I Wrightianum 29 6.7 66.9 68.0 .3385 1 India G. hirsutum North a South v Baker 51 69 11.0 92.4 63.4 .2709 _ College Station 1' Frego bract 54 12.0 82.7 79.0 .2785 1 College Station.“ Lintless 27 9.8 77.0 80.8 .3185 1 College Station MW-1 1 67 12.0 86.9 67.9 .2400 Guatemala ' MW-147 41 18.3 88.0 71.4 .1693 ‘1 Guatemala MW-218 30 3.2 84.7 44.1 .5815 1 Mexico l. LE 1. RESULTS OF GREENHOUSE SCREENING EXPERIMENT FOR RESISTANCE OF COTTONS TO PINK BOLLWORM LARVAE AT COLLEGE STATION. 1954-55 (continued) Percent larvae Larvae Total Mean boll _ recovered Comparison Cotton bolls weight Entered Survived per gram with Origin of cotton _ in grams bolls after of boll Deltapine 15 enlfY weight MMvfV-ZSS 23 2.6 62.6 $3.8 .5574 2 Mexico " -269 26 16.8 65.4 .9 .1418 Mexico -MW-298 19 1.2 67.8 26.2 .8676 2 Mexico Pubescent 49 11.7 99.2 71.2 .2951 College Slelion unctatum 96 5.6 79.5 64.8 .4522 1 A5201!!! sPm-4 51 12.5 92.9 74.9 @972 College Sielion , exas 3 8 9.2 62.5 88.0 . 989 Mexico fTexas 16 12 14.1 83.3 84.0 .2488 Mexiw I Texas 20 32 18.6 75.6 86.0 .1743 Mexiw ‘Texas 21 39 21.2 72.8 81.7 .1400 MeXiCO Texas 24 12 10.1 60.0 77.8 .2320 ' 2 MEXiCO Texas 29 21 15.9 92.9 99.9 .‘2199 ’ Mexico ‘Texas 31 21 14.3 77.1 82.7 .2224 z MQXiCQ Texas 32 38 17.8 75.3 86.0 .1815 Mexico Texas 34 31 15.8 72.3 77.7 .1773 Mexi¢0 Texas 35 18 14.0 71.1 84.4 .2144 MQXiCO Texas 37 16 21.2 72.5 87.9 .1503 o MQXiCO ‘Texas 40 37 13.8 77.3 69.9 .1952 ' MBXiCO Texas 42 20 13.1 63.0 82.5 .1981 q MeXi¢<> Texas 49 49 17.9 79.7 79.4 .1759 ' Mexico . Texas 49 12 20.9 79.7 94.9 .1904 Mexico Texas 49 27 19.9 99.9 77.7 .2029 j a Mexico Texas 59 99 9.9 71.9 75.7 .9299 1 Mexico Texas 55 24 7.2 74.2 79.7 .4090 Mexico Texas 56 40 15.3 72.5 80.0 .1891 1_ Mexico Texas 61 15 8.7 78.7 79.7 .3217 ‘ Mexico “Texas 62 24 12.9 85.0 88.2 .2900 1 Mexico Texas 63 23 11.1 81.7 78.7 .2907 ‘ Maxim 9X68 64 20 14.5 79.0 82.3 .2236 1 Mexigq v exas 67 26 14.7 66.2 75.6 .1701 Mexiaa e exas 6 5.4 70.0 57.1 .3727 2 Guatemala _ exas Guatemala exas 99 13 17.3 70.8 89.1 .1824 . Guatemala Texas 100 8 9.9 80.0 71.9 .2897 Guatemala Texas 101 43 13.3 63.7 81.0 .1940 Guatemala Texas 105 19 9.2 71.6 79.4 .3075 2 Guatemala Texas 108 15 11.8 82.7 88.7 .3109 2 "Mexico e exas 109 28 10.3 67.1 87.2 .2846 Mexico , exas 151 14 8.4 74.3 78.8 .3478 Guatemala c? exas 158 12 7.2 66.7 72.5 .3341 2 Guatemala exas 160 27 9.9 76.3 79.6 .3060 ‘ Mexico ~ exas 161 21 11.5 56.2 83.1 .2029 - Mexico - exas 168 14 13.1 87.1 83.6 .2782 Guatemala . exas 169 18 7.6 73.3 65.2 .3139 2 Guatemala Texas 183 28 12.7 69.3 81.4 .2215 2 Mexico exas 195 12 11.3 65.0 82.1 .2362 2 Guatemala Texas 197 11 9.1 47.3 69.2 .1805 Guatemala. 5 exas 198 16 7.9 52.5 81.0 .2690 2 Guatemala "Texas 200 15 10.8 69.3 80.8 .2585 2 Guatemala Texas Z03 29 9.6 64.1 81.7 .2727 1 Guatemala Texas 204 20 10.3 60.0 85.0 .2467 Mexico Texas 205 27 8.6 68.1 82.6 .3290 ‘ Mexico Texas 206 17 11.7 71.8 86.9 .2675 2 Mexico Texas 214 16 8.6 81.3 76.9 .3626 1 Guagemala Texas 217 20 8.4 64.0 71.9 .2725 Guatemala GXGS l7 9.7 70.6 78.3 2 Guatemala = exas 221 19 8.2 80.0 76.3 .3744 ‘ Guatemala Texas 224 17 9.1 62.4 83.0 .2837 i Mexiaa Texas 225 28 9.1 75.0 75.2 .3110 ‘ Maxim e exas 226 28 10.2 75.0 81.0 .2984 ‘ Mexiaa "Texas 239 18 9.0 72.2 78.5 .3133 ‘ Guatemala Texas 240 23 6.8 74.8 72.1 .3972 ‘ Guatemala _ exas 242 20 11.7 79.0 79.7 .2691 1 Guatemala < exas 243 J 22 10.8 76.4 81.0 .2861 1" Mexico Texas 244 \ 35 13.1 80.6 81.6 .2499 Mexico ‘ exas 245 12 9.5 65.0 79.5 .2729 Mexico Texas 294 22 9.9 73.6 82.7 .3064 Mexico exas 366 33 6.8 57.0 84.0 .3510 ‘ Central America " exas 382 29 17.8 71.0 72.8 .1455 College Station Texas 384 32 17.2 91.3 79.5 .2113 Tahiti "Texas 389 23 0.5 11.3 53.8 ~ .5932 c Caribbean region 0X65 41 2.9 66.4 .6540 I Afizana TABLE 1. RESULTS OF GREENHOUSE SCREENING EXPERIMENT FOR RESISTANCE OF COTTONS TO PINK BOLI. y LARVAE AT COLLEGE STATION. 1954-55 (continued) Percent larvae Larvae Total Mean boll _ recovered Comparison _i Cotton bolls _we1ght Entered Surgwed per gram with Origin of cotton i 1n grams bolls ‘I 1°‘ of boll Deltapine 15 entrY weight Texas 398 39 3.9 64.1 78.4 .6389 1 Arizona Texas 399 46 5.3 67.8 75.0 .4776 1 Arizona Texas 402 31 5.3 67.7 80.0 .5147 1 Arizona Texas 409 36 7.2 65.6 78.0 .3571 1 Arizona ' Texas 420 42 12.4 75.2 71.5 .2176 2 United States Texas 423 47 13.0 71.1 87.4 .2391 1 College Station Texas 516 33 12.8 79.4 85.5 .2660 Belgian Congo Texas 523 26 9.5 76.9 81.0 .3285 Belgian Congo Texas 536 College Station G. lrlotzschianum Galapagos Islands Davidsonii Gull of California G. raimondii ‘ . Northern Peru A G. stocksii 14 0.3 22.9 31.3 1.2195 2 Southeastern Asia . G. sturtii Australia 1 G. thurberi 82 0.9 31.7 22.3 .4096 1 Mexico 6. Arizona "a G. tomentosum 1t test indicated that the number of larvae recovered per gram of boll weight was greater than for Deltapine 15 at level oi significance. 1t test indicated that the number oi larvae recovered per gra level of significance. 3t test indicated that the number oi larvae recovered per gram of boll weight was less than tor Deltapine 15 at the 5 i of significance. Cotton bolls were infested with pink bollworm eggs when 10 to 20 days of age. Infested bolls were removed from the plant and examined 1O days later when they were 20 to 30 days old. Blooms were tagged with a different colored tag during each 10-day period to identify bolls of proper age range for infestation with pink boll- worm eggs or to collect them for examination. For example,.all blooms were tagged daily with white tags from July 1 to 10. All bolls marked with white tags were 10 to 20 days old on July 20, at which time they were infested with pink bollworm eggs. On July 30, all white-tagged bolls were 20 to 30 days old and were collected for examination. By usingtags of three colors and following this schedule of tagging, infesting and collecting, bolls on the plants of different age groups could be separated easily. Infestation of Bolls Each cotton boll in all tests was infested with five viable pink bollworm eggs when the boll was 10 to 20 days of age. Eggs deposited on a cotton leaf in the oviposition cage were removed with a moist camel hair brush and arranged in lots of five eggs on a sheet of paper marked off in 1 square centimeter sections. When sufficient lots of eggs had been collected, each lot was transferred to a boll on the cotton plant. Trans- fer of eggs to the cotton bolls was made with a moist camel hair brush. Egg masses were placed on the upper side of bolls in sutures near the apex. Eggs adhered to cotton bolls readily if sufficient moisture was applied to the bolls when the egg masses were transferred. Eggs were allowed to develop for 2 days before they were used to infest bolls. Viable eggs could 8 m of boll weight was greater than tor Deltapine 15 at Z Hawaiian Islands ' be identified easily by the reddish color r: developing embryo, as compared with ~..'