Today, I had to euthanize my two tomatoes (Big Beef and Brandywine) because they caught late blight. I'm bummed. They performed well and still would have had lots of tomatoes to go. I googled it and someone who contacted the ministry of agriculture (I guess our closest equivalent to a US extension?) said it's widespread across Southern Ontario.
It is always very sad when you have to pull productive plants. The "good" news for you in Canada is that at the end of September you probably didn't have very long left until frost, when they would be killed anyway.
Now that you know you have late blight, you can work on prevention for next year. If you have room to plant your tomatoes in a different spot, move them as far away as you can. I would try drenching your soil with something fungicidal, maybe a baking soda solution or Neem oil, before you plant in to it. Keep your soil well mulched and only water the soil, not the plants. Fungicides generally are way better preventatively than trying to treat an established disease. So start early in the season spraying every couple weeks. Diluted milk makes a good preventative spray. Compost tea used as a foliar spray helps build colonies of protective microbes.
The late blight we are seeing here in the Northern US and Canada can NOT overwinter (except on potato tubers.) See usablight.org for more information. It is only one mating type and two are required for the disease to become soil borne, and even if both were present in Canada IMO it likely wouldn't survive the winter.
If LB overwintered in the North, growing tomatoes or potatoes here wouldn't be possible, after years like 2009.
Drenching your soil with fungicide will only serve to kill benficial fungus in your soil and weaken future plantings by weaking the soil food web, IMHO.
I strongly recommend anyone growing potatoes or tomatoes read up on usablight.org, it is an invaluable resource.
The advice to rotate your plantings, while not a bad idea, generally applies to farmers and not small backyard gardeners who don't sterilize tools and don't have the space and only serves to discourage people from planting at all, IMO.
I'm bummed. They performed well and still would have had lots of tomatoes to go. I googled it and someone who contacted the ministry of agriculture (I guess our closest equivalent to a US extension?) said it's widespread across Southern Ontario. 