Native and Exotic Root Diseases Of California
Pete Angwin Plant Pathologist USDA Forest Service Forest Health Protection Redding, California Root Diseases
Pages 25-42 In The Training Manual Caused by fungi with the ability to infect and kill living roots and spread through the root system to adjacent healthy trees Native vs. Exotic Root Diseases In California
Native Exotic
Heterobasidion Root Port-Orford-cedar Root Disease Disease
Black Stain Root Disease
Armillaria Root Disease Types of Root Disease
Rootlet necrosis (Death of feeder roots)
Decay (Breakdown of host tissues)
Vascular wilt (Plugging of vascular elements) Root Disease Effects
Mortality Growth reduction Volume loss Tree hazard Stress Root Disease Effects
Important natural disturbance agents Create canopy gaps, alter forest structure Enhance vegetative and wildlife diversity General Signs and Symptoms of Root Disease Loss of Needles & Thinning Crowns
Be aware that other insect and disease agents produce similar symptoms. It is very important to look for additional clues that will help you determine what the actual problem is. Discoloration of Tree Crown
May be due to the root disease itself or secondary attack by bark beetles Sap Bleeding From Lower Bole Pattern of Dying of Individual Trees
Progression of deterioration of adjacent trees.
Sometimes scattered individual dead and dying trees Mushrooms or Conks at Base of Tree Windthrow
Advanced rot in the structural roots or no roots present means root disease is probably active on the site. Bark Beetle Attacks
Beetles will attack trees with root disease as well as trees weakened by fire, drought and overstocked conditions. When you see beetle attacks it is important to look for other clues that may indicate root disease is present. Two Most Damaging Native Root Diseases In California Heterobasidion root disease Black stain root disease
Also: Armillaria root disease Heterobasidion Root Disease
A Root and Butt Rot
Heterobasidion irregulare and Heterobasidion occidentale What is in a Name ? Common Names Annosus root rot Annosus root disease Annosum root rot Annosum root disease Heterobasidion root disease Latin Names Fomes annosus Heterobasidion annosum The New Names are here: Heterobasidion Root Disease Caused by two fungi: Heterobasidion irregulare (formerly “p-type” of H. annosum) – pines, incense cedar, western juniper, manzanita, madrone Heterobasidion occidentale (formerly “s- type” of H. annosum) – true firs, spruce, giant sequoia, hemlock
(Otrosina and Garbelotto, 2010) Heterobasidion Root Disease Reports in California Why Heterobasidion is Such a Problem
Strong Pathogenic Abilities – Attack living roots – Can spread aerially by spores, colonizing fresh stumps and wounds Why Heterobasidion is Such a Problem
Strong Saprophytic Abilities – Colonizes dead and dying stumps out to roots – Decays heartwood leaving stringy white rot – Occupy root systems for up to 35-50 yrs!
Both species can colonize pine stumps! H. occidentale can use pine stumps as a “bridge” to adjacent live fir H. irregulare only occasionally colonizes fir stumps Why Heterobasidion is Such a Problem
Strong Saprophytic Abilities – Colonizes dead and dying stumps out to roots – Decays heartwood leaving stringy white rot – Occupy root systems for up to 35-50 yrs!
Both species can colonize pine stumps! H. occidentale can use pine stumps as a “bridge” to adjacent live fir H. irregulare only occasionally colonizes fir stumps Symptoms: Faded or Flattened Crown Sapling Mortality Near Stumps Lack of Regeneration Within Root Disease Center Heterobasidion Root and Stem Decay
Laminant decay with pits on one surface Stringy Rot in Roots Advanced Decay Spongy White With Black Flecks Signs: Conks are commonly found in hollowed out stumps “Popcorn” Conks
On Roots of Small Saplings or Under Bark Lab Examination Asexual spores Spiniger meineckellum Management Strategies Prevention – Stump Treatment . Sporax = Borax = Sodium tetraborate hydrate . Cellu -Treat = Disodium Octaborate Tetrahydrate (New liquid borate formulation) – Minimize injuries to trees (esp. fir)
Silvicultural Choices – Plant or manage non-hosts of local Heterobasidion species
Eliminating infection centers – Uprooting and trenching – Removing healthy margin of trees Sporax Treatment of Freshly-Cut Stumps
Surfaces are receptive for up to 2 weeks
Treat stumps of fire- killed trees if: – tree dead less than 18 months – trees retain any needles- green or brown Sporax application
34 Cellu-Treat application on Plumas NF using back-pack sprayer
35 Cellu-Treat Can Be Applied To Irregular Stump Surfaces Black Stain Root Disease Caused by Leptographium wageneri L. wageneri Causes A Vascular Wilt
Fungal hyphae in xylem tracheids L. wageneri In Cross Section Of Root
Black Stain Fungus vs. Blue Stain Fungus Black stain root disease is spread via root contacts and insects Black stain can weaken trees, making them susceptible to bark beetle attack Three host-specific varieties of L. wageneri Leptographium wageneri var. wageneri
Host:Pinyon pine Leptographium wageneri var. ponderosum
Hosts:Ponderosa, Jeffrey and lodgepole pine, and occasionally sugar pine and hemlock Leptographium wageneri var. pseudotsugae
Host: Douglas-fir Distribution of Black Stain Root Disease In California Symptoms
Symptoms include all the typical root disease symptoms, including sparse & chlorotic crowns, reduced growth; heavy stress cone crops, and basal resinosus. Distinct disease centers or scattered infected trees. Scattered Jeffrey pine mortality on the Modoc National Forest Signs The major sign of black stain root disease is a dark brown to purple black stain in the sapwood of infected roots and lower stems. This is diagnostic! Disease Cycle
Infection centers are initiated by root-feeding bark beetles and weevils that carry fungal spores on their bodies. These insects are attracted to wounds and weakened, low vigor trees. Infection appears to be favored by cool, wet environments. Local spread is via small rootlets, either by root-root contact or short-distance growth of the fungus through the soil. Disease Cycle
