Potato Leafhopper and Seedcorn Maggot Efficacy Trials, 1979

Twenty-four soybean plots (var. Elf) were established near Ames, Iowa. Each measured 40 ft by 4 rows (30-in centers) and was bordered by 2 rows. Five treatments (Table 1) and a check were arranged in a randomized completeblock design, with 4 blocks. Granular insecticides were applied in-furrow at planting on May 23 with a 2-row John Deere 71 flex planter. Plants emerged on May 31. Stand counts were taken on June 14. Each plot was examined for phytotoxic symptoms and assigned a value from 0 (no symptoms) to 5 (severe curling and discoloration of leaves and growing tip). Seedcorn maggot damage was evaluated by counting the number of plants with snakeheads (maggot-eaten growing tip) and/or cotyledonary scarring in 4 1-m row sections/plot. Plots were sampled (10-sq ft/plot) for potato leafhopper nymphs and adults with a D-Vac vacuum insect net (1-sq ft sampling cone). Post-emergence samples (20, 30, 45, and 60 days post-emergence) were taken on July 19 (3-trifoliate stage), June 29 (5-trifoliate stage), July 13 (mid-bloom stage) and July 27 (beginning pod-fill stage), respectively. D-Vac sampling was supplemented with shake sampling, 2 samples of 2 adjacent 1 row-ft/plot, for nymphs at 45 and 60 days post-emergence. Total rainfall for June and July was 2.9 and 4.5 in, respectively. Plots were harvested Oct 25 and bean weight/10 row-ft determined.