ISSUE 1   May 10, 2007

EMERALD ASH BORER UPDATE

Exotic (non-native) tree pests are among the greatest threats to forest and shade trees of North America. The emerald ash borer (EAB) is a devastating insect pest of ash trees that has drawn regional and national attention in recent years. Native to eastern Asia, the insect was first discovered near Detroit MI in 2002. Scientists believe that it was unintentionally brought into the U.S. through infested ash crating or pallets. Since its initial discovery, the insect has been found in southeast Michigan, adjacent Ontario (Canada), and several counties in Ohio, Indiana, and Maryland. Two new infestations were detected near Chicago, IL in 2006.

The damage caused by this pest has been astonishing. Unlike native ash-boring beetles that only kill weakened and dying trees, EAB attacks all ash trees regardless of their vigor, size, or age. Nearly 25 million ash trees have been destroyed by the insect to date.

Quarantines have been imposed in infested areas to restrict the interstate movement of regulated materials and prevent the spread of the insect to un-infested areas. Materials regulated by the quarantines include firewood, nursery stock, green lumber, and other living or dead ash material. In addition, eradication efforts have been employed to eliminate the insect from new infestations once they are found outside of quarantined areas. Unfortunately, eradication of EAB appears to be a losing battle as the high cost and difficulty in detecting the beetle early before it spreads has hindered this effort.

Emerald Ash Borer adult
Emerald Ash Borer adult
(D. Cappaert, MI St. Univ.)

If the EAB becomes established in North Dakota, the impacts will be overwhelming. Green ash is one of the most abundant species in the North Dakota’s forests and woodlands. Similarly, ash species and cultivated varieties are some of the most common within the state’s community forests and rural tree plantings. The cost of removing dead ash trees would be a huge financial burden to city governments. The loss of ash within riparian forests would negatively impact water quality and wildlife habitat. In addition, the loss of ash within the state’s farmstead and field windbreaks would have a considerable effect on rural residents.

The insect completes the juvenile portion its life cycle beneath the bark of ash trees and logs. Often, infested trees and logs may show no obvious external symptoms of infestation. When infested material is moved to a new location, the adult insect emerges and seeks new ash trees to attack. Consequently, a shipment of infested ash trees arriving in North Dakota or a person bringing a load of infested firewood into the state could introduce the pest at any time. The nursery industry has been cooperative with the restrictions placed on the shipment of ash plant material and few North Dakota nurseries receive ash from states near the quarantined areas. The transport of firewood by campers, sports persons, and firewood dealers has emerged as the most important spread of EAB as the regulation and enforcement of this mode of spread have been limited.

Although the EAB is still several states away, all North Dakotans must take action now to help prevent the spread of this beetle into the state. Adequate techniques to manage this pest are currently lacking and the sole cost-effective choice is to remove and destroy infested trees. Therefore prevention of its arrival into the state is the only realistic option. If its arrival can be delayed for one or more decades, the tools needed to manage this pest effectively might exist and some of North Dakota’s ash resource will be spared. All citizens can help stop the spread of this insect into our state. If someone you know is planning a trip to North Dakota, tell them to leave their firewood at home and only use local firewood sources.

Emerald Ash Borer galleries
Emerald Ash Borer galleries
(Art Wagner, APHIS-PPQ)

In addition, North Dakotans are encouraged to incorporate diversify into tree plantings. There has been an over-reliance on the use of ash over the past 2 decades and now there is an overabundance of ash in our communities and rural tree plantings. As such, these plantings are at risk to EAB. As a rule, diverse tree plantings are more resilient to damaging factors (including climate, insects, diseases, etc…). Tree species selection should not hinge on substituting one single species for another, but rather, diversifying the overall species composition of the planting. That is, don’t put all your eggs in one basket.

Lastly, stay current with the status of this pest. The emerald ash borer website (www.emeraldashborer.info) is the best location to find current information about EAB.

Michael Kangas
Forest Health Specialist
North Dakota State Forest Service
Michael.kangas@ndsu.edu


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