} lowish color of infertile eggs. Hatching t; egg usually occurred within 24 hours after i_ fer to the boll. An infestation level of fiv per boll was selected because of the ext‘ small size of some cotton bolls. Examination of Bolls Infested bolls were removed from the" ing cotton plant 10 days after eggs were a“ and were examined for the number of en holes and larvae. Bolls at the time of I nation were 20 to 30 days of age. Thiie cedure allowed the pink bollworm la i, develop in optimum-age bolls. Since bolls‘, not removed from the growing plant duri developmental period, larvae were subjec.‘ natural conditions in the boll for develo Because of the wide variety of cottons? and their unpredictable fruiting characte it was impossible to obtain boll samples each cotton during each 10-day period. T; comparable results, a sample was obtainedfl Deltapine 15 for each 10-day period. .. samples of Deltapine 15 collected at the sam‘ as test samples were used in comparisons o test cotton with the standard. After bolls were collected, bracts and vf were removed by cutting smoothly acrosst f of each boll. The weight of each boll '~ corded to the nearest 1/ 1O gram. Bolls, examined under a binocular microscope f; number of larval entrance holes evident s; outside of the boll and the number of , found inside each boll. The numberof 1' *3 _ vered per gram of boll weight from each _n was calculated from the data obtained. Field Plot Experiments Two field plot experiments were conducted ; 954 and one in 1955. Experiment 1 in 1954 uded G. thurberi and 41 varieties of G. utum. Experiment 2 conducted the same ir consisted of G. thurberi and 36 varieties of hirsutum. Gossypium thurberi, Pima (G. badense) and Deltapine 15 were included in 1955 experiment. rimental Design 1A randomized and replicated design was used ;the experiments. Experiments 1 and 2 con- ted during 1954 were each replicated four es. Each replicate consisted of one plant of 1h cotton randomized within a plot. The 1955 eriment was replicated five times with six nts of each cotton randomized in each repli- e or plot. a» Plots were two rows wide and 36 feet long, or P 00 acre in size, and were inclosed by a 6 x 6 x foot cage consisting of plastic screen stretched a framework constructed of 1/2-inch gal- a ized iron pipe. The screen was regular 14 x mesh which would exclude all pests except 'der mites and aphids, and would confine pink lworm moths released in the cage. Spider tes and aphids were controlled by monthly iage applications of schradan. l’ lure of Plants " Seed of the different cottons were treated th Ceresan and were germinated in the green- use in 5-ounce paper drinking cups ‘filled with mixture of 50 percent fine gravel and 50 per- , t humus soil. The soil mixture was kept moist i watering daily. Plants were transferred to '- field after reaching the two to four-leaf ge. 1; The cottons were planted in the greenhouse ut May 15 and were transferred to plots in the _ld during the first week of June. Transplant- was done by tearing away the paper cup and tting the plant, with the soil mass on the roots, to properly spaced holes in the plots. Spacing l. plants was 18 to 20 inches in the row. A Blooms were tagged in these experiments in e same manner as described for the greenhouse pi; eriment. Tagging of blooms was started in i154 when the first blooms appeared. Since some rieties bloomed earlier than others, all cottons ere not represented in each boll collection. i erefore, the procedure was modified slightly i the 1955 experiment. All squares were re- oved at weekly intervals from earlier fruiting ttons until squares were present on all the cot- ns. Then the plants were allowed to bloom 1 d the blooms tagged in the usual manner. Infestation of Plots Pink bollworm populations inside caged plots were controlled by periodic introduction of moths. Approximately 150 moths were introduced into each cage at 10-day intervals. No attempt was made to sex moths since the sex ratio was approximately 50-50. Fenton and Owen (1953) found that the preoviposition period of the pink bollworm was approximately 3 days. Eighty-two to 94 percent of the eggs were laid on bolls when they were available. Also, the greatest total egg deposition occurred the first night of oviposition and oviposi- tion usually ceased in 7 to 10 days. Therefore, the first moth releases were made in the cages 3 days before the oldest bolls were 20 days of age to allow for the 3-day preoviposition period of the insect. When the moths started laying eggs, a crop of bolls ranging from 10 to 20 days of age was available for oviposition. The level of pink bollworm infestation selected was heavy, but this was considered necessary to prevent any cotton bolls from accidentally escaping infestation. The cottons set bolls throughout the season. Examination of Bolls Bolls were collected when 20 to 30 days old and were examined in the same manner described for the greenhouse experiment. Boll collections were made at 10-day intervals from August 10 through October 20 in experiment 1, and from August 14 through October 14 in experiment 2 during 1954. In 1955, boll samples were collected on September 20 and 30 and October 10. Oviposition Experiments Experimental Design Combinations of selected cottons with various modifications of bracts, calyxes, pubescence and leaf types were randomly planted in 1/200-acre plots in the field. The plots were caged in the same manner as the field plot test. Each test included only one caged replicate. Two tests were conducted during 1954. G. thurberi and Deltapine 15 were included in test 1, and G. thurberi only in test 2. Seven experi- ments were conducted during 1955. The cottons included in each were: test 1—G. herbaceum, Frego bract and Deltapine 15; tests 2 and 3- Pima and Deltapine 15; test 4—Pima, Texas 536 and Deltapine 15; tests 5 and 6—Pima, G. thurberi and Deltapine 15; and test 7—G. thurberi with bolls present, Pima and Deltapine 15 with all bolls removed. Characteristics oi Cottons Cottons included in these experiments and the structural characteristics of each are described following. Deltapine 15 had normal foliaceous bracts which were serrate almost half of their length. The outer margin of the calyx was con- voluted with a total of five or six elongate tips occurring around the boll. A moderate amount of pubescence was present on the vegetative parts, with the most found in the growing terminals. Pima had very large foliaceous bracts which completely covered the boll, with relatively shal- low serrations along the distal edges. The calyx was membranous and straight along the outer edge, fitting tightly against the carpel wall. The leaves were larger and had heavier midribs than Deltapine 15. A moderate number of stiff leaf hairs were on the younger leaves. G. thurberi had narrow, stiff, spike-like, flar- ed bracts. The calyx was fleshy and straight along the distal edge, fitting tightly against