Corn Earworm Control, 1976

Twelve chemicals and microbial treatments at various rates were applied to corn grown under furrow irrigation on the WSU Research Unit at Royal Slope. Experimental plots were four rows × 50 ft long, with 15-ft alleys within rows and one blank row between adjacent treatments, replicated three times in a randomized complete block design. Four applications were made at 4-day intervals beginning Aug 19'76 (10% silk) using a "Highboy" tractor-mounted, high-clearance experimental plot sprayer delivering 50 gal/acre at 40 psi. Weather conditions were normal during the application periods. Ten days after the last application, 25 ears were randomly selected from the two middle rows of each plot. Each sample was checked for number of ears damaged and number of dead and live earworms present. Extent of damage was rated for length of tunnels from ear tip using an index of 1 to 5 where 1 =• 0.5 cm, 2 = 0.5-1.5 cm, 3 = 1.5-3 cm, 4 = 3-5 cm, and 5 = > 5 cm, and for circumference where 1 = • 2 kernels, 2 = 4 l/4> 3 = 1/4-1/2, 4 = 1/2-3/4, and 5 = 3/4 up to entire circumference of the ear. Materials tested were also evaluated for honey bee toxicity, using an index of 0 to 5 where 0 has no hazard, 1 has short residual hazard, and 5 has long residual hazard.