Efficacy of Conventional and Biorational Insecticides against the Invasive Pest Thrips parvispinus (Thysanoptera: Thripidae) under Containment Conditions

Abstract

In 2020, the invasive Thrips parvispinus (Karny) was first detected in Florida, United States. In response to the implemented regulatory restrictions, we conducted laboratory experiments under containment conditions. Thrips larvae and adults were exposed to 32 products (conventional and biorational insecticides) either directly or indirectly. Direct exposure was performed using a Spray Potter Tower, while indirect exposure was conducted by evaluating residue toxicity against the thrips. Water served as a control. We assessed mortality and leaf-feeding damage 48 h post-treatment. Among the conventional insecticides, chlorfenapyr, sulfoxaflor-spinetoram, and spinosad caused high mortality across all stages in both direct and residue toxicity assays. Pyridalyl, acetamiprid, tolfenpyrad, cyclaniliprole-flonicamid, acephate, novaluron, abamectin, cyantraniliprole, imidacloprid, cyclaniliprole, spirotetramat, and carbaryl displayed moderate toxicity, affecting at least two stages in either exposure route. Additionally, chlorfenapyr, spinosad, sulfoxaflor-spinetoram, pyridalyl, acetamiprid, cyclaniliprole, cyclaniliprole-flonicamid, abamectin, and acephate inhibited larvae and adult's leaf-feeding damage in both direct and residue toxicity assays. Regarding biorational insecticides, mineral oil (3%) and sesame oil caused the highest mortality and lowest leaf-feeding damage. Greenhouse evaluations of spinosad, chlorfenapyr, sulfoxaflor-spinetoram, and pyridalyl are recommended. Also, a rotation program incorporating these products, while considering different modes of action, is advised for ornamental growers to avoid resistance and to comply with regulations.

Keywords: acute toxicity; chemical control; feeding damage; integrated pest management; mortality; residue toxicity.

Figure 1

Mortality caused by conventional and biorational insecticides 48 h after treating Thrips parvispinus. The figure illustrates the percentage of dead larvae (L1; L2) and adult thrips in both direct (squares) and residue toxicity assays (circles). Blue color indicates that the observed mortality was significantly higher than the control (p ≤ 0.05; GLMM), while red indicates non-significant differences.

Figure 2

Percent of leaf-feeding damage caused by Thrips parvispinus 48 h after being treated with conventional and biorational insecticides. The figure illustrates the percentage of bean leaf-feeding damaged area caused by larvae (L1; L2) and adult thrips in both direct (squares) and residue toxicity assays (circles). Blue color indicates that the observed leaf-feeding damage was significantly higher than the control (p ≤ 0.05; GLMM), while red indicates non-significant differences.