Photo of the Week – March 17, 2016

You’ve probably seen them – funny-looking brown balls stuck to eastern red cedar trees.  Sometimes, the  balls have long gooey orange tentacles hanging from them.  Do you know the story behind them?


Cedar-apple rust is a fascinating organism that uses two different hosts to help it complete its life cycle.  Galls that form on eastern red cedar trees eventually release spores, some of which make their way to leaves of apple or crabapple trees.  On those leaves, they stimulate formation of yellow lesions that eventually mature and create more spores that then need to make their way back to another cedar tree to complete the cycle.  The lesions on the leaves can be harmful to the apple trees (including the one in my yard) but I’m not sure there’s any big impact on cedars.

You can read much more about this at the Missouri Botanical Garden’s website.

I found the above gall at our family prairie last month.  And yes, I did cut the cedar tree down after I photographed the gall (see photo evidence below).


5 thoughts on “Photo of the Week – March 17, 2016

  1. Sara McClure March 17, 2016 / 2:53 pm

    Another good reason to keep cedars at bay – keep our apple trees healthy!

  2. Dylan Flather March 17, 2016 / 4:21 pm

    Hey Chris, really enjoy your blog even though I am not an ecologist by training. Just curious why you cut the tree. Was it to prevent the spread of cedar-apple rust? Is this not a natural host-parasite interaction (i.e. has the rust been imported from somewhere)? Thanks.

    • Chris Helzer March 17, 2016 / 5:28 pm

      Hi Dylan, the cedars invade grasslands around here without fire to suppress them and without control they turn prairies into woodlands. (which is not what we want)

  3. newconaturalist March 18, 2016 / 1:26 pm

    I remember seeing these galls on the cedars in my yard when I was a kid back in Virginia. I had no idea they were cedar apple rust. Thanks for the info!

  4. Luddene Perry March 19, 2016 / 9:57 am

    Of course, I didn’t think about this when I plant my 7 apple trees. It’s a good way to see which variety is CR resistant.


Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.