Hypoxylon canker is a fungus that mostly targets trees already under stress, and after a hot San Antonio summer, that describes a lot of live oaks right now. It's one of the sneakier tree problems because it develops inside the wood before it's obvious from the outside.
The clearest sign is bark that starts sloughing off in patches, revealing a silvery or olive-colored fungal layer underneath. By the time that's visible, the wood underneath is often already significantly weakened, which is a real concern for a tree near a house, driveway, or power line.
Because it usually takes hold in trees already stressed by drought, heat, or root damage, prevention comes down to keeping a tree as healthy as possible. That means proper watering, avoiding root zone damage, and having stressed trees checked before symptoms become obvious.
Do you have a live oak that's looked stressed or thin in the canopy this summer?
#SanAntonio
Close-up photo of bark sloughing off to reveal the fungal layer underneath, from a real hypoxylon canker case if available, paired with a wider shot of the affected tree.
Canva text suggestion: "Is Your Live Oak at Risk?" or "What Hypoxylon Canker Looks Like"