Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern & Central Midwest
February, 2013
Regional Report

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These hard-shelled bumps are scales on a jade plant.

Watch out for House Plant Pests

I've had my bay laurel for about ten years, and I dutifully bring it indoors in winter and take it out to summer outdoors. I do this specifically because it always has scale insects, and taking it out for summer means the predators take care of the insect populations. By the time the populations climb to unacceptable levels, it's time to go outside for the summer where nature can go to work.

Stressed Plants Ripe for Pests
This is a good example of what can happen to a plant that lives in a stressful situation. My bay laurel is in a dry, warm home in winter, quite unlike its native cool Mediterranean winter home. Any time a plant is stressed, it is target for soaring pest populations. Insect pests tend to stay in check if a plant is in good health and is getting the care it needs. But as with my bay laurel, all it takes is heat and low humidity for a brief time to bring on the insects. Or all it takes for fungus gnats to have a population boom is to overwater a plant a few times.

Knowing what pest damage looks like will help you diagnose your pest populations. You can then work to reduce them. In most cases, the best and safest tool you can have in your arsenal is a strong spray of water. Horticultural oil and insecticidal soap are two products you should keep handy.

Spider Mites
These tiny spiders are plant-sucking pests, and they love dry, dusty conditions. A plant's leaves may start looking pale, and if you look closely, you will notice stippling or tiny yellow dots. The mites themselves are hard to see, but if you tap the leaf over a piece of white paper, tiny moving specks fall onto it are usually mites. Bad infestations will eventually show webbing on the undersides of the leaves.

These insects have two life stages, an immature crawling stage and a mature stage in which the insect is settled beneath a waxy shell. Indications of scales are sticky sap and black mildew on the leaves. Scales are hard to wash off, but horticultural oil works beautifully to smother them.

Fungus Gnats
These pesky flying pests indicate overwatering. The mature fliers do no harm, but the larvae feed on plant roots. Simply drying a plant out for several weeks often takes care of the problem.

White cottony masses in the leaf axils are usually mealybugs. They also suck plant sap, and can usually be controlled by dabbing them with a cotton swab dipped in alcohol or horticultural oil.

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