What’s Wrong With Your Plants and Why?

Tony GloverRegional Extension

Agent

Diagnosis Can Be Tricky Without All The Facts

Abiotic vs. Biotic Problems

• Abiotic – non-living agent (non-infectious).

Extreme temperatures Excess or deficient

water, light or nutrients Soil compaction, soil

grade changes Damage from cultural

practices: herbicides, fertilizers, pruning, mulching

Abiotic vs. Biotic Problems

• Biotic – living agent (infectious).

Pathogens - parasitic microorganisms that cause disease (fungi, bacteria, viruses, phytoplasma)

Pests – insects, mites, nematodes or mammals feeding on or damaging plants.

Abiotic vs. Biotic Problems

Symptom Progression• Biotic disease –

symptoms progress and nearby plants become infected.

• Abiotic disease – generally a lack of symptom progression. Does not spread.

Exception – nutritional deficiency symptoms progress slowly.

Abiotic disease – Herbicide Injury

What’s Wrong?

Biotic or Abiotic

Steps in Problem Diagnosis

Know the Plant Inspect the Site and Look for Patterns Look for Symptoms or Signs Examine cultural practices and

weather conditions Identify Potential Causes Consult Resources and Reach

Diagnosis

Steps in Problem Diagnosis

Know the Plant• Identify the species and cultivar affected• Know what problems commonly affect

the species. For example: Red Maple – Phyllosticta Leaf Spot, gloomy

scale Flowering Dogwood – Powdery Mildew, spot

anthracnose

Steps in Problem Diagnosis

Know the Plant• What’s normal for specific plant?

Fall Needle Drop on White Pine

Steps in Problem Diagnosis

Know the Plant• Look at the Whole Plant (foliage, stems,

branches, leaves, and roots)• Note the color, size, and thickness of the

foliage• Check the trunk and branches• Examine the Roots

Check the Trunk and Branches

Look for wounds, cankers, exit holes and other clues

Pitch Tubes on Bark, Southern Pine Beetle

Check the Trunk and Branches

Sapsucker damage to sugar maple

Don’t mistake sapsucker damage for borer exit holes

Check the Trunk and Branches But…

Girdling Roots

Girdling Injury

Planted too deep

Deep Planting or Covered Later

Check for flare at base of trunk

Girdling Roots Girdling roots are a

common problem with trees that are planted too deep

Too Much Mulch Over The Root Ball

Problems caused by too much mulch• Keeps trunk tissue wet• Can increase rodent

damage• Mulch can intercept

rain and irrigation• Can keep poorly

drained soils too wet• Can encourage surface

roots• Can encourage

development of stem girdling roots

Planted too deepOld root system has died

Steps in Problem DiagnosisInspect the Site and Look For Patterns

• Determine prevalence of problem. Large area, all plants – generally abiotic. Scattered, localized – generally biotic.

• Check for distribution of symptoms. Uniform – generally abiotic. Random – generally biotic.

• Are the symptoms/patterns related to geography? (soil, low spot, etc)

• Is the damage limited to one type of plant? Multiple plant species - often abiotic One species – often biotic

Observation of Field PatternsAbiotic Problem

Symptoms distributed in a large area. Damage pattern is uniform.

Gas leak from building

Observation of PatternsRandom vs. Uniform

Leaf Spot (Fungal) Marginal Leaf Scorch

Observation of Field PatternsRandom vs. Uniform

Boxwood Phytophthora Root Rot Oak Nutrient Deficiency

Uniform StripesRandom Patches

Observation of Field PatternsRandom vs. Uniform

Bermuda spring dead spot Fertilizer application problems

Steps in Problem Diagnosis

Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and

Weather Conditions Identify Potential Causes Consult Resources and Reach

Diagnosis

Look for Symptoms and/or Signs

Symptoms - plant reactions or alterations of a plant’s appearance due to a disease or disorder.

Signs - actual presence of the pathogen, it’s parts or by-products seen on a diseased host plant.

Symptoms

Signs

Steps in Problem Diagnosis

Know the Plant Inspect the Site and Look for Patterns Look for Symptoms and/or Signs Examine Cultural Practices and

Weather Conditions Identify Potential Causes Consult Resources and Reach

Diagnosis

Steps in Problem Diagnosis

Examine Cultural Practices and Weather Conditions• Ask questions - Collect as much background

information as possible• When was the problem noticed?• Was the damage sudden or gradual?• Has the problem spread?• How old are affected plants?• What cultural practices have been performed

recently? Herbicide Sprays?

Hail Damage

Steps in Problem Diagnosis

Identify Potential Causes Consult Resources and Reach

Diagnosis Get Laboratory Assistance

• Take samples (plant, soil)• Don’t forget pictures

Most Common Diseases of 2009Ornamentals

• Phytophthora Root and Crown Rot • Boxwood, Juniper, Hydangea, Leyland Cypress, Pansy, Petunia,

• Fungal Leaf Spots (Oak Leaf Blister, Anthracnose, and other leaf spots)

• Armillaria Root Rot• Oakleaf Hydrangea, Cotoneaster

• Pythium Root Rot • Pansy and other flowers

• Powdery Mildew • Dogwood, Crape Myrtle, Rose

• Botryosphaeria Canker /Dieback • Leyland Cypress, Japanese Maple, Cleyera

• Bacterial Leaf Spots• Basil, Begonia, Oakleaf Hydrangea, English Ivy

• Azalea Leaf Gall• Sooty Mold

• Various Trees and Shrubs (Hackberry Woolly Aphid)

Diseases Caused by Phytophthora

Some of the most economically important and damaging diseases on woody plants in the Southeast, USA, and worldwide

The name Phytophthora derives from Greek and literally means “plant destroyer.”

Cause problems annually Notorious Phytophthora diseases include

rhododendron root rot, sudden oak death, and potato late blight.

Particularly serious in or following “wet” years Diseases often are associated with wet or

saturated soils

Phytophthora 101

Phytophthora species resemble fungi but are not.

They are most closely related to aquatic organisms, such as brown algae and diatoms.

Phytophthora organisms are often referred to as ‘water molds’ because they do need water to complete their life cycle.

This group of organisms produces swimming spores .

Disease Cycle: Phytophthora Root Rot

Some Trees and Shrubs Attacked

Abies – fir Acer – maple Arbutus – madrone Betula – birch Buxus – boxwood Camellia – C. japonica Castanea – chestnut Cedrus – cedar Cercis – redbud Chamaecyparis - false

cypress Citrus - orange, lemon, etc. Cornus – dogwood

Cryptomeria -Japanese cedar

Cupressus - cypress Elaeagnus Eucalyptus Fagus – beech Ficus - fig Forsythia Ilex - holly Juglans—walnut Juniperus –juniper Kalmia – laurel Malus - apple

More Trees & Shrubs Attacked...

Pieris – andromeda Pinus – pine Platanus – sycamore Prunus - cherry, plum, etc. Pseudotsuga - Douglas fir Pyrus - pear Quercus – oak Rhododendron -

rhododendron, azalea Robinia – locust Rosa - rose

Rubus - raspberry Syringa - lilac Taxus - yew Thuja - arborvitae Tsuga - hemlock Vaccinium - blueberry Viburnum -arrowwood Ulmus – elm

Phytophthora as Pathogens of Woody Plants

They can attack all parts of the plant Blight & dieback on shoots & foliage

—uncommon Cankers on stems & trunk —e.g.,

“bleeding” cankers – occasionally Root & crown rots — most common

Symptoms—Above Ground Appear after roots are diseased Chlorosis & yellowing of the foliage

• very slight at first, then becoming obvious Stunted growth Overall wilting & decline Cankers - orange/red/brown discoloration

• on stems and trunk• distinct margin between healthy & diseased

tissues Plant death

Phytophthora Foliage Blight

Trunk and Stem Cankers “bleeding” cankers - maple

Trunk and Stem Cankers “bleeding” cankers - Oak

outer bark inner bark

Photo: Bruce Moltzen, Missouri Department of Conservation

Symptoms—Below Ground

Must expose roots for examination• this usually requires digging! • need to know what healthy roots look like!

Reduced root volume/lack of feeder roots Roots discolored - red, brown, dark brown

• healthy roots are white or off-white Cortex sloughing/root rot Cankers on root crown

• may move up stem above ground

Boxwood - Cortex sloughing/root rot

Phytophthora Root Rot on Boxwood

Phytophthora Root Rot on Shore Juniper

Field Diagnosis

Above-ground symptoms alone usually are not diagnostic—merely indicate vascular dysfunction

Therefore, look below ground at roots & crown

Together, these may be diagnostic Other pathogens also can cause root rot

• Armillaria, Fusarium, Sclerotium, Thielaviopsis, etc.

