Leaves have yellow or orange powder on them.

Leaves have yellow coating or powder in spring.

Cluster Cup Rust

Cluster cup rust on Ribes americanum Mill. Top arrow indicates infected developing fruit;
bottom arrow indicates rust aecial pustule on leaf.

Cluster cup rust on leaves and inflorescence of Ribes americanum Mill.
Black arrows indicate leaf pustules, white arrow indicates abnormal rust-infected fruit

• Causal organism: Puccinia caricina D.C., North America
• Crops affected: Black, red, white, and ornamental gooseberries and currants

Cluster cup rust produces yellow spots on leaves, flowers and developing fruits in April and May. The affected Ribes are usually growing in a low lying area, possibly near a swamp. The alternate hosts for this disease are Ribes and sedges. This disease can significantly reduce the yield of black fruited currants. This disease can be significant in the mid-west and northern plain states.