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

Abstract

Invasive tephritid fruit flies collectively pose a significant economic challenge to agricultural pest management globally. 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 peptide‐based biorational insecticide with a unique mode of action, containing the active ingredient, GS‐omega/kappa‐Hxtx‐Hv1a (GS‐Hv1a), against four of tephritid species, oriental fruit fly (Bactrocera dorsalis), melon fly (Zeugodacus cucurbitae), Mediterranean fruit fly (Ceratitis capitata, ‘Medfly’), and Malaysian fruit fly (Bactrocera latrifrons). This assessment aimed to determine whether GS‐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 GS‐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 survival decreased following oral ingestion as well, the amount required to achieve this was greater than the concentration used in the topical bioassay. We observed that survival continued to decline up to 72 h after exposure, indicating a delayed effect similar to other reduced‐risk insecticidal products such as fipronil. For this reason, GS‐Hv1a may be useful as a horizontal transfer tool in conjunction with C. capitata male pheromone lures.