Repellency of different plant extracts and commercial formulations used as prophylactic sprays to protect bagged grain against Tribolium castaneum: a field study.

Abstract

Nine agents, including acetone extracts of five plant materials, viz., sweet flag rhizomes (Acorus calamus L.), kut root (Saussurea lappa L.), curry leaf (Murraya sp), kinnow peel (Curus nobilis X Citrus deliciosa) and turmeric rhizomes (Curcuma longa L.), and crude mustard oil, two commercial neem formulations (nimbicidin and repellin) and one synthetic pyrethroid (cypermethrin) were evaluated at 1% level as bag treatments for the control of storage insects under warehouse conditions in a thrice replicated trial. The changes were monitored at 2, 4 or 6 months of storage. Rice filled in untreated bags served as controls. The two-way analysis of variance of the insect counts per 100 g grains showed very highly significant differences due to agents and durations of storage (p<0.001). The interaction between these treatments was also significant (p<0.05). The main effects were highly significant for the interaction. Based on the overall insect counts per 100 g grains, cypermethrin and repellin were the most effective with counts of 3.4 and 4.7, respectively, followed by turmeric extract (9.5), nimbicidin and Murraya extract (both 11.1), Acorus extract (13.4), and S. lappa extract (17.1). Treatments of mustard oil and kinnow peel extract were the least effective. Lower insect counts in most of the effective treatments were probably due to their repellent action. Extracts of Murraya, turmeric, S. lappa and nimbicidin showed good repellency against the test insect even after three months of ageing under laboratory conditions, thereby substantiating the results obtained under warehouse conditions.