Tree Diseases - Anthracnose
Anthracnose is a fungus that will attack many Deciduous trees including Maples, Oaks, Dogwoods and London Plane trees. London Plane and Dogwood are the most common infections in Plymouth County. Spores from past infection will re infect new foliage as it emerges. Wet weather will increase activity. The fungus will kill young leaves and spread to twigs and branches. Feature trees may warrant control.
Once the twigs die the ground below the tree becomes a litter ground of dead twig and some branches after a high wind or heavy rain storm. No home owner would want this under a feature tree. Commercial properties could not allow this scenario to continue in a parking area. At this point control is questionable at best. It would be extremely costly if not Arbor culturally impossible. Do not let Anthracnose get to witches broom on feature London Plane Trees.
Anthracnose rarely kills its host. It will make plants look unsightly.
Leaves have to be sprayed 3-4 applications every two weeks until they harden off. Once the leaves have hardened off it is much more difficult for the fungus to penetrate the leaf. Wet weather will determine how many application are necessary in a season.
Dogwood Anthracnose effects mostly leaves. All Dogwoods are susceptible. Kousa Dogwood is the only resistant dogwood.
Planting a "Mono Culture" many plants of the same species on the same driveway will increase the chance of getting a fungus like Anthracnose. Many will plant a row of London Plane trees down both sides of a long driveway. This species is known to be tolerant of heat stress and compaction making them a good choice for islands in parking lots. The Anthracnose will start in the leaves looking like frost damage.
The fungus will move down on the twigs killing as it moves down. This causes new shoots to form with multiple 5-6 small shoots with leaves to form. During wet weather the fungus will kill the new leaves and twigs.
This is called "Witches Broom". There are many types of witches broom on many different species.