Hot, dry weather brings out twospotted spider mite.
Twospotted spider mites are small (1/50 inch) and oval-shaped. They can range in color from yellowish or greenish to brown to orange-red, with two dark spots on either side of their body. Active nymph and adult mites appear as tiny, eight-legged, yellowish to reddish specks. Plants attacked may have very fine webbing on or between the leaves.
Damage Caused by Twospotted Spider Mites
Attacked cucurbit leaves are stippled with white and then brown specks. Damaged leaves usually appear dusty or bronzish; they may turn brown and drop from the plant. Spider mites are a common pest on many types of plants, including houseplants, fruits, vegetables, and landscape plants, particularly during hot, dry weather.
- Spider mites have sucking mouthparts that they will use to puncture plant material to feed on individual plant cells.
- They remove the cell's contents, including chlorophyll, which gives leaves their green color. This causes leaves to have a speckled or mottled appearance.
- As feeding continues, leaves may begin to yellow or bronze and eventually die.
Severe infestations of spider mites can cause plants to become stunted, defoliated, and potentially die.
Twospotted spider mites also produce webbing, which can also indicate their presence. The webbing is produced by glands near their mouths, and strands will be spun on the undersides of infested leaves. As mite populations grow, the webbing can completely cover a plant's leaves, stems, and flowers.
Life Cycle of the Twospotted Spider Mite
Twospotted spider mites overwinter as adult females on host plants or in the soil. When temperatures begin to warm in the spring (April and May), they will become active and start feeding. Females don't have to mate before reproducing and can lay over 200 eggs in their lifetime. Twospotted spider mites can go from egg to adult in as little as five days during favorable conditions (hot, dry weather), meaning populations can rapidly expand.
Management of Twospotted Spider Mites
Spider mites can be difficult to see until populations get large and plants start showing symptoms of their feeding. If you suspect you have spider mites, closely inspect the undersides of leaves using a magnifying glass. Alternatively, you can use a piece of white paper and shake plant leaves over it. This will cause any mites present to fall on the paper, making them easier to see.
It's important to note that not all mites are pests; some are predators of other mites.
One way to determine if you have a pest or predatory species is to crush and smear them.
- For the most part, mites that feed on plants (pests) will be green, while predatory species will be yellow or orange.
- If predatory mites are numerous and plant damage is not occurring, treatment is probably unnecessary.
Twospotted spider mites thrive during hot, dry weather and on stressed plants. Making sure plants are well watered during these conditions can go a long way in preventing outbreaks.
Spider mites are often introduced into landscapes and homes on infested plant material. Inspect plants before putting them in your landscape or bringing them indoors. Plants can also be quarantined away from other plants until you are sure no spider mites are present.
Spray infested plants with a forceful spray of water. This will remove the mites, their eggs, and webbing. You may need to repeat this several times.
Predators such as lacewings, lady beetles, and predatory mites will often keep spider mite populations in check outdoors. During hot, dry weather, the mites reproduction may outstrip the ability of the predators to control them. Previous insecticide spraying may kill natural enemies, making damaging infestations more likely. Take steps to conserve predators by providing habitat and avoiding pesticide use if possible.
Insecticidal soaps and horticultural oils are commonly used to manage spider mites. These pesticides have no residual activity and must come into contact with the mites to work. Therefore, good coverage is important for both the upper and lower sides of leaves when using them.
Contact your county Extension office for current pesticide controls.
Commercial: Treatment usually is required only around field edges, but if mites are numerous, also check for areas throughout the field that may need to be spot treated.