Spider mites are arachnids, so small they can barely be seen. But the damage caused by the piercing and sucking pests is apparent in the garden and greenhouse. Yellow or white stippling, red spots or yellow dots on the leaves are a warning that if the leaf is turned over the mite will be found amongst cast skins and bits of excrement.
The spider mite injects toxins into plant tissue while it feeds. The toxins cause discoloration along the veins, spreading to the entire leaf which will then dry out. Their attack keep plants from blooming, or the flowers could be disfigured. Bulbs are not safe from spider mites. An infestation can cause the bulbs to decay, turning them to dry pulp, inviting bacterial and fungal attacks.
Identifying the Spider Mite
Spider mites have 4 pairs of legs, and the mouthparts are fashioned for piercing and sucking. The most common species of spider mites, cyclamen mite (Stenotarsonemus pallidus), the two spotted spider mite (Tetranychus urticae), and broad mite (Polyphagotarsonemus latus), can be found throughout the United States, as can the bulb mite (Rhizoglyphus echinopus).
Leaves and flowers of plants infested with spider mites might be encased in a fine webbing. A magnifying glass is needed to see the mite. To confirm their presence, tap a few leaves on a sheet of paper and watch for movement.
The Spider Mite HabitatThe spider mite thrives in dry, hot environments. Before bringing bedding plants into a garden or greenhouse, examine them carefully for mite damage. Once inside a greenhouse, the mite can crawl from one plant to another if they are placed close enough together so that the leaves touch. Once the mite is introduced to the greenhouse, the conditions are perfect for rapid development from egg to adult. The hotter the conditions, the better for a new generation of mite to be produced every two weeks. The heat also encourages the number of eggs they lay.
A sun garden that has been treated with chemical pesticides is also inviting to the spider mite. Damsel mites, ladybugs, green lacewings and other types of mites that would be natural predators have been eliminated, making the garden safe for the mite while increasing its immunity to the very chemicals that target him.
Protect the Garden From Spider Mites
After the garden goes dormant in the fall, make a final inspection for the mite for evidence of damage. Don't encourage spider mites to winter in your garden. Consider a dusting with diatomaceous earth for organic elimination of the garden pest. Spider mites can catch rides around the property on garden tools or even on human hands. Keep rubbing alcohol available to clean tools, and don't move from infected areas to mite free plants without a proper cleanup.
Trim yellow leaves or dried blossoms from plants with clean, sharp tools, and destroy the debris immediately. Keep the garden weed free, eliminating the formation of leave bridges the spider mite can use to travel from plant to plant.
Introduce wild brambles into an area near the garden, and keep them pesticide free to encourage firefly larvae, predatory midges, ladybugs, ambush bugs and dance flies who prey on the spider mite. If your garden has room, consider companion planting for natural pest control.
When planting bulbs for spring, inspect them carefully for corky brown spots or other signs of mite infestation. Destroy the bulb along with the infested soil around it. Don't use infested debris for compost, and don't plant fresh bulbs in infested areas.
Sources:
Reilly, Ann, Step By Step Successful Gardening. Iowa: Meredith Corporation, 1987
Ball, Liz, Ball, Jeff, Flower Garden Problem Solver. Pennsylvania: Rodale Press, 1990
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