Encountering small red spiders in Washington state is a common occurrence, particularly during the warmer months and the transition into fall. These arachnids, often no larger than a pinhead, can appear suddenly on sidewalks, decks, and even inside homes, prompting questions about their identity and origin. While the term "red spider" is frequently used to describe a variety of tiny red arthropods, the specific species most commonly observed in this region is the spider mite.
Identifying the Red Spider Mite
The creature typically referred to as a red spider in Washington is almost always the twospotted spider mite. Despite its name, this pest is not an insect but a member of the arachnid class, closely related to spiders and ticks. The name is somewhat misleading, as these pests are not always red; they can range in color from pale yellow to deep orange or red, especially as populations grow and conditions become hot and dry. Adult mites are incredibly small, measuring only about 1/50th of an inch, making them difficult to see with the naked eye. A key identifying characteristic is the presence of two distinct dark spots on their translucent bodies, which gives them their common name.
Lifecycle and Habitat
Understanding the lifecycle of the twospotted spider mite is crucial for effective control. These pests thrive in hot, dry conditions, which is why infestations often spike during the peak of summer. A single female can lay hundreds of eggs on the undersides of leaves, and in the warm weather common to Washington summers, a new generation can hatch and reach maturity in less than a week. They feed by piercing plant cells and sucking out the contents, which depletes the plant’s chlorophyll and results in a characteristic stippling or bronzing of the leaves. Webs are a telltale sign of a heavy infestation; you might notice fine, silken webbing connecting leaves and stems, particularly on plants like roses, strawberries, and junipers.
Impact on Plants and Gardens
Signs of Infestation
Homeowners and gardeners in Washington should be vigilant for specific signs of spider mite damage. The most obvious indicator is the stippling pattern on leaves, where tiny yellow or white dots appear as the plant cells are destroyed. As the damage progresses, the leaves may curl, turn brown, and eventually drop off the plant. Webbing is a clear sign of an advanced infestation. While spider mites feed on a wide variety of plants, they show a particular preference for broadleaf evergreens like juniper and arborvitae, as well as fruit trees and vegetable crops.
Management Strategies
Effective management of red spiders requires a proactive and multi-pronged approach. The first line of defense is cultural control: maintaining plant health through proper watering and mulching makes them less susceptible to attack. Since spider mites thrive in dust, occasionally rinsing plants with a strong jet of water can dislodge populations. For biological control, introducing predatory mites like *Phytoseiulus persimilis* is highly effective, as these beneficial insects specifically target pest mites without harming plants. When chemical intervention is necessary, miticides specifically labeled for spider mite control should be used, ensuring thorough coverage of the undersides of leaves.
Distinguishing from Other Red Arachnids
It is important to differentiate the spider mite from other red-bodied arachnids that may be found in Washington. For instance, the red velvet mite is a larger, soft-bodied mite that is often seen crawling on soil during rainy seasons; while they look similar, they are not pests and actually feed on smaller insects and mites. Similarly, chiggers—though often called "harvest mites"—are related to spiders but are distinct pests that cause itchy bites. True spiders, while they may be red, are usually visible to the naked eye and do not produce the fine webbing or stippling damage characteristic of an outbreak.
