Biology and Insecticide Management for

Western Flower Thrips James A. Bethke

University of California Cooperative Extension

Western Flower Thrips • Probably the most serious pest of ornamentals in

greenhouses - Parrella 1995

• IR-4 considers this pest number one most years for research in ornamentals

• Efficient vector for many Tospviruses, TSWV, INSV

• Direct damage to buds and flowers, usually damaged much earlier

Impact on the Greenhouse Industry

TSWV - Tomato spotted wilt virus

Leaf, Flower/Petal Damage

INSV

Impatiens necrotic spot virus

The Most Common Causes of Pesticide Failure

Failure to implement IPM program Failure to monitor Misidentification of pest Wrong choice of pesticide Incorrect rates/off label use/old pesticide Water quality/pH/adjuvants/tank mixes Misuse of or poor calibration of equipment Inadequate coverage or placement of pesticide Great numbers or resistant populations

Effective sprays • Scouting

• Early detection

• Proper identification of the pest

• Minimize frequency of application

• Avoid tank mixes

• Rotate the mode of action

• Use a more integrated approach

Sticky Cards

- white, yellow or blue stick cards are attractive to thrips adults - trap above crop height - 1 trap/10,000 square ft. in doors; 1 trap/4 acres outdoors - place near sensitive plants, vents, doors - count/record trap data weekly - plot catches vs treatments to evaluate

Weed Control

Chickweed is also an indicator plant but also a harbor for pests and disease

Econet T Econet L

No Thrip Antivirus Screen

Conserve (Spinosad) • Arguably one of the best products for thrips control • 6ppm can cause 100% mortality to susceptible thrips • Some formulations are registered as ‘organic’ • Provides a unique mode of action

Dow & Conserve Resistance

• Great concern • Monitoring program using coated vial method (IOBC) • Thrips on roses in CA, 2002 • Survey of growers from San Diego to Watsonville • Most populations were very sensitive

Recent Assays

Recent Assays

Western Flower Thrips • Frankliniella occidentalis • Very small - Thigmotactic • Damage resembles mites, fecal flecks, terminal or leaf distortion, Tospoviruses • Monitor with sticky cards • Female WFT lay 130–230 eggs • Multiple genes for resistance • IR4 has been concentrating on thrips products for many years

Thrips Biology

Thrips Biology: Disease Transmission

Susceptible stages

Consider the Risk Save the most effective product(s) for the

time of year or cropping cycle with the most risk

• When no. of pest are most prevalent

• When the crop is the most susceptible

Use rotations with softer products or chemicals that are suppressive during the least risk

Example - Thrips The most effective products are Conserve

Pylon and Avid, so do not use these at any time during the year or cropping cycle when there is low risk

This ensures the products effectiveness as a cleanup product or preventive during high risk

Use soft products or suppressive products during the cooler times of the year when thrips are less likely to be present

Consider Other Pests Thrips and leafminers then never use Conserve for

leafminers

Thrips and mites then never use Avid for thrips

Low risk – Soap or Oil or IGR>BotaniGard>pyrethroid>OP

High risk - Conserve>Pylon>Avid>Overture>pyrethroid+OP

These rotations are appropriate as products with different modes of action are being used every two weeks.

IRAC Recommendation for Rotational Scheme

MoA = Mode of Action

w, x, y, and z are modes of action from the IRAC MoA chart

http://mrec.ifas.ufl.edu/lso/DOCUMENTS/ThripsManagementProgram-February%202011-FINAL.pdf

http://mrec.ifas.ufl.edu/lso/DOCUMENTS/ThripsManagementProgram-February%202011-FINAL.pdf

James A. Bethke UCCE San Diego

9225 Hazard Way, Suite 201 San Diego, CA 92123

jabethke@ucanr.edu Cell: 951-775-7172