Western Flower Thrips

Western Flower Thrips in Greenhouses- from Dr. Stephen Franks, NCSU Dept of Entomology

Thrips are a constant problem for growers. Not just this particular week, but all the time. Western flower thrips, Frankliniella occidentalis, is the most important and damaging thrips of greenhouses and has been called the most damaging greenhouse pest in the world. This is true of greenhouse-grown food and ornamental crops. Nearly all floriculture crops are susceptible to thrips damage. Western flower thrips reproduce rapidly and are difficult to manage because they live in the cracks and crevices of flower heads and foliage. Thus they are difficult to contact with insecticides. Western flower thrips also develop insecticide resistance rapidly so it is important to emphasize chemical rotation and to have a resistance management plan. Sanitation is also very important in managing thrips. Because they can feed and reproduce on hundreds of plant species, weeds in and around a greenhouse will provide a constant supply of thrips even if the crop is sprayed. Western flower thrips pupate in soil, so clean up spilled potting soil and other debris to deny them this vital part of their lifecycle. More information and chemical recommendations can be found in the newly-revised Ornamentals and Turf Insect Note No. 72 at Western Flower Thrips

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.

Pest to Monitor: Flower Thrips-

The eastern flower thrips, Frankliniella tritici, feeds mainly on flowers and fortunately is not known to vector any virus. Because of their tiny size, flower thrips are carried over large areas by wind systems. Flower thrips are found throughout North Carolina with peak migration early to mid June. They have been found on dozens of hosts. Control of flower thrips is difficult because of constant migration from weeds, grass, flowers and trees. They are also known to make a mild, but noticeable "nip" to the skin.

The first step in management is to eliminate as many weeds in the area as possible, or keep them mowed so they do not flower. To protect flowers, homeowners might use products such as neem or Mavrik. Pyrethrin insecticides might be used before blossoms open to protect pollinators. The commercial industry should rotate chemicals to reduce concern of resistance. They might use products such as Conserve, Pedestal, Azatin (or Ornazin) and BotaniGard. Monitoring for thrips with yellow sticky cards can also help detect populations as they are increasing, allowing controls to be started before substantial plant damage. Note from Dr. Stephen Bambara

For more information on flower thrips, see Ornamental and Turf Insect Note No. 21 at Thrips


For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.