Efficacy of ISTs in corn for managing corn rootworm complex

Fei Yang

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, and the northern corn rootworm (NCR), Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae) stand as the primary belowground insect pests of corn in Minnesota, causing substantial yield losses and economic harm. The adoption of genetically engineered corn hybrids, incorporating insecticidal proteins from Bacillus thuringiensis (Bt), has been a pivotal strategy for U.S. corn producers in managing these rootworms. However, reports of corn rootworms developing resistance to Bt proteins have become prevalent in Bt corn fields, necessitating the exploration of alternative practices. Insecticidal seed treatments (IST) employing neonicotinoid insecticides like clothianidin and thiamethoxam have been proposed for use at higher rates to control rootworms. Nonetheless, a significant knowledge gap exists regarding the comprehensive efficacy and value of higher-rate ISTs for managing the rootworm complex, especially concerning emerging Bt resistance within Minnesota. This study aims to evaluate the effectiveness of elevated IST rates in controlling rootworms in both Bt and non-Bt corn fields. Additionally, it seeks to determine whether combining IST with Bt technology yields additive, synergistic, or neutral effects in managing the rootworm complex
in Minnesota. The findings from this research endeavor not only bridge the current knowledge gap but also establish a basis for employing higher-rate IST in corn as a strategic tool for robust rootworm management.