Cactus
Fungi, bacteria and viruses attack cacti, the first two particularly when plants are over-watered. Fusarium rot can gain entry through a wound and cause rotting accompanied by red-violet mold. ""Helminosporium" rot" is caused by "Bipolaris cactivora" ( "Helminosporium cactivorum"); "Phytophthora" species also cause similar rotting in cacti. Fungicides may be of limited value in combating these diseases. Several viruses have been found in cacti, including cactus virus X. These appear to cause only limited visible symptoms, such as chlorotic (pale green) spots and mosaic effects (streaks and patches of paler color). However, in an "Agave" species, cactus virus X has been shown to reduce growth, particularly when the roots are dry. There are no treatments for virus diseases.
Disocactus × hybridus
Disocactus" × "hybridus is a hybrid between "Disocactus phyllanthoides" and "Disocactus speciosus". It is perhaps the most commonly grown orchid cactus and seems to survive and flower under most conditions. It has a very complex taxonomic history and has been mistaken for "Disocactus ackermannii" for a long time. The name "Cactus jenkinsonii" McIntosh (1829) might be an older name, but there is no combination under "Disocactus".