A survey of 218, mainly male, cashew farmers conducted in three Tanzanian cashew-growing Districts recorded farmers' knowledge of cashew powdery mildew disease caused by Oidium anacardii Noack and its control. The survey complemented a wider study of cashew powdery mildew disease management knowledge and information systems. The overall objective was to identify difficulties in, and solutions to, implementing IPM to minimise costly and environmentally harmful use of sulphur fungicide. Over 90% of farmers in Newala and Nachingwea Districts, and 70% of respondents in Mkuranga District, used sulphur dust. Most farmers believed that sulphur was essential for protecting cashew flowers from damage by mist - 'mist disease', and for increased production, and knew no ways of reducing use of sulphur. A minority of farmers had some knowledge of the life-cycle of O. anacardii and of the possibility of linking cultural practices to remove infection sources with reduced need for sulphur later. This farmers' knowledge was related directly or indirectly to official research and extension sources, and to their own observations and experiments. Their efforts to implement these IPM strategies reflected interest in reducing costs but were also limited by gaps in biological understanding and by difficulties in sharing IPM concepts and field tasks in the villages. Many farmers (44%) in Newala reported using more than recommended sulphur rates, whilst a majority (66%) of farmers in Nachingwea reported using well below recommended rates. These results suggest farmers' independent adaptation of standard recommendations according to perceived needs and opportunities. Sulphur-based control of cashew powdery mildew, particularly at the higher rates reported used in Newala, appeared to be highly vulnerable to low cashew prices. The diverse information sources used by farmers afforded little or no access to details of cashew powdery mildew disease nor alternative ideas about its control. The implications for future IPM-related research and for communication of research results are highlighted.