Tree care is crucial, especially when dealing with pests like the emerald ash borer. Though small and seemingly harmless with its bright metallic-green color and size smaller than a dime, this beetle is one of the most destructive pests in North America. It has caused the death of hundreds of millions of ash trees across the continent. Believed to have entered the U.S. from Asia, it was first identified in southeastern Michigan in 2002.
Ash trees, known for their durability and beauty, are commonly found throughout North America, particularly east of the Rocky Mountains. Unfortunately, the emerald ash borer is rapidly destroying these beloved trees. Ash wood, prized for its strength and lightweight nature, is often used in the production of baseball bats, tool handles, furniture, and flooring. Without proper intervention, the spread of this pest will continue to devastate ash populations and disrupt industries dependent on ash wood.
With a focused approach, we can help prevent further destruction.
What is an Emerald Ash Borer and its Origin?
The Emerald Ash Borer (EAB), scientifically known as Agrilus planipennis, is a green, jewel-toned beetle that specifically targets ash trees. These beetles lay their eggs in the bark crevices of ash trees, and once the larvae hatch, they feed beneath the bark, disrupting the tree's ability to transport nutrients and water. Over time, this can severely damage or even kill the tree. The larvae take up to two years to mature into adults.
Originally from Asia, the EAB wasn’t destructive in its native environment. However, outside its native range, particularly in North America, it has become an invasive species, causing widespread destruction to ash trees. Adult Emerald Ash Borers are typically a striking metallic green, measuring around 8.5 millimeters long and 1.6 millimeters wide. A unique feature of the EAB is its bright red upper abdomen, which can only be seen when its wings are spread.
This invasive beetle is a serious threat to ash tree populations, making it critical to monitor and manage its spread.
Does the Emerald Ash Borer Have Natural Predators?
One of the main reasons the Emerald Ash Borer (EAB) is so destructive in North America is the abundance of food and lack of natural predators. With billions of ash trees available to feed on, the EAB population has exploded. In its native range in Asia, several natural enemies, such as parasitoid wasps, play a crucial role in controlling EAB populations. These wasps and other predators target EAB eggs, larvae, and adult beetles, keeping their numbers in balance. However, in North America, the absence of these natural predators has allowed the EAB to spread rapidly and cause extensive damage to ash trees.
Efforts are ongoing to introduce and establish some of these natural predators in North America to help control the EAB population.
How Can I Identify an Ash Tree in My Yard?
There are four species of ash trees that can be targeted by the Emerald Ash Borer: green, white, black, and blue ash. However, mountain ash, another species, is not affected by EAB. So far, EAB has not attacked any other tree species in North America.
To help you identify an ash tree in your yard, arborists recommend looking for the following key features:
Opposite Branching
One distinctive characteristic of ash trees is their opposite branching pattern. This means that the branches grow directly across from each other, rather than in a staggered arrangement. However, keep in mind that some limbs may have broken off or died, so not every branch will have an opposite mate. Additionally, ash tree branches are typically gray to brown in color and lack a waxy coating.
Leaves
Ash tree leaves are compound, consisting of 5 to 11 individual leaflets. The edges of these leaflets can be either smooth or toothed. At the end of each branch, there is a single bud. It's important to note that the only other tree with opposite compound leaves, which can sometimes be confused with an ash tree, is the boxelder.
Bark Patterns
As ash trees mature, their bark develops a tight pattern with noticeable diamond-shaped ridges. In contrast, younger ash trees have smoother bark, making it easier to differentiate between mature and juvenile trees.
Seeds
Ash tree seeds, known as samaras, are dry and shaped like small oars. They typically grow in clusters and remain on the tree until late autumn or early winter, making them a distinguishing feature during those seasons.
How to Detect Emerald Ash Borer (EAB) Infestation
Emerald Ash Borer (EAB) is a destructive pest that attacks and kills ash trees by burrowing into them and feeding on their vital nutrients. The beetles lay larvae in the bark, allowing them to reproduce and spread quickly. Early detection and proactive beetle prevention are key to controlling an EAB infestation, though it can be challenging.
There are several clear signs to watch for that can help you identify the problem before it’s too late:
1. Larvae or Adults
Look for larvae under the bark, which are cream-colored and slightly flattened, with pincher-like appendages at their abdomen. Adult EAB beetles have a shiny emerald or coppery green body, narrow in shape (3-3.5mm wide) and around 7-8mm long. Their large, kidney-shaped eyes are either bronze or black, making them easily distinguishable.
2. Epicormic Shoots
When an ash tree is stressed, it may produce new shoots, known as epicormic shoots, which can grow rapidly from the trunk, crown, or larger branches. These shoots are also called water sprouts, suckers, or witches’ brooms. Not every tree attacked by EAB will produce these shoots, but they can be a sign of infestation when conditions are right.
3. Increased Woodpecker Activity
Woodpeckers often feed on the larvae hidden beneath the bark. If you notice an increase in woodpecker activity around your ash trees, this may be a strong indication of EAB presence.