the carpel wall. The midribs of the leaves were weak and the plant was almost glabrous. G. herbaceum was similar to Deltapine 15 except that the bracts flared widely, exposing the entire cotton boll. Frego bract was a mutant of G. hirsutum that had distorted, twisted, slightly narrowed and elongate bracts. Texas 536, commonly called Extreme Round Leaf, had narrow bracts, 5 to 7 millimeters in width, which gave the boll the appearance of being almost bare. The leaves narrowed at the junction of the petiole and blade and looked much like cotton suffering from 2,4-D damage. G. thurberi, G. herbaceum, Frego bract and Texas 536 were planted in paper cups in the greenhouse, as described for the field plot ex- periments. These cottons were transplanted to the plots in the field after reaching the four- leaf stage. Pima and Deltapine 15 seed were planted directly into the plots in the field. Iniestation of Plots Approximately 150 ‘moths were introduced into each caged plot when the cottons had bolls of the desired age. The oldest bolls in experiment 1 of 1954 were 3 weeks old and 4 weeks old in experiment 2 when moths were introduced into the cages. Experiments 1 through 4 of 1955 con- tained bolls 3 weeks old and experiments 5, 6 and 7 had bolls older than 3 weeks when moths were introduced. Cotton plants in the plots were exposed to the pink bollworm moths for 5 days before exami- nation. This allowed for a 3-day preoviposition period and 2 days of maximum oviposition. An infestation level of 150 moths to 1/200 acre was high, but was used to insure that no cotton bolls escaped oviposition accidentally. Examination of Bolls Five days after the cottons were exposed to pink bollworm adults, 5 to 10 plants of each cot- ton were selected for examination for eggs. All plants collected for examination had approxi- l0 . the technique was discontinued. " mately the same amount of vegetative g The vegetative sites examined for eggs wer minals, leaves and the axils of stems and < Squares and bolls below the bracts aroun nectaries, inside the bracts and under the é were examined for eggs. . Attempts were made to modify the brac ; calyx of Deltapine 15 by cutting and tri n them to determine how these modifications r affect the oviposition habits of the pink boll moths. The bracts were cut away '5 but the resulting rough, pitted depression f, at the site of the wound attracted mot a oviposition. The convoluted tips were tri from the calyx to make it straight along the" edge. However, the calyx curled and split ' it had been cut, resulting in many eggs deposited in these locations. Apparentl distortions afforded the necessary stimuli Q duce oviposition and the moths were attra these distorted locations. Since the f modifications could not be produced artifi, RESULTS AND DISCUSSION Greenhouse Experiment Results of a 2-year greenhouse expe designed to screen cottons for antibiotic j on pink bollworm larvae indicated the w, resistance of several cottons. The datafl used in several types of tests for significa evaluating the results of this experiment} tons that appeared to be resistant in one 44 test and not resistant in another were elimi Larval behavior of the insect before an entry into the cotton boll should be co a in an evaluation of the results of this expe _ Pink bollworm larvae are antagonistic each other and many migrate away from fruits when the larvae are crowded (Bra r Martin, 1955). This reaction to crowding: explain the relatively low percentages of ,- that entered the small-boll cottons with m. weights below 2 grams. The same auth ported that pink bollworm larvae may -, other inside the cotton boll. Thus, mortality inside the small-boll cottons c” due to the cannibalistic habit of the _, This would lower the percentage of sur the larvae that entered the small bolls. 9' The use of five eggs to infest cotton y, gardless of the size of the boll, tended to the data. Results obtained with five eggsii on a small boll of G. stoclcsii, which averai gram in weight, would not be valid for com- with the results obtained with five eggs apt a boll of Texas 21 with a mean boll weight. grams. For example, G. thurberi had a weight of 0.9 gram. The mean boll We Deltapine 15 was 13.7 grams. If the ~pio ,- s» infestation were based on the number of V per gram of boll weight, the infestation 0f rberi bolls was approximately 15 times than on Deltapine 15 bolls. p was thought, however, that the techniques yed in this experiment were acceptable, blwith these obvious sources of error. The Tmental error affected the extremely small- ttons most; however, only four cottons were 1 that could be considered as having A» ely small bolls (with a mean boll weight than 2 grams). The purpose of the d s tests for resistance was to test the data ghly in view of the experimental error. It a ought that this error could be adjusted best ‘the experimental design consisted of a con- - level of infestation for all cottons, since ll size of the different cottons was not 0' Thus, the limitations of each test were ered when evaluations of the results for piicance were made. iequate samples of bolls were obtained from 2 the cottons tested, which included varieties 4 hirsutum, G. arboreum, G. barbadense, G. ceum, G. stoclcsii, G. thurberi and various s. The greenhouse experiment was de- u and the data collected in a manner that ‘ permit comparisons of the number of e recovered per gram of boll weight of each ‘gnificantly more larvae per gram of boll t were recovered from 68 of the cottons jfrom Deltapine 15. In 41 of these cottons, ifferences were highly significant. MW- ' ontained significantly fewer larvae than pine 15 and was the only cotton that ap- i» to be resistant by this test for significance. __ver, the position of this cotton in relation e regression line in Figure 1 indicated no nce. umber of larvae recovered per gram of boll t, Table 1, indicated a correlation between _two values. As the mean boll weight in- d, the number of larvae recovered per gram ll weight decreased. The curvilinear regres- of larvae recovered per gram of boll weight ean boll weights is shown in Figure 1. The '0n below the regression line of G. thurberi, = 389 and a cross of Stoneville 2B x G. ] tosum indicated resistance to pink boll- attack. Two of these cottons, G. thurberi exas 389, had extremely small bolls which Iged less than 2 grams in weight. Gossypium ii and MW-298 also had bolls that averaged , an 2 grams inweight, but they plotted well the regression‘ line in Figure 1, indicating h degree of susceptibility to pink bollworm ge. ~ e large differences in the number of larvae ered per gram of boll weight for the four ults obtained for the mean boll weights i varieties with mean boll weights of less than 2 grams indicated that greater variation existed in the boll samples of the small-boll than in the large-boll cottons. A test of homogeneity of variances of the number