Severe infestation of spider mites will eventually kill the leaves on tomato plants, reducing the vigor of the plant and the number and quality of fruit produced. Can you identify a spider mite on your tomato plant?

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Spider Mites on Tomato

Spider mites are attracted to a variety of plants, but, in Kansas, during the summer, they cause more problems for tomato plants, a Kansas State University horticulturist said.

"The tiny insects feed on the underside of the plant leaves and suck the juices out the plant, causing the leaves to turn yellow and ultimately die," said Rebecca McMahon, Kansas State University Research and Extension horticulture agent in Sedgwick County, Kan. "An infestation can reduce the vigor of the plant and the number - and quality - of fruit produced."

Gardeners will be able to identify spider mites on tomato and other plants by a characteristic stippling on the leaves - it almost looks like someone took a paint brush and flung it at the plant, leaving tiny pale yellow or white specks on the leaves, McMahon said.

To confirm a spider mite infestation, choose a leaf that has the characteristic stippling pattern and place it over a white or light-colored piece of paper. Tap the leaf gently, and, after a few taps, remove the paper. If, in a few seconds, tiny black or red specks on the paper begin crawling around, you´ll know that you have spider mites.

"Spider mites are one of the most difficult insect pests to control," said McMahon, who explained that there isn´t a good insecticide that will kill them.

Extension horticulturists currently recommend aiming a hard stream of water at infested plants to knock spider mites off the plants. Other options include insecticidal soaps, horticultural oils, or neem oil.

"To be effective, such products will need to come in contact with the spider mite or spider mite egg," McMahon said. "Spraying the undersides of the leaves where most spider mites eat and live is recommended. When spider mites are evident, spraying once a week to kill young mites as they hatch also is recommended."

This feature story prepared with Rebecca McMahon, Kansas State University Research and Extension Horticulture Agent, Sedgwick County. For more information, visit your local county extension office or visit our website at

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