As parasite threatens Maine’s ash trees, regulators weigh how to lessen damage

Fri, 04/02/2021 - 12:30pm

Maine regulators are considering a proposal to continue slowing the spread of the invasive emerald ash borer parasite that is killing the state’s ash trees. 

The new rules would expand the areas where Maine’s Department of Agriculture, Conservation and Forestry, or DACF, regulates the movement of ash products, and extend a ban on bringing materials from infested areas of other states and Canada into non-regulated parts of Maine. The rules would also lift restrictions on the movement of composted or uncomposted ash chips in all parts of the state. 

The proposal comes less than two months after the federal government lifted a quarantine on ash products in nearly two dozen states where the insect has been found. The U.S. Department of Agriculture called that approach ineffective and in January announced plans to use parasitic wasps  which kill the ash borer by laying eggs in or on those of the ash borer  to eliminate the invasive species. 

Maine officials argue wasps mostly protect young ash trees and cannot fully replace restrictions on the movement of ash products. The Bureau of Forestry issued an emergency order in January to extend the quarantine until stricter state rules could be adopted. 

“The parasitoid wasps are not a solution for the existing trees,” said Gary Fish, state horticulturist with the agriculture department. “They’re not nearly as effective on older trees as they are on younger trees.”

Fish explained that thin bark on young ash trees allows wasps to easily lay their eggs over emerald ash borer territory, while thicker bark on older ash trees is harder for the wasps to penetrate and parasitize. He also pointed out that wasps can’t be released until ash trees have been significantly damaged by emerald ash borers because the wasps need a food source to establish their population. 

“By the time you release the wasps, most of the trees are already destined to die,” said Fish. 

While emerald ash borer was first discovered in Michigan in 2002, Maine was able to keep the parasite killing ecologically and culturally sacred ash trees out of the state until it was discovered in Aroostook County in 2018.

Dr. John Daigle, University of Maine professor in the school of forest resources, credits Maine’s proactive quarantine rules, such as firewood restrictions, as the main reason for being able to fend it off so long. 

“It’s really been a big effort to try to control, as best as we can, the movement of infested firewood,” said Daigle. “It’s a direct result of the quarantine, and information and education that’s been sent to people.” 

Daigle and Fish both highlighted the cultural significance of black ash trees as part of the creation story for Wabanaki tribes of Maine and resource used for traditional Wabanaki basket weaving

“Losing ash will be a blow to a lot of aquatic and wetland organisms as well as an extremely large hit for the Native American populations in Maine,” said Fish. “We want to make sure for the future that we can basically control what might come across the border.” 

Ninety percent of ash trees in Maine are not in infested areas, but the parasite has been found across New England. Quebec and New Brunswick also have significant populations. While Cumberland, York and towns in the southwest corner of Oxford County have had emerald ash borer exposure, Aroostook County has been hit the hardest. 

The Department of Agriculture, Conservation and Forestry presented three options for expanding the quarantine in Maine’s northernmost county at a virtual public hearing March 16. The most conservative option expands the quarantine area by three towns, while the most extreme would add 36 towns and territories. 

The new rules would also no longer regulate the movement of chipped wood in areas under quarantine because regulators have deemed the practice as low risk. 

Administrators will collect and respond to public comments, and work with the DACF commissioner and attorney general to decide which option and potential rules changes will be best. 

If there are no comments that would change the proposal significantly, the new rules will then be sent to the secretary of state to be posted and will become effective five days later. 

Public comments can be submitted to or Gary Fish, Maine DACF – Horticulture, 28 State House Station, Augusta, ME 04333-0028 until 5 p.m. on April 2.