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 Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Leaf Spots Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Blighted leaves, stem lesions, and defoliation. Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Black stem cankers and lesions Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Foliar symptoms: note leaf debris Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Infected boxwood and pachysandra Sharon Douglas, Connecticut Ag Experiment Station www.ct.gov/caes
Symptoms on pachysandra in landscape Sharon Douglas, Connecticut Ag Experiment Station 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 Melodie Putnam, 2008 • Get lab results!
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. Green Borders • • Cranberry Creek Green Velvet • • North Starr Green Tower • • Northern Charm Variegated English • • Suffruticosa Korean • • Chicagoland Green Rotundifolia • • Baby Gem Shadow Sentry • • Gordo Vadar Valley • • Golden Dream Winter Beauty • • Franklin Gem Winter Gem • • Green Gem Winter Green
Boxwood Blight Survey Boxwoods from: Boxwoods found from: • Connecticut, Maryland, 13 states, 1 Canadian Province Ohio, Oregon, Pennsylvania CA, IL,IN, KY, MI, OK, TN, • British Columbia, and WI. 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 • 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
Recommend
More recommend
