cotton squares. Mortalities were determined at the end of 72 hours. Approxi- 

 mately 25,000 weevils were used in the experiments. During 1957, LD-50 values 

 varied among populations from different localities as follows: for toxaphene, 

 from 12.5 to 6l.8(xg. per gm. of boll weevil; for endrin, from 0.8 to 3.5ug. 

 per gm; for Guthion, from 0.9 to 2.3 jig. per gm. There was no evidence of 

 acute resistance of the boll weevil from any of 5 localities to any insecticide 

 tested. Mortality variations between times of year and between the 2 years 

 were as great as among locality groups. 



I960 - Cowan, C. B„, Jr., J. W. Davis, and C. R. Parencia, Jr. Field experiments 



against several late-season cotton insects in 1959. J. Econ. Ent. 53(5):747-749. 



Strobane-DDT was as effective against the boll weevil and the bollworm 

 (Heliothis zea (Boddie)) as tcxaphene-DDT Guthion- DDT gave better control of 

 the boll weevil than Shell SD-3562 and Shell SD-4402, but it was no better than 

 Shell SD-5539-DDT. Sevin gave better boll weevil control than Geigy G-30494- 

 DDT, but it was not better than Bayer 25141. There was no difference in boll 

 weevil and bollworm control obtained with Sevin applied in a dust or in a wettable 

 powder formulation. Shell SD-4402 was effective against bollworms but Shell 

 SD-3562 was ineffective. Bayer 25141 at dosages used was less effective than 

 standard materials. There was no difference in control of the cotton aphid 

 Aphis gossypii Glov.) and the desert spider mite ( Tetranychus desertorum 

 Banks) with demeton, ethion, Trithion, Bayer 25141, Shell SD-3562 and Geigy 

 G- 30494. Sevin, Shell SD-3562, and Shell SD-4402 were as effective as methyl 

 parathion against the cotton leafworm ( Alabama argillacea (Hbn.)). Bacillus 

 thuringiensis showed some promise in the control of this insect. 



I960 - Hightower, B. G., and J. C. Gaines. Residual toxicities of insecticides to cotton 

 insects. Tex. Agr. Expt. Sta. B. 951. Mar. 



Results of experiments conducted to determine the effect of natural or 

 simulated climatic conditions on the residual toxicities of several chlorinated 

 hydrocarbon and organo-phosphorus insecticides to several species of cotton 

 insect pests. In tests with the boll weevil, endrin and Sevin appeared to have 

 similar residual properties. Based on residual properties alone, toxaphene and 

 dieldrin ranked with endrin and Sevin, but the initial toxicities of endrin and 

 dieldrin were greater than toxaphene. Mortality rates for these insecticides 

 were reduced 20% to 30% after exposure to simulated wind and rain. Residual 

 properties of aldrin and BHC were inferior; heptachlor was erratic. Guthion 

 exhibited the best residual properties against the boll weevil of the organo- 

 phosphorus materials. 



I960 - Parencia, C. R., Jr., and C. B. Cowan, Jr. Increased tolerance of the boll weevil 

 and cotton Fleahopper to some chlorinated hydrocarbon insecticides in central 

 Texas in 1958. J. Econ. Ent. 53(l):52-56. 



The boll weevil and cotton fleahopper ( Psallus seriatus (Reut.)) showed in- 

 creased tolerance to several of the chlorinated hydrocarbon insecticides in 

 central Texas in 1958. Topical-application studies on weevils reared from 

 squares collected from one field in July indicated increased tolerance to 

 toxaphene and a high tolerance to dieldrin. In field experiments much better 

 control was obtained with Sevin (1-naphthyl N-methyl carbamate) and such 

 organic-phosphorus compounds as Guthion (0,0-dimethyl S-(4-oxo- 3H- 1,2,3- 

 benzotriazine-3-methyl) phosphorodithioate) and malathion than with toxaphene 

 and dieldrin. Dosages of toxaphene, dieldrin, and heptachlor, 2 and 3 times 

 those effective in previous years, failed to control the cotton fleahopper. Sevin, 

 Guthion, malathion, toxaphene plus DDT, dieldrin plus DDT, and DDT alone 

 were effective, but DDT has not been used against the cotton fleahopper for 10 

 years in the area. 



1960 - Parencia, C. R., Jr., C. B. Cowan, Jr., and J. W. Davis. Control of several 

 early-season cotton pests with insecticides. J. Econ. Ent. 53(6):1 051- 1054. 



A mixture of toxaphene plus DDT and Guthion (0,0-dimethyl S-(4-oxo- 

 l,2,3-benzotriazin-3-(4H)-ylmethyl) phosphorodithioate) or methyl parathion 



80 



