Rusty Spot

You'll see rusty spot as rust-colored lesions on foliage during cool, wet conditions. This fungal disease spreads by spores. Remove infected leaves. Improve air circulation and reduce leaf wetness. Avoid overhead watering. Apply fungicides preventively. This rust disease spreads readily in moist spring and fall conditions common to Western Washington. Watch foliage closely for early symptoms Early detection and prompt management of symptoms help limit disease spread.

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.