Ovipositional responses of Chilo partellus (Swinhoe) (Lepidoptera: pyralidae) to natural products from leaves of two maize (Zea mays L.) Cultivars

Ovipositional responses of Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) to hexane extracts of leaves of two maize (Zea mays L.) cultivars, one resistant (Kisan) and one susceptible (Basilocal), were studied in two-choice bioassays. Gravid females laid a significantly higher percentage of eggs on substrates smeared with extract of Basilocal leaves (HEBL) (69%) than on those smeared with extracts of Kisan leaves (HEKL) (31%). Several chemicals were isolated from HEKL, three of which were characterized as dotriacontanol, heptadecanol, and nonadecanol. These chemicals were either absent or were present in very small amounts in HEBL, but in HEKL they were detected in much larger amounts. Each isolated chemical was tested for its effect on C. partellus oviposition in two-choice bioassays. Maximum ovipositional deterrence (90%) was observed for the compound MR-22a, followed in decreasing order by nonadecanol, MR-7, and heptadecanol. The identity of the remaining compounds is being investigated. The results indicate that the relative resistance of Kisan maize compared to Basilocal is partly due to the presence of certain ovipositional deterrents in its leaves.