Don't Give EAB a Ride!

Posted by: Denyse Schrenker, Eagle County Extension

People were seeing fireworks last week when it was confirmed that emerald ash borer has made its way to the Western Slope. Two new pockets of emerald ash borer (EAB) in Littleton and Carbondale were recently discovered. These new locations are well outside of the known infested area north of Denver: see Colorado State Forest Service map for known EAB locations. In case you missed it, Emerald Ash Borer is an invasive insect that feeds under the bark of trees during its larval stage. This feeding stops the flow of nutrients and water and gradually kills the tree over a 3 to 5 year timespan. All true ash species (Fraxinus spp.) are hosts for EAB. Green ash (Fraxinus pennsylvanicus) and white ash (Fraxinus americana) are commonly grown in Colorado and both are highly susceptible to emerald ash borer, including their cultivars such as the popular white ash variety, ‘Autumn Purple Ash’. Mountain-ash (Sorbus spp.) are not susceptible to emerald ash borer as they are not a true ash.

Damage from emerald ash borer. Photo credit: Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

How is this different from mountain pine beetles?
Although mountain pine beetle has killed a large number of trees as well, it is a native insect that has periodic outbreaks. The outbreaks are a naturally occurring cycle (though they can be prolonged by human activity) that will eventually end and the surviving trees will regenerate the forest over time. Since emerald ash borer is not native to North America it has no native predators to halt outbreaks so it will continue as long as there are ash trees present.


What Can I Do?

White ash tree. Photo credit: Richard Webb, Bugwood.org

Don’t Move Firewood (remind your friends & family too!)
With camping season in full swing, don’t be tempted to save a couple bucks by taking firewood with you. Always burn firewood locally and buy seasoned and kiln-dried wood as many harmful insects, not just EAB, can hitch a ride in firewood. You can learn more about this at https://www.dontmovefirewood.org/.

Use firewood locally, emerald ash borer and other harmful insects can hitch rides in firewood.

Use Best Tree Care Practices

• Watering Mature Trees
• Watering Your Landscape During a Drought
• Fall and Winter Watering 
• Mulching Trees 
• Healthy Roots, Healthy Trees

Learn to Identify Ash Trees

• Ash Tree Identification
• Contact your local extension office for assistance with identification

White ash leaf. Photo credit: Paul Wray, Iowa State University, Bugwood.org

Learn More about Emerald Ash Borer

• Emerald Ash Borer Resources
• Colorado State Forest Service: Emerald Ash Borer
• FactSheet: Recognizing Wood Boring Insects of Ash Trees in Colorado

Emerald ash borer in exit hole. Photo credit: Debbie Miller, USDA Forest Service, Bugwood.org

Make a Plan

If you are in close proximity to an outbreak, start making a plan for your ash trees. Contact your local extension office for more information.

Lilac Ash Borer

Lilac Ash Borer- Cassey Anderson CSU Extension Adams County

Most of us are aware of the looming menace posed by Emerald Ash Borer to our ash trees along the Front Range in Colorado. However, we do have another pest of our ash trees, the lilac ash borer. Lilac ash borer can, like their name, impact both lilacs and ash trees. They are more of a concern in ash trees.  Fortunately they are usually not lethal to the tree.  Adult borers emerge from trees in the spring then lay egg on the bark .  The larva which develop then burrow into the tree where they spend most of their time in heartwood.  They then overwinter in the tree and emerge as adults the next year.

Pupal Skin Left Behind by Lilac Ash Borer (from CSU Extension Lilac Ash Borer fact sheet)

Distinctive round/melon shaped holes can often be found on the main trunk of the tree. During the spring and early summer it may even be possible to find the final pupal skins of the lilac ash borer left in the trunk as the mature insect emerges. The pupal skin may resemble a wasp. They are not related to wasps but rather are a type of clearwing moth which has some resemblance. 

