Field Corn, Northern Corn Rootworm Larval Suppression, 1977

Abstract

Abstract Field corn was planted near Wooster (Wayne County) Ohio on May 9 and 26. Four recommended soil insecticides were applied at time of planting 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. A split split plot design with 4 replicates was used (main plot = placement, sub plot = planting date, sub sub plot = insecticide). Plots were 2 rows wide (38 in spacing), 40 ft long, with 4 buffer rows between replicates that were contiguous and 20 ft alleyways between those that were not. The field had been in com for 7 years. Previous insecticide use consisted of 1 lb/acre Furadan in 1976 only. Soil type was silt loam, pH 6.64, organic matter 2.1%. Rainfall during May was less than half normal, but abundant rain during the following months brought the season’s total to above average. Soil temperature (4 in. depth) was 13°C on May 10, and 22°C on May 26. Larval damage was assessed on August 8, by digging and washing 24 root systems from each treatment (6/plot x 4 rep) and evaluating each root system on the standard Iowa 1-6 rating scale where 1 = little or no damage and 6 = three or more nodes of roots destroyed.