of larvae recovered per gram of boll weight from individual bolls showed highly significant differences between these four cottons and Deltapine 15. There was no signifi- cant difference in the variation of number of larvae recovered per gram of boll weight from in- dividual bolls of G. thurberi, Texas 389 and MW- 298, which had mean boll weights of 0.9, 0.5 and 1.2 grams, respectively. However, there was a highly significant difference between the varia- tion of individual boll records of G. stoclcsii, with a mean boll weight of 0.3 gram, and the variation of the other three small-boll cottons. Results of these tests indicated that the variation in number of larvae recovered per gram of boll weight among individual bolls of small-boll cottons, particularly those with a mean boll weight be- low 2 grams, was significantly greater than for large-boll ones, such as Deltapine 15. Thus, results obtained under conditions of this experi- ment for these small-boll cottons were variable and not as reliable as those for large-boll cottons. A similar test of the Stoneville 2B x G. tomentosum cross, with a mean boll weight of 4.7 grams, and Deltapine 15 revealed no signifi- cant differences in variation of number of larvae recovered per gram of boll weight among in- dividual bolls at the 1 percent level of significance. This indicated that results obtained from bolls as large as those of the Stoneville 2B x G. tomentosum cross or larger would not be affected by the variation in number of larvae recovered from individual bolls. Thus, the results would be more reliable. A comparison of the number of larvae that entered the cotton bolls with the number that survived has been used by some workers as a measurement of resistance. Percentages of larvae that entered the boll and survived are shown in Table 1. The percentage of survival of larvae that entered bolls was plotted against the mean boll weight of the cottons in Figure 2. Lower percentages of larvae survived in G. thurberi, G. stocksii, Texas 389 and the Stoneville 2B x G. tomentosum cross. This is an indication of resistance by these four cottons. However, G. stocksii and Texas 389 appeared to be highly susceptible to pink bollworm damage in the test for resistance shown in Figure 1. G. thurberi and the Stoneville 2B x G. tomentosum cross ap- peared to be resistant in tests shown in Figures 1 and 2. The cross of Stoneville 2B x G. tomentosum was the most resistant cotton of the group tested. However, there was no significant difference in the number of larvae recovered per gram of boll weight for this cotton and Deltapine 15 when tested by group comparisons. Results of the 11 l ‘@113 group comparisons of each cotton with Deltapine 15, indicated that most of the cottons with mean boll weights ranging up to 8 grams were sig- nificantly more susceptible to the pink bollworm than Deltapine 15. The Stoneville 2B x G. tomentosum cross had a mean boll weight of 4.7 grams, yet the‘ difference in number of larvae recovered per gram of boll weight was not significant. Thus, this cotton departed from the pattern set by other cottons with a similar boll size enough to indicate resistance by this test for significance. The apparent resistance of the Stoneville 2B x G. tomentosum cross seemed to be caused by cell proliferation in the cottonseed. Results showed that a high percentage of larvae entered the cotton bolls, but the percentage of survival was low. There was a slight amount of cell proliferation in the carpel Wall where the larvae entered but not enough to kill many larvae. Most of the larvae seemed to survive until they reach- ed the cottonseed. The membranous seed coat prevented first instar larvae from entering the seed directly; therefore, they fed on the outside of the seed until they found a suitable place to enter. Many of the larvae were engulfed by large, clear, granular cells and were killed as they fed over the outer portion of the seed. The cell proliferation seemed to be initiated by insect injury to the seed. Rarely would pro- liferation prevent the formation of normal lint and seed, even when the cotton boll was attacked by several larvae. Most of the larvae recovered -z LARVAE RECOVERED PER GRAN IOLL WEIGHT 2 4 s a co I2 l4 l6 as 20' 22 24 MEAN sou. WEIGHT (cams) Figure 1. Regression of number of larvae recovered per gram of boll weight on mean boll weight for 108 cottons in greenhouse screening experiment for resistance to pink bollworm damage, College Station, Texas, 1954-55: (A) Deltapine 15, (B) G. t/aurberi, (C) Texas 389, (D) MW-298, (E) G. Jtocksii, (F) Stoneville 2B x G. tomentoxum, (G) Hexaploid Z-64, (H) MW-l47. l2 from. this cotton were taken from older" that were not growing rapidly .-and in whi proliferation was not so pronounced. G. thurberi appeared to be resistant y experiment. The percentage survival of that entered the bolls was low, Figure _t the value for larvae recovered per gram " weight plotted against mean boll weight w, below the regression line, Figure 1. Ho the results of the group comparison of t i ton with Deltapine 15, Table 1, indicat significantly more larvae were recover gram of boll weight from G. thurberi. t. tioned earlier, this cotton had a mean boll j of 0.9 gram and was included in the g , cottons that had highly significant differel the variation among individual boll s .7 Also, there was no lint on the seed of this; and the larvae moved about freely inside t) Thus, cannibalism may have been impo , reducing larval populations in these smal This cotton was considered to have some an effect on pink bollworm larvae, but not =1; as the Stoneville 2B x G. tomentosum cro The cause of the apparent resistance! thurberi to pink bollworm also seemed to . proliferation. The percentage of larvae f tered the bolls was low, indicating that th ’ have been repelled by the cotton boll i; manner. However, low percentages of) * entered the other small-boll cottons and th_ be explained by the small boll size = antagonistic tendency of the larvae. Also was a low percentage of survival of larv entered G. thurberi bolls. The young, fas ing bolls would respond to insect inj “u: a 0 0 O PER GENT OF ENTERED LARVAE RECOVERED D o 8 2 4 o I no It M I MEAN BOLL WEIGHT (GRANS) Figure 2. Percentage of survival of larvae that -{J on mean boll weight for 108 cottons in greenho _‘ experiment for resistance to pink bollworm d <1; Station, Texas, 1954-55: (A) Deltapine 15, (B) f‘? (c) Texas s89, (D) MW-298, (E) c. Jtocklii, (F 2B x G. tomentorum, (G) Hexaploid Z-64, (H) crating great masses of granular tissue. ;proliferation of cells seemed to come from ‘ rpel walls where larvae entered and often 1| fill the entire locule of the boll. Pink orm larvae were trapped in this mass of v and many were killed, apparently by nical pressure. The proliferated tissue Was _xic to the larvae because larvae were reared ‘Vsfully in containers using this material for Most