trees d iseases developed by: frank reilly, advanced master gardener volunteer in cooperation with:...
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Trees Diseases
Developed by:Frank Reilly, Advanced Master Gardener Volunteer
in cooperation with:Chuck Hoysa, Past Extension Agent and Soil & Water Conservation
District EducatorJoe Murray, Consulting Arborist and Assistant Professor of Biology
Arboriculture Program Director, Blue Ridge Community CollegeMila Pearce, IPM Diagnostic Lab, &
Gary Peiffer, County Extension Agent, The University of Georgia
Cooperative Extension
Non-Living Factors
Often cause disease-like symptoms
AND contribute to disease susceptibility
Janet will cover this aspect Nutrient Deficiency Water Stress Temperature Stress Other
Conditions Necessary for Plant DiseasePathogen Susceptible
Host
Favorable Environment
Telephone call to Cooperative
Extension!
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.
Diagnosis
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
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 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
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.
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.
Symptomology:Sudden blighting, death of bloomsBacterial ooze may be visibleBlighted leaves stay attachedForms shepard’s crook
Control: Plant tolerant varieties Prune infected branches Disinfect pruning tools Maintain plant vigor Control insect vectorsSprayed 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 todieback and death
Spores are dispersed throughoutthe summer, but infection periodsare unknown
Hosts include :Oriental arborvitaeBaldcypressArizona cypressItalian cypressLeyland cypressJunipers
Dieback is from the inside out
Flattened cankers are associated with bleeding and resin.
Control:
Remove cankers in winterDo not prune in May or JuneIncrease plant healthNo chemicals available
Phomopsis Tip Blight – Disease of conifers causing needle cast, dieback, and death of highly susceptibletrees.
Control:Fungicides can be effective if applied according to label directions. Pruning branches will limit inoculum build-up.
Black KnotCommon gall on cherries,plums, and peaches.
Symptoms include dieback of branches, thin crowns, and gnarly black galls on trunkor branches.
Control: Prune branch galls six to eight inchesbelow infection. It is impractical to remove trunkgalls.
Wetwood and SlimefluxCaused by bacteria.Hosts:OaksPopularElms
Other symptoms:fermentation smell, swarming insects
Wetwood or slime flux •bacterial infection •initiated through root and/or trunk wounds. •Oozing occurs when bacterialpressure 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.
Symptomolgy:Symptomolgy:Slighty sunken irregular areas on barkSlighty sunken irregular areas on barkCanker becomes blistered with clusters of perithecia Canker becomes blistered with clusters of perithecia
immersed in stromata causing the tree bark to exfoliate.immersed in stromata causing the tree bark to exfoliate.Colors vary from black, gray to tan.Colors vary from black, gray to tan.
Hypoxylon canker is most prevalent in situations of weakened or stressed hardwoods.
Hosts: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 Canker
Entry point for this fungus is usually through old branch stubs or wounds. Causes a soft, white heart rot.
Hispidus CankerPrimarily found on oak species
Once trunk decay fungi are actively growing, there is no control. Improve tree vigor to add to its lifespan!
Verticillium WiltSample Hosts:Maple, Ash, Elms, Magnolia, RedbudTulip 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.
Control: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.
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?
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? 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.
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.
www.suddenoakdeath.org
Trees Pests
Developed by:Leslie Paulson, Advanced Master Gardener Volunteer
in cooperation with:Chuck Hoysa, Past Extension Agent and Soil & Water Conservation
District EducatorJoe Murray, Consulting Arborist and Assistant Professor of Biology
Arboriculture Program Director, Blue Ridge Community CollegeMila Pearce, IPM Diagnostic Lab, &
Gary Peiffer & Jule-Lynne Macie, County Extension Agent, The University of Georgia
Cooperative Extension
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: Sapsuckers Herbicide damage Lightning Too much or not
enough water Squirrels, roof rats 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
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
Beetles attack stressed native pine trees
Second generation beetles attack surrounding trees
Blue stain fungus Galleries
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 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
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!
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
Fall Pest of Oaks Caterpillars feed
together Begin life light green
and turn black with stripes
Fall Webworms fall webworm
appears I late summer
nests grow until entire branches are covered
Seldom a danger to the tree
Wooly Alder Aphids Piercing sucking Suck plant sap Honeydew Sooty mold 30 generations a
year Live birth Wings at times
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.
Piercing sucking Crawlers – only
control stage Waxy covering Systemic
insecticides Sooty mold
Leaf Miners Death to plant uncommon
Discolors or browns leaves
Hard to control – remove fallen leaves
Time applications exactly
Cicadas Annual Periodic No long damage
except to young saplings
Flagging Different species (at
least 3) Different broods
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