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.
Having done more research on these black spots there has been mention of these spots on a number of blogs, however no one knows with 100% certainty what these spots could be.
By enlarging the original photo of the twig I can see that the spots are indeed fungal, but cannot be 100% certain that it is anthracnose. Anthracnose is caused by several different, but closely related fungi. Branch symptoms appear as small orange brown blisters or a brown band encircling the young twig resulting in shoot death.
Anthracnose fungi survive winter in buds, twigs, fruit, fallen leaves or petioles. In spring, spores are splashed short distances by water or carried long distances by wind to newly forming leaves. If weather conditions remain cool and wet, spores will form within the leaf spots and spread throughout the tree canopy. These spores will form new leaf spots. This cycle continues as long as cool, wet weather is present. Good sanitation methods such as removal and destruction of infected plant parts is the key to controlling this disease. Pick up fallen leaves; prune trees and shrubs for better air circulation and remove dead and diseased wood.The article Anthracnose of Shade Trees gives information on how to manage this infection.
As in my previous answer my recommendation would be to get an on-site accredited arborist to properly identify your tree, assess the disease, and recommend treatment. In the meanwhile, follow the clean up procedure to minimize spore development in and around your trees.