larvae recovered from this cotton "found in bolls about 4 weeks old that did roliferate as much as younger bolls. An irable aspect of this phenomenon in G. eri was that the proliferation that killed bollworm larvae usually destroyed the locule Qked, and the entire boll in many cases. able 1 and Figures 1 and 2 indicate that Lloid Z-64 possibly was resistant to pink orm damage. Only 44.1 percent of the if that entered bolls survived and it was g the regression line plotted in Figure 1. _ the degree of resistance in either test did ppear to be outstanding, it was consistent. Field Plot Experiments The criteria used to test the cottons for re- sistance to pink bollworm in the field plot ex- periments were the number of larvae recovered per gram of boll weight, which was a test for antibiotic effects on larvae, and the number of larval entrance holes found in bolls, to test for preference. Bolls that had no larval entrance holes were considered as escaped bolls and in- dicated nonpreference for oviposition by the adult. The number of larvae recovered per gram of boll weight was considered a more valid criterion of resistance than the mean number of larvae re- covered per cotton boll from each cotton. Results, Tables 2, 3 and 4, show that the number of larvae recovered per boll definitely depended on boll size. Therefore, if the number of larvae recovered per boll was used as a measurement of resistance, the small-boll cottons would appear to be more resistant and large-boll varieties more susceptible than Deltapine 15. The use of the Z. RESULTS OF CAGED FIELD PLOT EXPERIMENT 1 FOR RESISTANCE OF 33 VARIETIES OF COTTONS TO PINK BOLLWORM DAMAGE AT COLLEGE STATION. 1954 _ Total Erliltrtlzmce Larvaed Mean mall I r c Lvarvcfie B0115 escaped o es recovere we: e o ere er bolls per boll per boll in grims gram boll lvavt. N°- b°n5 Perwnll ne 152 117 12.8 6.0 12.7 .4921 5 8.54 beri 298 2.3 0.3 0.8 .3888 65 31.48 ui 3 60 24.4 9.4 11 7 .8084 0 0 20 69 18.2 8.4 18.5 .4905 0 0 ~ 21 88 20.3 8.3 16.4 .5293 0 0 -- 24 72 19.0 8.6 11.6 .7781 1 2.27 29 126 20.2 9.4 17.4 .5420 1 2.03 “ s 31 26 27.2 12.3 25.4 .6451 0 0 _s 32 105 ' 14.4 7.2 14.3 .5130 6 13.87 as 34 106 15.1 7.3 18.0 .4049 3 7.80 s 35 92 22.3 9.9 17.9 .5519 1 2.96 s- 37 19 30.4 13.6 23.3 - .5270 0 0 is 40 87 11.7 5.1 14.3 .3731 6 10.30 A- 42 44 9.3 4.8 15.7 .2929 3 6.62 43 109 18.6 8.4 , 17.5 .5056 3 3.92 49 87 20.8 9.0 12.5 .6971 0 0 53 106 16.5 7.8 10.9 .6569 0 0 56 108 17.3 8.0 16.5 .5341 2 3.13 ...—. 61 22 16.5 6.5 11.2 .4488 0 0 1- 62 61 14.1 6.1 8.2 .7054 0 0 .... 63 121 17.5 8.0 13.9 .5923 0 0 64 133 17.8 8.1 12.6 .6544 4 5.86 s 67 99 19.0 8.4 15.7 .4960 1 2.99 99 43 23.0 9.8 18.1 .5813 0 0 -- 100 40 19.8 8.1 11.1 .6448 0 0 s 101 73 10.3 4.7 11.9 .3803 4 10.88 i- 105 62 24.3 8.2 13.4 .7390 1 2.61 108 37 18.3 7.8 11.1 .7056 1 4.03 as 10s a7 21.6 as 11.6 .8360 0 o “as 160 77 19.4 8.2 10.6 .7709 0 0 n. 161 25 18.1 7.4 11.8 .8246 0 -0 ias 168 _ 82 17.1 7.2 11.6 .6265 1 3.42 os 183 f 119 19.2 8.7 13.5 .6835 2 3.26 p at 5% level .1868 8.54 ' at 1% level .2474 11.32 ntages converted to angles. lard cotton. ' 13 number of larvae recovered per gram of boll weight resulted in data which were comparable for all cottons. ‘ Adequate bolls for inclusion in the analyses were obtained in experiment 1 for 32 varieties of G. hirsutum and G. thurberi. The identity of the cottons and results obtained are shown in Table 2. Analysis of the data indicated that significant differences existed between Deltapine 15 and 11 of the cottons in the number of larvae recovered per gram of boll Weight. Significantly more larvae were recovered from 10 of these 11 cottons than from Deltapine 15 and in 5 of these cottons the differences were highly significant. This indicated that these cottons were more susceptible than Deltapine 15 to pink bollworm attack. Texas 42 was the only cotton which contained signi- ficantly fewer larvae per gram of boll weight than Deltapine 15. This significant difference in the case of Texas 42 seemed to indicate resistance of an antibiotic nature until the data presented in Table 2 were examined carefully. Texas 42 had a mean boll weight of 15.7 grams and an average of 9.3 entrance holes per boll was ‘recorded. The respective values for Deltapine 15 were 12.7 grams and 12.8 entrance holes. The trend in average number of entrance holes to mean boll weight shown in Table 2 was for the number of entrance holes to increase as the boll weight in- creased. Texas 42 contained about half the num- TABLE 3. RESULTS OF CAGED FIELD PLOT EXPERIMENT 2 FOR RESISTANCE OF 25 VARIETIES OF COTTONS T01 BOLLWORM DAMAGE AT COLLEGE STATION. 1954 ber of entrance holes that would be expecte. a mean boll weight of 15.7 grams. This s have been because the adults did not prefer cotton for oviposition or because many L hatching on the bolls were repelled in manner by the cotton and did not attem enter the bolls. Results obtained for Tex in the greenhouse experiment, Table 1, su“ the hypothesis that the apparent resi exhibited by this cotton was caused by non erence of adults for oviposition. 7 A highly significant number of bolls t thurberi escaped pink bollworm damage, t 2. This indicated that bolls of this cotton g repelled the larvae or that eggs were not lai‘ the bolls by the adults. v Cottons for which adequate numbers of ; were collected and results obtained in ed ment 2 are shown in Table 3. Three of cottons contained significantly more larvae; gram of boll weight than Deltapine 15, to the 1 percent level of significance and the 5 percent level. G. thurberi contained if larvae per gram of boll weight than Deltapi and the difference was highly significant. y was no significant difference in the nump larvae recovered per gram of boll weight G. thurberi and Deltapine 15 in experime’ A highly significant number of G. thurberf escaped pink bollworm injury in this experi as in experiment 1. TY Bolls escaped Total Entrance Larvae Mean boll Larvae Cotton bolls holes recovered weight recovered per ._ per boll per boll in grams gram boll wt. N°- b°u5 P9‘ Deltapine 152 88 21.5 8.8 13.8 .6295 1 G. thurberi 180 1.1 0.2 1.0 .1890 76 G. hirsutum Texas 195 23 15.7 6.8 10.4 .6281 0 Texas 203 33 10.7 5.6 10.5 .3931 0 Texas 204 79 14.1 7.1 11.1 .6800 5 Texas 205 88 13.5 6.0 9.1 .5494 3 Texas 206 85 15.7 7.3 10.5 .5899 1 Texas 225 55 14.1 6.7 10.6 .6583 1 Texas 226 61 16.7 8.4 13.0 .7030 1 Texas 242 52 15.9 7.6 12.1 .6783 1 Texas 243 44 14.2 6.3 10.8 .6091 1 Texas 245 51 12.5 5.9 10.7 .5614 0 Texas 294 88 14.9 6.1 9.4 .6753 3 Texas 366 16 ~ 10.3 3.1 4.6 .7009 2 Texas 382 87 23.3 10.8 17.2 .6819 0 Texas 384 68 23.4 11.8 19.4 .6194 0 Texas 395 130 6.1 2.2 3.1 .6966 11 Texas 398 83 7.9 3.9 4.1 .9388 2 Texas 399 83 10.9 5.3 5.3 1.9531 4 Texas 402 76 9.4 4.7 4.6 1.0075 1 Texas 409 139 15.2 6.7 7.4 .8851 1 Texas 420 118 20.6 9.3 13.6 .6804 0 Texas 423 59 19.2 8.9 12.7 .7453 2 Texas 516 92 19.7 7.5 9.1 .7622 2 Texas 523 112 18.0 8.1 10.5 .8802 0 L.S.D. at 5% level .2652 - .3522 L.S.D. at 1% level ‘Percentages converted to angles. "Standard cotton. 