Boxwood blight is a fatal plant pathogen on boxwoods in the landscape and commercial industry. DNR nursery inspectors have recently made multiple discoveries of infected holiday greenery at garden centers around the state.
Symptoms of infected boxwood leaves include dark-brown leaf spots with a tan center. Eventually, leaves turn brown from the tip down and drop from the stem, causing multiple bare branches. Long, thin black streaks can also be seen on infected stems.
In 2011 a fungus called boxwood blight was found in North Carolina. Since then, it has spread to 24 states, including Indiana where it was found in December of 2018.
The exact origin and source of the introduction of this disease to the U.S. is not known. There have been multiple interceptions at garden centers and on Christmas decorations in the state.
There are other diseases that can look similar, but boxwood blight is distinguished by producing rapid defoliation of infected plants resulting in death. Fungal spores are viable in soil for five years.
The best approach to this pathogen is to prevent its introduction into the landscape. Preventive treatments are available, but these treatments are only designed to protect your plants from becoming infected with the fungus.
All boxwoods, Pachysandra and sweet box are susceptible to boxwood blight. The fungus can be transported on symptomatic and asymptomatic plants. A one-month latency period may occur before plants show symptoms, however once symptoms develop it is too late to save them.
Early detection of this disease is critical to reduce economic impact. Homeowners are encouraged to report suspicious plants. If your boxwoods develop sudden leaf drop: contact your local Purdue Cooperative Extension agent or the DNR, Division of Entomology and Plant Pathology at 1-866-NOEXOTIC.