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: Predictive models for the locations below continue to indicate lower estimated TSWV Risk this year than the historical average for Kenly (3.6%), Kinston (5.7%), and New Bern (6.6% ), while slightly higher risk in the Whiteville area (10.8%). The 3rd generation of tobacco thrips began to disperse in Whiteville last week (~May 5) and dispersed at the beginning of this week for the Kinston and New Bern areas. In these areas, the 4th generation of thrips is expected to begin dispersing in approximately two weeks from now, by the end of May. In the Kenly area, the 3rd generation of thrips is expected to begin dispersing by the end of this week (~May 17), followed by the 4th generation two weeks after, in early June.
Because the third AND fourth generations of tobacco thrips are the ones that typically transmit the most TSWV, seedlings transplanted in late April (3rd and 4th week) are more at risk of TSWV infection than the ones transplanted before mid-April. Be aware that it takes approximately four weeks from the time a plant is infected with TSWV until the symptoms appear. Thus, symptoms of TSWV infection will probably show up this week and next week for early planted fields (1st-2nd week of April).
A greenhouse application of imidacloprid alone or combined with Actigard® at transplant or greenhouse is recommended to minimize potential losses to TSWV. If imidacloprid was not applied in the greenhouse before planting or at transplant, foliar applications of imidacloprid can be can conducted to product against TSWV. If foliar applications of Actigard® are being considered (post transplant), the sooner plants are treated the better since it takes a few days for the product to be effective and can provide protection for ~two weeks (depending on environmental conditions). Treatment in addition to standard insecticides is probably not required for areas with a history of <10% TSWV incidence. See the NC Agricultural Chemicals Manual and the NC Flue Cured and Burley Tobacco Guide for details on TSWV management practices.
This update was compiled based on Thrips Flight and TSWV Risk Assessments conducted for the four key tobacco-growing locations in NC included below. These models were created assuming no insecticide treatment and including the average historical TSWV incidence for each location as listed below (Fig. 8.1 modified from Mina, 2011).- 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.
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