Hollyhock rust

Hollyhock rust is a prevalent fungal disease caused by the pathogen Puccinia malvacearum. This obligate parasite specifically targets plants in the Malvaceae family, with hollyhocks (Alcea rosea) being the most common and severely affected hosts in home gardens and landscape settings.

The primary clinical signs of this infection are distinct orange-to-brown, raised pustules that appear predominantly on the underside of leaves. As the disease advances, these spots may also manifest on stems and petioles, eventually causing the foliage to turn yellow, wither, and drop prematurely.

The development and spread of the fungus are heavily favored by high humidity, prolonged rainy periods, and moderate temperatures. Spores are easily disseminated via wind, water splashes during irrigation, or rain, allowing the disease to travel rapidly between plants if they are planted too closely together.

The harmful impact of hollyhock rust is significant as it weakens the plant by disrupting photosynthesis. If left unmanaged, the infection can severely stunt the plant’s growth, inhibit flower production, and ultimately lead to the death of the specimen, while also serving as a reservoir for spores.

• Promptly remove and dispose of any infected leaves or stems.
• Ensure adequate spacing between plants to allow for proper airflow.
• Water at the base of the plant to keep foliage dry.
• Apply fungicides containing copper or systemic triazoles if infection is heavy.
• Maintain good garden hygiene by removing all plant debris at the end of the season.