Oak Wilt vs. Hypoxylon Canker: Diagnosing Tyler's Sick Trees

In Smith County, our Oaks are our pride and joy. But when an Oak starts dropping leaves in July or the bark starts peeling, panic sets in.

Two major diseases threaten Tyler's oaks: Oak Wilt and Hypoxylon Canker. While they both kill trees, they behave very differently. Knowing the difference can save your other trees.

1. Hypoxylon Canker (The "Stress" Killer)

We see this everywhere in Tyler, especially after hot, dry summers.

• Cause: It is a fungus that is already on the tree. It activates when the tree is stressed (drought, root damage, construction).
• Visual Sign: The bark peels off in large sheets, revealing a smooth, silver/grey or black surface underneath.
• Contagious? No. It attacks weak trees. It does not "jump" to healthy neighbors easily.
• Treatment: None. Once you see the silver patch, the tree is dead structurally. It must be removed for safety.

2. Oak Wilt (The "Plague")

This is the one that keeps arborists awake at night.

• Cause: A fungus spread by sap-feeding beetles (nitidulids) or through connected root systems.
• Visual Sign: Leaves turn brown specifically along the veins (veinal necrosis) while the rest of the leaf stays green. The tree drops leaves rapidly, often in fully green condition.
• Contagious? YES, HIGHLY. It spreads through root grafts underground. If one tree gets it, it can kill every Red Oak on your block within weeks.
• Treatment: Expensive fungicide injections (Alamo) can save white oaks, but red oaks usually die too fast. Trenching is required to stop the root spread.

The "Thumb Rule" for Tyler

• Bark falling off + Silver patch? = Hypoxylon. (Remove the tree, water your other trees).
• Brown leaf veins + Rapid leaf drop in Spring? = Oak Wilt. (Call a pro IMMEDIATELY to trench and isolate).

Prevention is Key

1. Stop Pruning in Spring: Never prune Oaks from February to June. This is when the sap beetles are active. Fresh cuts attract them.
2. Paint Cuts: If you must prune (or if a storm breaks a branch), paint the wound immediately with pruning sealer or latex paint.
3. Water Deeply: Both diseases thrive on stressed trees. Deep watering during our August droughts is your best defense.

Not Sure Which One It Is? Don't guess. If it's Oak Wilt, your neighbors are at risk. Call us for a diagnostic visit.

Schedule a Diagnosis