What do you get when you have lots of spring rain, cedar trees, and apple trees? You get an invasion of rusts - in this case, Cedar-Apple Rusts (Gymnosporangium juniperi-virginiana).
Rusts are considered parasitic fungi that attack a variety of hosts. Here, the unfortunate hosts are cedar trees and apple trees. The two types of trees need to be in proximity to each other for the rust to "take." In these pictures taken at the Habitat Education Center and Wildlife Sanctuary in Belmont, MA, the cedars and apples are within fifty yards of each other.
A closeup of the rust shows its jelly-like tentacles or horns sprouting from a hard, acorn-like gall. After a rain, or especially during a day-long mist, these horns come out in all their glory, dangling off the cedars in a spiderish manner. They can easily expand to the size of your fist. After a day or two of sun, they dry up, then return at the next rain. Eventually the hardened galls die but they can stay attached to the tree into the next year or even longer.
The rust doesn't appear in this form on apple tree though. Instead, the apple leaves get orange-brown lesions. The rust reproduces and continues its life cycle by spreading spores between the two trees. This can go on year after year after year.
They are not difficult to see. Here's a few trying to blend in with a tractor... but I caught them.
For additional information, check out the UMass Extension website for a helpful PDF.
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