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Boxwood Blight in Illinois

Please report suspect Boxwood Blight to the Department, or to the U of I Plant Clinic for Diagnosis.

Boxwood Blight is a fungal disease affecting boxwoods, and other plants in the Buxaceae family such as Pachysandra and Sarcococca species.  Though,​ there seems to be some significant tolerance within the Buxus genus itself, the most susceptible varieties include the most popular ones, being “English” and “American” boxwoods, both of which are very common in the Illinois production and landscape settings.

The disease was first described in the United Kingdom in the mid 1990s.  It was discovered in New Zealand in 2002, identified as a new species of fungus and given the name Cylindrocladium pseudonaviculatum.  The fungus causing the disease in the UK was named Cylindrocladium buxicola, but these are now known to be the same.  The disease was first confirmed in North America in 2011 in Connecticut and North Carolina, and has since been found in approximately 20 states.  In North America, with the implementation of ‘one fungus one name’, the pathogen is renamed Calonectria (syn. Cylindrocladium) for diagnostic purposes, with the North American confirmed species being Calonectria pseudonaviculatum, and the European species being Calonectria henricotae, which has not been found in North America to date.

Though Illinois had three separate detections in three counties late in 2016, we do not believe it is established in the state, nor widespread and prevalent, thus far​.  Boxwoods are a common and popular plant in North American landscapes, Illinois included, and make up a significant component of the nursery production and trade industry.  For this reason, we feel it is important to detect and manage this pest to prevent further introductions and spread.

It is generally agreed upon that the pathogen is not demonstrating the ability to move quickly or long-distance via air travel, or otherwise natural means.  However, the overwhelming means of rapid and long-distance conveyance (interstate) is movement of infected plant material. The potential for more localized movement (i.e. within a production setting, from property to property, etc.) exists via plant to plant contact,  contaminated tools, clothing, or other associated equipment that may have made contact with infected plants, in addition to local movement of infected plants or plant materials.  This seems to be a “cultural practices” issue, versus natural spread like EAB which we are all to​o familiar with.

Illinois residents should not be concerned with Boxwood Blight “showing up” in their landscapes naturally.  It will undoubtedly be introduced via infected plants or plant material, or perhaps through equipment or tools.  Residents are urged to keep a close eye on: any Boxwoods that were recently planted, plants in close proximity to newly installed plants, or established plants that may have been trimmed or pruned recently.  It is also recommended to purchase your plants from licensed sources, and maintain your plants to keep them vigorous.

Further information can be found at the following links: