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Trees Pests and D iseases. Developed by: Janet Anastasi , Master Gardener Volunteer Frank Reilly , Advanced Master Gardener & Tree Steward Leslie Paulson , Advanced Master Gardener & Tree Steward With input from Page Thacker , Unit Coordinator & Extension Agent And the

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trees pests and d iseases

Trees Pests and Diseases

Developed by:

Janet Anastasi, Master Gardener Volunteer

Frank Reilly, Advanced Master Gardener & Tree Steward

Leslie Paulson, Advanced Master Gardener & Tree Steward

With input from

Page Thacker, Unit Coordinator & Extension Agent

And the

Prince William County Tree Team

trees pests and d iseases environmental and other non living factors

Trees Pests and DiseasesEnvironmental and other Non-Living Factors

Developed by:

Janet Anastasi, Master Gardener Volunteer

in cooperation with:

Chuck Hoysa, Past Extension Agent and Soil & Water Conservation District Educator

Joe Murray, Consulting Arborist and Assistant Professor of Biology Arboriculture Program Director, Blue Ridge Community College

Mila Pearce, IPM Diagnostic Lab, &

Gary Peiffer, County Extension Agent,

The University of Georgia

Cooperative Extension

why plant a tree
Why Plant a Tree?
  • Provide shade
  • Provide aesthetics in the landscape
  • Improve air quality
  • Reduce storm-water runoff and improve water quality
  • Create wildlife habitat
  • Reduce noise levels
  • Provide screening and privacy
types of construction damage

Environmental Changes

  • Soil compaction
  • Excessive thinning
  • Moisture stress
  • Soil fill
  • Soil cuts
soil compaction
Soil Compaction


  • Running of heavy equipment over root zones
  • Piling of debris on top of tree roots
  • Parking under a tree
soil contamination
Soil Contamination

Prevent soil contamination that can damage or kill trees!

  • Watch out for fuel leaks.
  • Do not allow on-site paint dumping.
  • Plan for cement or mortar wash out areas.

Is this a good home building site?

site factors
Site Factors

Environmental Conditions

  • Light patterns
  • Temperature extremes
  • Precipitation
  • Wind patterns
  • Air quality
site factors1
Site Factors

Soil characteristics

  • Texture
  • Compaction
  • Moisture & drainage
  • Fertility and pH
  • Temperature
  • Contamination
  • Salt
non living factors
Non-Living Factors
  • Nutrient Deficiency
  • Water Stress
  • Temperature Stress
  • Other
what is the right tree
What is the Right Tree?
  • Growth factors
  • Soil requirements
  • Other Environmental requirements
  • Maintenance requirements
right tree
Right Tree

Other environmental factors

  • Hardiness zone
  • Wind and storm damage
  • Light requirements
  • Pollution tolerance
  • Insect and disease tolerance
tree care after construction
Tree Care after Construction
  • Aerate or use other soil alteration methods to re-introduce oxygen and reduce compaction.
  • Water deeply – to encourage new root development and reduce tree stress.
  • Inspect frequently – look for visible signs of insect or disease attack.
  • Mulch – them well but correctly!
  • Fertilize – in a year or two after they have recovered from construction stress.
non living and cultural factors
Non-living and Cultural Factors
  • Can be tricky to diagnose
  • Good to know what is ‘normal’
  • Knowledge of past weather conditions
  • Knowledge of past cultural practices
  • Often referred to as disorders
  • Yellow leaves with green veins
  • Indicates nutrient deficiency
  • Can be a fertilizer or pH problem
  • Can affect all trees -
  • pin oak - dogwood
leaf scorch
Leaf Scorch
  • Lack of water
  • Common on newly planted trees
  • Can occur on established trees during drought
  • Common on trees with restricted roots
winter damage
Winter Damage
  • Timing is key
  • Late winter, early spring, before new growth emerges
  • Most common on broad leaf evergreens
  • Can show up as leaf scorch, dead branches
herbicide damage
Herbicide Damage
  • Knowledge of use
  • Distorted growth, especially at growing points
  • Most susceptible in spring as new growth emerges
  • Damage can be widespread
needle shedding
Needle Shedding
  • Common on pines, especially white pine
  • Also occurs on other evergreens
  • Knowledge of plant is helpful
  • Look at other plants in neighborhood
trees d iseases

