Abstract

                                Cues associated with the host-plant complex, volatiles emitted by herbivore damaged plants and/or exogenous applications of elicitors decide on orientation behaviour of pests and beneficial insects. We conducted laboratory studies to know whether exogenous use of methyl salicylate (MeSA) influences on developmental stages and mortality of rice leaffolder, Cnaphalocrocis medinalis (Guenee), and biocontrol services of a ichneumonid parasitoid, Xanthopimpla flavolineata (Cameron) and a coccinellid beetle Micraspis sp. on C. medinalis. Results of green house studies revealed that MeSA at 100 mg L^-1 significantly influenced the fecundity (38.4 eggs female^-1), egg hatchability (25.0%) and larval mortality of C.medinalis (75.0%) when compared to fecundity (75.0 eggs female^-1), hatchability (80.7%) and larval mortality (5.0%) due to buffer-treated control plants. MeSA at 100 mg L^-1 also resulted in extended larval, pupal and adult duration of 7.11, 7.92 and 6.83 days, respectively as against the larval, pupal and adult duration of 6.08, 6.67 and 4.93 days, respectively in buffer treated control plants. MeSA at 100 mg L-1 also effected for lower pupal (28.5%) and adult (25.0%) emergence, than higher pupal (82.5%) and adult (85.0%) emergence in control plants. MeSA at 100 mg L^-1 influenced for significant increase in the parasitization of X. flavolineata (70.0%) on C. medinalis pupae and predatory potential of Micraspis sp. (80.2%) on C. medinalis larvae. However, MeSA in any concentration was not lethal to both parasitoid and predator. There was significant difference in the attraction of C. medinalis, X. flavolineata and Micraspis sp. towards olfactometer arms due to MeSA treated and untreated leaves. The movement of C. medinalis was maximum towards leaves of control plants (5.5 adults with 28.0% attraction). This experiments revealed that MeSA treated rice leaves showed the less preference of C. medinalis adults (0.8 to 2.8 adults with 3.0 to 20.0% attraction). However, orientation behaviour of X. flavolineata (1.0 to 3.0 adults with 5.0 to 15.0% attraction) and Micraspis sp. (2.0 to 4.2 adults with 10.0 to 20.0% attraction) was higher towards leaves treated with MeSA concentrations.

Key words : Rice plants, Methyl Salicylate, Cnaphalocrocis medinalis, Developmental characteristics, Xanthopimpla flavolineata, Micraspis sp.