Greeley foresters bracing for the arrival of emerald ash borer
Emerald ash borer
Adult emerald ash borers, a nonnative beetle from Asia, are emerald green and grow to about 1/2-inch long.
Benefits of trees
The city of Boulder has compiled an online inventory of its trees, complete with statistics outlining their financial and ecological benefits. Below are some of those stats, according to Boulder.MyTreeKeeper.com.
Total number of trees in the city of Boulder: 50,661
Total yearly eco benefits: $11,570,505.19
Greenhouse gas benefits:
— 11,702,886.15 lbs CO2 avoided
— 9,760,205.10 lbs CO2 sequestered
— 95,478,589.60 gallons saved
— 6,496,279.41 kWh saved
— 629,155.70 Therms saved
Air quality benefits:
— 43,535.10 lbs pollutants saved
— 12,346,420.50 leaf surface area (square feet)
Slowing the spread of emerald ash borer
Do not move firewood. If going camping, burn and dispose of wood where it is purchased.
Determine if that is an ash tree in the yard.
If planting new trees, consider planting species not impacted by emerald ash borer.
Common signs of an emerald ash borer infestation
Thinning canopies, usually at the tree’s upper branches.
Tiny D-shaped holes about 1/8-inch in diameter made by mature emerald ash borers as they emerge from beneath the bark.
Cracks in an ash tree’s bark, usually where larvae have been feeding.
S-shaped feeding galleries, which can be observed by removing the ash tree’s bark.
Woodpecker damage or increased activity, as the bird has developed a taste for emerald ash borer larvae.
Great trees to plant in Greeley
Oaks, including bur, English, chinkapin, crimson spire or Fastigiate English
Kentucky coffeetree and Kentucky coffeetree espresso
Honey locusts, including shademaster, skyline and imperial
Lindens, including redmond and sentry
Elms, including accolade and discovery
Crabapples, including red barron, perfect purple, spring snow, centurion, thunderchild, radiant, indian summer and coralburst
Hawthorns, including thornless cockspur, Russian and Washington
Pears, including autumn blaze and Cleveland select
Oaks, including gambel or wavy leaf
Magnolias, including star and saucer
Hotwings tatarian maple
Japanese tree lilac
For more information about emerald ash borer, go to www.GreeleyGov.com/AshBorer.
There’s a new pest on the horizon that has a taste for ash trees, which just happens to be the species that dominates Greeley’s urban forest. When the emerald ash borer does arrive, it will produce major holes in the canopy of some of Greeley’s most prized public places, including Lincoln Park and Island Grove.
“Enjoying a saunter through the Arts Picnic?” Hatcher said. “The largest shade trees in Lincoln Park are ash. Catching an afternoon event at Island Grove? We have over 100 ash trees there.”
Hatcher estimates 15 percent of Greeley’s tree population is comprised of ash. A whopping 30 percent of those are located between the sidewalk and the curb where residents walk and drive past every day.
City foresters are used to such a calamity. When they’re not worrying about losing trees to age or structural problems, they’re forced to deal with a never-ending barrage of natural predators, including pests, disease and an array of environmental factors, such as floods, fires and extreme weather.
Since the 1900s, it seems about every generation or so something of biblical proportions comes along and wipes out an entire plant species in the United States, Hatcher said.
This latest pest has been in the U.S. since 2002, but it’s still relatively new to the country’s mountain states. The emerald ash borer was discovered in 2013 in Boulder, which has Hatcher worried about the day it comes to Greeley.
The non-native beetle from Asia has already claimed at least 50 million ash trees in 25 Midwest and east coast states, causing hundreds of millions of dollars in damages. Boulder’s forestry officials have successfully contained the ash borer for almost three years, and yet it’s probably only a matter of time before it spreads to other cities. All other attempts to eradicate the pest have fallen short.
