The Calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Trim | No | No | No | No | No | Trim | Trim | Trim | Trim | Trim | Trim |
The Texas A&M Forest Service advises against pruning oaks from February 1 through June 30. That's when fungal mats form on infected red oaks and the small sap beetles that visit them are most active. A fresh cut leaks sap, the beetles come to it, and if they've been on a mat, they bring the spores along.
July through January is the working window. Many people prefer the coldest weeks of winter. Whatever the month, every wound on an oak gets painted right away with latex or a wound dressing. Month-by-month details.
Oak trimming books up in the safe months.
Call (877) 674-2213Please stay on the line while your call connects.How Oak Wilt Spreads
Above ground, through beetles carrying spores from a mat to a fresh wound. This is why timing and paint matter.
Below ground, through connected roots. Live oaks especially grow in groups that share root systems. According to the Texas A&M Forest Service, the fungus travels an average of about 75 feet a year through those roots, and this kind of spread causes most of the losses in Central Texas.
In firewood, when unseasoned wood from a red oak that died of oak wilt is moved and stacked somewhere new.
The fungus is called Bretziella fagacearum. There's no cure. Prevention and containment are the tools.
Live Oaks and Red Oaks Behave Differently
| Compare | Live oak | Texas red oak, Spanish oak, shumard oak |
|---|---|---|
| How infection looks | Leaves with yellow or brown veins; trees dying in a slowly widening group | Whole crown turns brown or red over a few weeks, usually late spring or summer |
| Speed | Months to a year or more; some survive with thin crowns | Fast, often 2 to 3 weeks |
| Spore mats | Rarely | Yes, under the bark of recently dead trees |
| Main risk to neighbors | Root connections | Beetles from the mats, plus firewood |
Post oaks and other white oaks are the least susceptible, but still get the same trimming calendar and paint.
If You Suspect Oak Wilt
- Don't trim or cut into the tree while you figure it out, especially February through June.
- Look at the leaves. Live oak leaves with yellow or brown veins, or a red oak browning out fast, are reasons to get it checked.
- Get a diagnosis. The Texas A&M Forest Service has foresters who help landowners confirm oak wilt, and its Find My Forester tool lists who covers your county. Most of San Marcos is in Hays County.
- Handle a dead red oak correctly. The Forest Service advises that recently dead red oaks suspected of oak wilt be destroyed by burning, burying or chipping. Don't keep the wood as firewood. A crew can take it down and chip it.
- Ask about containment. Trenching to cut root connections, and removing infected red oaks, are the standard suppression steps. The Texas Oak Wilt Suppression Program offers cost-share to qualifying landowners who work with Forest Service staff on a plan.
Oak Trimming the Right Way
- Scheduled July through January unless there's storm damage
- Tools cleaned between trees, especially going from a dead or suspect oak to a healthy one
- Cuts made just outside the branch collar, never flush
- Every wound painted the same day
- Live oaks raised and thinned lightly, not stripped; heavy interior thinning stresses them in summer heat
- Ball moss reduced by opening the canopy, not by stripping branches
Oak Health Treatments
Beyond trimming, some oaks benefit from treatments recommended after someone looks at them: improving the soil and mulch around a tree stressed by construction or drought, or preventive fungicide injections for high-value live oaks in an area where oak wilt is active. Ask about these on the call; whether they make sense depends on the tree and the site.
Oak Questions
My live oak is losing lots of leaves in March. Is that oak wilt?
Most likely it's normal. Live oaks drop old leaves in early spring as new ones come in. Leaves with discolored veins, or heavy leaf loss in summer, are the warning signs. Spring leaf drop or oak wilt?
A storm broke my oak limb in April. Do I wait until July?
No. Storm damage gets cut cleanly and painted right away. The waiting rule is for routine trimming.
Can oak wilt be cured with an injection?
No cure exists. Fungicide injections can help protect some uninfected or lightly infected live oaks, but they don't clear the disease from a tree that's dying.