Presented by Dwight Scarbrough Entomologist USDA Forest Service Forest Health Protection March 19, 2013 Edition Oxford Suites, Boise, Idaho, USA Presentation.

Presented by

Dwight ScarbroughEntomologist

USDA Forest ServiceForest Health Protection

March 19, 2013 EditionOxford Suites, Boise, Idaho, USA

Presentation Developed by James Hoffman Plant pathologist (Retired)

Principles of Plant Pathology and Important

Forest and Range Diseases in Idaho

Presentation Outline

Section 1: Introduction to the Basic Principles of Plant Pathology.Section 2: Important Plant Pathogens in Forest and Range Ecosystems in Idaho.

Section 3: Decline Diseases: A Complex of Biotic and Abiotic Origins.

Section 4: Hazard Trees and Your Safety.

Section 1:Introduction to the Basic

Principles of Plant Pathology

What is a Plant Disease?

A disturbance that interferes with a plant’s “normal” structure, function, or physiological processes.

As opposed to a tree injury which is caused by a single event (e.g. hatchet blow to a tree)

Disease Definitions

Parasite – an organism that lives on or in another organism.

Host – an organism that provides nutrition for an invading parasite.

Pathogen – an agent that causes disease.

Disease Triangle Disease is the product of three

interacting factors

Host Plant

EnvironmentPathogen

Disease

Signs of Diseases

• The physical presence of the pathogen on the surface or inside the plant–Fruiting bodies, fungal tissues, dwarf mistletoe shoots, etc.

–Geeks look for spores (under a microscope)

Symptoms

The expression of the host to the pathogen infection.

– Tissue death, abnormal growth forms, branch or top-dieback, lesions, yellowing, decay, defoliation, etc.

Is this a diseased cottonwood tree?

No, it’s early fall!

Types of Diseases

Tree Disease Concepts, Paul D. Manion

Biotic diseases (Infectious)

Abiotic diseases (Non-infectious)

Decline diseases- (Complicated as many pathogens are involved over a long time period.)

Fungi Parasitic Plants Bacteria Mycoplasmas =

Phytoplasmas Virus Nematodes Others?

Types of Biotic Diseases (Infectious plant disease

agents)

Moisture imbalances (Drought)

Wind Temperature Nutrient and mineral

imbalances Air pollution Soil acidity or alkalinity Others?

Types of Abiotic Diseases (Non-infectious plant disease

agents)

Common Categories of Fungal Diseases

Foliage diseases

Cankers (usually stem rusts)

Decays and Rots

Root diseases

Vascular wilts

Management Techniques for Plant Diseases

Regulatory Methods Quarantines and Inspections Cultural Methods Host Eradication Rotation to Non-host Species Sanitation Altering the Environmental Conditions Biological Control Chemical Control No Control

Section 2:Important Plant Pathogens

in Forest and Range Ecosystems in Idaho

Foliage Diseases

• Needlecasts • Needle

Blights• Shoot

Blights

• Mostly caused by fungi

• Cause spotting and discoloration

• Cause premature defoliation

• May reduce growth

• Only a problem when infection occurs over consecutive years

Signs of Foliage Diseases

Signs

• Fungal fruiting bodies are often visible on the surface of infected needles

Snow Blight

Lophodermium needle cast

Elytroderma needle cast

Symptoms of Foliage Diseases

• Leaf spots or discoloration• Dead/dying foliage• Thin crowns• Degrees of Defoliation

Dothistroma needle cast

Pine needle cast

Lodgepole pineNeedlecast

Other Foliage Diseases

Snow Mold

Elytroderma Needlecast

Marssonina Leaf Spot of Aspen

Elytroderma

Small, dense witches’ brooms

Cedar-apple RustGymnosporangium sp.

