Spider Mites

Though many people think of spider mites as insects, they are actually arachnids that are very close to spiders. Their name does not come from this likeness however, it comes from the fact that these creatures spin silky webs in order to lay and hatch their eggs. Spider mites are part of the Tetranychidae family, a family which contains approximately 1,600 different species. They are very invasive due to the fact that they will feed on hundreds of different types of plants and foliage.

The most common site of spider mite infestation is on the undersides of plant leaves. And because these creatures are very small – less than 1 mm in most cases – they are very hard to see with the naked eye. When they are seen, they are often mistaken for specs of dirt or rust. Spider mites may also vary in color, though most of those seen in North America will be rust-colored.

How Spider Mites Cause Damage

Spider mites have a very specialized mouth construction which is perfect for penetrating the cells of plant leaves. They feed by puncturing the plant and then sucking the sap out of the cells. This process leads to a yellowish or bronze stain on the surface of the leaf which, after enough punctures, will discolor the leaf to a point where it’s easily visible. Plants suffering from spider mite infestation tend to exhibit flecks and/or a bronze discoloration.

Environmental Variables

For spider mites to reach their maximum potential they require a warm and dry climate. It is for that reason that they are most pervasive in the U.S. in southwestern states like Arizona, Texas, and New Mexico. However, spider mites have no problem living in northern regions either. They are very adept at winter hibernation, finding a point of entry in to the bark of a tree where they will remain protected from severe weather.

Their affinity for dry and warm conditions also means that spider mites do very well indoors. They can travel into your home on clothing, shoes, garden tools, and any other number of things. Once inside your home, they will easily infest your ornamental plants if they are left unchecked.

Reproductive Cycle

One of the main reasons behind the invasive nature of spider mites lies in their reproductive cycle. Under optimal conditions an adult female can lay between 12 and 20 eggs per day. She will continue this on a daily basis for 3 to 4 weeks during her breeding season. Again, when the right conditions exist an egg can hatch in as little as 3 to 5 days. Once hatched, the young spider might only need 5 to 7 days to become fully mature. And with every fully mature female, new eggs will be laid.

Based on this knowledge, running the numbers shows just how quickly a small handful of spider mites can get out of control. In a four-week breeding cycle a single female can produce 400 offspring. Every female she produces will begin producing her own offspring within a week of her birth; she too can produce as many as 400 eggs. The cycle goes on to the extent that you could have thousands of spider mites in a very short amount of time.

Treatment Options

Options for treating spider mite infestations can be broken down into four main categories. Regardless of the treatment, early detection is key to managing infestation before it gets out of control. Below are the four categories and a brief description of each.

• Agricultural: Agricultural treatments begin with watering practices. Infested plants can be washed thoroughly with a moderate jet of water to remove all of the spider mites. Regardless of whether or not other treatments will be used, beginning by washing infested plants is generally accepted as a good idea. In terms of preventative measures, keeping plants properly watered is a good way to encourage spider mites to look elsewhere for their food.

• Biological: Biological methods of treatment usually consist of introducing natural predators into the environment. It may be that the use of pesticides has significantly damaged the population of the spider mites predators, thus allowing them to proliferate. But a reintroduction of natural predators, such as ladybugs, can help reduce the overall spider mite population.

• Organic: Organic treatments use all natural substances such as peppermint oil to interrupt the egg cycle of the spider mite. As a spider mite egg grows it begins to break open 2 to 3 days before the hatchling completely emerges. During that time, the use of organic substances can suffocate the young mites in the egg so that the hatching process is not completed. Many experts in the industry believe that interrupting the egg cycle is one of the best ways to control spider mites and there colonist.

• Chemical: Chemical treatments involve the use of pesticides and miticides to control spider mites. In most cases they are effective in killing spider mites on contact. They are also effective in preventing new infestations in the future, if continually used on a long-term basis. However, one of the downsides of the chemical method is that it also tends to kill other insects as well. This unintended consequence may result in a worse infestation if natural predators have been destroyed by the pesticide.