Corn Earworm and European Corn Borer Control in Sweet Corn, 1977

Sweet corn was planted Jun 2477 (app. 1000 HU 50) so that expected European corn borer and corn earworm moth flights would coincide with ear formation. Four randomized complete blocks each 80 ft long x 168 rows were used. Each block contained 20 chemical treatments and 5 stratified untreated checks. Each replicate consisted of four rows of corn with two border rows between treatments. Ten border rows were left on the edge of each block. Insecticides were applied with a modified commercial Hagie Hiboy equipped to spray each 4-row plots with six D2/23 Tee Jet tips per row at 30 gpa. Applications were initiated at 80% silk on Aug 17 and retreatments were made on Aug 21, 24, 27, and 31. At harvest, 14 days after the last application, 25 ears from the middle two rows of each replicate were examined for “early” or “late” instar larvae of the European corn borer and corn earworm. The number of “early” European corn borer or corn earworms is an indicator of residual control after the last application. Damage to each ear was assessed as “none (clean)”, “tip only”, and “tip and side”. Third generation European corn borers heavily infested the area after the last treatment but did little ear damage and were not considered in the damage assessment. Earworm pressure was intense and was the main cause of economic damage in this test.