Emerald Ash Borer
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The Emerald Ash Borer (Agrilus planipennis) commonly called EAB, is an invasive wood/boring beetle from eastern mainland Asia. It was detected as an invasive pest in the United States in 2002, and has spread throughout the east coast. The EAB spends its juvenile life beneath the bark of ash trees, damaging the flow of nutrients as it grows. The widespread destruction of ash forests by EAB impacts several species of ash trees, and the surrounding arthropod community. We aim to assess the ecological impact that the accidental introduction of this pest has caused these communities, as despite years of research, little is known on the subject.
We are also assessing the efficacy of biological control on EAB populations throughout the state. The biological control comes in the form of four species of small parasitic wasps that have been introduced into Maryland from their native areas in North-Eastern Asia to control EAB populations. These wasps pose no risk to humans as they lay their eggs inside the larvae or eggs of this beetle and may be an effective way to control the pest in both managed and natural forestry landscapes. |
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The EAB is an emerging threat in the west, and the research done here will contribute to effectively controlling their populations wherever EAB is detected as a new invasive. For more information on the EAB, click here.
Log Collection and Rearing
We harvest logs of infested ash trees during the fall and winter to rear the emerald ash borer that lay dormant inside. The trees that are collected are still alive, but show many signs of heavy EAB infestation. These signs range from a vast decay of crown cover, to copious amounts of woodpecks and beetle exit holes. The emerged adults of EAB are used to track the spread of the pest and to aid the research of this insect to the USDA.
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Rearing the EAB requires a simulation of their natural growing environment. The EAB starts its life as an egg laid on a live ash tree. Once hatched, it bores into the bark’s inner layers, into the cambium, and proceeds to feed on it, growing larger until adulthood, when it emerges. Because of their particular life cycle and dependence on ash trees, collecting trees already infested with EAB and subsequently collecting the emerging adults has proven to be more effective than artificial breeding.
Infested trees are collected, labeled, and cut into 2 ft sections before being stored in a walk-in refrigerator that keeps the insects dormant throughout the year. Over time these sections are rotated into our greenhouse barrel setup. Each barrel may contain up to 10 smaller branches or just one large log. Larger logs are propped up to ensure that the highest number of EAB have room to emerge. The barrels are placed into a large greenhouse room in rows, labeled with the setup date, collection date, ID, and a barrel number. |
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Each barrel has a sealed, modified lid with the identification information and two holes. Each hole has a clear plastic cup attached to it outside the barrel, covering the hole entirely. Over time, EAB, and other insects that were on the log will emerge and make their way towards the light to the plastic cup. These cups are checked every day after setup, and if there is an EAB inside, the cup is screwed off, capped, and replaced with a new cup. The collected EAB are then shipped off to the USDA, while any other arthropods that emerge are collected, recorded, and stored separately clearly identified.
The rearing barrels remain active for approximately two months to ensure all specimens are collected from the log. After this period, the logs are discarded, and the barrels are cleaned of any debris. Any dead EAB or associates found in the barrels after disposal are collected for later
review.
The rearing barrels remain active for approximately two months to ensure all specimens are collected from the log. After this period, the logs are discarded, and the barrels are cleaned of any debris. Any dead EAB or associates found in the barrels after disposal are collected for later
review.
Debarking
In addition to log collection and rearing, we also track EAB and other arthropods through annual debarking at select sites.
The debarking process involves carefully peeling back the bark of infested ash trees using drawknives. If done with enough caution, any insects living beneath the bark within the cambium can be observed and collected. Thanks to the EAB’s trademark galleries within the wood, we can follow its trail and record whether it survived, was eaten, or parasitized. When live larvae are found, they are collected and stored in one of our growth chambers. Ideally, any parasitoid that attacked it will mature into adulthood and be taxonomically identified.
Combined with log rearing, debarking helps us to better understand the spread of EAB and its biological control. The debarking sites are specifically chosen with parasitoid release sites in mind, as well as areas with ample ash tree populations.
The debarking process involves carefully peeling back the bark of infested ash trees using drawknives. If done with enough caution, any insects living beneath the bark within the cambium can be observed and collected. Thanks to the EAB’s trademark galleries within the wood, we can follow its trail and record whether it survived, was eaten, or parasitized. When live larvae are found, they are collected and stored in one of our growth chambers. Ideally, any parasitoid that attacked it will mature into adulthood and be taxonomically identified.
Combined with log rearing, debarking helps us to better understand the spread of EAB and its biological control. The debarking sites are specifically chosen with parasitoid release sites in mind, as well as areas with ample ash tree populations.
Frequently Asked Questions
What is the impact of your research?
Our research is used to inform the national community on control measures for emerald ash borer. Our assessment on the efficacy and impact of biological controls in Maryland can be used to inform public and academic authorities on the best practices for controlling the pest in states that emerald ash borer has not yet invaded.
In addition, our assessment of the pest’s ecological impacts and use of modeling to predict future ecological impacts will be vital in understanding how well ash forests can recover from invasion. This can inform us on best practices to aid in the recovery and regeneration of ash forests in similar environments across the nation.
Why do you need trees that are infested with emerald ash borer?
Emerald ash borer larvae feed on phloem tissue just under the bark of trees. Here they will wait out the cold winter and pupate to become adults in the spring. We harvest infested ash trees to collect these larvae while they are laying dormant for the winter. Once collected we will rear the adult beetles from the logs by incubating them for a period of about three weeks. Once the beetles have emerged we send them off to USDA:BIIR in Newark, DE so their offspring can be used to rear parasitic wasps. These wasps are then released as part of field experiments used to assess several aspects of the wasp’s ecology, phenology, life cycle, and efficacy as a biological control.
Won't I be able to treat my trees with pesticides, why bother with biological control?
Chemical controls like TREEage (emamectin benzoate) work well to protect individual trees but are logistically ineffective at treating emerald ash borer on a large scale in more remote areas. A combination of biological control and chemical control aims to protect valuable trees with pesticides while controlling the pest at large in less managed landscapes. Chemical control is perfect for short term protection but is not reasonable for long-term control of the pest.
How can I learn more about emerald ash borer and keep up to date with recent information on the pest?
You can learn more about the emerald ash borer invasion and signs on how to spot it by visiting the UMD extension page on emerald ash borer by clicking here. You may also consider subscribing to Landscape and Nursery IPM Alerts located here to learn more information about other pests in our area.
I have a tree that's infested with emerald ash borer, would it be of any use to you?
We are always eager to find more locations to harvest logs for emerald ash borer rearing. While there is not guarantee that we would be able to collect or use your infested tree, it could certainly help us to be made aware of it. You can send us an email at saker@umd.edu. Please include photos of the tree and your location.
What other insects are found in the rearing barrels, and are they beneficial?
There is a whole host of other insects that come out of the ash logs we collect, and we call these "associates" due to their association with ash trees. These insects range from parasitoid wasps that prey on a variety of larva, to flies, moths, and other native wood boring beetles. These insects are collected in ethanol and logged for further community analysis, so every insect counts! Below is a small gallery of the most common associates reared. Click on an associate to learn more about it.
Our research is used to inform the national community on control measures for emerald ash borer. Our assessment on the efficacy and impact of biological controls in Maryland can be used to inform public and academic authorities on the best practices for controlling the pest in states that emerald ash borer has not yet invaded.
In addition, our assessment of the pest’s ecological impacts and use of modeling to predict future ecological impacts will be vital in understanding how well ash forests can recover from invasion. This can inform us on best practices to aid in the recovery and regeneration of ash forests in similar environments across the nation.
Why do you need trees that are infested with emerald ash borer?
Emerald ash borer larvae feed on phloem tissue just under the bark of trees. Here they will wait out the cold winter and pupate to become adults in the spring. We harvest infested ash trees to collect these larvae while they are laying dormant for the winter. Once collected we will rear the adult beetles from the logs by incubating them for a period of about three weeks. Once the beetles have emerged we send them off to USDA:BIIR in Newark, DE so their offspring can be used to rear parasitic wasps. These wasps are then released as part of field experiments used to assess several aspects of the wasp’s ecology, phenology, life cycle, and efficacy as a biological control.
Won't I be able to treat my trees with pesticides, why bother with biological control?
Chemical controls like TREEage (emamectin benzoate) work well to protect individual trees but are logistically ineffective at treating emerald ash borer on a large scale in more remote areas. A combination of biological control and chemical control aims to protect valuable trees with pesticides while controlling the pest at large in less managed landscapes. Chemical control is perfect for short term protection but is not reasonable for long-term control of the pest.
How can I learn more about emerald ash borer and keep up to date with recent information on the pest?
You can learn more about the emerald ash borer invasion and signs on how to spot it by visiting the UMD extension page on emerald ash borer by clicking here. You may also consider subscribing to Landscape and Nursery IPM Alerts located here to learn more information about other pests in our area.
I have a tree that's infested with emerald ash borer, would it be of any use to you?
We are always eager to find more locations to harvest logs for emerald ash borer rearing. While there is not guarantee that we would be able to collect or use your infested tree, it could certainly help us to be made aware of it. You can send us an email at saker@umd.edu. Please include photos of the tree and your location.
What other insects are found in the rearing barrels, and are they beneficial?
There is a whole host of other insects that come out of the ash logs we collect, and we call these "associates" due to their association with ash trees. These insects range from parasitoid wasps that prey on a variety of larva, to flies, moths, and other native wood boring beetles. These insects are collected in ethanol and logged for further community analysis, so every insect counts! Below is a small gallery of the most common associates reared. Click on an associate to learn more about it.
