Does Ash Borer affect other trees? - Plant Care Guide

No, the Emerald Ash Borer (EAB), which is the most commonly referenced "ash borer" in North America, primarily affects only ash trees (genus Fraxinus) and does not typically infest other tree species. EAB is highly host-specific, meaning its life cycle and feeding habits are uniquely adapted to ash trees, making them the exclusive target of this destructive invasive pest. While a recent study did note some feeding on white fringetree, ash remains the only primary host.

What is the Emerald Ash Borer and why is it so destructive to ash trees?

The Emerald Ash Borer (EAB), Agrilus planipennis, is a small, metallic green beetle that is an invasive species originally from Asia. It is incredibly destructive to ash trees (Fraxinus species) because its larvae feed on the phloem and xylem tissues just beneath the bark, effectively girdling the tree and disrupting its ability to transport water and nutrients.

Here's why EAB is so destructive:

• Larval Feeding: The adult EAB beetles lay their eggs in the bark crevices of ash trees. Once hatched, the larvae (grubs) burrow into the tree's inner bark and feed on the vascular tissues (phloem, which carries sugars from leaves to roots, and outer xylem, which carries water from roots to leaves).
• S-Shaped Galleries: As the larvae feed and grow, they create distinctive S-shaped feeding galleries that snake through these vital tissues. These galleries effectively girdle the tree, cutting off its circulation.
• Disruption of Water and Nutrients: When the phloem and xylem are damaged, the tree can no longer transport essential water and sugars between its roots and leaves. This is akin to a blocked circulatory system in an animal.
• Rapid Decline and Death: The disruption of these vital systems leads to a rapid decline in the tree's health. Infested ash trees typically die within 2 to 4 years of initial infestation.
• Lack of Natural Resistance: Ash trees in North America did not evolve with EAB, so they have no natural defenses against this pest. Unlike Asian ash species that have developed resistance, North American ash varieties are highly susceptible.
• High Reproductive Rate: EAB has a high reproductive rate, and its populations can explode quickly, leading to widespread infestation and destruction of ash forests.

Since its accidental introduction in Michigan in 2002, EAB has killed tens of millions of ash trees across North America, profoundly altering forest ecosystems and urban landscapes.

What specific tree species are affected by the Emerald Ash Borer?

The Emerald Ash Borer (EAB) primarily affects all true ash tree species (genus Fraxinus) native to North America. Its host specificity means it targets these trees almost exclusively for its life cycle and feeding.

The main ash species vulnerable to EAB include:

• Green Ash (Fraxinus pennsylvanica)
• White Ash (Fraxinus americana)
• Black Ash (Fraxinus nigra)
• Blue Ash (Fraxinus quadrangulata)
• Pumpkin Ash (Fraxinus profunda)
• Velvet Ash (Fraxinus velutina)
• Oregon Ash (Fraxinus latifolia)

Essentially, if a tree is identified as an "ash" (with characteristic opposite branching and compound leaves), it is susceptible to EAB.

Recent scientific findings have also shown that EAB can infest and complete its life cycle in White Fringetree (Chionanthus virginicus), which is in the same plant family (Oleaceae) as ash trees. While fringetree can be infested, it is not considered a primary host in the same way ash trees are, and the extent of damage to fringetree populations is still being studied. For the vast majority of commonly planted or wild trees, EAB remains an exclusive threat to ash species.

How can I identify an ash tree on my property?

Identifying an ash tree on your property is crucial for monitoring potential Emerald Ash Borer (EAB) infestations. Ash trees have several distinct characteristics that help differentiate them from other common tree species. The most reliable identifiers are their compound leaves and opposite branching pattern.

Here's how to identify an ash tree:

1. Opposite Branching: This is a key identifier. Ash tree branches, buds, and leaves grow directly opposite each other on the stem, rather than alternating along the branch. While a few other trees (like maple, dogwood, and horse chestnut) also have opposite branching, this narrows down your possibilities significantly.

2. Compound Leaves: Ash trees have compound leaves, meaning each leaf is made up of several smaller leaflets attached to a central stem (rachis).

