Hi! I have forwarded your question to the tree team where they will have more expertise to help you with that issue. 

Hello Hans,

Thank you for contacting CSU Extension. Your email was forwarded to the Boulder County Extension Master Gardener Tree Team. If you send a response of have more questions, please add Tree Team in the subject line.

Shothole Borer is a very destructive and common disease of pome fruit trees in Colorado. However, the eggs are laid on the trunk or large branches where the larvae burrow in and attack the cambium and severely weaken the trees. As you mentioned, with this insect, you should be able to see not only holes on the trunk and large branches but also wounding of the bark on various areas of the tree.

It is more likely that the culprit is Peachtree Borer. I will share the Quick Facts from the Fact Sheet listed below.

• The peachtree borer is the most destructive insect pest of peach, cherry, plum, and other stone fruits in Colorado.
• Damage is done by the immature larvae, which chew beneath the bark of the lower trunk and larger roots.
• Insecticide sprays applied to the lower trunk when eggs are being laid can prevent new infestations.

With this insect, the damage is to the trunk right above and below the ground. The ooze is also from that region and only happens in the spring when the larvae are eating. I think it also could explain the low vigor of your tree if the trunk and roots at ground level are compromised.

I did notice that there was some fruit on the tree. I think if you agree when you read the fact sheet and treat as recommended, you might be able to help your tree become much healthier. Let us know if this is helpful or if you do not think this makes sense.

Regards

Peachtree Borer - 5.566 - Extension (colostate.edu)