2016 Master Gardener Basic Disease Training

on Ornamentals

D.L. Clement

University of Maryland Extension Specialist

Keys to Problem Identification

Know the host plant

Check for symptoms and

signs

Check for part of the plant

affected

Check for patterns

Site history - ask questions!

Abiotic Factors

• Non-living, non-infectious, non-transmissible

– Environmental

• Climate extremes and exposure, temperature, moisture, light

• Nutrition, pH, soil type, organic matter

– Chemical

• Pesticides

• Deicing salt

• Air pollution

– Mechanical

• Lightning, hail, pruning, construction, embedded wires, grade changes

What are abiotic/non-infectious factors

• Immediate damage –injury

– Lightning

– Hail damage

– Ice damage

– Pesticide damage –phytotoxicity

– Dull mower injury

– Etc..

• Chronic damage – progressive over time

– Stress issues

– Nutrient deficiencies

– Drought

– Air pollution

– Poor drainage

– Etc..

Construction Equipment Damage

Poor Drainage

Poor Soil Conditions at Installation

Camden Yards Root rot on English ivy

Excessive Mulch

Exposed Root Ball

Root injury from construction

Old Road Bed Exposed during Installation

Herbicide damage on evergreens

Flooding Damage

Lightning damage

Winter Salt

Salt on Yew Salt on Spruce

Winter Dessication on Holly

Winter damage on Leyland

Normal fall color and needle drop on White Pine

Winter Color on evergreens

Yew with winter colorYew recovery from winter color

Non-Pathogenic FungiSlime mold Fuligo septica

Non-Pathogenic FungiSlime mold Fuligo septica

Mushrooms

Examples of Foliar Fungal Diseases

Sycamore Anthracnose

Anthracnose canker

Beech Anthracnose

Dogwood anthracnose

Discula Management

• Resistant C. florida cultivar

– Appalachian Spring

• Resistant trees

– C. kousa

– Dogwood hybrids i.e. Stellar series

• Fungicides

– chlorothalonil – (Daconil)

– myclobutanil – (Immunox)

– propaconazole – (Banner)

– thiophanate-methyl – (Cleary’s)

Powdery Mildew on Lilac

Powdery mildew on oak

Powdery Mildew on Dogwood

Powdery Mildew on Dogwood

pPPP

Powdery Mildew Management• Field Resistance

– Cherokee Brave

– Kousa cultivars and hybrids

• Resistant (C. florida cultivars)

– Jean’s Appalachian Snow

– Karen’s Appalachian Blush

– Kay’s Appalachian Mist

– Appalachian Joy

• Fungicides

– propiconazole – (Banner)

– myclobutanil – (Immunox)

– thiophanate-methyl – (Cleary’s)

Brown Rot on Kwansan Cherry

Brown Rot Management

• Chemical

– Lime-sulfur

– Chlorothalonil

– Captan

– Thiophanate-methyl

– Myclobutanil

• Cultural

– Thin canopy and remove twig cankers in the spring

Black spot on Rose

Cercospora leaf spot on rose, common on blackspot resistant knockout roses

Fungal Leaf Spots-Cherry Shot Hole

Cedar-Apple Rust on Juniper

Cedar-Quince and Cedar-Hawthorn Rust on Crabapple

Pear Trellis Rust

Washington State Univ.

Pnwhandbooks.org

Boxwood Blight

Volutella Blight and Macrophoma Leaf Spot

Douglas Fir Needle cast

Rhododendron diseases

• Phytophthora blight and root rot

• Management:

– Remove infected plants

– Change drainage or soil conditions

– Chemical treatments are not curative, temporary fix, and are expensive

Phytophthora root and crown rot

Rhododendron diseases

• Botryosphaeria canker

Rhododendron diseases

• Botryosphaeriaon rhododendron

• Management

– Prune out infected stems and twigs below canker symptoms

Fungal Canker DiseasesFilbert blight

Cytospora on spruce

Thyronectria Canker on Honey Locust

Verticillium Wilt

Photo: J. Hartman, U. Kentucky

Fungal Wilt Diseases

Dutch Elm disease

Dutch Elm Disease

Fungal Root Rots Armellaria

Armellaria rhizomorphs

Joseph O'Brien, USDA Forest Service,

Bugwood.org

Armellaria root rot

Joseph O'Brien, USDA Forest

Service, Bugwood.org

Ganoderma Root Rot

Fungal Root RotsJack o’lantern mushrooms

Fungal Wood DecayHypoxylon cankers on oak

Clematis Stem blight

Miscanthus leaf spots/blight

Botrytis blight on flowers

Day Lily Leaf Streak

Downy Mildew on Rudbeckia

Impatiens Downy Mildew

Alternaria Leaf Spot on Sunflower

Cladosporium on Peony

BacteriaLeaf spots on Zinnia

Bacterial/fungal leaf spots on zinnia

BacteriaCrown Gall on Rose

Photo by Bob Alde

Phomopsis Fungal Twig Gall on Forsythia

BacteriaFire Blight on Crabapple

Fire Blight

Spur Die Back and Canker caused by Fire Blight

Photo by William M. Ciesla

Bacterial Ooze caused by Fire Blight

Photo by John Hartman, U of Ky

Bacterial Streaming from Fire Blight Infected Twig Tissue

Photo by Paul Bachi, U of Ky

Bacterial Leaf Scorch on Oak

Bacterial leaf scorch on oak

• Caused by a bacterium

• Thins the canopy

• Causes dieback• Starts from the lower

branches and interior of the canopy

• Has killed many street trees

NematodesRoot Knot Nematode Galls

NematodesFoliar Nematode Symptoms

Virus Symptoms on Dahlia

VirusesMosaic on Gerbera Daisy

VirusesImpatiens Necrotic Ring Spot Virus

Virus on rose

Rose Rosette Virus in Multiflora Rose

• Eriophyid mites can be

seen with a 20x hand lens

with practice and patience

• Mites are found on tender

new growth on buds and

between stems and leaf

petioles

• Most infections occur in

spring (Apr‐June)

• Mites can be spread long

distances on wind currents

Rose Rosette eriophyid mite

Phyllocoptes fructiphilus

ars.org

Rose Rosette Symptoms

Rose Rosette Symptoms

Rose Rosette Virus

Hosta Virus X

Phytoplasmas - Elm Yellows

Photo from Gary Moorman, Penn State

Dodder

Dodder

Mistletoe

Photo from MK Malinoski

Collecting a Sample

• Collect leaves that show various stages of symptom development.

• Border between healthy and diseased tissue.

• A sample can consist of leaves from more than one plant of the same species.

• Take pictures of symptoms and environment.

Slide from NPDN

Packaging a sample

• Place sample on a paper towel. Do not wet the towel.

• Double bag and seal the sample in zip lock bags.

• If shipping, use a crush proof box with seams sealed completely with tape.

• Be sure to include the sample submission form.

Slide from NPDN

University of Maryland Plant Diagnostic Laboratory

Dr. Karen Rane

Dept. of Entomology

University of Maryland

4112 Plant Sciences Building

College Park, MD 20742-4454

301-405-1611

rane@umd.edu

http://www.plantclinic.umd.edu