Comparative efficacy of a spider knottin insecticide, GS-omega/kappa-Hxtx-Hv1a, against four species of invasive tropical tephritids

Authors: Stockton, Dara; Manoukis, Nicholas

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2022
Publication Date: 9/2/2022
Citation: Stockton, D.G., Manoukis, N. 2022. Comparative efficacy of a spider knottin insecticide, GS-omega/kappa-Hxtx-Hv1a, against four species of invasive tropical tephritids. Journal of Applied Entomology. 146(10):1311-1319. https://doi.org/10.1111/jen.13072.
DOI: https://doi.org/10.1111/jen.13072

Interpretive Summary: Insecticide resistance management relies on a combination of rotational applications and novel chemistries to ensure problematic arthropod pests can be reliably controlled. We tested a peptide-based insecticide derived from spider venom, Hv1a, against four species of tephritid fruit flies in Hawaii, two of which have documented spinosad resistance in the field. Due to a novel mode of action, this insecticide has been previously shown to have little to no cross resistance to spinosad making it a good candidate for resistance management. We test the efficacy of Hv1a at 4 concentrations using two routes of delivery, ingestion and topical. We found two interesting effects. First, Hv1a was more effective as a topical product, which is interesting given it is more effective in lepidoptera as an ingested product. Second, we found that different species responded more than others. It was very effective against Mediterranean fruit fly, somewhat effective against the solenaceous fruit fly, but no effective at all against oriental or melon fly. Future work will focus on refining that application of this product against tephritids and testing it in the field.

Technical Abstract: Invasive tephritid fruit flies collectively pose one of the most significant economic challenges to Invasive tephritid fruit flies collectively pose one of the most significant economic challenges to agricultural pest management on a global scale. However, insecticide resistance to a number of previously effective chemical classes, has increased the risk these pests pose as management options become limited. We evaluated the efficacy of a novel class of peptide-based biorational insecticides containing the active ingredient, GS-omega/kappa-Hxtx-Hv1a (Hv1a), against four of tephritid species, oriental fruit fly (Bactrocera dorsalis), melon fly (Zeugodacus cucurbitae), Mediterranean fruit fly (Ceratitis capitata), and Malaysian fruit fly (B. latrifrons). This assessment aimed to determine whether Hv1a has the potential for effective management of tropical tephritids, particularly in regions where insecticide resistance has developed to other products. We conducted two sets of screening assays with different methods of exposure, oral and topical, and compared survival over time in response to increasing concentrations of Hv1a up to 3.86 mg/ml. We found that efficacy was species dependent. Ceratitis capitata was susceptible following topical exposure, while the other species of fruit fly were not. While medfly was susceptible following oral ingestions as well, the dose required to achieve mortality was greater. We did observe that mortality continued to decline up to 72 hours after exposure, indicating a delayed effect similar to other insecticidal products such as fipronil. For this reason, Hv1a may be useful as a horizontal transfer tool in conjunction with C. capitata male pheromone lures.