Controlling insects on indoor plants

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Have you noticed a sticky substance on the floor beneath your ficus or philodendron? Are there little scabs on the under side of the leaves of your orchid?  Maybe you have noticed that your plants just look a little lack luster. Well, we can blame some plant puniness on being a tropical houseplant indoors in Kentuckiana during the winter.
Low light, humidity
Low levels of humidity and low levels of light trigger a response in plants that slows them down for the winter.  They shed foliage and basically standby until the environment turns more favorable. However, another reality of being a houseplant is that you are susceptible to a handful of insect problems.
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, that’s actually honeydew. Honeydew is a nice way of saying bug poop.  The yellowing or shedding of leaves is another indicator of an insect problem (but, it is also not uncommon in the winter as light levels drop).
Sucking scales
Many of the insects that feed on our indoor plants are considered sucking insects and the worst of the offenders are called scales. 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 include distorted, yellowing foliage and an overall pale as the scales suck the juices from the plant.
Oil and pruning
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.
Tiny spidermites
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
Fungus gnats are not as common, except for those 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 them they may begin feeding on the plant’s roots and root hairs.  
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.
(Jeneen Wiche is an avid gardener from Shelbyville. She can be reached at www.JWiche@shelbybb.net.)