Invasive Insects

Learn more about invasive insects — the Emerald Ash Borer, Spotted Lanternfly and Tussock Moth — and how you can protect your trees and vegetation.

Emerald Ash Borer

A close-up of an emerald ash borer. The Emerald Ash Borer (EAB) is a very serious and destructive pest of ash trees. State officials have confirmed the presence of EAB in the City of Arvada in 2020. First detected in Boulder, Colorado in 2013 and more recently found in neighboring municipalities, this invasive and highly destructive insect attacks and kills ash trees. The City of Lakewood continually monitors for EAB and has not found a presence in Lakewood.

View Confirmed Presence Map

The adult insects are present from May to October. The EAB larvae feed under the bark of ash trees, eventually girdling the tree and cutting off nutrients. These trees typically die within 2-4 years of first symptoms.

Helpful resources can be found on the Colorado State Forest Service EAB webpage and with tree identification information, area insect detection reports, and more. Visit this page for updates and resources.

What to do about this pest

Visit the Colorado State Forest Service EAB website for further details and directions.

How to Spot Tree Symptoms


Determine if you have any ash trees on your property.

True ash trees have compound leaves with 5-9 leaflets, and buds, leaflets and branches grow directly opposite from one another. Mature trees have diamond shaped bark ridges.

Use free resources to assist in identification.

The Colorado State Forest Service and Colorado State University Extension have developed EAB/Ash Tree ID App for both Apple and Android devices. Simply search the app store for “ash tree.”

Watch for symptoms.

Symptoms can include branch dieback near the top, D-shaped exit holes 1/8-inch wide, serpentine tunnels under the bark and new sprouts on the trunk and branches. Watch the video above to learn how to identify symptoms.

Evaluate whether chemically treating a tree is worthwhile.

Large, high-value healthy trees might warrant early treatment as “insurance” much more than young, unhealthy or poorly located trees. If you hire someone to apply pesticide treatments to protect ash trees, make sure the applicator is licensed by the Colorado Department of Agriculture as a commercial pesticide applicator.

Consider removing or replacing ash trees.

You may opt to remove or replace ash trees before the pest’s arrival and instead plant diverse new tree species. This can offer more long-term benefit than paying for preemptive chemical treatment in areas where the insect has not yet been detected.

Hire a Tree Contractor

Understand treatment options.

Treatments exist that are capable of helping infested trees recover if applied early in an infestation.

Avoid Transportation

Never transport firewood or other products from ash trees as this is the most likely method of accidentally spreading the pest.

Spotted Lanternfly

A Spotted Lanternfly adult. Photo credit: CSU Extension First detected in the U.S. in 2014, the Spotted Lanternfly is an invasive planthopper with a wide range of hosts. According to Colorado State University (CSU) Extension, this includes over 70 species of vegetation. Trees, grapevines, hops, hardwoods and ornamentals are all susceptible to damage from this insect.

Quick Facts (via CSU Extension)

  • Spotted Lanternfly has not been detected in Colorado at this time.
  • Scouting efforts for this insect are ongoing and continue to be important to minimizing the potential negative effects it could have on flora across the state.
  • Please contact your local CSU Extension office if you believe you have identified Spotted Lanternfly on your property.

Online Resources

Tussock Moth

According to Colorado State University (CSU) Extension, caterpillars of the Douglas-fir tussock moth (DFTM), Orgyia pseudotsugata, chew the needles of spruces, Douglas fir and true firs.  Most problems in urban forests along the Colorado Front Range have involved blue spruce.

Tree Sample.jpg Tussock Moth.jpg

During outbreaks the caterpillars can extensively defoliate plants, feeding first on the new growth then later moving to older needles.  Injury typically is first concentrated at the top of the tree but can involve the whole during severe outbreaks.  Tops of heavily damaged trees may be killed, sometimes after only a single season of severe injury.  Stresses from needle loss can also weaken plants so that they become more susceptible to effects of bark beetles, such as spruce ips, or fungi that produce cankers on branches.

Quick Facts (via CSU Extension)

  • Douglas-fir tussock moth caterpillars feed on needles of spruces, Douglas-fir and true firs.
  • Numerous natural enemies attack Douglas-fir tussock moth and these will often control outbreaks after a season or two.  A virus that produces “wilt disease” is a particularly important natural control.
  • The potential for problems can be predicted by surveying for egg masses before eggs hatch in late spring.

  • Several insecticides can be used to control Douglas-fir tussock moth during outbreaks.
  • Please contact your local CSU Extension office if you believe you have identified Spotted Lanternfly on your property.

Online Resources