Diagnosing Tree Problems

Linn/Benton Master Gardener Training

Rick Fletcher

OSU Extension Service

Tree Death in the City

Big Trees- Big Problem

Fungal Mat in Decayed Wood

The Real Culprit: Human Damage

Why Trees Die

• Complex interaction of biotic and abiotic factors……

– And a little bad luck.

What Kills Trees?

• Separately or in combination:– Insects– Animals– Diseases– Abiotic Factors

Environmental Setting

• Look to the underlying situation before making judgments about why a tree died.

• ALSO: Many insects and diseases occur on declining trees but are not the primary cause of death.

Conifer Diseases

• Root rots• Stem/branch cankers• Needle casts

Root Rots

Annosus root rot

Oak root rot

Laminated root rot

Cedar root rot

Diseased trees Healthy trees

Disease pathway tree

Nancy Boriack

ODF Photo

Short leaders

Oak Root Disease

• Caused by the fungus Armillaria ostoyae.

• The most common root disease in Oregon.

• Affects all conifers and hardwoods to some degree.

• Particularly damaging to stressed trees.

The honey mushroom

Annosus root disease

• Can attack many species of conifers.

• Especially bad on the Abies genus.

• Spreads rapidly from wounds, and cut stumps.

Dead Trees in Alsea- 2010

Laminated Root Rot Damage

Laminated Root Rot

• Attacks all conifers, but particularly bad on Douglas-fir.

• Trees attacked lose vigor and crown mass.

• Many times blow over before they die.

Cedar Root Rot

• Port-Orford Cedar Root Disease: Phytophthora lateralis.

• Avoid soil movement from infested to uninfested sites.

• Plant other species or disease-resistant cedar seedlings in infested areas.

E. Hansen photoPhotos from USFS Dorena Tree Improvement Center (html)Photos from USFS Dorena Tree Improvement Center (html)

Stem and Branch Cankers

• Gall rust• Dermia cankers• Phomopsis cankers• Grovesiella

Phomopsis canker

• Attacks stressed trees. Commonly Douglas-fir.

A New Threat- SOD

• Disease caused by Phytophora ramorum

• Wide host range• Disease has

spread from California north to Oregon.

Oregon Conifer Hosts of Concern

Douglas-fir and grand fir

Needle Casts and Rusts

• Swiss needle cast• Rhabdocline needle

cast.• Pine needle cast.• Poplar rust

Why the Yellow Trees?

Swiss Needle Cast

• Serious forest problem along the Oregon Coast.

• Only impacts Douglas-fir.

• Can be controlled in Christmas trees with fungicides.

Pine Needle Cast

• Caused by several fungal organisms.

• Worse in areas of poor air drainage.

• Especially bad on 2 needle pine species.

Poplar rust on D. Fir

• Alternate hosts are Douglas-fir and populus species.

• Orange pustules appear on Douglas-fir in late spring.

• Can cause substantial defoliation.

Different Insects Attack Different Parts

of the Tree

Sucking Insects

• Aphids• Adelgids• Scales• Mites

Adelgids

• Balsam wooly adelgid• Aphid like insects that

do both chewing and sucking damage.

• Cause distorted growth, but rarely kill trees.

Cooley Spruce Gall Adelgid

• Seven different life stages.

• Forms cone-like galls on spruce.

Cooley Spruce Gall Adelgid

• On Douglas-fir, crawlers form cotton ball like spots on leaves.

• Only damages current needles.

Needle scales

• Wide variety of conifers affected.

• Most severe on cedars and pines.

• Foliage damaged, but trees not killed.

Pine Needle Scale

• Common on many species of pine

• Damages foliage and weakens trees.

Spruce Spider Mites

• Attack several conifer species.

• Worse during summer hot, dry weather.

• Drought worsens attack.

Boring insects

• Bark Beetles• Twig Weevils• Root Weevils• Wood Borers• Needle Midges

2007 Vineyard Mountain Bark Beetle Attacks

Bark Beetles

• Most common insects linked with death of local conifers.

• Individual insect species only attack certain species and/or genuses of conifers.

• Can have epidemic outbreaks with the right conditions.

• Most are native insects and are always present.

Douglas-fir Bark Beetles

Ipps Damage to Ponderosa Pine

5 Spined Ipps Damage to Pine

Bark Beetle Signatures

Population Control

• Important to understand life cycle of insects.

• Wood containing insects should be destroyed or treated to kill them.

Douglas-fir Twig Weevil

• Boring insect that infests small branches.

• Associated with stress weakened trees.

• Rarely cause death, but further weaken trees.

Close up of Twig Weevil

White Pine Weevil

• Serious problem on young spruce trees.

