Nancy R. PatakyDirector, Plant Clinic University of Illinois

Common Conifer Diseases of Forests

Illinois (University of Illinois)Plant Clinic1401 W. St.Mary’s RdUrbana, IL 61802http://plantclinic.cropsci.illinois.edu/

Iowa (Iowa State University)Plant and Insect Diagnostic Clinic327 Bessey HallAmes, IA 50011http://plpfserve.plp.iastate.edu/pdc/welcome

Wisconsin (University of Wisconsin)Plant Disease Diagnostics Clinic1630 Linden DriveMadison, WI 53706-1598http://www.plantpath.wisc.edu/pddc/

Tri-State University Plant Clinic Contacts

Plant Clinic 1401 W. St. Mary’s Rd. Urbana, IL 61802

217-333-0519

May thru mid-September

Today Our Focus is on the Forest

Forest

NurseryLandscape

Plant Disease

Pyramid

Conditions necessary for plant disease to occur

Host

Pathogen Favorable Environment

Time

Pathogen-Agent causing theinfectious disease

A.Fungi

B.Bacteria

C.Virus

D.Nematodes

Most conifer diseases are caused by a fungal pathogen.

One disease discussed today is caused by a nematode.

Conifer Diseases Prevalent in Forests

1.Foliar Disease

2.Foliar & Stem Disease

3.Stem Disease

4.Wilts

5.Root / Butt Rots

Needle cast – New needles green, one year old needles brown, two year old needles cast (dropped)

Lophodermium

Swiss needle cast

Rhizosphaera needle castCyclaneusma needle cast

Needle blight – affects needles of any age with affected needles usually remaining attached

Brown Spot Needle Blight Dothistroma Needle Blight

Management of Needle DiseasesForest Trees: Most have no impact

But…be certain of your diagnosis

Ornamental:

Improve air flow

Resistant varieties, where possible • Ex. Norway Spruce resistant to Rhizosphaera

Protective fungicides• Rhabdocline, Rhizosphaera, Swiss Needle Cast in Spring

• Cyclaneusa & Lophodermium in Summer

Conifer Diseases Prevalent in Forests

1.Foliar Disease

2.Foliar & Stem Disease

3.Stem Disease

4.Wilts

5.Root / Butt Rots

Diplodia Blight of Pine•Symptoms appear on both foliage and stems•Cankers may be present

Diplodia Blight of Pine – Fruiting bodies and spores

Fruiting bodies on needles

Spores

Fruiting bodies on cones

Diplodia Canker Phase

Diplodia/Sphaeropsis tip blight and canker

• Hosts– Austrian, Scotch, &

Ponderosa pine (& other stressedconifers)

• Symptoms & signs– Shoot tip die-back– Branch cankers on

stressed trees– Fruiting bodies at

base of needle clusters and on cone scales

Diplodia ManagementForest Trees: Impact mostly to seedlings

Ornamentals: Serious

Remove infected wood or cones when dormant

Do not plant susceptible pines near mature, infected trees

Fungicides ? – three sprays: bud break, half candle, full candle

Efficacy of Sprays for Diplodia?•Latent infection of healthy Austrian & Scotch pines is common. (Kentucky study, 2001)

•If fungicides are used, pick systemic product

•Stressed trees more susceptible (multiple studies) – especially drought

Conifer Diseases Prevalent in Forests

1.Foliar Disease

2.Foliar & Stem Disease

3.Stem Disease

4.Wilts

5.Root / Butt Rots

Stem DiseasesCankers are the primary symptom. Dieback follows. Often stress related. Cytospora

on spruce

Cytosporaof Spruce

Typically affects lower part of tree first and moves upward each year

CytosporaCanker of Spruce

Cytospora (Leucostoma) Canker of Spruce

Gummy exudate and canker below. Probably won’t see fruiting bodies.

