Comparative efficacy of GS-Hv1a against invasive tropical tephritids

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 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,
“Medfly”), 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
than topical. We observed that mortality continued to decline up to 72
hours after exposure, indicating a delayed effect similar to other
reduced-risk 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.