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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.)
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
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
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
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
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.)
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?
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
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:
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_027046 FS-R6 Hazard Tree, Long Range Planning for Developed Sites: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_0 26108.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. Guyon Plant Pathologist USDA Forest Service Forest Health Protection 4746 S. 1900 East Ogden, UT 84403 Phone: (801) 476-4420 firstname.lastname@example.org in Southern Idaho Dayle Bennett BFO Group Leader USDA Forest Service Forest Health Protection 1249 S. Vinnell Way Boise, ID 83709 Phone: (208) 373-4227 email@example.com