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).
The Prairie Ecologist 