HI Steve. Im in the Lake George area of upstate NY. We used to be zone 4 but now 5 . It gets very cold in this area. I have about a dozen plum trees and have been getting devastated by Black knot . Methley, Bruce, Burbank, Santa Rosa, Black Ice, Hanska, Shiro, and especially Stanley Prune have been overwhelmed and all but two of those are still standing. So far, there is nothing on my Alderman( whiich has large red plumbs in August that taste great) and no sign of any on my Superior that is literally 10 feet from the infested Prune tree. I also have a Waneta that is still young but no sign of Black Knot. I have been trying to get new trees the past few weeks and finding that there arent a lot available mail order. The President is supposed to be a good one and I put that in last May. BlueByrd is another. And Kenmore(NY 9) is also supposed to be a good one, but I cant find one for sale. Order soon if your looking for spring delivery.