Emerald Ash Borer

Encyclopedia Article

Frequently Asked Questions

What is the emerald ash borer?

It is an insect that belongs to a group of metallic wood boring beetles. These insects normally serve to kill weakened trees, a part of the natural nutrient recycling scheme. However, emerald ash borers kill vigorously growing or weakened ash trees.

emerald ash borer adult beetle is one-half inch long.
EAB Adult Beetle

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 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?

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. Adult feeding (removal of tissue along leaflet edges) can be seen on affected ash trees. 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.

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

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

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 half of Iowa's counties.  Just because an infestation was found in a county does not mean the entire county is infested.  Click to see the current Iowa distribution map.

How does the emerald ash borer spread to new areas?

On its own, the beetle moves slowly through the landscape, approximately one mile annually. However, humans can greatly accelerate the spread of this exotic insect by moving infested nursery stock, firewood and logs to un-infested areas. Emerald ash borer movement into parts of Michigan outside of the Detroit area, Ohio, and Indiana has been the direct result of moving these ash products.

What is being done to limit the spread to new areas?

Federal and state quarantines are now in effect throughout Iowa and the U.S.  Quarantine borders are indicated by blue lines in the U.S. distribution map linked above.

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 determine if these wasps can be introduced to America to control these beetles. Unfortunately, this process is time-consuming and may not be available to current eradication and containment efforts. A fungus (Beauveria bassiana) has also been tested as an adult beetle “natural insecticide”; tentative results have showed moderate success.

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 insecticides 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.

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. 

Additional Information

The federal emerald ash borer Pest Alert is is available here.

More:  www.extension.iastate.edu/psep/EmeraldAshBorer.html

www.iowatreepests.com/eab_home.html

 

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 states 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.  

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