Orange “Jello” on Junipers in spring

Galls on junipers in fall

Control of Foliage Diseases

Control usually not needed nor is it practical

Maintain mixed species composition in stand

Maintain healthy, vigorous trees

Role of fire? High value trees – both

protective and controlling fungicides

Cankers – a symptom of disease

• Localized area of dead bark or cambium– Often sunken because

the tree continues to expand around the infection site

• Very common– More common on thin-

barked species (aspen)

• Usually caused by fungal infections that enter through wounds

Identifying Cankers

Hail damage

Fungal Canker Symptoms

• Expanding edges• Callus ridges and sunken wood

• Dead wood inside margin

Black knot of cherry

Cytospora canker Target canker 12

Signs of Cankers

• Sometimes fruiting bodies are invisible

• Often perennial & expand until the tree is girdled

• Most important & common group of diseases in aspen

• Cause direct mortality

• Provide entry point for decay fungi

Cankers of Aspen

Rust Galls and Cankers

Cause diseases of leaves branches and stems

Rust colored spores

All require a living host (obligate parasites)

Complex lifecycle often involving 2 different plant hosts and up to 5 spore stages!

Western Gall Rust

• Most common canker in pines in this area

• A “pine-to-pine” rust

• Causes hip cankers that rarely girdle the tree

• Wind-snapping at canker is common

• Fungus enters through needles

Western Gall Rust

Attacks all 2-3 needle pines:ponderosa, lodgepole, scots, and Austrian pines.

Western Gall Rust -Hip cankers on stems create weak areas…

White Pine Blister Rust

Introduced from Europe in the early 1900’s

Lethal, invasive disease

Infects all species of white, 5-needle pines

In Central Rockies this would be limber, whitebark, and bristlecone pines

Alternate host = currants and gooseberries

Symptoms of White Pine Blister Rust

• Cankers are often gnawed on by rodents

• Swollen cankers with orange margins

• Roughened bark as a result of past fruiting

• Branch death (flagging)

Signs of White Pine Blister Rust

Resinous, diamond shaped cankers on branches/stems

Orange blisters and spores that infect the alternate host

White pine blister rust

in the Central Rockies

2005

Other Rusts

Spruce and Fir Broom Rust

•Common but do not cause serious damage

Comandra Blister Rust

• Common and important in lodgepole and ponderosa pines

• Infects all hard pines• Causes top-kill

Decays (Rots)

Top rot, usually resulting from top breakage or damage

Stem or trunk rots

Butt rot

Root rot

White Rot Fibrous, usually whitish Break down lignin leaving

some cellulose intact Variable appearance

Brown Rot Brown in color, cubical, crumbly

Breaks down cellulose leaving lignin

Indicators of Decay

• Infection courts– Fire scars, logging scars,

broken/dead tops, fallen trees, old-growth characteristics

• Symptoms– Exposed decay, cracks, decayed

branch stubs, sparse foliage, cavity nesting birds

• Signs– Conks, fruiting bodies fungal

tissues, carpenter ant activity

Stem Decays

Decay in trees

Generally in inner wood

aka “heart rot”

Caused by fungi, that often form conks (sign)

White Trunk Rot (Phellinus tremulae)

On aspen only White rot Most infected

trees have conks

Conks

Saprots

“Pouch” fungus – insect correlation

In the sapwood

On dying or newly killed trees

Cryptoporous volvatus“pouch fungus”

Root Diseases

Most involve decay of the roots and lower stem “root and butt rots”

Hard to Diagnose– Symptoms are nonspecific, not

diagnostic, and may not appear

Greatest concern– Structural failure (snapping, uprooting)

of green trees!

Root Disease Spread

Subway: root-to-root

Airborne: by spores

Signs of Root

Disease -Fruiting Bodies

Phaeolus schweinitzii The “cow-pie” conk

Symptoms of Root Disease

Basal resinosis

Thin crown, stress crop, branch dieback

Expanding

mortality

centersDecay in roots

Symptoms of Root Disease

Vascular Wilts

Mostly caused by fungi

Invade conducting tissues, disrupt water movement, and cause wilting

Infect wounds on stems or roots

Diagnoses based on symptoms

Black Stain Root Disease

• Pinyon pine in CO, ID, UT, NV• Vectored by insects• Trees develop thin, chlorotic crowns

• Expanding infection centers• Black streaks in roots

Parasitic Plants

True Mistletoes (Phoradendron spp.)

Dwarf Mistletoes (Arceuthobium spp.)

Dodder (Cuscuta spp.)

True Mistletoes--Juniper Only true mistletoe in Great

Basin

Shrubby, photosynthetic plant

Acquires water from the host plant

SW-CO and NM, AZ, UT, & NV

Bird dispersed

Dwarf Mistletoes

(Genus Arceuthobium)

Parasitic plants that occur on all western conifers

Host specific Most common and

damaging tree disease in the Western US

Largest impact is growth reduction

Brooms may create fuel ladders for fire

Dwarf Mistletoes – Arceuthobium spp.

