Scientists at the International Centre of Insect Physiology and Ecology (Icipe) have unveiled two superior, disease resistant napier grass varieties at a time when farmers especially in Western Kenya are being buffeted by low yields due to poor varieties.

The varieties which have come up as a result of aggressive research can withstand the notorious napier stunt disease predominantly in Western Kenya and which wipes a plant within days. The researchers say the two varieties were developed from experiments that led to them to identify the insect (vector) that transmits the phytoplasma bacteria which causes the napier stunt disease.

Principal researcher and project coordinator Zeyaur Khan said that the disease had affected napier production in the region after it was first discovered in Teso, Busia County. “We collected live samples of 20 different species of sucking insects associated with napier grass and reared them in cages feeding them on diseased plants to acquire the phytoplasma,” he said.

“Samples of surviving insects and plants were then tested for phytoplasma. The process led to the identification of a common leaf hopper as the insect vector of the disease and the selection of two varieties, Ouma 2 and South Africa, which have slightly different resistance mechanisms.”
The varieties have been distributed to 15 farmers who would then multiply them and distribute them to fellow farmers.

The International Centre of Insect Physiology and Ecology (Icipe) in Kenya first discovered the napier stunt disease in 2000. Its symptoms are visible in the re-growth that happens after the grass has been cut or grazed on.

Affected plants are recognised by severe stunting and yellowing. It also causes profuse growth of shriveled, unhealthy new plants. NSD also attacks other plants such as rice and fodder grasses such as star grass and Bermuda grass.

Specialised bacteria called phytoplasma cause napier stunt disease. The bacteria stops the grass from taking up the nutrients it needs to grow. The bacteria are also transmitted from plant to plant via an insect (maiestas banda krammer), which is quite popular in fields in western Kenya.

The bacteria are also transmitted through a common practice of propagating split napier grass roots for multiplication. “The disease is also found to be prominent in Ethiopia. Our intention is to spread the resistant crops beyond Kenya, to the larger East African region,” said Prof Khan.

The McKnight Foundation Collaborative Crop Research Programme funded the study.