Spider mites are sap-sucking pests that damage indoor and outdoor plants, eventually killing them if left unchecked. Telltale signs of infestation include the appearance of bronze spots or speckling, leaf curling and, in some cases, silk webbing. Despite their nearly microscopic size, spider mites are classified as arachnids and are related to scorpions, daddy-longlegs and spiders.
Meet Your Mites
Red Spider Mites
Also known as the two-spotted spider mite (Tetranychus urticae), the red spider mite is the most common type of leaf-munching, web-spinning mite that affects houseplants, flowers and many kinds of vegetables, especially eggplant, beans, tomato, squash and cucumber. In fact, according to the University of Florida, this tiny mite has more than 200 species of plants on its menu.
Spruce Spider Mites
The spruce spider mite (Oligonychus ununguis) targets coniferous trees such as juniper, balsam fir, Fraser and, of course, spruce. In addition to occupying existing trees in your landscape, these mites sometimes tag along with nursery-purchased saplings. It’s also possible to invite them into your home if you bring a live tree indoors to decorate for the winter holidays.
Management Strategies for Outdoor Plants
Turn the hose on garden plants periodically. Not only do plants benefit from an extra drink of water, but the force of the stream helps to dislodge mites and their egg-laden webbing. This practice also helps to remove dust and other debris that might impede natural mite predators.
Introduce beneficial insects into your landscape. Spider mites have a lot of enemies, most notably the spider mite destroyer lady beetle (Stethorus picipes). As the common name implies, this bug, and its larvae, feed specifically on spider mites. Other predators include sixspotted thrips (Scolothrips sexmaculatus), lacewing larvae (Chrysopa spp.) and minute pirate bugs (Orius spp.). Predatory mites, such as the western predatory mite (Galendromus occidentalis), are often used in greenhouses to control red spider mites. You can purchase beneficial insects from some garden centers and various online sources.
Plant-based insecticidal sprays formulated as miticides, such as neem oil is safer on the environment that chemical-based pesticides. Neem oil helps reduce spider mites without harming plants or beneficial predatory insects. The product reduces feeding as it stops the spider mite's ability to take in food and also works as a repellent. Always wash your hands after using. To use:
- Use a ready-to-use neem oil spray. Test a small portion of the plant and wait 24 hours before spraying the entire plant to make sure foliage damage doesn't occur.
- Thoroughly spray all parts of the plant and both sides of leaves. This is important because direct contact is necessary to suffocate mites.
- Reapply every seven to 14 days until the infestation is under control. Note that it may be necessary to reapply more often if the infestation is very heavy or after periods of rain.
Management Strategies for Indoor Plants
Treat Plants with Water
You don’t want to bring predatory insects into your home or even spray organic insecticides indoors if you can help it, so cleansing with water is the best option for getting rid of spider mites on indoor plants. Either bring plants to the kitchen sink or to the shower and use the spray of water to displace mites and their eggs. Follow up by wiping off leaves with a soft cloth. Repeat this process every seven to 14 days until the infestation is under control.
Prune Infected Plants
Pinch off dead or decaying leaves with fingers, taking care not to touch or handle healthy parts in the process. Don’t toss these trimmings into the compost pile. Instead, bag and discard them. Similarly, if plants are so damaged from mites that they are beyond rescue, dispose of them accordingly.
Spider mites are hard to control especially when their populations are high and the plant is heavily infested. In some cases and with heavily infested house plants, tossing the plant is sometimes your only choice. Encase the discarded plant inside a plastic bag so the spider mites don't infest other plants.
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