oak wilt: identification & management … …. mark duff certified forester, board certified...
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Oak Wilt: Identification & Management
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Mark DuffCertified Forester, Board Certified Master Arborist
The Impact of Oak Wilt
• “Oak wilt is one of the most destructive tree diseases” (Young, 1949).
• “…. this disease has the potential of becoming one of the worst diseases to attack the forests of the state.” ( True and Gillespie, 1961).
• “Ceratocystis fagacearum, the cause of oak wilt, is a fungus with the potential to be one of the most destructive of all tree pathogens.” (Gibbs and French, 1980).
• “Oak wilt is now one of the most serious forest diseases in the country” ( Johns and Phelps, 1992).
The Impact of Oak Wilt
Thousands of acres throughout central and west Texas have been adversely
affected by oak wilt.
What Is Oak Wilt?
• Caused by the fungus Ceratocystis fagacearum
• Primary vascular pathogen
• Relies on insects for transportation
• Produces fungal mats
• Heat sensitive
• Unknown origin
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What Trees Are Susceptible?
Red Oaks are extremely susceptible to the pathogen and play a unique role in disease spread.
White Oaks are more tolerant of the disease; however, they are NOT IMMUNE to infection!
Live Oaks are intermediate in susceptibility; however, they are seriously affected due to their vast, interconnected root systems
that allow for disease spread among trees.
All Oaksand other members of the Beech family
(Fagaceae)
Above ground (long distance) via sap-feeding beetles:
Fungal spores are picked up from certain infected RED oaks and carried to fresh wounds on other oak species. New infection
centers are started in this manner.
How Is Oak Wilt Spread?
Sap Beetle
Fungal Mat
Fresh Wound on Oak
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How Is Oak Wilt Spread?
Underground (localized) via interconnected root systems:
This occurs primarily in LIVE oaks and is responsible for the majority of spread and tree deaths in central Texas.
Root Grafts
Rate of spread averages 50 feet to 75 feet per year.
Live Oak Mott
• Rapid defoliation• Death in 3 to 6 months• Spread to adjacent trees• No fungal mat formation• ~ 5 - 15% survival rate
Diagnosis in Individual Live Oaks
• Maintain leaves, then defoliate• Death in 4 to 6 weeks• Possible spread to adjacent trees• Possible formation of fungal mats• 100% mortality (no survivors)
Diagnosis in Individual Red Oaks
• Fungal mats contain spores
• Form only on RED oaks
• Form under bark
• Can have multiple mats per tree
• Produce a sweet odor like rotting fruit
• Mat production accelerated by cool, moist weather (springtime in Texas)
• Trees infected in fall / winter produce mats
Presence of Fungal Mats
Oak Wilt Management
Early detection and prompt action are essential for successful management of oak wilt.
There are four primary approaches used to manage oak wilt:
These measures will not cure oak wilt but can significantly reduce tree losses.
Prevention
Trenching
Fungicide InjectionPlanting
Prevention - Pruning
Peak beetle activity and fungal mat production occur
in the spring; therefore, avoid wounding oaks from February through June.
Regardless of season, immediately paint all pruning cuts and other wounds to oaks. This discourages contaminated sap-feeding beetles from visiting these wounds and introducing
oak wilt into these trees.
Prevention - Red Oak Management
Destroy infected red oaks to prevent fungal mat formation.
Never use infected red oaks for firewood!
Prevention - Firewood
• Transport and use only dry, well-seasoned firewood
• Leave unseasoned wood on site one year before moving
• Do not store infected wood near healthy trees
• Cover wood with clear plastic and bury the edges to prevent insects from leaving the pile
Trenching
Trenches must be placed a minimum of 100 feet ahead of the disease, excavated to at least 4 feet (sometimes deeper), and
sever all root connections to be effective.
100’
100’ minimum
Diseased
Healthy
Pushing / Rouging
Removing all oaks within the boundaries of the trench, specifically
the healthy and pre-symptomatic trees, can improve barrier effectiveness.
