Pervasive use of poor quality seed remains an important reason for low yields throughout the developing world. We attempt to increase the quality of the local stock of seed tubers among a sample of Irish potato farmers in Uganda. We do this by providing agricultural extension information about (i) how to select the best seed tubers and (ii) how to properly handle and store the seed potatoes until the next planting season. The information is provided through appealing videos, shown to individual farmers on mobile devices. While we find some effects on knowledge immediately after having shown the video, this effect has vanished one year later. We also find no effect of the videos on practices, input use, and final outcomes such as yield and consumption. However, there are signs that spillovers between treatment and control farmers may affect our results. After modeling spillovers among neighboring farmers, we find evidence that especially the video containing information on seed selection translated into adoption of improved practices, higher yields and increased welfare. Acknowledgement : We would like to thank the Embassy of the Netherlands in Uganda for funding this research through the Pasic project. We also thank the Ugandan Ministry of Agriculture, Animal Industries and Fisheries (MAAIF), Economic Policy Research Centre (EPRC), National Agricultural Research Organization (NARO) and Kabale Zardi, and the International Fertilizer Development Centre (IFDC). We would like to thank Marc Charles Wanume for excellent field support. Senne Vandevelde acknowledges funding from the grant Policy Design and Evaluation Research in Developing Countries Initial Training Network (PODER), which is funded under the Marie Curie Actions of the EU's Seventh Framework Programme (Contract Number: 608109).