Northern Corn Rootworm Larval Control By Experimental Insecticides in Ohio, 1976

Field corn, variety Pioneer 3773, was planted at New Pittsburg (Wayne County), Ohio on April 30'76. Four experimental and 2 recommended soil insecticides were applied in the furrow or in a 7-inch band in front of the presswheel at time of planting. Randomized split plots, with placement (band or furrow) assigned to the whole plots and insecticide to the split plots, or randomized complete blocks with four replicates were used. Plots were 2 rows wide (38 in spacing), 40 ft long, with two border rows between replicates that were contiguous and 25 ft alleyways between replicates that were not. Because of variation in larval density, the number of rows in a replication was less than twenty. Application was made with electric Gandy insecticide boxes mounted over each planter presswheel at a constant 3 mph tractor ground speed. Soil type was silt loam. Rainfall for May was 1/2 normal with June normal and July slightly below normal. Soil temperature (4 in depth) at planting was ca 11°C. Larval damage was assessed on August 3rd, by digging and washing 24 root systems from each treatment (6 roots/plot × 4 reps) and evaluating each root system on the standard 1-6 rating scale where 1= little or no damage and 6 = three or more nodes of roots destroyed.