FOREST HEALTH: EMERALD ASH BORER
The emerald ash borer (Agrilus planipennis) is a destructive, invasive wood‐boring pest of ash trees (Fraxinus spp.). Native to eastern Asia, the emerald ash borer (EAB) was unknown in North America until 2002, when it was discovered in Detroit. Since then, EAB has spread to 36 states including Texas, where it was first detected in Harrison County in 2016.
EAB is responsible for killing millions of ash trees across the country. Ash trees are widespread in the United States and all 16 native ash species are susceptible to attack. Ash trees with low population densities of EAB often have few or no external symptoms of infestation.
Current Situation
EAB was first detected in Texas in April 2016 when four adult beetles were caught and confirmed in a monitoring trap in Harrison County, just south of Karnack. We began monitoring for the pest in 2009 by strategically deploying detection traps each spring. These traps are monitored throughout the spring and summer months to capture EAB emergence and track movement.
As of August 2024, EAB has been detected in 27 Texas counties:
- Bosque
- Bowie
- Camp
- Cass
- Collin
- Cooke
- Dallas
- Denton
- Ellis
- Franklin
- Grayson
- Harrison
- Hill
- Hood
- Hopkins
- Johnson
- Lamar
- Marion
- McLennan
- Morris
- Palo Pinto
- Parker
- Red River
- Rusk
- Tarrant
- Titus
- Wise
EAB will undoubtedly continue to spread in and around these areas, and it is possible that new detections will be made in other counties. We will continue to monitor the movement of EAB through our trapping program and will remain vigilant in evaluating further EAB sightings across Texas.
Hotline to Report EAB: (866) 322-4512.
EAB Known Infested Counties Map (USDA-APHIS)
What are ash trees, and why are they so important?
There are five species of native ash trees in Texas, these are: Berlandier, Green, Rio Grande, Texas, and White.
Ash trees make up a massive population of urban forests. In Dallas, for example, they account for over 5% of the city’s canopy cover.
Ash trees are important to our environment and our economy. They help fill the forest canopy and provide shade for the forest floor as well as keeping our ecosystems diverse and stable. Not to mention, nearly 100 species of insects rely on ash trees to survive.
They provide shade—cooling our streets and homes, keep the air clean and water pure, maintain soil quality, manage storm water runoff and beautify the places we live, work and play, granting them additional value.
Ash trees also provide us with a variety of different products.
White ash wood has a variety of unique qualities, being both pliable and strong but still lightweight. Many products are made from white ash wood, such as baseball bats, hockey sticks, guitars, boat oars, flooring, and furniture. White ash also provides food for some wildlife—such as cardinals, finches, and wood ducks. The black ash wood is not as strong as white ash, but it has a pleasing grainy look that makes it a great choice for furniture. Young black ash wood is also pliable enough to be split and used for cabinet making.
How can I tell if my ash tree is displaying signs of EAB activity?
Seeing EAB adults near an ash tree is a tell-tale sign it may be infected. EAB adults are dark green, one-half inch in length and one-eighth inch wide. They fly between May and June, depending on climatic conditions. You should also note that ash trees within the early stages of attack often have few or no external symptoms of EAB infestation.
Symptoms of an infestation may include any or all of the following:
- dead branches near the top of a tree
- leafy shoots sprouting from the trunk
- bark splits exposing s-shaped larval galleries
- extensive woodpecker activity
- D‐shaped exit holes
To report any symptomatic ash trees, please contact your local Texas A&M Forest Service office or call the EAB hotline at 1-866-322-4512.
How do you help manage EAB?
Plant Diversly
The first step to stopping EAB starts at the planting stage. When planting trees, either to replace those lost because of EAB or simply to add new trees to the landscape. Planting a diverse array of species is one of the best ways to prevent significant losses in the future. A general guideline to follow is known as the 10-20-30 rule. This simple rule of thumb suggests that a tree population should include no more than 10% of any one species, 20% of any one genus, or 30% of any one family. For example, if you plant 10 trees, two of them can be different types of ash tree, maybe one Red and one Berlandier, and then the rest need to be other types of trees, such as birch, mesquite, hickory, oak and so on. Having a greater diversity of trees reduces the likelihood that they will be severely affected by an outbreak of any single pest or pathogen.
For information and guidance on tree planting visit the Texas Tree Planting Guide.
If you have ash trees on your property, then you have some decisions to make. The first choice is whether, or not, the tree is important enough to save. If it’s a tree that provides shade to your sunporch or if it was planted in memory of a loved one, the answer may be ‘yes’. If you decide this is the case, then you have options.
Slow the spread!
EAB, like many other species of insect, can spread long distances in wood. Buying and using only local firewood can keep EAB from spreading to new locations. Movement of ash nursery trees and other wood products can also potentially allow EAB to reach new areas and create satellite populations. The Texas Department of Agriculture (TDA) is responsible for regulating the movement of potentially infested products from areas of known EAB outbreaks.
