Farmer knowledge of cassava brown streak and cassava mosaic diseases in Tanzania

Abstract

The virus diseases – cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) – are the most important biotic constraints to cassava production in Tanzania. They are being addressed through the dissemination of improved cassava varieties through a formalized seed (= planting material) system. For this to succeed, however, it is essential that producers of cassava seed and roots can recognize and manage the diseases. A baseline study was therefore conducted to assess farmer knowledge of CBSD and CMD in north-western and southern Tanzania. Sixty farmers were interviewed to assess their knowledge and understanding of cassava diseases. All 60 farmers were aware of the symptoms of CBSD and CMD, although few knew their names. Most use a variety of local names for these diseases, such as cassava fever, cassava fog, or other local language names that refer to other pests and diseases. None of the farmers knew the cause of CBSD, although one farmer was aware that viruses cause CMD. Most farmers had no suggestion about how these diseases spread, although some associated spread with harvesting tools (1.7 %) or drought (3.4 %). Most farmers had not received information about CMD or CBSD from any source. Information sources that were reported were extension services and cassava seed producers. The majority (>71 %) of the interviewed farmers did report selecting vigorous plants for planting material in the hope of minimizing negative impacts of diseases. When choosing varieties, farmers selection criteria, in order of importance were: high yield, sweetness, storability, disease resistance, and accessibility. More than 80 % of farmers met their seed requirements by recycling material either from their own or neighbours’ plots, while 17 % sourced improved varieties obtained from seed producers. Farmers reported recycling their saved seed for an average of 7.9 years. Of the farmers who had previously grown improved varieties, 14.3 % had returned to growing local varieties primarily due to marketing challenges, but 85.7 % continued to grow the improved material. Overall, these results highlight continued weaknesses in farmer knowledge and understanding of cassava virus diseases and their associated crop losses, as well as limited recognition of the benefits of high-quality certified planting material of improved varieties. This emphasizes the need for further farmer awareness creation through training and provision of extension advice as well as strengthened efforts by cassava breeders to develop varieties that combine virus disease resistance with the other key traits demanded by farmers.