Disease Late Blight Tomatoes

Current late blight risk in Ontario field tomatoes: July 25, 2019

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

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.

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 at 1 of 8 sites for the July 15-18 sampling period and 4 of 8 sites for the July 18-22 sampling period. Late blight symptoms caused by the US-23 genotype have been observed in New York and Wisconsin on potato, 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. I will begin parental leave in early August and will be unavailable for the rest of the 2019 growing season.

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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