Hundreds of thousands of ash trees in North Texas are under threat from a small and unassuming beetle: the emerald ash borer (EAB). The half-inch-long insect may look harmless, but anyone with an ash on their property should take action now to protect their trees.
The Garden has several dozen well-establish ash trees, and, unfortunately, EAB has been identified on site. Fortunately, a dedicated team of tree specialists have graciously donated their services and treatment to help preserve these trees.
Twenty four ash trees have received treatment from Bartlett Tree Experts, a leading provider of scientific tree care, and Rainbow Ecoscience, a tree health company that leads the industry nationwide in creating solutions for pests and disease.
The Garden is grateful for the help, says Seth Hamby, Director of Living Collections at FWBG. “The support we are receiving from Bartlett and Rainbow Ecoscience is invaluable,” says Hamby. “Their dedication to preserving our trees helps us maintain the beauty and health of the Garden for all visitors to enjoy.”
However, EAB continues to threaten ash trees across North Texas. What is the risk, and how can you protect your corner of the urban forest?
EAB 101
Adult EAB beetles (Agrilus planipennis Fairmaire) are metallic green and about 1/2 inch long. An invasive species native to Asia, EAB was first spotted in Michigan in 2002; the insects likely arrived in the U.S. on wood packing material.
The beetles aren’t harmful to humans, other animals or other plants. The beetles attack only ash trees, boring their way into the tree’s bark to lay their eggs. When these eggs hatch, the larvae feed on the inner bark and disrupt the tree’s ability to transport water and nutrients.
Is my tree an ash?
How to Identify an Ash Tree
(Video)
Without treatment, the tree cannot survive, and many die between two or five years after becoming infested. Tens of million of trees have already been lost across North America west of the Rockies.
Early identification and preventive measures are essential. Once a tree is fully infested, the available treatments can only slow its decline.
Four Steps for Saving Your Ash Trees
What should you do to protect your trees from EAB? Here are the essential steps:
Determine if you have ash trees on your property. The most common types of ash found in North Texas are the Arizona ash (Fraxinus velutina or Fraxinus berlandieria), the green/red ash (Fraxinus pennsylvanica) and the Texas ash (Fraxinus albicans Buckley or Fraxinus texensis). All of these trees share the following features:
- Compound leaves of an odd number leaflets, with one extending straight from the end.
- Tan to gray bark that grows in a distinctive diamond-shaped pattern.
- Seed pods shaped like paddles or teardrops.
Inspect your ash trees for EAB infestation. Look for the following signs:
- Dieback of the upper canopy of the tree.
- Splitting or shedding bark with insect trails underneat.
- Increased woodpecker activity. (Woodpeckers love these beetles and will frequent infested trees.)
- D-shaped holes in or under the bark.
Be aware of EAB activity in your area.
Unfortunately, it can be difficult to spot EAB infestation until the tree is severely damaged. Experts recommend anyone who is aware of EAB-affected trees within ten to 15 miles of their location to have their trees checked.
Since EAB beetles have been confirmed at the Garden, homeowners within 15 miles of our location should take action. (For reference, that would be a circle that reaches roughly as far as Saginaw to the north, Arlington to the east, Crowley to the south and Aledo to the west.) Residents of other areas can contact their local Texas A&M Agrilife Extension Office to ask about EAB activity in their area.
Discover your options. EAB infestations are difficult to treat, because the insects bore into the tree trunk. Two options are available for treatment: injection of insecticides into the tree trunk or into the soil surrounding the tree. Both require the help of experts, both to assess the tree and to provide treatment.
Soil applications, while shown to be effective, come with a level of uncertainty about how long the tree will remain unprotected as the insecticide is absorbed by the roots, explains Gareth Harrier, local manager for the Bartlett Tree Experts. Trunk injections are a more immediate solution.
The cost of treatment will vary based on multiple criteria including the method used, the size of the tree and the number of trees to be treated, but as of this writing usually runs between $15 to $20 per inch of diameter of the tree trunk. (You can learn how to measure your own trees with this guide.)
This treatment must be repeated every two years until the threat of EAB infestation is low enough to warrant leaving the tree unprotected. In the Midwest, where EAB first hit North America, that injection cycle has typically lasted between 6 and 12 years, depending on factors including the number of ash trees in the area and the level of mortality of untreated trees in the area.
This isn’t cheap, but untreated ash trees are very likely to become infested and die. Dead trees should be removed–leaving them poses a risk of the tree falling on people or property–and tree removal can be incredibly expensive. Small trees may only cost a few hundred dollars to remove, but large trees, especially those that require a crane to remove, will run many thousands.
The longer an infected tree has been standing the more expensive it is to remove, says Harrier, since the wood becomes extremely brittle and will break unpredictably. Many tree care companies cannot allow their workers to climb these trees.
“We encourage all homeowners with ash trees to take action to protect these valuable parts of the urban forest,” says Harrier. “The silver lining is that we can learn from the experience of ash owners and arborists in the Midwest and Northeast who have been dealing with EAB since the early 2000s. We encourage you to work with an ISA-certified arborist to devise a plan for the ash trees on your property.”
This isn’t the sort of cheerful plant information that we like to share with the friends of the Garden, but EAB is a real risk. Our horticulturists are closely monitoring the Garden’s ash trees. We encourage you to do the same for the trees on your property.
