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High Plains Journal Article: Spider mite control

Spider mite control
By Charles Lillard, Oklahoma County Extension Master Gardener

This article was taken directly from the High Plains Journal, July 29, 2019 Edition.

As days get hotter and drier, the population of spider mites increases. The damage caused by these creatures also increases. These small 8-legged animals suck plant juices, usually from the underside of leaves, causing the foliage to turn brown, lose their vigor, and eventually die. A fine silken web may be present. Under favorable conditions spider mites can multiply quickly and seriously threaten plant health. Heavily infested leaves and branches can become covered with an almost invisible webbing. To confirm a spider mite infestation one can hold a white sheet of paper under a branch and then tap the branch. If present, they will fall off and be seen as tiny specks crawling over the paper.

Be watching for these pests as the days get warmer as some mites thrive during the warm summer months. When the daily high-low temperature is 95 to 75 degrees, the number of spider mites on a plant can double in half the time it takes when the temperature is cooler. Large numbers increase when plants are sheltered and have a southern exposure. 

Recognizing spider mites
The twospotted spider mite (Tetranychus urticae) is only one-sixtieth of an inch long. During the warm months these mites are a whitish green with a dark colored area on each side. In the spring and fall they tend to become rusty-orange. They prefer to feed on young and tender leaves. They spend the winter in protected areas, such as weeds.

The European red mite (Panonychus ulmi) attacks flowering fruit trees and deciduous trees as well as shrubs in the rose family. They are brownish-red and elliptical in shape. They have four rows of spines that run down back its back. The eggs are bright red to orange and have a stalk so that they resemble a miniature onion set with the sprout attached. In the summer, eggs are laid on plant leaves. The European red mite spends the winter in the egg stage.

Some spider mites such as the Honeylocust spider mite (Platytechtranychus multidigtali) are specific to only one type of plant. The Honeylocust spider mite is greenish in the summer then turns reddish in fall. These mites spend their winter as adults in leaf bud scales and bark cervices.

The Oak ret mite infests the upper leaf surfaces of oak trees and is most predominant on the lower branches. In the summer, red barrel shaped eggs are laid on the tops of leaves. The eggs remain dormant until spring.

Controlling spider mites
Spider mites can threaten the health or appearance of your plants. Therefore, it is important to balance cultural, biological and chemical control methods all season. Inspect your plants once every two weeks for spider mites. You may use the sheet of paper under the branch method of detecting. Learn to recognize the early feeding symptoms of leaf stripping and bronzing. When an average of two-dozen mites fall from a branch each time you strike the branch, consider applying a pesticide. Spider mites thrive on plants that are under stress. Keeping plants watered and having adequate light will limit spider mite damage. Do not over or under fertilize.

This article was taken directly from the High Plains Journal, July 29, 2019 Edition.