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United States Department of Agriculture

Agricultural Research Service

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Close-up of several invasive scale insects of the species Pseudococcus calceolariae. Click the image for additional information about it.
These invasive scale insects, Citrophilus mealybugs (Pseudococcus calceolariae), when disturbed, secrete a red liquid as a means of defense. Note the two droplets on the large mealybug in the center.  Click the image for additional information about it.

Read the magazine story to find out more.

On the Front Lines Against Scaley Invaders

By Luis Pons
December 9, 2003

They're small. They're messy. They're—well, scaley!

They are scale insects, and many gardeners know how hard it is to keep them at bay. Imagine trying to keep them out of the country.

Yet that is the mission in which Agricultural Research Service entomologist Douglass Miller plays a large role. Based at the ARS Systematic Entomology Laboratory in Beltsville, Md., Miller is the lab's scale insect expert. He's routinely called on to identify scales suspected of being invaders from other parts of the world. Miller is often the first to tell whether a scale species is new to the United States, or perhaps new to the list of known insects.

Scale insects are among the nation's most destructive pests, mostly because they often go undetected until they've become established and caused damage. They devastate nut and fruit trees, greenhouse plants, forest vegetation, woody ornamentals and houseplants. Their best-known calling card is a sticky, sweet substance called honeydew that many secrete while feeding. The most common scale insects are identifiable by the hard, scaley cover that is their natural protection. Others are covered by mealy waxes that come in a variety of colors.

According to Miller, the national cost of control efforts and damage repair related to scale insects reaches up to $500 million annually. At least 1,000 species can already be found in the United States, 253 of which are invasive.

Miller has monitored scales for ARS for 34 years. He and fellow ARS entomologist Gary Miller developed another tool for combating scales: the first known full inventory of them. This inventory is part of ScaleNet, an ARS-run Internet database that allows users to gather information about scales. ScaleNet is accessible at:

You can read more about the research on scale insects in the December issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

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