Stage-Specific Susceptibility of Bemisia tabaci MED Eggs and Neonates to Insecticides With Different Modes of Action.

Bemisia tabaci MED is one of the major cryptic species that infests various horticultural crops. Over the years, insecticide resistance has developed in this species due to overuse, yet there is a lack of research on resistance rates among individual insecticides. In this study, the age-specific effects of eight insecticides with different modes of action (acetamiprid [4a], flupyradifuron [4b], spinetoram [5], emamectin benzoate [6], pyrifluquinazon [9b], pyridaben [21a], spiromesifen [23], cyantraniliprole [28]) were tested on B. tabaci eggs of different ages. Insecticides at different doses were applied to eggs on tomato plants via leaf dipping assays, and the mortality until shortly after hatching (1st instar nymphs) was determined. Among the tested compounds, pre-hatch mortality was substantially higher for neonicotinoid compounds (55.8 ± 3.8% and 88.6% ± 4.7% for flupyradifuron and acetamiprid, respectively), hatch failure was greatest for pyridaben (57% ± 6.5%), and 1st instar nymph mortality was higher for emamectin benzoate (74.1% ± 7.9%), pyrifluquinazon (69.9% ± 2.5%), cyantraniliprole (67.9% ± 7.5%), and spinetoram (66.6% ± 3.3%). This suggests that neonicotinoids are highly lethal at the embryonic stage, while pyridaben induced hatch failure, and a variety of other insecticides induced lingering lethality after hatching. Our results provide essential information for understanding each insecticide's developmental and physiological effects and improving the chemical control of B. tabaci.