Urban TreesDiagnosis and Disorders

Karen Carter

Virginia Cooperative Extension

Henrico County

Disease Causes

Biotic Agents Living; infectious Fungi, bacteria, viruses, nematodes

Abiotic Agents Non-living, noninfectious Nutrient deficiencies, water stress,

temperature stress, chemical misapplication

Symptoms and Signs Symptoms are physical expression of

disease by plants Blights Cankers Die-back Galls Mosaic/Mottle/Ring spot Rots Spots Wilts

Symptoms and Signs

Signs are the visible presence of pathogens. Mycelia Ooze/Flux Pycnidia

Powdery Mildew

Slime Flux

Conditions for Disease

Predisposing Factors (Stress)

Improper temperature Excess soil moisture Drought Improper nutrition Improper light Improper humidity Wet foliage Mechanical damage

Diagnosis is not easy!

A given symptom can have many different causes.

Requires knowledge of the plant, its history, and its environment.

Requires good detective work; look for clues, ask the right questions.

Diagnosing Tree Problems

Accurately identify the plant. Look for a pattern or abnormality. Carefully examine the site. Note the color, size, and thickness of

the foliage. Check the trunk and branches. Examine the roots and root collar.

Root Collar Excavation

References

Plant Disease Clinic

• Diagnostic services for VCE

• Plant Disease Fact Sheets on-line

www.ext.vt.edu/pubs/plantdiseasefs/index.html

Submit Sample to Extension Office

Submitting a sample Collect leaves

(or other plant parts) that show various stages of symptom development.

Take pictures of symptoms and environment.

Packaging a sample Place sample on a

paper towel. Do not wet the towel.

Double bag and seal the sample in zip-able bags.

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

Sampling reminders

The accuracy of a disease diagnosis can only be as good as the sample and information provided.

Sample must be representative of symptoms and severity in the field and must contain the right material.

Call an Arborist

Disease and Pest Control

Hopefully, many problems can be avoided by:

• Using less susceptible species.• Planting in the right location.• Proper planting and after care.

Urban Trees Diseases

Developed by:Mila Pearce, IPM Diagnostic Lab, Griffin

Gary Peiffer, County Extension Agent, DeKalb In Cooperation with

The University of GeorgiaCooperative Extension Service

Urban Forestry Issue Team

Powdery Mildew – Fungal disease of leaves of most broad-leaved trees and shrubs causing little lasting damage except possible dwarfing or distortion on heavily infected leaves.

Powdery mildews: Found world wide Over 7000 species Gymnosperms are not infected Obligate parasites

Powdery MildewFavorable conditions:*Dry, warm days*Cool nights*Water inhibits germination, but humidity does not

Powdery Mildew ControlSeldom warranted because damage is usually slight. Destroy fallen leaves, increase sunlight, and improve air flow. Surface applications of certain fungicides can be used.

Anthracnose Fungal disease of a wide variety of broad-leaved trees causing symptoms that vary from small necrotic leaf spots to blight of leaves.

AnthracnosePrimary causal agents:

ColletotrichumKabetiellaPhyllostictaGloeosporiumDisculamany more…..

* Small necrotic spots* Irregular lesions along leaf margins* Premature defoliation

Anthracnose Symptomology

AnthracnoseFavorable conditions:

* Warm, wet weather* High humidity* Poor air circulation

Discula on Dogwood

Dieback caused by Discula Discula petal blight

Discula v. Spot Anthracnose

Purple Eye Target Spot on maple caused by Phyllosticta.

Bacterial Leaf Scorch

Bacterial Leaf ScorchCausal agent : Xylella fastidiosa. Infection through xylem feeding insects such as sharpshooters and treehoppers.

Bacterial Leaf ScorchSymptomology:Dieback and browning due to water stressScorching of leaf margins

Control:Maintain plant vigorPrune infected branchesNo chemicals available

Bacterial Leaf ScorchFinal stages of decline

Symptomology:Sudden blighting, death of bloomsBacterial ooze may be visibleBlighted leaves stay attachedForms shepard’s crook

Fire blight

Fire BlightCausal agent: Erwinia amylovoraFavorable conditions:Infection in spring when there is abundantmoisture and temperatures 65-86 F

Fire BlightControl: Plant tolerant varieties Prune infected branches Disinfect pruning tools Maintain plant vigor Control insect vectors

Cankers and Galls on trunks/branches - Seiridium Canker

Distinct, sunken lesions which lead todieback and death

Flattened cankers are associated with bleeding and resin.

