Cedar-Apple Rust Gall

>> Sunday, April 25, 2010


Following yesterdays rain we began seeing these alien looking things hanging on many of the cedar trees.  What in the world were they?  It seemed evident that they were some type of fungi.  After doing a bit of research we discovered that this is the Cedar-Apple Rust Gall. 

The following information is taken from the Kentucky Pest News Newsletter.

“Rust-infected Juniperus species (cedars and junipers) are revealing bright orange evidence of the rust fungi infecting them during moist periods this spring.  In Kentucky, we commonly see three different rust fungi on cedars and junipers, often on the same tree.  These rust diseases are cedar-apple rust, cedar-hawthorn rust, and cedar-quince rust.  All three rusts are caused by different species of the fungus Gymnosporangium, each of which must spend a phase of its life cycle as a parasite on Juniperus species such as native red cedars or ornamental junipers.  The other phase of the life of these rust fungi is spent on susceptible alternate hosts such as apple, crabapple, hawthorn, mountain ash, pear, and serviceberry.

 Cedar apple rust.  The cedar-apple rust fungus (G. juniperi-virginianae) forms light brown to reddish or chocolate brown galls in the leaf axils of infected Juniperus species.  These galls are usually rounded and range from pea-sized to 2 inches in diameter.  As galls mature, the flesh becomes corky and the surface becomes pitted with circular depressions.  In spring, following rainy periods, slimy, yellow-orange tendrils, or “spore horns,” up to 2 inches long swell and protrude from these depressions.  A gall may produce many spore horns, which cause it to resemble orange-colored blossoms from a distance.  Severely rusted Juniperus can be very conspicuous.”

From the reading I did I found that these galls apparently do no harm to the cedar trees but can do damage to the apple trees.  There may be damage to the leaves and on the fruit as well.  It can weaken the trees and can cause them to eventually die.  In some areas in past years laws were passed requiring all cedar trees near apple orchards to be destroyed.  As many cedars as we have here on the farm that isn’t an option.  Hopefully, our young apple trees won’t suffer too greatly.


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