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Emerald Ash Borer Invasion Threatens City’s Ash Trees

Invasive Species Raises Questions About Fiscal Responsibility of City Tree Choices
Emerald Ash Borers
Emerald Ash Borers were discovered in New Jersey for the first time in 2014. TotalLandscapeCare.com

NEW BRUNSWICK, NJ—Eighty-four percent of the trees proposed for Recreation Park are either non-native or at risk of succumbing to an invasive pest, according to a New Brunswick Today analysis.

In 2012, the City of New Brunswick laid out a plan to improve the park, located on Pine Street in the Second Ward.

The $2.3 million improvements include a skate park, community garden, multipurpose sports field and picnic area, as we reported.

According to a planting schedule provided by the city, 126 trees will be planted in the park, 42 of which are Ash trees.

Ash trees are in critical danger because of an Asian beetle known as the Emerald Ash Borer (EAB), pictured bellow.

One third of the planned trees are at risk. According to NJ Department of Agriculture, “Emerald Ash Borer was discovered in New Jersey in May 2014 in Somerset County. Infestations throughout the U.S. and Canada have killed tens of millions of ash trees since 2002”.

In 2015 the EAB has spread to Burlington, Mercer, Middlesex and Bergen County.

In order to counter this threat, the City of New Brunswick would need to apply pesticides. As a result ash trees become expensive to maintain.

If pesticides are not routinely applied, the trees may succumb within a few years of infestation. This makes them an undesirable choice because if they succumb to EAB they will need to be replaced by a hardier species.

What criteria should city officials use to choose trees for the new park?

One answer is ecological value. A good method of assessing it is by counting the number of Lepidoptera (butterfly) species each tree supports.

The University of Delaware published a ranked list of tree species on how they compare in terms of supporting lepidoptera. The more species a tree supports, the more valuable it is ecologically.

Trees are great hosts because they provide food in the form of foliage, pollen and nectar. According to their website “caterpillars are disproportionately valuable sources of food for many terrestrial birds, particularly warblers and neotropical migrants of conservation concern.”

Although Ash trees rank #18 on the list, supporting 149 species, it is susceptible to EAB. An environmentally responsible replacement could be any one of the species ranked higher: Oaks, Poplars, Maples, Willows or Birches.

Of the 126 trees scheduled to be planted in the renovated park, approximately 50% are non-native.

Non-native trees are correlated with supporting less lepidoptera species according to the University of Delaware's ranking. The non-natives include: 25 Norway spruce, 19 Kousa dogwood, 16 Yoshino cherry, and 4 Crape myrtle.

A possible substitution could be 23 Magnolia, 25 White pine, and 16 black cherry.

If left alone, the park could become almost empty of trees, and not reach its full potential in supporting native fauna.

Public land is at a premium in New Brunswick, and every tree counts.

The city is not isolated from nature, it is part of it. Planners and landscapers must be conscious of both pests that are a danger to purchased trees and what ecological value those trees have once planted.

The community benefits from having native species in private and public lands because there will be more pollinators and birds, according to city-based environmental advocates.

By virtue of being native, these species require less care because they have evolved with local pests, soil and climate.

although Ash trees are native to New Jersey and would normally be a good choice, they are an exception because EAB is an invasive pest.