insecticides tested, except CS-645A, and for the delta and alpha isomers of benzene 

 hexachloride. 



Significant contact action was demonstrated for aldrin, dieldrin, and benzene 

 hexachloride. That for benzene hexachloride was largely attributable to the 

 gamma isomer. 



Toxaphene, chlordane, and compound CS-645A kill largely by stomach action. 

 Stomach action contributes greatly to total effect from all 8 primary insecticides 

 tested. 



1950 - Parencia, C. R., Jr., and K. P. Ewing. Late- season control of boll weevil and 

 bollworm with dusts and sprays. J. Econ. Ent. 43(5):593-595. 



Insecticides applied as dusts and as low-volume sprays were tested in a 

 single small-plot, and in several large-scale, field experiments at Waco, Texas, 

 during 1949 against late- season infestations of the boll weevil and the bollworm, 

 Heliothis armigera (Hbn.). A 2.5% dieldrin dust gave better results than a 20% 

 toxaphene dust in the small-plot experiment conducted for control of the boll 

 weevil. A dust containing 2.5% of aldrin, 5% of DDT, and 40% of sulfur gave 

 results approximately equal to that of a 20% toxaphene dust in 2 experiments 

 against the boll weevil. In each of 3 experiments records of square-infestation 

 showed that 20% toxaphene dust gave better control of the boll weevil than did 1 0% 

 or 7.5% chlordane mixed with 5% DDT. In the small-plot experiment the yield 

 was higher, but not significantly, from the toxaphene than from the chlordane- 

 DDT mixtures. Aphid, Aphis gossypii Glov. , infestations approaching the dam- 

 age point developed after the applications of chlordane- DDT dust mixtures in 



1 of the large-scale experiments. In 1 experiment aldrin- DDT applied as a spray 

 gave better boll weevil control and higher increases in yield than toxaphene-DDT 

 or chlordane-DDT applied as sprays. A toxaphene dust gave somewhat better 

 boll weevil control than a toxaphene-DDT spray, but there was a slight difference 

 in favor of the spray in control of the bollworm. 



1950 - Parencia, C. R., Jr., and K. P. Ewing. Comparison of early-season, late-season, 

 and a combination of early- season plus late- season insecticide applications for 

 cotton insect control. J. Econ. Ent. 43(5):596-598. 



Field-plot experiments were conducted in the Waco area during 1949 to 

 compare early- season, late-season, and early- plus late-season insecticide 

 applications for cotton insect control. 



The cotton which received early-season treatment set and matured its crop 



2 to 3 weeks earlier than cotton which received no early treatment. Control of 

 thrips (several species), overwintered weevils, Anthonomus grandis Boh., and 

 other early- season insects was approximately the same when a dust and a spray 

 were compared. Plots receiving an average of 3.5 early- season applications 

 produced a gain of 317 pounds of seed cotton per acre over plots receiving no 

 treatment; plots receiving an average of 5 late- season applications produced a 

 gain of 379 pounds; and plots receiving an average of 7.3 early plus late applica- 

 tions produced a gain of 460 pounds. 



The results of these experiments indicate that early-season insecticide ap- 

 plications may be more economical than late- season applications in the Central 

 Texas area, even though entire farms or communities are not treated. 



Late- season applications, especially on highly productive land, are likely to 

 be needed after early- season applications on areas smaller than entire farms or 

 communities. 



1950 - Scales, A. L., E. E. Ivy, and C. F. Rainwater. Preliminary evaluation of two 



nitroparaffin insecticides against four cotton insects. J. Econ. Ent. 43(4):560- 561 . 



At the rates tested against the boll weevil, neither compound CS-645A nor 

 CS-674A, corresponding to the chemicals [2-nitro- 1,1 -bis (p-chlorophenyl) 

 propane] and [2-nitro- 1, 1-bis (p-chlorophenyl) butane], respectively, compared 

 favorably with 20 percent toxaphene. 



53 



