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.
Pollination
Rain pollination is used by a small percentage of plants. Heavy rain discourages insect pollination and damages unprotected flowers, but can itself disperse pollen of suitably adapted plants, such as "Ranunculus flammula", "Narthecium ossifragum", and "Caltha palustris". In these plants, excess rain drains allowing the floating pollen to come in contact with the stigma. In rain pollination in orchids, the rain allows for the anther cap to be removed, allowing for the pollen to be exposed. After exposure, raindrops causes the pollen to be shot upward, when the stipe pulls them back, and then fall into the cavity of the stigma. Thus, for the orchid "Acampe rigida", this allows the plant to self-pollinate, which is useful when biotic pollinators in the environment have decreased.