Mathias Ndalahwa1, *Juma Yabeja1, Kiddo Mtunda2, Innocent Ndyetabula3 and James P. Legg1

Community Phytosanitation Action proves increase in cassava productivity and market of tuberous roots in Tanzania

1) International Institute of Tropical Agriculture (IITA), P.O.BOX 34441, Dar es salaam, Tanzania, 2) Sugarcane Research Institute, P.O. BOX 30031, Kibaha, Tanzania, 3) Maruku Agricultural Research Institute, Bukoba, Tanzania.

* , Registrant ID# 3256

Cassava is the second most important food crop after maize in Tanzania. Yields of cassava in Tanzania are currently less than half the average for Africa and one of the most important causes for these low yields is the impact of the cassava virus disease: cassava brown streak disease (CBSD) and cassava mosaic disease (CMD). CBSD reduces yields both by reducing plant growth and by causing a dry necrotic rot in the tuberous roots of affected plants. The disease has spread greatly in Tanzania in recent years, and there is therefore a major effort being made to control it and mitigate its deleterious impacts on food security. As part of this effort, one project seeks to use community phytosanitation approaches to limit CBSD spread and reduce losses within selected target communities. Participating communities included two villages in north-western Tanzania, in Chato and Muleba Districts, and two villages in the coastal region, in Mkuranga and Kisarawe Districts. A three-step approach was taken comprising: i) community sensitization on the approach ii) removal of existing CBSD-affected cassava crops, and iii) replacement with CBSD-free planting material of an improved variety. Detailed experimental data were collected from selected participating farmers at regular time intervals in order to document the technical outcomes of the project. Cassava fields of four groups of farmers were monitored: Primary Recipient Group (PRG) farmers – selected from the first group in the village to receive CBSD-free planting material; Secondary and Tertiary Recipient Group (SRG; TRG) farmers – who received stems of the new variety in the second (SRG) and third (TRG) seasons; and Control Recipient Group (CRG) farmers – who were ‘check’ farmers in a non-target village who were not grouped together, and who did not apply any phytosanitation (roguing or selection of CBSD-free stems for replating). In each of the monitored fields, records were taken of CBSD incidence and severity, whitefly abundance and yield at harvest. In addition, a standard approach was used to calculating the inoculum pressure in the immediate surrounds of each monitored field and samples were collected from both symptomatic and asymptomatic plants in order to test for the presence of the two virus species that cause CBSD. In this report we summarize the incidences, severities and yields obtained for each of the groups of farmers from target villages in Chato and Mkuranga Districts. Overall, the study has demonstrated that the monitoring approach has been effective in documenting CBSD in target communities, that there is a strong negative relationship between CBSD incidence and yield and that low levels of CBSD incidence can be sustained for several seasons following the supplying of CBSD-free planting material and the application of community phytosanitation measures. Further effort, however, is required to prove that the benefits of community phytosanitation + CBSD-free planting material are significantly greater (and therefore worth the additional cost) than provision of CBSD-free planting material without community phytosanitation.