Management of the Greenbug on Grain Sorghum. 2. Testing Seed and Soil Treatments for Greenbug and Corn Leaf Aphid Control12

Abstract

Monocrotophos treatments to grain sorghum seed were not effective against Schizaphis graminum (Rondani). Seed-furrow treatments of aldicarb were effective when placed in the seed furrow in direct contact with seed at planting but were not effective when banded 1/2 inch above seed. Seed-furrow treatments of granular or liquid disulfoton gave season-long control of pest and about, six weeks' control of the corn leaf aphid, Rhopalosiphum maidis (Fitch). Sidedress treatments of granular or liquid disulfoton also were effective against green bugs, but a period of 2-:3 weeks after application was required for best control. Combination treatments of disulfoton, seed-furrow + sidedress application, or seed-furrow + foliar spray application, were highly effective against the green bug and provided season-long control. Phorate granules applied in direct contact with seed in the seed furrow at planting provided several weeks of residual control of both green bugs and corn leaf aphids but caused a significant reduction in plant stand. Combination seed-furrow + foliar spray treatments of phorate gave season-long green bug control. Some of the insecticidal treatments caused a significants reduetion in populations of insect and spider predators and hymenopterous parasites. some insecticidal treatments increased grain sorghum seed yields significantly over the nontreated checks, but these in creases apparently over the nontreated checks, but these increases apparently were not entirely due to green-bug or corn leaf aphid control. Aphid damage to the aerial portions of the plants was not significantly greater in the nontreated checks than in the insecticidal-treated grain sorghum. There was no evidence of increased test weight or seed size of harvested grain resulting from insecticidal treatment, and the percent of lodged sorghum plants at harvest was not related to earlier green bug infestations