Abstract

In a previous experiment, sweetpotato whitefly was found to be difficult to control with either neem or Beauveria bassiana alone. This earlier research also reported that the combined application of neem and B. bassiana increased mortality of whitefly nymphs when both of these products were applied to eggplant foliage; but a higher concentration of neem (more than 0.5%) was slightly toxic for young eggplant. Therefore, the present research was undertaken with these two products in which neem was applied as soil drench and B. bassiana was applied to foliage. Three concentrations of neem- 0.25, 0.5 and 1.0%; and three concentrations of B. bassiana- 10⁶, 10⁷ and 10⁸ conidia/ml were used to investigate the combined efficacy against sweet potato whitefly, Bemisia tabaci. The results demonstrate that maximum nymph mortality (92.3%) occurred when 1.0% neem was combined with 10⁸ conidia/ml of B. bassiana. The highest (14.3) mortality ratio (N/Bb; mortality caused by neem/mortality caused by B. bassiana) occurred when 1.0% neem was combined with 10⁶ conidia/ml of B. bassiana; and the lowest mortality ratio (5.7) occurred when 0.25% neem was combined with 10⁸ conidia/ml of B. bassiana. The results showed that neem was compatible with B. bassiana; and suggest that soil application of neem along with foliar application of B. bassiana might be useful for the control of B. tabaci.     

Key words: Botanical insecticide, compatibility, eggplant, entomopathogenic fungus, integrated pest management (IPM).