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.
Eucalyptus camaldulensis
Regulation causes flooding to be decreased during the winter and spring months, and water more consistently flows during the summer and autumn months. Since the river red gum disperses its seed during spring, regulating the water may affect the species' ability to disperse using water as a dispersing agent, especially in floodplain red gum forests. Natural water run-off can also be affected, leaving some trees permanently flooded due to the build-up of water behind dams, or the permanent water flow. Neither can seeds germinate in constantly flooded areas.