How to Manage Pests

Although related to insects, mites are not insects but arachnids, similar to spiders and ticks. Mites are tiny and difficult to see. Look for webbing and check the undersides of leaves to be sure spider mites are present. Sprays of water, insecticidal oils, or soaps can be used for management. Spider mites have many natural enemies that often limit populations.

• To the naked eye, spider mites look like tiny moving dots. Use a magnifying lens to see them.
• Adults are less than 1/20 inch long, have eight legs and an oval body, with two colored eyespots sometimes visible near the end of the head.
• Spider mites live in colonies, mostly on the under surfaces of leaves; a single colony may contain hundreds of mites.
• When numbers are high, leaves, twigs, and fruit may be covered with dense webbing.

• A small number of mites is not usually reason for concern, but very high populations can be damaging, especially to annual plants.
• Often, the damage first shows up as a stippling of light dots on the leaves; sometimes the leaves take on a bronze color. Heavily infested leaves may turn yellow and drop off.
• Damage is usually most severe under hot, dusty conditions and on water-stressed plants.

• Spider mites have many natural enemies, which prevent them from becoming pests in many landscapes, especially when undisturbed by pesticide sprays.
• Key predators include predatory mites, which are about the same size as plant-feeding mites, but have longer legs and are more active.
• Other common predators include thrips, lacewings, and lady beetles.
• Keep dust down. Plant ground covers, use mulches, and irrigate regularly.
• Avoid using insecticides that kill natural enemies.

• Water plants sufficiently to avoid drought stress that increases mites and damage.
• Most woody plants can tolerate low to moderate mite populations, and natural enemies are often abundant.
• In gardens and on shrubs and small trees, spraying or thoroughly misting the underside of foliage at least once a day with water will often reduce spider mite numbers adequately.
• If you wish to use an insecticide, a good choice is an insecticidal oil or soap (or both combined) applied so the undersides of leaves are completely covered. Be sure mites are present before treating. Don’t spray when plants are water-stressed or if it is very hot.
• Spider mites frequently become a problem after the application of persistent insecticides such as imidacloprid or pyrethroids—not only are these insecticides not very effective against mites, they often kill off their natural enemies and stimulate mite reproduction.

Life cycle of spider mites. Adults are no bigger than the tip of a pencil. Use a magnifier to see them.

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