Government Affairs: Will compost be the end of boxwoods?

November 12, 2015 - By Gregg Robertson

Boxwoods have been one of the “go to” landscape plants for landscape contractors and homeowners in the Eastern and Midwestern U.S., but boxwoods’ days may be numbered. A fungal disease that causes boxwood leaves to yellow and drop, eventually leading to the weakening and eventual death of the boxwood from secondary diseases, is gaining a foothold.

Boxwood blight, until recently a disease known only in England and European countries, found its way to the U.S. in 2011. It has since been found in 12 states: Connecticut, Delaware, Maryland, Massachusetts, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island and Virginia.

The disease is difficult to control with fungicides and the recommended remedy for diseased plants is to remove and destroy them by burning or burying them deeply. The fungus that causes the disease persists in soil for years, requiring that the infected soil be sterilized by high heat before boxwoods can be successfully replanted in the same area.

The disease is spread by contact with infected plants, leaf litter or soil. Humans also can spread the disease by using contaminated tools and carrying the fungal spores on their shoes and clothing. In the U.S., the disease has been spread most commonly by the movement of diseased plants from nurseries through marketing channels such as plant rewholesalers, big box stores and garden centers.

The U.S. Department of Agriculture and state departments of agriculture have well-established regulatory and inspection programs and methods of tracing contaminated plant shipments and have been diligent in tracking down and destroying blighted boxwoods.

But another way that the disease can be spread is through contaminated compost. Compost contaminated with the boxwood blight fungus will be more insidious and more difficult to control than plant shipments.

Compost conundrum

The potential problem of contaminated compost has its roots in the late 1980s and early 1990s when many states, facing rapidly filling sanitary landfill space, began mandatory recycling and composting programs to reduce the amount of trash flowing into landfills. A key part of many of these state recycling and composting programs was to make it illegal to dispose of yard waste and other organic material in landfills and to direct this material to municipal and private composting operations.

These state laws and programs have been in place for about 25 years and they’re now routine and well established. Landscape contractors and the general public know they should take their yard waste to a municipal or private composting facility. While at the composting facility, many will pick up a load of compost or mulch from last year’s yard waste to spread on their gardens–mulch that could be contaminated with fungus spores from the blighted boxwoods that unknowingly were disposed of with other yard waste last year.

As yet, there has been no verified case of compost spreading boxwood blight. But it’s only a matter of time, especially in those states with landfill bans on yard waste. Eight of the twelve states in which boxwood blight has been found have laws directing yard waste to composting facilities rather than to landfills: Delaware, Maryland, Massachusetts, New Jersey, North Carolina, Ohio, Pennsylvania and Rhode Island.

The solution to this problem is for states with yard-waste landfill bans to create an exception for boxwoods–any boxwoods, whether blighted or not. The safest way to dispose of blighted boxwoods is by incineration or landfill disposal.

Second, an education program will need to be mounted in to tell the public, landscape contractors, waste haulers, landfills operators, compost operators, big box stores and garden centers about the exception and to enlist their assistance is keeping boxwoods out of the compost feedstock.

If we allow another spring clean-up season to come and go without taking these two steps, it may be too late to save the boxwood as a viable landscape plant in this country.