Epidemiology of Banana streak virus (BSV) in East African highland bananas (AAA-EA)
The study achieved a better understanding of the epidemiology and ecology of Banana streak virus (BSV) in Uganda, generating information useful in designing management strategies to limit the spread of BSV. An identification key for the mealybugs on Musa in Africa was constructed. Screenhouse transmission experiments identified Dysmicoccus brevipes, Planococcus citri and a Pseudococcus sp. from bananas as mealybugs able to transmit the virus. Field observations also demonstrated that mealybugs are able to spread from plant to plant. Monitoring spread of BSV in new fields revealed that both onset and rate of spread was site specific; however, it was not clear why this was the case. The first incidence of BSV infection in Rakai was 28 months after planting (MAP), but in Ntungamo it was only 6 MAP. BSV incidence then increased to 28%, 72MAP at a rate of 0.10 new infections/infected plant/month and 43%, 28MAP at a rate of 0.23 new infections/infected plant/ month in Rakai and Ntungamo respectively. BSV spreads slowly in some locations, and is therefore probably amenable to control by phytosanitary measures. These would comprise primarily of the use of virus-free planting material and roguing infected plants. BSV spread predominantly within-field once initial infections were established. New infections were more likely to occur within 10 rows/columns from an old infection. More spread occurred to plants bordering established infected fields in Ntungamo. Spread of BSV into the new fields from the surroundings suggests need for separation of new fields from old infected fields in order to delay onset of BSV and reduce BSV incidence.