Field Corn, Corn Rootworm Larval Control, 1983

Abstract

Abstract Two insecticide evaluation studies were conducted for rootworm control. The first test was conducted at the Pa. Agric. Exp. St. Farm at Rock Springs, Centre County. Northern corn rootworm is the species present at this location. The test field had been continuous corn with no insecticide treatments for 3 years. Corn was planted on 19 May, using a 6-row John Deere Max-Emerge no-till planter with 30-in. row spacing. Insecticides were applied to 15 by 90-ft plots in a randomized complete block design with untreated checks in five replications. Eight insecticides were compared at 15 material-rate combinations, using either an in-furrow or banded method of application. All granular treatments were applied at planting, 19 May. The banded treatments were applied in 7-in. bands over the row. Reduction sleeves were used to contain Lorsban to a 5-in. band. Stand germination counts were taken on 21 June. On 21 and 22 June, the plots were thinned to 114 plants per 90 ft of row or a population of 22,000 per acre. On 5 Aug., the five plants from each replication were evaluated for root damage ratings based on the Iowa 1 to 6 system. Yield was determined on 8 Nov. by mechanically harvesting two middle rows of each plot for shelled corn. The second test was conducted at the Yahner farm, Cambria County, Pa. Both northern and western corn rootworm were present in the field. Western corn rootworm was first detected in this county in 1982. The tilled test field had been continuous corn for more than 4 years. Corn was planted on 8 June, using a four-row John Deere no-till planter with 38-in. row spacing. Insecticides were applied to 7.5 by 126 ft plots in a randomized design with untreated checks in four replications. Four insecticides were compared at 1 lb(AI)/acre banded 7-in. over the row. All granular treatments were applied at planting. Plants were thinned to 125 plants per 100 ft row on 22 June. On 11 Aug., the five plants from each replication were evaluated for root damage ratings based on the Iowa 1 to 6 system. Yield was not measured due to drought.