Editing Cactus (section)

===Pests and diseases===

A range of pests attack cacti in cultivation. Those that feed on sap include [[mealybug]]s, living on both stems and roots; [[scale insect]]s, generally only found on stems; [[whitefly|whiteflies]], which are said to be an "infrequent" pest of cacti;{{sfnp|ps=none|Innes|1995|p=32}} [[Tetranychus urticae|red spider mites]], which are very small but can occur in large numbers, constructing a fine web around themselves and badly marking the cactus via their sap sucking, even if they do not kill it; and [[thrips]], which particularly attack flowers. Some of these pests are [[Insecticide resistance|resistant to many insecticides]], although there are [[biological control]]s available. Roots of cacti can be eaten by the larvae of [[Sciaridae|sciarid flies]] and [[fungus gnat]]s. [[Slug]]s and [[snail]]s also eat cacti.{{sfnp|ps=none|Innes|1995|pp=31–32}}{{sfnp|ps=none|Brown|2001|pp=90–91}}

Fungi, bacteria and viruses attack cacti, the first two particularly when plants are over-watered. [[Fusarium oxysporum|Fusarium rot]] can gain entry through a wound and cause rotting accompanied by red-violet mold. "''Helminosporium'' rot" is caused by ''[[Bipolaris cactivora]]'' ({{abbr|syn.|synonym}} ''Helminosporium cactivorum''<ref name=SpeciesFungorum/>); ''Phytophthora'' species also cause similar rotting in cacti. [[Fungicides]] may be of limited value in combating these diseases.{{sfnp|ps=none|Hecht|1994|p=152}} 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).<ref name=DuarAlexRivaHara08/> However, in an ''Agave'' species, cactus virus X has been shown to reduce growth, particularly when the roots are dry.<ref name=IzagMaryOlivOrop95/> There are no treatments for viral diseases.{{sfnp|ps=none|Hecht|1994|p=152}}