Author(s):

Nandini KN and N Srinivasa

Abstract: Biological activity of methanol extracts from leaves of four different species of Vitex namely, V. negundo (purple), V. negundo (white), V. altissima, V. peduncularis and V. trifolia was studied on red spider mite, Tetranychus macfarlanei infesting okra crop. Toxicity parameters such as repellence (walk- off), mortality were determined by releasing adult mites on okra leaves treated with extracts under laboratory conditions. Among the methanol extracts of different Vitex spp. Per cent walk-off of adult mites from treated okra discs differed significantly 6 and 12 hours interval. Repellent property showed marginal increase from 6 hours to 12 hours in most of the treatments except in V. peduncularis at 10% concentration, with which walk-off response remained lowest and same i.e., 13% up to 12 hours after six hours per cent walk-off was maximum, 72 per cent with V. negundo (purple) extract at 20% concentration followed by V. trifolia at 15% with 59 per cent walk-off. V. negundo (purple) extract at 20% was superior with the highest walk-off of 73% upto 12 hours, so also the walk-off with V. trifolia extract at 15% concentration. Among the species of Vitex, repellent activity of V. negundo (purple) at 20% concentration and of V. trifolia at 15% was more apparent. Mortality of adult mites in various treatments differed significantly at all the intervals of 24, 48 and 72 hours. Extract of V. negundo (purple) at 20% recorded highest mortality of 89 per cent at 72 hours followed V. peduncularis at 14% (79% mortality) and V. negundo (white) at 12% (78% mortality) and were statistically on par with each other. It was evident that V. negundo (purple) methanol leaf extracts caused maximum mortality of mites i.e., 89 per cent at 20% concentration. The lowest mortality record was less than 50 per cent i.e., 48 per cent with the same species of Vitex at the lower concentration of 15%.

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