How to Get Rid of Spider Mites That Have Infested Your Garden or House Plants
If the leaves of your favorite plant are starting to turn yellow no matter how much sunlight or water you provide, it might not be your fault. The culprit could be spider mites, tiny pests that are known to wreak havoc on indoor and outdoor plants.
The almost-too-small-to-see spider mites on plants can reproduce quickly, leaving plants yellowed, wilting, and dying. “To the naked eye, spider mites look like tiny, moving dots,” according to the University of California’s Integrated Pest Management Program (UCIPM). “A small number of mites usually isn’t reason for concern, but very high populations—levels high enough to show visible damage to leaves—can damage plants, especially herbaceous ones.”
If you’re dealing with spider mites, don’t panic. They’re annoying, but can be managed and even removed completely with the right techniques. Here’s everything you need to know about spider mites, including how to get rid of them.
What are spider mites, exactly?
Spider mites are neither insects nor spiders, but they belong to the arachnid family. “The mites build colonies on the undersides of leaves and produce webbing over infested leave surfaces,” the University of Minnesota Extension (UME) reports—that’s how they got their name.
These mites multiply quickly in hot weather because they thrive in a warm, dusty environment. That’s why they become more common from June to September. With the right conditions, larvae hatch and reach development in as little as a week; their population can boom in just two weeks.
The mites feed by sucking the moisture out of plant leaves, causing damage and potentially death if the infestation spins out of control. The pests can be quite harmful to plants, especially if left untreated, but don’t pose any threat to people or structures—they don’t spread any diseases or burrow into wood.
How do spider mites get on indoor plants?
It’s unfortunately pretty easy to get spider mites on indoor plants. “Due to their small size, spider mites can move through minute openings, including screens,” says John Bell, board-certified entomologist with Ehrlich Pest Control.
Just like some spiders, “spider mites will spin a very fine web that will be picked up by the wind and carry them distances,” Bell says. (This is known as “ballooning,” if you want to get technical.)
How do spider mites get on outdoor plants?
Spider mites can infest indoor and outdoor plants, Bell points out. “They find their plant material the same way for both,” he says. Meaning, spider mites may balloon through the wind and just happen to land in your garden.
What are the signs of a spider mite infestation?
You might not be able to see the spider mites themselves, especially if you’re not looking closely. But they leave plenty of other evidence that should tip you off. The tops of leaves will start to exhibit stippling, or small white and yellow dots, that leave them looking mottled and discolored. Eventually, they might turn brown and fall off.
Another telltale sign is pale white webbing, which “cover[s] leaves, twigs, and fruit,” according to UCIPM. If you notice the protective webbing on any indoor or outdoor plants, you’re most likely dealing with spider mites.
“Due to their small size, it is difficult to see spider mites with your naked eye,” Bell says. His advice: Hold a white sheet of paper under a leaf you think might have spider mites and then tap the leaf. “If spider mites are present, they will fall onto the sheet of paper and look like small specs, which will start to move on the paper,” Bell says. “To confirm, press on the speck with your finger and slide. If a smudge mark is created, you have a spider mite problem.”
How to get rid of spider mites
As annoying as spider mites might be, you can eradicate them with a few simple measures. It’s important to take a close look at your plants regularly, especially if you’re living in a dry area. Spotting signs of an infestation ASAP will make it easier to get rid of.
✔️ Drown them out.
Because they love dusty, dry atmospheres, moisture becomes one of your best defenses. “Spider mites thrive on plants under stress,” UME reports. “Most plants should receive about one inch of water a week to avoid stress conditions.” Proper mulching also helps conserve moisture, keeping mites away or at manageable levels.
If the mites refuse to leave, you can also choose to remove them directly from affected plants. Give gardens and trees a strong spray with a hose to dislodge the mites and break up the webbing (which can prevent egg laying). This will also keep your plants dust-free.
✔️ Pay closer attention to house plants.
Removing spider mites from indoor plants can be especially tricky. It’s important to identify all infested plants, especially if they sit closely to one another, because you’ll want to treat them at the same time.
First, trim off any particularly rough-looking leaves (and unfortunately, you should get rid of heavily infested plants to try and save its neighbors). Leaves with tons of webbing should be thrown away, not composted. Then, like the method above, give them a generous spray in the sink or tub and clean larger leaves (paying extra attention to the underside) with a soft cloth. Continue to do this every week or every two weeks as needed.
✔️ Hit them with soapy water.
“The easiest way to treat small areas is to make your own miticide by placing one tablespoon of liquid soap into a gallon of water and placing it in a spray bottle,” Bell says. Then, spray the leaves of your plant with the solution and wipe them with a sponge or cloth. But, he points out, this “will need to be repeated every couple of days until spider mites are gone.”
✔️ Crank up the humidity.
Spider mites prefer dry conditions, Bell points out. “To help reduce the chances of getting spider mites, keep plant material dusted and keep the humidity high,” he says. If you happen to have your plants in a certain area of your home, it may be worth investing in a humidifier to keep the area a little more moist than the rest of your home.
✔️ Try pest killers.
Strangely enough, some common insecticides actually make it easier for spider mites to thrive, research shows. Instead, UCIPM recommends trying a spray of natural insecticidal oils or soaps (especially underneath leaves), including garlic, clove, mint, rosemary, neem, and cottonseed oils.
When can a spider mite-infested plant be saved?
In a perfect world, you’d be able to save your plant. “As long as the plant has not completely succumbed to the infestation, most plants can be saved but will not necessarily be aesthetically pleasing for some time,” Bell says.
It’s kind of up to you to decide what you are (and aren’t) OK with when it comes to the appearance of your plants, which can end up with stippled leaves from spider mites.
“Fertilization and care over time can help improve the aesthetics and replace damaged leaves,” Bell says.
When should a spider mite-infested plant be thrown out?
Again, a lot of this comes down to what you’re willing to tolerate. If a sickly-looking plant isn’t something you want to look at every day for a while and you’re not overly attached to the plant, it may be time to pitch it.
“From a distance, it may look like your plant might be yellowish from lack of nutrition or dehydrated from lack of water,” Bell says. “Upon closer inspection of the plant, look for very fine webs that are created by spider mites on the plant.”
Spider mites feed on plants by piercing the the leaf and sucking out the nutrients, Bell explains. “This will leave very fine white stippling that will eventually lead to brown spots and then the death of leaves,” he says.
Bottom line: Spider mites can get out of hand quickly, and keeping your plants watered regularly, free of dust, and pruned can help keep them away. The good news is, once you get rid of them, your plants should return to their former glory.
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