ALERT: Immediate Action Needed for Thrips/TSWR

ALERT: Immediate Action Needed for Thrips/TSWR

May 4, 2014

Source: Neil McRoberts

For those who have water and tomatoes:

 

Thrips numbers have increased rapidly in the southern arm of the Central Valley and Tomato spotted wilt virus (TSWV) has been reported in all of the areas we monitor,” according to Neil McRoberts, Assistant Professor, Plant Pathology Department, UC Davis.

There are numerous reports of TSWV symptoms in crops from Stanislaus County down to Fresno and Kings County particularly around the Huron area.

 

The current risk in Fresno County is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 17th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.  This means you need to take immediate action.

Generation 4 adults are projected to peak on June 11th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in the Merced area is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

Generation 3 adults are projected to peak on May 22nd.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 16th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in eastern San Joaquin County is lower than in other southern Counties, but we think a precautionary approach is best. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 28th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 22nd.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.

 

The current risk in Kings County is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 22nd.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.  This means you need to take immediate action.

Generation 4 adults are projected to peak on June 14th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in western San Joaquin County is lower than in other southern counties, but we think a precautionary approach is best. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4.

Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 28th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 22nd.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.

 

The web resource for integrated management of Western Flower Thrips and Tomato Spotted Wilt Virus in the California Central Valley contains two tools to help in disease risk management:  

A Field Risk Index tool uses simple information about field locations, land use, and agronomy to calculate a risk category for tomato crops.  This tool can be used before planting or early in the season to get a heads up about the general risk to a crop from TSWV.

A thrips population projection model, driven by degree-day accumulation at several Central Valley locations, aids in projecting when thrips generations are hatching, developing, and adult numbers are peaking.  This information is used to issue regular updates and provide broad guidelines for timing insecticide sprays to keep thrips numbers low enough to prevent TSWV from spreading.

The research behind these tools was supported by the California Tomato Research Institute (CTRI)

The model was developed in Collaboration with Dr. Len Coop of Oregon State University’s Integrated Plant Protection Center (IPPC).  The IPPC developed and hosts the USPEST web service which is a multi pest multi model tool that provides information on pest development and disease risk for the Contiguous 48 US states using a network of weather stations.

 

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