As you said, it's a phytosanitary issue. It's the movement of any cherries from Ontario out of the province. As I understand it, it's not going to affect cherry growers in Ontario very much. There's not much of that happening. What it does mean is that, in order to export to the U.S., any cherry grower in another province, for example B.C., has to make sure that they have it on their labels that the product was produced in that province, just so the U.S. knows that it doesn't have the pest that Ontario has, Rhagoletis cerasi.
On June 6th, 2017. See this statement in context.