• and sometimes Pythium spp., especially on boxwood

Fungal Leaf Spot Diseases

Typically have tan to gray centers surrounded by a darker border

Fungal fruiting structures (pycnidia, spores, etc.) can be seen within the leaf spot

Defoliation is common Fungi survive on fallen leaves Prolonged leaf wetness, high humidity and poor

air circulation increase disease development Spores are spread by wind and water-splashing,

but can also be spread by insects, on clothes, tools, and hands

Japanese MaplePhyllosticta Leaf Spot

Defoliation due to Entomosporium leaf spot disease - Indian Hawthorn

Less water stays on this protected area

Oak Leaf Blister

Common fungal disease on oaks, especially red oaks (s. red and water oak)

Disease favored by cool, wet springs

Symptoms appear in late spring as yellow, blister like, circular, raised areas

Oak Leaf Blister

Spots become dull brown with age

As leaves mature, become resistant to infection

Affects appearance not tree health

Fungicides not needed, but one application of chlorothalonil or mancozeb before budbreak will control disease

Cercospora Leaf Spot – Crape Myrtle

Cercospora Leaf Spot

Cercospora Leaf Spot - Dogwood

Boston Ivy Leaf Spot

Armillaria Root Rot

Armillaria Root Rot – Oakleaf Hydrangea

Armillaria Root Rot - Oakleaf Hydrangea

Armillaria Root Rot -Oak

Armillaria Root Rot - Rose

White fungal growth under bark

Drainage? Irrigation? Death

by watering hose? No fungicides for

control Resistant plants

best replacement option

Bacterial Leaf Spots

Plant wetness, high humidity and warmer temperatures favor disease development

Bacterial cells spread by water splashing, tools, hands, or insects

No Fruiting structures in spots

Many controlled with copper fungicides (Kocide)

Angular leaf spots running along veins

Oak Leaf Hydrangea

Bacterial Leaf Spots

English Ivy Hydrangea

‘water soaked spots’

Sooty Mold Common name for group

of black-colored fungi that grow on honeydew on plants and other surfaces

Fungal growth gives appearance of being covered with a layer of soot

Honeydew produced by aphids, mealybugs, soft scales, whiteflies

Control sooty molds by controlling the honeydew producing insect. Drenches with Merit or Safari for hackberry aphids (early spring)

Sooty mold on crape myrtle

Asian Woolly Hackberry Aphid

Multicolored Asian lady beetle pupa

Azalea Leaf Gall

Occurs in cool, moist springs

Spores for next year’s infection are released when leaf galls turn white

Prune infected leaves

Camellia Leaf Gall

Camellia leaf gall early symptoms and lastyear’s infected leaves

Spores for next year’s infection are released when backside of leaves turnwhite

Leaf Gall Control Remove galls and destroy before they turn white

with spores Disease most severe when foliage becomes wet

during leaf expansion in spring. • Avoid planting in heavy shade • Avoid wetting foliage in spring

If the disease was severe in previous years and galls were too numerous to pick, apply a fungicide before new leaves and flowers emerge.

Applications can stop when leaves become full size Bayleton. Apply first spray as new leaves and

flowers appear. Repeat 2-3 times at 10-day intervals.

Powdery Mildew Common disease on dogwood

and other plants Looks like baby powder Use Resistant Cultivars:

• Cherokee Brave, Karen’s Appl. Blush, Kay’s Appl. Mist, Jean’s Appl. Snow

Start sprays at first sign of disease (early May)

Fungicides:• Heritage • Spectricide Immunox• Fertilome Systemic Fungicide• Fertilome Halt Systemic

Fungicide

Too late for fungicides

Spot Anthracnose

Small reddish spots on bracts and leaves, trees in sun

Rake leaves in fall Heritage, Daconil,

Mancozeb, Halt, Immunox

Spray before budbreak, after bract fall, and one month later, and September after new flower buds form

Dogwood Anthracnose Different disease than

spot anthracnose Spots with reddish or

purple borders Spots enlarge over

time Leaf, twig blights,

cankers, can kill tree Blighted leaves

remain attached through winter

Resistant Cultivar ‘Appalachian Spring’

Hydrangea – Leaf Spot Several fungi cause leaf spots

on hydrangea – Cercospora, Corynespora, Colletotrichum

Often in combination with powdery mildew

Adequate plant spacing for good air circulation

Avoid watering late in the day Remove fallen leaves Apply fungicide at first sign of

disease:• Heritage, Daconil*, Immunox

Mancozeb*, Fertilome Systemic Fungicide

• * Poor control of powdery mildew, but good leaf spot control

• Ultra-fine Spray Oil

Leyland Cypress Problems

Botryosphaeria Canker

J. Woodward - UGA

Botryosphaeria Canker

UGAJ. L. Williams-Woodward - UGA

Control of Canker Diseases Difficult to control once infection has occurred Prevent canker diseases by proper

establishment and care:• Plant in well drained soils• adequate plant spacing• Irrigate plants to prevent drought stress, mulch

plants• Remove branches with cankers. Trace the dead

wood back to the base of the canker and prune at bud or branch fork. Prune 4-6 inches below canker.

• Sterilize pruning tools frequently• Avoid canker susceptible plants

Fungicides are of little value

Thank You