GardenLine | Common Saskatchewan Pests | Spider Mites on House Plants

Spider mites are tiny arthropods that are more closely related to spiders and ticks than to insects. They have 8 legs as opposed to 6, which is the easiest way to differentiate them from insects. They attack a wide variety of plants indoors and outside, and can cause considerable damage. Not all mites however are pests. Several predatory mites are quite beneficial in that they keep a wide variety of insect pests under control.

Mites are often too small to be seen with naked eye. Tell-tale signs of a mite infestation are white speckling on leaves and webbing around leaves and stems. See the samples. Mites feed on plants by sucking the sap from the leaves. This type of feeding causes the leaves to have a mottled or speckled appearance. Note that other types of pests also suck sap from leaves and cause the same type of damage.

On houseplants, mite populations are fairly inactive during the cooler winter months. During the hot summer months, the populations can grow incredibly fast. Eggs laid on the leaves hatch to produce a new generation of mites every few weeks. Several generations can occur during the summer months. Mites multiply fastest under hot, dry conditions and on plants under stress.

Control: The first control is to ensure the plant receives a suitable growing environment: water, sunlight, fertilizer and soil. A healthy plant will tolerate mite infestations better than a weak plant.

Insecticidal Soaps can effectively reduce mite populations. You need to spray the plant thoroughly (top and bottom of the leaves) and often. One application every 5 to 7 days for 4 weeks is recommended, as this will catch the young as they hatch. Some gardeners recommend to thoroughly rinse the plant about 1 hour after spraying with the soap solution to prevent possible damage to the plant by the soap solution.

If the plant is heavily infested with mites, the best solution is to throw it out. If possible, take a cutting and start over again. As a last resort, pesticides can be used. A word of caution: insecticides are designed to kill insects, however mites are not insects, so most insecticides are not effective in controlling mites. Miticides are effective in controlling mites. Read the labels carefully.

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.