When to Prune Trees to Protect from Oak Wilt

Live Oaks can get Oak Wilt by way of root transmission from another Live Oak or from Nitidulide beetles. This insect would first have to have fed from a tree with an infected fungal mat. A fungal spore can stick to them and be carried to the next tree that the insect feeds on. Red Oaks are the most common tree to produce that infected fungal mat. Insect transmission does not occur from Live Oak to Live Oak as Live Oaks are can’t produce the infected fungal mat and fungal spore. When Oak Wilt travels through the grafted root system of Live Oaks, it is at a rate of about 75 feet per year, though spread at a rate of 150 feet per year has been documented.

Spanish/Red Oaks usually get Oak Wilt through insect transfer. Spanish/Red Oaks don’t develop grafted root systems. Spanish/Red Oaks are one of the few trees known to produce that infected fungal mat and fungal spore that can be transported through sap feeding beetles. That infected fungal mat most commonly forms in mild temperatures for the first year following the trees death from Oak Wilt. Spanish/Red Oaks can’t be save once they’ve gotten the disease and should be removed immediately once infected.

Most Oaks develop mechanical problems which cause self inflicted wounding. This includes interlocking limbs, branches rubbing on roofs, and trees growing up into and through the crown of susceptible Oaks. This type of abrasive wounding will never heal, and will drip sap year round. The flow will be heaviest during peak insect and fungal mat formation periods. All pruning cuts made by man, even large or incompetent cuts, will stop flowing sap within a couple of hours. If these wounds are properly treated with pruning paint, there will be no sap flow at all and the wound will be unattractive to insects and are less likely to be infected by insects.

Trees that need to be pruned, should be pruned, by a professional Arborist, as soon as possible. This will significantly reduce the possibility of Oak Wilt infection by insect vector.

When pruning trees susceptible to insect transmission of any disease a non-phytotoxic wound sealer should be used.