Published: May 22, 2019
Two rows of ash trees on CU Boulder campus

This spring and summer, Facilities Management (FM) Outdoor Services and Housing Facilities Services (HFS) will continue to engage in responses to the emerald ash borer (EAB) and European elm scale infestations in our campus trees. Integrated pest management (IPM) strategies used against this pest include the injection of insecticides directly into the trunks of threatened or infested trees.

Campus treatments

Weather permitting, on or after May 28, and as part of the core campus treatments, staff will facilitate applications of the following insecticides:

  • TREE-age (Emamectin Benzoate) to 87 ash trees on Main and East campuses and at Wilderness Place. TREE-age has EPA Reg. No. 100-1309-74578.
  • Azasol (Azadirachtin) to seven elm trees on the west side of Main Campus on and around Varsity Lawn. Azasol has EPA Reg. No. 81899-4.

Weather permitting, on or after May 28, and as part of the product trial treatments, staff will facilitate applications of the following insecticides:

  • TREE-age (Emamectin Benzoate) to 14 ash trees on East Campus. TREE-age has EPA Reg. No. 100-1309-74578.
  • TreeAzin (Azadirachtin A and B) to 14 ash trees: eight trees at Colorado Avenue and Discovery Drive and six trees at the Space Science Building. TreeAzin has EPA Reg. No. 82996-1.

The elm scale applications will occur on seven trees. These trees have been infested with European elm scale for decades, leading to severe deficits in their vigor, health and appearance.

The EAB applications will occur on up to 115 ash trees, including 28 that are part of a product trial being conducted in collaboration with faculty and students from Colorado State University, the city of Boulder forestry division, ArborSystems and Arborjet. These trees are located on our Main and East campuses.

All of the EAB and elm scale applications will be performed by trunk injection, directly applying the insecticides into the cambium of the tree. This method delivers the product to the target insects, greatly minimizing exposure to non-targeted animal or plant species.

Professional applicators, licensed by the state of Colorado, will be conducting the trunk injections. As a further effort to ensure the highest standard of health and environmental protection, FM and HDS staff will accompany the contracted applicators to ensure only predetermined locations receive a treatment and all necessary precautions are taken to avoid non-target impacts.

Guidelines for pesticide use are generally described in the campus pest control policy. These applications are among the many tools used as part of an integrated approach to landscape management. The trees will continue to receive supplemental watering and cultural care, and will be monitored closely for treatment efficacy and overall health.

Staff will also be placing yellow application notice flags at the base of all trees, indicating where the application was made. Law requires these flags remain in place for 24 hours after an application has been made. In the interest of keeping the campus community informed, staff will leave these flags in place for one full week after the application occurs.

Please do not hesitate to contact Facilities Management should you have any questions or concerns. You may reach Outdoor Services Assistant Director Don Inglis at 303-735-6311 or Or you can reach Environmental Services Assistant Director Robert Lenahan at 303-735-3627 or