Spider Mites in Cacti

The Facts

• Spider mites drain nutrients from the cacti they inhabit by digging through the skin and draining sap. This leaves the cactus open to infection from diseases, fungi and bacteria, which can quickly kill it. Even where an infestation is light, the spider mites will permanently discolor the cactus wherever they damage the surface. If a cactus becomes infected with spider mites, early treatment is the best way to ensure its survival.

Identification

• The first sign of a spider mite infestation is often the white-colored webs they weave on the surface of the cactus. Yellow spots that turn brown over time will also develop on the surface of the cactus. These are where the mites attack the surface in order to gain access to the sap beneath. Where a heavy infestation occurs, the cactus will become discolored; taking on a bronze or greyish hue.

Prevention / Solution

• By the time you see the symptoms of an infestation, general precautionary measures, such as regularly misting the cactus with water, will not work. Once an infestation has taken hold, consider using a miticide on the cactus, as this will kill the mites. Insecticides will not work on a spider mite infestation as they are designed to combat a different kind of creature.

Warning

• Not all webs you see on a cactus are due to spider mites. A cactus can play host to a common household spider without harm, but the webs from a normal spider are very different from those of a spider mite. Spider mites leave thin, wispy webs on the leaves and needles of a cactus, while household spiders have a thicker, more patterned web.