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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.


Black stem cankers and lesions

www.ct.gov/caes


Foliar symptoms: note leaf debris


Infected boxwood and pachysandra

www.ct.gov/caes


Symptoms on pachysandra in landscape

www.ct.gov/caes


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 okay at many unlikely locations


• 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


• 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

• [email protected]

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