Diseases

The most common diseases of Schlumbergera and Rhipsalidopsis are caused by fungi. Bacterial infections are rare. Viral infections are usually not destructive but weaken the plants and lead to unattractive spotting. More recently, mites of the genus Brevipalpus have been identified as important destructive pathogens. The most important fungal pathogen for Schlumbergera and Rhipsalidopsis is Fusarium oxysporum, which occurs worldwide in soil in over 100 different forms and shapes. The pathogens attack the roots, the stems and finally the phylloclades with soft, and red basal stem canker. Infections by Pythium species and Phytophthora species especially P. nicotianae, lead to clinical pictures, which are hardly distinguishable from one another. In contrast bipolaris blight caused by Bipolaris cactivora (formerly Drechslera cactivora), which could lead to smudged, round, black sunken lesions on phylloclades, which then rot and fall off the stems. Fungal infestation is generally promoted by high soil humidity and poor ventilation associated with higher temperatures of more than 28 °C (82 °F).

Infested plants should be destroyed. When treating with fungicides, rapid development of resistance must be taken into account and various preparations should be used alternately.

Bacterial infections by Pectobacterium (syn. Erwinia) carotovorum are rare. They are characterized by a soft rot generally starting at the soil line, which becomes mushy red. Treatment is not possible. The same applies to virus infections, which usually do not destroy the plants.

Since the 1990s Schlumbergera in North America and Europe have mainly suffered from Tospoviruses (Tomato Spotted Wilt Virus, TSWV and Impatiens Necrotic Spot Virus INSV of the family Bunyaviridae), which are transmitted as vectors by various thrips species. The infection is manifested in particular by sunken chlorotic lesions, chlorosis, ring spots and necrosis. A discoloration of the flowers has also been observed in Schlumbergera orssichiana. Control of biting and sucking insects and mites as well as hygiene when making cuttings (careful twisting of phylloclades or use of heat-sterilized knives) are the only possibilities to avoid virus distribution.

Schlumbergera and Rhipsalidopsis can also be asymptomatically infected!

Mites of the genus Brevipalpus, especially B. russulus, vernacularly named “flat mites” or “false spider mites” and not to be confused with the common spider mites (genus Tetranychus) are little noticed, but obviously widespread. In contrast to the latter, Brevipalpus species do not produce webs. The damages are varied and include chlorosis, sometimes accompanied by reddish spots or discolorations, soft rot and falling apart of the phylloclades. In addition, these pests are important vectors of plant viruses.

As in other cactus groups plants can often be attacked by mealy bugs. Spider mites on the other hand are of little importance.