Disease Late Blight Tomatoes

Current late blight risk in Ontario field tomatoes: July 10, 2019

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 (Fig. 1), along with the BliteCast forecasting model.

So, what is the risk of late blight so far this year?

  • No positive detections of P. infestans spores in Spornado or rotorod traps yet this season.
  • The BliteCast forecasting model hit the threshold for the first fungicide application at Ridgetown Campus on June 20, but since that time, conditions for infections have generally been less favourable.
  • There are no reports of late blight symptoms on tomato or potato in Ontario or anywhere in the Great Lakes Region. The only report of late blight in the United States is in Florida.
  • Taken together, the above points mean that the environment has been less conducive for infection by infestans than earlier in the season and we have no evidence that there is an active source of inoculum present in the growing region.
    image depicting two spore trapping styles. The funnel-like passive Spornado spore trap and the active rotorod spore trap.
    Figure 1. Spornado (left) and rotorod (right) spore traps setup at Ridgetown Campus, University of Guelph.

    If you suspect late blight in your tomato (or potato) crop, please reach out to Amanda Tracey (Amanda.tracey@ontario.ca, 519-350-7134) or Cheryl Trueman (ctrueman@uoguelph.ca, 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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