Spider Mites

Facts, Identification, & Control

SCIENTIFIC NAME

Family: Tetranychidae

WHAT ARE THEY

Mites are so small and prolific that mite infestations usually are not noticed until their populations are so large they cause damage to their host plants. Spider mites get their common name from the ability to produce silk webs much like spiders that are used to move around on the plant and to move from one plant to another.

IDENTIFICATION

There are more than 1,000 of species of spider mites, but the common characteristics of these mites are their very small size, approximately 1/50 of an inch, which is about the size of the period at the end of this sentence. They are oval-shaped and red, greenish and brownish colored. Spider mites do not have any wings or antennae but have eight legs in their adult stage. As one might expect, color varies not only by species of mite, but also by the mite’s developmental stage (see Life Cycle, below). Upon close examination of plants infested by spider mites, the amber-colored eggs, whitish colored cast skins and black specks of mite feces can be seen.

HABITAT

Spider mite habitat is quite variable and depends upon the mite species. However, most spider mites that are important pests live on household plants, landscape plants, farm crops and fruit trees that are found in both urban and agriculture environments. They are likely to be found feeding on the underside of plant leaves or other parts of the plant.

DIET

Mites feed by using their mouthparts to pierce plant leaves and suck out the fluids from individual plant cells. This causes the leaves to have a spotted appearance where the cellular contents have been removed. Prolonged, heavy feeding by spider mites cause yellowing of the leaves and premature leaf drop similar to a drought-stressed plant. Unless spider mites are controlled, their host plant may be stunted or even killed.

LIFE CYCLE

Spider mites go through four developmental stages- egg, larval, nymph and adult.  Mite larvae have six legs, while the nymph and adult stages have eight legs. The larvae and nymph mites resemble adults, except for the number of legs and being smaller in size. In the best of environmental conditions, spider mites will complete a life cycle in less than a week. Their short life cycle and the female’s capability to lay eggs over her lifetime cause rapid population increases and a lot of feeding damage to plants.

PREVENTION TIPS

The first step to prevent and control spider mites is to actually see mites on the plant. Key things to look for are the mites themselves, their webbing and damage to their host plants. Some tips to help manage spider mites on plants include:

  • If you suspect a plant has spider mites, vibrate the plant’s leaves and look for mites that drop from the plant onto a white piece of paper or cloth held under the plant. Spider mites often come indoors with plants that were set outside during the summer and on Christmas trees during the season. Therefore, it is recommended to use inspection methods before bringing any of these indoors to help prevent indoor spider mite problems. It is a good idea to inspect any new plants that are brought inside or set out as outdoor landscape plants.
  • Use a soft cloth to wash spider mites off of plants using a mixture of mild detergent solution – about ½ tablespoon of detergent in one gallon of water. Also, mites can be removed by washing them off the plant using a water spray. Depending upon the number of mites on the plant, it might be necessary to apply this removal technique several times.
  • Use insecticide formulations recommended by your local plant experts or university extension agent.