Thrips Flight and TSWV Risk Assessment Report – May 18, 2020

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This is the seventh of our weekly TSWV and tobacco thrips risk assessment updates. Third generation flights have now begun at 2 of our 8 report locations, which impacts management choices. We may also need to consider management efforts for fourth-generation flights at some of these locations considering the slow start much of the crop has gotten. Fields planted within a month of the fourth generation flight may warrant additional attention. 

Managing tomato spotted wilt virus (TSWV) in North Carolina tobacco requires both pre-transplant and post-transplant decisions, which are most effective when timed to thrips movement into tobacco fields. The winter of 2019/2020 was historically mild which raises concerns about increased infection due to greater survival and reproduction of thrips vectors of TSWV.

In order to give growers a sense of TSWV risk moving into 2020 transplant, we will be producing weekly reports from the TSWV and Tobacco Thrips Risk Forecasting Tool for selected locations in eastern NC where TSWV may be problematic. In these posts, we’ll provide a summary of model outputs to date for each location and suggestions as to how growers might use this information to make management decisions. These predictions will improve as we get closer to transplant dates, and growers should use the most recent information to make management decisions! Growers are also encouraged to look at predictions more frequently than weekly as they get close to transplant.

The information presented here is intended to supplement, but not replace, farm-specific predictions. In order to generate data for your farm, the following information is required:

1. Field location, selected on 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

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 somewhat higher than a typical year. Last year the third generation thrips flight occurred on May 24. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) is expected to begin on May 27. Because Kenly is a lower risk location, additional treatments against TSWV are not recommended here. Growers who are interested in making additional treatments against TSWV should consult their local Extension agent for recommendations or contact Hannah.

Keanansville is a higher TSWV risk site in Duplin County. As of today, TSWV infection risk in Keanansville is higher than a typical year. The third generation tobacco thrips flight typically transmits the most TSWV. Last year the third generation thrips flight occurred on May 16. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) began on May 16Because the flight has already begun, additional field applications of Actigard at this time will be less effective. The fourth-generation thrips flight is predicted for June 4, and late-planted tobacco may also benefit from protection against this generation as well. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.

Kinston is a moderate TSWV risk site in Lenior County and also houses the N.C. Department of Agriculture and Consumer Services (NCDA&CS) Cunningham Research Station where we conduct tobacco research. As of today, TSWV infection risk in Kinston is slightly higher than a typical year. Last year the third generation thrips flight occurred on May 17. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV)  began on May 18. Greenhouse float water treatments of Actigard are effective for up to two weeks post-transplant. Growers who are interesting in taking additional action against TSWV who have not transplanted yet should consider greenhouse applications of Actigard. Because the flight has already begun, additional field applications of Actigard at this time will be less effective. The fourth-generation thrips flight is predicted for June 6, and late-planted tobacco may also benefit from protection against this generation as well. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.

New Bern is a higher TSWV risk site. As of today, TSWV infection risk in New Bern is higher than in a typical year. Last year the third generation thrips flight occurred on May 10. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) began on May 9. Greenhouse float water treatments of Actigard are effective for up to two weeks post-transplant. Because the flight has already begun, additional field applications of Actigard at this time will be less effective. The fourth-generation thrips flight is predicted for May 31, and late-planted tobacco may also benefit from protection against this generation as well. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.

Windsor is a moderate TSWV risk site. As of today, TSWV infection risk in Windsor is slights higher than in a typical year. Last year the third generation thrips flight occurred on May 19. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) is expected to begin on May 27. Greenhouse float water treatments of Actigard are effective for up to two weeks post-transplant. Growers who are interesting in taking additional action against TSWV and will be transplanting May 13 or later should consider greenhouse applications of Actigard. Growers who planted earlier than May 13 should consider making a foliar application of Actigard 2 to 3 days prior to May 27. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.

Whiteville is a higher 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 about the same as in a typical year. Last year the third generation thrips flight occurred on May 9. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) was expected to begin on May 4. Greenhouse float water treatments of Actigard are effective for up to two weeks post-transplant and would not be recommended for growers who have not already transplanted. Because the flight has already begun, additional field applications of Actigard at this time will be less effective. The fourth-generation thrips flight is predicted for May 28, and late-planted tobacco may also benefit from protection against this generation as well. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.

Clinton is a higher TSWV risk site in Sampson County. As of today, TSWV infection risk in Clinton is slightly higher than in a typical year. Last year the third generation thrips flight occurred on May 14. This year, the third generation tobacco thrips flight (the generation that typically transmits the most TSWV) began on May 16. Greenhouse float water treatments of Actigard are effective for up to two weeks post-transplant and would not be recommended for growers who have not already transplanted. Because the flight has already begun, additional field applications of Actigard at this time will be less effective. The fourth-generation thrips flight is predicted for June 3, and late-planted tobacco may also benefit from protection against this generation as well. Growers should consult their local Extension agent for recommendations or contact Hannah for more information.