Rust disease is a group of fungal diseases affecting the aerial parts of the plants.

Gymnosporangium rusts are a group of closely related diseases caused by fungi that infect both junipers and woody plants in the rose family. These fungi must infect both types of plants to complete their life cycles. 

Plants affected include:

  • Juniper
  1. Smooth, round, up to golf-ball sized, galls on twigs.
  2. Elongated, slightly swollen areas along  the branches.
  3. Prolific branching, called witches’ brooming.
  • Apple:
  1.  Yellow to bright orange spots on leaves.
  2.  Spots on fruit.
  • Hawthorne:
  1. Yellow spots on leaves.
  2. Distorted fruit with horn-like protrusions.
  3. Galled Twigs.
  • Shadbush or Serviceberry:
  1. Brownish-orange spots on leaves.
  2. Distorted fruits with horn-like protrusions.

At AC Plant and Turf, we suggest planting rust resistant cultivars of Juniper, Crabapple and Hawthorne.