Evaluating the efficacy of insecticidal seed treatments (IST) for managing soil insect pests in Bt and non-Bt corn

Insecticidal seed treatments (IST) aiming to control early season soil insect pests have been adopted globally in a variety of crops. However, concerns have emerged regarding the negative effects of IST on pollinators. Currently, nearly 100% of corn seeds are treated with neonicotinoid insecticides, to ensure protection against primary and secondary pest threats, including corn rootworms. The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, and the northern corn rootworm (NCR), Diabrotica barberi Smith & Lawrence are the two major belowground insect pests of corn and have caused substantial yield losses and economic damage in the U.S. Corn Belt, with an estimation of over $1 billion annually in yield loss and cost of control. Currently, there is a notable gap in our comprehensive understanding of the efficacy and value of IST for controlling the rootworm complex in Minnesota. In this study, we investigated the efficacy of IST at variable rates for control of rootworms in both Bt and non-Bt corn fields, and discussed whether there are additive, synergistic, or neutral effects when IST is combined with Bt and/or RNAi technologies for managing the rootworm complex. The data generated from this study will provide a foundation for the effectiveness of IST in rootworm management within the state, but also addresses the necessity of using IST in all corn seeds to minimize the exposure of pollinators to neonicotinoids.