Ash trees are beautiful, strong, and often a central feature of your yard. They provide shade, beauty, and value to your property. But there is a tiny pest that can destroy them. We are talking about the emerald ash borer (EAB).
If you have ash trees in Franklin, Brentwood, or Middle Tennessee, it’s important to understand how to protect them. In this guide, we’ll walk through everything you need to know about ash tree treatment for emerald ash borer. You’ll get detailed information about monitoring, treatment options, and preventive care.
What is the Emerald Ash Borer (EAB)?
EAB is a destructive beetle that evolved in Asia. The invasive creature can fully kill up to 99% of ash trees. It does this within 8 to 10 years from the time when it infests it. The beetle feeds on the tree bark. This stops the nutrient flow to the tree. The larvae form a tunnel in the shape of an S. This is the cause of swift tree death within a year to four years.
Key Details About the Emerald Ash Borer
Appearance
Small, metallic green beetles about half-inch long. They have a width of ⅛ inch.
Destructive Life Stage
Larvae are white and flat. They feed on the tree’s inner bark (phloem and cambium).
Signs of Infestation:
- D-shaped exit holes
- Crown dieback
- Vertical bark cracks, and
- Woodpecker damage.
Spread
EAB can fly on their own. But their spread is generally more a result of people moving infested firewood and wood products.
Impact
EAB has led to the death of millions of ash trees in North America. Natural predators are not able to halt or slow their spread.
Why Early Treatment Matters
Emerald ash borer infestations progress quickly. Once a tree shows severe symptoms, it may be too late to save it. Early treatment can:
- Stop the EAB from spreading inside the tree.
- Keep your tree healthy and safe.
- Save your property from the expense of tree removal.
Knock On Wood Tree Services in Franklin and Brentwood helps homeowners and property managers by assessing trees early and applying the right treatments. They help protect ash trees before severe damage occurs.
Signs Your Ash Tree Might Have EAB
Some common signs of EAB include:
- D-shaped exit holes in the bark: This is where adult beetles leave the tree.
- Bark splitting or cracks: Larvae feeding can cause bark to split.
- Sparse foliage: Leaves may thin or drop early.
- Woodpecker damage: Birds may peel bark off the tree to eat larvae.
EAB Beetle Monitoring / Identification
Monitoring is an important part of ash tree care. It helps determine when and if treatment is needed.
How to Monitor for EAB
- Check your ash trees in spring and summer.
- Look for D-shaped holes, bark splits, and early leaf drop.
- Examine branches and twigs for unusual thinning or dieback.
- Look for woodpecker activity. It can indicate larvae inside the tree.
Early detection makes preventive treatment much more effective.
Treatment Options for Emerald Ash Borer
There are several ways to treat ash trees against EAB. Choosing the right method depends on the tree’s size, health, and level of infestation.
1. Soil Injection
Soil injections involve applying insecticide around the base of the tree. The tree absorbs the chemical through its roots.
Pros:
- Less visible than trunk injections.
- Protects the tree over the growing season.
- Can be combined with other PHC practices.
Cons:
- Works best in healthy trees.
- Requires proper timing in spring or early summer.
Knock On Wood uses safe and effective soil injections as part of their PHC program, ensuring your ash tree receives the treatment it needs without harming surrounding plants.
2. Trunk Injection
Trunk injections deliver insecticide directly into the tree. The chemical moves through the vascular system, targeting the larvae.
Pros:
- Highly effective at reaching pests inside the bark.
- Can treat trees that already show early infestation signs.
Cons:
- Needs professional application.
- Slightly more invasive than soil injections.
3. Basal Bark Spray (Dinotefuran)
Basal bark spray is applied to the lower 5–6 feet of the tree trunk. A surfactant is required to help the chemical absorb into the bark.
Pros:
- Can target EAB larvae without drilling into the tree.
- Useful for smaller trees or as a supplemental treatment.
Cons:
- Less effective than trunk injection for larger trees.
- Works best on younger, smaller trees.
- Needs careful application to avoid runoff or harm to other plants.
This method can be used in combination with other PHC practices for overall tree protection.
