Emerald Ash Borer (FAQ)

What is the emerald ash borer?

The emerald ash borer (EAB) is an invasive wood-boring beetle that attacks and kills ash trees.  Since its discovery in North America in 2002, EAB has killed hundreds of millions of ash trees in North America and cost municipalities, property owners, nursery operators, and forest products industries hundreds of millions of dollars to remove, replace or treat ash trees.


Where has the emerald ash borer been found in Iowa?

Emerald ash borer was found in Iowa for the first time in 2010. Since then it has been found in over three-fourths of Iowa's counties.  Just because an infestation was found in a county does not mean the entire county is infested.

Where is the emerald ash borer currently found in the U.S.?

Borers were first detected in June 2002, though they most likely arrived there 10 to 12 years before. Click to see the current U.S. distribution map.

What are the signs and symptoms of EAB in ash trees?

See Michigan State University Extension Bulletin E-2938 for details. Infested trees have canopy thinning or dying branches in the top of the tree, epicormic sprouts (suckers) growing from the trunk, and flecking of bark by woodpeckers.  Confirmation is made by finding larvae in winding, s-shaped tunnels just under the bark.

What do emerald ash borers look like?

Adult emerald ash borers are bright metallic green in color with very short antennae. They are ½ inch long and one-eighth inch wide. Emerald ash borer larvae are creamy-white in color and have flattened segmented bodies. Older larvae grow up to an inch long. 

Where did the emerald ash borer come from?

The natural range of this beetle is northern China, Korea, Japan, Mongolia, and eastern Russia. Based on literature records, the emerald ash borer had never been found outside Asia. It is not considered a major pest of ash trees in its native region.

How did the emerald ash borer get to the United States?

Although no one knows exactly how the insect gained admittance to our country, it most likely arrived in solid wood packaging materials that originated from Asia. This could include ash wood used for crating, pallets, or stabilizing cargo in ships.

What types of trees does the emerald ash borer attack?

In North America, it is found in ash trees. Green, white, black, blue, pumpkin, Marshall seedless, Autumn Purple, and Summit are examples of susceptible species and cultivars. Ash trees in any setting (forest, landscape, woodlots, or fencerows) have been affected in infested areas. Branches as small as 1-inch diameter to trunks exceeding 2 feet in diameter have been colonized by this beetle.  Recently, EAB was also found to attack the white-fringe tree.

What happens to infested ash trees?

photo of tree with crown dieback and epicormic shoots due to EAB
Trees infested with EAB develop thin crowns, dead branches, and epicormic shoots on the lower part of the tree.

Tunnels excavated by feeding larvae destroy the water and nutrient-conducting tissues under the bark; this effectively starves the ash tree. The canopy of heavily infested trees will begin to die, usually near the top and progressing downward. Sometimes, infested ash trees produce epicormic (“water”) sprouts on the trunk or branches below emerald ash borer activity. The bark may crack directly over larval galleries. Adult beetles chew characteristic “D”-shaped exit holes as they leave former feeding sites below the bark. Woodpeckers often are found on infested ash tree trunks, feeding on larvae; this is most often noted during winter. Trees attacked by the emerald ash borer die within 1-3 years.

How does the emerald ash borer spread to new areas?

Adult beetles move slowly through the landscape, possibly one mile per year. However, humans can spread this exotic insect long distances by moving infested, firewood, logs, and nursery stock to un-infested areas. 

What has been done to limit the spread to new areas?

Education efforts such as "Buy It Where You Burn It" have attempted to impress upon the public the importance of not moving firewood or logs out of infested areas.  Federal and state quarantines in effect throughout Iowa and the U.S. regulated movement of ash logs, ash chips and mulch, and all hardwood firewood across quarantine borders indicated by blue lines on the U.S. distribution map.  Regulated items could not be legally moved outside of the quarantine area without permits, certificates, or compliance agreements.  

In late 2020 the USDA-APHIS removed the federal domestic EAB quarantine regulations after concluding that the domestic quarantine had not proven effective in stopping the spread of EAB.  

What is the life cycle of the emerald ash borer?

Adults are present from mid-May through late July and feed on ash leaflets. Following mating, female beetles lay eggs (average 60 – 90 per female) in bark cracks. Tiny white larvae hatch from eggs within one week and then bore through the bark and into the cambium. Larvae feed under ash tree bark from mid-summer through the next spring, producing “S”-shaped tunnels. Pupation occurs in spring and the new generation of adults emerges shortly thereafter. It is generally considered that the emerald ash borer completes a generation in one year. However, reports of a generation requiring two years to complete development have been made when the host tree was vigorous and apparently healthy.

Is there any known natural resistance in ash trees to the emerald ash borer?

Unfortunately, no observations of host plant resistance in the ashes have been reported. In its native range, the emerald ash borer is considered a major pest of ash trees. Research in that compared American species/cultivars with Asian ash species observed fewer emerald ash borer larval tunnels on Asian species, but the results are preliminary. All of the trees had been damaged to some extent by this insect.

Are there any natural enemies of the emerald ash borer?

Yes, scientists have observed parasitic wasps attacking the egg or larval stages of the emerald ash borer in its native land. Efforts are underway to introduce these wasps to North America to supress these beetles. Unfortunately, this process is time-consuming and will not eradicate EAB.  Natural enemies may reduce EAB populations and aid in slowing the spread.

What should I do with my ash tree now that EAB is in Iowa?

There are three strategies to consider if you have an ash tree in your landscape.  You can do nothing and wait and see what transpires; You can remove a failing/declining ash tree and replace it with another species, or you can use preventive insecticide treatments to preserve and protect your ash tree.

What are the EAB insecticide treatment options?

Detailed information on emerald ash borer management options are contained in two publications available from Iowa State University Extension & Outreach.

See also the multi-state guide, "Insecticide Options for Protecting Ash Trees from Emerald Ash Borer."

Be wary of sales gimmicks

If individuals or companies offer cures or preventive treatments for emerald ash borer, thank them for their interest and ask them to leave your property. If someone approaches you and claims that the state has ordered your ash trees to be removed and then offers to cut them down for a price, record the person’s name and contact information and pass it on to the IDALS – State Entomologist Office at (515) 725-1465. 

If I remove my ash tree, what should I plant to replace it?

Many other shade tree species can be planted to replace an ash tree.  Consult this publication for alternatives for ash: Shade trees for Iowa – Ash Alternatives (FOR406)

Do I have to treat or chip the wood from a removed EAB infected tree?

Ash trees infected with EAB do not need to be treated or chipped when removed.  If you do plan to keep the wood for campfires or fireplaces use it on your property and do not transport the wood to new locations.  Any firewood brought indoors (especially the first year after being cut) can have EAB beetles emerging in the house.  The EAB that emerge indoors will not infest any items in the home and will not live long.  They will likely end up near windows where they can be vacuumed and removed.  Do not treat firewood with insecticides. 

Additional Information

2008 Federal Emerald Ash Borer Pest Alert.

Iowa Tree Pests - Emerald Ash Borer Homepage - IDALS

Do you live in Iowa and have an insect you would like identified?

The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them.  Please see our website for current forms, fees, and instructions on preserving and mailing insects.   

Contact information for each state's diagnostic laboratory for U.S. residents.  If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.