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Environment

Emerald Ash Borer's 'Inevitability' Prompt Loveland Ash Removals

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www.emeraldashborer.info
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Adult Emerald Ash Borer

Work is underway to remove 800 ash trees from Loveland parks and open spaces. Why? Because of one little beetle.

The Emerald Ash Borer (EAB) has been in Colorado for years now, but remained undetected until 2013 when it was found in the city of Boulder, the furthest point west that it has been detected. The invasive beetle is native to Asia and has decimated the ash tree population across the U.S. No one has been able to stop or eradicate it.

Loveland forestry specialist Rob MacDonald thinks EAB's spread north from Boulder is inevitable.

"The beetle can be transported as a larvae underneath the bark of the infested tree," said MacDonald. "And it could be in Loveland for all we know, we want to be proactive and avoid a large expense at one time and keep our parks as safe as we can."

The total cost of removal and tree replacement will be over $500,000 which MacDonald said will take between 8 and 10 years. 

The decision to cut down the city's ash trees preemptively may seem extreme, but MacDonald said other options are problematic.

"Some of the chemical options are not always environmentally friendly," he said. "Most of the chemicals that are used are neonicotinoids and those are not safe to use for the most part around honey bees, so there are environmental implications with using some of those chemicals as well."

Dead trees are also a safety hazard since they are more likely to fall over. MacDonald wants the process to be gradual and not jarring to residents.

"I've been inspecting trees in our parks, looking for ash trees that are old have a lot of defects in them are structurally defective or are not terribly attractive… and their removal won't cause a huge loss in the landscape. Like most communities along the Front Range, we stopped planning ash trees a number of years ago," he said.

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Credit Rob MacDonald / City of Loveland
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City of Loveland
One of the 800 ash trees located in Loveland parks that will be replaced.

The replacement trees will be of differing species, like Ohio Buckeye and Horse Chestnuts so one type of tree doesn't dominate any one park.

Meanwhile Boulder is trying a biological control to keep EAB numbers down. In Sept, 2014 agriculture officials introduced almost 5,000 stingless, parasitic wasps from Asia.

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Credit Colorado Deptartment of Agriculture / APHIS
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APHIS
An adult Tetrastichus wasp. Thousands of them have been released in Boulder to try to keep EAB numbers down.

The tiny wasps (Tetrastichus Planipennisi) are a natural parasite of the EAB.

"Our hope is that they emerged and find EAB to parasitize - lay their eggs in - and then that's where they'd stay the winter, in the EAB larvae in the trees," said John Kaltenbach, state survey coordinator for the Colorado Department of Agriculture.

He said they will release more of the wasps in the spring, along with another biological control insect.

"It's an egg paracitoid, Oobius agrili and we'll release that at the time when emerald ash borer adults are laying their eggs," Kaltenbach said.

According to the USDA, Oobius agrili kill up to 60 percent of EAB eggs that are laid during the summer.

Tiny female Oobius accomplish this by searching the bark of ash trees for EAB eggs, which are laid in bark crevices and between layers of bark. When Oobius finds an EAB egg, it injects its own egg inside where it will hatch, grow, and kill the host egg. An Oobius adult will emerge and repeat the cycle for at least two generations during the EAB egg-laying season. Each Oobius adult can parasitize up to 62 EAB eggs during its lifetime. Oobius spends the winter as larvae inside EAB eggs and emerge the following spring as adults.

"[Emerald Ash Borer] doesn't spread very far on its own," Kaltenbach said. "Most of its big jumps are human assisted. It probably showed up in Boulder on firewood or something else that somebody brought in from the Midwest."

To that end, in addition to the biological controls, there is quarantine in Boulder County. The quarantine prohibits the movement of all untreated plants and plant parts of the genus Fraxinus out of the quarantined area. This includes, but is not limited to:

  • Logs and green lumber
  • Nursery stock, scion wood, and bud wood
  • Chips and mulch, either composted or uncomposted
  • Stumps, roots and branches
  • Firewood of any non-coniferous (hardwood) species

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