Potential of dip treatments to disinfest cuttings of the invasive Thrips parvispinus (Thysanoptera: Thripidae)

Abstract

Thrips parvispinus (Karny) (Thysanoptera: Thripidae), an invasive thrips species, poses a significant threat to global agriculture due to its polyphagous nature and rapid spread. Its recent arrival in the continental United States raises concerns about potential impacts on ornamental and vegetable crops. Dip treatments might serve as a phytosanitary practice for growers to start with plants free of visible pests. This study aimed to assess the efficacy of dip treatments using 4 biorational and microbial insecticides (mineral oil and Beauveria bassiana-based) in controlling T. parvispinus on bean seedlings. Following gentle agitation of cuttings, artificially infested with 10 second-instar (L2) larvae, for 15 s in each solution, thrips infestation was evaluated at 1, and 24 h postdipping, scoring the numbers of dislodged and dead larvae. Additionally, we tested whether dipping could cause phytotoxicity on bean (Phaseolus vulgaris L.), gardenia (Gardenia jasminoides Ellis), and mandevilla (Mandevilla splendens (Hook.f.) Woodson) cuttings during a 7-day period. Our results demonstrated that dip treatments effectively dislodged and killed T. parvispinus L2 larvae from infested cuttings, with BotaniGard-ES and Suffoil-X exhibiting the highest efficacy and a dislodgment rate of 80%-100%. BotaniGard-ES was the only product causing phytotoxicity on bean seedlings, but not on mandevilla and gardenia. Overall, we demonstrated that dip treatment using biorational insecticides is an additional tool that can be incorporated in the integrated pest management of T. parvispinus. These results hold implications for the broader application in the management of thrips across various plants propagated from cuttings.

Keywords: bean; gardenia; insect pests; mandevilla; propagative material; regulated pest.