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Weed board resumes biological releases: root weevils showing ~80% local kill, gall wasps less certain
Summary
Staff reported releases of knapweed root weevils and gall wasps countywide; root weevils are producing strong local impacts (~80% kill), while gall wasp populations have suffered predation and have not yet shown clear mortality effects in some sites.
Duchesne County staff described progress on biological-control releases for knapweed and Russian knapweed, outlining a mixed early result: introduced root weevils are achieving notable success locally, while gall wasps have been vulnerable to predation and require further monitoring.
“The root weevils have it's about an 80 percent kill rate right now in Duchenne County,” the staff presenter said, adding that other counties sometimes record higher rates. Staff acknowledged that gall wasps have not yet produced a visibly measurable kill-rate in many local releases because grasshoppers and other insects consumed much of last year’s released populations.
Staff said they have several release and collection sites (Bridgeland, Fruitland, Roosevelt and other locations) and plan repeated releases to build sustainable populations. The board discussed that EDDMapS records can show where biological agents have been deployed and help prioritize future release and monitoring sites.
