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Plant Protection - Western Flower Thrips (Tech Tip )
By Marla Faver, Syngenta Technical Services

Western Flower Thrips (WFT - Frankliniella occidentalis) are often a problem year after year in greenhouse production. They are tough to manage during all crop growing stages, but even more so when crops are flowering. They can be very difficult to control due to their preference for tight dark places, particularly in flowers and buds. It is often challenging to reach these small tight places with pest control materials. WFT prefer feeding on pollen, young foliage, flowers, and buds and this feeding can cause curled, distorted, puckered and chlorotic foliage. Typically irregular white spots form and the leaf surface may appear silvery or stippled. WFT feeding also causes new growth and flowers to be deformed and discolored with feeding scars. WFT also have the ability to transmit viruses such as impatiens necrotic spot virus (INSV) & tomato spotted wilt virus (TSWV).

Start control measures early and use an integrated approach to reduce the chance of crop injury and prevent high populations from building. Listed here are some of the basic control strategies that should be implemented;

  • Inspect new shipments of plants and remove or treat plants that contain thrips.
  • Start with a clean growing area. Old plant material and "pet" plants are a perfect place for thrips to hide out between crops. Remove stock plants and old flowers from the growing area. These may also serve as a reservoir for viruses spread by thrips. Be sure to control weeds in and around the greenhouse.
  • Use screening on doors and vents to help prevent thrips from moving into the greenhouse from outside crops or weeds.
  • Inspect crops regularly for the presence of thrips and physical damage caused by their feeding. Use sticky cards to monitor populations early in the crop cycle before flowers or buds are present. Use Thripline™ ams pheromone lure with your sticky cards to increase thrips movement giving an earlier and more accurate population assessment.
  • Proper use of chemical controls.

    o Begin spray rotations when populations are low and before flowers or buds are present.
    o First apply products that have activity on adults and immature stages such as Avid® 0.15 EC insecticide/miticide then rotate to an insect growth regulator followed by an appropriate rotational program including Scimitar® GC and Flagship® 25WG insecticides on foliar feeding thrips.
    o Check spray coverage as this is often a factor limiting control with pesticide applications. The use of water sensitive spray paper will aid in the evaluation of proper spray coverage. A periodic change in the spray or application pattern changes the spray angles and allows improved spray coverage. Always follow directions on the product label including appropriate use rates, application restrictions and plant safety.


Rate /100 gal

Scimitar GC 5 oz
Flagship 25WG (foliar) 4.5 - 8 oz/100 gal, 8 -17 oz/A
Flagship 25WG (soil) 4.5 - 8 oz/100 gal, 8 -17 oz/A
Avid 0.15 EC 8 oz
Thripline 1 lure/1,000 ft sq

The use of biological control agents (BCAs) is an excellent tool for an Integrated Crop Management (ICM) program. Implementing an integrated approach provides more options to control thrips populations.


Pest stage BCA feeds on

Hypoline™ m Hypoaspis miles (beneficial mite) Thrips pre-pupae and pupae
Exhibitline™ sf Steinernema feltiae (beneficial nematode) Thrips pre-pupae and pupae
Swirskiline™ as Amblyseius swirskii (beneficial mite) Smallest thrips larvae, whiteflies, pollen or mold
Amblyline™ cu Amblyseius cucumeris (beneficial mite) Smallest thrips larvae,Tarsonemid and Eriophyid mites
Oriline™ i Orius insidiosus (predatory bug) Voracious predator on multiple pest species, pollen

©2014 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your state or local extension service to ensure registration status. Scimitar® GC is a Restricted Use Pesticide. Amblyline™, Avid®, Exhibitline ™, Flagship®, Hypoline™, Oriline™, Swirskiline™, Scimitar® , Thripline™, and the Syngenta logo are registered trademarks of a Syngenta Group Company.

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