Late blight has been found in a tomato field in Kent County. Samples are being analyzed for strain identification reports Dennis Van Dyk, vegetable crop specialist for the Ontario Ministry of Agriculture, Food and Agribusiness. 

Samples from the potato detection in Elgin County have been identified as US-23. This strain is highly aggressive on tomatoes (foliage and fruit) as well as potato tubers but less so on potato foliage. On tomatoes, US-23 produces much more sporangia than any other strain which can be easily spread by wind. This strain should still be susceptible to Ridomil. 

Growers in all regions should be vigilant and ensure plants are protected with a late blight specific fungicide. Disease risk remains high. Plants are growing vigorously and new growth needs to be protected.  

Visit the Ontario Crop Protection Hub to view registered late blight specific products on potatoes and tomatoes.

Review the potato late blight entry in Ontario CropIPM to refresh yourself on what late blight infection looks like. The tomato late blight entry can be found at this link.

If you suspect late blight in your crop, please contact an OMAFA vegetable crop specialist:
For tomatoes, contact Amanda Tracey (amanda.tracey@ontario.ca, 519-350-1734)
For potatoes, contact Dennis Van Dyk (dennis.vandyk@ontario.ca, 519-766-5337)

Source:  OMAFA vegetable specialist July 5, 2024