October 22, 2013
Boxwood blight has come to Ashe County, N.C. State Extension Agent Travis Birdsell announced this month.
Ashe’s first case of the ornamental plant disease was confirmed in July, but other areas in the High Country have already seen some damage. Earlier this month, a two-acre field of infected boxwoods in Alleghany County was burned to contain the blight, Birdsell said.
The blight could the hurt the region’s wreath industry, which uses boxwood tips and cuttings, he said.
Plants affected by the blight develop spots on leaves and stems, and the leaves drop off, starting at the bottom of the plant. Plants usually do not completely die, but their appearance is ruined.
The fungus that causes boxwood blight was first discovered in the United Kingdom in the mid-1990s, causing a severe blight disease on boxwood (Buxus species). It is now widespread throughout most of Europe, and in native stands of boxwood.
In October 2011, this fungus was found for the first time in the U.S. on English and American boxwood samples collected from N.C. and Connecticut. Since then, it has also been found in Delaware, Maryland, Massachusetts, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island and Virginia, as well as in British Columbia, Ontario, and Quebec.
The greatest potential for long-distance transport of boxwood blight is the movement of infected plants, cuttings and tools. The fungus has the potential to spread throughout the boxwood tip production areas of N.C., and other states through the use of contaminated tools and burlap carrying-sacks during tip harvest.
It is also showing up in fields along roads which are used to transport infected plants in open vehicles.
Another way it spreads is on contaminated tools and workers. The fungus spores are very sticky, and will stick to tools and equipment, as well as animals such as deer and dogs.
Spores can also be moved by water, in splashing rain, flood water, overhead irrigation, or in droplets carried by the wind. Spores are not likely to travel long distances by wind alone.
Spread of this fungus will cause significant long-term losses of boxwood plants in both natural/landscape areas as well as in production fields. Plants growing in shaded areas are at especially high risk.
Symptoms of box blight include dark- or light-brown, circular leaf spots often with darker margins, dark stem cankers or streaks, straw- to bronze-colored blighted foliage and sudden leaf drop. Leaf spots may grow together to eventually cover the entire leaf.
Blighting can occur suddenly with complete leaf loss under warm (60 to 80°F) and humid conditions.
Limiting the spread of this contagious fungus can be accomplished by always following good sanitation practices when cutting boxwood tips. This includes:
• Disinfecting tools in between different blocks of plants, and especially in between different field locations,
• Wearing clean disposable coveralls or launder clothes between fields, or wear arm and leg protectors that can be treated with one of the sanitizing agents listed below,
• Washing off debris/dirt entirely from soles of shoes in between different boxwood fields or landscapes in counties suspected to have boxwood blight,
• Ensuring that any burlap or material used to bundle cuttings is new or previously unused,
• Assembling wreaths away from existing boxwood plantings, and never discarding boxwood waste material where it could contaminate other boxwood plants.
The best way to sanitize tools is to dip them for 10 seconds into one of the following solutions and allow them to dry:
• Lysol Disinfectant Concentrate at 2.5 fl ounces (5 tablespoons) to one quart water
• Clorox or other brands of household bleach mixed 1 part bleach to 9 parts clean water, mixed fresh each day), or
• ZeroTol at 2.5 fl ounces to one gallon water
For more information on the best sanitizing solutions as well as other information about the disease, go to http://go.ncsu.edu/boxwood_blight_links.