Bionomics and importance of two species of Chaetocnema in rice yellow mottle virus transmission in lowland rice in Tanzania

Regular samplings were done of two important vectors in farmers' fields during the 1999/2000 and 2000/01 rice seasons at crop stages susceptible to rice yellow mottle virus (RYMV) on a traditional rice variety ('Supa') under rainfed lowland conditions to provide information on the bionomics and importance of these vectors in the disease transmission. The population of Chaetocnema sp. (nr. varicornis Jacoby) (Coleoptera: Chrysomelidae) was significantly higher in hotspot than non-hotspot areas. However, there was no significant difference in the C. pulla Chapuis population between these two areas. In general, the Chaetocnema sp. population was higher than that of C. pulla, and both vectors reached the peak of their population at 63 days after planting. Early planting in the hotspot areas is suggested as a disease management strategy. Both vectors are naturally infective and Chaetocnema sp. proved more efficient than C. pulla in the transmission of RYMV.