Urban Trees Diagnosis and Disorders Karen Carter Virginia Cooperative Extension Henrico County
Jun 09, 2015
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