Among the Pythium diseases, Pythium blight (a.k.a. ‘greasy spot’ or ‘cottony blight’) is the most straightforward to understand and control. Pythium aphanidermatum, and a few other species that cause blight, are most active under hot, wet conditions. Pythium blight is most feared because it can cause widespread plant death in 24-48 hours with little chance of recovery.