Abstract

                                The enzyme activity in the field population of diamondback moth was assessed and mixed function oxidase (MFO) was high in all the three locations compared to glutathione-S-transferase (GST) and carboxyl ester hydrolase (CEH). Results revealed that there was high increase in MFO enzyme activity in Coimbatore, Oddanchatram and Udhagamandalam populations due to exposure of insecticides. MFO activity was high in Oddanchatram population recording 98.72, 82.29 and 96.00 per cent as influenced by the application of fenvalerate, carbosulfan and monocrotophos, respectively after 12 h of treatment than Coimbatore and Udhagamandalam populations. The specific activity of GST varied from 367.34 to 506.29, 370.26 to 512.26 and 370.26 to 455.56 at 12 h after the application of fenvalerate, carbosulfan and onocrotophos, respectively in all the three populations. CEH activity was noticed only in the case of fenvalerate and it ranged from 1554.23 to 2379.12, 1355.82 to 2186.21 and 1554.23 to 2025.46 at 6 h after application in Coimbatore, Oddanchatram and Udhagamandalam, respectively.

Key words : Detoxifying enzymes, MFO, GST, CEH, Resistance, Insecticide, Plutella xylostella.