• Attacks and kills tree leader.

• Infested leader will show boring holes

A big pine problem

Sequoia Pitch Moth

Flat Headed Wood Borers

• Bore beneath bark and into wood.

• Attack weakened trees. Will attack healthy trees during droughts.

• Found many times in firewood.

Douglas-fir Needle Midge

• Douglas-fir is only tree attacked.

• Damage to needles done by tiny worms.

• Infested needles fall of tree by Christmas.

• Problem mainly for Christmas tree growers

Needle Feeders

• Can be very scary for homeowners.

• Rarely are epidemic in our climate.

• Can cause severe problems in native forests.

2010 Benton County Sample

Field Damage Near Summit

Look at the Litter Carefully Reveals- Sawfly Larvae Damage

Hoodoo Pass Disaster

Spruce Budworm

• Serious pest in Cascades and Eastern Oregon.

• Killed millions of acres of forest nationwide.

• Damage is cyclical.• Little problem in local

area.

Douglas-fir Tussock Moth

• A serious epidemic insect in Eastern Oregon in the 1980’s

• Found in Willamette Valley, but not a big threat.

Silver Spotted Tiger Moth

• Attacks mostly Douglas-fir

• Voracious feeder.• Can defoliate small

tree in a couple of days.

• Doesn’t kill trees.

Gypsy Moth

• Serious non-native insect.

• Attacks nearly all tree species.

• Is especially damaging to conifers like Douglas-fir.

• Population currently under control in OR.

Other Tree Damage

• Air Pollution• Sunburn• Frost injury• Nutritional deficiency• Stem rots• Animal damage

Air pollution damage

SO2 and alder.

Sun & Heat Damage

• Drooping foliage.• Necrotic needles in

late summer.

Sunscald to Trunk

• Problem on small trees with thin bark.

• Made worse by pruning lower limbs too soon.

Cold Damage

• Foliage desiccated by cold, dry winds.

• Buds/tissue killed by early or late frosts.

Current Season Needle Necrosis

• Impacts grand fir and noble fir grown on Valley floor.

• Serious Christmas tree problem.

• Cause is calcium deficiency in late spring.

• Best cure is genetics.

Stem Rots

• Common problem around homes.

• Conifers vary in response to injury.

• Long term rot and breakage is main problem.

December 2007

Storm Damage

The “Root” of the Problem

Important Clue to Damage

Butt Rot from Phellinus pini

Animal Damage Problems

• Rodents• Deer & Elk• Others

Deer/Elk in the Home Landscape

• Conifers used to browsing.

• Main long term damage to browsing is slowed growth and extra leaders.

• Antler rubbing can be severe-don’t prune to soon.

Controlling Browse

• Fences work best.• Small trees can be

protected by plastic tubes or other devices.

• Repellants have variable effect.

Mice/Vole Damage

• Serious problem in new planting.

• Girdling of bark near ground line can kill small trees.

• Best treatment is to remove hiding cover around trees.

Gopher Damage

• Worst on pines.• All conifers are

somewhat susceptible

• Fleshy rooted weeds are a magnet.

• Trapping is most effective treatment

Porcupine Damage

• Serious problem, particularly on pines.

• Can kill limbs or tree tops.

• Can be confused with squirrel damage.

• Populations are currently building in Willamette Valley

Culprit?

2010 Damage to Pines

The Culprits: Silver Gray Squirrels

Bob McNitt, aka, the pine guy examines

damage to native

ponderosas

Mike Melcher

Who’s been

messing with my trees?

The Damage and the Culprit

Human Damage to Trees

• Wires left on trees.• Nails or other metal in

trees.• Wounding by mowers,

vehicles or other source.

Construction Damage

Roots

Chemical Damage

• Each chemical has distinct damage pattern on various tree species.

• Resistance to damage varies greatly by species and time of application.

Diagnosing Tree Problems

• Identify species involved

• When injury noticed• Part of plant showing

injury– Roots, top, stem– Age of foliage– South vs north side

More Diagnosis Questions

• Species affected?• Distribution of

damage- on plant, on planting.

• Disturbance around tree anytime recently?

• Chemical applications?

Bottom Line for Conifers• Conifers are hardy and

tough to injure.• When injured severely,

conifers seldom recover.

• Death in conifers usually linked to several causes.

• It takes decades to replace a nice one.

References for Diagnosis

• Tree Identification Books• Insects that Feed on Trees and Shrubs• Diseases of Trees and Shrubs• PNW Insect and Disease Control

Handbooks from OSU• Several other reference books in MG

reference library and Rick’s office.

Linn-Benton Pest Scene Investigator Team

QUESTIONS?