I have small black spot and on twigs of my hornbeams that’s spreading and causing branch die back. I’m seeing similar tip die back on a nearby River Birch and Limber Pine but no spotting.
Is this fungal? What is the recommended treatment ?
I am in Cambridge, Massachusetts US.
Thank you for contacting the Toronto Master Gardeners.
It is difficult for me to see the small black spots on your photo. Hornbeams can be infected by a number of diseases: Soft scale and canker disease are two that are most mentioned.
Cankers appear as a sunken area in the wood of the branch, stem or trunk that contains dead tissue. Cankers also increase the chance of foliage discoloration on the infected branch. In extreme infections, the cankers can greatly affect the life of the tree and may even prove fatal. Like other hornbeam diseases, the best defense is prevention. Regularly prune dead or dying branches, twigs and leaves from the tree as soon as possible. When pruning, create the cuts in the healthy part of the wood away from the cankers.
Soft scales, and certain other scales secrete sticky honeydew. Do you see a sticky substance on the branches of your tree? This link provides information on the management and control of this pest.
My suggestion would be to have a certified arborist come and check out your trees. You may also wish to contact the Massachusetts Master Gardeners here. There may be a disease in your area that we are not aware of.