' 



Considerably higher dosages of toxaphene, dieldrin, and aldrin were required 

 for a kill of weevils in late September and October comparable to that obtained in 

 August. It is assumed that certain factors other than environmental greatly affect 

 the toxicity of these insecticides. These factors probably involve the physiology 

 of the weevil, itself. 



No differences were found in the toxicity of toxaphene sprays made from 

 miscible oil concentrates containing 3 different emulsifiers in tests for boll 

 weevil control. In tests for control of the salt-marsh caterpillar, there was a 

 difference in the toxicity of the sprays made from oil concentrates containing 

 these different emulsifiers. The toxicity of 2 of the emulsifiable sprays was 

 reduced by the simulated rain in the experiment in which salt-marsh caterpillars 

 were used as the test insects. Apparently the type of emulsifier used in making 

 the miscible oil concentrate affects the toxicity of the spray emulsion as well as 

 its residual toxicity following rains. 



One-half inch of simulated rain greatly reduced the toxicity of toxaphene- 

 sulfur dusts. The addition of either oil or a commercial sticker to toxaphene- 

 sulfur dusts had little or no effect on the residual toxicity following simulated 

 rain. 



1951 - Hanna, R. L., and J. C. Gaines. Lime-free calcium arsenate mixed with organic 

 insecticides for cotton insect control. J. Econ. Ent. 44(3):430-432. 



Previous experiments at this station have indicated that lime-free calcium 

 arsenate mixtures containing 1% gamma benzene hexachloride or 0.5% parathion 

 were at least as effective as 20% toxaphene-40% sulfur or 3% gamma benzene 

 hexachloride- 5% DDT- 40% sulfur for controlling the boll weevil and that 1% 

 gamma benzene hexachloride or 0.5% parathion added to the calcium arsenate 

 would prevent the buildup of aphids on the treated cotton. 



Tests conducted during the 1950 season generally confirmed this previous 

 work. One experiment demonstrated that calcium arsenate- 1% gamma benzene 

 hexachloride, calcium arsenate-0.5% parathion, and 20% toxaphene-40% sulfur 

 were equally effective in controlling a severe infestation of boll weevils and a 

 moderate infestation of bollworms. Calcium arsenate-0.5% parathion gave 

 better control of boll weevils than 10% chlordane-5% DDT. 



The results of 3 seasons' tests in the Brazos River bottoms near College 

 Station, Texas, indicated: (1) that lime-free calcium arsenate plus 1% gamma 

 benzene hexachloride or 0.5% parathion is at least as good as any insecticide in 

 general use for controlling boll weevils; (2) that, except in extreme cases, the 

 percentages of benzene hexachloride or parathion, as mentioned above, will pre- 

 vent a buildup of aphids on cotton treated with these mixtures; (3) that the addi- 

 tion of as much as 2.5% DDT to these mixtures gives excellent bollworm control. 



1951 - Isely, D., and G. Barnes. Boll weevil control in late summer,, Ark. Agr. Expt. 

 Sta. B. 510. May. 



BHC, 3-5-40, and calcium arsenate were tested late in the summer of 1950. 

 Although the number of punctures were never reduced below 30%, the data sug- 

 gests that the greatest return from dusting will be gained if control measures are 

 concentrated in periods during which cotton is fruiting most rapidly and if controls 

 are continued as long as needed. 



1951 - Lincoln, Charles. Boll weevil infestations and control in eastern Arkansas in 

 1950. J. Econ. Ent. 44(5):766-769. 



Boll weevil infestations were extremely variable in eastern Arkansas early 

 in the summer of 1950. During June and July early planted cotton was more 

 heavily infested than later cotton. Infestations built up to high levels in August in 

 all areas under consideration, including areas with extremely light early infesta- 

 tions. Despite heavier infestations by overwintered and first-generation weevils, 

 control was easier in early cotton because it required a shorter period of protec- 

 tion from weevils of the second and later generations. 



Application of insecticides early in the season did not reduce later infesta- 

 tions sufficiently to reduce the necessity of control measures later in the season. 



56 



