Michele Rawleigh
For many, 2021 was a rough year. That was also the case for the Denton area’s ash trees. The extended freeze during Winter Storm Uri in February 2021 caused considerable damage or outright killed several trees, including ashes. Furthermore, ashes are now also battling a killer beetle, the emerald ash borer. This 1-2 punch may be more than an ash tree or your wallet can bear.
Freeze damage, EAB infestation, or both?
Some symptoms of freeze damage and emerald ash borer (EAB) infestation are similar. Epicormic sprouting is common to both conditions. Epicormic sprouts are those leafy shoots that emerge directly from the tree trunk rather than at the tips of branches. Epicormic sprouts indicate significant damage to the vascular system under the bark.
Splitting bark is another symptom of both freeze damage and EAB. The freeze/thaw cycle creates fissures in the bark from expansion and contraction. The EAB larvae chew extensive serpentine tunnels that horizontally crisscross the tree’s vascular system interrupting the flow of water and nutrients. As the vascular tissue is consumed, the bark separates from the tree. Splitting or missing bark due to an EAB infestation will typically expose the characteristic S-shaped tunnels underneath and contain the D-shaped exit holes where the mature larvae emerged as adult beetles.
Additional symptoms of an infested ash tree may include woodpecker activity and thinning of the tree’s canopy. Where freeze damage usually causes a dramatic, sudden dieback of major limbs, the presence of emerald ash borer generally causes a more subtle loss over time usually starting in the upper canopy.
Can the ashes be saved?
The answer was “No” for a huge ash adjacent to Denton City Hall. Sadly, it was a victim of Uri, and considering its location and proximity to pedestrians and the building it was removed, according to Haywood Morgan, Denton’s Urban Forester. Dead limbs on ash trees in particular are very brittle and can be a major safety hazard to people and property when they break.
Homeowners should be monitoring their ashes as they leaf out this spring. If a tree still has less than 50% to 60% of its pre-Uri canopy, it should be evaluated for removal. It might survive, but the confirmed presence of EAB in several Denton neighborhoods means you might only be delaying the inevitable.
For healthy ash trees worth saving, there are several preventive treatment options for emerald ash borer. They consist primarily of insecticide injections into individual ash trees or into the surrounding soil to be absorbed by the tree. However, the treatments need to be repeated frequently, annually to every two or three years depending on the method. Consider though, that it is generally more cost effective to treat healthy, mature ash trees than to remove and replace them.
Questions?
Denton residents with questions or concerns can contact Haywood Morgan at 940-349-8337 or [email protected]. Additional information is available from Texas A & M Forest Service at tfsweb.tamu.edu/eab or tfsweb.tamu.edu/afterthestorm/canmytreebesaved, or the Emerald Ash Borer Information Network at www.emeraldashborer.info.
Michele Rawleigh is a Denton County Master Gardener, Texas Master Naturalist, and Certified Citizen Forester.