Effects of rotenone from derris crude extract on esterase enzyme mechanism in the beet armyworm, Spodoptera exiqua (Hubner).

This research was to elucidate the toxicity and esterase enzyme mechanism of derris crude acssst (Derris elliptica Benth) in the beet armyworm (Spodoptera exigua Hubner) by larvae dipping method. Derris crude extract was extracted by Soxhlet's apparatus with ethanoL solvent. The ethanolic derris crude extract was diluted into 5 concentrations to test the toxicity value. The result showed that the toxicity dramatically increased when the concentration of substance and the time exposure were increased. Toxicity in terms of LC50 value against 2nd instar larvae indicated that ca. 69.15 (r2 = 0.98), 51.32 (r2 = 0.99) and 46.60 (r2 = 0.98) ppm at 24, 48 and 72 hours, respectively. The in vivo study with Yang et al. (2004); Visetson and Milne (2001) modified method, revealed that the derris crude extract inhibited esterase enzyme activities ca. 0.75-1.07 fold without a change in the protein concentration. This result indicated that, derris crude extract had efficacy as an insecticide, therefore it had the potential to be another insecticide alternative in S. exiqua control. Moreover, some separate experiments indicated that this extract was safe to human and the environment.