Vijai Pandian column: Houseplant Pest Control

8:18 PM, Jan. 25, 2013  |  Comments
- -A mass of green houseplants fill in the empty spaces.
- -A mass of green houseplants fill in the empty spaces.
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Houseplants add life and beauty to our home and office environments. Their vivid colors, textures, and fragrances enhance the serenity of the surrounding and improve indoor air quality. For many people, growing houseplants satisfies their gardening urge and has become a silent companion in their life.

Though houseplants are relatively easy to grow, they can be vulnerable to insects and other environmental problems causing the plant to appear unsightly. These pest problems can be managed through early detection and implementation of control measures in a timely fashion.


When buying a new houseplant or nurturing an existing plant, always check for signs of insects on both the top and undersides of the leaves. A 10x hand lens can come in handy for detecting smaller insects such as spider mites that hide on the underside of the leaves. Look out for a sticky honeydew-like substance, black molds, white cast skins, tiny cottony clusters, brown or gray bumps, mottled yellow discoloration, or disfigured leaves.

If any signs and/or presence of insects are detected, isolate the infected plant from the rest to prevent it from spreading. When an infestation is confined to a few leaves, one or more of the following non-insecticide methods can be used:

? Gently swab the pests with cotton dipped in mild detergent (1/2 teaspoon per quart of water) or rubbing alcohol solution. Beware not to use rubbing alcohol to wipe pests on plants with hairy leaves like African violet.

? Dislodge the pest with a forceful spray of lukewarm water. Follow-up spray may be needed.

? Prune off the badly-infested leaves or branches.

Insecticide Treatment

The above preventive control method is applicable if the infestation is light. When the insect population is out of hand, an appropriate insecticide treatment is necessary. It is important to identify the insect pest before choosing any insecticide options. For help in diagnosing the insect pest, bring an infected specimen to the Extension Office. Common houseplant insects are aphids, scales, mealy bugs, spider mites, thrips, and white flies.

? Aphids: A common sap-sucking pest that feeds in clusters on stems, young leaf buds, shoot tips, flowers, and the undersides of leaves. They have pear shaped bodies and are mostly green colored in houseplants. In large colonies, both winged and wingless forms of adult aphids can be seen. Typically, aphids excrete a sticky honeydew-like substance on the leaf surface which in turn attracts black sooty mold growth. They also cast off white skins on the surface of the leaves.

? Scales: An unusual insect that looks like a small gray or brown bump or like a hard shell body tightly attached to the stem and leaf surfaces. Like aphids, they produce sticky honeydew and cause yellowing and defoliation of the leaves.

? Mealy bugs: A soft body insect covered with white, waxy filaments and are seen underside of the leaves and stem joints like a white cottony ball.

When it comes to use of any insecticides, always read the fine print on the label and follow the directions. One of the most common insecticides for houseplant use is the insecticidal soap. A thorough foliar spray both on top and the underside of leaves is necessary for at least partial control of insects like aphids, mealy bugs, and spider mites. Repeated applications may be needed. Be aware that some houseplants like dieffenbachia, ornamental ivy, maiden hair fern, jade plant, fuchsia, and begonia are sensitive to insecticidal soap. For scales and spider mite control, horticultural oil can be a better choice than insecticidal soap. But make sure to get a good coverage when spraying the plant. You can also use systemic insecticides (imidacloprid) labeled for houseplant use on scales, mealy bugs, aphids, and spider mites. An advantage of using systemic insecticides is that it minimizes the use of other spray applications, but they are most effective during the growing season when plants are active in tapping the nutrients from the soil. Other insecticides labeled for houseplant use are neem oil, pyrethrins, and resmethrin.

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