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Alternatives to Boxwoods
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 Melodie Putnam, 2008 • Causes branch dieback • Infects winter injured plants • Both Boxwood Blight and Volutella can occur at same time • 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. 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 • 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
