Texans are rightfully anxious to prevent oak wilt after the February 2023 ice storm downed so many branches.
Oak wilt is caused by a fungus, Bretziella fagacerum, which disables an oak’s water conducting system. The fungus is spread by a sap-feeding beetle that is active from the beginning of February through the end of May. The beetle lands on the fungal mat on an infected red oak, picks up the fungus on its body, and then travels some distance to a healthy oak of any kind that has sap oozing from a fresh wound whether it was caused by ice-shattered branches or fresh man-made pruning cuts. Live oaks are particularly problematic because the fungus also spreads from an infected live oak to adjacent trees via interconnected roots — as fast as 100-150 feet per year. Thus, when one live oak in your area is infected, all of the neighboring trees are in grave danger.
So what should we do after the ice ravaged so many of our live oaks? Well, first take some comfort knowing that the jagged wounds created by the downed branches sealed themselves within a few days. And the weather stayed cold, so beetle activity was unlikely. That was then… But now that temperatures are warmer, the beetles are definitely waking up! So from now until June, prune only damaged parts of your trees — and only if they are a safety hazard. Then, immediately paint the wound thoroughly; any kind of latex paint will work.
Hold off any aesthetic pruning from now until after June 1, when it’s too hot for beetle activity. Better to live with an ugly stubble for a few months than risk the loss of your precious oaks and those of your neighbors. Learn more about oak wilt at texasoakwilt.org.
