Orientation behaviour of pests and beneficial insects is mediated by cues associated with the host-plant complex, like volatiles emitted by herbivore damaged plants or exogenous application of elicitors. We conducted laboratory studies to investigate whether exogenous application of jasmonic acid (JA) influences the developmental stages and mortality of rice leaf folder Cnaphalocrocis medinalis (Guenee), parasitoid behavior of ichneumonid parasitoid, Xanthopimpla flavolineata Cameron on C. medinalis pupae and predatory behavior of coccinellid beetle Micraspis sp. on early instar larvae of C. medinalis.
Green house studies revealed the existence of negative relationship between the increased concentration of JA (0.2 mM to 5 mM) and fecundity of C. medinalis (35.2 to 65.3 eggs female-1) and egg hatchability (20.3 to 62.7%) compared to maximum fecundity (72.2 eggs female-1) and hatchability (82.0%) on buffer-treated control plants. However, positive correlation of higher the concentrations of JA resulted in higher mortality of C. medinalis larvae (84.3 to 38.2%) was observed than mortality on control plants (5.5%). We recorded shorter larval duration of 4.08 to 4.39 days of C. medinalis due to JA concentrations compared to the larval duration of 6.56 days in control plants. Higher the concentration of JA also influenced for lower pupal emergence (25.3 to 65.0%) and lower pupal duration (4.08 to 5.39 days) than higher pupal emergence (85.7%) and pupal duration (6.19 days) in control plants. Use of JA at higher concentrations resulted in lower adult emergence (20.6 to 62.4%) than 82.3 per cent emergence from control plants, and lower adult duration (4.67 to 6.11 days).
Increased concentrations of JA influenced for significant increase in the parasitization of X. flavolineata (72.6 to 40.6%) and predatory potential of Micraspis sp. (81.4 to 38.5%). However, JA in any concentration was not lethal to both parasitoid and predator. There was significant difference in the attraction of pest, C. medinalis, parasitoids X. flavolineata and predators, Micraspis sp. towards olfactometer arms due to JA treated and untreated leaves. The movement of C. medinalis was maximum towards leaves of control plants (5.2 adults with 26.0% attraction) and there was negative influence towards the leaves treated with JA concentration (0.6 to 3.0 adults with 3.0 to 15.0% attraction). However, orientation behaviour of X. flavolineata (1.0 to 3.2 adults with 5.0 to 16.0% attraction) and Micraspis sp. (1.5 to 4.0 adults with 7.5 to 2.0% attraction) was higher towards leaves treated with higher concentration of JA.