Possible Mechanisms of Resistance to Endosulfan in the Larval Population of Spodoptera litura Fab.

Guntur population of Spodoptera litura larvae developed 8.09 and 23.73 fold resistance to endosulfan in comparison with Chittoor population, and 22.16 and 122.22 fold in comparison with baseline data by topical application. By leaf sandwich method, the same population showed 7.70 and 11.90 fold resistance at LD₅₀ and LD₉₀ in comparison with Chittoor population. Endosulfan in combination with PBO (1:10) showed synergistic factors of 4.90 and 16.71 by topical application and 5.99 and 8.45 by leaf sandwich ingestion and the same insecticide in combination with TPP (1:10) showed the synergistic ratios of 1.13 and 2.95 by topical application and 1.19 and 1.57 by leaf sandwich method at LD₅₀ and LD₉₀, respectively. Thus, the resistance in S.litura to endosulfan was largely due to MFO and slightly due to esterases.