What are thrips?
 Thrips* are tiny (1-2 mm, about the size of a spider mite) insects with thin, feathery wings (right). Most thrips feed on plants but some species are predatory. Thrips feeding injury often appears as sunken, silvery patches on leaf surfaces.
Plant-feeding thrips develop from eggs through several immature stages to a pupal stage then emerge as adults. Eggs are laid in leaf tissue, larvae feed on leaves and the pupal stage often occurs off the plant in soil. There are multiple generations of thrips each year so populations can build rapidly to damaging levels. The generation time from egg to egg can be as little as two weeks.
Some thrips transmit an important plant virus while feeding. The virus, called tomato spotted wilt virus (impatiens necrotic spot virus), is lethal to a wide range of ornamental and garden plants. Commercial growers, therefore, often have zero tolerance for thrips in their greenhouses.
Use vent screens to protect greenhouses
Thrips usually enter greenhouses through open vents. Many large, commercial greenhouse growers now use fine mesh screens to prevent thrips entry. Screening vents, however, will slow air flow so additional vent area may be needed.
* Thrips is always plural, one thrips or many thrips. Common misspelling: thrip
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| western flower thrips (magnified) with wings folded across back; large green tube is a leaf vein |
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adult thrips, larvae are similar minus the feathered wings and a smaller body size
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and the yellow traps are much easier to find. Use a minimum of 1-2 traps per 1000 square feet of greenhouse. Check traps every 2 or 3 days. Traps will capture winged