Larvicidal and antifeedant activity of some indigenous plants of Meghalaya against 4th instar Helicoverpa armigera (Hübner) larvae

In the present study, seven indigenous, widely distributed plants of Meghalaya, namely, Pinus kesiya Royle (Pinaceae), Lantana camara Linn. (Verbenaceae), Litsea cubeba Lour. (Lauraceae), Gaultheria fragrantissima Wall. (Ericaceae), Mikania micrantha Kunth.(Asteraceae), Ambrosia artemisiifolia Linn.(Asteraceae) and Eupatorium riparium Regel (Asteraceae) were screened for their larvicidal and antifeedant activity against fourth instar larvae of the cotton bollworm, Helicoverpa armigera (Hübner) under laboratory conditions. The crude extracts of all the seven plants demonstrated a dose dependent increase in bioactivity. However the bioactivity of four plants namely, L. camara, G. fragrantissima, L. cubeba and P. kesiya was significantly higher (p ≤ 0.05) than the negative (solvent) control and extracts of A. artemisiifolia, E. riparium and M. micarantha. Methanol extract of L. camara caused highest oral toxicity with larval mortality ranging between 27.77% and 53.33% across the test concentration (0.25%, 0.5% and 1% w/v) while extract of G. fragrantissima demonstrated the highest feeding deterrence with reduction in larval feeding by50.92% and 70.61% at 0.1% and 0.5% respectively. Crude extract of L. cubeba leaves demonstrated high oral toxicity and feeding deterrence while extract of the needles of P. kesiya showed moderate level of oral toxicity as well as feeding deterrence at the highest tested concentration. Phytochemical analysis of the extracts of these four plants, revealed the presence of five different classes of phytocompounds each of which is known to have deleterious effect on insect pests.Thus it may be concluded that four out of the seven plants possess insecticidal property and can be further investigated for the development of a potent botanical insecticide.