Controlling spider mites organically provides the best long-term solution for infestations. Spider mites are resistant to some pesticides, and spraying with pesticides kills many spider mite predators. Wildlife-friendly gardens encourage spider mite predators, such as lacewing larvae and lady bugs. Signs of a spider mite infestation include yellow speckling on foliage and fine webbing on the undersides of leaves. Spider mites are very small. You may see them if you hold a piece of white paper under a spider mite-infested leaf, tap the leaf and the mites fall on the paper; they may crawl after falling onto the paper.
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Watering plants and spraying their leaves with water controls some spider mite infestations. Spider mites thrive in warm, dry conditions, and drought-stressed plants are vulnerable to their attack.
Water spider mite-infested plants according to their water needs. If you're unsure how much water the plants need, then water them when their soil surface is dry. Apply enough water to moisten the soil to the depth of the plants' root balls.
Spray plants with a strong jet of water from a garden hose to remove and destroy spider mites, and disrupt their webbing, delaying egg-laying. Spraying infested plants with water also removes dust. Dust prevents spider mites' predators from attacking the mites.
Insecticidal soap kills spider mites by preventing them from breathing. Commercial products are available, or you can make your own. Test insecticidal soap on a small area of a spider mite-infested plant, and wait 24 hours before spraying the whole plant with the product to ensure the insecticidal soap won't harm the plant.
Spray all parts of infested plants, including the undersides of leaves, with a ready-to-use insecticidal soap spray that you tested on the plants. Ensure the leaves get completely wet with the product. Spray the plants every week until the spider mite infestation is under control.
Make your own insecticidal soap by gently mixing 3 tablespoons of dish-washing soap with 1 gallon of water. Spray the plants with the mixture every five or six days for as long as necessary.
Indoor plants infested with spider mites can be treated with biological controls that contain predatory insects and mites. Spider mites have naturally occurring enemies, and you can buy some of them as commercial products to control spider mite infestations. These products work best on plants indoors, where the predators can't escape into the environment.
Phytoseiulus persimilis, a spider mite predator, is supplied in tubes filled with vermiculite granules. Use this biological control at temperatures between 57 and 86 degrees Fahrenheit. Sprinkle the vermiculite granules onto leaves halfway up the infested plants. If the granules won't stay on the leaves due to the leaves' shapes, then place the granules near the plants in small cones of paper. A tube containing 1,000 Phytoseiulus persimilis mites treats five or six plants.
Don't use pesticides and biological controls.
Treatments for Houseplants
Pruning and rinsing houseplants' leaves removes most spider mites from the plants. Biological controls also work in removing the pests from houseplants, but some people are not comfortable with introducing those biological controls' living organisms to a home.
Houseplants severely infested with spider mites should be thrown in the trash outside.
Prune leaves and stems of a lightly or moderately infested houseplant, and place the removed plant parts in the trash outdoors, or put them in plastic bags in the trash indoors. Wipe pruning shear blades with a cloth that was dipped in rubbing alcohol before and after pruning plants infested with spider mites.
Hold the houseplants over a sink or in a shower, and rinse their leaves with plenty of water. If a plant is too large to move easily and it has large leaves, then wipe the leaves with a soft, clean, damp cloth. Rinse or wipe both the upper and underside of houseplant leaves every one to two weeks as necessary. You can also treat spider mite-infested houseplants with an insecticidal soap spray in place of rinsing them with water.