Behavioral and physiological responses of rice leaffolder Cnaphalocrocis medinalis to selected wild rices

Of four wild rices evaluated, Oryza perennis and O. punctata showed resistance to rice leaffolder, Cnaphalocrocis medinalis (Guenée), whereas O. australiensis and O. nivara were moderately resistant. C. medinalis larvae showed a strong nonpreference for settling and feeding on Oryza australiensis, O. perennis and O. nivara as compared to susceptible IR36 rice variety. Among wild rices tested, however, only O. australiensis, was more preferred for larval settling and feeding than resistant TKM6 plants. The growth index of C. medinalis on all wild rices, except O. punctata was significantly lower than on IR36 and TKM6 plants. First-instar larvae caged on O. perennis showed significantly lower larval and pupal weights than those on other wild rices. Incorporation of dry leaf powder of O. punctata and O. perennis wild rices in an artificial diet caused high larval mortality. Ovipositing gravid females showed less preference for wild rices than for IR36 and TKM6 plants.Based at the International Rice Research Institute (IRRI), P.O. Box 933, Manila, Philippines