   • Typically, an ash leaf will have 5 to 11 leaflets (most commonly 7), although blue ash can have 5-9, and pumpkin ash can have 5-9.
   • The leaflets often have finely toothed edges and are somewhat elongated.

3. Bark:

   • Mature Ash: The bark of mature ash trees typically has a distinct diamond-ridge pattern, forming deep, interlacing furrows.
   • Young Ash: Younger ash trees have smoother bark.
   • Distinguish from other trees: Maple bark is typically more fissured or scaly, dogwood is blocky, and horse chestnut is flaky.

4. Buds:

   • Ash buds are typically dark, sometimes nearly black, and are arranged oppositely along the stem. The terminal bud (at the tip of the branch) is usually larger.

5. Seeds (Samaras):

   • Ash trees produce paddle-shaped seeds called samaras that hang in clusters. Each seed has a single wing. These often persist on the tree into winter.

Differentiating from look-alikes (MAPLE):

• Maple: Has opposite branching, but simple leaves (single blade, not multiple leaflets) that are typically palmately lobed (like a hand).
• Boxelder (a type of maple): This is the tricky one, as it also has opposite, compound leaves. However, boxelder typically has 3-5 leaflets (rarely 7), and the leaves often look somewhat sloppier or less refined than ash. The twigs of boxelder are often greenish or purplish with a waxy bloom.

When you suspect you have an ash tree, use a combination of these features, focusing on opposite branching and compound leaves, to confirm its identity. If still unsure, a local arborist or extension office can help.

What are the signs of an Emerald Ash Borer infestation?

Identifying the signs of an Emerald Ash Borer (EAB) infestation early is crucial for effective management and potentially saving your ash tree. EAB symptoms often become noticeable after a few years of infestation, typically starting in the upper canopy.

Here are the key signs to look for:

1. Canopy Thinning and Dieback:

   • Starts at Top: One of the earliest and most noticeable signs is the thinning of the tree's canopy, often starting at the top. Leaves may appear sparse, yellow, or smaller than usual.
   • Branch Dieback: As the infestation progresses, branches in the upper canopy will start to die back.

2. D-Shaped Exit Holes:

   • Distinctive Shape: After the adult beetle emerges from the tree, it leaves behind small, very distinctive D-shaped exit holes in the bark, usually about 1/8 inch (3-4 mm) in diameter. These are a definitive sign of EAB.

3. Serpentine Galleries (under the bark):

   • Winding Pathways: If you carefully peel back the bark on an infested tree (especially in areas of dieback), you'll find winding, S-shaped (serpentine) feeding galleries packed with frass (insect waste). These galleries girdle the tree.

4. Epicormic Shoots (Water Sprouts):

   • Stress Response: When an ash tree is stressed by EAB, it may try to grow new shoots from dormant buds on the trunk or large branches, often at the base of the tree. These are called epicormic shoots or water sprouts, and they are a sign of severe stress.

5. Bark Splits/Vertical Cracks:

   • Callus Tissue: As the tree tries to heal over the larval galleries, the bark may split vertically, revealing the characteristic S-shaped tunnels underneath.

6. Woodpecker Activity:

   • Increased Foraging: Woodpeckers feed on EAB larvae under the bark. An unusual increase in woodpecker damage (flaking off patches of bark) on an ash tree, especially in spring and winter, can be an early indicator of infestation.

7. Adult EAB Beetles (less common to spot):

   • Small, Metallic Green: The adult beetles are about 1/2 inch long, slender, and bright, metallic emerald green. They are often difficult to spot as they are active during the day and can fly.

When checking for EAB, focus on the upper canopy, main trunk, and large branches. If you notice several of these signs on an ash tree, it's highly likely to be infested.

What should I do if I suspect my ash tree has EAB?

If you suspect your ash tree has Emerald Ash Borer (EAB), it's important to act quickly and follow a specific course of action to assess the infestation and determine the best management strategy. Early detection can make a difference in saving the tree.

