WICHE: Controlling pests on indoor plants

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Tips for dealing with the pests that attack inside your house.

By Jeneen Wiche

Have you noticed a sticky substance on the floor beneath your ficus or philodendron? Are there little scabs on the underside of the leaves of your orchid? Maybe you have noticed that your plants just look a little lackluster.

Well, we can blame some of the plant puniness on being a tropical houseplant indoors in Kentuckiana during the winter.

Low levels of humidity and low levels of light trigger a response in plants that slows them down, causing them to shed foliage and leaving them in a standby phase until the environment turns more favorable.

However, another reality of being a houseplant is that you are susceptible to a handful of insect problems while waiting indoors until spring.

By the time people notice a problem with a plant a couple of things are already beginning to happen. I mentioned the sticky stuff on the floor. Well, that’s actually honeydew. Honeydew is a nice way of saying bug poop. Also, yellowing or the shedding of leaves is common in the winter, but that could be caused by insect problems, too.

Many of the insects that feed on our plants are considered sucking insects, and the worst of the offenders are called scales. There are soft scales and armored scales, the latter of which does not produce honeydew. The former does and is considered the most common and the most troublesome for plants.

Scales can be found on either side of the leaves, but most often they choose to secure themselves on the underside. How do you tell if you have scale? The scale looks like a small oval scab, and besides the stickiness left behind by the honeydew, other symptoms can be seen in distorted, yellowing foliage and an overall pale as the scales suck the juices from the plant.

There are several different ways to control scale, all of which are low on the toxicity scale, no pun intended. Horticultural oil is a safe and effective approach, which essentially smothers the scale. On houseplants apply a 2 percent solution and be sure that you are using the lighter horticultural grade oil, not the heavier dormant oil.

Pruning heavily infested plants may also be a good idea before you begin your treatment. For plants that are lightly infested, you can clean the plant up and remove the scale with rubbing alcohol and a cotton ball. Use an insecticidal soap, or soapy water and a soft cloth.

Spidermites are also common on houseplants and can be identified by the “bronzing” effect that their feeding activity causes and by the existence of clusters of webbing. The spidermites themselves are tiny and hard to see, but the symptoms they cause are obvious.

Spidermites essentially suck the chlorophyll from the plant that causes the foliage to take on a brownish color. Indoor control methods for spidermites include horticultural oils, misting to increase humidity levels (high humidity is unfavorable) or placing the plant in the shower to destroy the webs and knock the mites from the plant.

Fungus gnats are not as common except for those who have plants that require constant moisture and are potted in mixtures high in organic matter. Fungus gnats do not damage the foliage of plants like the other indoor plant pests, but they can prove to be a nuisance if you have an infestation indoors.

When the female gnat is ready to lay her eggs, she is attracted to moist areas high in organic matter. Once the larvae hatch they primarily feed on the organic matter that attracted their mother, but if the source is insufficient, then they may begin feeding on the plant’s roots and root hairs.

Of course the root feeding will cause the plant to wilt, and if it continues, it can kill the plant.

If you have a problem with fungus gnats, an ounce of prevention is worth a pound of cure. Let your houseplants dry out between waterings and use a sterile potting mixture instead of one that is high in organic matter.


Check out gardening columnist Jeneen Wiche’s work at www.SwallowRailFarm.com. You can find her columns also at www.SentinelNews.com/agriculture. She answers questions once a month in SentinelNewsPlus. To submit a question, send an E-mail to jwiche@shelbybb.netand type “Sentinel-News” in the subject field.