We have reports of dieback in established pachysandra the past week. Pachysandra is a popular ground cover species grown in shady, well-drained locations. The wet weather in these shady sites has encouraged development of a fungal blight.
Pachysandra blight, a disease caused by the fungus Volutella pachysandrae, begins as brown leaf blotches that develop targetlike rings. The fungus may progress through stems and stolons, causing cankers that girdle and kill stems. You might not see the disease initially because it develops on stems hidden by the leaf blades. Look for wilted pachysandra plants with brown blotches on the leaves. Push back the leaves to find the blotches and cankers on stems. An easy-to-spot diagnostic feature is pink to-orange spore masses on the underside of leaves or on stems just after a rain. Spore masses are common in moist weather. Look particularly for Volutella blight in dense plantings where thick mulch has been used and where conditions are warm and moist. The disease often follows stress, such as winter injury, insect infestation, sun scald, or recent shearing. Remove and destroy any severely infected plants. Do this when plants are dry to prevent disease spread.
Because this disease is more likely following injury or stress, try to provide a protected location for pachysandra. This species thrives in shade in a moist, well-drained, acidic soil with plenty of organic matter. Remove dead or diseased plant material and concentrate on improving site conditions. Chemicals may be used as protectants, with repeat applications being necessary at 10- to 14-day intervals, depending on the product and weather conditions. Copper, mancozeb, and chlorothalonil are some active ingredients registered for this use on pachysandra. Look in the Home, Yard, and Garden Pest Guide and the Illinois Commercial Landscape and Turfgrass Pest Management Handbook for specific products. Effective nonchemical controls include keeping insects under control and mulching pachysandra with a material that does not hold excessive moisture. Pruning any surrounding plants for better air movement may also help manage this fungus. Consult Report on Plant Disease, no. 649, for additional information.