Isanti council hears U of M proposal to inject fungi into 100 city ash trees to fight emerald ash borer

Colin, a doctoral candidate at the University of Minnesota, told the Isanti City Committee of the Whole that his lab has spent three years testing entomopathogenic fungi such as Purpureocillium as a targeted treatment against emerald ash borer.

He said the proposed pilot would involve injecting a suspension of fungal spores into 100 city‑owned ash trees and monitoring treated and untreated trees through May 2031 to compare survival and non-target effects. "This would involve my injecting 100 city owned... and we would monitor those ash trees," he said.

The researcher described two delivery approaches under study, including tree injections similar to standard fungicide treatments, and said the fungi produce enzymes that allow them to penetrate and grow inside the insect, eventually killing it.

During questions, council members asked whether the fungi could harm non-target insects and whether injections could reach a critical mass to halt infestation. Colin said the approach is intended to be targeted and that non-target risk is a key focus of the study; he said those questions remain under investigation.

Staff and council discussed using the city’s GIS documentation to select trial trees by size and location and flagged the University’s ability to provide study documentation to help prioritize candidates. Council members expressed general support and agreed to direct staff to add a draft letter of support for the researcher’s grant application to the council agenda so members can review and, if desired, modify it before formal action.

The proposal is a research trial, not a citywide treatment program. Next steps are for staff to add the draft letter to the council agenda and for council to consider a formal letter of support at a future meeting.