Trees Diseases

Developed by:

Frank Reilly, Advanced Master Gardener Volunteer

in cooperation with:

Chuck Hoysa, Past Extension Agent and Soil & Water Conservation District Educator

Joe Murray, Consulting Arborist and Assistant Professor of Biology Arboriculture Program Director, Blue Ridge Community College

Mila Pearce, IPM Diagnostic Lab, &

Gary Peiffer, County Extension Agent,

The University of Georgia

Cooperative Extension

conditions necessary for plant disease
Conditions Necessary for Plant Disease


Susceptible Host

Telephone call to Cooperative Extension!

Favorable Environment

take home message
Take Home Message
  • Right Plant Right Place
  • If you paid attention to the rest of these classes you can ignore most of the rest of this talk.
  • Accurately ID the plant – THE MOST important step!
  • Look for patterns of abnormalities
  • Examine the site
  • Look at the foliage
  • Look at the trunk and branches
  • Look at the roots and root collar

Symptoms vs. signs

  • Symptoms - expressions of disease initiation that differentiate them from healthy plants nearby
  • Signs - vegetative or fruiting (reproductive) structures of the organism that is causing the disease
disease symptoms
Disease Symptoms
  • Spots - circular or irregular lesions on leaves, flowers, and stems
  • Blights - sudden death of leaves, flowers, and twigs
  • Galls - abnormal growths or swelling
  • Cankers - dead places on bark and stems
  • Rots - general decomposition of tissue
insect damage leslie will talk about this
Insect DamageLeslie will talk about this
  • Some insect damage can look like disease
  • Sooty mold - grows on honeydew
  • Scales, mealybugs, mites, adelgids, borers can all cause damage that looks like disease
top 10 diseases

Top 10 Diseases

You are “likely” to encounter.


Powdery mildews:

*Found world wide

*Over 7000 species

*Gymnosperms are not infected

*Obligate parasites

Powdery mildews:

Found world wide

Over 7000 species

Gymnosperms are not infected

Obligate parasites

Favorable conditions:

*Dry, warm days

*Cool nights

*Water inhibits germination,

but humidity does not


Anthracnose: Fungal disease of a wide

variety of broad-leaved trees causing symptoms

that vary from small necrotic leaf spots to

blight of leaves.


Primary causal agents:






many more…..


Discula petal blight

Dieback caused by Discula


Control:Anthracnose on some species is not warranted because of location or

the disease presents no long term damage. Maintain tree vigor with proper watering, fertilization, good drainage, etc.Valuable shade trees may be pruned to reduce severity and increase life span of the tree.


Septoria leaf spot

- circular spots formed when a fungus attacks at bud break. Control should therefore be attempted at that time. Septoria species attack a wide variety of trees.


Fire blight - common to several Prunus species greatest damage on apples, crabapples and pears



Sudden blighting, death of blooms

Bacterial ooze may be visible

Blighted leaves stay attached

Forms shepard’s crook



Plant tolerant varieties

Prune infected branches

Disinfect pruning tools

Maintain plant vigor

Control insect vectors

Sprayed on antibiotics are also recommended but they are very costly and the coverage and timing are the keys to any success.


Cankers and Galls on trunks/branches - Seiridium Canker

Distinct, sunken lesions which lead to

dieback and death


Spores are dispersed throughout

the summer, but infection periods

are unknown

Dieback is from the inside out

Hosts include :

Oriental arborvitae


Arizona cypress

Italian cypress

Leyland cypress



Flattened cankers are associated with bleeding and resin.


Remove cankers in winter

Do not prune in May or June

Increase plant health

No chemicals available


Phomopsis Tip Blight –

Disease of conifers causing

needle cast, dieback, and

death of highly susceptible




Fungicides can be effective if

applied according to label directions.

Pruning branches will limit inoculum



Black Knot

Common gall on cherries,

plums, and peaches.

Symptoms include dieback of branches, thin

crowns, and gnarly black galls on trunk

or branches.

Control: Prune branch galls six to eight inches

below infection. It is impractical to remove trunk



Wetwood and Slimeflux

Caused by bacteria.





