Texas oak wilt season: Officials advise halting oak tree pruning through June

Oak tree leaves that have been infected with oak wilt. 

It’s that time of year again where local and state officials are reminding residents to hold off on pruning their oak trees through June to help prevent the spreading of a deadly tree disease.

Oak wilt is considered one of the most destructive tree diseases in the US and is killing oak trees in some parts of Texas at epidemic proportions, according to the Texas A&M Forest Service. Oak wilt is an infectious disease caused by a fungus, Bretziella fagacearum, that invades and disables the water-conducting system in oak trees.

“February through the end of June is oak wilt season in Texas,” Texas A&M Forest Service Staff Forester II Rachel McGregor, who covers the Parker County area, said. “If you are concerned you might have oak wilt, I recommend contacting an ISA oak wilt qualified arborist, your local Texas A&M Forest Service forester, me, or your local AgriLife Extension agent.”

All species of oak trees can be infected by the oak wilt fungus, but live oaks and red oaks are the most susceptible.

“Oak wilt is one of those diseases that can cause a lot of heartache and distress. In some situations homeowners have no other option than to just watch their oak trees die,” Parker County Extension Agent Jay Kingston said. “I have seen oak wilt in red oaks and live oaks in all portions of the county. If residents have infected red oaks, immediate disposal is recommended to help cut down the chance of spreading the fungus.”

In 2019, Texas counties with confirmed oak wilt included Parker, Palo Pinto, Tarrant, Hood, Johnson and Wise counties, as well as many other counties in Central and West Texas.

McGregor and Kingston provide some helpful tips to try and prevent the spread of the disease.

“Always paint wounds or pruning cuts on any oaks immediately,” McGregor said. “Do not transport firewood, and oak wilt-infected red oaks should be cut down and burned, buried or chipped up to prevent fungal mat formation.”

Kingston said one of the ways new oak wilt infection centers are created is through the transmission of the fungus from infected oaks. Red oaks never survive oak wilt and often die within four to six weeks following the initial appearance of symptoms. Symptoms to watch out for include the development of yellow veins that eventually turn brown on leaves; tip burn or margin burn, which turns the edges of the leaves brown; and the appearance of fungal mats in red oaks, which can be found by looking for inconspicuous narrow cracks in the bark that lead to hollow areas between the bark and wood.

“This exposure can occur in a number of ways including pruning cuts and injury from weed trimmers, mowers or vehicles,” Kingston said. “When the vascular system is exposed, sap-feeding beetles are attracted to your tree. These same beetles are also attracted to the fungal mats on infected red oaks.”

The beetle then carries the fungal spores to new trees above ground, while fungus can travel from tree to tree underground through interconnected roots, according to the forest service.

Most live oaks defoliate and die within three to six months following the initial appearance of symptoms, according to the Texas Oak Wilt organization, which has a recommended website for information about the disease.

McGregor said she can help residents by providing research-based information.

“I offer research-based information for Texas landowners to make proper decisions on their trees and related natural resources,” McGregor said. “I emphasize oak wilt awareness and the distribution of proper oak wilt information.”

Kingston said the best way he can also help by educating the public.

“The most important part of that education is pruning your trees at the proper time and in the proper manner,” Kingston said. “Be aware of the disease, its modes of transmission and what each person can do to help prevent the spread.”

For more information about oak wilt, visit texasoakwilt.org or the forest service website at tfsweb.tamu.edu

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