Current late blight risk in Ontario field tomatoes: September 4, 2019

By: Amanda Tracey, Vegetable Crops Specialist, OMAFRA, Ridgetown and Cheryl Trueman, Department of Plant Agriculture, Ridgetown Campus – University of Guelph

With tomato harvest in full swing, it is time to wrap up the late blight spore trapping for this growing season.

As mentioned in a previous post, this is Year 1 of a three-year research project to assess the value of different spore traps and forecasting models to predict late blight risk for field tomatoes. We are comparing the Spornado and rotorod spore traps at eight sites in Kent County (Fig. 1), along with the BliteCast forecasting model.
DNA of Phytophthora infestans, the organism that causes late blight, was detected by Spornado traps at 3 of 8 sites for the August 26-29 sampling period (Table 1).
Rotorod traps detected spores of P. infestans at 0 of 8 sites for the August 26-29 sampling period (Table 1).

Late blight symptoms have been confirmed on a potato plants in Norfolk County.

Late blight caused by the US-23 genotype has been observed in Wisconsin on potato and in New York and Pennsylvania on tomato and potato. Pennsylvania on tomato, but there are no reports of symptoms on any crops in Ontario or Michigan.

A summary of fungicides for late blight management is available here.

If you suspect late blight in your tomato crop, please reach out to Amanda Tracey (Amanda.tracey@ontario.ca, 519-350-7134) to confirm the diagnosis. Cheryl is away on parental leave and will not be available for the remainder of the growing season.

Project collaborators: Tomecek Agronomic Services, Sporometrics, Phytodata, and Genevieve Marchand (AAFC).

Funding acknowledgement: Ontario Tomato Research Institute, Fresh Vegetable Growers of Ontario, and the Ontario Agri-Food Innovation Alliance.

Links to previous late blight posts from the 2019 season: June 20, July 10, July 20, August 7, August 14, August 21, August 28.