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Soil insecticides to suppress larvae of the northern corn rootworm were evaluated at 3 locations in Ohio. Plots with 30-inch rows were established in continuous corn acreage on May 2 at the Western Branch Research Center (Clark County), and May 7 in a grower's field near Wooster (Wayne County), and on May 10 at the Ohio Agricultural Research and Development Center (Wayne County). Soil type and characteristics were: silty clay loam, pH 5.9, organic matter 2.9% (Western Branch); silt loam, pH 7.0, organic matter 2% (Wooster site); Wooster loam, pH 6.6, organic matter 5% (OARDC site). Soil insecticides were applied at planting 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. Experiments were arranged in randomized complete block designs with 4 replicates/treatment. Plots were 2 rows × 40 ft long. Furadan (1.2 oz ai/l,000 ft row) was applied 1976-78 in the Western Branch field and 1974-78 in the Wooster field; a soil insecticide was not used in the OARDC field prior to 1979. Larval damage was assessed July 9-10 (Western Branch plots), July 31 (Wooster plots) and August 1 (OARDC plots) by digging and washing 16 root systems from each treatment (4/plot × 4 reps) and evaluating each root system with the standard Iowa 1-6 rating scale (1 = little or no damage, 6 = 3 or more root nodes destroyed). |
