Frequently Asked Questions about Emerald Ash Borer.

With emerald ash borer (EAB) growing within Sioux Falls and spreading to surrounding communities, I field a lot of questions about EAB. This article is going to cover those common questions about the pest, the treatments to protect ash trees, and EAB management and spread.

How can I tell my ash tree is infested?

It can be very difficult to tell if an ash tree is truly infested. Even for a very qualified arborist, the signs of emerald ash borer may be too small to notice without a thorough canopy inspection and branch sampling. Once signs are obvious to a qualified arborist or to a tree owner, the tree has been infested for many years and is too far gone to do anything with, other than removal.

The best course of action if you have an ash tree is to determine if you want to treat and save your tree or remove it before it is heavily infested. Once EAB finds a tree, it will kill it. Therefore, the need to determine if a tree is infested or not is irrelevant to know. Unless it is a new infestation area.

I don’t see dead or sick ash trees. Is EAB still a problem?

Emerald ash borer is a problem and will be more and more of a problem in Sioux Falls and surrounding area for many years to come. We are still in the early stages of the problem and that is why there is little notice of it.

The problem of EAB is a slow burn until the flame gains enough heat to explode into a bone fire. In large areas like Sioux Falls with as many ash trees as there are, the spread and significance of EAB to the community will be slow. Emerald ash borer is just about everywhere across Sioux Falls and of course is confirmed in Brandon, Canton, Crooks, Baltic, and now Lennox (as of 4/1/24). It is possible it is in other nearby communities nearby or cities farther away, but it usually takes 3-4 years of being in a community before it is noticed and confirmed.

Knowing that, emerald ash borer is doing a similar slow move all across Sioux Falls. There are so many ash trees in Sioux Falls that the overall population of EAB is being spread out. Plus, many ash are being proactively removed and treatment rates are really good in many neighborhoods. All of this slows the increase in EAB populations. But once the beetles start to get hold of untreated ash trees, their population will explode over a few short years. Right now in Sioux Falls, we are right at the point when the beetle population will explode soon. Within the year or the next few, more and more dead and dying ash trees will be visible around neighborhoods.

Are the treatments effective?

Yes. If done correctly and professionally, the treatments have an efficacy of 99.9%. But the key to those statements is “correctly.” There are many contractors offering treatments. Many of those contractors started treating trees once EAB was found with no prior experience. Injecting and protecting an ash tree from emerald ash borer is not as simple as spraying. Chemical rates, timing, and tree condition matter.

Also, care of the tree matters as well. The tree needs water when its dry, proper pruning, and to be healthy enough to fight off other fungal diseases. EAB treatments only protect against insect attacks.

How do I know if my ash tree is a good tree to protect or not?

Not all ash should be protected. But is a personal, value based decision. Its your tree. If you value the tree and its shade or benefit to your landscape, then protection may be the best bet. But if you have 4-5 or more ash trees in your yard, it may not be financially prudent for you to protect them all.

If you want to protect the tree, first consider these points:

  • Is the tree structurally sound? A tree with a split or other defect can fail in a storm, wasting your treatment investment.
  • Is the tree healthy? If the tree is not healthy and well cared for, the treatments can be less effective and of course other diseases may still cause tree decline and death.
  • Are there signs of decay? Trees with heart-rot decay of Fomes decay signs should not be treated. Those trees will have a hard time distributing the insecticide to protect the tree due to the decay of sapwood, plus they will possibly be prone to failure in storms.
  • Is the tree growing in a good place? Trees near or under power-lines or in poor growing locations where they will have to significantly cut back or prevented from being good healthy trees, should not be protected long term.

How long do I need to continue to treat my ash tree(s)? This is getting expensive.

The tough part with this pest, is you will have to either pay to treat the tree or remove the tree (there is no wiggle room long term). Tree injections need to be done indefinitely (for the life of the tree). During periods of active emerald ash borer infestation within your neighborhood or town, treatments are going to be needed every 24 months (every other year or every 2 years, however you want to phrase it). There is NO NEED to treat an ash tree if you do not have a confirmed EAB infestation within 15 miles. After EAB has worked its way through a community and all the untreated ash trees are dead and gone, then treatments can be spread out to every 3 to 5 years.

It does not make much financial sense to pay to protect a tree for a few short years, then have to pay for its removal. Each situation is different. But in most instances, it really boils down to one of those two cost options. My advice; Do not make a rash emotional decision, but to take your time and decide what is best for you financially, long term. EAB does work fast in tree terms, but in human terms, it takes years to kill an ash tree so take a few weeks to decide what is best for you when EAB is announced near you.

How will I know the treatments are working?

Your ash will remain healthy with a full canopy of leaves. Remember, other diseases and environmental stress (drought, etc.) can still occur, but a well treated ash tree will have full protection from any insects trying to suck, chew or bore into the tree.

All of this will be very obvious once insect levels get high enough to start killing nearby untreated ash. They will decline and die and your treated tree won’t.

Will drought prevent the treatment from working?

