Progress in cassava technology transfer in Uganda

This publication contains the full text of papers presented at a Workshop held in Masindi, Uganda, 9-12 January 1996, and sponsored by the Gatsby Charitable Foundation. During the Workshop the need became evident for additional statistics on the multiplication, distribution and uptake of improved varieties of cassava in the six districts where activities are supported by The Gatsby Charitable Foundation and also elsewhere. The results of a subsequent survey in selected sub-counties of each of the six Gatsby districts are also presented here, together with estimates of the amount of improved material that has been distributed and the area now grown. These latest figures (Appendix 1) represent the best available estimates and in some instances differ substantially from those compiled and presented in the earlier district reports

The effect of competition on the control of invading plant pathogens

1. New invading pathogen strains must compete with endemic pathogen strains to emerge and spread. As disease control measures are often non-specific, i.e. they do not distinguish between strains, applying control not only affects the invading pathogen strain but the endemic as well. We hypothesise that the control of the invasive strain could be compromised due to the non-specific nature of the control. 2. A spatially-explicit model, describing the East African cassava mosaic virus-Uganda strain (EACMV-UG) outbreak, is used to evaluate methods of controlling both disease incidence and spread of invading pathogen strains in pathosystems with and without an endemic pathogen strain present. 3. We find that while many newly introduced or intensified control measures (such as resistant cultivars or roguing) decrease the expected incidence, they have the unintended consequence of increasing, or at least not reducing, the speed with which the invasive pathogen spreads geographically. We identify which controls cause this effect and methods in which these controls may be applied to prevent it. 4. We found that the spatial spread of the invading strain is chiefly governed by the incidence at the wave front. Control can therefore be applied, or intensified, once the wave front has passed without increasing the pathogen’s rate of spread. 5. When trade of planting material occurs, it is possible that the planting material is already infected. The only forms of control in this study that reduces the speed of geographic spread, regardless of the presence of an endemic strain, are those that reduce the amount of trade and the distance over which trade takes place. 6. Synthesis and applications. Imposing trade restrictions before the epidemic has reached a given area and increasing other control methods only once the wave front has passed is the most effective way of both slowing down spread and controlling incidence when the presence of an endemic strain is unknow

Influence of NPK fertiliser on populations of the whitefly vector and incidence of cassava mosaic virus disease

The influence of NPK fertiliser on the symptoms and spread of cassava mosaic virus disease (CMD) and on populations of the whitefly vector (Bemisia tabaci) was investigated in Uganda using three cassava varieties: Migyera (CMD-resistant), Nase 2 (tolerant) and Ebwanatereka (highly susceptible) in 1995-96 and 1996-97 planting seasons. In each season NPK fertiliser significantly (

Effects of cassava mosaic virus disease on the growth and yield of cassava - some highlights from Makerere experiments

(African Crop Science Journal 1999 7(4): 511-522