1. Boxwood Blight, a new disease of boxwood in the U.S.
Alan Windham, Professor, Plant Pathology
Mark Windham, Professor, Plant Pathology
Anni Self, Plant Pathologist, TN Dept of Agriculture

2. Boxwood Blight, why the concern?
Boxwood is an important landscape plant in American gardens and a valuable crop produced by nurseries
This fungal disease attacks all commercially available boxwood species and cultivars
Boxwood blight can defoliate a boxwood in one season
Boxwood cuttings, plants in containers and those established for decades are susceptible
Fungicides give moderate to poor control
Has been found in 9 states in the U.S. (MA, RI, CT, NY, PA, MD, VA, NC, OR); this number will likely increase

3. Boxwood Blight Time Line
First reported in the United Kingdom in mid-1990’s (now considered widespread throughout Europe)
Reported in New Zealand in 2002
Reported in CT and NC in October 2011
By February 2012 reported in MA, MD, VA, RI,OR,NY, PA and British Columbia

4. The Pathogen Cylindrocladium buxicola (syn C. pseudonaviculatum)
L. Lacey & K.Ivors, NCSU

5. Boxwood Blight Symptoms*
Tan-to-brown circular spots on leaves
With time whole leaves turn brown and are shed
Tan-to-black lesions develop on twigs
Root system is not affected, at least initially; as plant declines the root system will be affected
* Disease symptoms – visible damage to leaves, stems or other plant parts

6. Boxwood Blight signs*
During humid, wet conditions the fungus may sporulate on the underside of leaves and stems
Spore masses are white on infected leaves and stems
* Sign – visible signs of the pathogen (masses of spores, mycelium)

7. Signs and Symptoms of Boxwood Blight
Photos courtesy of S. Douglas, CT Ag Exp Station

8. Boxwood Blight, symptoms on stem
Photo courtesy of S. Douglas, CT Ag Exp Station

9. Boxwood Blight Damage to Cuttings in Propagation Bed

10. Container Nursery: plants were defoliated in 7-10 days

11. Boxwood Blight of Boxwood
Defoliation of boxwood in one season due to box blight
Photos courtesy of M. Inman, CT Ag Exp Station

12. Boxwood Blight Defoliation of box wood due to box blight infection
Photo courtesy of S. Douglas, CT Ag Exp Station

13. Spread
Short distance the fungal spores can be splash dispersed or by wind driven rain
Long distance spread via infected plant material
Wet foliage and warm, humid conditions favor disease development
Fungus can survive for years in leaf litter via micro-sclerotia

14. Host
Cultivar
Buxus microphylla var. japonica
‘North Star’
‘Green Beauty’
‘Baby Gem’
Buxus sempervirens
‘Suffruticosa’
‘Elegantissima’
‘Artic Emerald’
‘Jade Pillar’
‘Graham Blandy’
Buxus sinica var. insularis
‘Winter Gem’
‘Winter Green’
Buxus sinica var. insularis X Buxus
‘Green Mountain’
sempervirens hybrid
‘Green Gem’
‘Green Velvet’
‘Chicagoland’
‘Green Ice’
‘Big Leaf Gordo’
Hosts for Boxwood Blight in CT
All commercially produced boxwood species/cultivars are considered hosts

15. Best Management Practices for Landscapes
Be extremely cautious if buying boxwood this season
Examine plants carefully before buying; if not healthy, walk away
Fungicides slow, but do not eliminate the disease
Isolate new plants from established plantings
Contact your local Extension Agent for more information

16. Best Management Practices for Nurseries
Train staff to recognize boxwood blight signs and symptoms
Closely inspect incoming boxwood and isolate new plants from older blocks of boxwood
Scatter boxwood blocks throughout nursery
If possible, use drip irrigation
Take cuttings for propagation from healthy plants
Keep up-to-date on developments in fungicide trials
Contact your plant inspector or Extension agent if you see anything suspicious

17. Look-a-like Diseases
Phytophthora root rot
Volutella blight

18. Phytophthora root Rot
Roots are killed; foliage dies once roots are dead
Problem in nurseries and newly established plants in landscapes

19. Phytophthora Root Rot

20. Phytophthora Root Rot Healthy
Phytophthora root rot; note discolored roots

21. Volutella Blight A minor problem compared to boxwood blight
Shoots may be killed
Sign of disease- pink-to-salmon colored spores on leaves

22. Volutella Blight S Douglas, CT Ag Exp Stat
P Bachi, Univ of KY, ipmimages.org

23. Further Reading Boxwood Blight, CT Ag Exp Station
Boxwood Blight, NC State University