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. 

UPDATE: As mentioned during the previous TSWV Risk Assessment Report, the estimated TSWV Risk was higher than expected this year compared to 2024 for the areas. Remember that predictive models generated during the growing season using the Intensity Predictor Tool become final on May 31st.

Based on our scouting efforts in the last month, we observed a steady increase in TSWV incidence in commercial farms (Table 1). This aligns with the predictions of the Risk Assessment Tools that indicated higher incidence and risk than usual, especially for areas like Whiteville and New Bern, in the last few weeks. This model takes into account last year’s thrips populations and this year’s weather conditions to make its prediction.

Table 1. TSWV incidence in three commercial tobacco fields scouted weekly in NC.

*Number of plants in our last date of scouting pooled dead plants due to TSWV and standing but TSWV infected plants. **4th farm included in 6/5/2025.

TSWV incidence is affected by temperature, rainfall, age of the plants, among other factors, such as disruption of neighboring small-grain fields or weed patches. Disturbance of this fields may exacerbate thrips movement to tobacco fields and contribute to TSWV infections. Despite various areas in the state reported late planting of crops like peanuts and soybeans, which could contribute to the rise on TSWV incidence (15-25% incidence levels), we did not recorded unussually large numbers of thrips on tobacco at our research station in Kinston, NC (Table 2). Large numbers of thrips between 30-50 per leaf have been reported in previous years (2014), but it was not observed in our untreated plots. Generally, when the number of thrips found in the plants is not large, but we continue to observe high incidence of the virus, it indicates that probably there was high abundance of TSWV source plants in the area.

Table 2. Number of thrips per untreated tobacco leaf in research plots at Kinston, NC.

At this point of the season, insecticides sprays solely focused on thrips management are not required as most thrips generations have already dispersed and plant growth has advance in most areas. Beyond six weeks after transplant, tobacco plants become less susceptible to infections. Additionally, symptoms observed in June are likely due to infections from a few weeks ago since it takes the plants 2-3 weeks or more to develop symptoms.

More Information

Tobacco Connection: Vol 2, Num. 2 (Spring 2025 Update).

Tomato Spotted Wilt Virus on Tobacco

Questions About Thrips in Tobacco