Cedar Apple Rust
Q: I have two seven-foot tall Eastern red cedar trees. Both have growths that look like walnut meats on them. Is this cedar apple rust?
A: Orange, jelly-like spore “gobs” were on the trees last spring but you didn’t notice them. The gall you notice now will be at the center of the fist-sized mass in April-May. This particular disease travels back and forth between Eastern redcedar and apple trees. Both hosts are required for it to develop.
Cedar apple rust is less harmful to redcedars than apples, on which it causes leaf and fruit drop. If you value woodland apples and crabapples, remove all of the dried galls now.
The disease can be managed on apple by spraying with a fungicide labeled for use of fruits (click for sources). Read and follow label directions.