Management: Cytospora Canker of SpruceForest Trees: Not an issue. Urban

stress absent

Ornamentals:•Find source of stress•Correct stress•Remove dead wood•Improve vitality

Scleroderris Canker (Gremmeniella abietina)

•Causes shoot and possibly tree death

•Scotch, Jack, Red pines –Northern Wisc

•Stress is definitely a factor

•Infection 1o May-July via buds or needles, but symptoms next spring

Scleroderris Canker of Conifers1. Lake Strain

Young trees 6’ or lessBud dieback, orange base to needlesCankers on young trees – lowest branches under snowYellow-green stain in cambium

2. European StrainAll pines

Much more serious –may kill treesNot in Midwest

Orange base to needles in Spring

Threat to young trees 6’ or less

Scleroderris Canker Management

Ornamentals: Not an issue

Forest Trees:

Do not replant in an affected area

Use only disease-free stock in the Spring

Chemicals available in nurseries

Quarantines on Christmas trees grown in areas with European strain

Some resistant varieties

White pine blister rustHosts – Needs both

White Pine Ribes (currant and gooseberry)

Currant

White pine

Favored by cool, moist conditions and in low lying areas

White pine blister rust

Spores released by Ribes specis in midsummer to early fall cause yellow or reddish spots on pine needles.

Infected pine needles may turn yellow and drop.

Fungus moves into branch and swollen and blistered pine twigs & branches develop 2-3 years later.

Girdled branches are blister rust flags…..Probably what we see first

White Pine Blister Rust Cankers Later Exude Resin

White pine blister rust Management•Prune infected branches well before they reach the trunk

May work on ornamental trees

Not practical for forest

•Remove alternate hosts within 1,000 ft

•Seek rust-resistant planting stock

**Interesting Note:

The first quarantine laws were enacted in 1912, because of the need to control movement of this fungus. The fungus is from Asia but white pine is native. Imported on European white pine breeding stock

Pine gall rusts• Hosts

– Austrian and Scotch pine• Symptoms & signs

– Swellings and galls on main stems or branches

– 2 yr-old galls release yellow spores in spring

• W. gall rust pathogen re-infects pine only

• E. gall rust pathogen infects oak (red/black) then back to pine (all within 3-4 wks)

Pine

Mature & active gall

Immature gall

Pine gall rustsGalls often not noticed

during first year after infection

Before spring, remove infected pine branches or whole trees

Check nearby wild areasApply Bayleton or

mancozeb every 7-14 days during pine shoot elongation.

Gouty Oak GallCaused by an insect

(wasp)

Management of Rust Diseases•White pine blister rust branches pruned and removed. Remove Ribes alternate hosts. No fungicides

•Pine gall rusts are pruned in early spring. Fungicides may help ornamental or nursery stock.

•Problem in nurseries

•Problem in Jack pine plantations

Conifer Diseases Prevalent in Forests

1.Foliar Disease

2.Foliar & Stem Disease

3.Stem Disease

4.Wilts

5.Root / Butt Rots

Vascular Diseases

Pine Wilt is the only vascular disease of conifers in the Midwest.

Pathogen invades the water conducting system of the tree

Pine

Pine Wilt caused by pinewood nematode

Kills trees in a season

All pines are host except white pine (usually)

Vector – Pine Sawyer Beetle

Wood extract for PWN assay

Pinewood nematodes viewed through a dissecting microscope

Pine Wilt Management• Correctly Identify• Remove tree before mid-March• Chip, burn, or bury tree• No chemicals effective

Conifer Diseases Prevalent in Forests

1.Foliar Disease

2.Foliar & Stem Disease

3.Stem Disease

4.Wilts

5.Root / Butt Rots

Root RotsSymptoms include off-color foliage, smaller than normal leaves, stem dieback, leaf scorch, branch death, wilt, decline, and possible plant death.

White Pine

Armillaria root rot• Hosts

– Hundreds of woody plants• Symptoms & signs

– Young trees suddenly turn yellow, then reddish-brown, then die. (usually following moisture stress)

– White mycelium under the bark at the base of the tree

– Spongy or stringy white wood rot

– Honey mushrooms

Look for white mycelial fans of growth between bark wood

Aka Shoestring Root Rot because of rhizomorphs

Armillaria Root Rot Fruiting Bodies

FBs Produced in late summer or fall

Armillaria root rot spreadAirborne spores (occasional)

Growth of fungus from tree to tree

Rhizomorphs

Root grafts

Armillaria ManagementAvoid using recently cleared land, especially deciduous forests.

