Anti-feedant and growth inhibitory effects of seed extracts of custard apple, Annona squamosa against Khapra beetle, Trogoderma granarium

The anti-feedant and growth inhibitory effects of seed extracts of custard apple in hexane, ethyl acetate and methanol were tested against neonate and 7 days old larvae of the Khapra beetle, Trogoderma granarium, using a feeding bioassay. The LC50 values for hexane, ethyl acetate and methanol extracts were 1195.41, 305.36 and 1446.32 ppm for neonate larvae; 5805, 1300 and 5815 ppm for 7 days old larvae, respectively. Drastic reduction in larval weight was observed in all extracts as compared with the control (acetone). The weight of five larvae in the control (acetone) was 6.03 mg after 15 days of release of neonate larvae. In case of Annona squamosa seed hexane extract the larval weight near LC50 (1250 ppm) was 0.65 mg, whereas in ethyl acetate (250 ppm) and methanol extract (1500 ppm) it was 0.91 and 0.90 mg, respectively. Ethyl acetate extract at 1250 ppm showed maximum anti-feedant activity of 44.50 and 59.50% after 10 and 15 days of release, respectively, whereas 35.68 and 53.45 % for hexane extract and 26.07 and 38.65% for methanol extract was observed at same concentration after 10 and 15 days of release, respectively. Annona squamosa seed ethyl acetate extract produced 55.73% anti-feedant activity for 7 days old larvae while hexane and methanol extracts produced 50 and 25.04%, respectively. The present study conclusively showed that A. squamosa seed ethyl acetate extract was superior to hexane and methanol extracts and first such study against Khapra beetle.