Oak wilt treatment is priced by the size of the tree.
There is no flat rate, and any honest arborist will tell you the same. The cost tracks the trunk's diameter and the amount of shared root that has to be cut, because a bigger oak needs more fungicide and more work to protect. Here is how the cost is actually decided in Austin and the Hill Country.
The dose follows the wood.
Fungicide treatment is not a spray. The protectant, propiconazole, is injected directly into the base of the tree, and the amount it needs is measured against the trunk's diameter at breast height, what arborists call DBH. A slender oak takes a small dose and a handful of injection points. A wide, mature live oak takes several times the product and many more points around the flare. That is why two trees in the same yard can be quoted very differently.
Trenching follows the same logic from a different angle. The price reflects how much grafted root has to be severed to get ahead of the infection, so a long root front between large trees costs more to cut than a short run between small ones. In both cases, the size of what you are protecting drives the number.
Big tree, bigger dose, higher cost. The price is honest because the work is proportional to the tree.
The work behind a quote.
Every oak wilt job is a different mix of these. What your property needs depends on how many oaks are involved, how their roots are connected, and how far the disease has already moved.
On-site evaluation
It starts here, at no charge for a suspected case. I walk the property, read the canopy and the pattern of decline, and tell you straight whether your oaks need urgent action.
Certified lab confirmation
Oak wilt is a reportable Texas disease and is easily confused with look-alikes, so a suspected case is confirmed by a certified laboratory and routed to the Texas Plant Disease Diagnostic Lab before any treatment.
Fungicide injection
Preventive propiconazole protects healthy, high-value live oaks in the path of the disease. The amount a tree needs is measured against its trunk diameter, so a larger oak is more involved than a small one. Protection lasts two to three years, then it is renewed.
Trenching
The only way to stop the underground spread between live oaks is to sever the grafted roots with a deep trench ahead of the infection front. The work scales with how much root has to be cut and how reachable it is.
Removal of infected trees
Dead red oaks should come down and be handled correctly so they cannot grow the spore mats that start new infections. This varies with the size, height, and access of the tree.
An honest number needs eyes on the tree.
No two yards are the same. The size and number of your oaks, how their roots are connected, how far the disease has moved, and how reachable the work is all change what the right plan costs. A flat price posted on a web page would either overcharge the simple jobs or under-quote the serious ones, and neither is honest.
So the quote comes after I have seen the trees, not before. Be cautious of anyone who gives you a firm oak wilt price over the phone without looking, because the plan should be built around your property, not a price sheet.
The evaluation is free. You get a straight assessment and a real number for your trees, with no guesswork and no pressure.
Five things that change the quote.
Trunk diameter
The single biggest factor for injection. More inches of DBH means more fungicide and more injection points, in direct proportion.
How many trees
Protecting a stand of connected live oaks costs more than one tree, but per-tree pricing usually improves when several are treated in the same visit.
How far it has spread
Caught early, a property may need only injection. Once a center is established, trenching enters the picture and the scope grows.
Access and terrain
A rock saw needs room to work. Tight lots, slopes, fences, and utilities all affect how trenching is priced.
Whether removal is needed
Dead red oaks should come down and be handled correctly so they cannot grow the spore mats that start new infections.
Cost questions.
Why is oak wilt treatment priced by the size of the tree?
Because the dose follows the wood. Fungicide injection is measured against the trunk's diameter, so a bigger tree needs more product and more injection points, which costs more. Trenching is priced by how much shared root has to be cut. The bigger the tree and the longer the root front, the higher the price.
Is the fungicide injection a one-time cost?
No. Preventive propiconazole injection protects a healthy live oak for about two to three years, then it is re-applied. It is ongoing protection for a high-value tree, not a one-time cure, and it cannot save a tree that is already heavily infected or past roughly a third of canopy loss.
Do you charge for the on-site evaluation?
The initial on-site evaluation for a suspected oak wilt case is complimentary. Because oak wilt is a reportable Texas disease, a confirmed diagnosis may also involve a certified laboratory fee, which is a modest pass-through cost charged by the state diagnostic lab, not by me.
Is it cheaper to just remove the tree?
Rarely, once you account for the whole yard. Removing one infected oak does not stop the fungus from moving through grafted roots to your other oaks, and a mature live oak is worth far more standing than the cost of protecting it. The cheapest outcome is usually catching it early and containing it, not removing trees one at a time as they fall.
A free evaluation beats a guess.
Send a few details or call directly, and you will get an honest, on-site assessment and a real quote for your trees, not a ballpark off a web page.