Black Knot infections of 'sweet' cherry species

[SwampDonkey]

Here is a USDA report on Black Cherry infections of black knot fungus in southern US.

http://www.forestpests.org/southern/Diseases/blackknt.htm

Here are some photos taken today in my back yard. I have 1 acre of black cherry growing here in an old orchard I cleaned up 2 years ago.

New infection of black knot on a black cherry sapling, notice the amber colored sap which has turned to jelly. Some white spruce needles have become embedded in the jelly. The sapling is 10-12 yrs of age and 15 feet tall.


Severe black knot infections on mature black cherry boles. Trees are approximately 60 years of age.


No infections of black knot on mature pin cherry crowns and boles. (60 yrs of age)

Black knot disease also infects choke cherry and some but not all commercial plum species, such as the Stanley variety. It is also found on wild Canada plum. Black knot does not infect "sour" cherries such as pin cherry. Sometimes at a distance you may think they are infected but close observation of the branch will reveal that a branch has died and the bark pealed away.

Best management practice is to remove infected trees and branches, and promptly burn them. Pruning may also be beneficial, but be careful not the cut too close to the tree bole. Entry points of the disease are dead branches, bole scares, stress cracks, forked stems and lenticels (white speckled markings in the bark). In areas with drier, less humid climates the disease is less prominant. Also, stands of mixed hardwood containing sugar maple, oaks, beech and yellow birch will yield better quality black cherry. Open crown conditions of old orchards and line fences will be most susceptable as will stands with choke cherry undergrowth.

cheers

[slowzuki]

Thanks Swampdonkey!

The infection rate here is about 9/10 trees.  All older trees have it.  There are a lot of choke cherries around as undergrowth.

I'll have to start burning the trees after cutting.  I've been told if doing pruning to clean the tools before working on a healthy tree, this would make sense with your info.

[SwampDonkey]

In my first photo, for those that may not read the USDA report, the black crusty looking areas are the infecting fungi.

[RedHawkRidge]

Most Northern Cherry in Western Wis have this or something like it, from young to old.  A few trees have it on the main stem and are nearly girdled. Others seem to have clusters on branches, without being severely affected.  I have some cherries that have had the problem for years without apparent significant effects.
Some examples of the crud appear to be active and associated with sap gel forming on the stem; other trees just have clumps of black crud on the branches that look like my cat took a dump on them.
jim

[SwampDonkey]

As you suggest RedHawk, the disease is rarely fatal to the tree. It just causes deformities and degrades the use as lumber. In Pennsylvania, I've heard the black cherry is not so seriously infected. This is probably in a dryer or less humid region of its range. Its very humid climate up here in spring and summer, from April to September. (Maritime-Humid climate) Its not comfortable out side (temperature-wise) 'till the end of May though, when leaves begin to emerge. Our aspen are beginning to flower here now though, they look like pussy willows. Its actually quite warm in the hardwood stands by noon, having to peel off some layers of clothing, but evenings are dipping into the 20's. February was warmer than March this year. I haven't had the snow blower out since mid-January.