Lilac Ash Borer Exit Holes

We had a severe wind event here in Adams County this spring and saw one of the unfortunate side effects of a tree that had been riddled with the insect.  While the damage caused by the larvae rarely kills trees because it does not feed extensively in sapwood it does weaken and makes them more prone to failure.   

This tree snapped a foot or so off the ground exposing the larval galleries both new and old from the feeding of the lilac ash borer. These trees had been planted in a very narrow strip between road and sidewalk, were not getting sufficient irrigation if you looked at past growth and the grass growing around the trees, several of the trees also had visible girdling roots which likely compounded their stress.

Lilac Ash Borer Galleries 

Generally speaking stressed trees are more susceptible to damage from lilac ash borer. Ensuring that existing trees are planted correctly, do not have girdling roots, and are watered appropriately can reduce infestations of lilac ash borer.  Treatment for this insect is not the same as treatment as for emerald ash borer. For treatment options and more information please see our fact sheet on lilac ash borer: https://extension.colostate.edu/docs/pubs/insect/05614.pdf

Help Slow the Spread of Emerald Ash Borer

By Carol O'Meara, Boulder County Extension

In the two seasons since detection of the Emerald Ash Borer in Boulder, experts have learned that it’s very difficult to find.  The Colorado EAB Response Team, arborists, and foresters have been looking high and low throughout the Front Range, into tree canopies and on the ground at firewood, trying to find the destructive pest.  For a time, the only place that bug was detected was in the city of Boulder.

But that changed last Monday, June 6, when Bodhi Tree Care Arborist James Young saw the classic symptoms of the Green Menace:  D-shaped exit holes and serpentine galleries just under the bark on an ailing ash tree in Longmont.  He also found one of the bugs half in, half out of the ash, killed as it was emerging from the branch. 

Young notified Ken Wicklund, City of Longmont Forester, who went to inspect the tree.   In the warmth of the day, Emerald Ash Borer adults – half-inch long, metallic green beetles – were flying around the tree.  Wicklund contacted the Colorado Department of Agriculture for confirmation identification, which, sadly, was positive.

At the same time the insect was found in a new Colorado community, our neighbors in Nebraska announced the first detection of the pest, making their state the 26th to have the tree killer.  The speed of the spread – to 26 states since it’s detection in Michigan in 2002, killing hundreds of millions of ash – causes any tree lover to weep in dismay.

As you ponder the decimation of a native North American tree, consider also that complicit in this is humans.  The insect arrived here because humans brought it over from its native Asia.  It was by accident but, like opening Pandora’s Box, the damage was done. 

The insect doesn’t naturally spread more than about 1-and-a-half miles per season; for it to leap across the Great Plains or even across our county took humans, moving it in firewood, nursery stock, or shipping pallets.  Once infested wood arrived, the insects ventured out into surrounding areas, attacking ash trees.  By the time the bug is detected it can be miles away from the original source of the infestation.

This is why Boulder County is quarantined; the EAB Response team is trying to slow the spread.  No firewood or any ash wood can be taken out of the quarantine.  It will take all of us to do this.

Owners of ash trees near or within the detection sites of Boulder and Longmont should make a plan for what they want to do for their ash.  Protection with pesticides, removal, or replacements with saplings of a different type of tree is a personal decision each tree owner should weigh, because the Emerald Ash Borer kills trees in a scant handful of years.  The Boulder County EAB webpage offers information on all aspects of what you need to consider (bouldercounty.org/property/forest/pages/eab.aspx).

To aid in your decision, the Colorado State Forest Service has a Decision Guide that walks you through the process (bouldercounty.org/doc/parks/eab-decision-guide.pdf).   Be sure to assess the health of the ash when considering protecting it; not all trees are healthy enough to save. 

For the most accurate tree health assessment, hire a pro.  Certified Arborists are trained to look for symptoms of EAB and many other pests, be they insects, disease, or environmental problems.  They can climb the tree to take a close look at it.  Find a Certified Arborist through the International Society of Arboriculture (ISA) or look for an accredited company by the Tree Care Industry Association (TCIA).

