Field spread of banana streak virus (BSV)

Musa (banana and plantain) provides a major source of carbohydrates for about 400 million people of whom 20 million are from East Africa. Yet, banana is threatened by number constraints, banana streak virus inclusive. Banana streak virus (BSV) was monitored in Rakai and Ntungamo, Uganda for up to 72 months after planting (MAP) and 29MAP respectively. BSV incidence increase over time was fitted into exponential model and spatial spread analysed by 2DCLASS and 2DCORR. BSV infection was initiated in Rakai 29 months after planting (MAP), but only 6 MAP in Ntungamo. BSV incidence then increased at a rate of 0.10 plants respectively / infected plant / month at a rate 0.23 plants / infected plant / month in Rakai and Ntungamo respectively. In both sites, spatial analysis showed that there were significant aggregated BSV spatial patterns. New infections were more likely to occur within a 10 rows/coloumns from an old infection. Significant edge effects were also detected in Ntungamo, indicating that there was significant spread from the immediate surroundings (infected established field suggesting need for separation of new fields from old infected fields to delay onset of BSV. Roguing should be frequent enough to offset rate of BSV incidence increase. The study shows that BSV is a slow spreading disease; however, there is sufficient time in this perennial cropping system for it to increase to epidemic levels. It is however, possible to check the advance of the BSV epidemic through phytosanitary measures.