Treating Oak Trees Isn't Hard At All

This past week I will have to call the Oak Wilt Week! On Tuesday, September 16 Rob Grotty with the Texas Forest Service and I did a program together on Tree Health and the Oak Wilt Fungus. Actually I talked on tree health and Rob, who is an expert in the oak wilt fungus, talked about oak wilt and how to treat it. We didn’t have many to attend the program but I don’t think that means that oak wilt isn’t a problem in our live oak and red oak trees.

On Wednesday, Christi Stromberg, the Williamson County Horticulturalist, and I along with some Williamson County Master Gardeners treated some live oaks near the County Courts building. Christi had noticed a few weeks ago that one of the live oaks in a row of 5 or 6 had lots of dead leaves and limbs. As she looked closer she saw the typical oak wilt symptoms in the leaves. She invited Rob Grotty over for another opinion and he also agreed that the tree was severely infected with the oak wilt fungus. Christi quickly contracted with a tree service to remove that tree to the ground and ordered the fungicide Alamo to treat the surrounding trees in hopes of stopping the spread. This is where the Master Gardeners and I stepped in to help with the Alamo injections.

Oak wilt is a devastating disease of live oaks and red oaks, the two predominant oaks in western Williamson County area and of the Hill Country in general. The oak wilt fungus lives in live trees and typically is spread from tree to tree by the common root system that they all share. It is not uncommon for live oaks to come up in motts sprouting from the roots of some mother tree located nearby and these motts in turn send out more sprouting roots forming more live oak motts. All this propagation makes for a beautiful Hill Country landscape but also allows a disease to spread very easily from tree to tree. Red oaks on the other hand don’t root sprout or form motts but they are very susceptible to the disease and they also have died by the thousands in the Hill Country.

As you drive around western Williamson County you see that most of the development has happened in these oak covered hills. It is beautiful scenery but with rapid movement of oak wilt through the trees homeowners can be left with nothing but stumps. Fortunately there are some treatments available but unfortunately they cost money and time. First you can trench trees. What this means is cutting a 5-6 foot trench to break the roots so that disease spread is stopped. This is not foolproof by any means but the Texas Forest Service has had an 80-90% success rate where they can trench. Of course you can’t trench a neighborhood so homeowners are left to treat trees to prevent the disease from killing trees.

Treating trees by injecting Alamo fungicide into the root system is very effective if you treat them before they are infected. I like to think of Alamo as a vaccination for the tree. It is much better to vaccinate than it is to treat the disease, in fact it is almost impossible to save a tree once infected.

Treating is easy. You simply dig out around the base of the tree exposing the root flares. We do this so that we can inject the fungicide easier and in more places than in the rough bark. Once we dig out some of these big roots we drill holes about 1 inch deep and insert a T into the hole. We join all the T’s together with plastic hoses and hook that to a pump-up sprayer full of Alamo and water. We use 20 ml of Alamo per liter of water per inch of trunk diameter. As soon as the tree takes up the mixture we cover the roots back up and move to the next one. The trees we injected last Wednesday took about an hour and a half per tree.

How much does it cost? Christi bought a kit that included the T’s, plastic tubing, pump-up sprayer, drill bit and the Alamo for about $275. This is enough Alamo for about 4 ten inch diameter trees. I believe the Alamo purchase alone is about $100 for one quart. Of course for those who say they don’t know how or can’t do this I say, “If I can do it anybody can!”