Critical Timing of Oak Pruning

Oak wilt is an extremely serious fungal disease that attacks red oaks and live oaks across significant parts of our state. Because oaks are such important trees to Texas landscapes, we should call attention to one of the prime ways that it’s spread: through improper pruning practices.

Photo: Landscape crew was finishing up oak pruning in McKinney (DFW area) earlier this week.

Timing of pruning…
Pruning must be done when the fungus is inactive. Initially pathologists and professional arborists told us that we should prune between Thanksgiving and Valentine’s Day – a rather unusual way of measuring time.

Later that was expanded to say that we could prune once the fungal mats became inactive in mid-summer’s really hot weather and all the way through fall and winter.

So now we could say that the safest time to prune oaks would begin in mid-July and extend through mid-February (early February in South Texas), and the time to avoid would be just the inverse: mid-February (early February in South Texas) through mid-July.

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Additional tips to help prevent spread of oak wilt…
If you have a work crew coming in to do the pruning for you, ask that they disinfect their saws before they start work on your trees. Check their credentials to see that they’re well versed in coping with active oak wilt should they encounter it.

All cuts made to oaks, even those made when the fungus is inactive, should be sealed with pruning paint to prevent entry of oak wilt into the exposed surfaces.

The Texas Oak Wilt Partnership is a collaborative project between the Texas Forest Service of Texas A&M, the U.S. Department of Agriculture Forest Health Protection Division and the Lady Bird Johnson Wildflower Center. Here is the organization’s outstanding website.

Posted by Neil Sperry
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