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EAB Update – September 2015

EAB Update
City and County of Boulder surveys for emerald ash borer (EAB)-infested ash trees continue for the 2015 season.  EAB has been confirmed in grids covering an area of 15 square miles within the City of Boulder (no change since August 2015).*The Colorado EAB Response Team is comprised of members from the following agencies/organizations: Boulder County, City of Boulder, Colorado Department of Agriculture, Colorado State Forest Service, Colorado State University Extension, Colorado Tree Coalition, Green Industries of Colorado, University of Colorado and USDA Animal and Plant Health Inspection Service.
To date, EAB has not yet been detected outside of the Boulder City limits.

EAB was originally detected in Colorado in the fall of 2013.  Delimitation surveys initiated in 2013 followed a scientific protocol developed by the Canadian Forest Service.  Subsequent surveys initiated in 2014 and 2015 target ash trees exhibiting symptoms of decline.

Many ash trees all over the state of Colorado are in poor condition due to freeze, drought and other environmental conditions.  Ash pests such as lilac ash borer, ash bark beetle and other boring insects are much more common than EAB. Web Site Updates

Take a look at the website.  Boulder County’s newly- approved EAB Management plan is linked along with their new website.

Colorado Emerald Ash Borer Myths

September 23, 2015, will mark the two year anniversary of the detection of emerald ash borer (EAB) in Colorado.  It is estimated that the insect was present in Boulder for at least 4 to 6 years prior (2007 – 2009) to its detection in 2013.  Efforts to detect EAB and ‘find the edge’ of the infestation continue to dominate the efforts of those responding to the invasive pest.  But the insect has proven to be very difficult to find in the early stages of infestation, frustrating those of us who work in arboriculture, pest management, diagnostics, and support sustainable urban landscapes.  As such there is much confusion and misinformation circulating regarding EAB.  It’s time to set the record straight.

Myth #1 – All declining and dead ash in Colorado must have emerald ash borer.

This statement is far from true.  Many ash all over the Front Range are exhibiting symptoms indicating signs of distress, which include the tiny clusters of new growth, thinning of the canopy (dropping leaves), suckering or growth of stems and leaves at the base of a tree, splitting of the bark and signs of boring insects.

There are many boring insects that affect ash.  The most common insects causing holes in the bark of ash trees are lilac ash borer and ash bark beetle.  It has been surprising to tree experts at how much damage lilac ash borer, ash bark beetle, and other pests, such as flatheaded apple tree borer, ash trees can tolerate.  These naturalized pests cause similar damage to EAB in ash trees.  The big difference is ash can coexist with the naturalized pests, while an infestation of EAB will kill any ash tree within 3 or 4 years.

The naturalized boring insect pests we commonly find in our declining ash trees are not working alone, environment plays a major role.   Mother Nature has not been kind to Colorado trees of all kinds, ash included, in the past few years.  Much of the damage expressed by ash and other trees throughout the Front Range was caused by damage suffered in November  2014, when we experienced a 77 degree drop in temperature over just a few days.    This was extremely damaging to ash and many other tree species in our area that had not ‘hardened off’ appropriately.

The fact remains that as of September 2015, EAB has only been detected within the city limits of Boulder.  And even in Boulder, many declining ash are being attacked by the naturalized pests, not EAB.

Myth #2 – Pesticides labeled for EAB won’t work once a tree is infested with this pest.

Not completely true. Multiple research studies on EAB in the Midwest have proven that several pesticides will control EAB even after an ash has become infested.  This is not to say that pesticides will save every ash or that pesticides should be used in all cases.  The decision to use a pesticide is a personal choice of the land owner/manager and should be based on the following:

·        Health or condition of the tree.  Ash trees with more than 30-40 percent canopy dieback, or damage or injury to the trunk of the tree, including severe frost cracking or splitting, will not respond well to treatment.  If you have ash trees with canopy dieback or severe trunk injury, consider removal and replacement with a species other than ash.

·        Location of the tree.  On a regional level, the current recommendation is to only consider applying pesticides for EAB management if the tree is located within the quarantine area or is close to the known area of infestation (City of Boulder).  On a site-specific level, if a tree is located under power lines, is too close to a structure, is in a parking lot or other area with limited root space, or just plain poorly sited, consider removal and replacement with a species other than ash, rather than use of prolonged chemical treatments.

·        Economics or value the tree provides.  Trees provide value and services to our landscape.  They increase property values, shade and aesthetics, and provide services to our communities by helping to mitigate storm water run-off and reduce cooling costs by shading our buildings and reducing temperature.  They also filter the air and help mitigate pollutants.
Myth #3 – All pesticides labeled to control EAB are harmful to pollinators.

Not true, as long as the law and label directions on the product are followed.  The pesticides used to control EAB are insecticides, and an insecticide can potentially kill a wide variety of insects, including those that are pollinators.  However, pesticides are highly regulated and researched so that misuse and harm to non-target organisms (pollinators and other animals and plants) is minimized.  All of us are bound by law to follow the label on an insecticide.  The label will tell us if there is risk of harm to pollinators when using a particular product, and how to use that product to minimize that risk.  For example, if a product is potentially harmful to honeybees, the label directions will tell us to avoid applying the product to flowering plants when bees are present.

Here is an example of the label instructions on a commonly used insecticide for backyard settings:

According to CSU Extension, there are four chemical control approaches considered for use in management of EAB:

1. Soil applications of systemic insecticides.  Two insecticides (imidacloprid and dinotefuran) can be applied to the root system of ash trees and will subsequently be taken up by the roots.
2. Non-invasive systemic trunk sprays. The insecticide dinotefuran can be applied as a coarse spray onto the trunk of ash trees and will be absorbed through the bark.
3. Trunk injections with systemic insecticides. Some insecticides can be injected into the lower trunk of trees and will then move systemically throughout the tree. These include emamectin benzoate, azadirachtin and imidacloprid.
4. Persistent surface-applied contact insecticides. A standard method of controlling many borers and bark beetles is to apply a persistent insecticide onto the trunk and branches to kill adults as they lay eggs and to kill newly hatched larvae before they enter the plant.  Various pyrethroid insecticides are usually used for this purpose (e.g., bifenthrin, cyfluthrin, permethrin).

Typically the insecticides in the class Neonicotinoid, which includes imidacloprid, dinotefuran and thiomethoxam, can be toxic to honeybees and other pollinatorsif used improperly and not according to label directions.  When used according to label directions, these pesticides should have minimal impact on pollinators.

Many insecticide treatments are best left to the professionals to apply.  Some of the treatments, such as trunk injections, can only be applied by commercial pesticide applicators, and formulations of insecticides that can be purchased ‘over the counter’ at garden centers are often not strong enough to protect trees with a trunk diameter at breast height (DBH) of 15” or more.   Commercial pesticide applicators are required to be licensed with the Colorado Department of Agriculture.  For more information and lists of applicators in your area, please contact the Colorado Department of Agriculture at 303-869-9063.

Don’t Move Firewood

All ash wood, logs, debris and firewood is under quarantine within Boulder County and the City of Erie.   If a tree infested with a pest dies, the tree is cut down and the logs often become ‘firewood’.  As firewood moves, so does the pest it contains.  This is the single most common method of movement of invasive tree pests over long distances.

Ash nursery stock and firewood are not allowed to leave Boulder County and Erie (the quarantine area) unless under a special permit.  Illegal movement of ash (live or dead) will result in penalties of up to $1000 per violation.

Together, we can slow the spread of EAB.

For more information on EAB identification, reporting, management and planning visit  or call 888-248-5535.

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