Field Corn, Corn Rootworm Larval Control, 1986

Abstract

Abstract Corn rootworm planting-time and first-cultivation soil insecticide trials wt conducted at Mead, Neb. The test plots were in trap crop during 1985 and had been in a trap crop (no insecticide)/insecticide test plot annual rotation at least 8 yr. The soil type was a silty clay loam. The experimental design was a randomized complete block with 4 replications. Each replication consist of single-row treatments that were 35 ft long and 30 inches apart. Planting-time application equipment consisted of modified V-belt seeders mounted oi model 80 John Deere® flex planter. Preweighed amounts of insecticide granules were placed on the V-belts and directed into the seed furrow or band over the row in front of the press wheel. Noble® metering units mounted on a hand-powered bicycle applicator were used to apply granular insectici formulations at first cultivation. Liquid insecticide formulations were applied with a small plot sprayer pressurized with C02 . A Tee Jet® 8004 nozzle v used at 30 psi to deliver 16.4 gal/acre. Granules were banded directly over the plant whorl, and liquids were sprayed in a 7- to 10-inch band directed at t plant base. All treatments were immediately incorporated by a cultivator. Corn was planted on 7 May, and first-cultivation treatments were applied 6 Ji Soil moisture conditions were excellent when insecticides were applied. Initial corn rootworm egg hatch was detected on 3 Jun. Stand counts were taken 2 Jun and 15 Oct. Plant evaluations were made on 2 Jun in the planting-time test to determine whether any insecticide treatments adversely affected cc development. Plants were considered abnormal if they were stunted or exhibited deformed growth patterns (i.e., buggy whipping). Rootworm feeding dama - was evaluated (8 Jul, planting-time test; 17 Jul, cultivation test) by digging 5 roots from each treatment row and rating the damage by means of the Iowa 6 scale (1, no feeding to 6, 3 or more nodes of roots completely destroyed). Lodging counts were taken in October. A plant was recorded as lodged if t angle between the soil surface and the plant stem was ≤67.5 degrees. Data were subjected to an analysis of variance, and an LSD test was used for me separation where significant differences occurred.