Drechslera cactivora is the fungus responsible for stem rot and leaf shattering on holiday cactus. Dark, water-soaked, mushy lesions appear both above and below the soil line. Lesions develop a dark, felty appearance due to dense sporulation of the pathogen. Even very small lesions can result in cladophyll abscission (leaf drop). The disease has been reported on cactus genera including Cereus, Echinopsis, Hatiora, Schlumbergera, and Mammilliaria. Infected plants should be discarded. Growth media should be steam pasteurized before use. Start with clean pots, tools, and flats. Chlorothalonil is registered for use on holiday cactus. Always check labels for host appropriateness and test for phytotoxicity on a small group before applying to the entire crop.
