Spider mites are a common bug in greenhouses and vegetable gardens. They attack both outdoor and indoor plants. They are very destructive in nature.
Spider mite is generally found in hot and dry conditions. Mostly where other enemy pests have been cleared off by the use of pesticides and insecticides. Thus providing them suitable conditions to multiply and infest.
Though they are harmless to humans, the same is not applicable to plants.
Spider mites suck up the plant juice from the leaves. Gradually they suck all the fluid from the plant leaves. As a result, The leaves turn yellow and drop off.
Thus they are a menace for gardeners and farmers.
In this article, we will learn all the things we should know about spider mites. Questions such as –
- How to identify spider mites?
- What is the life cycle of a spider mite?
- What damage do they cause?
- How to get rid of them?
will all be answered below.
How to identify spider mite?
- The spider mite is very small, about 1/30th inch long.
- They are usually yellowish-orange in color. They have two dark spots on their bodies. Each spot is visible on each side of the body
- They mostly live on the undersurface of leaves. They live in colonies.
- Spider mites are most easily identified by their webbing. Webbing is also a sign of heavy infestation.
What is the Life Cycle of Spider Mites
These mites lay eggs during winter. They survive the winter as eggs present on vegetation.
- Initially, the larvae hatch. After that, they become fully grown in 1-2 weeks. Growth depends mostly on the surrounding temperature.
- High temperatures (>90°F) assist in growth. Colonies may reach high numbers in a period of fewer than two weeks.
- After hatching is complete, the mites build small colonies on the undersides of leaves. They also produce webbing over the infested surfaces of leaves. This webbing officially gives them the common name “spider” mite.
Behavior and Plants Attacked by Spider Mites
Spider mite presence is visible on bedding plants, deciduous trees, evergreens, greenhouses and annual garden plants.
Let us see a few plants where spider mite infestation is seen.
- Ornamental plants: azalea, arborvitae, spruce, and rose
- Bedding plants: marigolds, lantana, salvia, New Guinea impatiens, and viola
- Garden vegetables: snap beans, cucumbers peas, lettuce, and tomatoes.
- Berries: blueberry, strawberry, and blackberry.
What Damage Caused by Spider Mites
They feed on the underside of leaves. They do this by using their piercing-sucking sharp mouthparts. Thus they are harmful to plant growth.
- This injury results in tiny yellow or white spots.
- The plant has a brownish look. Also, discoloration of leaves is visible.
- Webbing is an indication of spider mite infestation.
- These symptoms are often confused with drought stress.
- On azalea plant, flowers and leaves also seem distorted.
- On bedding plants and garden vegetables, severe infestations may lead plants to die.
If you see discolored leaves and suspect spider mites, hold a paper plate or a white sheet under the leaves. Then shake the leaves and branches.
Therefore if mites are present, you will see very small spider-like creatures drop on the paper. Also, you can see them moving around on the paper. Thus it is an easy way to identify them.
How to Get Rid of Spider Mites
Check Plants Regularly for Spider Mites
- Examine plants closely for webbing and/or stippling.
- Look very closely with the help of a hand lens on the underside of yellow leaves. The presence of spider mites might be there.
- You can simply hold cardboard or white piece of paper just below the potentially infested leaves. Then shake the leaves and branches and look for spider mites that may have fallen from leaves.
- Always check garden plants every 2-3 days. During drought conditions, do this regularly. Thus preventing their spread.
Watch Plants for Signs of Stress
Spider mites multiply and thrive on plants especially under stress. Water the plants well. This will help to reduce the chances of a spider mite attack.
- Make sure that plants receive one inch of water per week. This will help to avoid stress conditions. Hence it will avoid their attack.
- Try conserving the soil moisture via proper mulching.
- Select plants that are drought-tolerant. Particularly for the locations that are dry and hot.
- Avoid fertilizing the plants during drought. Because this may add stress to plants.
- Do not overwater the plants. This results in root rot.
Use water spray with a high-pressure to displace some of the spider mites. This will also wash away their protective webbing.
Natural Enemies like Velvet Mites can Control Spider Mites
Certain species of predatory mites (e.g., Phytoseiulus persimilis) and lady beetles (e.g. Stethorus sp.) naturally control the population of spider mite.
Velvet Mites Feed on Spider Mites
Velvet mites are 1/16 – 1/8 inch long in length. They are mostly found on the soil surface. They are very active during the spring.
- larvae and Mite eggs grow inside insects.
- They are harmless to gardens and people.
- Apart from the spider mites, they can control other pests like cabbage moth, lace bug spring, the cankerworm and other arthropods.
If the population of the spider very is high, natural enemies are ineffective at controlling them.
Insecticidal Soap and Horticultural Oil
These are highly effective against mites and no to have little impact on animals, people and nontarget insects.
These pesticides will only kill mites that the pesticide contacts directly. They have no residual activity.
- Target the top as well as the underside of leaves.
- Repeat applications might be required.
Effective active parts of pesticides include deltamethrin, bifenthrin, and lambda-cyhalothrin. Only use these pesticides when necessary. As they might have negative effect on a variety of insects.
Most of the spider mite infestations occur generally when it is dry and hot.
- Water plants thoroughly and completely before spraying the pesticides for the spider mite.
- Spray during the early morning or during the early evening.
- These steps will surely reduce the risk of further stressing plants and causing more injury.