The Backyard Jungle

Enlarge Image Image Gallery The banded greenhouse thrips (Hercinothrips femoralis) is one of several species that feed on the foliage of garden plants. Inset: Thrips dance about on a datura petal.

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Here's the fourteenth in a series of articles that will help you tell friend from foe in your garden.

Part XIV: Thrips

One of the most common pests found on flowers, vegetables, and fruit has one of the least commonly known names in the insect world . . . thrips . (One thrips or a hundred, the s stays on.) Perhaps this creature has been able to maintain a certain degree of anonymity because of its minute size; unless your eyes are exceptionally sharp, you'll need a magnifying glass just to spot a thrips.

Under magnification, thrips aren't easily confused with other tiny garden pests. In addition to their slim bodies and brown, black, or yellow coloration, thrips have unusually slender wings fringed with microscopic hairs. Indeed, the name of the order to which the various species of thrips belong (Thysanoptera) means "fringed wings."

If you spot one thrips, you'll likely spot dozens or even hundreds; they're sociable little creatures. Several generations of thrips may hatch annually, and with the help of mild winter and spring temperatures, thrips populations can easily build to infestation proportions.

These Lilliputian plant feeders dine by rasping their host plant's epidermis until it weeps, then sucking the juices. This abrasive manner of feeding results in stippling, streaking, and other forms of distortion of the host plant. For the most part, though, thrips damage is tolerable, often superficial rather than actually threatening to the health of the host plant.

There are a great many species of thrips that attack flowers, one of the most notorious being the citrus thrips (Scirtothrips citri), which leaves brown rings on the ends of fruit. These circular blemishes in no way diminish the quality of the fruit, but since American consumers have been conditioned to expect near-perfect-looking citrus, such discolored fruit is usually downgraded and processed for juice. For the home citrus grower, however, thrips damage is usually bearable.

The most destructive species of thrips are those that feed on foliage—and many species in this group are common in the home garden. The onion thrips (Thrips tabaci) attacks various alliums (onions, garlic, etc.) as well as carrots, beans, peas, and other vegetables.

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