Gardening Articles: Health :: Houseplants

Those Pest-y Houseplants (page 3 of 3)

by Charlie Nardozzi

Scale

These insects may be flattened and brown, or thick, white, and covered with a waxy or woolly substance. They appear like small bumps on leaves and stems. Leaves of infested plants turn yellow, and the overall vigor of the plant declines. Like mealybugs, the young are mobile, while the adults tend to settle in one area to feed. Ficus and citrus are often attacked by scale.

Controls: Flicking or rubbing the scale off the twigs by hand or dabbing them with rubbing alcohol often controls small infestations. For larger populations, spray horticultural oil or neem oil to cover the shells and suffocate the scale. Scale insects may hang on the twigs and leaves even after they are killed.

Spider Mites

These small insects aren't usually evident until their population soars and they form their characteristic webbing. Their feeding can cause stippling of the leaves and leaf drop. They thrive in hot, dry conditions and are particularly fond of cyclamen, Norfolk Island pine, and schefflera.

Controls: Keep plants misted because high humidity discourages the mites from getting established. Wash off infested plants in a shower or sink full of soapy water. Spray insecticidal soap or horticultural oil on severely infested plants. In houses with many plants, consider releasing predatory mites, such as the two-spotted mite (Phytoseiulus persimilis). These mites feed on spider mites and reduce the population without harming the plants, pets, or people. It will take a few weeks for them to control an infestation.

Whiteflies

These tiny, white insects feed in large numbers on leaf undersides, sucking out plant juices. They secrete honeydew that may cause the growth of a sooty, black fungus on leaves. Their feeding can cause leaves to turn yellow and drop. They are easily disturbed and fly around when you brush against an infested plant. They are often found on hibiscus and ivy.

Controls: Whiteflies are attracted to the color yellow, so you can trap them by hanging yellow cards coated with a sticky substance, such as Vaseline, around your plants. Or suck them up with a vacuum cleaner as you shake your plants. In serious cases, spray plants with insecticidal soap, neem oil, or horticultural oil. In houses with many plants, consider releasing the whitefly parasite (Encarcia formosa). This miniature wasp kills whitefly larvae but doesn't harm plants, pets, or people.

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