Presented by Dwight Scarbrough Entomologist USDA Forest Service Forest Health Protection March 19, 2013 Edition Oxford 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 Environment Pathogen 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 pine Needlecast

Other Foliage Diseases Snow Mold Elytroderma Needlecast Marssonina Leaf Spot of Aspen

Elytroderma Small, dense witches’ brooms

Cedar-apple Rust Gymnosporangium 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 centers Decay 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 Intensification Dwarf 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 Mistletoe Brooms 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: FS-R1 Hazard Tree Safety Initiative – “Up the Ante” Website: Hazard Tree Information and Safety Websites FS-R6 Field Guide for Danger Tree Identification & Response: grasslandhealth/insects-diseases/?cid=fsbdev2_ FS-R6 Hazard Tree, Long Range Planning for Developed Sites: pdf

For More Information r4/spf/fhp/field_guide/toc.htm

Additional Information sources in Utah or Nevada John C. Guyon Plant Pathologist USDA Forest Service Forest Health Protection 4746 S East Ogden, UT Phone: (801) in Southern Idaho Dayle Bennett BFO Group Leader USDA Forest Service Forest Health Protection 1249 S. Vinnell Way Boise, ID Phone: (208)