Napier grass commonly known as elephant grass is an important fodder in Uganda and has been increasingly associated with intensive (stall-feeding/zero grazing) and semi-intensive dairy cattle and goat production systems to meet the increasing demand for milk and meat.
The grass is widely used for soil and water conservation in hilly slope areas. Napier grass has been identified as an important tool in the integrated management of stem borers of maize and sorghum due to its importance as a trap crop for these pests.
The push–pull effect is established by exploiting semiochemicals to repel insect pests from the crop (‘push’) and to attract them into trap crops (‘pull’) e.g. Napier grass.
Napier stunt disease
With the expansion of Napier grass crop, however, has come a new disease called ‘Napier Stunt’ also known as kugengewala. The disease was first observed on farmers’ fields in Masaka district in 2000. Affected Napier grass plants remain stunted, have short internodes, bunchy appearance and produce very low fodder yields. Leaves of some affected plants begin to dry at the edges and have a ‘torn’ appearance. Yellow/purple streaking starting at leaf tips. The yellowing should not be confused with yellowing due to poor soils. Eventually the stool may be completely destroyed.
Causes and spread of Napier stunt disease
The disease is caused by phytoplasma, microscopic bacteria found in phloem cells of plants and transmitted mainly by insect vectors (leaf and plant hoppers,”:amayanzi”) when they feed on infected plants.
Major methods of spreading Napier stunt disease on-farm are:
• Movement of infected planting materials by farmers
• Ignorance on symptoms and mode of transmission
• Poor agronomic practices
Studies conducted at the National Livestock Resources Research Institute (NaLIRRI) have shown over 90 percent of Napier grass fodder fields in Uganda are affected by this disease.
However, the most affected districts are those located around Lake Victoria Crescent areas where zero grazing dairy cattle production is a major enterprise. Due to limited land, farmers tend to search for Napier grass from other places and in the process transport infected plants from one place to another. The disease is much more severe and prevalent in poorly managed Napier grass fields.
Effect of the disease on fodder and animal production and household income
• The total herbage yield of Napier grass is reduced by over 80%.
• While a healthy acre of Napier grass fodder when properly supplemented should provide feed to sustain one mature cow and its calf for about six months, fields affected by the disease may support the same animal for less than 3 months, greatly reducing milk yields and household income.
• The reduction in fodder yield forces farmers to buy grass to compensate for declining production or to reduce the number of animals. This could be a source of ticks and poisonous plants.
• Many smallholder dairy farmers struggle to make up for the lost biomass due to the disease by stepping up feed supplementation resulting into an increase in cost of supplements per day by 200 per cent.
• Farmers have raised the quantities of manure applied per acre by one tone. This changed the cost of manure application by about Ushs 34,400 per acre per year
Napier stunt disease management
• Uproot and burn diseased plants
• Plant disease free cuttings or splits
• Use recommended agronomic practice (spacing; fertilizer application; proper cutting intervals and cutting heights). Applying manure to the fodder fields reduces disease incidence by over 40%
• Farmers are advised to contact their extension staff or NaLIRRI researchers
• Use Napier grass varieties that are tolerant to the disease
• The institute is producing hay on commercial basis for sale to farmers.
The writer is a livestock expert