Emerald Ash Borer Treatment

Unsure if your tree is a city tree?
CLICK HERE for the City of Denver tree inventory site

  • Enter your address into the search box at the top left of the page
  • Blue triangles indicate a city tree that belongs to the Forestry Department
  • Green Circles indicate a parkway tree that belongs to the Parks and Recreation Department
  • Clicking on the triangles or circles will open a window that shows the species, address, ID # and size range of the tree
  • If the blue tree is an ash, it will include a line for “treatment cycle” (ash trees only)

Key of Terms:

  • N/A means the tree has not been selected for treatment by the city
  • Cycle1 means the tree was selected for treatment in 2016
  • Cycle2 means the tree was selected for treatment in 2017
  • Cycle3 means the tree was selected for treatment in 2018
  • Note: Ash trees that are a green circle will not show if they were selected for treatment

EAB in the news:

Protecting your ash trees from emerald ash borer

Emerald ash borer is considered the most destructive forest pest ever in North America. It is responsible for killing more than 50 million ash trees in 27 states. Across the front range of Colorado, 1 out of 6 trees are at risk.

Emerald ash borer was first detected in Boulder in September of 2013.

On Monday, June 6th, 2016, emerald ash borer (EAB) was detected in Longmont, CO, at a residential location which has not been officially released. The detection falls within an existing EAB quarantine area around Boulder County, in which the City of Longmont resides. The quarantine area was set up in an effort to prevent the human-assisted spread of this devastating insect.

Swingle believes emerald ash borer (EAB) is a serious threat across the Colorado front range, requiring action from residents and businesses. Here are some answers to commonly asked questions to help you stay informed:

How can I identify if I have an ash tree?

Plants form foliage buds in two ways – opposite and alternate. That is, the buds (leaves) are either directly across from each other (opposite) or found on different positions along the branch (alternate). The foliage buds in ash trees are found on opposite sides of the twig.

The leaves of ash trees are also distinct in that they are formed in 5 – 11 leaflets. The only other tree that has both alternate buds and leaves formed in leaflets is the boxelder. Boxelder always has either 3 or 5 leaflets.

Emerald Ash Borer Trunk Injection

If I treat my tree what should I expect?

If the tree is not treated it will die, that is a known fact. Some have asked, “If I treat my tree, will it look the same as it does now?” Maybe…and maybe not.

While the success rate for treatment is very high, when emerald ash borers become prolific, they will challenge the tree – or begin feeding on the tree before the treatment controls them. Treated ash trees will accumulate more dead branches and have a more sparse appearance to the tree canopy. When the EAB mortality curve subsides, the ash should return to its normal vigor.

Trunk injections are the best course of action. Injections can start in late May through June. It is effective for at least 2 years; yet research has shown it can last longer. Trunk injections are recommended for trees within 15 miles of the known detection site. A trunk injection may also be used if a soil injection is recommended, but the soil is not accessible.

Recommendations for homeowners and property managers:

  • Consult an expert to evaluate your trees and make recommendations
  • Do not plant new ash trees – good substitutes for ash include maples, lindens, honeylocusts, hackberrys, oaks and elms
  • Do not move firewood made from ash trees out of the area
  • Prune dead branches – dead branches weaken the tree and make it less likely to survive and attach
  • Additional recommendations may include tree fertilization and lilac/ash borer or ash bark beetle spray