Hi Betsy, 

Thank you for reaching out to CSU Extension! 

I'm sorry to hear about your tree and appreciate you sending over those images. In order to better understand what is going on with the tree, would you be able to send a few more images that show the base of the tree (to help us understand how the tree was planted) and a picture of the entire tree? 

Also, did you notice any yellowing of leaves or other discoloration last fall? Or have you noticed the presence of any insects on the tree - either last year or more recently? If so, a photo of those insects would be helpful as well. 

In the meantime, here is a fact sheet on common diseases that impact locust trees that you might find useful: https://extension.colostate.edu/topic-areas/yard-garden/honeylocust-diseases-2-939/

Thank you!

CSU Extension Boulder County Master Gardeners

Thank you for your response!

Hi Betsy - Thank you for sending the additional photos and information. I'm going to pass this on to our diagnostics team to get their expertise.  They will be in touch once they have had a chance to review!

Hi Betsy,

Thanks for providing the other pictures. Our diagnosticians have looked at all the pictures and we believe the bark damage is caused by squirrels. They eat the bark away to get to the softer phloem - a common problem in urban areas. The scratches on the trunk also look like squirrel claw damage from routinely climbing the tree. I've attached a really good article from Purdue University that talks to how to control tree squirrel damage. 

You do have a different issue with the damage in the branch "crotch" where it looks like the branch has pulled away from the trunk. There is a bit of squirrel damage outside of the wound, but it also looks like the wound might have been caused by stress (break or cut) near the trunk when the tree was younger and it is getting bigger maybe due to additional bird or insect activity. Due to the size and depth of that wound, you might want to consider pruning that branch off the tree. I know that might seem daunting since it is a pretty big portion of the tree on that side but there is a concern that leaving it, might cause bigger issues including a fungal or bacterial infection that could weaken the tree past the point of no return. You can keep an eye on it to see how things progress but most likely, water will continue to collect in that spot and cause bigger issues. I would recommend discussing that with an arborist to see if they could do anything to help repair the wound or to get advise on correct pruning technique and pruning (other branches) for aesthetics - to balance the overall shape of the tree. 

I hope this all helps.

Thank you!