Here's what you should do:

1. Confirm Identification:

   • Verify Ash Tree: First, double-check that the tree is indeed an ash species, using the identification tips (opposite branching, compound leaves, diamond bark pattern).
   • Verify EAB Symptoms: Look closely for the definitive signs of EAB: D-shaped exit holes, serpentine galleries under the bark, canopy dieback, and increased woodpecker activity.
   • Take Photos: Document your observations with clear photos of the symptoms.

2. Contact Local Experts:

   • Extension Office: Reach out to your local Cooperative Extension System office (often part of a university). They have experts who can confirm EAB presence and provide guidance specific to your region.
   • Certified Arborist: Consult a certified arborist with experience in EAB management. An arborist can provide an on-site assessment of the tree's health and the extent of the infestation. You can find one through organizations like the International Society of Arboriculture (ISA).

3. Assess Infestation Level:

   • Less than 30% Canopy Dieback: If the tree has less than 30% canopy dieback, it may be a good candidate for insecticide treatment.
   • More than 30-50% Canopy Dieback: If the canopy dieback is severe, the tree may be too far gone to save, and removal might be the only viable option.

4. Consider Treatment Options (for salvageable trees):

   • Systemic Insecticides: If treatment is viable, professional arborists can administer systemic insecticides that are absorbed by the tree and kill EAB larvae as they feed. These treatments are often applied annually or biennially. Some homeowners can apply certain products, but professional application is often more effective and safer. Look for products containing emamectin benzoate (professional application, lasts 2-3 years) or imidacloprid (some homeowner products, lasts 1 year).
   • Timing: Treatments are typically applied in spring or early fall.

5. Consider Removal (for severely infested or unsafe trees):

   • If the tree is too damaged or poses a safety risk (dead limbs falling), professional tree removal is necessary.
   • Disposal: Follow local guidelines for disposing of infested ash wood to prevent further spread of EAB. Do not move firewood out of regulated areas.

6. Preventive Measures (for healthy ash trees in EAB areas):

   • If you have healthy ash trees in an area where EAB is present or expected, consider preventative insecticide treatments administered by a professional arborist. This is generally more cost-effective than treating an already infested tree.

Remember, acting quickly and consulting with experts will help you make the most informed decision for your ash tree and contribute to slowing the spread of EAB.

What are the primary methods for treating Emerald Ash Borer?

The primary methods for treating Emerald Ash Borer (EAB) involve systemic insecticide applications, which effectively deliver chemicals into the tree's vascular system to kill EAB larvae and adults as they feed. The choice of treatment depends on the tree's health, infestation level, and whether it's a preventive or active treatment.

Here are the main treatment methods:

1. Basal Bark Spray:

   • Method: A systemic insecticide (e.g., containing dinotefuran) is sprayed directly onto the lower 2-5 feet of the tree's trunk. The bark absorbs the chemical, which then moves into the tree's sap.
   • Application: Can be done by homeowners with some products, but professional application ensures proper coverage and dosage.
   • Frequency: Applied annually.
   • Best For: Trees with a trunk diameter of up to 50 inches. Good for larger numbers of trees due to ease of application.

2. Soil Drench/Injection:

   • Method: A systemic insecticide (e.g., containing imidacloprid or dinotefuran) is applied directly to the soil around the base of the tree. The roots absorb the chemical, which then moves throughout the tree.
   • Application: Some homeowner products are available as soil drenches. Professional products may involve soil injections.
   • Frequency: Applied annually, typically in spring or early fall.
   • Best For: Smaller trees (up to 20-25 inches in diameter).

3. Trunk Injection:

   • Method: This is a highly effective professional application method where concentrated systemic insecticide (most commonly emamectin benzoate) is injected directly into the tree's trunk, into the xylem tissue. The tree's sap then carries the chemical throughout the tree.
   • Application: Must be done by a certified arborist or licensed pesticide applicator.
   • Frequency: Generally lasts for 2-3 years, making it a more convenient option for long-term protection.
   • Best For: Large, valuable trees, or trees with significant canopy dieback (up to 30-50% dieback, though effectiveness decreases with more severe damage). It's also the most environmentally targeted method as the chemical is contained within the tree.

