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Tuesday - May 04, 2010

From: San Antonio, TX
Region: Southwest
Topic: Trees
Title: What to do with ailing live oak trees
Answered by: Nan Hampton and Eric Beckers

QUESTION:

We live in far north San Antonio, TX on a 2 acre lot with many trees.. about 25% oak and 75% cedar. About 15% of our live oak trees have not sprouted leaves yet this spring, or have only sprouted leaves on the lower part of the tree trunk where the canopy begins. These same trees have also lost large chunks of bark, some areas as large as 20" x 7". We would love to get rid of many of the water hogging cedars so the oaks can thrive, but are afraid to remove too many of them in case we get hit with oak wilt (a cedar tree is better than no tree at all). Do you think this damage Is a result of stress on the trees from last years record drought? What should we do to help these trees survive? Should we paint the areas that have lost bark or cut them away? Any help would be appreciated. Thank you.

ANSWER:

Mr. Smarty Plants contacted Eric Beckers form the Texas Forest Service about this question. Here is what he said:

"We're hearing this over and over again and we'll probably hear about it throughout the new year. After being stressed by the drought many of our oaks were further damaged by Hypoxylon and borers. As soon as you hear someone say the bark has fallen off, you can bet that their drought stressed tree has hypoxylon cankers (first brown and powdery, and then a silvery crust) and the prognosis is not good."

Go to the TAMU AgriLife Extension Plant Pathology page to find three fact sheets about hypoxylon: Hypoxylon Fact Sheet #1, Hypoxylon Fact Sheet #2, and Hypoxylon Fact Sheet #3.

Since you live in San Antonio, your trees aren't likely to be affected by oak wilt. Eric continued:

"If you live in the areas north of a Wimberley to Kyle line then there is the chance that oak wilt could be at play as well. Trees damaged by oak wilt can also display hypoxylon cankers, so then we look for the pattern of mortality, groups of oaks dying side by side, and the brown vein leaves. Drought mortality accompanied by hypoxylon cankers usually occurs on one or two oaks over here and another two or three over there—the sick trees are scattered about with healthy ones in between."

However, you should visit the Texas Oak Wilt site to familiarize yourself with the symptoms, prevention and treatment of the disease.