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.
Biomimetic architecture
The Qatar Cacti Building designed by Bangkok-based Aesthetics Architects for the Minister of Municipal Affairs and Agriculture is a projected building that uses the cactus's relationship to its environment as a model for building in the desert. The functional processes silently at work are inspired by the way cacti sustain themselves in a dry, scorching climate. Sun shades on the windows open and close in response to heat, just as the cactus undergoes transpiration at night rather than during the day to retain water. The project reaches out to the ecosystem level in its adjoining botanical dome whose wastewater management system follows processes that conserve water and has minimum waste outputs. Incorporating living organisms into the breakdown stage of the wastewater minimizes the amount of external energy resources needed to fulfill this task. The dome would create a climate and air controlled space that can be used for the cultivation of a food source for employees.