Hi Hans,

Sorry to hear about your tree! It seems like it's some sort of borer (insect) or sap suckers (bird) that is impacting the tree. Can you look at the holes and see if you see any ‘frass’ – the saw dust material left by borer insects around the openings on the trunk? This would be indicative of borers over sap suckers. 

Here's a resource about a few different types of borers: https://extension.colostate.edu/topic-areas/insects/shade-tree-borers-5-530/

Best wishes,
The Boulder County Extension Colorado Master Gardeners

Hi Hans, 
Pruning trees in winter regulates growth and allows you to create structure. Pruning trees in spring brings on vigorous growth and fruiting wood. Timing is key to the health and growth of the tree. In our previous email, we sent you the shade tree borer fact sheet which is helpful in regard to the holes in the trunk. If you want, you could bring in a large branch sample to our office along with pictures and request a diagnostic test. Each test is $7.00. I also have two more fact sheets that will help you with crabapple management and pruning.

Flowering Crabapple Trees - 7.424 - Extension (colostate.edu)
Science-of-Pruning-Full-Section.pdf (colostate.edu)

Thanks again for your questions,
Lisa



Thanks for your kind feedback, Hans!