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How to get rid of red spider mites in your garden

It doesn’t matter if you’re a novice or a professional gardener, some garden pests bring all levels of gardeners together because they cause damage in a diversity of growing environments. The red spider mite is one such creature. Houseplants, vegetable gardens, fruit trees, and landscape plants are all susceptible to infestations when conditions are right. If you care for plants, you will probably deal with these bugs sooner or later. 

close up of a red spider mite
Egor Kamelev/Pexels

What is a red spider mite?

“Red spider mite,” or simply “spider mite,” is a common name given to the Tetranychidae family of arachnids. This family includes about 1,200 different species of tiny sap suckers. They are related to, but separate from, spiders, ticks, and scorpions. They have eight legs, an oval body, and have the ability to make silk webbing. They vary in color from green or yellow, to red, to reddish brown, to almost black, and may feature spots or other markings. They do not have wings or antennae. Adults are only about the size of the period at the end of this sentence.

Each spider mite species feeds on different host plants and is active in its preferred climate conditions. Two of the most common species, both with broad appetites, are the Two-Spotted Spider Mite, and the Red Southern Mite. The Two-Spotted is found on a wide range of deciduous ornamental trees, shrubs, flowers, fruits, and other crops during hot summer weather. The Red Southern Mite attacks broadleaf evergreens like hollies, azaleas, viburnum, and rhododendron, along with roses and some other deciduous shrubs in cool spring and fall temperatures.

These arachnids have a five-stage life cycle that includes an egg stage, larval stage, two nymphal stages, and the adult stage. Immature mites resemble adults, but smaller. In ideal conditions, the transformation from egg to adult takes about a week. Adult females may live for several weeks, laying dozens of eggs during their lifespan. Overlapping generations of reproducing adults can cause a population explosion and serious plant damage.

spider mites on a tomato leaf

Signs of damage

Piercing mouthparts, made to puncture the leaf surface from below, allow spider mites to extract the fluids from individual plant cells. This causes the leaf to exhibit a stippled appearance, as if it has been dusted or sprayed with pale paint droplets where the contents were removed. Heavy infestations cause yellowing or bronzing of the leaves, along with early leaf drop resembling drought stress. Damage is most evident on the upper leaf surface. Affected plants may be stunted or even killed. 

In addition to the stippled leaf pattern, look for webbing. Most spider mites cover leaves, stems, and flowers with very fine silk. The mites use the silk strands to move from leaf to leaf, and plant to plant, with help from the wind. As an added bonus, abundant silk webbing shields them from predators and pesticides. Early in an infestation, the webbing may be found only on lower leaf surfaces and may be difficult to see. Spray a fine mist of water on suspect leaves to make webbing more easily visible.

Infestation causes

When environmental conditions are right, spider mites actively seek new feeding locations. On dry, breezy days, they can spin long strands of silk and move from leaf to leaf or plant to plant. They can also hitch a ride on birds and other animals, and even on gardeners and their tools. Sometimes they come into the garden on newly acquired plants, so it’s a good idea to quarantine, observe, and — if needed — treat every plant before exposing it to the rest of your garden.

Spider mites spread readily in arid, even dusty conditions, infesting plants that suffer from drought stress. They also find a welcome environment in landscape beds with drip irrigation or hydroponic setups where plants remain succulent and foliage is rarely wet.

A person with green and white gloves sprays a pest control solution from a yellow spray bottle onto some roses

How to get rid of red spider mites

Mites have a host of natural predators, including ladybugs, lacewings, and predatory mites. Where their populations are robust, they keep the pests in check. Avoid excessive use of broad spectrum insecticides that harm these beneficial species.

Before treating for an infestation, first confirm that the problem is spider mites. Tap an affected leaf or branch on a sheet of white paper. Any mites that drop will be visible in greater detail with the help of a magnifying glass. If you’re sure you have a mite problem, then it’s time to consider your options.

On a single houseplant, or a small portion of an individual landscape plant, you could wipe down the plant with rubbing alcohol. Use a cotton ball to methodically clean the upper and lower surfaces of each leaf and along the stems. Then wait a few hours and hose down the plant. Monitor and repeat the process in a week or two if the problem persists and again as needed until the mites stop coming back. 

Popular low-toxicity mite killers kill spider mites through physical rather than chemical action. Although they do not kill as quickly as chemical miticides, they are equally as effective when used as directed. Plus, unlike with chemicals, mites do not develop resistance to these products.

Oil-based miticides, like Natria neem oil, smother eggs and disrupt the breathing of adults. Garden Safe Insecticidal Soap degrades the soft-bodied mite’s protective outer layer and dries it out. Harris Diatomaceous Earth powder particles cause the soft-bodied mites to dehydrate. This package includes a duster that directs the application where you need it.

It helps to blast the leaves with a strong jet of water to dislodge the webbing and some of the adults before treating with these topical treatments. Then coat the entire plant with the product, paying special attention to the lower leaf surfaces and stems. Follow up with a second treatment a week later. Then monitor weekly and treat again as needed.

When the weather turns dry, occasional spider mite outbreaks are to be expected. Strong, healthy plants are able to resist them, especially when they are supported by a host of natural predators. By maintaining a robust garden ecosystem, you will avoid major problems. But, when the occasional big infestation does happen, know that there are effective treatments that will help you save your plants without polluting the environment.

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