What Are Spider Mites and How Do You Get Rid of Them?

Even the most green-thumbed gardener isn’t immune to experiencing a spider mite infestation on their plants—something Nicole Sanchez, Associate Professor of Horticulture at Oregon State University, can confirm. She had her kids watering her greenhouse plants for five days while she was away for work. “I remember thinking, ‘It looks like I might have some spider mites. I’ll need to remember to check into that.'” When she got back, their numbers had exploded.

While these tiny garden pests can cause extensive damage left unchecked, don’t panic if you spot them on your favorite flowers. I spoke with experts who explained how to prevent their numbers from skyrocketing with simple control strategies and sensible plant care.

What Are Spider Mites?

Spider mites are arachnids in the Tetranychidae family. They’re closely related to spiders, scorpions and ticks rather than insects. While there are hundreds of spider mite species, the one you most commonly see on plants is the two-spotted spider mite (Tetranychus urticae).

What do spider mites eat?

Unsurprisingly, spider mites feast on plants. “They’re most attracted to younger plant material and softer leaves,” Sanchez says.

What are spider mites attracted to?

Spider mites thrive in hot, dry conditions and are drawn to drought-stressed plants. “Plants with excess or high nitrogen content also tend to be more attractive,” Entomologist Zach Schumm says. Rainy, cool weather and reduced fresh, leafy plant growth result in dwindling spider mite numbers.

What damage do spider mites inflict on plants?

Certified Horticulturist Leslie Halleck explains that spider mite infestations can cause significant damage if left unchecked, especially for young and small plants. As they pierce plant tissue and suck out sap, spider mites drain plants of color, energy, and chlorophyll.

“This can severely stress or stunt plants and even eventually kill them,” Halleck says. “Spider mites can also quickly spread to your other garden plants and houseplants.” Sanchez says they can also adversely affect your vegetable harvest yields and palatability.

Why are they called spider mites if they’re not spiders?

Spider mites are named after spiders because of the fine webbing they produce and for being part of the arachnid family of invertebrates.

How to Identify Spider Mites

Speedy spider mite identification helps prevent an infestation from causing problematic plant damage.

What do spider mites look like?

Sanchez says you can make out moving spider mites with the naked eye, but they’re about the size of a period at the end of a sentence, so you’re not likely to see any identifying features.

Under a magnifying glass, you’ll see adults have an oval body, four pairs of legs and no antennae. The common two-spotted spider mite has two dark spots on its back.

Signs of spider mites

Initial spider mite damage can be attributed to various things, so it pays to be vigilant. According to Sanchez, often, people don’t realize their plants have an infestation until they see the thread-like webbing. Some other signs of spider mites include:

• Visible moving dots on foliage (especially the undersides).

• Distortion of new leaves (cupping and curling) and blooms.

• Yellow or whitish chlorotic spots on leaves.

• Leaves take on a bronze coloring and then drop after extensive feeding.

Are Spider Mites Dangerous?

Spider mites aren’t dangerous for humans or pets, only plants.

Do spider mites bite?

Spider mites bite holes in leaves to suck out the sap, but, unlike some mite species, they don’t bite people or pets.

Are spider mites poisonous?

Spider mites aren’t poisonous to people or pets — only plants.

How To Get Rid of Spider Mites

You can use several simple methods to get rid of spider mites.

Spray with water

A targeted heavy stream of water is the simplest first line of defense to eliminate spider mites. “The force of the water can dislodge and kill spider mites,” Halleck says. Focus on the underside of the leaves, carefully direct the stream at delicate foliage, and be aware that this method won’t work for controlling large infestations.

Apply soapy water

Sanchez recommends applying a spray of soapy water next. This relies on contact with the spider mites to suffocate them, so thoroughly cover the leaves’ undersides. There’s no residual effect once the solution dries, so reapplying a few times is necessary to control infestations.

It’s best to avoid using this solution when it’s intensely hot outside, as the soap can bleach delicate new leaves.

Apply insecticide

If the strategies above aren’t working, consider applying a low-toxicity insecticidal soap or horticultural oil. Again, good coverage and repeat application are essential, and Sanchez says the product should be labeled as a miticide to ensure effectiveness.

Schumm suggests only using this method when absolutely necessary. “Natural enemies are already working on managing their populations, and insecticides can harm these natural enemies,” he says. Sanchez explains this can result in a “mite flare,” where spider mite numbers intensify due to having fewer predators.

Sanchez cautions against using a product like neem oil during the hottest part of the day or on plant leaves with a waxy cuticle (such as Jade plants or citrus leaves), as this can cause damage. She also says that oft-touted diatomaceous earth is unlikely to be effective. It relies on contact to kill the mites, and it will be difficult to get this powder to adhere to the underside of the leaves they crawl on.

When to call a pro

Having to call a pro to control spider mites is rare. However, if you have large ornamental landscapes or highly prized plants, they can apply the best pesticides to purge populations rapidly.

How To Prevent Spider Mites

Spider mite prevention involves minimizing plant stress and promoting an environment these pests don’t like. Halleck recommends maintaining even soil moisture. “Infestations are more common during very dry conditions (and low humidity) when plants are water-stressed,” she says. A plant humidifier can help in indoor settings with dry air from HVAC systems. Halleck also recommends diverse native planting to promote more predatory insects for natural control.

Frequently Asked Questions

Do spider mites live in soil?

“Spider mites may lay eggs in soil later in the season for overwintering,” Sanchez says. However, they mostly live on leaves, so repotting your plant isn’t a control strategy.

What eats spider mites?

Some spider mite predators include minute pirate bugs, big-eyed bugs, and lace­wing larvae. While it’s possible to purchase predatory mites for spider mite control, Sanchez doesn’t generally recommend this for home gardens. Finding a suitable species for your crop, climate and landscape size is challenging.

About the Experts

• Leslie Halleck is a Certified Professional Horticulturist, UCLA Extension Horticulture Instructor and author; email interview, Jul. 19, 2024.
• Nicole Sanchez is an Associate Professor of Practice in the Department of Horticulture at Oregon State University; video interview, Jul. 18, 2024.
• Zach Schumm has a master’s degree in Ecology (Entomology) and is an Insect Diagnostician at Iowa State University; email interview, Jul. 15, 2024.