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.
Ferocactus wislizeni
In adulthood, fishhook barrel cacti generally lean southward, toward the sun, earning them the nickname "compass barrel cactus." One theory about why this happens is, the afternoon sun is so intense it slows the growth on the exposed side, causing the plant to grow unevenly. Older barrels can lean so far they uproot themselves and fall over, especially after heavy rains when the soil is loose. Its life cycle is 50–100 years.