Foresters cringe anytime a tree is lost, but losing an ash is particularly tough to swallow, said Hatcher. Ash, particularly green ash, became a popular tree in urban forestry because it’s highly adaptable and has a high tolerance for poor growing conditions, making it the perfect “street tree.”
Ash trees also live a long time — 120 years on average for green ash and 260 years for white ash — and can grow to 80 feet tall with a 45-50-foot spread, making them ideal shade trees in public parks. They’re unrivaled in terms of adaptability, size and growth rate. Replacing them will take decades.
“The emerald ash borer has essentially removed the ash tree as an option for our urban forest,” Hatcher said. “This isn’t Chicago or coastal Georgia where high precipitation and rich soils sustain a wide variety of tree species.
“We don’t have that luxury because there are only so many trees that can thrive in our high plains desert. When it gets here, emerald ash borer is going to leave a lot of holes in our urban canopy.”
History of EAB
The emerald ash borer was first discovered in September 2002 outside Detroit. An invasive species from Asia, forestry officials believe the beetle traveled to the U.S. in wood packing material.
Adult beetles are emerald green and grow to about 1/2-inch long, but it isn’t the adults killing ash trees by the millions. Ash borer larvae feed on the wood beneath an ash tree’s bark, disrupting its ability to transport water and nutrients to its upper branches. Once infested, it can take as long as five years before an ash tree exhibits symptoms and several more before it ultimately dies.
After it was first discovered in the fall of 2002, emerald ash borers quickly spread to Ohio, Maryland and Fairfax County, Va.
Five years later, in July 2008, 10 states from Maryland to Missouri had confirmed ash trees infested with emerald ash borer. But a curious thing happened in 2013. The beetle was discovered in Boulder — more than 600 miles away from the outbreak’s western most border in Kansas City, Kan. Colorado became the 22nd state to confirm ash trees in one of its cities infested with ash borer.
Today, emerald ash borer is a resident in 25 states. Despite federal quarantines being in place in 22 out of those 25 states, forestry officials believe emerald ash borer arrived in Boulder when someone violated a local quarantine and transported infested ash — likely firewood — across state lines into Colorado, Hatcher said.
What Boulder is doing about EAB?
Every year, the city of Boulder Parks & Recreation Department conducts a survey of its tree inventory, which is what foresters were doing in September 2013 when they first discovered emerald ash borer, city of Boulder Forestry Assistant Tom Read said. Almost immediately, the Colorado Department of Agriculture imposed a quarantine on emerald ash borer in Boulder County.
Similar in scope to actions taken in other states and by the U.S. Department of Agriculture, the quarantine prohibits any potentially infested ash trees, logs and firewood from leaving the county.
Boulder forestry officials are in the midst of a long-term plan to try to save the city’s most valuable ash trees — those near public buildings and in public parks — while removing and replacing the rest with other species.
Boulder Parks & Recreation manages more than 50,000 trees, and more than 6,000 — or 12 percent — are ash. In 2014, the Boulder City Council approved a conservative plan to treat about 20-25 percent of its ash trees with a pesticide.
As for the other 4,200-4,500 ash trees managed by the city, they’re actively being cut down and replaced. That process will take several years to complete.
At the county level, the situation isn’t as dire, said Brett Stadsvold, emerald ash borer coordinator for Boulder County. Originally from the Midwest where he earned a degree in natural resources from the University of Minnesota, Stadsvold first began addressing the emerald ash borer epidemic when it showed up in 2009 in St. Paul. He’s been with Boulder County for about the past year and a half.
When he arrived, Boulder County managed 1,500 ash trees. As was the case in the city of Boulder, county officials also developed a plan to save its most important ash trees, while eradicating the rest.
If the city of Boulder’s ash treatment plan sounded conservative, Boulder County officials took the idea to the extreme. Of the 1,500 ash trees in Boulder County, only 24 — less than 2 percent — were identified as viable candidates for pesticide treatment. The rest are being removed at a rate of about 190 ash trees per year. The county is on pace to phase out all of its ash trees in eight to 10 years, Stadsvold said.
