There are three major problems on prunus plants. The first is black knot - it looks like swellings that have ruptured black on the branches. It eventually kills. The two that cause bleeding are cankers and peach tree borer. These two problems attack stressed trees. The borer attacks near the soil line. Sap oozes out of the EXIT holes. The cankers occur anywhere on the tree. (this is what your tree probably has.) At first, sap starts oozing out of the bark and there is no visual reason why (hole or cracked bark). With time the dead bark spits and the bleeding increases. Eventually both the borers and cankers will kill the tree. There is no recommended borer control for trees that bear an edible crop. There are no effective canker fungicides. Try and keep the plants growing vigourously. Many plnts in the prunus genus have a short life expectancy in Northern Illinois because of the freezing and thawing in the spring is a major stress factor.

I have a different problem with my sour cherries I thought I would post here. I have two sour cherries (Montmorency and Morello) on dwarfing Giessen rootstocks in containers on my roofdeck (8th floor) in Chicago. Last year, they both got horrible powdery mildew followed by mite infestation (I understand one can follow the other). I tried a milk spray I read about, soap spray, and finally a neem spray. Nothing seemed to provide complete relief. Unfortunately, the mildew and mites started to infect my apple trees, which proved more resistant, but still suffered. Now, it is important to add that these poor trees started off the growing season on a covered balcony until we moved to our roofdeck, so I am wondering whether the lack of direct sun caused the problem in the first place (everything stayed wetter longer, etc.). Is there anything I can do to prevent th return of mildew/mites this Spring? Or should I toss the cherry trees in the interest of healthier apples? Thanks for any advice.