Emerald ash borer, an invasive insect that kills ash trees, has been detected for the first time in Marshall and Tama counties.

The Iowa Department of Agriculture and Land Stewardship made the announcement last week. That brings the total to 55 counties in Iowa where this pest has now been confirmed.

The two most recent discoveries were the result of a landowner who noticed telltale woodpecker damage on his ash trees, says Mike Kintner, state EAB program coordinator for IDALS. Further investigation by authorities resulted in the collection of EAB larvae from the trees. The detections in both cases occurred in a rural area north of the town of Le Grand.

Native to eastern Asia, EAB has decimated tens of millions of ash trees since it was accidently introduced in the U.S. in the Detroit area in 2002. First detected in Iowa in 2010, EAB has continued to spread. Since the beetle only travels short distances on its own, humans serve as the primary vector for expanding its range. The most common mode of transport for this pest is through movement of firewood. The Iowa EAB team strongly urges Iowans to use locally sourced firewood, burning it in the same county where it was purchased.  

Larvae tunnel under bark
EAB larvae kill ash trees by tunneling under the bark and feeding on the part of the tree that moves nutrients up and down the trunk. EAB-infested ash trees can include branch dieback in the upper crown, water sprouts along the trunk and main branches, vertical bark splits, D-shaped emergence holes, S-shaped tunneling under loose bark, and woodpecker damage.

If you suspect EAB entering your area, contact one of the following:

• Iowa Department of Agriculture, state entomologist office, 515-725-1470

• Iowa Department of Natural Resources, state officer, 515-725-8453

• Iowa State University Extension Entomology, 515-294-1101

If a landowner is interested in protecting a valuable and healthy ash tree within 15 miles of a known infestation, the treatment window for protecting an ash tree begins soon. Soil treatments should be made from mid-April to mid-May. Basal trunk sprays should be applied mid-May to mid-June. Trunk injections begin once the tree has a full canopy.

Full details are available in ISU Extension publication PM 2084. To learn more about EAB and view maps of its distribution, visit iowatreepests.com.

For information, contact Iowa EAB Team member:

• Mike Kintner, IDALS EAB coordinator, 515-745-2877, [email protected]

• Robin Pruisner, IDALS state entomologist, 515-725-1470, [email protected]

• Jeff Goerndt, DNR state forester, 515-725-8452, [email protected]

• Jesse Randall, ISU Extension forester, 515-294-1168, [email protected]

• Mark Shour, ISU Extension entomologist, 515-294-5963, [email protected]

• Laura Iles, ISU Extension entomologist, ISU Plant and Insect Diagnostic Clinic, 515-294-0581, [email protected]

• Donald Lewis, ISU Extension entomologist, 515-294-1101, [email protected]

• Jeff Iles, ISU Extension horticulturist, 515-294-3718, [email protected]

Team answers questions
The Iowa EAB Team provides information to frequently asked questions:

Should I be concerned about EAB? Yes. It kills ash trees, usually in two to four years. In the Midwest, millions of ash trees have been killed by EAB since 2002. There are about 3.1 million urban ash trees and 52 million ash trees in forests in Iowa. Statewide, Iowa averages 16% to 17% ash on city property, though the ash component in tree inventories can reach 87%.

How do I know if I have an ash tree in my yard? Two sources to check on tree identification are Common Problems of Ash Trees and Interactive Tree identification Key. 

How do I know if my ash tree is infested?  Look for the following symptoms:

• canopy thinning or dying branches in the top of the tree

• water sprouts (suckers) halfway up the trunk

• feeding notches on edge of leaflets

• woodpecker feeding sites with bark flakes on lawn

• S-shaped feeding galleries under dead bark

• D-shaped exit holes an eighth inch in diameter

Who should be thinking about treating ash trees? If you are a homeowner within 15 miles of a known infested area, you can consider treatment of a healthy ash tree during the growing season (see next question). If you are not in a known infested area, treatment may be premature.

If I am contacted by a pesticide applicator to treat ash trees for EAB in the fall or winter, what course should I take? The best time for most preventive applications for EAB is in spring. Some products can be used throughout the summer and early fall (before leaf color starts to change). If you live within 15 miles of a confirmed EAB-infested site, get an estimate for the treatment. It is best to get at least one additional estimate before any work is done.

What are EAB management options?  There are two management publications available from ISU Extension in English and Spanish.

Ash trees can be protected with insecticide applied by a commercial pesticide applicator or the homeowner. Trees must be healthy, vigorously growing and valuable to your landscape.

Most systemic insecticide treatments (imidacloprid and dinotefuran) must be done each year for the life of the tree. Two active ingredients will last for two years in a light EAB infestation: emamectin benzoate and azadirachtin. In heavy EAB infestations, only emamectin benzoate is effective for two years; azadirachtin must be injected every year.

There is a per-acre use limit for soil treatments and basal bark treatments; consult product label when planning applications. There is no per-acre use limitation for trunk injections.

ISU Extension does not recommend canopy sprays because of limited effectiveness, need for specialized equipment, spray drift and possible adverse effects to nontarget organisms.