What is it?
Cedar apple rust, cedar hawthorn rust (juniper hawthorn rust), and cedar quince rust are the most common cedar rust diseases. They are rust fungi that require two different hosts, one evergreen and one deciduous, to alternate and complete their disease cycles. Evergreen hosts include red cedar or juniper, while deciduous hosts include apple, hawthorn, crabapple, mountain ash, and pear. These rust fungus are mainly cosmetic issue.
Symptoms
- Cedar apple rust and cedar hawthorn rust cause brown to dull red, round galls on juniper needles, with cedar apple rust producing larger ones.
- Cedar apple rust and cedar hawthorn rust can cause yellow, orange, or red spots on the upper surfaces of hawthorn and apple trees. They can also cause yellow to orange spots on the fruits.
- Cedar quince rust shows up as long swellings on juniper twigs and needles.
- Cedar quince rust causes a swollen, corky gall on the current year’s growth.
Damages
- Premature leaf drop, branches dieback and defoliation on severe infestation.
- Damage are mainly aesthetic and seldom kill the tree.
What to do?
- Prune infested evergreen parts in winter/early spring, before spores emerge.
- Rake and clean up fallen leaves on deciduous trees in fall time.
- Avoid planting both hosts to avoid contact.
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