Corn rootworms (CRW) are among the most destructive pests in corn production across the Corn Belt, causing considerable damage through larval feeding on roots. While crop rotation and Bt technologies are widely adopted management strategies, their effectiveness is increasingly compromised by the pest's evolution of resistance and behavioral adaptability. Chemical insecticides applied at planting to target larvae directly serve as an additional tool for corn rootworm control. In this study, we evaluated the performance of various insecticides, applied in-furrow, for managing corn rootworms by assessing Node Injury Scale (NIS), lodging rates, and grain yields from 2020 to 2024. We found that Mode of Action (MOA) 3A insecticides (sodium channel modulators), such as Force Evo (tefluthrin) and Capture LFR (bifenthrin), did not provide substantial efficacy in reducing NIS and lodging rates. In contrast, MOA 1B+3A insecticides (acetylcholinesterase (AChE) inhibitors + sodium channel modulators), such as INDEX (chlorethoxyfos + bifenthrin) and AZTEC HC (tebupirimphos + cyfluthrin), significantly reduced CRW larval damage, particularly under high pest pressure in 2020, 2021 and 2023. Differences in insecticide concentrations did not significantly impact larval control efficacy. Additionally, seasonal rainfall during larval hatching and variation in cumulative corn growing degree days (GDD) strongly influenced the root injury and lodging outcomes. Lower GDD likely limits root regeneration, increasing lodging risk under CRW pressure. These findings demonstrate the values of in-furrow insecticides in managing corn rootworms, particularly under high pest pressure and provide valuable insights for developing integrated pest management strategies to sustain effective CRW larval control and improve crop productivity.

Certain soil insects, such as the root-damaging larvae of the maize pest Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), are increasingly difficult to control because of recent bans of some insecticides. An alternative and safer approach may be the development of biopesticides based on entomotoxic defense proteins of higher fungi. Many of these potentially interesting proteins are protease inhibitors, and some have been shown to adversely affect insects. We examined the effects of the cysteine protease inhibitors macrocypin 1, 3, and 4 from Macrolepiota procera, clitocypin from Clitocybe nebularis, and cocaprin 1 and the serine protease inhibitor cospin 1 from Coprinopsis cinerea on D. v. virgifera. We confirmed the inhibition by mycocypins of the cysteine catalytic-type proteolytic activities in gut extracts of larvae and adults. The inhibition of pGlu-Phe-Leu-hydrolyzing activity was stronger than that of Z-Phe-Arg-hydrolyzing activity. Mycocypins and cospin resisted long-term proteolytic digestion, whereas cocaprin 1 was digested. Bioassays with overlaid artificial diet revealed no effects of proteins on neonatal mortality or stunting, and no effects on adult mortality. Immersion of eggs in protein solutions had little effect on egg hatching or mortality of hatching neonates. Microscopic analysis of the peritrophic matrix and apical surface of the midguts revealed the similarity between larvae of D. v. virgifera and the chrysomelid Leptinotarsa decemlineata, which are sensitive to these inhibitors. The resistance of D. v. virgifera to fungal protease inhibitors is likely due to effective adaptation of digestive enzyme expression to dietary protease inhibitors. We continue to study unique protein complexes of higher fungi for the development of new approaches to pest control.