By John Kmitta
As mentioned in the March issue of Arbor Age, university researchers and extension specialists, tree and land care company representatives, non-governmental organizations, municipal arborists and foresters, and providers of management solutions recently joined together as the newly formed Coalition for Urban Ash Tree Conservation (CUATC). Their goal is to clarify misconceptions about emerald ash borer (EAB) management options and bring a unified voice to EAB management strategies.
Since the forming of CUATC, members of the coalition have been working toward their goals by hosting seminars and providing additional support.
“A lot of communities didn’t realize that ash was one-third of their trees,” said Dr. Joe Chamberlin, field development manager, southeast, for Valent Professional Products. “We wanted to get together the leading researchers and arborists. The primary message is not that you should go out and treat all of your trees or that you should use one particular product, but rather that you should incorporate an overall management program.”
At a recent seminar titled “Management Strategies for Emerald Ash Borer,” Dr. Fredrick Miller of Joliet (Ill.) Junior College and the Morton Arboretum (Lisle, Ill.), presented a range of topics related to EAB management, including the life history of EAB, the overall condition of forest resource, the pros and cons of ash phloem reduction (cutting of trees), the pros and cons of insecticide treatment, and the impact of doing nothing at all.
EAB is present in 15 states plus Ontario and Quebec, and attacks North American ash species (green, white, blue and black). There is usually one generation per year, but can extend to second season. According to Miller, signs of EAB infestation include epicormic branching, woodpecker activity, D-shaped emergence holes, and thin crowns on well-established trees.
Miller urges arborists to know the condition of their forest resource. This involves a comprehensive tree inventory including species composition, age classes, pests and diseases, hazard trees and overall tree health. “If I’m going shopping, I need to know what’s in my pantry,” said Miller.
According to Miller the ideal composition of the forest resource is no more than 30 percent from a single plant family, no more than 20 percent from a single genus, and no more than 10 percent from a single species. There should also be an even distribution of young, middle-aged and mature trees.
Arborists should also know their EAB population dynamics, including distance to the nearest known infestation, what adjoining communities are doing about EAB, what the EAB pressure is in their area and adjoining areas, and whether homeowners would be willing to treat their trees.
Removal, treatment, or nothing at all?
Miller outlined the pros and cons of ash phloem reduction (systemic removal of all public ash trees). On the plus side, ash phloem reduction results in less phloem resource, allows for replanting, reduces risk of hazard trees, and can be more efficient. But, on the flipside, it is costly and often not feasible, it results in the loss of tree benefits, it has shown — in areas such as Michigan — to be an ineffective management option, and ash phloem reduction of public trees does not take into account any private trees.
With regard to chemical management (i.e., the preventative and curative treatment of ash trees), arborists need to evaluate several factors:
Do residents value their trees?
Age class distribution
Are there legacy or high-value trees I want to preserver?
Pesticide limits of community
When should I begin treating?
Can I afford to treat?
Will treatments be applied in house or contracted out?
What are the best application techniques?
What products should I use?
According to Miller, trees that should be considered for treatment include mature trees in good health and high-value trees in prominent locations. Trees that should be considered for removal include ash trees in poor health and trees with utility or infrastructure issues (i.e., limited growth space). “Insecticides can be effective on protecting ash trees from EAB,” said Miller. But unnecessary chemical treatments are wasteful, he added.
Said, Chamberlin, “Treatment works. There are three EPA-registered insecticides — dinotefuran, imidacloprid and emamectin benzoate. No one product is best.”
According to Chamberlin, dinotefuran is ideal for first year of a treatment program after leaf-out, imidacloprid is a good early preventative before leaf-out, and emamectin benzoate works well for high-profile trees.
“Emamectin benzoate is the only product effective for more than one year with a single application,” Miller added.
According to Miller, application methods include basal soil drench, granular application, root flare injection, trunk injection and basal trunk spray. Soil drench and injections are most effective when made at the base of the trunk. Soil injections should be no more than two to four inches deep and made with moist soil. Miller recommends a 9 a.m. to 3 p.m. application timeframe (after that, the tree shuts down). He also recommends treating on clear days that are approximately 75 degrees with a light breeze.
When it comes to the cost benefit of removal versus treatment, Miller urges arborists to do their own calculations. But, for example, Miller roughly estimates removal, disposal and stump grinding at $500, plus replacement and replanting costing approximately $200, which brings the total to $700. By comparison, annual treatment at $20 year for 25 years equals $500 per tree.
Those who decide to do nothing at all are faced with infested trees that will eventually die, delays with regard to replanting, the loss of tree benefits, the potential for property damage, and the potential for lawsuits.
According to Chamberlin, the core messages are that an integrated approach is best (i.e., remove and replace plus treatment and conservation); tree removal does not slow EAB spread; ash conservation makes sense for healthy trees, and municipal trees are not the same as private trees.
For more information, and additional resources, visit the following:
“Insecticide Options for Protecting Ash Trees from Emerald Ash Borer”: www.emeraldashborer.info/files/multistate_EAB_Insecticide_Fact_Sheet.pdf
Purdue University Emerald Ash Borer Cost Calculator: http://extension.entm.purdue.edu/treecomputer
Legacy Tree Project: www.legacytreeproject.com