Boxwood Blight Task Force

The following BMPs are guidelines for boxwood growers to avoid introduction of the boxwood blight pathogen or, if the disease is already present, to manage the disease in the most effective manner and avoid spread of the disease to new locations. Each BMP is specialized for individual boxwood growing situations.

Downloadable Decision Options

Downloadable Expanding on Boxwood Blight Management Decision Guide

This decision guide is a general starting place for anyone who has landscape boxwood that have been diagnosed with Boxwood Blight. For
further details to guide your management decision we recommend 1) reading the "Expanding on the Boxwood Blight Management Decision
Guide" and 2) reviewing additional information on the Virginia Boxwood Blight Task Force website (https://ext.vt.edu/agriculture/commercialhorticulture/
boxwood-blight.html).

* This alternative approach was proposed in response to reports of growers who rejected the option of removal of very large
American boxwood. However, there is not enough research at this time to know how efficacious this approach will be over time in
Virginia and this approach poses risks. It is important to keep in mind that although visibly diseased branches may be pruned out,
pruning out affected branches will not eliminate the Boxwood Blight fungus from American boxwood. Further sporulation of the
fungus on the American boxwood is likely and these spores can serve as a source of inoculum for uninfected boxwood in the
landscape. Also note that weather conditions in Virginia are generally favorable for development of Boxwood Blight and repeated
fungicide sprays may be necessary for much of the year on a 7-day to 2-week schedule, depending on product label directions and
weather conditions. Additionally, it can be difficult to keep up with the sprays required, particularly under prolonged rainy weather.
English boxwood (Buxus sempervirens 'Suffruticosa') is extremely susceptible to Boxwood Blight; therefore, no one is suggesting
using this approach on infected English boxwood.

Expanding on the Boxwood Blight Management Decision Guide

Boxwood blight is a serious and contagious boxwood disease.  Management decisions will influence the disease progression.  Although boxwood blight is serious and spreading in many communities in Virginia, boxwood remains a valuable landscape ornamental. Successful and sustainable landscaping with boxwood currently requires knowledge, attention and care.

Option 1—Do nothing

1. Infected susceptible boxwood will decline and eventually die.
2. Disease will spread in landscape and locally (e.g. neighborhood, town).

Option 2—Remediation after confirmatory diagnosis of boxwood blight

1. Remove diseased, susceptible boxwood promptly OR, if American boxwood, consider alternative approach for American* (below).
2. Remove leaf litter from soil surface (e.g. raking/sweeping, vacuuming, or by using a burn torch/agricultural flamer.
   1. Diseased boxwood, leaf debris and soil should be double-bagged and removed to the sanitary landfill OR buried 2' deep in soil OR burned (if allowed in your locality).
   2. Do not compost boxwood debris or plant material and do not place curbside for brush pickup, since this will spread the disease to new locations via wind-blown leaves and/or municipal mulch.
   3. Because the fungal spores can stick to tools, equipment, etc., sanitize all tools, equipment, tarps, shoes, gloves, etc., used after removing plants to prevent spread of fungal inoculum to healthy boxwood. For a list of sanitizer recommendations, refer to the Boxwood Blight Task Force website at https://ext.vt.edu/agriculture/commercial-horticulture/boxwood-blight.html. It is recommended that vehicles that have been potentially exposed to the boxwood blight fungus be thoroughly washed of debris (e.g. cleaned at an auto spa).
3. Mulch soil surface under existing boxwood and/or replacement boxwood to a depth of approximately 2”. (In research studies, a 2”- to 4”-inch mulch layer effectively prevented splash dispersal of boxwood blight spores to lower leaves, but a shallow mulch layer is a better cultural choice for boxwood.)
4. If leaf debris has been incorporated into the soil, removing soil to a depth of 8" to 12" may help eliminate inoculum of the pathogen, but this is often impractical.
5. Apply preventative fungicides, as recommended on the product label, to the infected and non-infected boxwood in the vicinity whenever weather conditions are favorable for disease development. (Note that weather conditions in Virginia are favorable much of the year.)
   1. Products containing the active ingredient, chlorothalonil, and labeled for use on landscape ornamentals, have been shown effective when used preventatively (before the disease is present) on boxwood. Professional landscapers have additional active ingredient options. Refer to the fungicide information on the Virginia Boxwood Blight Task Force website for more fungicide information.
   2. Favorable weather conditions for development of boxwood blight: Applications should be made in spring when daytime temperatures reach 60F and prolonged rain is predicted. You can stop spraying when daytime temperatures are regularly above 80F in the summer. Begin sprays again in the fall when temperatures drop below 80F and prolonged rain is predicted. In winter when temperatures regularly stay below 60F you do not need to spray, but pay attention to forecasts for prolonged periods of mild winter weather and rainfall when fungicides might need to be in place.
6. Monitor other boxwood, pachysandra, and sweetbox in the landscape for development of boxwood blight symptoms. (Other plants in the boxwood plant family, Buxaceae, including Pachysandra spp. and Sarcococca spp., are also susceptible to the disease and should be monitored for boxwood blight. Since they can harbor inoculum for new infections on susceptible boxwood, they should be removed if susceptible boxwood are also in the landscape.)
7. For recommendations on replacement shrubbery and/or boxwood refer to information in “Option 3” below.

