Resistance Monitoring of Chilo suppressalis (Lepidoptera: Crambidae) to Chlorantraniliprole in Five Field Populations from Hunan China 2013–20201

Chlorantraniliprole, a new anthranilic diamide insecticide, has been commercialized in China since 2008 for controlling several lepidopterans, including rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae). Chemical control of this pest has become difficult because of its development of resistance to many conventional insecticides. To facilitate chlorantraniliprole resistance monitoring, seedling dip bioassays were conducted in 2013 and 2020 to assess the resistance of 5 field populations of C. suppressalis from Hunan provinces in China. The median lethal toxicity (LC50) of chlorantraniliprole against 3rd–4th instar larvae of field populations ranged from 14.799 to 103.587 mg active ingredient (a.i.)/L. The resistance of C. suppressalis to chlorantraniliprole is increasingly serious in most of the regions in Hunan. The levels of resistance of C. suppressalis to chlorantraniliprole ranged from 11.1-fold to 74.4-fold compared with a susceptible population, respectively. During the 8 years, the resistance level of C. suppressalis to chlorantraniliprole at five monitoring points showed a fluctuating upward trend. The resistance of C. suppressalis to chlorantraniliprole in Hengyang is highest in every year. These data are useful in future monitoring program for detecting any changes in resistance as a result of use of the insecticide.