To date, no late blight has been reported in Ontario.
Here is a chronology of late blight reports from the US Northeast so far this spring. Note that in most cases, these are reports of symptoms being found on a small number of plants in one location, unless otherwise noted. When a small number of plants are involved, they are generally destroyed after sampling and the remaining plants are treated to reduce the risk of spread.
June 28 – Long Island, New York – 3 tomato fields, 2 potato fields all in close proximity
June 28 – Virginia – late blight reported in potato
June 28 – Delaware – late blight reported on two potato plants in a difficult to spray part of the field
May 12 – Michigan – late blight reported in one potato field
May 9 – Maine – late blight reported at one location – volunteer tomatoes in a greenhouse
April 22 – Connecticut – late blight reported on potato and tomato in a greenhouse
Here are two websites where you can track late blight reports: