Pachysandra is a great ground cover for shady sites in Illinois. It has dark, evergreen foliage that fills open areas quite aggressively with rhizomes. The plant is sometimes bothered by scale insects, a few leaf-spotting diseases, three stem diseases, and a blight. Diseases can be minimized by thinning plants occasionally and pruning surrounding plants to provide better air flow in the area.
Macrophoma, Phyllosticta, and Septoria fungi can cause leaf spots on this host, but usually damage is minor. Sometimes, we see Fusarium or Rhizoctonia stem rots. There has also been a report of Sphaeropsis tip blight on pachysandra (similar to the disease on pine), but we have not seen it at the Plant Clinic.
The most common disease seen on pachysandra is Volutella blight. We talked about imperfect and perfect stages of fungi in issue no. 10 of this newsletter. The perfect stage of this disease is Pseudonectria pachysandricola. The imperfect (conidial) stage is Volutella pachysandrae. Both cause the same disease. We call it Volutella blight, for ease of communication.
Volutella blight may cause tan leaf spots or blotches, often with concentric rings within the spots. The lesions have a dark brown border. The fungus may move to the stems, where it girdles and kills tissue beyond the infection. Volutella is a stress pathogen. We usually see the disease in spring following winter injury, but humid conditions of late have caused a flare up in some locations. The disease is common following recent transplanting, shearing, leaf scorch, or a scale infestation. Look for pink (Volutella stage) or red (Pseudonectria stage) masses of spores on the lesions.
Remove and destroy severely infected plants. Determine the source of stress and try to correct it for your site. Avoid heavy mulching and overcrowding of pachysandra plants. Fungicides can be used as preventives. Many products are listed in the Home, Yard, and Garden Pest Guide and the Commercial Landscape and Turfgrass Management Handbook. These include copper fungicides, chlorothalonil, and mancozeb active ingredients. The commercial handbook also has a few systemic products listed, including Manhandle, Spectro, TwoSome, and Zyban. For more in-formation on this disease, consult Report on Plant Disease, no. 649, “Pachysandra Leaf and Stem Blight,” available in Extension offices or on the Internet at http://www.ag.uiuc.edu/%7Evista/horticul.htm.