Other symptoms:

fermentation smell, swarming insects


Wetwood or slime flux

  • bacterial infection
  • initiated through root and/or trunk wounds.
  • Oozing occurs when bacterial
  • pressure builds up
  • Trunk and bark staining usually results.
  • weakens trees but does not directly cause their death.
  • Control:
  • Cosmetic only.
  • Use 10-20% bleach solution
  • clean the bark surface.
  • Do not drill to insert drain tubes
  • That spreads infection.

Wood DecayFungi




Hispidus Canker

Irpex Canker



Slighty sunken irregular areas on bark

Canker becomes blistered with clusters of perithecia

immersed in stromata causing the tree bark to exfoliate.

Colors vary from black, gray to tan.


Hypoxylon canker is most prevalent in

situations of weakened or stressed








Control measures include pruning out branch cankers, surgically removing small trunk cankers, fertilizing and watering to improve tree vigor. These controls can slow disease spread but do not often totally eliminate it!


Hispidus Canker

Entry point for this fungus is usually through old branch stubs or wounds. Causes a soft, white heart rot.


Hispidus Canker

Primarily found on oak species

Once trunk decay fungi are actively growing, there is no control. Improve tree vigor to add to its lifespan!


Vascular Wilts

Diseases that interfere with the

uptake and flow of water

and nutrients.


Verticillium Wilt

Sample Hosts:

Maple, Ash, Elms, Magnolia, Redbud

Tulip Poplar

  • Symptoms include:
  • curling,
  • drying,
  • interveinal chlorosis or
  • reddening,
  • defoliation,
  • wilting,
  • dieback and death.
  • Infection occurs on stressed trees
  • initiated through the roots and wounds.

Dutch Elm Disease DED

Yellowing, flagging and

branch dieback

Staining under bark



Prune infected branches and monitor insect vectors (elm bark beetles).

Prevent root grafts through appropriate use of trenching methods.

Plant resistant varieties such as Chinese Elms and Zelkova Elms.


Annosum Root Rot





Symptoms include general

tree decline and wind-throw.

what next
What Next?
  • Most diseases we encounter are cosmetic
  • Sanitation - prune and rake
  • Remove problem trees
  • Plant appropriate or disease resistant trees
  • Spraying is often not an option
  • Get a positive ID before any treatment
  • Start with a good sample
what makes a good sample
What makes a good sample?
  • Distinct symptoms
  • Fresh sample
  • Whole section of branch or handful leaves
  • Junction of live and dead tissue
  • What plant is it!
what makes a bad sample
What makes a bad sample?
  • All dead tissue
  • Single leaf
  • Been on dashboard for a week
  • Damage occurred months ago
  • Don’t know what plant it is

Oak Leaf Blister (caused by a fungus) is more common during cool, wet springs. Leaves remain attached therefore little long term harm to tree.


Witches’ Broom caused by powdery mildew on Witchhazel but there are many causes such as diseases, insects, frost, drought, etc.


Witches’ Broom caused by

mites and powdery

mildew on Hackberry tree.


Cedar Apple Rust

Galls are abnormal growth responses

caused by fungi, insects, and bacteria


Mature gall

Actively sporulating



Alternate host leaf spot.

Most often seen on apples and


new diseases on the horizon sudden oak death sod phythophthora ramorum
NEW DISEASES ON THE HORIZONSudden Oak Death, SOD, Phythophthora ramorum
  • Phythophthora ramorum is a soil-borne fungus
  • accidentally shipped to the Eastern USA in nursery stock
  • shown to affect over 60 different ornamental plants.
  • damaged and/or killed many western tree species but
  • we do not know what it will do to eastern varieties, especially our oaks.

trees pests

Trees Pests

Developed by:

Leslie Paulson, Advanced Master Gardener Volunteer

in cooperation with:

Chuck Hoysa, Past Extension Agent and Soil & Water Conservation District Educator

Joe Murray, Consulting Arborist and Assistant Professor of Biology Arboriculture Program Director, Blue Ridge Community College

