MSU Evaluation of Insecticides to Control EAB Adults & Larvae.
What Are My Choices Now?

How Well Do Insecticides Work for Emerald Ash Borer?

David Smitley, Ph.D. and Deborah McCullough, Ph.D.
Department of Entomology
Michigan State University



 EAST LANSING, Mich. 2004, April  -- Homeowners in southeastern Michigan wanting to protect their ash trees from emerald ash borer themselves should do so by the end of April, advises Michigan State University Entomologist, David Smitley.

 Ash trees in southeastern Michigan are under attack by the emerald ash borer (EAB), a metallic green beetle from Asia. Discovered in North America in the Detroit area in June 2002, it has killed more than 5 million ash trees in southeastern Michigan.

 “Homeowners in the infested area must now make a difficult choice: treat their ash trees each year with insecticide or let them succumb to attack and eventually pay for their removal,” Smitley says.  “Those choosing to protect one or more ash trees can either hire a professional arborist or apply the insecticide themselves. Now until the end of April is the best time for homeowners to treat ash trees against the pest themselves.”

   Bayer Advanced Garden Tree and Shrub Insect Control is the only systemic product on the market that is easy for homeowners to use. Other products must be injected into the trunk or sprayed on, and for large trees these types of applications are best done by certified applicators, such as tree care companies. Other options for protecting ash trees include hiring an arborist to inject ash tree trunks in late May or spraying the trunk and foliage with insecticide in early June and again in early July.

    Smitley says homeowners should make sure they are purchasing the correct product -- look for the words “Tree and Shrub” in large print on the label and imidacloprid as the active ingredient.

      “Many will want to use this product because it is the only one that can be mixed in a bucket of water and drenched around the base of your ash trees,” he says. “In research tests last year, this insecticide [imidacloprid] protected ash trees from borers at four of five sites when it was injected into the soil or drenched around the base of ash trees in mid- to late April. Bayer Tree and Shrub Insect Control comes in a 32-ounce, blue plastic container that costs about $20.”

      Instructions on use of the product – including precautions against skin contact and proper storage -- should be followed exactly as written on the product label.  “For example, it says to use 1 ounce of the insecticide for every inch of distance around the tree trunk,” Smitley says. “Let’s say an ash tree has a trunk diameter of 10 inches and a circumference of 25 inches. For this tree, you would need 25 ounces of the insecticide. Pour 25 ounces of insecticide into a bucket or watering can, fill it three-fourths full with water, then pour the solution around the base of the ash tree.”

      Applying the product by the end of April will allow plenty of time for the insecticide to be absorbed by the roots and moved up into the tree, he says.

      “Though we know this product works for healthy trees, we do not know when ash trees have been too damaged or infested for treatment,” Smitley says. “Trees with many dead branches and extensive dieback last summer and fall may not benefit from treatment.” 

      Smitley notes that only residents of southeastern Michigan living inside the infested area need to consider treating their ash trees. At this time there is no reason to treat ash trees outside of the infested area. The infested area includes the counties of Livingston, Washtenaw, Wayne, Macomb, Oakland and Monroe, and parts of Genesee, Jackson, St. Clair, Ingham and Lapeer.

MSU Evaluation of Insecticides to Control EAB Adults & Larvae
Summary of Research Conducted in 2003 .pdf

Emerald Ash Borer: What Are My Choices Now?

June 27, 2003 

    Some people just found out that ash trees in their neighborhood are infested with emerald ash borer.  What do you do now?  First, make sure that you have ash trees and not some other type of tree. Only ash trees will be attacked.  If you are not sure, contact your local MSU-Extension office for bulletin E-2892: ‘Distinguishing ash from other common trees’.  Second, insecticide treatments are not likely to help dying trees.  They will work best as preventive treatments to healthy ash trees.  Finally, if you have ash trees, emerald ash borer is going to be costly, no matter what you do.  Treating your trees yourself or paying an arborist to treat them will be expensive, and so is the cost of removing dead trees.  Trees located between the sidewalk and street may be removed by the city or township you live in, but you will have to pay for the removal of trees in your yard.  At this time, most infested ash trees are dying 1-3 years after dead branches are first found.  Remember, if you decide to treat your ash trees with insecticide, they will need treating each year. 

    Insecticide treatments options for July.  Insecticides will work best on trees with little or no borer damage.  It is unlikely that systemic insecticides applied as trunk injections, soil drenches, or soil injections will move very well in trees with extensive tunneling injury.  Trees with more than 20% canopy die-back usually have extensive damage that will be difficult to overcome. 

For Arborists or Landscapers:
1) Merit (imidacloprid) soil-injection or soil-drench.  Merit takes 4 – 8 weeks to be absorbed by the roots and moved up to the branches.  The best time for this was April and May.  We don’t know how well these treatments will work if they are applied now.

2)  Trunk injections of imidacloprid or bidrin.  We can’t say at this time which insecticide works the best.   The optimum time is probably late May and June, but they should still work in July, as long as the trees are healthy (the insecticides will not move well if there is a lot of borer damage to the trunk).  We know from our tests last year that trunk injections in late August and early September do not work well for trees already showing some canopy dieback.

