Emerald ash borer characteristics

Emerald Ash Borer (Agrilus planipennis)

The small Emerald Ash Borer Beetle has a justifiably bad reputation for destruction, radically deforesting neighborhoods in just a few years.

The Emerald Ash Borer is one in a line of destructive tree beetles in North America. As recently as June 2002, the beetle was identified in Windsor, Ontario and in the southeast portion of the state of Michigan. In less than a decade, it became a well-known problem insect. It is native to Asia, found locally in parts of Japan, the Koreas, China, Mongolia, and Russia. A few beetles likely hitched a ride on cargo during shipping and that is when trouble on the North American continent began.
The Emerald Ash Borer is a highly invasive species, capable of populating a large area in a very short period of time. It is also highly recognizable thanks to its metallic green coloring. The insect makes no distinction between wild areas and landscaped growth, attacking the leaves and bark of the Ash tree species wherever it happens to grow.
Emerald Ash Borers (EABs) are related to native species of North American tree borers. They all share some similarities in how they feed, mate, and otherwise operate in adulthood. Adults appear in the late spring months and into early August. One generation lives per year, but it can wreak havoc in little time if left unchecked. The adults that emerge from the tree trunks leave a small, visible “D” shaped hole in the bark of the Ash tree. They proceed to feed off of the tree’s foliage before mating several weeks later.
Upon mating, the female beetle can lay upwards of 50 to 100 eggs on the surface of the tree, allowing the larvae to easily begin boring into the tree once they are born. Larvae dig into the area just under the bark and continue boring tunnels while feeding on the sapwood inside the tree. This draining of tree fluids continues from the summer season into the fall. The death of the tree is caused by dehydration and starvation. The small tunnels block or destroy the xylem in the tree trunk which allows water to move up the tree. Ash trees that are infected and impaired will have seasons where only a few branch cluster grow leaves, while other parts are bare. Suffering Ash trees will try to grow new shoots from the base of their trunks in an effort to stay alive.
Ash trees offer a tremendous amount of natural beauty to neighborhoods. They are an important part of the temperate forest ecosystem and are harvested for use. Targeting the larvae is instrumental in stopping the spread of the Emerald Ash Borer, and the only known solution to stop them is the removal and destruction of all infected trees. This usually results in an entire neighborhood’s treescape changing because Ash trees were popular decades ago in urban and suburban planning. In many places, this species alone was planted for miles. Now block after block loses shade and character in an effort to stem infestations.
Quarantines of known infected areas and trees is currently ongoing throughout many states and provinces. It is thought that the presence of Woodpeckers might be an indication of infestation because Woodpeckers seem enjoy hunting the larvae under the bark. At this time, the EAB feeds only on Ash trees (known as Fraxinus spp.). If you suspect your Ash tree is affected, contact your local government to have the village/city look at your tree.

Emerald Ash Borer

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.


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 before. 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. .

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.

  • English:https://store.extension.iastate.edu/product/13114
  • Spanish:https://store.extension.iastate.edu/product/14762

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 2008 federal emerald ash borer Pest Alert is is available here.

More: 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.

Emerald Ash Borer May Have Spread to Different Tree

Adult Emerald Ash Borer

The emerald ash borer, which is destroying ash trees in a large swath of the nation, has apparently spread to a different tree, according to a researcher at Wright State University. Professor Don Cipollini has found that the invasive green beetle has apparently begun to attack white fringetree (Chionanthus virginicus).

White fringetree is native to the United States and grows wild from New Jersey south to Florida and west to Oklahoma and Texas. It is also a popular ornamental tree that has been planted in other parts of the country.

“It appears that emerald ash borer is eating more than ash trees,” Cipollini said. “It may have a wider host range than we ever thought in the first place, or it is adapting to utilize new hosts. This biological invasion is really something to worry about. It’s having drastic ecological and economic consequences, and you can’t always predict what’s going to happen.”

Native to Asia, emerald ash borer was introduced to the United States near Detroit in 2002. It is believed to have been in ash wood used to stabilize crates during shipping.

So far, the insect has spread in all directions, killed tens of millions of ash trees and threatens to kill most of the 8.7 billion ash trees throughout North America. It is estimated that the borer will have caused $10 billion in economic damage by 2019.

The borers attack trees by laying eggs on the bark. The serpentine feeding galleries of the larvae inside the bark disrupt the flow of nutrients and water and starve the tree.

There are efforts to try to save ash trees from the borer. Pesticides can be injected into the trunk or poured into the soil around the tree and taken up by the roots. And there have been releases of parasitoid wasps.

“But it’s hard to stop this thing because the borer has reached such high densities,” Cipollini said. “And it is now spreading to parts of the country where white fringetree grows.”

White fringetree, a relative of ash, is a deciduous shrub or small tree that can grow up to 30 feet tall. It has white flowers and a purple, olive-like fruit. It is known for its relative lack of pest and disease problems and has never been reported as a host to wood borers related to emerald ash borer.

Cipollini, who has studied emerald ash borer for nearly 10 years, has been working with colleagues to come up with new strains of ash trees that would be resistant to the insect. With colleagues and students, he has co-authored seven publications on the insect, with several others in review or preparation.

He discovered that borers were also attacking white fringetree in August when he acted on a hunch.

Cipollini was examining some white fringetrees that had been planted by the Yellow Springs Tree Committee near his home in the southwestern Ohio village when he spotted a telltale borer exit hole with the characteristic “D” shape on one of the trees.

“I walked up to the tree, saw the hole right in front of my eyes and said, ‘Oh my gosh, there it is,’” he recalled.

