Rapidly declining post oaks

Rapidly declining post oaks
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EAST TEXAS - I’ve been getting a number of calls in the past few weeks about oak trees “suddenly” up and shedding leaves, looking as though they were about to die. I’ve been called from all parts of Angelina County, both urban and rural.

In near all cases, the post oaks had appeared perfectly healthy until the abundant rainfall we’ve been having for months dried up and we returned to a normal-dry type of summer.

A wonderful publication about this problem was shared with me from our new district forester, Jordan “Jordy” Herrin, with the Texas Forest Service. He comes to Angelina County from Walker County, Huntsville, Texas with over 10 years’ experience working with Texas forest landowners. He helped me better understand the issues we are facing with these post oaks and their swift deterioration.

Jordy shared with me a very helpful publication, Rapid Decline of Post Oaks in Texas EPLP-033. This four-page publication explains a lot of the factors that cause can several problems with one of our most common oak trees.

Post oaks are a tough tree if left alone. They are slow-growing trees that can live in dry, poor soils, and are resistant to rot, fire, and drought. The most common reason they perish is from mechanical damage to the roots caused by construction. I’ve seen too many perish from folks wanting to build right next to them. Left alone in their natural environment, they do quite well but when we chop up or disrupt their roots with underground utility lines or foundation work, they don’t last long at all.

Clients often call in with reports of severe insect infestations eating the leaves or galls, cankers and leaf blisters that may disfigure the trees, but these very rarely cause any real harm.

Some years ago, we saw a huge outbreak of Hypoxylon Canker. Huge slabs of bark falling off the tree were often the tell-tale sign and death was imminent. That’s not the signs I’m seeing.

But recently we’ve seen a number shed their leaves from disease brought about by varying extremes (drought and drowning) that has made them very susceptible to common disease issues they could normally fend off.

One resident on Pahal Rd, south of the Bald Hill Community, showed me his trees that had cracks running down the length of the truck – sometimes several “cracks” running from the ground up into the branches. According to Mr. Herrin, some trees had so much water and grew so fast that they literally saw too much growth. He had seen it in some trees at his residence in Walker County or he wouldn’t have believed it.

What we are seeing is the weakening of trees from the exhaustion of stored carbohydrates in the roots. Recent drought then drowning weather patterns reduce a post oaks ability to fight off the lesser diseases that may come along.

The technical name for all is this is “rapid decline”.

So what can we do? Pamper your trees. Water deeply then infrequently when we get dry. The type of watering you may do for your lawn isn’t nearly as deeply applied as what a large oak needs. I like to put my water hose on the ground and let the water barely dribble out, slow enough to where it doesn’t run across the ground, but is able to soak in. Then I leave that hose running at that incredibly slow rate overnight!

Please do not disturb the soil under the drip line of the trees. You can mulch selectively to reduce vegetative competition around the trees and hold moisture in the soil.

Do not pile up mulch around the tree trunk. Do not give it sudden shot of fertilizer.

Caring for post oaks means removing all stressors and providing ample water when we get dry. If you have leaves that have fallen off a tree, I suggest you wait until spring to see if it leafs-out before you rev up the chain saw.

Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu.