International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria.
*Present address: Crop Protection Specialist, Cambodia-IRRI Rice Project (CIRP), Department of Agronomy Building, Lot 14, Pokambor Street, Phnom Penh, Cambodia.
Lepidopterous stem borers attacking rice in Nigeria were monitored during 1990 rainy season on two lowland irrigated rice varieties, viz., ITA 212 and Suakoko 8. The African white stem borer, Maliarpha separatella Rag., was the dominant species among the other lepidopterous stem borers, viz., Chilo zacconius Bles. and Sesamia calamistis Hemps. Larval and pupal numbers were highest on 80 weeks after transplanting (WAT) on ITA 212 as compared to Suakoko 8 on 100 WAT. The bored tillers in ITA 212 (20.24%) were lower than in Suakoko 8 (50–654). The number of African white stem borer immature stages (larval and pupal) decreased with increase in age of ratoons.
