Emerald Ash Borer Detected in Larimer County

Emerald Ash Borer (EAB) has been detected outside of Berthoud in unincorporated Larimer County. More information at https://www.colorado.gov/agplants/emerald-ash-borer or contact the Larimer County Forester at 970-498-5765.

The Larimer County Forester can assist you in identifying and managing forest pests on your property. Explore this webpage to learn more about common forest pests in or near Larimer County.

Mountain pine beetleMountain pine beetle (Dendroctonus ponderosae) is a native insect of western North America. It is the most important insect of pines in this area, causing much pine tree mortality locally and across western North America. Dendroctonus literally means "tree killer." Currently, mountain pine beetle is not at an epidemic level in Larimer County. The Larimer County Forester is available to work with homeowner groups or individual landowners to help with education, identification of beetle-infested trees and treatment plans.

For more information:

thousand cankers diseaseThousand cankers disease (TCD) affects black walnut trees and is a result of attacks from the walnut twig beetle and associated fungus. TCD will kill most black walnut trees in Larimer County. Sanitation is the key to limiting the spread of TCD. As the steward of your property, removal of affected trees and the destruction of the complete tree, or approved treatment of the usable wood within the affected area, are required.

TCD is a fungal disease that is carried from tree to tree by the walnut twig beetle. The walnut twig beetle is a native insect of the southwest United States and has very little affects on the native walnut tree of that area, the Arizona walnut. The affects of TCD on black walnut trees in Colorado are almost always fatal.

If you have questions or believe that your walnut tree might have TCD, please contact the Larimer County Forester or your city forester for guidance in removal and proper disposal. Get more information on TCD.

emerald ash borerEmerald ash borer (EAB) was detected in Larimer County, outside of Berthoud, in September of 2019

Tips for EAB mitigation can be found at the Colorado Department of Agricultural webpage.

Ash trees make up 15-50% of the urban trees in Colorado, depending on location. If EAB does get established in an area, it is 99% fatal for ash trees without treatment. Pesticide treatment may be necessary for the remaining life of the tree. The loss of 25% or more of a community's crown cover will cause a major financial burden on both private and public resources. 

EAB is a federally regulated, exotic invasive insect native to Asia. The beetle was first discovered in 2002 in southeast Michigan and Windsor, Ontario. 

japanese pine beetle Japanese beetle (Popillia japonica) adults feed on the leaves and flowers of many trees, shrubs and field crops in Colorado. Insecticide treatment is difficult due to the risk to beneficial insects, primarily pollinators. Get more information on the Japanese beetle.




Prevent the Spread of Forest Pests

Buy firewood where you burn it. Moving firewood can spread tree-killing insects and diseases. Buy firewood at or near campgrounds, ideally within 50 miles or less of where you’ll camp. Learn more at www.dontmovefirewood.org.

  • It is illegal to bring firewood of any non-coniferous (hardwood) species from the quarantined area in Boulder County into Larimer County to prevent the spread of emerald ash borer.
  • Gathering firewood in Larimer County campgrounds is prohibited.

Larimer County Forester

OFFICE: 2649 E. Mulberry St., Suite 6, Fort Collins, CO 80524
PHONE: (970) 498-5765
EMAIL: dlentz@larimer.org
OFFICE HOURS: 6:30 a.m. - 3 p.m., Monday - Friday (except holidays)