Fungicide Injection
• Used to protect high-value oaks in advance of an expanding oak wilt center
• Best candidates are healthy or pre-symptomatic live oaks 50 feet to 150 feet from symptomatic trees
• Injection does not stop root transmission of the fungus!
Fungicide Injection
Success depends upon the health of the tree, application rate, and injection technique.
Fungicide Injection
Several products are currently labeled and registered for this
treatment; however, only macro-injections of Alamo® have been
scientifically proven effective and continue to be the industry standard.
• Bark is thinner below the soil line
• Increases the number of potential injection sites
• Spreads out the wounding, especially if future injections are needed
• Research has demonstrated superior distribution of fungicide in the tree
Macro-Injection Advantages
Criteria for Successful Injections
• Reliable• Verifiable documentation of research results• Must increase survival of treated trees over natural
population• Safe• Economical• Reasonably easy to apply• Legal
• Native or adapted to the local environmental conditions
• Tolerant of temperature extremes, amount and pattern of precipitation, and local soil conditions
• Not invasive nor detrimental to the local environment
• Preferably multi-functional in the landscape
Tree Planting
Tree Planting
• Avoid planting monocultures
• Create diversity in the landscape
• Avoid wounding oaks during planting
Tree Planting
• Site• Season• Hole• Drainage• Pruning(?)• Foreign Materials• Depth• Backfill• Staking(?)• Mulch• Protection• Maintenance
Recommended Trees
American smoketree
Arizona walnut
baldcypress
bigtooth maple
bur oak
Carolina buckthorn
cedar elm
chinkapin oak
desert willow
escarpment cherry
Lacey oak
littleleaf leadtree
mescalbean
Mexican plum
pecan
possumhaw
TX or MX redbud
rusty blackhaw
Texas crabapple
Texas sophora
“The overall goal of the Texas A&M Forest Service’s Cooperative Oak Wilt Suppression Project is to minimize the spread of oak wilt
(Ceratocystis fagacearum) in central Texas.”
• Provide public awareness and education about the disease
• Identify and map mortality centers with ground verification of oak wilt
• Provide treatment recommendations and cost-shares (when applicable) to private landowners
• Conduct post-suppression evaluations on cost-shared treatments
• Establish and maintain detailed and accurate records
Oak Wilt Suppression Project
Cost Shares
Cost-shares, disbursed through the Oak Wilt Suppression Project, may be available to private landowners for the following efforts:
• Containment trenching around oak wilt centers
• Pushing or rouging of all oaks within the boundaries of cost-shared trenches
• Removal of diseased red oaks in urban areas
Cost-shares shall consist of 40% of actual costs not to exceed $2000.00 per individual per year with a maximum of $10,000.00
per project per year.
Cost Shares
• Complete containment of the disease center (natural land features and existing underground infrastructure can be used in select cases)
• Relative isolation of the disease center from other disease centers
• High potential for fungal mat formation (red oaks)
• Compliance with Cultural Resources Preservation Act
The following criteria are required to qualify for cost-shares:
Cost Shares
• Removal of dead trees
• Trenching around healthy stands of trees
• Secondary trenches
• Engineering charges, consulting fees, or permit fees
• Loss or reduction in revenues from the land
• Stump grinding
• Fungicide treatments (injection)
• Replanting or landscaping
Items NOT eligible for cost-shares include:
Cost Shares
• Cost-share Application
• Treatment Plan
• Cultural Resources Survey Form
• TARL Records Check
• Treatment Maps
• General Location Map
• Underground Utility Waiver
• Cultural Resources Acknowledgement Form
• W-9 Tax Identification Form
There is an application process:
Oak Wilt Resources
Oak Wilt Information Partnership website:
www.texasoakwilt.org
HOW TO Identify and Manage Oak Wilt in Texas brochure
Other Informational Websites
• http://texasforestservice.tamu.edu
• http://texastreeplanting.tamu.edu
• http://texasinvasives.org
• http://www.treesaregood.org
• http://www.texasconservation.org