Bioefficacy of Podophyllum hexandrum and Podophyllotoxin against Cruciferous Pests

Podophyllum hexandrum Royle, a perennial herb belonging to Berberidanceae grows on interior Himalayan ranges from Kashmir to Sikkim. Methanolic extracts of roots, rhizomes and whole plant as well as podophyllotoxin extracted from the plant were evaluated for their insecticidal properties against three cruciferous pests, viz., Pieris brassicae L., Spodoptera litura Fab, and Helicoverpa armigera Hub. Among the three insects, P. brassicae was more sensitive to different plant parts as well as to the toxin. Mortality ranging from 16.7-73.3, 8.3-66.8 and 12.5-73.6 and LC₅₀ (%) values of 2.34, 4.36 and 2.42 were recorded at 0.5 to 10% concentration of the methanolic extracts of rhizome, root and whole plant against second instar larvae of P. brassicae, respectively after 48 h of treatment. A mortality range of 16.7-60.0% and LC₅₀ value of 571 ppm was calculated at 50-1000 ppm of Podophyllotoxin against second instar larvae of P. brassicae. The mathanolic extracts of whole plant (10%) and podophyllotoxin (1000 ppm) significantly increased the larval and pupal period, reduced the larval and pupal weight and adversely affected the reproductive potential of H. armigera and S. litura compared to their respective controls. Among the toxin and whole plant extract, later was more effective for both the insect species.