Description of spider mites
Spider mites are tiny eight-legged arthropods related to the spiders and ticks. Like the spiders and the ticks mites have no antennae and no wings. They get from place to place by crawling rather than flying.
Damage caused by spider mites
Spider mites feed externally on the foliage of nearly all houseplants, though some, such as ivy and Norfolk Island pine seem particularly susceptible. Spider mites use a short, sharp beak to puncture the plant tissue and feed on the liquid within the cells. The piercing-sucking action and sap loss causes unique symptoms. In light infestations the foliage will appear to be speckled with very tiny tan spots. Heavy mite infestations can turn the foliage from greenish-yellow and eventually tan or brown. Heavily infested plants often drop their leaves. Examination of infested foliage may reveal very fine webbing produced by the mites.
Management of spider mites
The first step in spider mite control on houseplants is to inspect regularly, frequently and thoroughly for pests. Spider mites are tiny and may be difficult to see with the naked eye on the plant. A convenient detection technique is to hold a sheet of white paper under a stem and then shake or tap the stem against the paper. The mites, if present, will show up as tiny, slow-moving specks on the paper. Examine leaf undersides for crawling mites or their eggs that will look like small shiny spheres. The common houseplant spider mite is the twospotted spider mite, a yellowish green mite named for the two large dark spots, one on each side of the abdomen.
If mites are present, the next step is to determine the extent of the damage and the value of the plant. It is usually easier, quicker and more convenient to discard a small plant that is heavily infested than it is to return it to good health and appearance. If possible, prune heavily infested portions of larger plants before attempting mite control. Washing or syringing infested plant foliage may reduce light mite populations. Move plants outdoors or into the bathtub or shower and then use a forceful spray of water to dislodge mites from an infested plant.
Several miticides (pesticides that control mites) are available for houseplants. Check with your local nursery or garden center. Sprays available to homeowners usually contain insecticidal soap, horticulture oil, or pyrethrin. Read and follow all the label instructions. Thorough spraying, especially to the undersides of leaves is important for control. These sprays have no residual activity and only control mites and insects that are contacted directly and repeated applications will be needed. Keep plants watered and fertilized to promote health and vigor and to reduce the impact of mite feeding.
Do you live in Iowa and have an insect you would like identified?
The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them. Please see our website for current forms, fees, and instructions on preserving and mailing insects.
Contact information for each states diagnostic laboratory for U.S. residents. If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.