Spider mites are tiny pests commonly found under plant leaves. These little spiders can damage fruit trees, houseplants, ornamental plants, and vegetables. The mites reproduce quickly, especially in hot, dry weather. If not dealt with early, spider mites can seriously harm or even kill your plants.
Thankfully, there are some pretty simple ways to get rid of spider mites. Here are some ways to spot and kill spider mites on indoor plants.
What Are Spider Mites?
Spider mites usually refer to over 1,200 types of mites. These pests are arachnids. That's the family of scorpions, spiders, and ticks.
They're so small, you may only spot the fine silk webs from spider mites. They use a pair of glands near their mouth to spin the fine silky web. The webs help the spiders spin down from infested to noninfested leaves. That's where they get the name, "spider" from.
The most common types are the two-spotted and spruce spider mites. These little spiders can infest indoor and outdoor spaces.
What do spider mites look like?
All spider mites look like small spiders and other arachnids. They have an oval body with eight legs. Their mouthparts are called stylets. This needlelike structure pierces plants to suck out sap.
Baby (juvenile) spider mites are smaller than adults. The juveniles have six legs after hatching. Adult spider mites have a rounder body. A pair of colored eye spots sit near their head.
Female mites have dark spots on the sides of their body. The females also have prickly body and leg bristles. The male mites are smaller than females. The females get up to 1/20 inch (1.25 millimeters) long. To the human eye, a female mite looks like a small moving spot.
The adult mites can be seen if you shake infested leaves over a white piece of paper. You can also use a magnifying glass to see them.
Spider mites come in several colors. It depends on the age and spider mite species. They can be green, red, yellow, or brown. As winter sets in, you may notice shades of red or orange. Perhaps it's the reason they're sometimes called "red spiders."
What do spider mites eat?
Spider mites feed on a wide variety of plants. And some types of spider mites can feed on thousands of different plants. They can be a major problem for your yard, garden, or greenhouse. They can infest your indoor ornamental plants, too.
These pests feed on plants such as:
Fruits and berries: Blackberry, blueberry, strawberry, raspberry, and tomato
Vegetables: Cucumber, eggplant, squash, beans, sugar peas, and lettuce
Trees and shrubs: Juniper, spruce, rose, arborvitae, and azalea
Annuals and perennials: Hydrangea, marigolds, salvia, New Guinea impatiens, lantana, and viola
Certain mite species eat conifers such as fir, false cypress, pine, taxus, and oak. They also target fruit trees, such as cherry, pear, and plum.
Where do spider mites live?
Spider mites cover plant leaves, shoots, and flowers. Some species are found all over the world. Some adult spider mites lay eggs and die during colder months. But other types survive during the winter by sheltering (diapause). It's a type of hibernation.
The honeylocust and two-spotted spider mites live in bark cracks, garden debris, and other hiding spots. These little spider mites find a place to slow down for the winter. Their hormones activate to wake them up in the warmer months.
Spider Mite Life Cycle
This pest's life cycle can change by region and species. If the spider mite lives in a dry region, it can reproduce more. The dry weather provides an ideal breeding ground.
Many species lay eggs during the warm summer months. In warm regions, spider mites can survive and reproduce all year. Some species lay eggs as the weather cools down. The eggs are typically clear but become cream-colored before hatching.
After mating, female spider mites usually lay large, round eggs. They put the eggs around leaf veins. Some types of spider mites can lay eggs on either side of the leaf. Leaves protect newly hatched juveniles (babies) from sunlight.
Most female spider mites prefer the bottom of the leaf for laying eggs. Each female can lay a dozen eggs each day, for two weeks. This means the population can grow quickly. And their silky threads help them move along under the leaf.
In warm, dry weather, a new spider mite can grow up (mature) within seven days of hatching. As the weather cools off, spider mites usually change color. They'll turn bright orange or red.
Some species of adult mites die in the winter while others shelter. The new mites hatch in the spring.