Seiridium CankerSpores are dispersed throughoutthe summer, but infection periodsare unknown

Hosts include :Oriental arborvitaeBaldcypressArizona cypressItalian cypressLeyland cypressJunipers

Dieback is from the inside out

Seiridium CankerControl:Remove cankers in winterDo not prune in May or JuneIncrease plant healthNo chemicals available

NECTRIA CANKERS:

Are multi-layered and become weak points on branches and trunks.

Canker wounds are often points where branches or trunks break off in ice and/or wind.

Nectria Cankers

Hosts:OakMapleYellow popularCherriesDogwoodsElmsHickoryRedbuds

Botryosphaeria Cankeron Leyland Cypress

Other hosts include:Hickory HollyLindens MaplesOak Pecan

Control:Prune branches six to eight inchesbelow the canker wound.

Wood Decay FungiGanodermaInonotusHypoxylonHispidus CankerIrpex Canker

Hypoxylon canker is most prevalent in weakened or stressed Hardwoods:OakBeechHickoryMaplesTupelo

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 CankerPrimarily found on oaks

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

Vascular WiltsDiseases that interfere with the uptake and flow of water and nutrients.

Dutch Elm Disease Yellowing, flagging and branch dieback

Staining under bark

Dutch Elm DiseaseControl: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.

Wetwood and SlimefluxCaused by bacteria.Hosts:OaksPopularElms

Other symptoms:fermentation smell, swarming insects

Wetwood

Bacterial infection initiated through root and/or trunk wounds. Oozing occurs when bacterial pressure builds up in the trunk. Weakens trees but does not directly cause their death.

Control:Cosmetic only.Use 10-20% solution of bleachTo clean the bark surface.Do not drill to insert drain tubesbecause it spreads infection.

Insects of Trees

Developed By:Jule-Lynne Macie, Rockdale Extension Agent

In Cooperation withThe University of Georgia

Cooperative Extension ServiceUrban Forestry Issue Team

Insects are often blamed for other’s damage:

Sapsuckers Herbicide damage Lightning Too much or not

enough water Squirrels String trimmer

Beaver Deer

Secondary pests Ants Bees Long horned beetles Termites

When looking at damage:

Think mouthparts Holes – chewing Wilting, yellowing – piercing sucking Speckling – rasping sucking

The Real Boring Insects

Chewing mouthparts, so think ‘holes’

Bark Beetles

Three beetle species: Southern Pine Beetle, Ips Engraver Beetle Black Turpentine Beetle

Larvae feed under bark Needles turn yellow from tips

back

Beetle Size Comparisons

Southern Pine Beetle is smallest (left).

Black Turpentine Beetle is largest (right).

Ips Engraver Beetle is in-between.

Beetle size compared to grain of rice.

Under the Bark

Beetles attack stressed native pine trees

Second generation beetles attack surrounding trees

Blue stain fungus Galleries

Pitch Tubes

A sign of attack – tree’s defense mechanism.

Popcorn-like in appearance.

Beetles may be ‘stuck’ in pitch.

Control for Homeowners

Sanitation! Homeowners do

not have equipment to spray preventatively

Asian Ambrosia Beetles

Attack smooth bark trees in early spring when leaves expanding

Bore deep into heartwood Toothpicks No good chemical control Tree removal – but no

need to hurry.

Various Wood Boring Beetles Beetles and caterpillar

species Common examples:

Poplar Borer Ash and Lilac Borer Bronze Birch Borer

Female lays eggs on trunk and larva bore under bark

Trees weakened by stress most likely to be attacked.

Manage thru tree selection and maintaining tree health.

Caterpillars

Chewing mouthparts so think ‘holes’

Bagworms

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!

Eastern Tent Caterpillars

Spring pest Tents in interior of tree Prefer fruit trees Capable of total

defoliation Will not kill a tree

(usually)

Orange Striped Oakworm

Fall Webworms

Large flimsy nests that cover tips of branches.

Nests grow larger and larger until entire branches are covered

Gypsy Moth

Late instar gypsy moth caterpillar on leaf (note body hairs and rows of red and blue dot pairs on back)

Be on the lookout for this pest

Sawflies

Feed in groups A type of wasp Caterpillar-like

larvae, but have more legs.

Bt is not an effective control.

Defense mechanism

Beetles

Both adult and larvae can cause damage

Elm Leaf Beetles

Japanese Beetles

Sucking Insects

Needle-like mouth so think yellowing, wilting and deformity

Aphids

Clients will often say their problem is ants on their plants

Wooly Alder Aphids

Piercing sucking Suck plant sap Honeydew Sooty mold 30 generations a year Live birth Wings at times

Scales – Soft, Armored, Pit, Oystershell, etc.

Piercing sucking Crawlers Waxy covering Systemic

insecticides Sooty mold

Other Insects

Miscellaneous damage, but is it really necessary to control?

Galls                          

Cicadas