Spider mites are tiny sucking insects that infest indoor and outdoor plants. To determine whether a plant has spider mites, hold a piece of white paper under a leaf, and give it a good tap. If tiny rust-colored specks drop onto the paper, your plant probably has spider mites. Plants infested with mites have a salt-and-pepper look, and the foliage color may look washed-out (figure A). On plants with severe infestations, you'll see webs on the undersides of the leaves.
English ivy, among other plants, is prone to infestations of spider mite. Other common pests are scale and mealybug. To help cut down on insect problems, keep plants well-groomed and dead foliage picked off. Spider mites can often be eliminated with jets of water from a water wand or hose-end sprayer. Horticultural oils and insecticidal soap are also effective treatments. If you've tried these treatments and failed, you may wish to use malathion, a organophosphate pesticide. If you use malathion outdoors, be aware that it is moderately toxic to birds and highly toxic to honeybees. Follow label directions carefully, and wear goggles, gloves and other protective clothing as specified by the manufacturer. If you wish to use malathion on a houseplant, you'll need a measuring spoon and a washtub, both of which should be used only with pesticides. Measure warm water into the washtub or bucket, and add the precise amount of malathion specified on the label. Mix the solution. Hold the houseplant's soil in place by covering it with your hand, and dip the foliage into the malathion bath. Set the plant aside to dry. Pour the remaining chemical solution into a watertight glass container, and dispose of it at your county's toxic-chemical disposal site. Never pour pesticides into storm drains or into indoor plumbing. To kill eggs and juvenile mites, use a systemic insecticide after administering the malathion dip (figure B). Systemic insecticides are administered to the soil surface and work inside the plant's tissues. As the plant is watered, its root system will take up the chemical.
If spider mites persist and low-toxicity solutions are ineffective, dip the infested plant two or three more times in malathion solution at one-week intervals, then reapply the systemic treatment once more.
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