Can Lawn Mowing and Maintenance Spread Boxwood Blight?

By Mike Goatley, Ph.D., Virginia Tech School of Plant and Environmental Sciences

Question: A client has English boxwoods and is worried about the possibility of our lawn service company spreading the disease around their property. Are there any concerns?

Answer from: Elizabeth Bush and Mary Ann Hansen, Extension Plant Pathologists, in the Plant Disease Clinic in the School of Plant and Environmental Sciences at Virginia Tech.

Boxwood blight is a fungal disease that was first found in Virginia in 2011 and has subsequently spread to many parts of Virginia. When susceptible boxwood, such as English boxwood, are infected, management of the disease by fungicides is not effective. The disease is devastating to landscapes with susceptible boxwood (Figure 1).

FIGURE 1: The boxwood blight fungus causes severe defoliation on susceptible boxwood. Photo by Adria Bordas

How the boxwood blight fungus spreads.

In Virginia, initial introduction and spread of the disease occurred by planting infected boxwood. Subsequently, the disease spread to nearby boxwood in localized areas (e.g. neighborhoods, towns). The boxwood blight fungus produces sticky spores, which easily adhere to clothing, equipment, animals, shoes, etc. and enable the pathogen to hitchhike to new locations on these items. It can also be spread to new locations in infected leaves that are blown by mowers or leaf blowers. Lawn maintenance professionals should be aware that activities such as mowing and leaf blowing can spread the disease to nearby landscapes. Additionally, boxwood blight-infested lawn maintenance equipment (e.g. spreaders, hoses, mowers, vehicles) or workers with boots or clothing infested with the sticky spores can spread the fungus to a new location. Spread of boxwood blight on professional lawn mowers moving from property to property was suspected to have occurred in several Virginia localities last year. This resulted in outbreaks of the disease on boxwood in entire neighborhoods and at least one small historic Virginia town with landscapes highly populated by susceptible English and American boxwood. This occurred during a period of prolonged rainfall, which resulted in epidemic levels of the disease and devasted boxwood landscapes in the affected locations.

Tactics to avoid spread of boxwood blight.

Educate employees to recognize boxwood and boxwood blight symptoms. Laminated boxwood blight wallet cards are available through your local Extension office (https:// ext.vt.edu/offices.html); these have images of the characteristic symptoms of the disease and include a link to the Boxwood Blight Task Force website. This website includes comprehensive information on the disease, as well as an image gallery of symptoms of the disease and downloadable best management practices (BMPs). The wallet card is available in both English and Spanish. We recommend distributing a wallet card to your employees and familiarizing yourself with the tactics to avoid spreading the disease detailed in the BMPs.

When possible, wash equipment between properties, especially if you have worked on a property where you suspect boxwood blight may be present. It is advisable to sanitize equipment as well (Sanitation recommendations are available on the Boxwood Blight website.) Cleaning and sanitizing the undercarriage of the mower deck at the end of the day is a relatively simple management strategy that would minimize the chance of spreading the disease. If you have a customer with a highly valued boxwood landscape, discuss the situation with the customer; there may be alternative approaches to maintaining such landscapes (e.g. using the customer’s mower). You can also organize the daily work-flow to mitigate the risk of spreading boxwood blight. For example, if a ‘risk level’ for boxwood blight is known among properties, always work on properties at low risk of having boxwood blight first and move to higher risk properties later in the day. If boxwood blight is diagnosed in a landscape, avoid that landscape until the boxwood and boxwood leaf debris have been removed to minimize the risk of spreading the disease.