Stocks of narcissi infected withFusarium bulbigenumwere divided into two parts, of which one was given the standard hot‐water treatment and the other was hot‐water treated with the addition of 0.5% formalin to the water. Some stocks were lifted the following season and the treatment was repeated. With most stocks a single application of formalin was sufficient to reduce the amount of disease to negligible proportions, but with one heavily infected stock a second treatment was necess