Blister Rust

Blister rust appears as yellow or orange pustules on the undersides of currant and gooseberry leaves and berries throughout the season. The fungus produces millions of spores that spread readily in wet conditions common to western Washington springs and early summers. Red currant is particularly susceptible to this disease. Control involves removing infected plant material, improving air circulation through pruning, and avoiding overhead irrigation.

Rust fungi often need two different host plants to complete their life cycle, so identifying and managing the alternate host can break the cycle. Remove heavily infected leaves and dispose of them away from the garden. Improve air circulation to speed leaf drying after rain. Fungicide applications are most effective as preventive treatments before symptoms appear; once pustules are visible, the current infection cycle is already underway.