Although OMAFRA has not yet confirmed late blight in tomatoes in Ontario, credible reports of the disease in tomatoes are coming in from the United Counties of Stormont, Dundas and Glengarry and from Perth County. Once samples are examined, further updates will be available.
We do know, however, that is has been confirmed in tomato and potato in neighbouring states, where it is spreading. It has also been confirmed in potatoes in Simcoe County.
Recent weather has been conducive to the development and spread of late blight. Commercial growers should scout often and ensure they are using fungicides with good late blight activity in their fungicide program. When late blight is in the area, spray intervals should be shortened.
See the late blight post from July 29 for fungicide recommendations for tomatoes in Ontario.
Contact OMAFRA at 519-674-1690 or firstname.lastname@example.org if you suspect you have found late blight in Ontario.