Bracing for the future
Forestry officials in Boulder deserve a lot of credit considering they’ve been able to keep emerald ash borer in check for almost three years, Hatcher said. Despite those efforts, local forestry officials began compiling an emerald ash borer management plan for the day it arrives in Greeley, as well as a public information campaign, which forestry officials recently unveiled online at http://www.GreeleyGov.com/ashborer.
Although Greeley foresters began putting the plan to paper in 2014, the reality is Colorado officials have been preparing for emerald ash borer since it was discovered in 2002.
Even though it was more than 1,000 miles away at the time, the city of Boulder stopped planting ash in 2002. Greeley followed suit in 2005.
“We’re not in panic mode just yet, so people don’t need to go out and cut down their ash tree or start treating it with pesticides,” Hatcher said. “The city has developed a plan to deal with emerald ash borer, and all we’re asking is for members of the public to do the same.”
It’s important for residents to have a plan because far more ash trees exist on private property than public. Although Boulder officials have their hands full managing their combined 7,500 ash trees, the Colorado Department of Agriculture says the number of publicly managed trees only encompasses a fraction of the total. The state agriculture department estimates there are more than 98,000 ash trees in the city of Boulder alone. It estimates the Denver metro area’s urban forest encompasses 1.45 million ash trees.
Although not on that same scale, the same holds true in Greeley. Of the estimated 10,000 ash trees in the city, the Greeley Forestry Department manages only 950. The rest are located in the front and backyards of residential homes.
Diversity is the key
Although agencies at the local, state and federal levels are exploring a variety of options to curb the emerald ash borer before it decimates the ash tree population in North America, all signs point to a future when ash trees will no longer line our streets or provide shade in our parks.
But this also isn’t the first time a species of tree has been plagued by an epidemic, Boulder Forestry Assistant Tom Read said. Before the early 1900s, American chestnut was the most common tree in the U.S. and grew in abundance from coast to coast. In 1904, a parasitic fungus, commonly known as chestnut blight, was accidentally introduced from Japan.
Within 40 years, the nearly 4 billion-strong population of chestnuts was almost wiped out. A few clumps in California, Wisconsin, Michigan and the Pacific Northwest survived.
In order to restore the devastating loss to the nation’s rural and urban canopies, foresters turned to another hearty tree, the elm, to replace the native chestnut. But in 1928, Dutch elm disease was introduced from Asia and Europe. Although quarantines successfully contained the disease to within a 150-mile radius outside of metropolitan New York City, those operations were suspended in 1941 when the U.S. entered World War II.
By 1989, 75 percent of the 77 million elm trees in the U.S. were lost. Foresters again tried to restore that loss, this time turning to ash trees.
Because of the continued international commerce the U.S. enjoys with other countries, the new buzzword in forestry is diversity.
“If we remove three ash trees, we’re replacing them with three different species — a lack of diversity is what allowed this to happen,” Read said. “We haven’t planted an ash tree since it was discovered in 2002 because we knew it would be here eventually, and that was considered a very progressive decision at the time. If you’re not thinking at least 20 years into the future, you have no business working in forestry.”
The Greeley Forestry Department manages four nurseries and has been working for about the past decade to increase the level of diversity of Greeley’s urban forest. The department also recently saved a thornless cockspur hawthorn from the new hotel and convention center construction site on 9th Avenue at the Lincoln Park Annex and moved it to Island Grove recognizing in the era of emerald ash borer, every tree is important.
With it being spring planting season, Hatcher said the best thing residents can do to help offset future impacts to Greeley’s urban forest is plant a tree, so long as it isn’t an ash.
“Every tree counts,” Hatcher said. “The longer emerald ash borer isn’t here, the infinitely better off we’ll be. But it’s coming, so replanting now is crucial.”❖