Issue 11, July 16, 2018
Pachysandra Leaf and Stem Blight
When sited properly, Japanese pachysandra (Pachysandra terminalis) is considered to be a mostly trouble-free species. However, it occasionally will have problems with scales and a few fungal diseases. Leaf and stem blight is the most common diseases on pachysandra.
Common leaf and stem blight symptoms include:
- Tan leaf spots or blotches with dark brown borders. Concentric rings are often visible within the spots (Photo 1).
- Stems can also be infected resulting in dark brown, expanding cankers. The canker girdles the stem resulting in the death of tissues beyond the infection. Dead stems eventually become withered and shriveled (Photo 2)
- Under wet conditions of spring and early summer, pink to orange brown spore pustules are visible on the undersides of affected stems and leaves.
Photo 1 Pachysandra leaf blight lesion with concentric rings and dark brown margin.
Photo 2. Blighted stems and leaves of Japanese Pachysandra, caused by pachysandra stem and leaf blight.
This disease is favored by a weakened or stressed host plant and is often seen on pachysandra damaged by winter injury. Other stresses, such as transplant shock, excess moisture, shearing, scorch from excess sunlight, or scale infestations can also increase a host's susceptibility to the disease. The plants in photo 2 were also infested with Oystershell Scale, likely contributing to the plants susceptibility.
Disease management should begin by removing and destroying all severely infected plant parts. The next step should focus on alleviating any known stresses and by controlling scales and other pests. Remove accumulated leaf debris that may hold moisture. Protect from excess sunlight or desiccating winter winds. Periodically thinning pachysandra beds will increase air circulation and allow plants to dry quickly. Chemical controls should be used as your last option. Fungicides can be used to prevent new infections. Products with the active ingredients chlorothalonil or mancozeb are labeled for homeowner use. Products with chlorothalonil, thiophanate-methyl, mancozeb and copper based active ingredients are labeled for used in Illinois by commercial applicators. (Travis Cleveland)
Author:
Travis Cleveland