Oak Wilt and other Tree Calamities
Currently, we are losing lots of trees throughout the county.
There are many culprits, but Oak Wilt tops the list. Oak Wilt has been an issue for many years but seems to really spread in its coverage following natural disasters like drought and extremely cold winters. Oak Wilt is a fungal disease and is more active during or following periods of increased moisture. Should we get into the promised El Nino spell that will bring us above average moisture, I expect to see Oak Wilt begin to spread rapidly. We have already seen an increase this spring with the limited rainfall we have received.
Oak Wilt is an infectious fungal disease that invades and disables the water conducting system in susceptible oaks. Red oaks are more susceptible than other oak trees and seldom survive an Oak Wilt infection- typically, red oaks will die in 3 to 4 weeks following infection. Live oaks are in the white oak family, but due to their vast interconnected root system that allows the fungus to move from one tree to another, they are very seriously affected by Oak Wilt. Live oaks life expectance and infections rate can vary widely from tree to tree. Some trees will linger for years and others may not show any symptoms while trees around them are dying.
Live oaks are considered the stateliest tree in central Texas and most folks want to do all they can to protect them, especially around their homes. Treatment and preventative options are limited but can be effective. Trenching to prevent transmission of the pathogen from infected trees and groves to uninfected ones can help keep the disease from spreading. Trenching with a trenching machine or rock saw at least 4’ deep will aid in preventing root transmission.
Injections of the fungicide propiconazole on high value trees can help prevent losses and extend the life of the tree.
Another disease that thrives on stressed trees is Hypoxylon Canker. Hypoxylon Canker is also a fungus that occurs in trees that have been subjected to stress conditions. This stress can be the result of a drought, oak wilt, insect damage, damage to trunk or roots, or just about any type of stress. Hypoxylon Canker is most common in oaks but will attack other tree species as well. Research has shown that the fungus is present in most healthy trees but may not actually become active until the tree is stressed.
As if Mother Nature does not provide enough stress to our trees, we are often our own worst enemy.
Avoid using herbicides that may have soil movement around your favorite trees. When possible, avoid deep soil disturbance and root damage, this can be especially stressful to trees during drought conditions. We all know that too little water is hard on your trees, but too much water can hurt your trees as well and can be especially harmful to certain species like post oaks. One of the quickest ways to end the life of a centuries old post oak is to build a home near it and try to start pampering it, it has lived this long through every imaginable weather extreme and natural condition, just let it be.
Mother Nature has, however, dealt some serious blows to our tree population in the last few years. Many of our trees are stressed from the ongoing extreme drought that was at its worst last summer. We have also had some unprecedented cold spells in the last 3 years that have knocked back and killed many varieties of trees. You combine just the drought and cold spells, and it is a wonder we have any trees left. These natural and the man-inflicted stressors make trees more susceptible to any potential diseases. Most naturally occurring stress is unavoidable, but man-caused stress should be avoided as much as possible. During drought, supplemental watering for yard trees is recommended. Aeration, composting, and mulching under trees will help keep them healthy, but may be difficult in yard areas with turf. I highly recommend planting varieties of known drought hardiness and disease resistance in your landscape. Here are three of my favorites for Comanche County: Chinkapin oak, Burr oak, or Chinese Pistache. A couple of smaller hardy selections would be Basham’s Party Pink Crape myrtle or most any Crape myrtle, and Texas Vitex; there are others that will also do well, but these always come to the top of the list for hardiness and disease resistance for me. Just remember, trees do live a very long time, but even they have an expiration date.