14 j he experiment conducted in 1955 was de- f to obtain additional data for G. thurberi. cottons included were G. thurberi, Deltapine 7nd Pima (G. barbadense). More plants of cotton were included in each replicate and »ink bollworm infestation was higher than t g 1954. This procedure was followed to in‘ larger, more representative boll samples insure that G. thurberi bolls were not ac- tally escaping pink bollworm injury. Re- f. obtained are shown in Table 4. Analysis of ‘data indicated no significant differences in ‘lumber of larvae recovered per gram of boll ht. However, in this experiment, as in both riments of the previous year, a highly signi- n number of G. thurberi bolls escaped pink Vorm injury. t he results obtained for the number of larvae vered per gram of boll weight for G. thurberi p be explained to some extent by the difference jean number of larval entrance holes per boll 1G. thurberi for the three experiments. It was v med that the number of larval entrance holes ‘boll was an indication of the level of larval tation to which the bolls were exposed. The ‘ge number of larval entrance holes per ‘for G. thurberi was 1.1, 2.3 and 3.1 for ex- ents 2 and 1 of 1954 and the 1955 experi- t, respectively. The number of larvae re- red per gram of boll weight in the same r of experiments was 0.1890, 0.3888 and A: Thus, as the level of larval infestation Zhe bolls increased, the number of larvae re- red per gram of boll weight increased. The F apparent conclusion to make from these ,- was that the G. thurberi bolls in experiment 1954 were not infested to the same degree he other cottons. There were no significant erences in the number of larvae recovered per ‘ of boll weight from G. thurberi in the other experiments when the bolls were exposed to er populations of pink bollworm larvae. i he most significant information obtained the field plot experiments conducted during and 1955 was that a highly significant num- F of G. thurberi bolls escaped pink bollworm ,.ge in all experiments. This is particularly nding in view of the conditions under which 1955 experiment was conducted. The insect tation was increased from 150 to 200 moths 1/200-acre plot. The ratio of G. thurberi plants to other cottons in the 1954 experiments was 1 to 35 or 40. In 1955, there was one G. thurberi plant for every two plants of other cot- tons. This procedure resulted in practically forcing the insect to G. thurberi. Yet, highly significant numbers of bolls escaped insect in- jury. The indicated resistance in G. thurberi appeared to be the result of nonpreference of the adults for oviposition. Two possible explanations of why G. thurberi bolls escaped pink bollworm damage were: the eggs were laid on the bolls or vegetative parts, but the larvae were repelled by the fruit for some reason and migrated from it, or the bolls and vegetative parts of G. thurberi were not preferred for oviposition. The data of the greenhouse screening experiment showed that 31.7 percent of the larvae placed on bolls entered the bolls. This indicated that extensive migration from the G. thurberi bolls occurred, but most of the bolls contained at least one larval entrance hole. This extensive larval migration is normal for the small-boll cottons such as G. thurberi. These facts do not support the theory that G. thurberi bolls repelled pink bollworm larvae. There was more evidence that supported the hypothesis that G. thurberi bolls and vegetative parts were not preferred for oviposition by the adult and, as a result, the bolls of this cotton contained lower levels of larval infestation than the other cottons in the caged plots. Tables 2, 3 and 4 show that as the average number of larval entrance holes per boll and the larvae recorded per gram of boll weight for G. thu/rberi increased, the percentage of bolls that escaped injury de- creased. It was assumed that the reason the bolls escaped injury was that the moths did not oviposit as readily on G. thurberi as on the other cottons. Thus, nonpreference may have been the cause of the apparent resistance of G. thurberi under the conditions of the field plot experiments. A significant number of bolls of Texas 204 escaped pink bollworm damage in experiment 2, Table 3. However, the third replicate of the ex- periment produced only two bolls of Texas 204 and one of them escaped pink bollworm injury. Data from this small sample of bolls perverted the results when averaged with data from the other replicates; therefore, the indicated signifi- cance for Texas 204 was disregarded. _ 4. RESULTS OF CAGED FIELD PLOT EXPERIMENT FOR RESISTANCE OF PIMA AND G. THURBERI TO PINK BOLLWORM DAMAGE AT COLLEGE STATION, 1955 Total Entrance Larvae Mean boll Larvae 3011s escaped . on bolls holes recovered weight recovered per ‘ ' per boll per boll in grams gram boll wt. N°- b°ll5 Pement >11... 1s= i. 23a '24.1 2.7 15.3 .5678 1 2.1a 262 27.7 8.1 13.2 .6406 0 0 urberi 642 3.1 0.6 1.0 .6883 51 16.21 10.43 _. at 1% level . ntages converted to angles. ard cotton. 15 Another point of interest illustrated in both the greenhouse screening experiment and experi- ment 2 of 1954 was the apparent high suscepti- bility of the Hopi cottons to pink bollworm attack. These cottons were listed in Tables 1 and 3 as Texas 395, 398, 399, 402 and 409. The mean boll weight ranged from 2.9 to 7.2 grams. Sur- vival of larvae entering the bolls ranged from 66.4 to 80.0 percent. These are relatively high values for such small-boll cottons. Larval re- covery per gram of boll weight for Texas 402 in the field plot experiment, with a mean boll weight of 4.6 grams, was 1.0075. This is an ex- tremely high value for larval recovery and the other Hopi varieties showed the same tendency in all experiments. Detailed observations of the feeding habits of pink bollworm larvae indicated that larvae began feeding on lint and the outer seed coat after entry into green cotton bolls with immature seed. The cottonseed were not entered until the seed became firm inside. After larvae began feeding on the seed, they completed development on one or two adjacent seed. However, larvae feeding outside the seed moved about in the bolls con- siderably, resulting in frequent contact with other larvae and increased larval mortality in- side the cotton boll. The Hopi cottons matured earlier than the other cottons in these experiments. Therefore, seed of Hopi were suitable for larval entry be- fore those of Deltapine 15 and the other cottons. Bolls of all cottons were infested with pink boll- worms at approximately the same age. There- fore, larval mortality was lower inside the more mature Hopi bolls than in Deltapine 15 bolls because the larvae were able to enter mature seed earlier and feed in a relatively protected spot. Oviposition Experiments Results of the 1954 field plot experiments, as presented in the preceding section, indicate that highly significant numbers of G. thurberi bolls were escaping pink bollworm damage. The es- cape of bolls from pink bollworm damage was observed early enough in the 1954 season to per- mit preliminary tests to determine why. The TABLE s. LOCATION or EGGS DEPOSITED ON BOLLS BY PINK BOLLWORM ADULTS ON SPECIES or‘ co i INDICATED AT COLLEGE STATION. 