Important Considerations for Treatment:

• Timing: Treatments are typically most effective when applied in spring as trees begin to take up water and nutrients, or in early fall.
• Tree Health: Treatments are most successful on trees that are still relatively healthy (less than 30% canopy dieback). Heavily infested trees are poor candidates for treatment.
• Cost: Trunk injections are often the most expensive per application but less frequent. Soil applications can be cheaper but require annual commitment.
• Environmental Impact: While systemic, these are still insecticides. Trunk injections are generally considered the most environmentally friendly method as the chemical is contained within the tree, minimizing exposure to other organisms.
• Long-Term Commitment: EAB treatments are not a one-time fix. They require an ongoing commitment to reapply the insecticide every 1-3 years as long as EAB remains a threat in your area.

Consulting with a certified arborist is essential to determine the best and safest treatment plan for your specific ash trees.

What are the long-term impacts of Emerald Ash Borer on local ecosystems?

The long-term impacts of the Emerald Ash Borer (EAB) on local ecosystems are profound and extensive, leading to a drastic reduction or near-elimination of ash trees, which in turn causes cascading effects throughout the food web and ecosystem structure. This invasive pest fundamentally alters the composition and function of affected forests and urban landscapes.

Here are the key long-term impacts:

1. Loss of Ash Tree Population:

   • Dominant Species Decline: Ash trees were a dominant species in many North American forest types (especially riparian zones and wetlands) and urban settings. Their widespread mortality creates large gaps in the tree canopy.
   • Altered Forest Structure: The loss changes light penetration to the forest floor, altering understory vegetation.

2. Impact on Wildlife:

   • Habitat Loss: Many bird species (e.g., woodpeckers, owls, flycatchers) used ash trees for nesting, roosting, and foraging. The removal of dead and dying ash trees eliminates this habitat.
   • Food Source Disruption: Some insects and animals relied on ash leaves, seeds, or the trees themselves for food. For example, specific butterflies and moths (like the eastern tiger swallowtail) use ash as a host plant.
   • Increased Woodpecker Populations (initially): Woodpecker populations may initially boom due to the abundance of EAB larvae as a food source, but this is often temporary as the food supply dwindles.

3. Changes in Plant Community Composition:

   • Native Understory Replacement: With increased light, aggressive invasive plants (e.g., buckthorn, honeysuckle) often colonize the gaps left by dead ash trees, outcompeting native understory plants.
   • Successional Shifts: The forest succession pathways are altered, as new species (which may or may not be native or desirable) replace the ash.

4. Altered Hydrology and Soil Dynamics:

   • Water Uptake: Large ash trees transpired significant amounts of water. Their loss can change local hydrology, particularly in wetlands and floodplains.
   • Nutrient Cycling: The sudden influx of dead wood on the forest floor changes nutrient cycling and decomposition rates.

5. Economic Impacts:

   • Timber Industry: Loss of valuable ash timber for lumber, flooring, and other products.
   • Municipal Costs: High costs for tree removal and replacement in urban areas, increased risk of falling limbs, and impacts on property values.
   • Nursery Industry: Shifts in demand for replacement tree species.

6. Reduced Urban Forest Benefits:

   • Ash trees provided vital ecosystem services in cities: shade, air quality improvement, stormwater management, and aesthetic value. Their loss reduces these benefits.

In summary, EAB is an ecological transformer, leading to a profound simplification of forest diversity, significant changes in wildlife habitat, and a shift towards potentially less desirable plant communities, with long-lasting and often irreversible consequences for natural and urban ecosystems.

What is the role of quarantine regulations in controlling EAB?

Quarantine regulations play a critical role in controlling the spread of the Emerald Ash Borer (EAB) by restricting the movement of potentially infested materials, thereby attempting to slow its geographical expansion. These regulations are primarily aimed at preventing human-assisted transport of the pest.

Here's the role of quarantine regulations:

1. Restricting Movement of Infested Materials:

   • Primary Focus: The main goal is to prevent the movement of EAB in its various life stages (eggs, larvae, pupae, adults) to new, uninfested areas.
   • Regulated Items: Quarantines typically restrict the movement of:
     • Firewood: This is the number one pathway for EAB spread. People unknowingly transport infested firewood to campgrounds or cabins, introducing the pest to new areas.
     • Ash Nursery Stock: The sale and transport of ash trees, saplings, or seedlings that might harbor EAB are prohibited.
     • Ash Logs and Wood Chips: Unprocessed ash logs, lumber with bark, and ash wood chips are restricted.
     • Other Ash Products: Any other ash materials that could potentially harbor the beetle.

