IDENTIFICATION — In fall, you’ll spot hard brown galls on twigs of Eastern red cedar. In spring the galls swell, turn orange, as in the photo, and release spores.
DAMAGE — When those spores find the foliage of an apple tree in late spring, spots of orange rust, like the ones in the small photo, grow on the leaves during the summer. Infected leaves drop off in midsummer, leaving the tree unsightly. As they ripen, spores from the apple are then blown back to the cedar to continue the cycle next year.
CONTROL — Grow rust-resistant apple cultivars and don’t plant Eastern red cedars and apple trees in the same garden. If you have susceptible apple trees, spray them with a fungicide as a preventative when the flower buds begin to open in spring.