Types of Spider Mites
There are about 1,200 known types (species) of spider mites. They belong to the Tetranychidae family. It's hard to see them without a microscope. You can also use a 10-20 power magnifying glass.
Here are a few common types you may find in your garden or yard:
Oak spider mite (Oligonychus bicolor). It's also called the oak red mite. This spider mite mostly feeds on red oak. You'll also find it feeding on beech, maple, elm, and chestnut trees.
Oak spider mites have a dark reddish-brown color. You can find them in North Carolina to west Kansas. The leaves on the lower branches of infested trees can turn bronze or yellow.
Spruce spider mite (Oligonychus unungius). This pest targets arborvitae, fir, conifers, hemlock, juniper, spruce, and sometimes pine trees. The leaves of the trees lose color. You may also see fine webs between the needles.
These mites are most active during the spring and fall. They're not very active during the hot summer. Heavily infested trees may need to be cut down.
Two-spotted spider mite (Tetranychus urticae). This spider mite spins silk webs like the pacific and strawberry mites. But the two-spotted spider mite always spins its web while walking. It lives all over the U.S., especially the southeast. This spider mite reproduces in hot, dry conditions.
The two-spotted spider mite feeds on many kinds of flowers, fruit bushes, trees, and shrubs. This spider likes to eat primrose, violets, fruit trees, vegetables, houseplants, and brambles. Adult mites look pale with two greenish spots. Females often turn reddish-orange in the winter.
Signs You Have Spider Mites
Spider mites are very small. So they're often hard to see with the naked eye. If you have a microscope or magnifying glass, you can use it to look for mites. But a good way to spot mites is to look for leaf damage. Look closely for silk webs on your plants, too.
You may spot spider mites crawling on your plant leaves. But they're very small and can be hard to detect. Typical spider mite damage on plants can look like:
Patchy or speckled. Look for small, light-colored spots on the leaves. You may think the plant appears dusty or faded. The leaves can get a white stippling or dotted appearance.
Color change in foliage. Leaves may lose their healthy green color. They may also become yellow, gray, or bronze. The spider mites remove the juicy leaf contents.
Premature leaf loss. Affected leaves may dry up. They can also fall off. The plant may look unhealthy or sick.
Fine webbing. You may see fine or silk webs. The webs may appear between stems or under leaves.
Dying plants. Plants may become weak. Your plant may stop growing or die over time.
Check the underside of leaves closely. This is where most spider mites cluster to lay their eggs. The area will likely be dry, too.
Why Do You Get Spider Mites?
Ideal conditions can make your plants tastier for spider mites. These tiny pests prefer drier, hotter climates. Temperatures over 80 °F with humidity lower than 50% invite them in.
Sometimes spider mites show up after you've used a pesticide. That's because their natural predator is gone. Pesticides can actually wipe out the good insects.
Spider mites often get eaten by other arachnids, predatory mites, lacewings, and thrips. Without predators, spider mites can multiply almost overnight. And the conditions lead to lots of spider mites (infestation).
What usually causes a spider mite outbreak on plants?
"In the field and in greenhouses, spider mite outbreaks on crop plants are often associated with hot and dry conditions," says Richard Clark, PhD, professor and section head of Genetics and Evolution at the School of Biological Sciences at the University of Utah, Salt Lake City, Utah. "Many spider mite species complete their reproductive cycles far more rapidly at higher temperatures."
But web-spinning mites can survive during the winter. They'll burrow under the bark scales, ground litter, or even trash. But once it warms up, the little spiders can hatch and grow.
Once an outbreak starts, how fast can it spread between plants?
If spider mites have food and warmth, they can spread in less than a week. If your plant gets dry, it's at risk. Once spider mites reproduce enough, they'll infest the plant.
They can quickly "spread to uninfested plants by crawling or hitching rides on air currents,” says Clark. "[They] can overwhelm and even kill the plants they live on."
Are Spider Mites Dangerous?