*Alternative approach for American boxwood (Buxus sempervirens): Currently some researchers are suggesting that while American boxwood is very susceptible to the Boxwood Blight fungus, it may recover (i.e. produce healthy new growth) during dry weather conditions. Additionally, there have been reports of reluctance of home growers and/or landscape professionals to remove very large American boxwood. For this reason, we have provided an alternative approach for infected American boxwood:

1.  Prune and remove diseased branches on American boxwood.

                                         i.    Because the fungal spores can stick to tools, equipment, etc., sanitize all tools, equipment, tarps, shoes, gloves, etc., used after removing plants to prevent spread of fungal inoculum to healthy boxwood.

                                        ii.    Follow Steps 2 through 6 (above).

1.  Precautionary note: This approach may be an acceptable alternative to complete removal of infected American boxwood. However, there is not enough research at this time to know how efficacious this approach will be over time in Virginia. Also, keep in mind that although visibly diseased branches may be pruned out, pruning out affected branches will not eliminate the fungus from American boxwood. Further sporulation of the fungus on the American boxwood is likely and these spores can serve as a source of inoculum for healthy, susceptible boxwood in the landscape and neighborhood landscapes. Also note that weather conditions in Virginia are generally favorable for development of boxwood blight and repeated fungicide sprays will be necessary for much of the year on a 7-day to 2-week schedule, depending on product label directions and weather conditions. English boxwood (Buxus sempervirens 'Suffruticosa') is extremely susceptible to Boxwood Blight; therefore, no one is suggesting that this approach be used on infected English boxwood.

Option 3—Replace susceptible boxwood with tolerant (resistant) boxwood cultivars and/or shrub species not susceptible to boxwood blight (Currently there are no boxwood immune to boxwood blight; however, there are boxwood cultivars that are “tolerant” (also termed “resistant”) to boxwood blight. The boxwood blight pathogen may sporulate on tolerant cultivars, but tolerant cultivars do not develop noticeable symptoms of the disease and are not negatively affected by boxwood blight.

1. If replacing susceptible boxwood with boxwood blight tolerant (resistant) cultivars:
   1. It is advisable to purchase replacement boxwood from nurseries that participate in the Boxwood Blight Cleanliness Program (BBCP). A list of participating BBCP nurseries is available at http://www.vdacs.virginia.gov/plant-industry-services-boxwood-blight.shtml . Home growers who want to buy boxwood produced by nurseries in the BBCP will have to do some work to identify a retail store/nursery that sells such boxwood. It is advisable to identify a retail operation that exclusively sells only boxwood produced in the BBCP to minimize the chance of introducing the disease into a landscape.
2. Only plants in the Buxaceae family (e.g. boxwood [Buxus spp.], pachysandra [Pachysandra spp.] and sweetbox [Sarcoccca spp.] have been reported susceptible to boxwood blight in the landscape. If you are considering replacing susceptible boxwood with other shrub species, refer to the Problem-free Shrubs for Virginia Landscapes (http://pubs.ext.vt.edu/450/450-236/450-236.html) Virginia Cooperative Extension fact sheet to avoid species of shrubs commonly afflicted with disease problems in Virginia.

Boxwood Blight FAQs

• Boxwood Blight Image Gallery

Comparison of Boxwood Blight to other Boxwood Problems

No boxwood cultivars are currently immune to boxwood blight (immune=unable to be infected by the boxwood pathogen). However, there are boxwood cultivars that show only very few minor or barely noticeable symptoms of the disease, despite being infected with the boxwood blight fungus. Such cultivars are characterized as boxwood blight “resistant” or “tolerant”.  Boxwood cultivars susceptible to boxwood blight should be avoided.

The tables below list some boxwood that were shown to be resistant to both boxwood blight and leafminer (Table 1) or very susceptible (Table 2) to the boxwood blight pathogen in research trials. New boxwood blight-resistant cultivars will continue to be released into the marketplace and the list of resistant boxwood in Table 1 is not exhaustive. 

Table 1. Cultivars of Boxwood resistant to both boxwood blight and leafminer.

Table 2. Some Cultivars Very Susceptible to Boxwood Blight

Downloadable Other Hosts

Only plants in the Buxaceae family (e.g. boxwood [Buxus spp.], pachysandra [Pachysandra spp.] and sweetbox [Sarcoccca spp.] have been reported susceptible to boxwood blight in the landscape. Refer to Tables 1 and 2 for a list of species of pachysandra and sweet box reported in the literature as susceptible to boxwood blight.

