Oak Wilt in the San Antonio Area: Signs, Spread and Your Options

Oak wilt exhibits dramatically different visual symptoms depending on whether it infects red oaks or live oaks. Red oaks (Quercus buckleyi and Quercus shumardii) are exceptionally susceptible. When infected, a mature red oak typically suffers complete canopy wilting and bronze foliage collapse in as little as two to four weeks. Furthermore, infected red oaks produce sweet-smelling fungal spore mats under their bark during humid spring weather. These mats create pressure pads that crack the bark, releasing fungal scents that attract nitidulid sap beetles. Live oaks rarely produce spore mats; however, because live oaks grow in continuous stands with interconnected root grafts, the disease spreads through root systems at a rate of 75 to 150 feet per year, killing dozens of mature trees simultaneously.

While sap-feeding beetles initiate new infection pockets above ground, more than 80% of mature tree mortality across Bexar County occurs underground through interconnected root graft networks. Live oaks growing within 50 to 100 feet of one another naturally graft their lateral roots together, creating a shared communal circulatory system. When a single live oak in a neighborhood contracts oak wilt, the fungal spores travel directly into the root flare and flow through shared root grafts into adjacent healthy oaks. This creates expanding disease centers (trenches) that leave circular paths of dead timber across entire subdivisions in areas like Hollywood Park, Shavano Park, and Timberwood Park.

While there is no chemical cure for a live oak that has already lost more than 30% of its canopy to oak wilt, healthy companion oaks within the infection perimeter can be protected using Alamo (propiconazole) systemic fungicide macro-infusions. Our certified arborists drill micro-ports into the root flare of threatened live oaks below ground level, inserting low-pressure infusion tees. We inject pressurized volumes of Alamo solution directly into active sapwood rings. The fungicide circulates upward through the vascular system, inhibiting fungal cell wall development and providing up to 24 months of vascular defense against root-grafted fungal transmission.