Spider mites are herbivores. They eat plants, not humans. Spider mites pose few risks to humans or pets. They only injure plants and plant leaves. But this can cause crops to die and lead to economic loss.
In fact, the two-spotted spider mite feeds on more than 1,275 types of plants. This pest has destroyed entire fields of potatoes. The mite has also killed between 50%-80% of strawberry crops from North Central Florida.
Do spider mites bite?
These pests have piercing-sucking mouthparts to eat plants. Spider mites use their tiny mouths to pierce leaves. They don't have fangs to bite humans. And they don't make venom.
Do spider mites cause allergies?
There are only seven mite allergens on record — none are from spider mites. Rarely, some fruit farmers can get a sensitivity to spider mites. They get occupational asthma and rhinitis symptoms. But it's still unclear how this happens.
How to Get Rid of Spider Mites
If spider mites damage your plants, here are some ways to control them:
Check your plants regularly. Check under your plant leaves. Look for signs of yellow spots or webbing. Catch the mites early to prevent an infestation. It can make it easier to manage, too.
Also, keep any new plants away from others after bringing them home. If they're pest-free after a couple of weeks, you can combine them.
Use natural predators. You can introduce natural predators such as predatory mites, thrips, or certain types of lady beetles. You can buy and release the good insects into your garden. Good insects can help control spider mites.
You can also buy predatory mites to release onto infested plants. They work best on two-spotted spider mites. First, try to identify the type of mite you're dealing with.
Spray your plants. A strong spray of water can knock some types of spider mites off your plants. One study showed strong rainstorms can cut down the number of eggs inside a web. Although webs can keep predators away, they don't protect eggs from the climate.
Spray your plants regularly to keep the number of mites down. If mites keep coming back, use an insecticidal soap, horticultural oil, or miticide. Check your local laws to see what's approved. Use miticides during the summer season. And always follow label instructions to stay safe.
Skip harsh insecticides, like carbaryl (Sevin). The chemical can kill off natural predators, too.
These methods can help keep your garden pest-free. They can also protect your plants from spider mite damage.
Takeaways
Spider mites are tiny pests that can cause serious damage to many types of plants, especially in hot, dry weather. Find early signs of leaf spotting, color loss, or fine webs to get rid of spider mites. Always check your local laws before using a safe insecticidal soap, horticultural oil, or miticide. Regularly inspect under leaves, water, and isolate new plants to keep your garden healthy.
Spider Mites FAQs
What is the fastest way to get rid of spider mites?
Quickly get rid of spider mites with an approved insecticidal soap, miticide, or oil. Horticultural oils can also help summer perennials. The dormant oils target mites and their eggs in the spring and fall.
Evenly spray the oil directly on the leaves, from top to bottom. Avoid spraying on any flowers, though. Keep in mind, regular insecticides won't work as well against spider mites. Be sure to follow label instructions to stay safe.
What is the best homemade spider mite killer?
The best homemade spider mite killer depends on the plant and type of mite. If it's an outdoor plant, try releasing a good insect like the western predatory mite. Also, keep your plants watered to prevent spider mite breeding.
If these aren't working, many locally approved plant extracts can kill mites (acaricides). Some options are garlic extract, clove oil, mint oil, rosemary oil, or cinnamon oil. Cover the mites with the oil and under the leaves, too. Since webs and eggs are more protected, you may need to reapply later.
Does vinegar kill spider mites?
Vinegar likely won't kill spider mites. But the weak acid may damage or kill your plants. Vinegar can also harm helpful bugs that control spider mites. Instead of vinegar, try safer options like insecticidal soaps or horticultural oils.
What chemicals are used to control red spider mites?
Insecticidal soaps or horticultural oils, like neem or canola, can control red spider mites. You can also try plant-based sprays made with rosemary oil, clove oil, or mint oil. Avoid using insecticides like carbaryl or pyrethroids. The chemicals can kill helpful insects. And this can lead to more mites.