Released: February 26, 2004

Check for Scales On Woody Plants

MANHATTAN, Kan. – When horticulturists suggest checking the scales early each year, they’re not talking about weight or New Year’s resolutions.

“One of the best times to check woody plants for scale infestations is during the dormant season. Deciduous plants, at least, won’t have leaves then, so the insects will be easier to see. Plus, a helpful scale control is a dormant oil spray, applied in late winter,” explained Ward Upham, Master Gardener program coordinator for Kansas State University Research and Extension.

Scales are odd insects that are easy to miss seeing, Upham said. They don’t look or act like a typical insect. In fact, some kinds of scale don’t even look much like their scaley kinfolk. But, all scales remain motionless through most of their life – like small bumps on a branch or leaf.

“Many look a bit like a little seashell that’s circular to oval in outline. Some have unusual shapes, including one kind that looks like an oyster shell, several that look like tiny helmets and some that look like small grains of rice. They can even look like the top half of a strange little stuffed olive,” he said. “Their color varies, too, and can include white, yellow, tan, red and brown. They also can have a waxy coating or appear kind of cottony.”

During the growing season, some scales produce a honeydew, which can surround them like a runny eggwhite and drip on cars parked under an infested tree. Often that honeydew attracts ants and supports growth of a sooty mold.

“The plants themselves won’t be harmed so long as just a few scales are present. During the growing season, however, populations of some types of scale can increase dramatically within just a few months,” Upham said. “A heavy infestation can damage fruit crops, destroy branches and even kill entire plants, especially when repeated heavy infestations go unchecked.”

In the High Plains, scale can seem epidemic in Manhattan euonymus, he said. Fruit-producing bushes, apple and crabapple trees, and other fruit trees are susceptible to infestation. Other plants at risk include both deciduous and evergreen landscape staples such as arborvitae, ash, elm, juniper, lilac, linden, maple, oak, pine, spruce and yew.

The U.S. Department of Agriculture’s Forest Service has high-quality photos of various types of scale posted for viewing on the Web at http://www.forestryimages.org/browse/order.cfm?id=Homoptera .

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News