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BOXWOOD BLIGHT A NEW DISEASEBOXWOOD BLIGHT, A NEW DISEASEOF BOXWOOD IN THE U.S.
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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 seasong
Boxwood cuttings, plants in containers and those established for decades are susceptible
F i id i d l 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
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BOXWOOD BLIGHT TIME LINEBOXWOOD BLIGHT TIME LINE
First reported in the United Kingdom in mid 1990’s (now considered widespreadmid‐1990 s (now considered widespread throughout Europe)
Reported in New Zealand in 2002 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
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THE PATHOGENTHE PATHOGEN
Cylindrocladium buxicola (syn C. pseudonaviculatum)
L. Lacey & K.Ivors, NCSU
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BOXWOOD BLIGHTS *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
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BOXWOOD BLIGHT SIGNS*BOXWOOD BLIGHT SIGNS
During humid, wet conditions the fungus may sporulate on the underside of leaves and stemsp
Spore masses are white on infected leaves and stems
* Sign – visible signs of the pathogen (masses of spores, mycelium)
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SIGNS AND SYMPTOMS OFB BBOXWOOD BLIGHT
Photos courtesy of S. Douglas, CT Ag Exp Station
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BOXWOOD BLIGHT, SYMPTOMS ON STEM
Photo courtesy of S. Douglas, CT Ag Exp Station
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BOXWOOD BLIGHT DAMAGE TOC P BCUTTINGS IN PROPAGATION BED
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CONTAINER NURSERY: PLANTS7 10 WERE DEFOLIATED IN 7-10 DAYS
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BOXWOOD BLIGHT OFBBOXWOOD
Defoliation of boxwood in one season d bdue to box blight
Photos courtesy of M. Inman, CT Ag Exp Station
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BOXWOOD BLIGHTBOXWOOD BLIGHT
D f li i fDefoliation of box wood due to box blight infection
Photo courtesy of S. Douglas, CT Ag Exp Station
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SPREADSPREAD
Short distance the fungal spores can be splash dispersed or by wind driven rainsplash dispersed or by wind driven rain
Long distance spread via infected plant material
Wet foliage and warm, humid conditions favor disease developmentp
Fungus can survive for years in leaf litter via micro‐sclerotia
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Host Cultivar
Buxus microphylla var. japonica ‘North Star’
‘Green Beauty’
‘Baby Gem’
Buxus sempervirens ‘Suffruticosa’
‘Elegantissima’
‘Artic Emerald’
‘Jade Pillar’ght in CT
Jade Pillar
‘Graham Blandy’
Buxus sinica var. insularis ‘Winter Gem’
oxwoo
d Blig
‘Winter Green’
Buxus sinica var. insularis X Buxus ‘Green Mountain’
sempervirens hybrid ‘Green Gem’Hosts fo
r Bo
p y
‘Green Velvet’
‘Chicagoland’
‘Green Ice’
H
‘Green Ice’
‘Big Leaf Gordo’
All commercially produced boxwood species/cultivars are considered hosts
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BEST MANAGEMENTP LPRACTICES 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 finformation
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BEST MANAGEMENTP NPRACTICES 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 nurseryg y
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 suspicioussee anything suspicious
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LOOK-A-LIKE DISEASESLOOK A LIKE DISEASES
Phytophthora root rot
Volutella blight
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PHYTOPHTHORA ROOT ROTPHYTOPHTHORA ROOT ROT
Roots are killed; foliage dies once roots are deadroots are dead
Problem in nurseries and newly established plants in landscapes
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PHYTOPHTHORA ROOT ROTPHYTOPHTHORA ROOT ROT
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PHYTOPHTHORA ROOT ROTPHYTOPHTHORA ROOT ROT
Healthy Phytophthora root rot; note discolored roots
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VOLUTELLA BLIGHTVOLUTELLA BLIGHT
A minor problem compared to boxwood blight
Shoots may be killed
Sign of disease‐ pink‐to‐salmon colored spores lon leaves
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VOLUTELLA BLIGHTVOLUTELLA BLIGHT
P Bachi, Univ of KY, ipmimages.orgS Douglas, CT Ag Exp Stat
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FURTHER READINGFURTHER READING
Boxwood Blight, CT Ag Exp Station
Boxwood Blight, NC State University