Presented by Dwight Scarbrough Entomologist USDA Forest Service Forest Health Protection March 19,...
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Transcript of Presented by Dwight Scarbrough Entomologist USDA Forest Service Forest Health Protection March 19,...
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.
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.
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
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
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
• 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
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
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)
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!
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
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.
Dodder (Cuscuta sp.)
Mats of dodder plant-strands
Vines attacking host
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.
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_027046FS-R6 Hazard Tree, Long Range Planning for Developed Sites: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_026108.pdf
Additional Information sources
in Utah or Nevada
John C. GuyonPlant PathologistUSDA Forest ServiceForest Health Protection4746 S. 1900 EastOgden, UT 84403Phone: (801) [email protected]
in Southern Idaho
Dayle BennettBFO Group LeaderUSDA Forest ServiceForest Health Protection1249 S. Vinnell WayBoise, ID 83709Phone: (208) [email protected]