Thrips Flight and TSWV Risk Assessment Report – April 23, 2025
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Collapse ▲To help growers determine the potential of management practices for TSWV, we have created step-by-step guides on how to use the Tobacco Thrips Flight and TSWV Intensity Predictor to create Current Year TSWV Risk Assessments and Historical TSWV Predictions. Growers are strongly encouraged to create their own models using the information from their fields and season dates to plan for Tomato Spotted Wilt Virus (TSWV) management.
TSWV incidence was higher in 2024 than in previous years, possibly due to warm winter temperatures and spring conditions that maintained winter weed hosts of thrips longer than typical. This year, the 2025 TSWV incidence is expected to be lower than in 2024. However, the first two thrips flights happened approximately two weeks earlier than in 2024. Additionally, low rainfall during the spring and early summer could still contribute (in part) to thrips population increase.
Thrips Flight and TSWV Risk Assessments were conducted for four key tobacco-growing locations in NC:
- Kenly is a relatively low TSWV risk site (typically less than 8%), situated within large acreage production areas in Johnston and Wilson Counties.
- Kinston is a moderate TSWV risk site (typically less than 10%) in Lenoir County and also houses the NCDA & CS Cunningham Research Station, where extensive tobacco research is conducted.
- New Bern is a higher TSWV risk site (typically above 10%) in Craven County.
- Whiteville is a moderate to high TSWV risk site (around 8% or above 10%) in Columbus County and also houses the NCDA & CS Border Belt Tobacco Research Station where tobacco research is conducted.
For all these locations, the 3rd generation of tobacco thrips is expected to begin dispersing this week, as early as April 22 in Whiteville and late in the week as April 24 in Kenly. Following closely, the 4th generation of tobacco thrips is expected to begin dispersing as soon as this upcoming week (April 26) and early next week. Growers scheduled to transplant this week or next week, as well as growers that didn’t treat at greenhouse or during transplant, need to take precautions against these upcoming populations.
A greenhouse application of imidacloprid in combination with Actigard® is recommended to minimize potential losses to TSWV. If foliar applications of Actigard® are being considered, the sooner transplants are treated the better since it takes time for the product to be effective.
The third generation tobacco thrips flight is the generation that typically transmits the most TSWV.
Historically, thrips population flights were reported in the second week of May in most tobacco production areas in NC, but in the last few years we are having earlier flight and can continue to be the case in upcoming years. This means the populations are maturing faster than expected. We need to accommodate to these populations changes and start scouting and using the prediction tool earlier every year to protect tobacco transplants.
These models were created assuming no insecticide treatment and including the average historical TSWV incidence for each location (Fig. 8.1 included below from Mina, 2011).
The models used for this summary are attached below for your reference. 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 and check for any updates frequently.
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