I've been having problems with cherry trees. Limbs are dying back, there are fewer leaves, and the trees just don't look right. At first I attributed this to the late May freeze, which killed all the blossoms. I thought the trees might have gone into shock. However, as the summer progressed and the trees were losing more and more branches, I realized I needed to do something to save the trees.
A common problem with cherries and other stone fruits (peaches, nectarines, plums or apricots) is gummosis. This appears as oozing sap or beads of sap on branches. Stone fruit have a natural tendency to ooze sap, so if a tree seems healthy, a little sap is no big deal. Sometimes trees under stress, growing in poorly drained or very dry soil, will produce sap. They may also respond to changing weather conditions or soil moisture by gumming up. Mechanical injury is another cause. If you wound a tree, it "bleeds."
Then, of course there are fungal and bacterial diseases that make a tree gum out. For gummosis cut out the badly infected branches. Be sure to disinfect your tools between cuts. I use isopropyl alcohol. Insects can also cause gummosis by boring into the bark. The tunnels they form can then become infected with disease. Borers are almost impossible to control except by preventing them in the first place by keeping the tree healthy with sufficient water, nutrients and proper pruning.
Cytospora canker is fungal disease problem that affects many trees including cherries. Sunken, dark lesions (cankers) appear on the trunk or branches. The bark at the edge of the canker can thicken and roll inward as a callus. Sap can ooze out. Leaves may yellow, some branch and twig dieback can occur, and eventually the entire tree can decline and die.
Heat and drought stress increase the susceptibility of trees to the disease. Prune out dead and dying branches a few inches below the canker into healthy wood. Disinfect your tools between cuts. Provide moderate amounts of fertilizer, preferably slow release to improve growth. Heavy amounts of fertilizer can promote the disease. Irrigate appropriately. If the canker is in the main trunk, pruning is of little value.
I found a broken sprinkler was the cause of problems for my trees. I increased the water and pruned out the dead limbs. With some late fall fertilization, I'm hoping the trees will be all right next year.
JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.
