Spider mites are a common pest of houseplants. They prefer dry environments with an ambient temperature of 80 degrees F. Feeding damage results in chlorotic spots or a stippled appearance on plant leaves. Webbing may also be present. Luckily they are pretty easy to control.
The most common spider mite found on houseplants is the two spotted spider mite. The adult has eight legs with an oval shaped body and is approximately one fiftieth of an inch long. The body is commonly greenish or almost translucent although it may be brown to orange-red. It has two dark spots on its body that are easily viewed using a 10X to 15X magnifying lens. Spider mites are not insects. They are a type of arachnid and closely related to spiders and ticks.
If your houseplants are infested with spider mites consider moving them to a cooler room away from healthy plants. Make sure the soil is not overly saturated or dry. A good rule of thumb is to water your houseplants when the top half inch of soil is dry. Washing the foliage of infested plants in a sink or bathtub using one to two teaspoons of a mild dish-washing liquid soap added to one gallon of water will help keep the population in check. Repeat treatment as needed. Other control options include using horticultural oils or labeled insecticides.
If the infestation is severe with most of the plant being covered with spider mites the best control option is to discard the plant. Before removing, place a plastic bag over the plant to help prevent any spider mites from migrating to other houseplants. To prevent future infestations keep newly acquired houseplants in an isolated area, away from other houseplants for a few weeks. Use this time period to monitor the plants for any pest problems before placing them with the rest of your healthy plants.
If spider mites are bothering your houseplants or if you have other plant questions, please call me at the University of Minnesota Extension office, Clay County at 218-299-5020, 1-800-299-5020 or email me at nels1657@umn.edu. Check out our website at www.extension.umn.edu/county/clay/