INSECTICIDAL PROPERTIES OF SUBTROPICAL PLANT EXTRACTS AGAINST NYMPHS OF WHITEFLY BEMISIA TABACIGENNADIUS

摘要

Leaves and seeds extracts of eight sub-tropical plants, namely, Azadirachta indica, Boswellia sacra, Myrtus communis, Annona squamosa, Sueda aegyptica, Acacia nilotica, Crotolaria juncea and Jatropa dhofarica were prepared by steeping 12.5 gm of shaded dried leaf/seed powder of the plants in 62.5 ml water-ethanol (1:4 v/v) for 24 hours. The extracts were suction filtered. Required quantity of filtrate was diluted with water to get 1, 1.5, 2, 2.5 and 3 per cent spray solutions respectively. Tomato leaves with whitefly nymphs were used to test the insecticidal properties of the extracts. The leaves were kept in contact on filter papers for 2 hours just before spraying and for 24 hours after spraying of extracts. The filter papers were sprayed with ninhydrin (0.4% in ethanol) and kept in oven at a temperature of 80 deg C for 2 minutes, which developed purple spots due to honeydew secreted by whitefly nymphs. The difference between the number of spots before and after spray gave the mortality of nymphs. Data analyzed by PAIRED T-test using S AS for the mortality of nymphs for all the extracts including the control, revealed that A. squamosa caused the highest mortality from 2% concentration onward. This is followed by A. indica, A. nilotica and C. juncea at the same concentration as A. squamosa. Extracts of B. sacra and /. dhofarica were effective only at 2.5 and 3 percent concentrations. The control was similar to M. communis and S. aegyptica being nonsignificant.