Very common on conifers

Small, leafless, parasitic flowering plant

Obtains water and nutrients from host plant

Sticky seeds are explosively discharged adhering where they land

Limber pine dwarf mistletoe

Pinyon pine dwarf mistletoe

Symptoms of Mistletoe

Branch swelling and cankers

Witches brooms - reduced vigor, dieback

Stunted growth –

62-year old “Bonsai”

Douglas-fir…

(Pathologist now the same vintage.)

Signs of Mistletoe

• Dwarf mistletoe plants

Dwarf mistletoe basal cups

Douglas-fir dwarf mistletoe

Dwarf mistletoe shoots

Spread and IntensificationDwarf Mistletoe

Spread occurs from tree-to-tree and within crowns

Distribution is patchy with discrete infection centers

Spread and Intensification

Plants tend to build up in bottom of crown and move up the crown

Mortality usually occurs from top down

Spread is quickest from an infected overstory to adjacent reproduction

Management of Dwarf Mistletoes

• Plant or favor non-host species• Prune brooms/infections• Remove infected trees/protect

uninfected regeneration– Buffer strips– Sanitation– Even-aged management– Partial cutting– Fire

• Do nothing• Chemical controls

• Ethephon (Chemical Name)– Also marketed under the trade

name of “Florel”• Causes abscission of dwarf

mistletoe shoots preventing the development of fruit and seeds.

Chemical Management of Dwarf Mistletoes

Dwarf MistletoeBrooms and Fire Effects

increases the fine fuels; are clustered in lower

tree crowns; collect at base of trees; on steep slopes, brooms

“pinwheel” downhill.

Is this a candidate stand for dwarf mistletoe control?

Yes! But it took more than one match…

Dodder (Cuscuta sp.)

Mats of dodder plant-strands

Vines attacking host

Section 3:Decline Diseases:

A Complex of Biotic and Abiotic Origins

What Are Decline Diseases?

Decline diseases are caused by the interaction of a number of interchangeable, specifically ordered biotic and abiotic factors which produce a gradual general deterioration, often ending in the death of trees.

Categories of Factors That Influence Decline

Disease Predisposing Factors: Long-term, slowly changing factors which alter a trees’ ability to withstand or respond to injury-inducing agents.

Inciting Factors: Short-term physiological or biological factors that generally produce dieback of small branches.

Contributing Factors: Include a collection of environmental factors and biotic agents.

Categories of factors influencing Declines

From: Tree Disease Concepts, Paul D. Manion

Decline Disease Cycle

From:Tree Disease Concepts Paul D. Manion

Section 4:Hazard Trees and Your

Safety

Size up snag hazards in work area. Never become complacent. Always look up. Get weather reports.

Scout out parking, sleeping, work areas, and safety zones. Advise co-workers of known hazards. Face your hazard and take appropriate action. Examine work area for other hazards. Take extra caution around heavy equipment. You are ultimately responsible for your own safety.

SNAG (Hazard Tree) SAFETY:

Don’t Let This Happen To You !!

Forest & Sade Tree Pathology Website:http://www.forestpathology.org/hazard.html

FS-R1 Hazard Tree Safety Initiative – “Up the Ante” Website:http://fsweb.r1.fs.fed.us/r1_www/projects/haztree_index.shtml

Hazard Tree Information and Safety Websites

FS-R6 Field Guide for Danger Tree Identification & Response:http://www.fs.usda.gov/detail/r6/forest-grasslandhealth/insects-diseases/?cid=fsbdev2_027046FS-R6 Hazard Tree, Long Range Planning for Developed Sites: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_026108.pdf

For More Information

http://www.fs.fed.us/r1-r4/spf/fhp/field_guide/toc.htm

Additional Information sources

in Utah or Nevada

John C. GuyonPlant PathologistUSDA Forest ServiceForest Health Protection4746 S. 1900 EastOgden, UT 84403Phone: (801) 476-4420jcguyon@fs.fed.us

in Southern Idaho

Dayle BennettBFO Group LeaderUSDA Forest ServiceForest Health Protection1249 S. Vinnell WayBoise, ID 83709Phone: (208) 373-4227ddbennett@fs.fed.us