Efficacy of Vitex negundo (L.) leaf oil extract agains diamondback moth herbivory of cabbage (Brassica oleracea L.)
2002
Estira, F.R. | Raguini, P.A.G. (Mariano Marcos State Univ., Batac, Ilocos Norte 2906 (Philippines). Coll. of Arts and Sciences)
The dangers of insecticides to human and to the environment have initiated biologists to choose other means of preventing insect infestation on crops by the use of botanical materials. This study was conducted to evaluate the efficacy of utilizing Vitex negundo leaf oil extract as an environment friendly pesticide. Cabbage (Brassica oleracea L.) leaves sprayed with four preparations at varying concentrations (20 percent, 40 percent, 60 percent, 80 percent) of V. negundo L. essential oil extract were exposed to herbivory of four larval stages (1st, 2nd, 3rd and 4th instars) of the common crucifer pest, diamonback moth (DBM). To test the efficacy of the extracts in controlling infestation by the DBM, mortality ratio after 8, 16 and 24 hours of exposure were determined. Results revealed that mortality ratio is higher at earlier larval stages as well as when these are exposed to higher concentrations of extract. Later larval stages are less sensitive to the V. negundo extract and that greater concentration of oil is more effective in causing mortality to the 3rd and 4th instars. Regardless of duration of exposure, earlier stages (1st and 2nd instars) of DBM larvae are highly sensitive to V. negundo leaf oil extract while later stages (3rd and 4th instars) of the larvae are less sensitive.
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