My pachysandra is dying off in patches. The leaves turn yellow, the vines wither away, and the roots rot, destroying the entire plant. This has been happening gradually for the last two years, including before the drought last year. This year it is extremely bad. Some of the plants look like the leaves have been stripped off too. My plantings are in the shade and do not have exposure to sun.
— Ellen Bauman, Genoa City, Wis.
Pachysandra is a shade-tolerant ground cover that will develop an overall yellow cast in too much sun. There can also be some burning at the leaf edges, but the plants will typically not wither completely away.
Your problem sounds like Volutella blight, a fungus that begins as small brown to tan spots on the leaves that enlarge to form blotches. These blotches can spread and join together, causing the foliage to die back. Concentric line patterns form within the brown spots as leaves yellow and fall. Infected stems will turn brown to black and die. Circular, spreading areas of diseased plants will be noticeable in the pachysandra planting as the disease progresses.
Volutella blight will be especially severe when the plants are crowded, and when wet and humid conditions prevail. Plants damaged by winter, stressed by drought or infested with insects will be more susceptible to this disease.
For your established bed of pachysandra, carefully remove all the severely infected plants and prune out all diseased parts. If the disease is caught in time, the plants that have been cut back to the ground may recover.It will be best to dispose of the infected plant material with the landscape waste. Be sure to disinfect your pruning shears with 70 percent rubbing alcohol or Lysol disinfectant after pruning out the infected stems and leaves. Continue removing any infected plants or plant parts throughout the growing season.
Fungicides such as mancozeb and maneb can be used to protect remaining plants and the new growth of any pachysandra that have been cut back. These treatments can help deter infection but will not cure infected plants. You would need to spray at seven- to 14-day intervals from spring until early summer. Be sure to carefully read and follow the directions on the label.
Monitor for pachysandra scale, small insects that will appear as white flecks on the leaves and stems. This insect can severely stress and kill pachysandra, so it will need to be treated if populations are high. Contact the Plant Information Service at the Chicago Botanic Garden (chicagobotanic.org/plantinfoservice or 847-835-0972) for advice on the right treatment.
Use good cultural practices to keep plants as healthy as possible, which will in turn reduce problems with insects and diseases. Water your pachysandra during drought periods and treat for insects as needed. Water early in the day so that the foliage will dry off before late afternoon.
Tim Johnson is director of horticulture for the Chicago Botanic Garden in Glencoe (chicagobotanic.org). Email questions to: sunday@tribune.com.
