Control of Curculio caryae (Coleoptera: Curculionidae) with reduced rates of a microbial biopesticide

Authors: Shapiro Ilan, David; WELLS, LENNY - University Of Georgia

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2021
Publication Date: 3/30/2022
Citation: Shapiro Ilan, D.I., Wells, L. 2022. Control of Curculio caryae (Coleoptera: Curculionidae) with reduced rates of a microbial biopesticide. Journal of Entomological Science. vol 57: 310-313. https://doi.org/10.18474/JES21-65.
DOI: https://doi.org/10.18474/JES21-65

Interpretive Summary: The pecan weevil is a major pest of pecans. Currently, control recommendations for pecan weevil primarily consist of canopy applications of chemical insecticides to suppress adults. Due to environmental and regulatory concerns, alternative methods of control are needed. In prior research, the microbial biopesticide, Grandevo (based on a naturally occurring bacterium) applied at 3.36 kg per ha, controlled pecan weevil at similar levels compared with recommended chemical insecticides. Grandevo, like other biopesticides is deemed to be environmentally-friendly and safe to non-target organisms. However, the cost of 3.36 kg per ha Grandevo is cost prohibitive to most growers. Therefore, the objective of our study was to determine the ability of Grandevo to control pecan weevil under field conditions when applied a lower rate. Experiments were conducted over two consecutive years (2019 and 2020) in pecan orchards in Byron, Georgia, USA, and included applications of Grandevo at 2.24 kg per ha and in 2020 a liquid formulation at 1.9 liters per ha (67% of the rate used previously). In both years of the experiment, the Grandevo treatments reduced pecan weevil damage by approximately 93% compared to damage in the non-treated control. Hence relative to prior research indicating efficacy with 3.36 kg per ha the lower rates of Grandevo enhance economic feasibility of the approach. Based on this current research and the recent findings that Grandevo also contributes to population reductions of the black pecan aphid makes Grandevo an attractive option for pecan weevil control.

Technical Abstract: The pecan weevil, Curculio caryae is a major pest of pecans. Currently, control recommendations for C. caryae primarily consist of canopy applications of chemical insecticides (e.g., carbaryl and certain pyrethroids) to suppress adults. Due to environmental and regulatory concerns, alternative methods of control are needed. In prior research, the microbial biopesticide, Grandevo (based on the bacterium Chromobacterium subtsugae) applied at 3.36 kg per ha, controlled C. caryae at similar levels compared with recommended chemical insecticides. However, the cost of 3.36 kg per ha Grandevo is cost prohibitive to most growers. Therefore, the objective of our study was to determine the ability of Grandevo to control C. caryae under field conditions when applied a lower rate. Experiments were conducted over two consecutive years (2019 and 2020) in pecan orchards in Byron, Georgia, USA, and included applications of Grandevo at 2.24 kg per ha and in 2020 a liquid formulation at 1.9 liters per ha (67% of the rate used previously). In both years of the experiment, the Grandevo treatments reduced C. caryae damage by approximately 93% compared to damage in the non-treated control. Hence relative to prior research indicating efficacy with 3.36 kg per ha the lower rates of Grandevo enhance economic feasibility of the approach. Based on this current research and the recent findings that Grandevo also contributes to population reductions of the black pecan aphid, Melanocallis caryaefoliae makes Grandevo an attractive option for C. caryae control.