By Dr Jolly Kabirizi
Napier stunt disease (NSD) is caused by a group of phytoplasma, 16SrXI strain bacteria. A leafhopper is the vector of Napier stunt phytoplasma. The disease is currently a major threat to Napier grass fodder production in Uganda.
Symptoms of Napier stunt disease
- Affected plants remain stunted, have short internodes, bunchy appearance and produce very low biomass yields.
- There is twisting or curling along the mid-rib starting at leaf tips, and leaves are reduced to short sword like stubs.
- Under severe dry seasons, the plants dry completely.
- The disease is much more severe and prevalent in poorly managed Napier grass fields and during dry seasons.
- Napier stunt disease incidence of 10% to 90% has been recorded in parts of Uganda where farmers practice zero grazing dairy production system.
- Disease incidence is highest in the Lake Victoria Crescent areas because of the high number of stall-fed animals that depend on purchased fodder due to limited land and the lowest (less than 10%) in highland areas such as Mbale and Kabale districts.
- The disease is spread through the movement of infected planting materials and fodder.
Management of the stunting disease
- Inspect the field regularly, remove and burn all diseased Napier grass stools.
- Use tolerant varieties as a component of an integrated management approach could be an environmentally friendly way to contain this disease in smallholder dairy industry.
- Several new napier grass accessions (Kakamega 1, Kakamega 2, NARO (National Agricultural Research Organization Napier) NAP1; NARO NAP 2, NARO NAP 3, Pakchong variety and others), tolerant to Napier stunt disease and have high biomass dry matter yield (10 to 100 tons per acre per year) are being promoted in different agro-ecological zones of Uganda.
- Improve the health of Napier grass by applying manure or fertilizer.
- When harvesting, cut Napier grass plants leaving a stubble height of 5cm above ground level.
- If the area is seriously affected use alternative grass species such as Brachiaria grass.
- Sensitise neighbours about the transmission mechanism and management of the disease.