Spider Mites! How can something so small be so destructive? Gardens in our area are very susceptible to spider mites. Spider mites are also called web-spinning mites. They commonly feed on fruit trees, vines, berries, vegetables and ornamental plants. Spider mites look like tiny, moving dots, smaller than 1/20 of an inch. They live in colonies, mostly on the under-surfaces of leaves. Webbing is an easy way to distinguish them from other types of small insects, but you may not always see the webbing. These little buggers produce rapidly in hot weather in the months June through September. If temperatures and food supplies are favorable, a generation can be completed in less than a week! So you can see how they can get out of hand very quickly! They prefer hot, dusty, conditions. They will also attack plants that are under water stress. Wind is also another way spider mites disperse to other plants. When cooler weather hits mites will start to decline.
Spider Mites suck the life out of plants causing light stippling dots on the leaves. Most of the time you won’t even notice you have spider mites until the plant starts to decline. As feeding continues, leaves will sometimes take on a bronze color. Yellowing and leaf drop will follow. Damage will worsen if plants suffer water stress. Greenhouses, even though it’s a humid environment, can get overtaken quickly, especially on tomato plants.
Even though spider mites in small numbers won’t do to much damage, I still have to get a hold of them quickly. They seem to damage vegetable crops much quicker than ornamentals. Sprays of water will help keep the moisture level up by removing the dusty conditions they like. Don’t forget to spray the ground around the plant to. Insecticidal soaps are a safe way to eliminate these bad guys, but you have to get the underside of the leaves or they will just continues to reproduce. Don’t use insectididal soap on water stress plants or when tempertures are higher than 90 degrees or you can damage your plants. A second application may be needed. The chances of getting them all and their eggs can be rather hard the first go around.
Here is another reason to go organic! Spider mites frequently become a problem after applying insecticides. Outbreaks are commonly a result of of using carbaryl (Sevin) because it simulates mite reproduction. This product favors spider mites by increasing the level of nitrogen in leaves. Sounds rather odd, but I have seen it!