Pest and Life Cycle – (Puccinia heucherae) Heuchera rust is a fungal infection which prefers warm, humid conditions and poor air circulation. Spores are produced on the lower side of the leaf and dispersed by wind or water droplets, infecting new foliage.
Symptoms – The upper surface of the leaf develops subtle pock marks (which can contrast the leaf colour, depending on the cultivar) while the reverse produces golden-yellow to brown raised rust pustules. Heavily infected leaves may become distorted.
Management – 1. Check your plants frequently for symptoms of rust. 2. Completely remove the foliage of all rust-infected plants, being careful not to cut the growing point or terminal. 3. Dispose of infected leaves by burning or throwing into the garbage – do not compost. 4. Consider replacing the soil (about a 1/2″ depth) on the surface immediately below the crown of the affected plant. 5. Spray with a copper-based fungicide (at label rate) approved for domestic use in your growing area. 6. Always clean your pruning tools and wash your hands after handling an infected plant.
Prevention – 1. Quite often the disease is introduced to the home garden through infected plant stock, so inspect your new Heuchera purchases carefully. 2. Water Heucheras in the morning so that the foliage is dry by the afternoon. Avoid watering in the evening as this creates humid conditions that are ideal for rust. 3. Don’t create a monoculture with mass plantings of Heuchera, spread them out instead and space with non-host plants (avoid Saxifraga, which is also a host to this rust species). 4. Clean out older tatty foliage in spring as the new leaves emerge. 5. Golden, peach and orange-leaved Heucheras seem to be more prone to infection while some older strains, such as ‘Palace Purple’, are quite resistant.
Mike's Garden Guide 