Effects of the hexanic extract of neem Azadirachta indica against adult whitefly Bemisia tabaci

The aim of this study was to evaluate the insecticidal and repellent efficiency of the hexanic extracts of seeds of neem Azadirachta indica on whitefly Bemisia tabaci adults. Bioassays were performed by testing seeds collected in 2007 (NEEM-1) and in 2008 (NEEM-2). Mortality was assessed with five levels (5-10%) and repellence at two levels (5 and 10%), for 8 hours. Water and Dichloromethane (0.1%) served as controls. The lethal median concentration of neem, analyzed by Probit, was 6.55%. The concentration of 10% (both, NEEM-1 and NEEM-2) produced 100% of mortality, NEEM-1 since the second hour of evaluation, whereas NEEM-2, since fifth hour of assessment. NEEM-1 and NEEM-2 (10%) produced 100% of repellent activity since seventh and sixth hour, respectively. Nevertheless, significant differences were not observed between the times of storage-collection for both extracts. It is recommended to achieve field studies that expand these results in vitro.