Evaluation of Soil Insecticides Against Larval Corn Rootworms, Clay Center, Ne, 1995

Abstract

Abstract Planting and first-cultivation time soil insecticide trials were conducted at Clay Center, NE, to evaluate their performance against larval corn rootworms. The local population consisted of >95% WCR and <5% NCR. All plots were in trap crop (insecticide free) during 1994. In 1993, multiclass soil insecticide trials were conducted, with all plots in trap crop (insecticide free) in 1992 and Lorsban 15G at 1.21b (AI)/acre was applied to all plots in 1991 and 1990. The experimental design was a RCB with 4 replicates. Each treatment replicate consisted of a single row 30 ft long with a 30-inch row spacing. Soil type was a Butler/Crete silt loam. All plots were planted on 16 May. Soil temperature at 4 inches was 64°F. Insecticides were applied using 10 inch Almaco smooth belt cones mounted in place of insecticide boxes on a 2-row John Deere 7100 plateless planter. Preweighed amounts of insecticide granules were distributed uniformly around the belt cone by a divider funnel and either directed into the open seed furrow (IF) or a 7-inch band in front of the press wheel and over the open seed furrow and incorporated with a drag rake (TB). Stand counts were taken on 7 Jun. Initial corn rootworm egg hatch was detected on 14 Jun. First-cultivation time treatments were applied on 21 Jun. Soil temperature at 4 inches was 79°F. A mason jar with holes in the lid was used to apply granular insecticides at first-cultivation. Granules were applied basally by shaking the mason jar and immediately incorporated by cultivation (GC). A CO2 pressurized backpack sprayer set at 40 psi was used to apply liquid insecticides (total volume of solution applied = 1,100 ml/ plot) at first-cultivation. The liquid insecticides were applied to the base of plants and immediately incorporated by cultivation (LC). Larval feeding damage was evaluated on 20–21 Jul. Five plants were dug from each treatment replicate and rated using the Iowa 1°6 scale (1, no feeding, to 6, 3 or more nodes of roots completely destroyed). Data were analyzed by ANOVA for RCB with mean separation using DMRT.