How to Get Rid of Spider Mites—One of the Most Common Houseplant Pests
Raising plants can be a both rewarding and frustrating experience. One discouraging drawback is when your greenery starts to look a little worse for wear and you can't figure out the cause. If the leaves on your plants begin to look stippled or distorted, it's possible it has fallen victim to mites. "Spider mites are one of the more common—and exceptionally frustrating—pests of plants both indoors and in the garden," says Josh Brown, owner of Predatory Plants. The arachnids aren't visible to the naked eye, reproduce rapidly, and leave a messy web in their wake.
While there are many different varieties of mites, spider mites are the most common. The pest lives in nature and in nursery settings, so you should check your plants for mites before bringing them home from your local gardening center and before moving garden plants indoors during cold weather seasons. "Since mites are so small, they can travel on human clothing or shoes from the outdoors, or they can be brought into your home on plants from the store," says Brown. How easy spider mites are to come by means it's important to be vigilant at protecting your plants from them.
Why Spider Mites Are So Common
Spider mites are most often a nuisance for houseplants, because the conditions of your home form a very hospitable environment for the pest. "Spider mites thrive in warm, low-humidity conditions found in most homes," says Melinda Myers, host of the Great Courses How to Grow Anything DVD series. She also notes they typically attack stressed pants, which is common for tropical plants growing indoors.
Spider Mites vs. Other Mite Species
If your plant has mites, more often than not it's spider mites. Despite this fact, there are many different varieties of the arachnid to look out for. "Spider mites are the most common, but cyclamen and broad mites are an occasional pest of houseplants—these are tiny and do not form webs like the spider mites," Myers says.
It's also possible that your plant has fallen victim to predator mites, which feed on spider mites. Brown says sometimes a plant will have predator mites if they were used in a greenhouse as a biocontrol. "The most noticeable difference between predatory and common spider mites is that predatory mites can be seen moving with the naked eye, whereas spider mites are only visibly active under a magnifying glass," Brown says.
Signs Your Plant Has Spider Mites
Knowing the signs of a spider mite infestation can help you get ahead of it. "Spider mites have needle-like mouthparts," Meyers says. "They use these to pierce the leaf surface and suck plant juices." According to Brown, this action typically leaves behind stippling on the leaves—or tiny white dots where the sap has been removed from the leaf tissue. "Usually it begins around the large veins of the plants on the tender leaves," Brown says. "In cases of severe infestation, the leaves will curl inward and are often coated in a messy web."
How to Check for an Infestation
If you see signs of a mite infestation and want to know for sure, Myers says to get out a magnifying glass and hold a piece of white paper under a leaf. Next, shake the leaf and watch for the specks to move across the page. "I often feel the grittiness of droppings and their cast exoskeletons," Myers says. "As mites grow, like insects, they cast off their outer skeleton—that is their structure instead of bones like ours."
How to Prevent Spider Mites
Before adding a new plant to your collection, there are a few precautionary measures you should take against mites, as they can easily travel from one plant to another.
Isolate Your Plant
It may seem drastic, but you want to remove any chance that a potentially mite-infested plant could affect the rest of your greenery. Myers says to isolate new purchases from the rest of your houseplants for several weeks and to watch for signs of spider mites and other pests before introducing it to the rest of your collection.
Clean the Leaves
Not only does cleaning the leaves eliminate dust, which allows your plant to access more sunlight, it also removes mites that may already be present. Myers says to use a damp cloth to wipe down smooth leaved plants and a makeup brush for fuzzy leaved plants.
Reduce Plant Stress
Since stressed plants are more susceptible to spider mites, it's important to promote a healthy and habitable environment. Myers says to make sure plants receive sufficient moisture and sunlight to reduce stress.
Since spider mites prefer low humidity, one way to keep them at bay is to increase the moistness of your plant area. You can do this by grouping plants together (once you've completed the isolation period). "As one plant transpires—loses moisture through pores in the leaves—the others benefit," Myers says. She also notes that you can set plants on saucers filled with water, making sure the plants are elevated above the water. "As the water evaporates it increases the humidity around the plants," she says.
How to Get Rid of Spider Mites
All hope isn't lost when you identify a spider mite infestation—there are a few ways to get rid of the arachnids once they've found a home on your plant.
Soap and Water
One way to get mites off your plant is to wipe down the leaves with soapy water. To do so, Brown says to start by mixing a small amount of dish soap with about 1 cup of water. Next, dip a cloth into the solution and fully wet and wipe down the leaves, making sure to also clean the stems and undersides of the leaves. Fully rinse off any soap residue from the plants and soil.
Myers recommends using horticultural oils, which are organic and kill all stages of mites on contact. Mites are similar to insects in that they breathe through the holes in their exoskeleton—the oil coats their bodies and suffocates them, causing them to die off. For application, spray the oil on the upper and lower leaf surfaces and stems of the infected plant. "Since these are contact killers, repeat applications are usually needed since you may miss some of the insects" Myers says.
Spray with Water
A strong blast of water will dislodge many of the mites, but it won't be effective when done only once. "Water showering alone is not effective at removing mites," says Brown. "It can deter them and rinse away some of them, but most mites hide in the crevices or undersides of leaves and will not be affected by showering the plant." Repeat the process weekly to keep the mites from taking over your plant again.
If you have room and the weather conditions are tolerable, Brown recommends moving your plant outdoors. "Mites have many natural predators, like ladybugs, and they can help clean plants as well," he says.