They're tiny, seldom-noticed little pests, but thrips seem to be plaguing flowers in area gardens.

Thrips are small -- less than one-twentieth of an inch long -- and usually go unrecognized as the cause of plant damage. Under magnification, you can see their slender bodies with featherlike wings made of bristles. The ones I find are usually yellowish-tan in color, but thrips can vary in color from yellow to dark brown.

Thrips use rasping mouthparts to feed on plants. This causes blotching and streaking of plant tissues.

The thrips plaguing local gardeners are western flower thrips and gladiolus thrips. They feed within the flower buds, causing stippling and scarring of the petals. If it's a severe infestation, the flower buds won't open. Western flower thrips have a broad host range, but in our area they seem to be particularly troublesome on roses, peonies and hollyhocks. (Gladiolus thrips bother glad flowers and leaves.) They also commonly feed on petunia, impatiens, gerbera, pansy, begonia, fuchsia, chrysanthemum, ivy geranium, marigold, hibiscus, verbena and carnation.

Thrips may also feed on plant leaves, leaving at first a silvery mottling or blotching. Tiny black specks -- feces -- can be seen on the underside of leaves. If leaves are damaged before they emerge from a bud, they will usually fail to develop properly.

Your first clue that your flowers are infested with thrips is the blotchy petals of opened flowers, especially noticeable on lighter-colored blooms. Another clue is the failure of flower buds to open fully or at all. To check for thrips, tap opened flowers over a piece of white paper and look at the specks that fall off. Thrips will move on the paper. On closed blossoms, thrips can be found by tearing open the bud and looking for moving specks at the base of petals.

Recognizing a problem is easier than controlling the pest. Thrips are difficult to manage because they tend to hide deep within buds, protected from most types of insecticide applications, and they are resistant to many pesticides.

Nonchemical options for management include not planting susceptible plants next to weedy or grassy areas where thrips can thrive -- or do a better job of controlling weeds. Regularly spray your plants with water -- this will knock thrips off the plant and will discourage mites. Keep garden plants healthy and vigorous, especially during the hot part of summer. Destroy infested blooms.

Natural predators such as predatory mites, lacewings and pirate bugs help keep thrips in check. If, as a last resort, you apply a pesticide, consider the least toxic, such as those containing spinosad or Beauveria Bassiana. Care should be taken to protect beneficial insects.

Other things you should know about thrips:

-- One of these is insects is called a thrips and a group of them is also called thrips. There is no such thing as "a thrip."

-- Thrips are not powerful fliers, but they will take advantage of wind currents. They also will hitchhike on clothing from one area to another.

-- Thrips also are a problem because they spread at least two plant virus diseases.

-- While it doesn't hurt much, some thrips will bite people. These bites are insignificant.

* Marianne C. Ophardt is a horticulturist for the Washington State University Extension Office in Benton County.