1954 most likely explanation seemed to be t bolls escaped injury because the moths dig oviposit as readily on G. thurberi bolls as on; of other cottons present in the cages. ' In test 1, adjacent rows of Deltapine 1 G. thurberi were caged together. The, mean ” ber of eggs found per boll for Deltapine 15, _ 5, was 19.6 and 1.2 for G. thurberi. Perce I of bolls that escaped oviposition were 5. j 79.1 for Deltapine 15 and G. thurberi, resp ly. These results indicated that Deltapi bolls were preferred for oviposition to G. th A and resulted in significant numbers of the of G. thurbe/ri escaping injury. The location of the pink bollworm eggs on the G. thurberi bolls was different from location on bolls of Deltapine 15. The .5 bution of the eggs on Deltapine 15 was 56. cent under the calyx, 42.4 percent on t inside the bracts and 1.2 percent below the f around the nectaries. All the eggs found i thurberi bolls were around the base of thy, in a tight groove formed by the calyx and ’ This groove was found only on bolls 3 more old, in which the enlarged circumf of the boll forced the calyx basally and ca i1 to bulge outward at the point of attac . Thus, eggs were found only on the old thurbewl bolls. The significant point illus by this test was that no eggs were found“ the calyx of the bolls of G. thurberi, the 1 ~: that generally was considered to be prefer the moth for oviposition. Test 2 conducted during 1954 was de" to force the insect to oviposit on G. thurberi; test was conducted simultaneously with test I in the same manner except that only G. tho plants were present in the cage.‘ The resul shown in Table 5. Eight eggs were found; the calyx of two bolls. The calyx of bot‘ had split and was abnormal. The re , of the eggs were found in the same loca the G. thurberi bolls as described for . When the moths were forced to oviposit '1' thurberi, the average number of eggs fou boll increased to 4.2, and the bolls that -; with no eggs decreased to 52.9 percent. - significant that such a large number of S; Cotton Under calyx On boll‘ Below bract” Total Total Eggs Bolls e n‘ No. Per- No. Per- No. Per- eggs bolls per No. e995 cent eggs cent eggs cent b°u bolls Test 1 Deltapine 15 419 56.4 315 42.4 9 1.2 743 38 19.6 G. thurberi 0 0 137 100.0 0 0 137 110 1.2 Test 2 ‘ G. thurberi 8 2.3 347 97.7 0 0 355 e 85 4.2 ‘Eggs found inside the bracts but not under the calyx. zfiggs iouncl below the bracts around the nectaries. l6 -. selection for oviposition when the cotton xposed to a high level of pink bollworm tion without other cotton. .' on them. on this cotton. the morphological The results parently, these results indicated that either ink bollworm moths were repelled by tropic factors, g teristics of this cotton did not afford suit- ites for the moths to oviposit. t 1 tend to eliminate the theory of tropic factors causing the moths to prefer ‘sine 15 bolls. With Deltapine 15 bolls avail- or oviposition in the cage, 20.9 percent of . thurberi bolls had pink bollworm eggs de- g It seemed reasonable that, ; the conditions of this test, if the moths iirepelled by some chemical constituent of G. eri bolls, more of the eggs would have been 1 the Deltapine 15 bolls. p e difference in morphological characteris- f G. thurbem’ bolls apparently was the cause e nonpreference of the moths for oviposi- Therefore, tests were con- .1 in 1955 to determine the effects of various hological differences in vegetative and fruit- arts of several cottons on the location and rs of eggs deposited by pink bollworm ' The results of seven tests are given in 6, 7 and 8. ink bollworm moths deposited 'more eggs fr the calyxes and fewer on the bolls of G. herbaceum. This reduction of the percentage of eggs laid on the bolls apparently was caused by the bracts of G. herbaceum flaring away from the boll, leaving the smooth boll completely exposed. It has been observed that pink bollworm moths do not oviposit on smooth, open surfaces. Ap- parently the egg-laying reaction must be “trigger- ed” by the stimulus resulting from placing the abdomen and ovipositor into a crevice or close- fitting place. Thus, the only suitable location for oviposition on G. herbaceum bolls was under the calyx. These results indicated that a dif- ference in the structural parts of the cotton boll caused a difference in the preferred location for egg-laying of pink bollworm moths. The vegetative characters of Texas 536 ap- parently were unattractive to the pink bollworm moth for oviposition since no eggs were found on the vegetative parts. Thus, all the eggs on this plant were laid on the bolls. The distribution of eggs on the bolls was in the same proportion as for Deltapine 15 but more eggs were found per boll on Texas 536 than for Deltapine 15. The narrow bracts did not seem to affect the pre- ference of the pink bollworm moth for oviposition. Apparently, the structural characters of the vegetative parts of Pima provided a better location for pink bollworm oviposition than did the fruiting parts. In all tests that included Pima, except one, the percentage of eggs laid on the vegetative parts was higher than that laid i: 6. NUMBER AND PERCENTAGE OF PINK BOLLWORM EGGS DEPOSITED ON VEGETATIVE PARTS OF SEVERAL ‘ COTTONS AS INDICATED AT COLLEGE STATION. 1955 Terminals Axils . on NO- N Total plants o. Per- No. Per- No. Per- eggs eggs cent eggs cent eggs cent 1 Test 1 ine 15 10 109 24.8 110 25.0 ~ 221 50.2 4401 ; baceum 10 54 21.9 67 27.1 126 50.0 247 ’ bruct 4 33 24.4 21 15.6 81 60.0 135 l . Test 2 ine 15 5 44 17.0 107 41.5 107 41.5 258 “f 5 54 24.5 3 1.4 163 74.1 220 Test 3 e 15 6 49 17.4 22 7.8 211 74.8 282 6 238 49.8 5 1.0 235 49.2 478 , Test 4 ine 15 3 8 22.9 4 11.4 23 65.7 35 ‘ 536 6 0 0 0 0 0 0 0 10 184 46.6 0 0 '211 53.4 395 t Test 5 ine 15 6 108 29.0 37 10.0 227 61.0 372 r 6 1.081 72.9 9 0.6 392 26.5 1.482 - beri 6 33 17.6 0 0 155 82.4 188 Test 6 ine 15 5 80 24.5 56 17.1 191 58.4 327 5 100 38.3 0 0 161 61.7 261 p beri 6 5 12.2 0 0 36 87.8 41 Test 7 pine 15 5 33 12.9 5 1.9 219 85.2 257 5 339 83.1 3 0.7 66 16.2 408 beri 10 4 7.1 0 0 52 92.9 56 17 on the fruiting parts. The larger number of eggs found 0n the leaves of Pima indicated that they were preferred to the axils or terminals for oviposition. Also, more eggs were found on the leaves of Pima than on the leaves of Deltapine 15. This apparently was caused by the coarser pubescence and the larger leaf veins of Pima. The percentage of eggs found under the calyx of Pima bolls not over 3 weeks old was smaller