The fungus doesn’t survive long in dead host trees, so disease centers often expand and break up as trees in the inside of the centers die. The fungus can survive in vigorous live trees, and make itself known during drought or other periods of stress. Management Strategies
Consider management objectives. Will expected disease levels be acceptable? Maintain trees in a vigorous condition with adequate spacing Avoid disturbance and injury, especially during times of peak beetle activity. Consider patch or clear cutting in highly diseased areas. Replant with non-host or a mix of species. Thinning can help by enhancing tree vigor and creating conditions that are less favorable for the pathogen, but if not done carefully, can increase disease levels. Management Strategies- Thinning
Thin aggressively, leaving an understocked stand. This will minimize future stand entries. Favor non-host species or a mix of species and remove diseased or weakened trees. Thin as early in the stand rotation as possible. Minimize soil disturbance, compaction and tree injury. Consider dry season operation, skyline yarding, minimize and designate skid trails, and avoid new road construction. Management Strategies- Thinning
If possible, thin when insect vectors are least active, generally from late June to early September. Monitor post-harvest levels of black stain root disease to evaluate the effectiveness of various levels of thinning. Black stain root disease is common in northern California, but ongoing thinning in areas such as McCloud Flats has lessened the impacts. However, its impacts, with those of the western pine bark beetle, increase during droughts. Armillaria Root Disease Armillaria Root Disease
Shoestring root disease Oak root disease – Mostly A. mellea in California Other species are weak pathogens or saprophytes – California’s species are weak pathogens or saprophytes – More pathogenic species of Armillaria are in Oregon and other states Damage
Not usually a big problem Stringy root decay Weakly attacks stressed hardwoods and conifers Blowdown/Tree hazard A. mella damage is more common in orchards and vineyards and in areas that are overwatered Armillaria Root Disease: Thick, white, mycelial fans under the bark Armillaria root disease Rhizomorphs (“shoestrings”) Armillaria root disease
Fruiting bodies are produced in the fall Temperature and moisture dependent Management
Not usually a big problem Since disease is more prevalent in stressed stands or sites, keep competition down Avoid cutting or killing oaks near young conifers Avoid overwatering oaks in landscape Replant landscape site with tolerant or resistant species Port-Orford-cedar Root Disease
Caused by Phytophthora lateralis, an exotic pathogen
Hosts are Port-Orford-cedar and Pacific yew
First found on nursery stock in 1920’s
Pathogen origin most likely Taiwan on hinoki cypress (Chamaecyparis obtusa) 99%+ Mortality of Port-Orford-cedar
Once infected, seedlings die within a few months, mature trees within 2-4 years Port-Orford-cedar Root Disease
Pacific yew (Taxus brevifolia) becomes infected only under high inoculum loads Impacts of Port-Orford-cedar Root Disease
Loss of Port-Orford-cedar from riparian zones (and loss of wildlife habitat) Loss of timber resource Road closures to protect or prevent disease spread Restrictions on bough harvest Cost of control Port-Orford-cedar Root Disease
Cambial stain of Phytophthora lateralis on Port-Orford-cedar Range Of Port-Orford-cedar Chamaecyparis lawsoniana Pathogen was introduced into the natural range of POC near Coos Bay in the 1950’s
All major watersheds in the range of POC are now infested The Pathogen- Phytophthora lateralis
“Phytophthora” means plant destroyer
“lateralis” chlamydospores grow laterally (on sides of) hyphae Characteristics of Phytophthora lateralis A “water mold” Narrow host range Germinates and infects under cool, moist conditions Spreads actively in water by zoospores Forms resistant spores (chlamydospores) that can survive up to 7 years when conditions are not favorable Can spread long distances in soil Sporangium releasing zoospores
Chlamydospore
Empty sporangium
sporangia filled with zoospores Movement by Water Movement by Water Movement By Root Grafting Soil Movement by Equipment
Long distance spread in organic matter and soil
Heavy equipment can transport Phytophthora lateralis Soil Movement by Vehicles Soil Movement by Boots General Management Strategies to Maintain and Restore Port-Orford-cedar
Slow the spread of Phytophthora lateralis Protect uninfested areas Breed to develop disease resistant trees Grow Port-Orford-cedar where it has a good chance to survive Specific Management Strategies A) Operate in dry season B) Cease operations during significant rain events that happen in the dry season C) Access uninfested sites before infested sites D) Use uninfested or treated water E) Road and trail management/improvement F) Retain/feature Port-Orford-cedar on low- risk sites G) Wash vehicles Specific Management Strategies
H) Wash boots and equipment I) Seasonal road closures J) Permanent road closures / no new roads K) Roadside sanitation L) Eradication (POC removal from infested sites) M) Plant resistant stock Equipment Washing Roadside Sanitation POC Resistance Program Zoospores on susceptible and resistant roots
Photos by Eun Sung Oh, Oregon State University POC Resistance Program- Common Garden Plots
Humboldt Nursery and Trinity Sites in California (2 more in Oregon) The JR13 Breeding Zones
5 Breeding Blocks
2 each in California and Oregon
1 spans the state boundaries (range of the Redwoods)
13 Breeding Zones Collect and Test Potentially Resistant POC From Every Breeding Zone Resistant POC is now available for planting! Questions?