Horticultural Research Station, Tamil Nadu Agricultural University, Pechiparai - 629 161, Kanyakumari District, India.
Investigations on the dosage and time-mortality response of Bacillus thuringlensis Berliner (Bt) treated larvae of Diamondback moth (DBM), Plutella xylostella (L.) revealed that Bt-treated DBM larvae were more susceptible than untreated counterparts to endosulfan, qulnalphos, fenvalerate and Nimbecidine. Bt-treatment increased the susceptibility of these larvae (1.90 to 2.80 times) to different insecticides. The LT50 values were reduced due to Bt-treatment. The increase in susceptibility was more or less equal against endosulfan, quinalphos and fenvalerate, but high in Nimbecidine with a susceptibility ratio of 4.65 times. The possibilities for the increased susceptibility of Bt-treated DBM larvae to the different insecticides are discussed.
