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Emerald ash borer in Greeley, CO
Weld County is inside Colorado's EAB quarantine. Here is how to tell whether your ash is infested, and what to do about it.
Why this matters in Greeley
Ash was one of the most heavily planted street and yard trees across Greeley through the 1970s and 80s. It was tough, fast, tolerant of alkaline soil, and it did well in a climate that kills a lot of other species. Whole blocks went in as ash.
Emerald ash borer is a metallic wood-boring beetle from Asia, first found in North America in 2002 and now detected in well over thirty states. It has killed hundreds of millions of ash trees. It reached Colorado in 2013 and has been working its way along the Front Range since. Weld County is inside the state quarantine area.
The important thing to understand: EAB is not a disease your tree fights off. Untreated infested ash dies. Typically within two to four years of visible symptoms, and effectively all of them in an infested stand within about six.
How to tell if your ash has it
Work top to bottom.
Canopy dieback, starting at the top
The first thing most people notice. Bare branches in the upper third of the crown while the lower canopy still leafs out. The larvae feed just under the bark and sever the tissue that moves water and sugars, so the top — furthest from the roots — starves first.
Sprouts from the trunk and base
Vigorous shoots erupting from the lower trunk or root flare. This is the tree attempting to push growth below the damage. On an ash, it is a bad sign.
Woodpecker damage
Heavy flaking of bark and irregular holes on the upper trunk and limbs, sometimes called blonding because it exposes the pale wood underneath. Woodpeckers find the larvae before you do, and unusual woodpecker attention on an ash is one of the most reliable early indicators there is.
D-shaped exit holes
Adult beetles chew out through the bark leaving a distinctive hole about an eighth of an inch across, flat on one side. Round holes are a different insect. These are easy to miss because they are small and often high up.
S-shaped galleries under the bark
Peel back a section of loose bark and you will see winding, serpentine tunnels packed with fine sawdust. This is definitive. If you can see these, the tree is infested.
First, make sure it is an ash. Ash has opposite branching, compound leaves with five to nine leaflets, and diamond-patterned bark on mature trunks. Mountain ash is not a true ash and is not affected. If you are not sure, send us a photo of a leaf and the bark.
Treat or remove
This is the decision people find hardest, and the honest answer depends on the tree.
Treatment can work on a healthy, structurally sound ash that has lost less than about a third of its canopy. Systemic insecticide applied by a licensed applicator, repeated on a cycle, protects a tree indefinitely as long as treatment continues. It is a permanent commitment and a permanent cost.
Removal is the right call when canopy loss is past roughly a third, when the tree has structural defects independent of the borer, or when the tree is small enough that replacement makes more sense than decades of treatment. It is also the right call if you are not prepared to keep paying for treatment for the life of the tree, because a lapsed treatment programme ends the same way as no treatment.
We will tell you which category your tree is in. If it is worth treating we will say so, even though removal is the larger job.
Dead ash is a different kind of hazard
This is what makes EAB more than a landscaping problem. Ash killed by borer becomes exceptionally brittle, far more so than most dead hardwood, and it fails without the usual warning signs. Limbs drop in still air. Climbing a dead ash is dangerous enough that it changes how the removal has to be done, and it gets worse every season the tree stands.
The practical consequence is that removing an infested ash early is cheaper and safer than removing the same tree three years later.
Disposal under quarantine
Colorado restricts movement of ash material out of quarantined areas to slow the spread. That affects where wood and chips from your tree can legally go. We handle disposal in line with current requirements — and it is worth knowing that moving ash firewood yourself is exactly how the beetle covers long distances.
Questions we get about this
How do I know if my tree is an ash?
Ash has opposite branching, meaning branches and buds come off the stem directly across from each other, and compound leaves made up of five to nine leaflets. Mature bark shows a tight diamond pattern. Mountain ash is a different genus and is not affected by EAB.
Is treatment worth it?
It depends on the tree. A healthy, well-placed ash that has lost less than about a third of its canopy is a reasonable candidate, provided you accept that treatment continues for the life of the tree. Past that point the tree rarely recovers a full canopy and the money is better spent on removal and replacement.
How fast does an infested ash die?
Usually within two to four years of visible symptoms. In an infested area, effectively all untreated ash dies within about six years.
Why is dead ash more dangerous than other dead trees?
It becomes unusually brittle. Limbs fail with no wind and no warning, and the whole tree becomes hazardous to climb, which makes removal more complex and more expensive the longer you wait.
Can I keep the wood for firewood?
Not to move it. Colorado restricts movement of ash material out of quarantined areas, and transporting ash firewood is the main way EAB spreads long distances. Wood can stay on your property but should not travel.
Do you charge for an ash inspection?
No. We will look at the tree, tell you whether it has EAB, and tell you honestly whether it is a treatment candidate or a removal.