none In the Chitwan valley, Nepal, Chilo partellus preferred maize and sorghum over rice, teosinte, finger millet and sugar-cane. Infestation on young maize plants produced "dead hearts" and on older plants reduced growth and sometimes prevented cob formation. The yield reduction in some maize cultivars reached 60% and stem infestation levels reached 98%. Borers produced "dead hearts" in young and "whiteheads" in older rice plants. The egg, larval and pupal periods from April through September lasted 4-5, 16-41 and 4-8 days, respectively. A complete generation took 28-48 days under summer field conditions and 192-233 days from October to May. Of the one egg, four larval and two pupal parasitoids, all hymenopteras, which were reared from C. partellus , the two most important were Trichogramma chilonis (70% egg parasitism) and Apanteles flavipes (30% larval parasitism).