apple bark disease

Asked March 30, 2020, 6:25 PM EDT

Large dead spots on major apple tree limbs. On several trees in this home orchard. See photos. I suspect this is caused by a fungus? Is there any way of killing the fungus without removing these large limbs? Can you tell what it is? and any way to save the trees? Suggestions for preventing this in the future? I think these are honeycrisp. is there a varietal difference in susceptibility?

Montrose County Colorado

1 Response

Definitely looks like a canker. No cures for cankers, probably cytospora canker. You can cut out that limb, ideally 1' behind the canker if possible so you are getting all that we cannot see. Sterilize your tools with alcohol, lysol or 10% bleach. Bleach can rust tools though. Have these trees had regular water? Stress can lead to trees getting disease. Make sure to keep vegetation immediately away from trunk so when they do get moisture, the base of the trunk can dry out.
Yes certain varieties are prone to certain diseases: fireblight, and powdery mildew especially. There are preventative sprays for fireblight, it typically starts at tips and works it way down, why I am thinking this is cytospora. https://intermountainfruit.org/dbm/gummosis
Let me know if you have other questions or need further information. You can reach me directly at susan.carter@colostate.edu