Emerald Ash Borer

Emerald ash borer (EAB) is a non-native, invasive insect from Asia that kills ash trees.  It was first discovered in the United States during the summer of 2002 near Detroit, Michigan. EAB has quickly become one of the most destructive and costly forest insects in urban forest history. In late 2015 it was discovered in Duluth, with indications it was here several years prior. Ash was a very popular replacement tree to plant after Dutch elm disease. In Duluth alone there are over 50,000 ash trees in maintained areas.

EAB lifecycle and how is spreads [video]

EAB status map [website]

Emerald ash borer (EAB) has been shown to kill essentially 100% of ash trees not chemically treated. This means there are two options for them, treatment (protecting them), or removal.

Treatment

We recommend that residents consider protecting large, well-placed, healthy ash trees. Treating an ash tree is more cost-effective than removal, plus maintains the tree benefits and value of a mature tree to your property. 

In order to be considered for treatment a tree should:

• Be 10" or greater in diameter.
• Not be competing with other trees or infrastructure.
• Show no more than 30% of canopy decline if an infestation is suspected.

Removal

Based on other areas which have already experienced the invasive bug, it infests all ash trees in a community within about 10 years after the initial infestation (in Duluth 2015 or earlier).

We do not recommended immediately removing all ash trees you do not plan to treat, but you should prepare for it.

• It is more expensive to remove a dead tree than a living one.
• Keep a close eye on your ash trees since EAB-infested trees can go from looking a little thin to dead in a year or two.

Contact us with questions on treatment or removal.

How long will I need to treat my ash tree?

Emerald ash borer’s population is expected to rise and fall in our area over a period of approximately 10 to 15 years; there are a lot of variables which may effect this, but based on other regions it is our best estimate.

Ash trees will need to be treated every two years (using emamectin benzoate) during this time. After all of the non-treated ash trees have died, EAB's food source will be limited, reducing its population. At that point, the intervals necessary between treatments will likely increase to four to six years, depending on pest conditions.

What is the treatment and is it safe?

There are several chemicals on the market to protect ash trees against EAB. That being said, there is a varying amount of chemical exposure, cost, and overall protection offered by each product. We use a trunk injection of emamectin benzoate due to its limited chemical exposure and proven effectiveness. 

There are increasing and well-warranted concerns regarding the overreliance on pesticides. Neonicotinoids (a class of insecticide) can have negative effects on non-target species, such as bees and other pollinators. Soil-applied products also have the potential to reach storm or ground water. 

The pesticide emamectin benzoate is not a neonicotinoid. It is a systemic insecticide injected directly into the trunk of the tree, which minimizes its non-target effects. Ash trees are wind pollinated; they are not a substantial nectar source for bees, they flower early in the growing season and only for a limited number of days. According to research conducted at Purdue University, “It is highly unlikely that bees would be exposed to systemic insecticides applied to ash.*” Emamectin benzoate has a low toxicity rating for mammals, a low bioaccumulation potential within ecosystems, and is immobile in soil. This means that the insecticide will not build up levels within an ecosystem and will be minimally harmful to people and animals that might encounter tree debris. 

While there are valid concerns regarding the overuse of pesticides in our environment, those concerns should be aimed at reducing pesticide use where fewer benefits result. The known environmental consequences of losing thousands of ash trees are vastly greater than the minimal risk associated with inoculating ash trees to protect them from certain death. 

For more information please see:

* Frequently Asked Questions Regarding Potential Side Effects of Systemic Insecticides Used To Control Emerald Ash Borer  [PDF]

Don't move ash (or other hardwoods) 

There is a quarantine on St Louis County, which means there are restrictions on public transport of hardwoods to a non-quarantined area. More information can be found here: City of Duluth [website] or the Minnesota Department of Agriculture [website].

For additional homeowner resources see:

Minnesota Department of Agriculture Homeowners Page  [webpage]

City of Duluth [website] 

How do I know if I have an ash tree? [PDF]