Sensitivity monitoring of Bemisia tabaci to two tetramic acid insecticides and baseline susceptibility to spiropidion in China

Abstract

The sweet potato whitefly, Bemisia tabaci (Gennadius) is one of the most devastating pests, inflicting severe damage on a wide range of crops. The tetramic acid insecticides, spirotetramat and spiropidion, act as inhibitors of lipid biosynthesis by targeting acetyl-coenzyme A carboxylase (ACCase), disrupting fatty acid biosynthesis and energy metabolism. In the present study, a total of 47 field populations were collected across China in 2021 and 2022, and their susceptibilities to spirotetramat and spiropidion were determined in the laboratory. The results showed that in contrast to their toxicities against nymphs, spirotetramat and spiropidion exhibited minimal toxicity against B. tabaci adults. B. tabaci nymphs from field populations exhibited susceptibility or low resistance to spirotetramat, with LC50 values ranging from 2.85 to 13.58 mg L−1 and resistance ratio (RR) from 1.7 to 8.2. There was a variation in the sensitivity of B. tabaci field populations towards spiropidion, with LC50 values ranging from 13.12 to 120.13 mg L−1 and RR from 3.5 to 23.4. The baseline susceptibility of B. tabaci nymphs to spiropidion was determined to be 24.06 mg L⁻1, corresponding to the median lethal concentration (LC50) calculated from 43 field populations. Cross-resistance was observed between spirotetramat and spiropidion, as well as between cyantraniliprole and tetramic acid insecticides. However, no significant cross-resistance was found between neonicotinoids and tetramic acid insecticides. Collectively, these findings improve our knowledge on the toxicity of tetramic acid insecticides to B. tabaci populations in China and provide valuable information for their scientific application in the field.