Using Agrisure Corn Hybrids in Combination with Insecticides for Rootworm Larval Suppression, 2015

Corn rootworm management efficacy trials were conducted to evaluate transgenic insect-resistant hybrids and granular insecticide combination treatments near Bryant and Cavour in South Dakota. The study was arranged in an RCBD with four ∼50 foot long replications. Four row treatments were established using rows that were spaced 30 inches apart at planting-time. In-furrow liquid insecticide treatments were placed directly into the open seed furrow between double-disk openers. The Agrisure3122- E-Z refuge and Agrisure Avicta (N29T3122), Agrisure Viptera (N29T-3111), and Agrisure CB (N92T43-3220) corn hybrids seeds were all treated with CruiserMaxx at 0.25 mg ( AI )/seed for secondary pest control. This seed was planted at ∼ 31,000 kernels per acre. Six roots per plot were dug randomly from the two outer rows, washed and rated using the Oleson 0–3 root injury rating scale. Yield assessments were taken from the center two rows. Yield and root rating data were analyzed by using SAS version 9.2 PROC MIXED/PDIFF option with Saxton’s lettering macro.

Root rating means from Agrisure CB that offered no NCR/WCR protection was 0.43, and 1.38 at Bryant and Cavour. Therefore rootworm pressures could be categorized as low to moderately high based on ∼0.25 economic injury level (EIL). Rootworm feeding pressure was ∼0.10 of a node greater at Bryant and 2/3 greater root injury at Cavour than in the previous season. In 2015, none of the rootworm toxin expressing hybrids allowed root feeding from rootworm larvae to exceed the ∼0.25 EIL. Insecticides are still very effective as a tool to reduce the feeding injury to corn roots.

Author notes