Spider Mites: What to Know

Medically Reviewed by Poonam Sachdev on January 16, 2023
4 min read

Spider mites are tiny pests that damage gardens and landscaping. They eat fruit trees, ornamental houseplants, vegetables, and other common plants. If left unchecked, spider mites can reproduce quickly and kill plants. Luckily, you can use simple methods to protect your plants from these destructive pests. Here’s what you need to know about spider mite characteristics, health risks, removal strategies, and more. 

Spider mite is a common name that refers to over 1,600 mite species. These pests are considered arachnids, a family that includes scorpions, spiders, and ticks. They frequently produce webbing for protection from the environment and can infest indoor and outdoor spaces. 

What do spider mites look like? All spider mites have the same body structure as spiders and other arachnids. They have two body segments and eight legs. A set of piercing-sucking mouthparts allows them to pierce plants and suck out sap. 

Adult spider mites have round bodies and a pair of red eyespots near their head. Female mites have dark spots on the sides of their body and prickly bristles on their body and legs. Juvenile spider mites are smaller than adults and only have six legs when they first hatch.

Female mites grow larger than males, reaching a maximum length of less than 1/20 inch (1.25 millimeters). They look like small, moving spots to the human eye. 

Spider mites come in several colors based on age and species, including green, orange, red, and yellow. The red species are commonly known as red spiders. 

What do spider mites eat? These pests feed on a wide variety of plants, such as: 

  • Almond
  • Blackberry
  • Blueberry 
  • Cherry
  • Cucumber
  • Elm
  • Eggplant
  • Hydrangea
  • Redbud
  • Rose
  • Squash
  • Tomato

Some species eat trees like balsam fir, hemlock, honeylocust, oak, and spruce. 

What is the spider mite life cycle? This pest’s life cycle varies somewhat by region and species. Dry conditions provide an ideal breeding environment for spider mites, and many species reproduce during the warm summer months. Some species lay eggs as the weather cools and hatch in the spring. 

After mating, female spider mites typically lay large, round eggs around leaf veins. Each female can lay a dozen eggs daily for two weeks after mating, so the population can grow quickly. In warm and dry weather, a new generation of spider mites can reach maturity within 7 days of hatching. 

Spider mites typically change color as the weather cools, turning a bright orange or red. In some species, adult mites die in the winter, and new mites hatch in the spring. Other species, like honeylocust and twospotted spider mites, survive the winter by sheltering in bark cracks, garden debris, and other hiding spots. 

In warm regions, spider mites can survive and reproduce all year.

There are over 1,000 species of spider mites, but it’s challenging to identify particular varieties. Fortunately, you can manage all spider mites with the same techniques, so you don’t need to know the specific species. 

Here are a few common species you may encounter in your garden or yard: 

  • Oak red mite (Oligonychus bicolor). This spider mite eats beech, birch, elm, and oak trees. The leaves of affected trees often turn bronze or yellow. 
  • Spruce spider mite (Oligonychus unungius). This pest targets arborvitae, balsam fir, helm, pine, and spruce trees. The leaves of affected trees look mottled, and fine webbing appears between the needles. Heavily infested trees may need to be cut down. 
  • Twospotted spider mite (Tetranychus urticae). This species feeds on over 200 species of plants, including houseplants, flowers, fruits, trees, and vegetables. It spins large quantities of webbing.

Twospotted spider mites and other species live throughout the United States. Populations may be especially high in the southeast. 

You can find spider mites living in many plants, including flowers, fruit bushes, shrubs, trees, and vegetables.

You may spot spider mites crawling on your plants, but their microscopic size can make them challenging to detect. Checking for plant damage and webbing are the easiest ways to tell if you have an infestation. 

Typical signs of spider mite plant damage include: 

  • Small white or yellow spots on leaves
  • Bronzed or bleached leaves 
  • Shedding leaves
  • Damaged flowers 
  • Dying plants 

You may also notice a lot of silk webbing on plant leaves.

Two conditions can make your plants more appealing for spider mites and lead to an infestation. 

These microscopic pests prefer high temperatures and low humidity. Temperatures over 80 degrees Fahrenheit and humidity below 50% provide an ideal environment. 

The absence of natural predators allows spider mites to flourish. These mites often get eaten by other arachnids and insects, such as predatory mites, lacewings, and thrips. If you eliminate predators with pesticides, spider mite populations can explode.

Are spider mites dangerous? Spider mites mostly injure plants, which can cause crops to die and lead to economic losses. They pose few risks to humans and pets. 

Do spider mites bite? These pests have piercing-sucking mouthparts that they use to pierce plants. They don’t have fangs to bite humans. 

Do spider mites cause allergies? Exposure to spider mites may cause fruit farmers to develop occupational asthma and rhinitis, but more research is needed to determine how often this sensitivity occurs.

You can eliminate spider mites with several techniques. 

Inspect plants frequently. Check your plants for signs of spider mites regularly so you can get rid of these pests before they multiply out of control. It’s also a good idea to isolate new plants for several weeks to ensure they aren’t harboring pests. 

Biological control. Spider mites have many natural predators that keep their population in check. You can release predatory mites into your garden to eat spider mites. 

Spray plants. Regularly spraying plants with water can wash away spider mites. Add an insecticidal soap or oil to your spray if necessary. 

These methods can keep your garden pest-free and protect your plants from spider mite damage.