The Distribution, Incidence, Natural Reservoir Hosts and Insect Vectors of Rice Yellow Mottle Virus (RYMV), Genus Sobemovirus in Northern Nigeria

Field visits and surveys were carried out in Niger, Kano, Bauchi and Gombe states of northern Nigeria at tillering and panicle initiation stages of rice in the years 2000 and 2001 to determine the distribution, host plants and occurrence of insect vectors of Rice Yellow Mottle Virus (RYMV). Farmers' cultural practices and field situations were also assessed. Visual inspection based on the Standard Evaluation Scale (SES) and enzyme linked immunosorbent assay (ELISA) methods were used in detecting RYMV infection. RYMV presence was established in all the four states surveyed. The virus was widely distributed in Kano state. The insect vectors of RYMV, such as Trichispa sericea Guerin, Chaetocnema pulla Chapius, Chnootriba similis Thunberg and Conocephalus longipennis de Haan, were found in the 4 states. Outbreaks of T. sericea occurred in many farmers' fields in Kano state. RYMV was detected more frequently on Oryza sativa L. than on O. longistaminata Chev. & Roehr and Echinochloa pyramidalis Hitche and Chase.Virus infection was not established in any other grass species, sedges and broadleaf plants tested. It is evident therefore, that RYMV has a narrow host range and is found more frequently in the Oryzeae