3) Trunk and foliage sprays with Tempo (cyfluthrin), Talstar (Bifenthrin), Astro (permethrin), Sevin (carbaryl) or Orthene (acephate). The best timing for a trunk and foliage spray was probably last week (last week of June), when the adults started flying.   A second application in the middle of July will give added protection.  The idea is kill adults before they lay eggs, and to kill young larvae as they chew through insecticide-treated bark.  Since adults will be flying and laying eggs the next two weeks, a trunk and foliage spray should be helpful right now, even though some eggs have already been laid.  Trunk and foliage sprays will not help after mid to late July because most of the eggs will have hatched and the larvae will be under the bark.

For Homeowners:
1) Soil drench with Bayer Advanced Garden Tree and Shrub Insect Control (imidacloprid).  Best done in April or May.  We are not sure how well it will work when applied in July.  Homeowners mix product in a bucket of water and drench over the roots. Water the insecticide into the soil immediately after drenching by running a lawn sprinkler long enough to fill a bucket placed on the lawn under your ash tree, to a height of ½ to1 inch.
2) Trunk injections.  Cannot be done by homeowners themselves except for the Acecap product.  We do not know how well acecaps work for emerald ash borer.
3) Trunk and foliage sprays with Orthene or Sevin.  Homeowners can spray small ash trees themselves.  Trunk and foliage sprays can be applied to small trees with hand-pump sprayers, or garden-hose spray attachments.  Wear gloves, long pants, a long sleeve shirt, shoes and socks when applying any insecticide.  Avoid getting spray mist on your skin or breathing it.  Be sure to follow all label directions, and do not mix insecticides at concentrations higher than the rate on the label. See comments above about proper timing.
Arborists and landscapers usually do a much better job of treating trees (especially large trees) with insecticide than homeowners do, and homeowners cannot make trunk injections of imidacloprid or bidrin on their own. 
USDA Forest Service:
Michigan Department of Agriculture:
Michigan State University Extension:

How well do insecticides work for Emerald Ash Borer?
Rev. March 14, 2003

   Homeowners, landscapers and arborists would like to know if ash trees can be treated to protect them from the emerald ash borer.   Insecticides will probably work best as preventive treatments to healthy ash trees.  We do not know how well insecticide treatments will work on heavily infested trees already showing canopy die-back.  Trunk injections in August and September of 2002 to trees with more than 20% canopy die-back did not give good control of borers.  This is most likely because the cambium tissues were too disrupted from borer injury to allow adequate movement of the injected insecticides up the trunk.  Trunk injections may work better on healthy trees or trees with a low level of infestation. 

   Spring Treatments.  Insecticides applied in the spring will probably work best on trees with little or no borer damage.  We do not yet know if trees already damaged by borers will benefit from insecticide treatments in the spring, or at what point trees are too damaged to recover.  It is unlikely that systemic insecticides applied as trunk injections or soil injection will move very well in trees with extensive tunneling injury.  Trees with more than 20% canopy die-back usually have extensive tunneling injury that will be difficult to overcome, even if the trees are protected from further attack by trunk and foliage sprays.  We will be conducting more tests this coming year to see how well trunk injections in the spring, soil injections in spring, and trunk and foliage sprays in spring and early summer work. 

    We will be testing the same kind of strategies used for a closely related insect, the bronze birch borer.  We will be treating ash trees with:

1) a soil-injected systemic insecticide in April that is absorbed through the roots (imidacloprid), 
2) systemic insecticides injected into the trunk in May or June (imidacloprid and bidrin), or
3)  contact insecticides sprayed over the foliage, trunks and limbs on June 1st and July 1st to protect trees from the adult beetles that we expect will be active from late May to early August (cyfluthrin, bifenthrin, carbaryl or acephate).  Adult emergence information will be reported weekly in spring issues of the Landscape CAT Alert (order at: 
    Cultural Practices and Sanitation.  Ash trees in areas where the borer is active should be watered during dry spells to avoid drought stress.  Also, the removal of infested trees is desirable if it is feasible.  Next spring adult emerald ash borers will be emerging from infested trees.  The removal of infested trees this winter and early spring before the adults emerge will help reduce the population.  Trees must be chipped to pieces less than 1 inch-long, de-barked, or burned to prevent beetles from emerging. Just cutting the trees and stacking the logs as firewood will not kill the beetles.  If trees are going to be removed, cutting and chipping them before May 1st is desirable to prevent adults from emerging. 

 Table 1.  Products names for the insecticides mentioned in this bulletin. Please note that these products are for use in the landscape, and that products used in nurseries must have Worker Protection labeling. 

