Laboratory assessment and prospects of repellent potentiation of naturally occurring plant extractives against the lesser grain bore, Rhizopertha dominica Fabricius (Bostrichidae: Coleoptera)

Abstract

Prevention of food losses during postharvest storage is of paramount economic importance. The use of synthetic chemical insecticides is either not permitted or used restrictively because of the residue problem and health risks to consumers. In view of the above, there is a need for plants that may provide potential alternatives to the currently used insect control agents as they constitute a rich source of bioactive molecules. Available literature indicates that plant extractives could be source for new insecticides. This paper focuses on the current state of new biorational agents for repellent as grain protectants applied in insect-pest management. A screening five naturally occurring indogenous botanicals namely: Acorus calamus Linn. (rhizomes), Annona squamosa Linn.(unripe fruites) and Vitex negundo Linn. (leaves), Gynendropsis gynendra Linn., (seeds) and Ocimum basilicum Linn.(leaves) were formulated in distilled water. Triton X-100 at the rate of 0.5 percent as emulsifier and benzene at the rate of 5 percent as solvent were used were tested for their larval repellent biopotency against Rhizopertha dominica Fabricius and two control were also used in the present investigation. Over all, the highest R. dominica larval repellency was calculated A. squamosa extract showed the highest larval repellency (99.77 per cent) and placed on top followed by O. basilicum (99.54 per cent), A. calamus (99.38 per cent) G. gynendra (99.22 per cent), V. negundo (99.10 per cent) where as in control using Benezene was showed (99.38 per cent) and in absolute control was seen only 79.25 percent larval repellency and placed at bottom of merit.