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Emerald Ash Borer

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Above is an example of an adult emerald ash borer. Its true size can be seen in relation to the penny in the lower right.

Emerald ash borer larvae produce damage as shown in this sample at the Crawford County Administrative Building. (Photo by Ted Pennekamp)

 

Emerald ash borer has become a green 

menace in Wisconsin and Crawford County

By Ted Pennekamp

 

This third installment of a series of articles about invasive species in Crawford County focuses on a pest known as emerald ash borer (EAB). 

EAB was first detected in the county in April of 2009 and was confined to an area in the town of Freeman. It has since spread to the village of Gays Mills and the town of Utica. In 2013, EAB was in 15 counties in Wisconsin. It is now found in 41 counties.

“It doesn’t move really fast on its own,” said Gary Harden in 2013. Harden, who was the DNR Area Forester for Crawford County at that time, said, however, that EAB can move several miles very quickly if firewood or other ash materials are transported. 

The Wisconsin Department of Agriculture Trade and Consumer Protection is the lead agency regarding EAB, and the state DNR and the federal Animal and Plant Health Inspection Service also help to control the spread of the insect, which kills all ash tree species.

The three agencies continue to promote citizen awareness, continue to monitor evidence of EAB and continue to enforce quarantines. 

EAB is an exoctic pest native to Asia. The adult beetles eat ash foliage but cause little damage. The real damage is caused by the EAB larvae that feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients. It is suspected that the insect was introduced to the United States via solid wood packing material carried in cargo ships or airplanes originating in Asia. 

Crawford County is one of 41 counties in Wisconsin that is under federal quarantine regarding the transport of material such as firewood and industrial wood products. Nearby quarantined counties include Vernon County, Grant County and Allamakee County, Iowa. 

It is illegal to move firewood from a quarantined county into a non-quarantined county. Also, homeowners should avoid moving firewood any significant distance from the area that the wood originated from in order to further reduce the spread of EAB. No firewood from outside of Wisconsin is allowed in state parks. DATCP-certified firewood can be used in state parks regardless of the distance traveled.

Operations such as nurseries, mills and loggers, firewood producers and users, green lumber manufacturers, and pallet producers all are being regulated in some way regarding EAB. These operations were previously being regulated and are not generally considered to be a problem, according to a DATCP report.

The Wisconsin DNR says that statewide one in five community trees is an ash. The DNR has suggested that municipalities in Crawford counties should: 

•learn more about the pest

•estimate impacts and costs

•plan for wood utilization or disposal

•communicate with surrounding municipalities and the county government

•report possible or suspected EAB to the hotline, 1-800-462-2803 or use the EAB reporting form at www.emeraldashborer.wi.gov

•consider ash management options such as preemptive removal and pesticide treatment.

Preemptive removal of some trees can be an unpopular option, but the experience of other states clearly shows that waiting to remove ash trees until they are dead costs local governments more in the long run, according to the DNR.

An article written by R. Chris Williamson and P.J. Liesch, UW Entomology, and revised on May 9, 2016, which is featured on the University of Wisconsin-Extension website, states, “Several insecticide products are available to homeowners for control of emerald ash borer. Since the presence and infestation level of EAB is quite difficult to determine at early stages of an infestation, insecticide treatments may be merited to mitigate damage by EAB. However, not all ash trees should be treated as some may be too extensively compromised or in poor condition to receive treatment. Tree location, value, and health, as well as the cost of treatment are all factors to consider. Due to the expense of yearly insecticide treatments, one should consider the value of a particular ash tree in relation to insecticide treatment costs before making any treatments. In addition, consider the health of each tree before treating.  Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50 percent canopy thinning. Insecticide treatments are not suggested for trees with greater than 50 percent canopy thinning. Trees with greater than 50 percent canopy thinning should be removed and destroyed in accordance with established guidelines. For a more detailed discussion on this topic, see University of Wisconsin Garden Facts XHT1215, ‘Is My Ash Tree Worth Treating for Emerald Ash Borer’.”

Citizens should also become informed and should inspect their own ash trees. Excellent information can be obtained at www.emeraldashborer.wi.gov. If trees display any sign or symptom of EAB infestation, citizens should contact DATCP or the DNR. 

How Do I Know If My Trees Have EAB?

The visual symptoms associated with emerald ash borer infestations are nearly identical to those we often see on ash that are infested or infected by other ash pests and diseases commonly found in Wisconsin. 

For example, crown dieback can result from multiple stressors including drought stress, soil compaction or verticillium wilt just to name a few. Therefore, it is important to look for a combination of at least two or more symptoms or signs (see list directly below) when trying to determine the presence of emerald ash borer in your ash tree. If you see two or more of these please report your findings.

Symptoms

Crown dieback: Dieback of the upper and outer crown begins to occur after multiple years of EAB larval feeding. Trees begin to show dead branches throughout the canopy, beginning at the top. Larval feeding disrupts nutrient and water flow to the upper canopy, thus resulting in leaf loss. Foliage in the top of the tree may be thin and discolored. 

Epicormic Sprouting: Stressed trees will attempt to grow new branches and leaves where they still can. Trees may sucker excessively both at the base of the tree and on the trunk, often just below where the larvae are feeding. 

Bark splits: Vertical splits in the bark are caused due to callus tissue that develops around larval galleries. Larval galleries can often be seen beneath bark splits.

Woodpecker feeding: Woodpeckers feed on emerald ash borer larvae located under the bark. Feeding is typically evident higher in the tree where the emerald ash borer prefers to attack first. Large numbers of larvae under the bark can lead to woodpecker damage that looks like strips of bark have been pulled off of the tree. This is called “flecking.” 

Signs

D-shaped emergence holes: As adults emerge from under the bark they create an emergence hole - 1/8 inch in diameter and D-shaped. 

S-shaped larval galleries: As larvae feed under the bark they wind back and forth, thus creating galleries that are packed with frass and sawdust and follow a serpentine pattern.

Larvae: Larvae are cream-colored, slightly flattened (dorso-ventrally) and have pincher-like appendages (urogomphi) at the end of their abdomen. Mature larvae reach 1 1/2 inches in length and all larvae are found feeding beneath the bark. 

Adults: Adult beetles are metallic green in color and are 3/8 - 1/2 inch in length and 1/16 inch in width. Adults are flat on the back and rounded on their underside.

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