Impact of Head Smut Disease (Ustilago kameruniensis) on Napier Grass Yields in Smallholder Dairy Production Systems

Abstract

Four consecutive studies were carried out to assess the impact of Napier grass head smut on fodder production as well as to explore alternatives to the popular Bana grass variety in smallholder dairy farms of central Kenya. The results indicated Napier grass, an important basal fodder, was threatened by the disease. The most prevalent coping strategy used by farmers was uprooting affected tillers and stools. However, disposal methods were found likely to perpetuate and spread infection. Of the 150 households sampled 19% had Kakamega I the only known Napier grass head smut resistant variety. A productivity evaluation of three varieties showed that Kakamega I had a higher growth rate (1.04 ern/day) than Kakamega II (0.78cm/day) and Muguga Bana (0.61 ern/day). The three varieties had cumulative dry matter yields of 68.32, 58.3 and 55.5 MT DM/ ha respectively over the experimental period. This was equivalent to respective annual yields of 34.2, 29.2 and 27.8 MT DMI ha for the three varieties. On harvest to harvest basis, the leaf to stem ratio for the three varieties averaged were 2.49,3.32 and 4.98. The cumulative yields of leaf were 48.6,44.9 and 45.7 MT DM/ha respectively. The study confirmed that Kakamega I was resistant to Napier grass head smut. It also indicated that Kakamega II and Clone 13 were resistant. ex-Githunguri, Muguga bana, French Cameroon and Farmer bana were found susceptible with infection rates of 7.1%, 3.6% 18.2% and 50% respectively. From the study it was concluded that Kakamega I is an effective replacement for the existing susceptible varieties. Additionally, on the basis of the higher biomass accumulation and yield, Kakamega I would be the cultivar of choice in all areas of intensive dairy production where forage biomass availability IS critical.