Table 1. Pachysandra species and cultivars known to be susceptible to the boxwood blight pathogen

1.     Kong P, Likins TM, Hong CX. 2017. First report of Pachysandra terminalis leaf spot caused by Calonectria pseudonaviculata in Virginia. Plant Disease 101:509

2.     LaMondia JA. 2017. Pachysandra species and cultivar susceptibility to the boxwood blight pathogen, Calonectria pseudonaviculata. Plant Health Progress doi:10.1094/PHP-01-17-0005-RS

3.     LaMondia JA, Li DW, Marra RE, Douglas SM. 2012. First report of Cylindrocladium pseudonaviculatum causing leaf spot of Pachysandra terminalis. Plant Disease 96:1069

Table 2. Sarcococca (sweet box) species known to be susceptible to the boxwood blight pathogen

1.             Kong P, Likins TM, Hong CX. 2017. First report of blight of Sarcococca hookeriana var. humilis by Calonectria pseudonaviculata in Virginia. Plant Disease 101:247

2.             Kong P, Likins TM, Hong CX. 2017. First report of Pachysandra terminalis leaf spot caused by Calonectria pseudonaviculata in Virginia. Plant Disease 101:509

3.             LaMondia JA. 2017. Pachysandra species and cultivar susceptibility to the boxwood blight pathogen, Calonectria pseudonaviculata. Plant Health Progress doi:10.1094/PHP-01-17-0005-RS

4.             LaMondia JA, Li DW, Marra RE, Douglas SM. 2012. First report of Cylindrocladium pseudonaviculatum causing leaf spot of Pachysandra terminalis. Plant Disease 96:1069

5.             Malapi-Wight M, Salgado-Salazar C, Demers JE, Clement DL, Rane KK, Crouch JA. 2016. Sarcococca blight: use of whole-genome sequencing for fungal plant disease diagnosis. Plant Disease 100:1093-100

6.             Ryan C, Williams-Woodward J, Zhang DL. 2018. Susceptibility of Sarcococca taxa to boxwood blight by Calonectria pseudonaviculata. Proceedings of Southern Nursery Association Research Conference 62:64-7

Sanitizer recommendations for the boxwood blight pathogen

Note: Only ethanol products provide some control of microsclerotia and other pathogen structures (e.g. mycelium, spores, chlamydospores) in plant debris; thus, it is VERY important to wash off surface soil and/or debris before proceeding with any recommended sanitizing procedure.

Data compiled from: (1) Douglas, S.M., 2013.  Efficacy of sanitizing agents to refine best management practices for the boxwood blight pathogen Calonectria pseudonavicula. APS poster, Annual meeting , Aug. 10-14, Austin TX, (2) Shishkoff, N., 2014. Survival of microsclerotia of Calonectria pseudonaviculata (the boxwood blight pathogen) treated with a variety of sterilants. APS poster, Potomac Division Meeting, March 12–14, Annapolis, Maryland, (3) Dart, N. L., Hong, C. X., Allen, C., 2014.  Efficacy of bleach and ethanol as sanitizers on conidia and infected leaf tissue colonized with mycelium and microsclerotia of the boxwood blight pathogen, Calonectria pseudonaviculata. Unpublished.

Version 1, published December 2014

Downloadable Fungicide Guide

¹F=Fair, G=Good, E=Excellent

• Effectiveness ratings are based on limited research.  Results can vary depending on environmental conditions, formulation of a pesticide, and application method and timing. These ratings are intended as general guides only.
• Sources of efficacy information: Gehesquière B. (2014). Phd Thesis. Ghent University, Belgium; Ivors, et al. 2013. Plant Dis. Manag. Rep. 7:OT014. doi: 10.1094/PDMR07; LaMondia, J.A. 2015. Plant Dis. 99: in press; Henricot B. and Wedgwood E. 2013. Plant Health Progress. doi:10.1094/PHP-2013-1024-01-RS; and unpublished research.

²FRAC Group: classification based on fungicide mode of action (www.frac.info). Rotate any fungicide at risk of resistance development with products that have a different mode of action (i.e., in a different FRAC group).

It is the user’s responsibility to read and follow product label directions for all products. Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension does not endorse these products and does not intend discrimination against other products which also may be suitable. 

Published 2/26/15

El tizón de boxwood en viveros de producción comercial

• Boxwood Blight Cleanliness Program, Virginia Department of Agriculture and Consumer Services
• Boxwood Blight Management, Department of Plant Pathology, North Carolina State University
• Local Virginia Cooperative Extension Offices
• Plant Disease Clinic Disease Alerts