He got permission from the committee to peel back the bark, discovered what appeared to be the typical feeding gallery of emerald ash borer and determined that attacks on this tree had begun at least two years earlier. He later found similar infestations in another white fringetree in Yellow Springs, one at Cox Arboretum in Dayton and one at Ferncliff Cemetery in Springfield.

Cipollini collected the larvae, took them back to his lab and put them under the microscope. The larvae were consistent with those of emerald ash borer — from the bifurcation of the pronotal groove to the abdominal segments becoming increasingly trapezoidal.

“Based on the larval morphology alone, I’m confident that this will turn out to be emerald ash borer,” he said. “There was a good paper that was published two years ago describing the physical characteristics of emerald ash borer larvae, and this meets those that I can determine. If it turns out not to be emerald ash borer, it has to be a close relative and likely non-native. And so it would still be a concern for the same reasons as emerald ash borer.”

Later Cipollini was able to exhume part of a dead adult beetle from the tree that failed to emerge two years ago. This specimen also exhibits key characteristics of adult emerald ash borer, he said.

He then sent photos of the larvae and a larval specimen to experts at the Animal and Plant Health Inspection Service (APHIS), an arm of the U.S. Department of Agriculture. Cipollini was told the larvae in the photos appeared to match those of emerald ash borer. The same is being done with the adult specimen in order to confirm its identity.

APHIS, which investigates invasive species that impact agriculture, horticulture and forestry, would be the agency that would quarantine white fringetree to try to control the spread of the borer.

“Wild populations of this tree, along with horticultural specimens, are now seemingly under threat like ash trees are,” Cipollini said.

Cipollini quickly wrote up a short paper on his discovery and sent it to the Journal of Economic Entomology, one of the Entomological Society of America’s main publications. The editor asked Cipollini to conduct DNA tests on the larvae to further confirm its identity, which he is currently doing. He also plans to rear additional adults from infested wood to confirm their physical characteristics.

Cipollini is scheduled to present his findings to APHIS officials and researchers at an emerald ash borer research review meeting on the Wooster campus of The Ohio State University on Oct. 15.

Cipollini said that if the emerald ash borer destroys white fringetree, the birds, insects, and other wildlife dependent on the tree’s leaves and fruit may also be threatened.

“It’s one of these unexpected consequences of biological invasions,” he said. “Even when you think you have a handle on something and you understand what it does and what it may cause, these kinds of surprises pop up.”

Cipollini said the threat to white fringetree is the latest example of the narrowing of the plant ecosystem, which provides humans with such things as fuel, water purification, and erosion control.

“It gets harder and harder for Mother Nature to handle that for us as you further and further reduce the pool of species that are present and their abundance,” he said.

Read more at:

– Wright State researcher finds emerald ash borer may have spread to different tree

Host Preference, Nutrition, and Defense

Research Issue

The emerald ash borer (EAB) has killed hundreds of millions of ash trees in North America since its discovery in 2002. All eastern North American ash species are susceptible to EAB including green, white, black, blue, and pumpkin ash. Asian ash species in EAB’s native range appear to have some level of resistance. Susceptibility and preference vary among North American ash species, with green ash being highly preferred and susceptible and blue ash much less preferred and susceptible. Many factors may contribute to host preference and suitability including physical qualities of the host (e.g., bark roughness, leaf texture), host volatiles, nutritional quality of the host, and the presence and abundance of defensive mechanisms and compounds.

Our Research

We conducted EAB feeding choice experiments with leaves from different ash species presented to EAB in cages in order to determine EAB preference for different species of ash. We collected and analyzed volatiles from ash trees of different species and compared their volatile profiles related to EAB feeding preference. Leaves and phloem were sampled and extracted for chemical analysis to elucidate differences in nutritional and defense chemistry of different ash species and examined their roles in EAB preference and performance.

Expected Outcomes

Understanding host preferences by EAB is important in prioritizing survey and management of different ash species. Discerning the mechanisms of host preference and resistance will be critical for incorporation into ash breeding programs to develop resistant trees.

Research Results

Although beetles consumed every ash species offered to them, Manchurian ash and blue ash were significantly less preferred than green ash, white ash and black ash while European ash was intermediate. The overall volatile profiles of different ash species differed significantly in their relative amounts of antennally active compounds. Moisture content and nutrients were important selective forces in feeding behavior of EAB larvae. Improved nutrient balance (total nitrogen/total non-structural carbohydrate ratio) and increased efficiency of amino acid utilization in green ash may contribute to its preference by EAB. Elevated levels of volatile compounds induced by adult foliar feeding in green and white ash, and lower levels of induced defensive compounds including phenolics and protease inhibitors in green ash, may also partially explain the preference for green ash by EAB. Negative effects of defense compounds might be alleviated by high nitrogen levels and by direct excretion or enzymatic conversion of defense compounds.

Chen, Y.; Ciaramitaro, T.; Poland, T.M. 2011. Moisture Content and Nutrition as Selection Forces for Emerald Ash Borer Larval Feeding Behavior. Ecological Entomology 36: 344-354.

Chen, Y.; Poland, T.M. 2010. Nutritional and defensive chemistry of three North American ash species: possible roles in performance by emerald ash borer adults. The Great Lakes Entomologist. 43: 20-33.

Research Participants

Principal Investigators

  • Yigen Chen, University of California at Davis (formerly at Michigan State University)
  • Therese Poland, US Forest Service – Northern Research Station Research Entomologist
  • Deepa Pureswaran, Natural Resources Canada Research Scientist
  • Tina Ciaramitaro, US Forest Service – Northern Research Station Biol. Lab. Tech.

Research Parthers

  • Enrico Bonello, Ohio State University
  • Justin Whitehill, Ohio State University

Last Modified: 03/14/2016

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