Tests of Insecticides, Including DDT, Against the Corn Earworm and the Fall Armyworm in Corn

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Abstract
Tests for control in sweet or dent corn ears of Heliothis armigera and Laphygma frugiperda were carried out in Illinois, Mississippi, and Arkansas. None of the 7 insecticides tested, including DDT, were effective as in dusts. Of the 16 insecticides or insecticide mixtures used as sprays, DDT, benzene hexa-chloride, chlordane, and TDE gave the best control. Benzene hexachloride made the corn inedible and chlordane left a pungent odor on the kernels at the strength used. TDE appeared to be less effective than DDT. As little as 0.25 g. technical DDT in 100 ml. white mineral oil (120 to 125 sec. Saybolt viscosity) applied by injection at 0.33 ml. per ear gave excellent control of both insects. One g. technical DDT in 100 ml. of white mineral oil (85 to 95 sec.) applied as a spray at 1 ml. per ear also gave very good control. The insecticide in undiluted oil should not be applied until the silks have been fertilized. An emulsion containing 1 g. of DDT (50-90% wettable powder), 0.5 ml. of emulsifier, 20 ml. white mineral oil (85 to 95 sec.) to 100 ml. with water applied as a spray at 2 to 3 ml. per ear also gave good to very good control. Approx. 20% oil seems to be necessary to obtain the required penetration of the ears where the spray is applied after the silks are fertilized. Analyses of 20 samples of corn sprayed with DDT in oil solution or in emulsions showed that none had more than 1.52 ppm. of DDT on the kernels or more than 2.7 ppm. on the cobs. The husks and silks had from 47.9 to 301 ppm. depending on the strength and rate of application of the spray. Injection and spraying the ears with oil solutions or emulsions containing DDT did not affect germination, neither did injection into the ears of dichloroethyl ether dissolved in mineral oil.

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