Assessment of Allelopathic Potentiality of Vimraj (Wedelia chinensis) Against Some Stored Grain Insect Pests

Vimraj (Wedelia chinensis) possesses potential bioactive compounds that may offer an eco-friendly alternative to synthetic insecticides for managing major storage pests. This investigation was conducted at the Department of Entomology, Bangladesh Agricultural University, Mymensingh, to assess the allelopathic potentiality of vimraj leaf extracts against rice weevil. A single-factor experiment was carried out following a completely randomized design (CRD) with three replications. Three treatments were applied viz. 100% methanol extract of vimraj leaf, 70% aqueous methanol extract of vimraj leaf, and 50% aqueous methanol extract of vimraj leaf. Each treatment was tested at three doses: D1 – 2.0 ml extract/20 g grain, D2 – 1.5 ml extract/20 g grain, and D3 – 1.0 ml extract/20 g grain. The results revealed significant effects of these treatments on adult mortality of the tested insect pests. Both 100% methanol extract and 70% extract at higher doses showed 100% mortality for all three pests, indicating strong allelopathic activity. In contrast, 50% methanol extract showed statistically insignificant effects on red flour beetle and pulse beetle mortality across all doses. The effectiveness of the extracts increased proportionally with higher doses, and 100% methanol extract at the lowest dose was least effective against rice weevil. Overall, the results suggest that methanol extracts of vimraj (Wedelia chinensis) leaf may be used as effective and eco-friendly bioinsecticides, provided proper concentrations and doses are maintained for managing storage insect pests.