Fungicides Late Blight Potato Tomatoes

Current late blight risk in Ontario field tomatoes: July 20, 2019

image depicting two spore trapping styles. The funnel-like passive Spornado spore trap and the active rotorod spore trap.

By: Cheryl Trueman, Department of Plant Agriculture, Ridgetown Campus – University of Guelph

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, along with the BliteCast forecasting model. This week, DNA of Phytophthora infestans spores, the organism that causes late blight, was detected at 1 of 8 sites for the July 15-18 sampling period.

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 (, 519-350-7134) or Cheryl Trueman (, 519-674-1500 x63646) to confirm the diagnosis.

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

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

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