For Release July 24, 2001

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

I hate spider mites. They’re small, they reproduce quickly, they are hard to see, they’ll feed on almost anything, and they seem to show up when plants are already stressed by the weather. On top of that they are very hard to control. Many of our common insecticides won’t control them and may even make the problem worse. They can seemingly appear overnight and at times disappear just about as fast. If not noticed and treated in a timely fashion, they can kill almost any plant.

Spider mites are not a true insect. They have eight legs, so they are more closely related to such other disgusting things as ticks, spiders and chiggers. They have a piercing sucking mouthpart. They stick their little mouth into a leaf surface and start sucking the plant juices. As they feed, a toxin in their saliva works its way back into the leaf killing a small portion of the leaf. Spider mites prefer hot and dry weather, thriving in the sweltering heat.

There are several distinct species of mites that we often lump all together as spider mites. In the long run, it usually doesn’t matter what species we are dealing with. Already this year, I’ve seen spider mites feeding on over 15 lawn and garden plants and they are even starting to cause problems in some soybean fields.

Spider mites are very small. They are often smaller than the period at the end of this sentence. They prefer to feed on the undersides of leaves. When populations become quite large, they will create a fine silky web under the leaves and oft times through out the plant. Their damage is often seen before they are. Look for foliage starting to go yellowish or bronze colored, or just going off color. This is caused by the leaf tissue death from the toxin in their saliva.

If you turn these leaves over and get out a magnifying glass, you can usually see the dozens, if not hundreds, of tiny little mites moving around on the leaf. An alternative to trying to see the mites with a magnifying glass, is to tap the leaf onto a piece of white paper. If there are mites, some of the will fall onto the sheet of paper. All of a sudden you will notice that there are a bunch of little specks on the paper and they are moving!

Spider mites, like all insect pests, are most damaging on evergreens, because they can not regenerate leaf tissue as quickly or easily as deciduous plants. But they can kill anything they feed on. They will feed on flowers and garden crops as well as trees and shrubs.

Since spider mite problems can develop so rapidly, it doesn’t do any good to treat until you know that you have spider mites. The best product for the home gardener to use for mite control is Kelthane. This is a product specifically labeled for mite control. You can also use diazinon or malathion, but they will not work as well. DO NOT use Sevin. Sevin kills natural predators of spider mites, but doesn’t kill the mites. Read the label carefully as there are a few plants that you should not spray with Kelthane.

Since the mites like to feed on the undersides of the leaves you really need to try to get the spray up under the leaves. You will also need to retreat three to four times at roughly one week intervals. Read the label for specific recommendations. A hose end sprayer is often the best sprayer to use.

Spider mites are small and nasty. If you don’t have them, don’t spray. If you do have them, treat quickly, while you still have something to treat!

-30-

Return to Agri-Views Home Page

Return to Ag Home Page