When to Use Each Method
| Treatment Method | When to Use | Notes |
| Trunk Injection | For best results on medium to large trees or trees with early EAB signs | Highly effective, professional application needed |
| Soil Drench / Soil Injection | DIY small trees or supplemental care for healthy trees | Less visible, works well with PHC program |
| Basal Bark Spray | Limited use on small or young trees | Requires surfactant, less effective on large trees |
Plant Health Care and Tree Care Tips
Healthy trees are more resistant to pests. Plant Health Care (PHC) focuses on keeping your trees strong. PHC involves:
- Routine monitoring for pests and disease.
- Preventive treatments like fertilization or pest control.
- Pruning and mulching to reduce stress.
While trees dominate your landscape, remember they share soil with grass, shrubs, and other plants. Treatments for one plant can affect others. For example:
- Fertilizer applied to your lawn can affect the tree’s roots.
- Pruning or fertilizing the tree can influence turfgrass growth.
Knock On Wood’s team considers the whole landscape when performing treatments. They ensure your tree, lawn, and other plants all stay healthy together.
Step-by-Step Guide for Homeowners
Here’s a simple plan you can follow to protect your ash trees from emerald ash borer:
- Inspect your trees
- Look for exit holes, bark splits, sparse leaves, and woodpecker damage.
- Monitor regularly
- Check trees each spring and summer. Keep a log of changes.
- Contact a certified arborist
- A professional can confirm EAB presence and recommend treatment.
- Choose the right treatment
- Soil injection, trunk injection, or a combination based on tree health.
- Apply preventive care
- Mulch, water, and fertilize to reduce stress.
- Follow-up monitoring
- Check treated trees annually to ensure EAB is under control.
Not every ash tree needs treatment for emerald ash borer. Some trees are too damaged or not worth the investment. This section helps you decide if your tree should be treated or removed.
Treat Your Tree If:
- The tree is large and mature – bigger than 12–15 inches in diameter at breast height (DBH). Mature trees give shade, beauty, and value you can’t replace.
- Canopy loss is limited – less than 30–50% of leaves are gone. Fifty percent is the absolute maximum.
- The tree is healthy overall – no major diseases or structural problems.
- The tree has high landscape value – provides shade, improves aesthetics, has sentimental value, or increases property value.
- EAB is nearby – within 15 miles or reported in your county.
- The tree is in a prominent spot – near your house, facing the street, or serving as a yard focal point.
Do NOT Treat your Tree if:
- Canopy is mostly gone – over 50% thinning or dieback.
- The tree has poor structure – significant decay or weak branches.
- The tree has low value – young, small, or easily replaceable.
- The tree has multiple health problems – disease or pest issues beyond EAB.
- The tree is in a hazardous location – close to structures, power lines, or dangerous areas.
- The budget can’t sustain long-term care – EAB treatments often need repeated application over many years.
How to Assess Your Tree:
- Measure DBH – diameter at breast height, 4.5 feet from the ground.
- Check canopy health – estimate how much foliage is left.
- Consider location and role – is it a central feature or near important structures?
- Think long-term – weigh the cost versus benefits over 20+ years.
- Consider sentimental or historical value – some trees are priceless to you or your family.
Why Professional Help is Important
Treating emerald ash borer is not a DIY project. Using the wrong chemicals or timing can harm your tree or surrounding plants. Professional arborists like those at Knock On Wood:
- Evaluate the tree’s health carefully.
- Apply treatments safely to target pests effectively.
- Monitor for ongoing pest activity and recommend next steps.
Our team is dedicated to delivering the best plant health services in Franklin and Brentwood, TN. We make the process simple, safe, and effective.
Long-Term Care and Prevention
Even after treatment, ash trees need ongoing care:
- Continue plant health care programs to maintain vitality.
- Monitor for return of EAB activity each season.
- Keep the tree hydrated and mulched to reduce stress.
- Prune dead or damaged branches promptly.
Healthy trees not only survive pests better, but they also enhance your property’s beauty and value.
When Removal Becomes Necessary
In some cases, EAB damage is too severe. Signs that a tree may need removal include:
- Over 50% canopy loss
- Extensive bark splitting and dieback
- Weak or decayed structural branches
Knock On Wood can safely remove hazardous ash trees while protecting your property and surrounding landscape. We also offer firewood from removed trees, giving your landscape a sustainable benefit.