Field Corn, Northern Corn Rootworm Larval Suppression, 1978

Abstract Soil insecticides to suppress larvae of the northern corn rootworm were evaluated at 2 locations in Ohio. Pioneer 3780 was planted in 30 inch rows in continuous corn acreage on June 3 in a 4.5 acre plot near Wooster (Wayne County) and April 29 in a 0.34 acre plot at the Western Branch Research Center (Clark County). Soil type was silt loam at Wooster and silfy clay loam (Brookston soil) at the Western Branch site. Planting at Wooster was delayed be-cause of abundant rain. Insecticides were applied at planting time in the furrow or in a 7-inch band in front of the presswheel using electric Gandy insecticide boxes mounted over each planter presswheel. Applications were made at 3 mph tractor ground speed. Experi-ments were arranged in randomized complete block designs with 4 replicates/treatment. Plots were 2 rows x 40 ft long. Furadan (1.2 oz AI/1000 ft row) was applied 1974-77 in the Western Branch field; a soil insecticide was not used in 1977 at Wooster. Larval damage was assessed August 1 (Western Branch plots) and August 2-4 (Wooster plots) by digging and washing 24 root systems from each treatment (6/plot x 4 reps) and evaluating each root system with the standard Iowa 1-6 rating scale, where 1 = little or no damage and 6 = three or more nodes of roots destroyed.