Cedar Apple Rust



Cedar Apple Rust

Paul Schnare

Saturday, April 26, 2003 


You may see large orange looking balls on cedar trees showing up at this time of the year.  If you look closely, you will find a round brown gall about the size of a quarter that encircles a branch.  Coming out of these galls are orange tentacles that are about two inches long.

What you are seeing is one phase of the fungus called cedar apple rust.  These orange tentacles are producing spores that will be carried by wind to nearby apple or crabapple trees.  The infected apple tree leaves then will exhibit a round orange area on the underside of apple trees.

In July spores are sent from apple trees to nearby cedar trees.  The infected cedar trees produce these brown quarter sized galls that surround the branches of the cedar trees.  Then in April, these galls produce the orange tentacles now evident, and the cycle begins again.

One way to control this disease is to remove one of the hosts, that is, cut down all of the cedar trees or all of the apple trees within a one to two mile radius.  This is not a practical solution in a metropolitan area.

You can also spray cedar trees in July, or apple trees in April with Bordeaux solution.  Make applications three times, about 10 days apart.  Be sure to follow all label directions.

Generally the disease is not lethal.  On the other hand, if infection occurs annually, susceptible trees will certainly be hurt by the disease.