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Gardening Articles: Health :: Houseplants

Those Pest-y Houseplants (page 2 of 3)

by Charlie Nardozzi

Control Strategies

Even if you are meeting the cultural requirements of your houseplants, insects can still be a problem. If you placed your houseplants outdoors in summer, check them carefully for insects before moving them indoors in fall. After the first few weeks indoors, check again for any insect eggs that may have hatched.

Here are the six most common houseplant pests, and some organic controls to keep them at bay. When using a spray, always test it on a few leaves before spraying the whole plant because some houseplants (e.g., ferns) are sensitive to specific sprays. Always use the recommended dosage amounts.


These small, soft-bodied insects may be pale green, pink, black, or yellow, depending on the species. They like to cluster on tips of new growth and leaf undersides, sucking out plant juices and causing leaves to become distorted and yellow. Aphids secrete a sugary fluid called "honeydew" that may spur the growth of a sooty, black fungus on leaves and cause stickiness on leaves, floors, and rugs. Aphids like fast-growing plants, such as hibiscus.

Controls: Place the plant in the shower and knock aphids off the leaves with water, or wash the leaves in a sink full of soapy water. Cut back on high-nitrogen fertilizers, which stimulate new growth. For widespread infestations, spray the foliage with insecticidal soap, neem oil, or horticultural oil.

Fungus Gnats

These small, dark-colored flies jump and fly across the soil surface and around the house. Although they generally don't harm plants, they're a nuisance. The adults lay eggs in potting soil. If numerous enough, the larvae can damage plant roots.

Controls: Fungus gnats feed on organic matter and fungi in the soil. They especially like moist, rich soil. Let the top layer of the soil dry out between waterings to discourage their egg laying. Avoid using fish emulsion fertilizers since they foster the fungus that gnats like to eat. Drench the soil with Bacillus thuringiensis 'israelensis' (B.t.i.) or neem oil to control the larvae.


These soft-bodied insects group in white cottony masses and suck sap from plants. Their feeding weakens the plant and causes leaves to shed. Like aphids, they excrete large amounts of sticky honeydew. While adults tend not to move once settled on a leaf, flower, or stem, the young (crawlers) can move around the plant. Mealybugs favor cacti and jade plants.

Controls: For small infestations, wash the leaves in a shower to dislodge the insects, or dab individual mealybugs with a cotton swab doused in rubbing alcohol. The alcohol will desiccate the insects, killing them. For larger infestations, spray with insecticidal soap, neem oil, or horticultural oil.

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