Corn Earworm and European Corn Borer Control Programs in Sweet Corn, 1978

Sweet corn was planted Jun 20’78 (app. 1000 HU 50) so that ear formation coincided with expected European corn borer and corn earworm flight activity. Twenty chemical treatments and 4 stratified untreated checks were replicated in four randomized complete blocks 80 ft x 164 rows. Each treatment consisted of four rows with two border rows between treatments. Ten border rows were left on the edge of each block. All materials were applied with a modified Hagie Hiboy (25 gpa, 3 mph, and 40 psi) with six D2/23 Tee Jet tips per row. Because of the severe European corn borer pressure, treatments were initiated at row tassel and continued at scheduled intervals adjusted to light trap catches. At harvest, 13 days after the last treatment, 25 ears from the middle two rows of each replicate were examined for damage to each ear as “none” (clean), “tip” (kernels eaten), “side”, or “tip and side”. Each ear was assessed for the number of European corn borers and corn earworms in the early, mid, or late instar stage. Treatments were applied during the heaviest European corn borer flight in 18 years based on light trap records. Corn earworm pressure was also intense, with the main infestation occurring after the Aug 24 application. The untreated checks were 100% infested with 94% damaged ears. There was an average of 2.3 European corn borers and 0.8 corn earworms per ear.