Emerald Ash Borer in Arvada

2023 Update: Emerald Ash Borer in Arvada

Emerald ash borer continues to spread throughout the City of Arvada, and the city’s forestry team continues to proactively respond to the infestation by treating ash trees on City-owned property through trunk injections and soil injections. 

However, a vast majority of ash trees in Arvada – approximately 97,000 ash trees – are located on private property. That means it is the responsibility of all property owners in the city to help fight EAB. 

How you can help fight against EAB to help protect Arvada’s tree canopy:

1. Identify if you have ash trees. Ash trees have the following characteristics: 
   • Compound leaves with 5 to 9 leaflets
   • Leaflets, buds and branches growing directly opposite from one another
   • Diamond-shaped bark ridges on mature trees
2. If you think you have ash trees on your property, contact a certified arborist as soon as possible. 
   • Tree professionals will help determine if your ash trees are infected with EAB. 
   • If your ash trees are infected, a tree care company can determine if your infected ash trees can be treated, or if they need to be removed. 
3. Don’t move firewood.
   • Protect all kinds of trees – not just ash trees – from tree-killing bugs by buying firewood from the same location you burn it. Transporting firewood long distances can potentially transport invasive species, such as EAB. Visit dontmovefirewood.org to learn more. 

Arvada's EAB Management Plan

The City prepared for the eventual infestation of EAB well ahead of its official arrival. The City's Forestry staff completed an inventory of the size, location, and health of all 1,500 ash trees on City property. The City also identified ways to proactively respond to the EAB infestation of ash trees on City property by developing the City of Arvada Emerald Ash Borer Management Plan (PDF). 

The City's Emerald Ash Borer Management Plan includes: 

• Management Strategies: Various methods have been employed to detect the presence of Emerald Ash Borer (EAB) in Arvada, including visual surveys, trap trees, chemical lures, and branch peeling. Early infestations are difficult to identify, and experience shows that there is typically a 3-4 year delay before removal becomes necessary.
• Proactive Mitigation: Removing ash trees that are in poor condition, have structural defects, or are not suitable for chemical treatments can help improve the resilience of the urban forest. Replacement with diverse tree species before EAB arrival is recommended to maintain the canopy. Proactively removing poor condition trees reduces food sources and habitat for EAB.
• Chemical Treatments: Properly applied insecticide treatments can protect ash trees from EAB. Treatments can be preventative or used in the early stages of infestation, but trees need to be in good condition for treatment to be effective. Different types of treatments, including soil application, trunk spray, trunk injection, are available, each with its own pros and cons. Licensed professionals should carry out insecticide applications.
• Private Property: The management of ash trees on private property is a significant concern. It is estimated that around 15% of Arvada's trees are ash trees, and EAB affects both public and private land. Treating healthy ash trees before infestation or removing infested trees early on is important. Preemptive removal of unsuitable ash trees and replacement can be a cost-effective strategy for homeowners.
• Overall Resilience: EAB will have a significant impact on Arvada's urban forest in the coming years. The city's forestry staff will focus on protecting high-value ash trees and removing those in poor condition. Replacement with a diverse mix of tree species will enhance the overall resilience of the urban forest to various challenges. It is crucial for citizens to participate in protecting and managing ash trees on private property to maintain a healthy urban forest.

Emerald ash borer background

As a non-native insect, EAB lacks predators to keep it in check. EAB only attacks ash trees in the genus Fraxinus but has also been documented infesting white fringe trees. Mountain ash and other tree species are not susceptible. 

It is unknown whether EAB arrived in Arvada by natural spread or via accidental human transport, such as in firewood or other raw ash material. Populations of the insect are capable of spreading a half-mile each year on their own. EAB was first confirmed in Colorado in 2013 in the City of Boulder. Since then, EAB spread to other nearby cities including Westminster, Longmont, Broomfield, and Arvada.