Remove infested stumps and roots –may survive for decades in large stumps (for high value sites)

Reduce stress. Use local seed source.

No effective, practical control

Annosum Root Rot (Heterobasidion annosum) (Fomes annosus)

•Decay of roots and butt

•Often kills

•Over 200 hosts including red, white, Jack pine and white spruce

•Infects through freshly cut stumps and moves to healthy trees via roots

Image by Joseph O’Brien

Symptoms•Reduced growth, but often none aboveground until the tree dies

•Windthrown trees

•Stained and resin soaked wood in butt of tree and roots leak resin

•Wood soft and stringy

•Stringy yellow decay in roots

Image by William Jacobi

Annosum Root RotWhite mycelium under bark

Basidiocarps around base of stump

mid-summer popcorn appearance

fall bracket shaped

Image by Paul A. Mistretta

Annosum Root Rot Management•Treat cut stumps to prevent establishment

Big problem in plantations where thinned

Not so much of a forest problem

Sporax* or other registered product

•Avoid planting in site formerly used for agriculture

•Avoid areas with a pH>6

•Disease favored by well drained, sandy soils

*Sporax by Wilbur-Ellis is a borate based fungicide registered for use to control this fungus

Schweinitzii Root and Butt Rot (Phaeolus schweinitzii)•Common on conifers, espDouglas fir

•Enters wounds

•Primarily root rot

•Forms very ornamental conks on stumps and roots (dye source)

Start yellow-green

then yellow-brown

then dark brown

By Andrej Kunca

by Larry Grand

Image by James Byler

Schweinitzii causes a brown cubical rot of upper roots and lower bole

White Pine Decline

White Pine Decline

•Delayed bud break•Reduced shoot elongation•Wilting and browning•Dead needles hold on•Exact Cause Unknown

White Pine Roots

White Pine Decline Healthy

Procerum root diseaseHosts

E. white, Austrian, & Scotch pine

Vector implicatedWeevils & bark beetles

Symptoms & signsDelayed bud-break &

reduced shoot lengthWilting and uniform

browning of needlesResin at base of tree &

evidence of insect attack

Procerum root disease

• Conditions– Various stress factors– Common on wet or poorly

drained sites• Management

– Avoid using stress-prone planting sites

– Remove infected stumps.

Leptographium procerum

Stained wood near the base of the tree and excessive sap exudate at the soil line are symptoms of this disease.

Causal fungus

Management of Root Rot Diseases

•Promote tree health to ward off problems

•Plant in well drained sites

•Plant in site appropriate to species needs

•Remove stumps and roots of dead trees

•Fungicides may help in nursery setting

•Does it help to remove conks? NO!

Helpful References are Listed in Handout

http://www.aces.uiuc.edu/~vista/rpd.html

How to Submit a Sample to a Plant Clinic

•Address to local plant clinic

•Provide Information

•Sample live, symptomatic areas

•Provide enough to work with and share

•Do not use plastic

•Use sturdy box

•Provide Pictures

What do I send to a lab?

What do I send to a lab from these spruces?

Illinois (University of Illinois)Plant Clinic1401 W. St.Mary’s RdUrbana, IL 61802http://plantclinic.cropsci.illinois.edu/

Iowa (Iowa State University)Plant and Insect Diagnostic Clinic327 Bessey HallAmes, IA 50011http://plpfserve.plp.iastate.edu/pdc/welcome

Wisconsin (University of Wisconsin)Plant Disease Diagnostics Clinic1630 Linden DriveMadison, WI 53706-1598http://www.plantpath.wisc.edu/pddc/

Tri-State University Plant Clinic Contacts

Nancy PatakyUniv of IllinoisPlant Clinic Directornpataky@uiuc.edu217-333-2478