Thrips Flight and TSWV Risk Assessment Report – 16 April 2019

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Tomato spotted wilt virus (TSWV) is transmitted by thrips from winter weeds that are host to the virus. Symptoms in tobacco include necrosis and distortion of leaves (Fig. 1). Symptoms are not found in winter weeds hosts, and management requires an integrated approach. Read more information on thrips biology and TSWV transmission.

Tomato spotted wilt virus symptoms in tobacco

Figure 1. TSWV symptoms observed in 2018 in Sampson County, NC. Symptoms of stunting, leaf distortion, and tissue necrosis were found in plants of this field.

Disease incidence in 2017 was higher than observed in previous years due in part to warm winter conditions and spring conditions that extended winter weeds survival longer than normal. TSWV incidence in 2018 was also high in portions of NC, in part due to temperate winter conditions and high inoculum pressure.

As we enter a cool, wet spring in 2019, there is continued concern for TSWV incidence. The New Tobacco TSWV and Thrips Forecasting Tool provides a resource to monitor thrips flights and predict risk of TSWV in a given field. These predictions are based on over 30 years of thrips trapping and weather data to provide an accurate representation of thrips flights.

This post serves to provide a summary of model outputs to date for each location below and suggestions as to how growers might use this information to make management decisions. These predictions will improve closer to actual transplant dates, and the most recent information should be used for management decisions.

Kenly is a relatively low TSWV risk site, situated within large acreage production areas in Johnston and Wilson Counties. As of today, TSWV infection risk in Kenly is slightly higher than last year. The third generation tobacco thrips flight (the generation that typically transmits the most TSWV) is not expected to occur during the next 14 days. 

Beulaville is a higher TSWV risk site in Duplin County. As of today, TSWV infection risk in Beulaville is is slightly higher than last year. The third generation tobacco thrips flight is not expected to occur during the next 14 days.

Kinston is a moderate TSWV risk site in Lenior County and also houses the N.C. Department of Agriculture & Consumer Services Cunningham Research Station where we conduct tobacco research. As of today, TSWV infection risk in Kinston is slightly higher than last year. The third generation tobacco thrips flight is not expected to occur during the next 14 days.

New Bern is a higher TSWV risk site. As of today, TSWV infection risk in Kinston is similar to last year. The third generation tobacco thrips flight is not expected to occur during the next 14 days.

Windsor is a higher TSWV risk site. As of today, TSWV infection risk in Windsor is similar to last year.The third generation tobacco thrips flight is not expected to occur during the next 14 days.

Whiteville is a moderate TSWV risk site in Columbus County and also houses the NCDA&CS Border Belt Tobacco Research Station where we conduct tobacco research. As of today, TSWV infection risk in Whiteville is is slightly higher than last year. The third generation tobacco thrips flight is not expected to occur during the next 14 days. 

Carthage is a relatively low TSWV risk site in Moore County. As of today, TSWV infection risk in Carthage is similar to last year. The third generation tobacco thrips flight is not expected to occur during the next 14 days.

In order to get the most accurate risk assessment, we recommend you enter your own farm data into the TSWV and Tobacco Thrips Risk Forecasting Tool. The following information is needed:

1. Field location (address, coordinates, nearest ZIP code, or selected from a map)

2. TSWV infection percentage in a typical year at this location

In addition, you can provide the following optional information which will improve recommendations:

3. Anticipated planting date

4. Greenhouse applications of imidacloprid and/or Actigard

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