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Question from Amy (received 5/20/20) -
This is a Kwanzan cherry. What is going on here and how can I help it? This tree is usually a prolific bloomer, but this year it barely bloomed at all and the leaves are sparse. There are new leaf buds on the bare branches that are healthy.
Answer from Gabrielle Harden, USU Forestry Extension Educator (sent (5/21/20) -
Amy,
It appears that this tree may have a canker. Unfortunately, with its location, there is not much you can do. If cankers occur on branches, the branches can be pruned to remove the canker. Here, the canker is on the bole. Cankers are caused by a variety of fungi, most commonly a fungus called Cytospora, but they can also be caused by bacteria. Your tree appears to have the fungal variety. The sap coming out is a condition referred to as gummosis - typically the result of another condition (cankers, insects, wounds, etc). Cankers are often the result of stressful conditions for a tree. It could have started as a frost crack and the fungi or bacteria got in. Trees are more susceptible when they are stressed or wounded. It is important to provide your tree with the proper environment (enough water, adequate sunlight, nutrients, minimal competition, etc.).
With the tree already being under stress, it is more susceptible to other pests such as insects. Reducing stress is vital to preventing further issues. Keep an eye on this area to make sure there are not insects getting in. If you see exit holes and frass, insects are in your tree and you have an entirely new issue.
To manage this there are some things you could try, but I fear this canker has gone too far. Once cankers are in the bole of the tree, there is little that can be done. 50% - 80% white latex paint mixed with Captan or Topsin OR Surround mixed with lime sulfur painted onto the area. Your best option is to ensure you are giving this tree enough water (drip irrigation often does not water deep enough, a tree needs to be deeply watered - 10 gallons per inch of diameter is a general rule of thumb) and continue to provide ideal living conditions. It is possible that once this tree gets enough water, the wound will start to heal and the tree will be just fine.
Here are a couple of resources that you may find helpful -
I hope this helps.