than the percentage found on older bolls. After the bolls became 4 weeks or older, more eggs were found under the calyx than on the boll. This was caused by the split and distorted calyx of older Pima bolls. The calyx would split when the circumference of the growing boll became too large for it. The moths would oviposit under the calyx at the splits. Relatively few eggs were found under the undamaged calyx of younger bolls. Apparently, the calyx was fitted too tightly for the pink bollworm moth to insert the ovipositor under it. _Results of the tests in which G. thurberi was included indicated that the morphological char- acters of this cotton exerted a marked influence on the number and location of eggs laid by the pink bollworm moth. Significant numbers of the bolls of this cotton in all tests escaped oviposition and injury by the pink bollworm. The numbers of eggs found in all oviposition sites on G. thur- TABLE 7. NUMBER AND PERCENTAGE OF PINK BOLLWOBM EGGS DEPOSITED ON FRUITING PARTS OF COTTONS AS INDICATED AT COLLEGE STATION, 1955 i . distorted points of the calyx. Eggs were 1f beri were significantly lower than for th' cottons tested. The ratio of eggs found o, tative to fruiting parts was about 50-50. -_ found under the calyx were located at br on the bolls until the latter were approxi n,‘ weeks or more old. In many cases when thurberi boll became fully grown, the cir ence of the boll became too large for th. Rarely did the calyx split, but it usua, pushed downward toward the base of the remained tight and smooth against the A the outer edge. The result was the form, a narrow, tight groove between the outsid... calyx and inner side of the bracts at the i the boll. This was the point at which =. were found on normal bolls of this cotton? results indicated that no favorable site f bollworm oviposition existed on G. thurb“ until they were 3 weeks or more of age. f outstanding feature of these experime, the very small number of eggs found per I per plant of G. thurberi compared with g cottons. Thus, the vegetative parts also = a poor sites for pink bollworm oviposition. The results of test 7, Tables 6, 7 and l’ cated ‘that the vegetative parts of Pima =. tapine 15 were preferred for ovipositio thurberi with fruit present. The ovipositi’ N Squares Under calyx On boll‘ Below bract” o. C°t1°n plants No. Per- No. Per- No. Per- No. Per- eggs cent eggs cent eggs cent eggs cent Test 1 Deltapine 15 1O O O 81O 61.9 425 32.5 74 G. herbaceum 1O O O 1,118 96.1 37 3.2 8 Frego bract 4 O O 304 71.7 112 26.4 8 Test 2 Deltapine 15 5 O O 16O 30.9 326 63.1 31 Pima 5 O O 83 53.9 71 46.1 O Test 3 Deltapine 15 6 O O 397 35.2 677 60.0 54 Pima 6 O O 128 43.7 165 56.3 O Test 4 Deltapine 15 3 O O 81 82.7 17 17.3 O Texas 536 6 O O 195 82.3 42 17.7 O Pima 1O O O 129 56.8 98 43.2 O ’ Test 5 Deltapine 15 6 O O 722 44.7 862 53.3 32 . Pima 6 O O 694 47.9 742 51.3 12 G. thurberi 6 O O 2 2.8 7O 97.2 O Test 6 Deltapine 15 5 O O 45O 48.7 427 46.3 46 Pima 5 O O 436 77.0 13O 23.0 O G. thurberi 6 O O 13 16.0 68 84.0 O Test 7 Deltapine 15 5 No fruit" Pima 5 No fruit‘ . G. thurberi 1O O O O O 12 100.0 O ‘Eggs found inside the bracts but not under the calyx. ‘Eggs found below the bracts around the nectaries. sFruit removed from Deltapine 15 and Pima. 18 k on the vegetative parts of these two cot- were more suitable for stimulating the egg- reaction of the pink bollworm moth than thbe sites on fruits and vegetative parts of m" em. a _e results of the oviposition tests indicated a orphological differences of the cotton plant w modifications of the oviposition habits of ink bollworm moth. Fruit characteristics of "lstraight calyx and flared or deciduous bracts ently made the fruiting parts ‘unattractive iposition. Characters of heavy, prominent j the leaf blade and pubescence on the en- egetative parts of the plant made the vege- parts more attractive for oviposition. If V characters could be obtained in one cotton, a shift of the preferred place of oviposition ‘the protected sites on the fruit to the open ‘ tive parts might be expected. Such a shift w enable predators and parasites to become ‘effective as natural control measures. In ion, the larvae would be forced to migrate in h of fruit to survive and greater mortality 1 result. The exposure of the larvae to chem- would be greater during migration in search of food and should give more efficient chemical control. The literature revealed that most of the major cotton pests that oviposited on an open, unpro- tected portion of the cotton plant had extremely high reproductive potentials. According to Little and Martin (1942) the cotton leafWorm, Alabama argillacea (Hbn.), laid an average of 500 eggs. The bollworm, Heliothis zea (Boddie), Was re- corded as laying over 3,000 eggs. The tobacco budworm, H eliothis virescens (F.) , may lay over 1,000 eggs. Of the insects that‘ lay eggs in a‘ pro- tected site, the pink bollworm may lay 100 to 200 eggs. The boll weevil, Anthonomzts grandis Bohl, lays about 100 eggs. The cotton fleahopper, Psal- lus seriatus (Reut.), .lays approximately 30 eggs. These data indicated that an insect which ovi- posits in an open, unprotected site needs a higher reproductive potential to insure survival. Thus, any change in the host plant that would result in a preference of exposed sites for oviposition by the pink bollworm, Which has a relatively low re- productive potential, could be detrimental to the survival of this pest. 8. PINK BOLLWORM EGGS DEPOSITED ON VEGETATIVE AND FRUITING PARTS OF COTTON PLANTS. WITH VARIOUS MORPHOLOGICAL DIFFERENCES AT COLLEGE STATION. 1955 Vegetative Fruiting Total Eggs J _ on No. parts parts bolls per Total Plants No. Per- No. Per- counted ha“ eggs eggs cent eggs cent " ' _ ; Test 1 ine 15 10 440 25.2 1,309 74.8 103 17.0 1.749 " baceum 10 247 17.5 1.163 82.5 106 13.2 1.410 bract 4 135 24.2 424 75.8 21 ‘ 20.2 559 1 l. Test 2 ‘ 15 5 . 258 33.3 517 66.7 40 19.4 775 t 5 220 58.8 154 41.2 47 8.0 374 g Test 3 - ine 15 6 282 20.0 1.128 80.0 1 57 19.8 1.410 6 478 62.0 293 38.0 55 5.3 _ 771 . Test 4 ' ine 15 3 35 26.3 98 73.7 20 4.9 133 1 536 6 0 0 237 100.0 33 7.2 237 10 395 63.5 227 36.5 118 1.9 622 - Test 5 ine 15 6 372 18.7 1.616 81.3 43 37.6 1.988 6 1.482 50.6 1.448 49.4 42 34.5 2.930 urberi 6 188 72.3 72 27.7 102 0.7 260 l_ Test 6 ine 15 5 327 26.2 923 73.8 45 20.5 1.250 5 261 31.6 566 68.4 34 16.6 827 rberi 6 41 33.6 81 66.4 236 0.4 127 Test 7 ine 15 5 257 100.0 No fruit‘ 257 5 408 100.0 No iruitl 408’ vurberi 10 56 30.5 128 69.5 159 0.8 184 removed from Deltapine 15 and Pima. 19 BIBLIOGRAPHY Adolph, Edward F. 1920. Egg-laying reactions of the pomace fly, Drorop/aila. jour. Expt. Zool. 31: 327-341- Anson, R. R., R. L. Knight, and S. Evelyn. 1945. Progress report of the plant breeding stations, bollworm resistance. Empire Cotton Growing Corp. Rpt. Expt. Stas. 1943-44! 67-68. Audant, A., and A. 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