How to manage Volutella blight in pachysandra
I’ve heard from several gardeners recently about an issue they’re having with their pachysandra. During last year’s growing season, the plants developed black blotches on their leaves and eventually the plants turned mushy and died.
Pachysandra is a popular ground cover, but unfortunately, a stem and leaf blight called Volutella is becoming more and more common in our area, especially during wet growing seasons.
Volutella infections tend to be more problematic in weak or overcrowded pachysandra patches. First, you’ll see small, dark blotches on the leaves and stems. These blotches have lighter and darker zones that look like irregular concentric rings. Sometimes you can see pinkish spore clusters, too. The blotches increase in size throughout the season until the entire leaf and stem turns black and dies. If left untreated, Volutella can wipe out an entire bed of pachysandra.
Be sure your pachysandra stays hydrated during times of drought, but only water deeply and in the morning to allow the foliage time to dry before nightfall. Water only when absolutely necessary. Like other fungal diseases, Volutella thrives in wet conditions. Volutella is often problematic in gardens that use an automatic sprinkler system that waters the landscape regularly, regardless of whether or not the conditions call for it.
To prevent this disease, thin overcrowded pachysandra every few years to encourage good air circulation and reduce competition. Do not mulch pachysandra with shredded bark products as these heavy mulches hold water against the plant stems, again leading to fungal issues. For the same reason, also rake out any fallen leaves and debris each fall.
The next line of defense against Volutella is a good spring haircut. If you had symptoms of Volutella in your pachysandra patch last year, mow your entire pachysandra patch all the way down to the ground within the next week or two.
Use a lawn mower or a string trimmer for the job. Then, vigorously rake up and dispose of all the debris to remove all diseased plant parts that may be harboring spores. New growth will occur within a few days. You should not have to do this every year, but doing so discourages the disease and promotes lots of new growth.
If you have had this problem for two or more years in a row, you can also take preventative action with applications of an organic fungicide. Once the new growth begins to appear, apply a biological fungicide, such as Serenade — Bacillus subtilis, two to three times. Time the applications at 14-day intervals and follow all label instructions carefully.
Pachysandra is also prone to winter injury, but the two issues are very different. Winter injury appears as light tan blotches, also on the leaves, but it does not have the concentric ring pattern typical of stem and leaf blight. However, winter injury can also be removed by mowing your pachysandra patch to the ground in spring to stimulate new growth.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.