Selected Insecticides for Corn Earworm Control in Soybean in Virginia, 1993

Efficacy of selected insecticides, with and without adjuvants, was evaluated against CEW in soybean. Hutcheson soybean was planted in 36-inch rows on 29 Jun. Treatments were applied on 18 Aug with water using a CO2-pressurized backpack sprayer calibrated to deliver 14.5 gal formulation per acre at 50 psi through three D2-13 disccore hollow cone spray nozzles per row, 1 over the top of the row and 1 on each side. A RCBD was used with 4 replicates; plots were 4 rows × 40 ft. Treatments were evaluated 3 h before and 1, 5, 8 and 12 DAT by comparing numbers of small (1st and 2nd instars), medium (3rd and 4th instars), large (5th and 6th instars) and total larvae per 3 row ft using a standard beat cloth sampling technique. Yield was determined by combining the center 2 rows of each plot (80 row ft) using a Hege small-plot combine. Data wore analyzed using ANOVA and LSD statistical procedures. A cumulative index (CI) was calculated for each treatment using ∑(Xi+1 - Xi)(Yi + Yi+1)/2], where Xi, and Xi+1, are adjacent sample dates and Yi and Yi+1 are corresponding points of total larval number.