4. D-Shaped Exit Holes
As adult beetles exit the tree, they create distinct D-shaped holes in the bark. These holes are a key characteristic of the EAB and the beetle group it belongs to.
5. S-Shaped Tunnels Under the Bark
Larvae feeding beneath the bark create S-shaped tunnels that curve as they move up or down the tree. The width of the tunnels increases as the larvae grow, making these tunnels more noticeable over time.
6. Branches Dying from the Top Down
As EAB beetles continue to feed, the tree’s branches will begin to die off from the top down. You’ll notice the foliage turning yellow, wilting, and eventually falling off, leaving bare branches behind.
7. Vertical Bark Splits
Infested trees often develop vertical splits in their bark. These cracks are a common sign that the tree is struggling under the stress of the infestation.
8. Leaf Notches
Adult beetles feed on ash leaves, creating notches on the leaf edges. In areas where the beetle population is high, this notching can lead to noticeable defoliation.
It’s important to note that some of these symptoms, like drought and other tree injuries, can mimic the effects of an EAB infestation. However, if you spot multiple signs from this list, it’s crucial to act quickly to prevent further damage to your trees. With these signs in mind, you’ll be better equipped to spot EAB infestations early and take appropriate action.
How Can I Help Stop the Spread of the Emerald Ash Borer?
Preventing the spread of the Emerald Ash Borer (EAB) is crucial to protecting ash trees from this invasive pest.
There are several key tactics you can take to help mitigate its impact:
Do Not Transport Firewood
One of the most effective ways to prevent the spread of EAB is by avoiding the transportation of firewood. Firewood can be infested with the beetles, even if it appears unaffected on the outside. Moving firewood from one location to another can introduce the pest to new, non-infected areas, increasing the risk of infestation.
This is particularly important in regions where the emerald ash borer hasn’t yet been detected. Unfortunately, many infestations near campgrounds and homes with wood stoves have been directly linked to the movement of infested firewood. Instead, buy firewood locally, near the area where you plan to use it, to minimize the risk of spreading EAB.
Plant Other Types of Trees
While ash trees have long been favored for landscaping, their vulnerability to EAB has made them a risky choice in many regions. Arborists now recommend planting other tree species native to your area that offer similar benefits for wildlife and the environment. These alternatives can provide shade, aesthetic value, and habitat for animals, while also being more resilient to pests like the EAB.
Consider Treating Affected Trees
If an ash tree on your property is infested, you can either remove and replace it or attempt treatment. There are several insecticide treatments available, some of which can be done by homeowners, while others require a licensed professional. Here are the most common treatment methods:
Trunk Injection: This method involves drilling small holes into the tree to inject insecticide. Although it's the most expensive option and can cause some damage to the tree, trunk injection is also the most effective and long-lasting treatment. It’s ideal for high-value trees that you want to preserve.
Soil Drenching: This treatment is suitable for trees with a trunk diameter under 12 inches. You can apply insecticides like imidacloprid or dinotefuran to the soil around the tree’s base once a year. It comes either in liquid form, diluted with water, or as granules applied directly to the soil. While effective, soil drenching can impact other nearby plants, insects, and animals, so use caution when applying it.
Bark Spray: Another option is spraying the lower 5 to 6 feet of the tree’s bark with an insecticide once a year. The insecticide penetrates the bark and spreads through the tree’s vascular system. However, this method poses the risk of the insecticide drifting onto other plants, which could harm non-target insects and animals.
By planting alternative species and considering the right treatment options, you can help slow the spread of the Emerald Ash Borer and protect the health of trees in your community.
Conclusion
Preventing the spread of the Emerald Ash Borer (EAB) is crucial to protecting ash trees and the ecosystems they support. By following key steps such as avoiding the transportation of firewood, planting alternative tree species, and treating infested trees, we can collectively reduce the devastation caused by this invasive pests. Early detection through canopy inspection, bark checks, and monitoring for signs like epicormic shoots can also help save trees before significant damage occurs. Remember, managing EAB requires a proactive approach, but with the right actions, we can help preserve our ash tree populations and the industries that depend on them.
FAQs
What is the Emerald Ash Borer (EAB)?
The EAB is an invasive beetle from Asia that targets ash trees, causing extensive damage by feeding on the tree's nutrients.
How can I identify signs of EAB infestation?
Look for thinning tree crowns, D-shaped exit holes, epicormic shoots, vertical bark splits, and increased woodpecker activity.
Why should I avoid transporting firewood?
Firewood may carry EAB larvae or adults, spreading the pest to new, non-infested areas.
Can I treat an infested tree myself?
Yes, soil drenching and bark sprays are DIY options, but trunk injection requires a professional and is the most effective.
What trees should I plant instead of ash trees?
Consult local arborists to select native tree species that offer similar benefits without the risk of EAB vulnerability.
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