Hemlock-blueberry rust

Berries leaves can be part of the life-cycle for some rust fungi! For example, hemlock-blueberry rust results in a powdery, orange rust on the undersides of blueberry & hemlock leaves. Don't worry if your patch is infected—the berries will be safe to eat.

https://www.fs.usda.gov/detailfull/r10/forest-grasslandhealth/?cid=FSEPRD684233&width=full