Insecticides
Several commercially available products are registered for treatment of EAB. Trees can be treated with soil injections or drenches, trunk injections, or trunk sprays. Systemic insecticides that list emamectin benzoate as the active ingredient are recommended in areas where EABs is present. These insecticide injections can protect a tree for 2-3 years and can be done either therapeutically or to prevent attacks of EAB.
If you determine the tree to be insignificant, it can be turned into mulch or used for firewood. However, be advised that EAB can survive for up to two years after a tree is cut down. So, if you chop down an infested tree and move it to your woodpile, you may be moving EAB closer to other, still-healthy trees.
Tree removal
The cost of removing dead or dying trees can be straining on budgets. Local communities and homeowners may pay to try and prevent infestation or remove infested trees from their properties. The best way to do this is to hire a trained professional who has experience removing EAB infested trees. You should always be sure that whoever you contract is insured and bonded in case of an accident, which is information real professionals should be happy to share. It is also vital that dead trees are disposed of properly to slow the spread of EAB and ensure the dead tree does not damage or harm any person, pet or property. Since EAB can survive in the wood of a dead tree for years, this is a vital step no matter how long the tree has been dead for. This is also why it’s imperative you burn, bury or chip the tree where it is, rather than transport it somewhere else. Transporting it may spread EAB to new counties that are currently EAB free.
Removing ash trees that are in poor condition or that are infested with EABs can help to slow the spread of the insect. Infested wood must be disposed of properly by chipping as insects can still emerge and travel to other trees, even after a tree has died and been cut down.
Most importantly make sure to report any symptomatic ash trees to your local Texas A&M Forest Service office or call the EAB hotline at 1-866-322-4512.
For more information on how to protect your Ash trees, visit:
Emerald Ash Borer Information Network: Information for Homeowners
How do EAB kill ash trees?
Adult EAB lay eggs in the bark of ash trees in the late summer. The larvae burrow into the bark and are sheltered by it during the winter months. The larvae feed under the bark (in the phloem and cambium) disrupting the flow of nutrients within the tree, hindering the transport of nutrients and water within the tree. When the beetles emerge as adults, they leave D-shaped holes in the bark about one-eighth of an inch wide.
EAB weaken trees in the winter and kill them in the summer and because they are invasive to the U.S., our ash trees do not have any natural defenses against them. Once an ash tree is infested, it is very likely it will die. In areas where EAB is well established, it can kill an ash tree within a year of the initial infestation.
How can your community prepare for EAB?
We can help communities develop, communicate and implement an EAB preparedness plan.
An EAB preparedness plan will not necessarily prevent EAB or the loss of community ash trees, but instead give communities information and decision-making tools, minimizing any suffering caused on the community by this invasive insect.
Guide for Texas Communities
Community Forest Planning: Emerald Ash Borer
EAB State Summary of Potential EAB Impacts
What effects would losing all of our ash trees have on our community?
Losing and removing all the community ash trees without a mitigation or replacement plan could cause a/an:
- Permanent loss from urban forest that will take years, or generations to replace
- Increased storm water runoff and water consumption
- Increase energy costs and higher temperatures, in urban and suburban areas
- Decrease in property value and neighborhood character
- Impact bird and arthropod communities that rely on this resource for food, shelter, and reproduction.
What are we doing to help?
We investigate suspected EAB infestations with particular concern paid to detections occurring in previously un-infested counties.
Don’t Move Firewood
EAB can travel long distances inside firewood, much further than it could by flight alone. EAB can also travel in unprocessed ash logs, ash nursery stock and other ash commodities.
An EAB quarantine regulates the movement of firewood, ash nursery stock, ash timber and other material that can spread EAB. It is important to know where the emerald ash borer quarantines are if you are traveling between infested states or counties that are known to be infested. EAB quarantines in Texas are established and enforced by the Texas Department of Agriculture (TDA).
Authorities are asking people follow these simple rules:
- Leave firewood at home. Don’t transport firewood, even within the state.
- Use firewood from local sources near where you’re going to burn it, or purchase firewood that is certified to be free of pests (it will say so on the label included with the packaging).
- If you have moved firewood, burn all of it before leaving your campsite.
- Learn more at Don’t Move Firewood.
Biological control
The Operation Biocontrol Program being conducted by USDA APHIS has successfully released parasites that specifically target EAB across the eastern United States. In many regions, these parasites have been recovered and show promising results as the suppress EAB populations to low densities but, as of 2023, none of these tests have been successful in the Southern United States.
Trapping Efforts
We are responsible for Texas’ EAB detection program. Triangular purple box traps are placed in ash trees to determine if EAB are in the area. The traps are coated with an adhesive that captures insects when they land.
The color attracts EAB and is relatively easy for people to spot among the foliage. If you see an EAB trap, stay clear of it. It is capturing vital data that could be compromised if you disturb it.
In preparation for the arrival of EAB to the state, we helped develop a multi-partner, state EAB response plan.
The EAB response plan includes establishing each involved agency’s responsibilities, removing ash trees as a preemptive measure, selecting ash tree treatments and planting tree species not susceptible to EAB. This assessment and implementation process typically takes 60-90 days and is submitted to the public for comment before being implemented.
Article source and photo credit: TEXAS A&M FOREST SERVICE
