Rust fungi appear on the upper and lower leaf surface as orange-yellow spots. Several rust fungi commonly infect the leaves and canes, while only a few fungi are able to infect fruit. Rust fungi are fairly common, but do not typically affect the overall health of the plant. However, one fungus, commonly known as orange rust, is considered a serious threat to black raspberries. Red raspberries are immune. Orange rust is a systematic disease that survives winter in newly formed roots, causing new infections the following year.
