Stem Rot (fungus – Coniothyrium euphorbiae): A disease of Euphorbia lactea, especially when grown in greenhouses. The disease begins on the upper end of the branch and moves downward. Rotted areas are dark colored and soft. Once a branch is attacked it usually dies. The disease resembles a bacterial decay, but no foul odor is present. Black fruiting bodies of the fungus can be seen in the infected areas. The fungus becomes established in greenhouses and is spread by splashing water. Damaged or wounded plant are quickly infected. Control by eliminating diseased plants and water without splashing.