Western Flower Thrips (WFTs - 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, particularly in flowers and buds due to their preference for tight, dark places. WFTs prefer feeding on pollen, young foliage, flowers and buds. Feeding can cause curled, distorted, puckered and chlorotic foliage. Typically, irregular white spots form, and the leaf surface may appear silvery or have a stippled appearance. New growth and flowers typically are deformed and discolored with feeding scars. WFTs also have the ability to transmit viruses such as impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV).

 

To reduce the chance of high populations of WFTs resulting in crop injury, start control measures early and use an integrated approach. Listed below are basic thrips control strategies:

 

§  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 leftover plants from the growing area. These can serve as not only as hosts for thrips but also as reservoirs for viruses spread by thrips. Be sure to control weeds in and around the perimeter of the greenhouse.

§  Screening (opening size < 200 microns) on doors and vents can 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. Include Thripline^™ ams pheromone lure from Bioline^™ pest control products with your sticky cards to increase thrips movement, which will provide 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 are effective on adults and immature stages such as Avid^® miticide/insecticide, and then rotate to an insect growth regulator following an appropriate rotational program such as Scimitar^® GC insecticide and Flagship^® 25WG insecticide on foliar-feeding thrips.

o    Check spray coverage as this is often the factor that can hinder control of pesticide applications. Using water-sensitive spray paper will aid in the evaluation of proper spray coverage.

 

In addition to WFTs, whiteflies are also significant pests for many flowers and nursery crops. The two most common whitefly species that infest greenhouse and outdoor nursery crops are the greenhouse whitefly (Trialeurodes vaporariorum) and the silverleaf whitefly (Bemisia tabaci). The adults and immature stages have piercing/sucking mouthparts, which are inserted in the phloem and extract plant sap. Injury is generally observed as chlorotic plant tissue and black sooty mold growing on the honeydew-excretions of the whiteflies. Large populations of whiteflies can cause stunting of plant growth and senescence of leaves.

The best whitefly control strategies depend on life stage, spray coverage and application timing. Using a neonicotinoid such as Flagship 25WG is the backbone of a successful control strategy. Including Flagship in a rotational program is an excellent tool for whitefly control, especially if used as a drench!! Avid and Endeavor^® insecticides are also terrific materials to incorporate into a whitefly control program.

The key is to start control measures early and use an integrated approach. Listed below are basic control measures that should be implemented:

§  Maintain weed-free production areas. Whiteflies feed on numerous hosts, so eliminate potential sites of contamination.

§  Inspect new shipments of plants and remove or treat plants that are harboring whiteflies.

§  Monitor openings in greenhouses to help exclude populations because adults are mobile.

§  Monitor egg and nymph populations by checking the undersides of leaves with a hand lens. If immature pests are present, Avid and Endeavor are appropriate treatments. Check for adults with yellow sticky cards. Flagship is an appropriate application for all feeding stages. Treatment threshold levels depend on crop, product applied and the experience of the grower.

§  Rotate insecticides with different modes of action to manage resistance. Use the appropriate water volume to cover the underside of plant leaves. In some cases, an adjuvant may be needed. Systemic materials, such as Flagship, have longer residual activity when used as a drench.

 

Pesticide Application Rates

Product	Rate /100 gal
Endeavor	5 oz
Flagship (foliar)	4.5 - 8 oz/100 gal, 8 -17 oz/A
Flagship (soil)	4.5 - 8 oz/100 gal, 8 - 17 oz/A
Avid	8 oz
Thripline ams	1 lure/1000 ft sq

 

A periodical change in the spray or application pattern changes the spray angles and allows improved spray coverage.

 

© 2012 Syngenta. Important: Always read and follow label instructions before buying or using Syngenta products. The label contains important conditions of sale, including limitations of warranty and remedy. All products may not be registered for sale or use in all states. Please check with your state or local extension service before buying or using Syngenta products. Scimitar^® GC is a Restricted Use Pesticide. Avid^®, Bioline™, Endeavor^®, Flagship^®, Scimitar^®, Thripline^™ and the Syngenta logo are trademarks of a Syngenta Group Company.