Black Knot Disease on Chokecherry Trees: Prune and Replace

Diagnosis

The black, corky growth on the branch is black knot, a fungal disease that will eventually kill the tree if unchecked.

Immediate Action

Prune the infected branch well below the knot and destroy it (burn or bag). Because the tree was purchased only a week ago, return it to the nursery for a disease‑free replacement—most nurseries honor a 30‑day guarantee.

Long‑Term Management

Monitor for new knots each spring. Fungicides are generally ineffective once the disease is established; sanitation and resistant varieties are the best strategies.