As a result of repeated application of insecticides on brinjal most of the lepidopteron pests may have developed resistance. In general, newly developed compounds are desired not to show cross resistance with existing insecticides. With this background, field population of L. orbonalis from brinjal which was known to be tolerant to most of the conventional insecticides were collected and subjected to the in vivo toxicity of spinetoram 12 SC to assess whether cross resistance exists. Untreated larvae of both field and laboratory strains showed no mortality during the 48 hours of feeding. After 48 hours of feeding on spinetoram 12 SC-treated fruits, LC50s of field larvae were 0.097, 0.45, 3.13 and 6.58 ppm for the 2nd, 3rd, 4th and 5th in stars of L. orbonalis respectively. However, in the laboratory strain these values were 0.76, 1.92, 17.37 and 49.55 ppm for 2nd, 3rd, 4th and 5th in stars of L. orbonalis respectively. The results confirmed the greater LC50 of the laboratory strain than of the field strain.

Download this article as