Alternatives to Boxwoods Ken Cote Indiana DNR, Division of - - PowerPoint PPT Presentation

Alternatives to Boxwoods

Ken Cote Indiana DNR, Division of Entomology and Plant Pathology

Overview

• Boxwood Blight Symptoms and Signs
• Boxwood Blight Survey
• Uses and forms of other plants
• How can you protect your nursery

What is Boxwood Blight

• Fungus
• Cylindrocladium

psuedonaviculatum

• Warm Moist Conditions
• Temps 41-86⁰F, 77⁰F

Optimum

• Above 91⁰F kills mycelia
• Microsclerotia are

produced.

• Survive up to 5 years in leaf

debris.

Where is boxwood Blight

• Confirmed cases in

– OH, PA, NY, VA, NC, MD, OR, CT, MA, RI – Canada (BC, ON)

• Not yet found in Indiana.

Symptoms

Plants develop small, black leaf spots Rapid progression symptoms resulting in leaf drop and small black stem cankers.

Infected plants on residential property

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Leaf Spots

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Blighted leaves, stem lesions, and defoliation.

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Black stem cankers and lesions

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Foliar symptoms: note leaf debris

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Infected boxwood and pachysandra

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Symptoms on pachysandra in landscape

www.ct.gov/caes

Sharon Douglas, Connecticut Ag Experiment Station

Volutella Blight Looks Similar

• Causes branch

dieback

• Infects winter

injured plants

• Both Boxwood

Blight and Volutella can occur at same time

• Get lab results!

Melodie Putnam, 2008

Boxwood Blight Survey

• 67 locations
• 34 Nursery Dealers
• 33 Certified Nurseries.
• No symptoms found out of 46,000 plus plants

inspected

• Too hot for disease in 2012.

Boxwood Blight Counties Survey 2012

Boxwood Blight Survey Cultivars Found

• Green Mtn.
• Cranberry Creek
• North Starr
• Northern Charm
• Suffruticosa
• Chicagoland Green
• Baby Gem
• Gordo
• Golden Dream
• Franklin Gem
• Green Gem
• Green Borders
• Green Velvet
• Green Tower
• Variegated English
• Korean
• Rotundifolia
• Shadow Sentry
• Vadar Valley
• Winter Beauty
• Winter Gem
• Winter Green

Boxwood Blight Survey

Boxwoods from: 13 states, 1 Canadian Province CA, IL,IN, KY, MI, OK, TN, and WI. Boxwoods found from:

• Connecticut, Maryland,

Ohio, Oregon, Pennsylvania

• British Columbia,

Canada

• This may pose a risk?

What if Boxwood Blight Gets Here?

• Sites will be managed under our clean plant

laws.

• Landowners will be requested to follow best

management practices to contain spread.

• Deep burial or burning.
• Protect adjacent, asymptomtic plants with

fungicides.

• Fungicides are labeled for Cylindrocladium,

more research is needed.

• Will we loose Boxwoods?

When Choosing Alternatives to Boxwood:

Consider Plant Form Consider Plant Function Consider Plant Adaptability

PLANTS SIMILAR IN SHAPE

Inkberry Holly Ilex glabra

• Salt tolerant
• Adaptable to wet

conditions

• High soil pH can lead

to chlorosis

• Leaf drop can be a

problem

• cv. Shamrock, Green

Magic

• Southern red mite

Green Magic Inkberry Holly

Shamrock Inkberry Holly

Leaf Retention Issues

Japanese Holly Ilex crenata

• Best look alike
• Hardiness varies among

cultivars

• Chlorosis in high pH

soils

• cv. Convexa (very

hardy)

• Green luster in photo

Uknown Cultivar of Japanese Holly

Chlorosis in high pH sutiations

Sky pencil: good replacement of Graham Blandy Boxwood

Ilex crenata ‘Chesapeake’

Dwarf Forms of Norway Spruce Picea abies

• Many forms available
• Highly adaptable
• Probably one of the

better spruces for IN

• Mites can be a problem
• Bagworm

Picea abies ‘Pumila’

Dwarf Alberta Spruce Picea glauca ‘Conica’

• Slow growing rounded

forms, conical forms

• Tolerant of shearing
• Topiary forms available

in trade

• Less tolerant of shade

and shearing than boxwood

• Spruce spider mite

magnets

Other closely related forms

Blue Hollies Ilex x meserveae

• Fairly adaptable to

Indiana soils

• Prefer acid, but doing
• kay at many unlikely

locations

• Tolerant of shearing
• Especially cultivar

China Girl or China Boy

China Girl Holly

Little Rascal Holly Ilex x Mondo

• Very low growing tight

form

• I do not have a great

deal of experience with this plant

• Seen winter injury in

parking lot plantings

Globe Arborvitae Thuja occidentalis

• Cultivars Tiny Tim and

Hetz Midget

• Slow growing forms

that require little maintenance

• Mites and bagworm
• Drought injury in 2012

• Mr. Bowling Ball

Thuja occidentalis ‘Bobazam’

Yew cultivars Taxus sp.

• Many forms available
• May already be over

used?

• Very tolerant of

shearing and some shade tolerance

• Root rot and edema

can be issues in wet soils

Boxleaf Euonymus Euonymus japonica ‘Microphyllus’

• Plant is similar in

appearance

• May not be winter

hardy in northern IN

• Scale, anthracnose and

crown gall can be a problem

• Prefers well drained

soil

Not Euonymus!

PLANTS FOR HEDGES AND PARTERRES

Bayberry Myrica pennsylvanica

• Coarser in texture
• Highly adaptable
• Tolerates shearing
• More pH adaptable

than Inkberry holly

• Not reliably evergreen

in Indiana

• May be ecotypes in

trade

Bayberry Hedge

Stoloniferous

English Ivy Hedera helix

• Take sun or shade
• Can be sheared into

many shapes

• Often gets twospotted

spider mites when used in this manner

• Can be invasive

Lavendar Lanvendula cultivars

• Tolerant of shearing
• Cultivars like Hidcote

and Munstead stay fairly low

• Probably more hardy

than Grey Green Santolina

• Not that tolerant of

wet soils

• Loved the 2012

summer

How Can I Protect My Nursery?

• Segregate boxwoods from states that have

the blight

• Make sure nursery has been inspected for

blight

• Hold plants for 4 weeks, inspect once a week

for symptoms

• Place plants on landscape fabric so debris can

be easily collected

How Can I Protect My Nursery?

• Obtain a fungicide history on boxwood

imported to nursery from high risk states

• Avoid over head irrigation
• Maintain spacing for good air circulation
• Avoid pruning or working in wet plants
• Disinfect pruning shears and other tools with

70% ETOH, 10% Bleach, Lysol, Zero Tol or Green Shield.

How Can I Protect My Nursery?

• Disinfect all pots with 10% bleach before

repotting boxwoods

• Do not compost dead boxwoods or bring

boxwoods back to nursery cull piles

• Clean all tools and boots between job sites

that have boxwoods

• Remember, there is an asymptomatic stage

What to do for suspect shipments

• Contact your DNR nursery inspector
• We will get laboratory confirmation for you
• Symptomatic plants, containers and

associated soil need to be mitigated

• Asymptomatic plants will need to be treated

with a fungicide and monitored

DNR Contact Information

• 1-866- NO EXOTIC
• 317-232-4120 DNR

Entomology

• Ken Cote 812-332-2241
• kcote@dnr.in.gov