And don’t move firewood or ash wood around.  This will help slow the spread of the Emerald Ash Borer.

Ash leaves Curling?

Posted by Eric Hammond Adams County

The wet weather which much of the state has experienced this year has been great for water bills, lawns and many plants in the garden.  However, it has also created some challenges.   One pest which has thrived under the moist and humid conditions is the ash leaf curl aphid (Prociphilus fraxinifolli).

Curling leaves on a mature ash

 

These insects are a type of wooly aphid which begins feeding on the underside of terminal leaves of green ash (Fraxinus pennsylvanica) in the spring.  Their feeding causes the leaves to curl (thus the aphid’s name).   Late in the summer winged individuals are produced which migrate to the roots of ash trees.

Leaves curled by ash leaf curl aphid

 

The damage caused by this pest is showy and often alarming to tree owners.   However, it is mostly a cosmetic issue and is normally not a serious concern to the tree’s health.   Normally treatment with insecticides is not warranted and sprays are ineffective once the leaves have curled, providing protection for the aphids within.   There are systemic treatments available but they can take several weeks or more to be affective and, again, are not normally necessary for the health of the tree.   If the curled appearance of the terminal leaves is distressing they can be removed from the tree.

 

Another nuisance associated with the insect is the sticky excrement they produce which is known as “honeydew”.   This sugary substance drips from affected trees in such quantity that it can coat cars, patio furniture, sidewalks or any other element of the landscape which is unlucky enough to be below the trees.   The honeydew is not only sticky and unpleasant but it is also commonly colonized by gray sooty mold which give it a black appearance with often appears to stain whatever it has dripped on.

Ash leaf curl aphids produce a white waxy substance as well as a sticky excrement
know as "Honeydew"

 

However, while all of this is a pain (pain in the Ash?), the issues associated with ash leaf curl aphid are still mainly aesthetic nuisances and it is not a serious threat to the tree’s health.  In most cases tolerance is the best option for dealing with the pest.   More information can be found in the “Aphid on Shade Trees and Ornimentals” Factsheet located here.

Assessing Ash risk

Posted by: Carol O'Meara, Boulder County Extension

In the months following the detection of Emerald Ash Borer in Boulder, people have been holding their breath, waiting for word on where the pest would show its presence next. They’re gazing at their ashes, appreciating what they have that might, in a short time, be gone.

Advertisements by mail or on the radio make the situation seem dire (one announcer sounds as though he’s shaking with rage that the insect dared come to Colorado). If you’re wracked with indecision on what to do to protect your ash or when to do it, take a deep breath and relax before making your decision.

Distance from the detected pest is the first question to answer; in Colorado CSU Entomologists recommend that only those ashes within five miles of the bug need protection. If you live further away than five miles from the pest, you have time to plan before booking tree treatments.

Check how close you are to the five mile zone by clicking on the Ash Tree Management Zone Map. There, you can type in your address and the map will zoom in to your location and identify the risk zone you live within.

Then build a plan, starting with an assessment of your trees and whether they’re healthy. Not all ashes are healthy enough for treatment; should they have greater than 40-percent dieback of their canopy they won’t translocate treatments effectively through the tree. Small trees could be protected, but ask yourself if it would be better to remove and replace them with another tree type. Often, costs of treatment far outweigh the costs of replacement.

Next, assess the type of treatment you would like for the tree. Small trees of less than 15-inch diameter can be helped with products you can purchase and apply yourself. But be careful – these products contain pesticides harmful to bees, so make sure there are no blooming plants, wanted or unwanted, in the ground under the tree (especially dandelions).

If your tree is larger than 15-inches or you’d like options that are more bee-friendly, ask your tree care company to help you in your decision. Don’t be alarmed by radio ads – heavy with reverb – announcing the presence of the pest. Arm yourself with the facts by going to eabcolorado.com and scroll down to How to Manage EAB and click on control options for information on the available treatments.

