late-season pests as aphids, spider mites, and 

 bolhvorms. In the Brazoria County experiment, 

 the diapause weevil control program in the fall 

 of 1961 and a systemic insecticide treatment 

 in the spring of 1962 were used. Approximately 

 900 of the 1,050 acres of cotton in the test pro- 

 duced an excellent crop without midseason or 

 late-season insecticide treatments. Insect con- 

 trol requirements on the remaining 150 acres 

 were greatly reduced. In Maverick County, 

 1,650 acres were treated one to three times in 

 the fall of 1961 to destroy diapausing boll 

 weevils, at a cost of $1 to $3 per acre. During 

 1962, only 650 acres of this cotton received the 

 recommended practices for this experiment. 

 Early-season insects were not a problem. Ap- 

 proximately 425 acres of this cotton were pro- 

 duced without insecticide treatment in 1962. 

 The insect control costs were greatly reduced 

 on the remaining acres. 



23. Brazzel, J. R., Davich, T. B., and Har- 

 ris, L. D. A new approach to boll weevil con- 

 trol. Jour. Econ. Ent. 54: 723-730. 1961. 



Late-season applications of insecticides were 

 made on 525 acres of cotton in the Big Bend 

 area of Texas during 1959 to reduce the over- 

 wintering population of boll weevils. Four ap- 

 plications of methyl parathion were made on a 

 12- to 14-day schedule beginning just before 

 harvest and continuing until frost killed the 

 cotton. The purpose was to kill the weevils 

 before diapause was attained. Overwintering 

 weevils were substantially reduced in the 

 treated area. The delay of buildup of the popu- 

 lation appears great enough to delay the start of 

 control programs sufficiently to effect substan- 

 tial savings in the cost of control. The program 

 offers some promise as a tool in boll weevil 



24. Brazzel, J. R., and Shipp, O. E. The 

 status of boll weevil resistance to chlorinated 

 hydrocarbon insecticides in Texas. Jour. Econ. 

 Ent. 55: 941-944. 1962. 



Weevils were collected from 20 acres in Texas 

 in 1960 and treated with endrin and toxaphene. 

 The response of boll weevils to methyl para- 

 thion, Methyl Trithion, and Sevin, in 1960-61 

 indicated four general areas of the State with 

 chlorinated hydrocarbon resistance levels suffi- 

 cient to prevent economic control with these in- 

 secticides. There was evidence of reversion to 

 susceptibility in the Mumford area, where re- 

 sistance was observed in 1956. There was no 

 evidence of resistance to the organophosphorus 

 and carbamate insecticides tested. 



25. Bull, D. L. Metabolism of Di-Syston 

 by insects, isolated cotton leaves, and rats. 

 Jour. Econ. Ent. 58: 249-254. 1965. 



Di-Syston was absorbed, metabolized, and 

 excreted rapidly by fifth-instar bolhvorms and 

 adult boll weevils. Insects excreted the toxic 

 oxidative derivatives as well as the hydrolytic 



products of Di-Syston metabolism, but rats 

 slowly excreted only hydrolytic products. 



As many as four oxidative and nine hydro- 

 lytic metabolites of Di-Syston were detected in 

 the biological systems used. The oxidative prod- 

 ucts included the sulfoxide and sulfone deriva- 

 tives of Di-Syston and of the oxygen analog 

 of Di-Syston. In animals and plants, the initial 

 oxidative reaction with the Di-Syston molecule 

 occurred at the mercapto sulfur atom. In plants, 

 Di-Syston was converted almost quantitatively 

 to its sulfoxide derivative during the first few 

 minutes after treatment. The chief hydrolytic 

 products of Di-Syston metabolism were diethyl 

 phosphate and O, O-diethyl phosphorothioate. 

 In addition, small concentrations of ethyl phos- 

 phate, phosphoric acid, and five unidentified 

 products were detected in certain samples. 

 0, O-diethyl phosphorodithioate was not formed 

 in insects or plants, but trace amounts of the 

 metabolite were detected in the urine of treated 

 rats. Similar products were formed in the 

 different biological systems, but the rates of 

 metabolism varied considerably. 



26. Bull, D. L., and Lindquist, D. A. Me- 

 tabolism of radio-labeled SD-3562 in insects 

 and cotton leaves. Ent. Soc. Amer. Bui. 8: 

 154. 1962. 



The absorption and in vivo metabolism of 

 C 14 or P 32 labeled SD-3562 by bollworms, boll 

 weevils, and excised cotton leaves were studied; 

 standard radiometric techniques were used. 



27. Bull, D. L., and Lindquist, D. A. Me- 

 tabolism of 3-hydroxy-N, N-dimethyl croton- 

 amide dimethyl phosphate by cotton plants, 

 insects, and rats. Jour. Agr. Food Chem. 12: 

 310-317. 1964. 



Radiometric techniques were used to inves- 

 tigate the nature and rate of the in vivo 

 metabolism of Bidrin in cotton plants, adult 

 boll weevils, fifth-instar bollworm larvae, and 

 white rats. In all the biological materials oxi- 

 dative demethylation of the toxicant to its 

 equally toxic N-methyl derivative occurred. All 

 toxic products decomposed rapidly, however. Of 

 nine phosphorus-containing metabolites de- 

 tected, tentative identification was made of six 

 hydrolytic and two oxidative products. 



Boll weevils were treated topically. Absorp- 

 tion and excretion studies were made. 



28. Bull, D. L., and Lindquist, D. A. The 

 effects of chronic doses of an organophos- 

 phorus inhibitor on cholinesterase activity in 

 boll weevils. Experientia 21 : 262-263. 1965. 



Weevils were fed sublethal Bidrin treated and 

 untreated diets. Both groups degraded non- 

 toxic, topical doses of C 14 labeled Bidrin at 

 equivalent rates. Weevils held on treated diets 

 were always more susceptible to topical and 

 oral doses of Bidrin than those from the un- 

 treated diet. The in vitro inhibition of ChE by 

 OP insecticides was always significantly greater 

 in insects from the treated diet. 