No. If that were the case, the tree would die from drought stress and not from EAB. Drought stress could slow the distribution of the chemical within the tree. But it will not prevent the overall treatment from working.

Again the trees still need to be cared for (watered, etc.). But other environmental conditions or pest population levels will not affect how well the treatment works or not. The key is that the treatment is done well initially and that the tree is cared for. That will provide the best protection from EAB.

Can I treat an infested ash tree?

Yes. But it depends on how heavily infested the tree is on the effectiveness of the treatment. The treatment effectiveness is far more variable than if done preventatively.

Generally, a tree with only 20-30% canopy loss from emerald ash borer could be recovered. However, do not rely on this as a way to wait for protecting your ash trees.

Infested ash trees that are recovered with treatment will have an uphill climb to be healthy again. Plus they will have other issues during recovery that a preventatively treated ash tree will not. The recovered tree will have dead branches to be pruned out, sprouting of new branches that will be more susceptible to breaking in storms, and the stress of the initial decline to recover from. Those factors can lead the tree more open to decay and other diseases that can cause decline or kill the tree.

In early detections of EAB or a new discovery, often times many of the existing ash in the area can be quickly treated and protected with little visible damage to the trees. It is those trees left unprotected in areas of high infestation that will likely be too far infested to save.

How long will it take EAB to kill an ash tree?

This depends on the amount of insects there are in the area (yard, neighborhood, city) and the health of the ash tree when initially infested. Ash are normally a very tough tree and can withstand more abuse and stress than other species of trees. But not emerald ash borer. Once found by a single EAB adult female, a healthy ash will fully die from the pest within 3- 5years. Obvious signs of decline will start at about 3 years.

A drought stress or ash in poor condition could decline within just 2 years. But initially, it takes time for the insects to go through a few life cycles to damage the tree enough for there to be decline within the tree.

At high insect population levels (peak of the bell curve) then even a healthy ash can fully die within 2- 3 years. Signs of infestation can be seen within a year or two of the tree being found by adult female beetles. Why females? They lay the eggs. And its the larvae that hatch that cause the damage to the trees, not the adults.

Why is an ash killed by EAB such a big concern?

The largest concern over the mass loss of a lot of trees, is pubic safety. When an ash does from emerald ash borer it becomes very brittle and unpredictable. The trees can fall over without warning on even a nice day or parts of the tree can drop without warning.

Because of this removal costs can skyrocket. There is considerable risk to the person or crew doing the removal. Often times the tree cannot be safely climbed or rigged off of. And in severe cases, the only safe way to remove the tree is to push it over with heavy machinery.

It is highly recommended that a tree owner not attempt to take down their own infested ash tree. Hire a qualified and insured arborist. A license to operate from a city or state is not a verification of competency. You will want a minimum of an ISA certified arborist to perform removal of infested ash trees.

I have ash that I don’t want to treat, should I wait to remove them?

No. It may be a hard pill to sallow, but the sooner you remove your ash now, the sooner you can start re-planting. But maybe even more important, you will save money and be safer without having to worry about removing an unpredictable infested ash tree when it does come.

I was told by someone my tree is infested with EAB. How can I know if they are creditable?

Identifying if an ash is infested or not is not a skill anyone can easily learn and with any degree of certainty. I suggest being very skeptical of anyone telling you an ash tree is infested. In fact, I will not tell someone that with any certainty that they’re ash is infested, unless it is very obvious and I can confirm it with visual signs of the beetle (exit hole, galleries in the wood, etc.). There are many many signs of tree decline that COULD be EAB, but often times are not. Any blanket statement about infestation to a tree without data to back it up, is likely a guess or a lie to scare you into doing something outside your best interest. Lastly, I will say that only a entomologist from the State and/or USDA can confirm EAB in a new area.

Will EAB only attack sick ash trees?

No. EAB will kill all unprotected ash trees. There is no natural immunity and no scientific proof or instance of a resistant type of North American ash tree.

Can I keep my ash wood for firewood? Take it camping?

The short answer is NO. Certainly do not move any ash wood you have off your property or outside your community. Many states have county wide moving bans in place, just for this reason. If you take an infested ash log with you camping, you just brought EAB to a new area. This is how EAB spreads, through firewood.

EAB is in a neighboring town, but not mine. When do I start treating my ash trees to protect it?

Treat your ash trees once there is a confirmed EAB infestation within 15 miles of your property. Emerald ash borer is a poor flying insect. They will fly to a nearby tree first before going off searching. If it needs too, it can fly up to 20 miles in a year. But cars and firewoood is usually how EAB is spread long distances.

I found a small green bug, is it EAB?

Very likely not. Its not say it couldn’t be, but these adult bugs are very small and live the majority of their life in the upper canopy of the trees. If you are concerned, take a clear and crisp photo of the bug and send it to the state for identification.

More Information

If this article does not answer your question, please contact me

You can also find more resources for EAB here:

For more on where EAB is in Sioux Falls, read that Blog article here: