Spider mites in home gardens
- Mites are not insects but arachnids.
- All arachnids, including mites, have two main body parts and eight legs.
- The two-spotted spider mite can infest over 200 species of plants.
- Severe spider mite feeding can stunt the plant's growth and can even kill the plant.
Each species of mite is different in its feeding pattern. If you have any doubt about the type of species found in and around your home, contact a professional pest control service or specialist to give you the best advice.
- Clover mites feed on grass, but do NOT bite humans or animals.
- Velvet mites are harmless to people and control other mites.
- Spider mites feed on plants, but are NOT harmful to people.
- Bird and rodent mites can carry diseases that are harmful to people.
Behavior and habits of spider mites
Spider mite (also called two-spotted spider mite) can be found on deciduous trees, evergreens, bedding plants and annual garden plants.
Ornamental plants: arborvitae, azalea, spruce and rose
Bedding plants: lantana, marigolds, New Guinea impatiens, salvia and viola
Garden vegetables: cucumbers, snap beans, peas, tomatoes and lettuce
Berries: blackberry, blueberry and strawberry
Spider mite infestations are particularly common during hot, dry summer weather.
How to identify spider mites
- They are very tiny, about 1/50th inch long.
- Yellow-orange in color, and have two dark spots, one on each side of the body.
- When a heavy infestation occurs webbing will also be present.
Life cycle of spider mites
These mites live through the winter as eggs on vegetation.
- Larvae hatch and complete development in 1-2 weeks depending on the temperature.
- Under high temperatures (>90°F) colonies can reach high numbers in less than two weeks.
- After hatching, the mites build colonies on the undersides of leaves and produce webbing over infested leave surfaces. This webbing gives them the name "spider" mites.
Damage caused by spider mites
They use piercing-sucking mouthparts to feed on the underside of leaves and needles.
- This injury produces tiny white or yellow spots or "stippling" on leaves and needles.
- The plant looks bronzed and has a yellowed discoloration.
- Webbing indicates a spider mite infestation.
- These symptoms may be confused with drought stress.
- On azalea, leaves and flowers also get distorted.
- On garden vegetables and bedding plants, severe infestations may cause plants to die.
If you find discolored leaves and suspect spider mites, hold a white sheet of paper or paper plate under the leaves and shake the branch or leaves. If mites are present, you will find tiny spider-like creatures drop down and move around on the paper.
How to get rid of mites
Check plants regularly for spider mites
- Examine plants for stippling and/or webbing.
- Look closely with a hand lens on the underside of discolored leaves for the presence of spider mites.
- You can also hold a white piece of paper or cardboard underneath potentially infested leaves; shake the leaves and look for spider mites that have fallen.
- Check garden plants every 3-5 days, especially under drought conditions.
Watch plants for signs of stress
Spider mites thrive on plants under stress. Keep plants well watered to reduce the chances of a spider mite attack.
- Most plants should receive about one inch of water a week to avoid stress conditions.
- Conserve moisture through proper mulching.
- Select drought tolerant plants for locations that are particularly hot and dry.
- Do not fertilize plants during drought, as this can add further stress to plants.
- Do not overwater as this can lead to root rot.
Use a high pressure water spray to dislodge some of the spider mites. This can also wash away their protective webbing.
Natural enemies like velvet mites can control spider mites
Certain species of lady beetles (e.g. Stethorus sp.) and predatory mites (e.g., Phytoseiulus persimilis) naturally control spider mite populations.
Velvet mites feed on spider mites
Velvet mites are 1/16 - 1/8 inch long and are found on the soil surface. They are active during spring.
- Mite eggs and larvae can grow inside insects.
- They are harmless to people and gardens.
- Apart from spider mites, they can control other pests like, spring cankerworm, cabbage moth, lace bug and other arthropods.
If the spider mite population is high, natural enemies are not effective at controlling spider mites.
Using pesticides like carbaryl and imidacloprid for mite control can kill these natural enemies as well.
Insecticidal soap and horticultural oil
These are effective against mites and have little impact on people, animals and nontarget insects.
These products will only kill mites that the pesticide directly contacts. They do not have any residual activity.
Target the underside of leaves as well as the top.
Repeat applications may be needed.
Effective active ingredients of residual pesticides include bifenthrin, deltamethrin and lambda cyhalothrin. Use these pesticides only when necessary, as they might affect a variety of insects.
Most spider mite infestations occur when it is hot and dry.
Water plants thoroughly before spraying pesticides for spider mites.
Spray in the early morning or early evening.
These steps will reduce the risk of further stressing plants and causing injury.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Reviewed in 2018