Spider Mites

Have you noticed fine webbing on your tomato plants recently? Are your leaves looking stippled (spotted white or yellow)? If so, you are like the many other gardeners experiencing spider mites in their garden.

Spider mites on lemon tree (Paramecium) CC BY-SA 3.0

Spider mites are very tiny. The females are only 1/20” and the males are even smaller! However, as spider mites colonize on a plant, you will see webbing, especially on the underside of the leaves. Spider mites can suck the life juices right out of your favorite heirloom tomato and these little buggers can complete an entire generation in less than a week! Unfortunately, drought-stressed plants are more susceptible to spider mite infestations.

Female spider mite Gilles San Martin CC BY-SA 2.0

One of the most common causes of spider mite infestations is the use of broad spectrum insecticides, which kill off beneficial predators along with the pests. The easiest (and least destructive) way to get rid of spider mites is to move the infested plant to a clear area of the yard and spray it off with the hose. Insecticidal soaps or horticultural oils can also be used, but watch out for applying them on sunny days. I recently learned the hard way that leaves will burn if insecticidal soap is left on the leaves during the heat of the day.

​If spraying your plants does not provide adequate control, you can purchase western predatory mites and Phytoseiulus (spider mite predators). Spider mites love dusty conditions, so you can make your yard less hospitable by giving plants an occasional light rinse.