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How to Identify Emerald Ash Borer

Understanding the Emerald Ash Borer

The Emerald Ash Borer (EAB) is an invasive species of beetle that has affected ash trees across North America. To effectively identify an EAB infestation, it’s crucial to have a grasp of what the insect is, its origin, and its life cycle. Additionally, knowing the signs of infestation to look for and your options to fight against infestation is critical for saving your ash trees. Let’s get started.

What is the Emerald Ash Borer? 

The Emerald Ash Borer, scientifically known as Agrilus Planipennis is a metallic green beetle native to Asia, specifically China and Korea. This invasive species is believed to have arrived in the United States accidentally, likely through the transport of infested wood packaging materials. The first known infestation in North America was discovered in Michigan in 2002. Since then, it has rapidly spread across the continent, leaving destruction in its wake.

Emerald Ash Borer Life Cycle 

To identify an EAB infestation, it’s essential to understand its life cycle. EAB has four distinct stages in its development: egg, larva, pupa, and adult.

  • Eggs: Adult emerald ash borer beetles lay their eggs on the bark of ash trees in the summer months. These eggs are tiny and reddish-brown, usually laid in clusters.
  • Larvae: Once the emerald ash borer eggs hatch, the larvae bore through the bark and into the tree, where they feed on the inner layers, creating characteristic serpentine tunnels called galleries. It is during this larval stage that the most significant damage occurs.
  • Pupa: After a period of feeding, the larvae pupate beneath the bark or in the outer layers of the tree. During this stage, they transform into adult beetles.
  • Adults: Fully developed EAB beetles emerge from the tree, leaving small, distinctive D-shaped exit holes in the bark. These adult beetles then seek out other ash trees to lay their eggs, continuing the cycle.

Why are Ash Trees more vulnerable to EAV Infestation? 

Ash trees are particularly vulnerable to EAB infestations for several reasons:

  • Lack of Natural Predators: In its native range, the EAB is kept in check by natural predators and environmental factors. However, when introduced to North America, it found itself in an environment without the same natural checks and balances, allowing its population to explode.
  • Lack of Tree Resistance: Unlike some tree species that have evolved defenses against local pests and diseases, ash trees did not co-evolve with the emerald ash borer. As a result, they lack natural resistance mechanisms, making them susceptible to EAB attacks.
  • Similar Environmental Preferences: Both the EAB and ash trees prefer similar environmental conditions, which further enhances the likelihood of infestation. These beetles thrive in temperate climates, and ash trees are prevalent in many North American landscapes.
  • Tree Stress: Ash trees weakened by stress factors such as drought, injury, or disease are more susceptible to EAB infestation. These stressors make it easier for the beetles to invade and cause extensive damage.

Signs of EAB Infestation

Understanding the signs of Emerald Ash Borer infestation is crucial for early detection. Several telltale signs indicate the presence of EAB in your ash trees.

  • D-Shaped Exit Holes: This is one of the most distinctive signs. These holes are left on the bark by emerging adult beetles. These small, half-moon-shaped holes are a clear indicator of EAB activity. 
  • S-Shaped Galleries: These are created under the bark by EAB larvae as they feed on the tree’s inner layers. As these galleries disrupt the tree’s vascular system, it hinders the flow of nutrients and water, eventually leading to the trees’ decline.
  • Crown Dieback & Thinning Canopy: This is when the upper branches and leaves start to wither and die as the EAB infestation progresses.
  • Epicormic Shoots: These are small branches that sprout from the trunk and branches of the tree, which are a response to stress from the EAB feeding.
  • Bark Splitting: As a result of the tree’s struggle to cope with the infestation bark splitting is often seen.

Seasonal Considerations in EAB Infestations

Understanding the seasonality of Emerald Ash Borer infestations is key to effectively identifying and managing the destructive pest. The appearance of symptoms and the likelihood of an infestation can vary with the changing seasons.

  • Spring and Early Summer (April-June): During spring and early summer, EAB adults become active, emerging from their overwintering sites within ash trees. This is when they mate and lay eggs on the bark of ash trees. While EABs are difficult to spot due to their small size and greenish color, you may notice the emergence of D-shaped exit holes on the tree’s bark. Additionally, this is the time when the first signs of crown dieback and thinning canopy may become noticeable due to larvae beginning to feed on the tree’s inner layers.
  • Late Summer and Fall (July-September): As the season progresses, EAB larvae continue to feed within the tree and create S-shaped galleries under the bark. These galleries may not be visible from the outside but the damage they cause becomes more pronounced and leads to further canopy decline. By this time, you may also observe an increase in the number of epicormic shoots.
  • Winter (Late November-March): During the winter months, EAB activity slows down. The larvae remain dormant beneath the tree’s bark, and the adult beetles are not active. However, this is a critical time for assessing tree health. Infested ash trees may display bark splitting due to the strain caused by the EAB larvae. While bark splitting can be observed year-round, it may become more noticeable in the winter as the bark tightens due to cold temperatures. 

Inspection and Confirmation of EAB Infestations

Detecting Emerald Ash Borer infestation in its early stages is crucial for tree preservation. After completing a self-diagnosis by looking for the signs listed above, it is important to work with a certified arborist if you feel you have an EAB infestation, they can guide appropriate treatment options to protect your ash trees. Fox Valley Tree Care, with its team of expert arborists, can provide a comprehensive inspection and tailored treatment plan for your ash trees in the Fox Valley. 

Prevention of Emerald Ash Borer Infestation

Preventing EAB infestation is crucial to protect your ash trees and the broader ecosystem. Here are some tips on how you can prevent EAB infestation: 

  1. Proper Tree Care Practices:
    1. Regular Pruning and Maintenance: Keep your ash trees healthy by pruning dead or weak branches and maintaining proper tree structure.
    2. Mulching: Apply mulch around the base of the tree to conserve soil moisture, regulate temperature, and improve overall tree health.
    3. Adequate Watering: Ensure your ash trees receive sufficient water, especially during dry periods, to reduce stress and vulnerability to EAB.
    4. Fertilization: Consider professional fertilization to improve tree vigor, making them less susceptible to infestations.
  2. Early Detection and Reporting:
    1. Regularly inspect your ash trees for signs of EAB infestations, including D-shaped exit holes, S-shaped galleries, crown dieback, thinning canopy, epicormic shoots, and bark splitting, as mentioned earlier.
    2. If you suspect an infestation, contact local forestry or agriculture authorities to report the issue. Early reporting can help implement control measures promptly.
  3. Insecticide Treatments:
    1. Consult with certified arborists or tree care professionals to determine if insecticide treatments are suitable for your ash trees.
    2. Insecticide applications can be effective in protecting ash trees, particularly when administered preventively or in the early stages of infestation.

Be in the Know to Protect Your Ash Trees

In the fight against destructive Emerald Ash Borer (EAB), knowledge and vigilance are important. Early detection is the best chance to save ash trees and preserve the ecosystem they support. Inspect your ash trees regularly and contact your local arborists if you feel you may have an infestation. If you’re in the Fox Valley area and believe your ash trees may be affected by EAB, don’t hesitate to contact Fox Valley Tree Care. Their team of expert arborists is well-equipped to assess and address EAB infestations, ensuring the health and longevity of your ash trees.

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