Complex Feeding behaviour of Spotted bollworm, Earias vittella Fab. to Bt-treated food

The feeding behaviour of spotted bollworm, Earias vittella Fab. to Bacillus thuringiensis (Bt) treated okra fruits was studied in the laboratory. Feeding deterrency was observed for the moderate range of Bt (Biobit, 32,000 IU mg⁻¹) i.e., 0.025% (= 8.0 X 10² IU ml⁻¹), as evidenced by the lower mortality caused at this level (13.67%) than the higher mortality (16.67%) at the preceding Bt-concentration (0.0125%). Avoidance to the Bt-treated okra was demonstrated which increased with an increase in the Bt concentration. At concentrations higher than the median lethal limit (0.498 and 0.0166% at 24 and 48 h, respectively), this effect was masked by the lethal action of toxin on the target insect.