2. Establishing Regulated Areas:

   • Designated Zones: Quarantines define specific "regulated areas" (counties, states, provinces) where EAB has been detected. Movement of regulated items out of these areas is prohibited or strictly controlled.
   • Permitting: Businesses that process or transport ash materials within or from regulated areas may need permits and must follow specific compliance agreements (e.g., heat treatment, debarking).

3. Slowing the Spread:

   • While EAB can fly short distances, most long-distance spread is due to human activity. Quarantines aim to slow this human-assisted spread, buying time for research into control methods, allowing communities to plan, and preserving ash populations in uninfested regions for as long as possible.

4. Public Awareness and Education:

   • Quarantines are often accompanied by public awareness campaigns (e.g., "Don't Move Firewood" initiatives) to educate residents, campers, and businesses about the risks and regulations.

5. Facilitating Research and Management:

   • By slowing the spread, quarantines provide opportunities for scientists to develop new biological control agents, resistant ash varieties, and improved treatment strategies. They also allow forest managers to prioritize treatment areas and removal plans.

Limitations:

• Quarantines are difficult to enforce perfectly over vast areas and cannot completely stop natural dispersal by adult beetles flying.
• They rely heavily on public compliance and ongoing monitoring.

Despite these challenges, quarantine regulations remain a vital tool in the broader strategy to manage the Emerald Ash Borer and mitigate its devastating impact on ash trees.

Are there any natural predators or biological controls for EAB?

Yes, there are ongoing efforts to identify and utilize natural predators and biological controls for EAB, primarily by introducing several species of parasitic wasps that attack EAB in its native Asia. These biological control programs aim to establish natural enemies that can help regulate EAB populations in North America.

Here are the key biological control agents:

1. Parasitic Wasps:

   • Types: Four species of tiny, stingless parasitic wasps (from the genera Tetrastichus, Oobius, Spathius, and Sclerodermus) have been approved and released in EAB-infested areas of North America.
   • How they work:
     • Oobius agrili: Lays its eggs inside EAB eggs.
     • Tetrastichus planipennisi: Lays its eggs inside EAB larvae.
     • Spathius galinae: Lays its eggs on the outside of EAB larvae, under the bark.
     • Sclerodermus pupariae: Also parasitizes EAB larvae.
   • Impact: When the wasp eggs hatch, their larvae feed on and kill the developing EAB eggs or larvae. The wasp then emerges, continuing the cycle.
   • Goals: The goal of these releases is to establish self-sustaining populations of these wasps that can, over time, provide a level of natural control, similar to how they regulate EAB in its native range.

2. Fungal Pathogens:

   • Research is also exploring the use of entomopathogenic fungi (fungi that kill insects) such as Beauveria bassiana.
   • How they work: These fungi infect EAB larvae and adults, causing disease and death.
   • Status: While showing promise in trials, their widespread application as a biological control in forests is still largely in the research phase or limited to specific applications. You can find Beauveria bassiana products for certain pest control applications.

3. Native Predators (Limited Impact):

   • Woodpeckers: Native woodpecker species (e.g., downy, hairy, pileated woodpeckers) do feed on EAB larvae. In areas with high EAB populations, you often see increased woodpecker activity.
   • Other Generalist Predators: Some native ants, predatory bugs, and spiders may consume EAB eggs or adults, but their impact on slowing large-scale infestations is generally considered minimal.
   • Limitation: Native predators alone are not sufficient to control EAB populations because North American ash trees did not evolve defenses against EAB, and native predators have not adapted to exploit EAB as effectively as Asian predators.

Overall Goal of Biological Control: Biological control is a long-term strategy. It's not expected to eradicate EAB, but rather to establish a complex of natural enemies that can help to reduce EAB populations to less damaging levels over many years, allowing for ash regeneration and survival in the long run.