Yesterday we went out to check on ginseng seedlings and found the cedar trees blooming with Cedar-Apple Rust fruiting bodies. It’s caused by a fungus and alternates each year on cedars or apple trees. If there aren’t any apple trees around, or maybe even if there are apple trees, it also chooses hawthorne or crab-apple trees here in the Ozarks for hosting the alternate years.
On the alternate years it appears as small round rust colored circles on the leaves of the host plants. When it gets to the cedar year, it “blooms” with the otherworldly things you see in the photo above.
If you’re growing apples, it pays to grow varieties resistant to this fungus because controlling it or eliminating it is an exercise in futility. The second link is from the University of Arkansas Extension and it lists a whole lot of varieties and their corresponding resistance ability. “VR” means “very resistant”.
Here’s some links to learn more: