Napier Stunt

Lead Organization:

International Center of Insect Physiology and Ecology

Community of Practice:

East & Southern Africa






The dairy industry represents one of the most important income-generating activities for resource poor smallholder farmers in East Africa. In Kenya alone, an estimated 600,000 farmers produce 80% of the milk consumed in the country. Napier grass (Pennisetum purpureum) is the most important livestock feed in these systems, and is also an important plant for soil management and widely used for agro-ecological management of stemborers and Striga on cereal crops. Recently, a new stunting disease of Napier grass has emerged, devastating Napier grass yield by 70 percent and contributing to a significant decline in milk production. There is potential risk for the disease spreading to food crops and posing a serious threat to food security. While initial research has helped to identify and study the disease vector (the leafhopper), effective management strategies for the disease are limited. Building on vector knowledge, the project seeks to develop and implement an integrated management approach for the disease to be implemented in Western Kenya, Eastern Uganda and Northern Tanzania. Focusing on stakeholders in the dairy value chain in target areas, the project will focus on building the capacity on disease diagnosis and management, and animal husbandry with the aim of stabilizing dairy and cereal production, increasing milk / cereal yields and income, and improving nutrition and livelihoods in the eastern Africa region.  

Grant Aims:

Screen Napier grass varieties for resistance to Napier stunt diseaseScreen for existence of any vector and disease biotypes in the target areasScreening alternative fodder grasses for resistance to stunt phytoplasmaCarry out transmission studies of the stunt phytoplasma to food crops (sugar cane, rice, finger millet, and pearl millet)

Outputs and Outcomes:

To confront the devastating epidemic of NSD, germplasm was collected and tested for NSD resistance. The team collected 241 varieties of Napier grass (70 varieties from a stock held by the Kenya Agricultural Research Institute (KARI) and 171 varieties from farmers’ fields, including 3 varieties from Uganda). Identification through Amplified Fragment Length Polymorphism (AFLP) genotyping has been initiated and 36 varieties have been fingerprinted. Preliminary results indicate that a total of 42 of the screened napier grass varieties are susceptible to stunt phytoplasma (positive by nPCR and LAMP, with fully expressed disease symptoms); 6 varieties are tolerant (positive by nPCR and LAMP but with no disease symptom expression); 2 are resistant (negative by nPCR and LAMP with no disease symptom expression). In addition, 52 wild grass species were assembled for evaluation as potential alternative fodder species, and 23 were screened for NSD resistance. Several resistant species were identifiedBrachiaria cv mulato was found to be resistant, while Guatamala, fodder sorghums and giant setaria were found to be tolerant as they were positive for phytoplasma but remained asymptomatic. Farmer evaluation of these materials showed that Brachiaria cv mulato was ranked highest as an alternative fodder for animalsUsing nPCR and LAMP detection techniques, 2 of the 50 napier grass cultivars tested negative to the stunt phytoplasma81 (13%) of the 646 wild grasses tested for presence of stunt phytoplasma were positive. The wild grasses were collected from Bungoma and Busia counties of western KenyaInfection in Busia was widely spread across many grasses with infection rates of 7-22%, while in Bungoma infection was high on 2 grasses – Cynodon dactylon 35% and Brachiara brizantha 18.5%Phylogenetic analyses grouped detected phytoplasmas into 2 clades, Napier stunt disease (NSD) and Bermuda Grass White Leaf Disease (BGWLD)The sorghum variety 65518 was tolerant with 83-91% of plants having phytoplasma, but remained asymptomatic by 3 months; fodder grass Brachiara cv. Mulato was negative to both stunt phytoplasma and symptom development; sugar cane, rice, finger & pearl milled exposed to napier stunt phytoplasma acquired the pathogen. Working to evaluate pathogen persistance and symptom expression