Oak Wilt Identification Management Mark Duff Certified Forester

… Oak Wilt: Identification & Management …. Mark Duff Certified Forester, Board Certified Master Arborist 1

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.

The Impact of Oak Wilt Oak wilt may reduce urban and suburban property values by 15 -20%.

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

Where is Oak Wilt?

Where is Oak Wilt?

Where is Oak Wilt?

What Trees Are Susceptible? All Oaks and other members of the Beech family (Fagaceae) 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. 9

How Is Oak Wilt Spread? 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. Sap Beetle Fungal Mat Fresh Wound on Oak

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. Rate of spread averages 50 feet to 75 feet per year. Root Grafts Live Oak Mott 11

How Is Oak Wilt Spread?

Diagnosis in a Population of Trees Live Oak Center Red Oak Center

Diagnosis in Individual Live Oaks • • • Rapid defoliation Death in 3 to 6 months Spread to adjacent trees No fungal mat formation ~ 5 - 15% survival rate

Diagnosis in Individual Red 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)

Foliar Symptoms in Live Oaks Tip burn / Marginal necrosis Veinal chlorosis / necrosis

Foliar Symptoms in Red Oaks Bronzing or water soaking

Presence of Fungal Mats • 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

Taking Samples • Bole (preferred) or branch samples • Confirms presence of pathogen

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: Prevention Planting Fungicide Injection Trenching These measures will not cure oak wilt but can significantly reduce tree losses.

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 Diseased Healthy 100 ’ 100’ minimum 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.

Trenching Soil depth and texture will determine equipment choice.

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 macroinjections of Alamo® have been scientifically proven effective and continue to be the industry standard.

Macro-Injection Advantages • 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

“Alternative” Products and Methods Tebuject

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

Tree Planting • 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 • 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

Tree Planting

Recommended Trees American smoketree Lacey oak Arizona walnut littleleaf leadtree baldcypress mescalbean bigtooth maple Mexican plum bur oak pecan Carolina buckthorn possumhaw cedar elm TX or MX redbud chinkapin oak rusty blackhaw desert willow Texas crabapple escarpment cherry Texas sophora

Oak Wilt Suppression Project “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

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 costshared 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 The following criteria are required to qualify for 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

Cost Shares Items NOT eligible for cost-shares include: • 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

Cost Shares There is an application process: • 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

Oak Wilt Resources Texas A&M Forest Service Central Texas Regions

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

Questions?

Thank You! Texas A&M Forest Service