Growers should be aware that STS is not registered for use on holiday cactus. Holiday cactus is subject to several diseases. Fusarium oxysporum is a fungus that causes root or stem rots. Infected segments produce reddish-orange sunken spots and then abscise. Orange spores develop in the lesions and are spread easily by water or air.
Stems topple over when the basal segment becomes infected.
Phytophthora parasitica and Pythium aphanidermatum are fungi that also incite root or stem rots. Phytophthora root and stem rot is characterized by necrotic stem lesions with faded reddish borders, grey-green discoloration of the stems, and segment abscission. Pythium root and stem rot is similar to the former disease, except that segment abscission is rare. Black spores develop in the lesions, giving them a fuzzy appearance. Infected segments commonly abscise.