Monitoring the development of resistance in diamondback moth (DBM) Plutella xylostella (L.) to diamide group of insecticides

The field resistance level in Plutella xylostella to diamide insecticides, viz., flubendiamide 20 WG at 50 g a.i. ha^-1, chlorantraniliprole 18.5 SC at 10 g a.i. ha^-1 and cyantraniprole 10.26 OD at 600 g a.i. ha^-1 was assayed at four locations in Tamil Nadu, India viz., Coimbatore, Krishnagiri, Oddanchatram and Kotagiri. Susceptibility of these populations varied and exhibited significant resistance towards these insecticides. The highest level of resistance to flubendiamide, chlorantraniliprole and cyantraniprole in terms of resistance ratio (fold increase in LC₅₀ over the susceptible laboratory population) was registered in the P. xylostella population collected from Krishnagiri (9.73), Kotagiri (9.15) and Krishnagiri (5.47), respectively.