Rust occurs on leaves, twigs and fruit. On the leaves, pale yellow spots develop on the upper leaf surface. The spots later enlarge and turn an orange color. Lesions on the fruit usually occur at the calyx end. The spots first appear to be light green but later turn a dark green to orange.
Fruit becomes rough and misshapened on the calyx end.
Rust infection occurs early in the season as soon as new growth starts in the spring.