Many of us enjoy a family picnic in the garden on a hot summer day, but none more so than a highly fertile colony of the two-spotted spider mite. Spider mites, or in their Latin guise, Tetranychus urticae, are a broad-spectrum pest that attacks greenhouse crops, strawberries, garden vegetables, and tropical house and landscape plants.
Spider mite damage initially appears as tiny white speckles visible on the topside of leaves. A little spot here, a little spot there—the damage gets missed as the flecks appear so insignificant. Under the right conditions, however, this damage can explode into something unmanageable.
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Spider mites are a member of the arachnid family and share the characteristic web-spinning abilities of traditional spiders. Unlike their cousins though, their webs are super fine and spread densely over leaves and stem without the classical geometric form. Upon close inspection of spider mite webs, you’ll discover not only adults moving back and forth, but multiple generations using the web’s protection to carry out their business. If your damage has already reached this state, you have a lot of catching up to do.
Identifying Spider Mites
Many species of mites can live on plants. Spider mites are small—so small you’ll need a 10x hand lens to identify them accurately. In fact, it’s more likely you’ll find the damage before the mite by randomly examining leaves. And this is wise—since if you detect them early, mites can be easily controlled. The mites themselves are oval in shape, slightly bristled, and pale green as juveniles with distinct dark green spots as they mature. These green dots are actually the contents of their gut and what gives the two-spotted spider mite its name.
Spider mites feed through a piercing, sucking action, which leaves a white pinprick mark. For individual plants, the first indication of infestation is a collection of these marks in an area the size of a dime. It may take some thorough hunting, but with practice, you can spot damage a good distance away. As the population increases, the feeding areas become larger, eventually yellowing the whole leaf and causing it to drop. Spider mites move from bottom to top, so it’s likely you’ll see the first of the damage on the plant’s lower growth, with leaves becoming more spotted as the population grows and the mites move up the plant. In severe situations, entire plants will become yellow and collapse.
Spider Mite Lifecycle
The lifecycle of the spider mite is dependent on their environment. Under ideal conditions of high heat (80 degrees F) and low humidity (less than 50%), the spider mite can complete development from egg to adult in just 5-7 days. These peak times generally occur between June-Sept. Under more average conditions of spring and fall, a lifecycle will take up to 19 days. If…