Punxsutawney Phil may have predicted six more weeks of winter, but here in Texas, February means it’s time to start preparations for spring gardening.
One thing you’ll want to leave off your landscaping to-do list, at least for a while, is pruning your oak trees. February marks the beginning of oak wilt season – a disease that can bring down even the mightiest of oak trees.
Demian Gomez, regional forest health coordinator with the Texas A&M Forest Service, spoke with the Texas Standard’s Laura Rice about what the disease is and how to keep your trees safe.
This transcript has been edited lightly for clarity:
Texas Standard: What exactly is oak wilt? How does it affect trees?
Demian Gomez: So oak wilt is a deadly tree disease that has affected millions of trees across more than 75 counties in Texas, but also found across the northeastern United States as well.
It’s a fungus called Bretziella fagacearum, which is what we call a vascular pathogen. That means that this fungus gets inside the water conducting vessels – that means that the vascular system – and blocks the water in the tree, and the tree ends up dying because of the fungus blocking all this system.
And it’s not only the fact that trees die. It also causes a lot of economic impacts, because it can reduce the property values by 15%-20% in some cases.
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Absolutely. Big, beautiful oak trees just dying – it sounds terrible. I know it can spread in a couple of ways: through root systems, or maybe even if you’re not careful, the tools you’re using. But is the insect involved in the process what’s especially concerning this time of year?
Yeah. So what happens is when a red oak is killed by oak wilt, it sometimes create a destructor called fungal mat. And sap beetles are really attracted to this because fungal mats have a very fruity odor.
So they smell really interesting for these beetles, and they would feed and reproduce in these structures. And then they’re going to go and fly to any type of wound in an oak tree, right.
So when we prune an oak tree this time of the year, the insects can actually bring the spores to the tree and therefore infect it. And this happens more commonly from February to June. And that’s why it’s important not to prune or wound any type of oak tree until this season in June finishes.
If we do – and you know, sometimes we have to prune because something else is going on – we always recommend, regardless of the time of the year, we want to paint those pruning cuts immediately after we make the cut.
You mentioned red oaks. Are red oaks especially vulnerable? Is there sort of a hierarchy of which oak trees are at risk the most?
Yes. So red oaks are the most susceptible. That means that they are going to get infected and they’re going to die probably after a month of them showing symptoms. And that typically means that, you know, leaves are going to turn red or brown in a time of the year which is not the fall. Those are the more susceptible.
Then we have, in an intermediate susceptibility, we have the live oaks. They die after around six months. And the problem with them is that they can spread the disease very easily throughout their interconnected root systems.
And then we have the white oaks that are the least susceptible, but they are not immune to infection. They get oak wilt, in most cases they can also die as well.
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So if you identify oak wilt in your neighborhood, or maybe you think your tree has it, are expensive treatments worth it? Do they work?
Yeah. So there’s many different approaches to managing oak wilt. Of course, we are talking about prevention in terms of not pruning from February through June. We’re talking about painting after every cut, regardless of the season.
We also want to focus on things like planting diverse tree species, because if we only have live oaks in the landscape, that increases the risk of our whole neighborhood having oak wilt.
But once we have a tree with oak wilt, there are a few things that we can do. If we are more like in a rural environment, we can think about something called trenching: That basically is severing the root connections between the trees, so that way we avoid this pathogen to move through the root system.
But mostly if we’re talking about an urban landscape, the way to go is typically protecting that with a fungicide, which basically means you inject a fungicide in the base of the tree, and that tree is going to be protected for a few years.
