Oozing sap, fungal disease hurting those cherry trees

I¹ve been having problems with cherry trees. Limbs are dying back; there are

fewer leaves; and the trees just don¹t 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 a 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, I¹m 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 and may be reached at

skellyj@unce.unr.edu or 887-2252.