Emerald ash borer (EAB) is a very serious problem that threatens all ash trees in the Midwest. As of 8/5/2008 it has been found in Wisconsin and is extensive in northern Illinois. The million dollar question seems to be, “When should I start treatment if I want to protect an ash tree?”
Unfortunately, there are differing opinions on this question and the actual facts are not fully conclusive.
There still is much to be learned. One consistent fact is that whenever they have found EAB, they always say it has been there for 3 to 6 years. It is important to keep this in mind as you make your decisions. Another important point to remember - you have time to deal with this!
Points to consider on treatment:
In our opinion high value, important trees should be considered for treatment: specimen trees, ones shading key areas, etc. Not all ash should be treated, it is a personal decision.
Trees should be healthy.
Yearly treatments with a root zone injected soil systemic insectide have been shown to protect trees from EAB. It is not 100 % effective (nothing in nature is!). Studies suggest it is 85 - 90% effective. It is best if the treatment is in place ahead of insect pressure. It can take several years for a large tree to be fully protected.
New products are becoming available and we are evaluating them. We will have more options as time goes on.
When high numbers of EAB come, other treatments may need to be added due to the shear number of insects that will be present.
Trunk injections should only be done in certain situations. Yearly trunk injection is not good tree care. Soil injection provides protection without damaging the tree.
Planting replacement trees is also an option to consider instead of treatment.
Misdiagnosis could be a big problem. Do not remove a living ash tree because of EAB unless you are sure of what is wrong because there are several look-alike problems. There are also many other problems with ash trees due to the past several years of drought. Most will not warrant removal. If trees are infested they will need special handling. Take time to properly assess the problems and collect all of the relevant facts before you take any action. Remember – you have time!
When should treatment be started? Some people say you could be wasting money in treating when EAB is not very close. Others will point out that early protection is most effective and without good trapping methods we do not know where EAB is for sure. Everywhere they have found EAB it had been present for 3 to 6 years before discovery! What is right for one person may not be right for another. Every customer will have to make up their own mind.