Control of Curculio caryae (Coleoptera: Curculionidae) with Reduced Rates of a Microbial Biopesticide

The pecan weevil, Curculio caryae (Horn), is a major pest of pecans (Harris 1985, Pp. 51–58. In Pecan Weevil: Research Perspective, W. W. Neel (ed.), Quail Ridge Press, Brandon, MS). These insects have a 2or 3-yr life cycle with most adult weevils emerging from soil beneath trees from late July through September to feed on and oviposit in the developing fruit (Harris 1985). Fourth instars drop to the ground and burrow to a depth of 8–25 cm, form a soil cell, and overwinter. During the following autumn, approximately 90% of larvae pupate and spend the next 9 mo in the soil as adults (Harris 1985). The remaining population (about 10%) spends approximately 2 yr in the soil as larvae and emerges as adults in the third year. Currently, control recommendations for C. caryae primarily consist of canopy applications of chemical insecticides (e.g., carbaryl and certain pyrethroids) to suppress adults (Acebes et al. 2021, Pg. 5, In Wells (ed.), Commercial Pecan Spray Guide. Univ. Georgia-Extension Bull. 841). Although these chemical insecticide applications are effective in controlling C. caryae in conventionally managed orchards, there is a lack of knowledge regarding C. caryae management in organic pecan systems. Additionally, due to problems associated with aphid and mite resurgence that often result from chemical insecticide applications that target C. caryae (Dutcher and Payne 1985, Pp. 39–50 In Pecan Weevil: Research Perspective, W. W. Neel (ed.), Quail Ridge Press, Brandon, MS), as well as other environmental and regulatory issues, research on developing alternative control strategies in both organic and conventional systems is necessary. In prior research, we discovered that that the microbial insecticide GrandevoT (based on Chromobacterium subtsugae Martin, Gundersen-Rindal, Blackburn & Buyer), applied in pecan orchards at 3.36 kg per ha, can control C. caryae at similar