Chemical name      Product name(s)         _Applications_

Imidacloprid             Imicide                        Mauget tree injection
                                Pointer                      Wedgel tree injection
                                Merit                         Soil injection

Bidrin                   Inject – a – cide “B”         Mauget tree injection

Cyfluthrin                Tempo 2                       Trunk and foliage spray
                             Tempo 20 WP               Trunk and foliage spray

Carbaryl                 Sevin SL                       Trunk and foliage spray
                             Sevin 80 WSP               Trunk and foliage spray

Acephate           Orthene Turf, Tree and        Trunk and foliage spray
                          ornamental Spray 97%
                         Orthene Turf, Tree and        Trunk and foliage spray
                           ornamental Spray 75%

Bifenthrin              Talstar F                         Trunk and foliage spray
                            Talstar Lawn and Tree      Trunk and foliage spray

Note: The chemical insecticide treatment recommendations provided herein, are based on reasonably effective treatments made for other similar native borer insects we routinely attempt to manage in Michigan. Please consider that we have performed very little University-based research on the efficacy of insecticides on the emerald ash borer, a new exotic pest; hence, these recommendations are based only on conjectural information. We will keep you updated on any new information.

March 14, 2003 Addition:

Deb McCullough and I have been discussing the insecticide treatments we will by trying in our research tests this spring.  I just realized that Sevin SL has a section on the label (p. 6) for Direct Trunk Treatment to prevent bark beetle attack.  This is a higher concentration of carbaryl, designed for application to the trunk and limbs.  We will be testing this treatment for emerald ash borer along with several other insecticides this spring to see how well it works.  Meanwhile, landscapers and arborists should know that this is another spray option for emerald ash borer.  The idea is to soak the bark with a high enough concentration of Sevin SL to kill larvae after they hatch from eggs and begin to bore into the trunk. The label directions are as follows:

Mix 5 fluid oz of Sevin SL  per gallon (3.9 gal/100 gal).  Apply 1 gal of spray solution per 50 sq ft of bark prior to beetle attacks.  Treat all of trunk greater than 5" in diameter.  Do not repeat applications more than once every 6 months.

For emerald ash borer the best timing will be late May or 1st week of June.  We will be limited to one application according to the label.  Please note that this is a much higher application rate of Sevin than the foliar spray used for most ornamental pests (1 qt/100 gal).

F.A.Q.:  I deal with a lot of homeowners who are unlikely to call a tree service, but willing to go purchase an insecticide to apply themselves. In this latest update you didn't specifically mention soil drench applications as of the Bayer product. Can I assume your comments on soil injection apply also to drenching? Do we have specific information on effectiveness of drenching as opposed to tree injections?  Very good questions, Jennie. 

First, for professionals, Merit 75 WP can be applied as a soil drench as well as a soil injection.  I will see if we can post a specimen label.  It says on the label...  "Soil drench:  uniformly apply the dosage in no less than 10 gallons of water per 1000 square feet as a drench around the base of the tree, directed to the root zone."   The rate on the label is 0.7 to 1.4 level teaspoons per inch of trunk diameter (dbh) or 1 to 2 oz per 30 cumulative inches of trunk diameter (dbh).  The goal is to place the insecticide where it is best absorbed by the roots, so we want it in the top 6 inches of soil within the drip line of the tree, putting the most insecticide where the most roots are. 

Homeowners can purchase Bayer Advanced Garden Tree and Shrub Insect Contol,  containing imidacloprid.  The rate is 1 oz per inch of tree circumference.  I have no idea how much this will cost.  I have also been asked about what happens if a homeowner uses Bayer Advanced Lawn Season-long Grub Control  on their lawn, including under ash trees.  This product also contains imidacloprid, but it is not labeled for tree and shrub pests and will not work well for borers when applied for grubs because if it is applied correctly the area under your ash tree will only receive about 1/10 of the rate needed for borer control.

No matter how imidacloprid is applied to the soil, it takes some time to be absorbed by the roots and moved up to the foliage.  The label says that "translocation delay can take up to 60 days".  For EAB, we want the imidacloprid to be there in late April when the tree starts to move water and nutrients up to the branches.  We do not know at this time how well a late October application works compared with a late April application.

The last question was about protecting trees in areas where EAB is likely to spread into.  Protecting trees is a good idea anywhere that EAB adults may find them (assuming we have products that provide protection).   There is no need to treat ash trees in counties where EAB has not yet been found.  However, it is difficult to know where treatments will be beneficial in parts of infested counties just outside the known infested area.  Any trees within 0.5 to 1.0 miles of a known infestation are at risk next year.  As you get further away it becomes guess work because the early stages of infestation are not easily detected.  In those cases it is a personal decision whether or not to treat ash trees.  If you are more than 10 miles away from a known infestation, it is very unlikely that EAB adults will find your trees, unless there are infested trees nearby that nobody knew about. 

I hope this answers your questions,
Dave Smitley, Ph.D.
January 15, 2003

Above article is also available as a printable document (saved in pdf format)
Click to get: New Exotic Pest, Emerald Ash Borer & Management Update .pdf

   For more information about EAB and what homeowners can do, go to the website or contact your county MSU Extension office.

    Michigan has an active Emerald Ash Borer Task Force working to control and eradicate the pest and minimize its damage. Members include MSU, the Michigan departments of Agriculture and Natural Resources, and the U.S. Department of Agriculture Animal and Plant Health Inspection Service and Forest Service, in cooperation with local units of government and various industry groups, associations and universities.

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