Mila Pearce, IPM Diagnostic Lab, &

Gary Peiffer & Jule-Lynne Macie, County Extension Agent,

The University of Georgia

Cooperative Extension

insect damage
Insect Damage
  • Some insect damage can look like disease
  • Sooty mold - grows on honeydew
  • Scales, mealybugs, mites, adelgids, borers can all cause damage that looks like disease
insects are often blamed for other s damage

Herbicide damage


Too much or not enough water

Squirrels, roof rats

String trimmer



Secondary pests



Long horned beetles


Insects are often blamed for other’s damage:
when looking at damage
When looking at damage:
  • Think mouthparts
    • Holes – chewing
    • Wilting, yellowing – piercing sucking
    • Speckling – rasping sucking
the real boring insects

The Real Boring Insects

Chewing mouthparts, so think ‘holes’

bark beetles
Bark Beetles
  • 3 different beetles – southern pine beetle, Ips engraver, Black turpentine
  • Needles turn yellow from tips back
  • Larvae feed under bark
under the bark
Under the Bark
  • Beetles attack stressed native pine trees
  • Second generation beetles attack surrounding trees
  • Blue stain fungus
  • Galleries
pitch tubes
Pitch Tubes
  • A sign of attack.
  • Beetles are sometimes ‘stuck’ in pitch
control for homeowners
Control for Homeowners
  • Sanitation!
  • Homeowners do not have equipment to spray preventatively
asian ambrosia beetles
Asian Ambrosia Beetles
  • Attack smooth bark trees in early spring when leaves expanding
  • Bore deep into heartwood
  • Need moist wood
  • Toothpicks
  • No good chemical control
  • Cut down
various wood boring beetles
Various Wood Boring Beetles
  • Attack various trees
  • Female lays eggs on trunk and larva bore under bark
  • E.g. Poplar Borer, Emerald Ash Borer, Lilac Borer, Bronze Birch Borer
emerald ash borer
Emerald Ash Borer
  • aggressive wood borer
  • Responsible for fire wood quarantine
  • “D”-shaped exit hole


Chewing mouthparts so think ‘holes’

  • Deciduous and evergreens
  • Insecticides only if early in season
  • Fall – move to ends of branch and pupate
  • Males fly to females
  • Lay eggs in bag
  • Prune and discard!
tent caterpillars
Tent Caterpillars
  • Spring pest
  • Tents in interior of tree
  • Prefer fruit trees
  • Pretty caterpillars
  • Capable of total defoliation
  • Will not kill a tree (usually)
orange striped oakworm
Orange Striped Oakworm
  • Fall Pest of Oaks
  • Caterpillars feed together
  • Begin life light green and turn black with stripes
fall webworms
Fall Webworms
  • fall webworm appears I late summer
  • nests grow until entire branches are covered
  • Seldom a danger to the tree
hickory horned devil
Hickory Horned Devil
  • Regal Moth
  • Largest Butterfly/moth north of Mexico


Both adult and larvae can cause damage

japanese beetles
Japanese Beetles
  • Turf pest
  • Adults difficult to control
  • Attack the grubs
sucking insects

Sucking Insects

Needle-like mouth so think yellowing, wilting and deformity

wooly alder aphids
Wooly Alder Aphids
  • Piercing sucking
  • Suck plant sap
  • Honeydew
  • Sooty mold
  • 30 generations a year
  • Live birth
  • Wings at times
aphids in general
Aphids in general
  • Clients will often say their problem is ants on their plants
  • Aphids like tender Nitrogen rich plant tips
  • Can cause mildew due to sweet honeydew
  • Natural controls (e.g. lady beetles)
scales soft armored pit oystershell etc
Scales – Soft, Armored, Pit, Oystershell, etc.
  • Piercing sucking
  • Crawlers – only control stage
  • Waxy covering
  • Systemic insecticides
  • Sooty mold
other insects

Other Insects

Miscellaneous damage, but is it really necessary to control?

leaf miners
Leaf Miners
  • Death to plant uncommon
  • Discolors or browns leaves
  • Hard to control – remove fallen leaves
  • Time applications exactly
  • Annual
  • Periodic
  • No long damage except to young saplings
  • Flagging
  • Different species (at least 3)
  • Different broods
  • Oak
  • Sycamore
  • Hawthorn
  • Azalea, rhododendron
the end

The End

Any Questions?