"Promise America" to Not Move Firewood!

Alexis Alvey, Horticulture Agent, CSU Denver Extension

What do baseball bats, bugs, and ash trees all have in common? (And no, this is not some lame, bar room joke.)  Well, they are all part of the "Promise America" campaign initiated by the US Department of Agriculture.  This campaign has been launched to educate everyday homeowners and gardening enthusiasts alike about the invasive insect pest called the Emerald Ash Borer (Agrilus planipennis) which is killing literally millions of ash trees across America.  There are a handful of different species of ash trees that are native to the Midwest and the East Coast that are commonly planted as great urban street trees throughout the US, including Denver.  Wood from ash trees has traditionally been used to make baseball bats.  Unfortunately, all of our native ash, including White Ash (Fraxinus americana) and Green Ash (Fraxinus pennsylvanica), which are the two species planted in horticulture, are completely at the mercy of Emerald Ash Borer.    This tree-killing beetle was first identified in the US in 2002 near Detroit, Michigan and is native to eastern Russia, northern China, Japan, and Korea.  No one knows for sure how or when it got here, but most likely in the 1990s it came to the US in ash wood used for stabilizing cargo in ships or for packing or crating heavy consumer products.  It has now spread into seventeen additional states and two Canadian provinces and continues expanding its range.  Its spread has been accelerated by the movement of infested firewood.  Last year it was discovered in Kansas for the first time, and people are worried that it will soon be in Colorado.  Denver Parks & Recreation’s Forestry Division will begin monitoring for Emerald Ash Borer for the first time this season. 

Photo: Adult Emerald Ash Borer 

(Leah Bauer, USDA Forest Service Northern Research Station, Bugwood.org)

The Emerald Ash Borer is actually a relatively pretty insect (I say relative, because in my opinion all insects are kind-of gross.)  The adult beetles are a bright, metallic green, a half-inch long, and have a flattened back. But the problem is not the adult beetles, it is their larvae.  The larvae are a type of flatheaded borer.  (By the way, “You are such a flathead!!” makes for a great insult!)  Larvae hatch from eggs laid within bark crevices and under bark scales in the spring.  They chew through the outer bark of the tree and into the cambium where they feed in the phloem interrupting the flow of nutrients within the tree, ultimately girdling it. 

Signs and symptoms of Emerald Ash Borer infestation are yellowing leaves on branches and then dieback generally in the top of the tree canopy first.  Sprouting from the base of the trunk can also occur.  If you are lucky and look very very carefully, you may see small holes in the trunk that are 1/8” in diameter and that are D-shaped.  Complete defoliation and tree death typically occurs within 2-3 years.   

Photo: Green Ash dead due to Emerald Ash Borer 

(David Cappaert, Michigan State University, Bugwood.org)

Unfortunately there is no simple cure for Emerald Ash Borer.  This little beetle has had an enormous economic and ecological impact.  The devastation of the insect is remarkable - over 53 million ash trees have died or are dying from the borer and all of North America's 7 billion ash trees are at risk.  It is estimated that up to $26 billion has been lost due to the borer in just four Midwestern states.  This took into account the cost of lost tree value, tree removal, and tree replacement. 

Invasive pests have been incredibly problematic for our urban trees and native forests for the past century.  From Dutch Elm Disease to Chestnut Blight to Asian Longhorn Beetle, invasive insects and disease have changed the composition and ecological functioning of our forests as well as their look and feel.  So please, “Promise America” that you will not move firewood; that you will burn firewood where you buy it; and that you will plant a diverse selection of trees and not all the same species. Oh, and that old wooden baseball bat of yours may be more valuable than you think!  

Photo: http://stopthebeetle.info/

For more information, visit:

www.emeraldashborer.info

stopthebeetle.info

www.dontmovefirewood.org