Napier grass diseases a threat to dairy sector

Kenya’s dairy industry is facing a major threat due to the outbreak of stunt and smut diseases affecting napier grass in Central and Western provinces.

The dairy industry is the largest in East Africa producing annually about 85 to 90 million litres of milk equivalent per capita based primarily on well established market oriented smallholder system.

According to Kenya Agricultural Research Institute (Kari), stunt and smut diseases infestation of the grass is rapidly spreading posing a major challenge to growth of the industry. 

Sustainability depends largely on availability of adequate feeds, of which napier grass remains the main fodder crop for zero grazing.

Some clones

Dr Margaret Mulaa of Kari Kitale centre says scientists from Kenya, Uganda, Ethiopia and International Livestock Research Institute (ILRI) are carrying out research to develop disease-resistant napier grass.

“Kenya has planted 120 clones of napier grass at Kari Alupe sub-centre. Some clones have shown tolerance to stunt and smut diseases. The two diseases cause drastic reduction in napier grass biomass by about 90 per cent,” she said. 

It is feared the diseases, if not checked will force farmers to either sell or graze dairy cows on sparse communal pastures along road sides exposing them to risk of contracting East Coast fever.

Increase costs

The fever will increase costs of livestock production due to the need for farmers to treat animals. Napier stunt is caused by tiny bacteria (Phytoplasma) and smut by fungi leading to yield reduction.

Ms Mulaa said grass infested with stunt is safe for livestock to eat, and yields 50 to 100 tonnes of napier grass can be realised if farmers implement recommended agronomic practices. 

Stunting disease was first observed in mid 1990s near Bungoma. Incidents of the infection in the area, Butere and Mumias sugar belt is 30 to 90 per cent of affected plants per field. It has also been observed in Kiambu and Murang’a districts in Central Kenya.

Symptoms of the disease include yellowing of leaves, tiny leaves, shortening of internodes, stunning, decline of vigour and finally death of the plant. It is spread by planting infested stems and root splits.

Kakamega Kari centre director Francis Muyekho said the bacteria lives in grass and small insects (leaf and plant hoppers) and transmits the disease by feeding on infested plants before moving to clean ones.

Napier smut appeared in Central Kenya in late 1980s and is more prevalent in higher areas of Kiambu, Thika, Othaya and Kirinyaga districts. It spreads rapidly by wind and infected plant.

Infected stems are smaller, thinner and with few, small and sometimes distorted leaves. Re-growth of plants infected by Napier smut disease is slow after cutting.

Mr Muyekho said farmers are advised to uproot and burn infested napier grass to manage stunt and smut diseases and use clean planting materials from disease free areas among others.

“Manure from livestock fed on smut infected plants may spread the disease if used. Farmers should not feed animals with plants infected with smut to avoid spreading the disease,” he said.