Wild carrot, or Queen Anne’s lace, is a widespread and difficult to control nuisance weed across most of western Oregon. It is prolific in roadsides, poorly managed pastures, post-harvest forestry sites, and other areas with intermediate disturbance levels, although it is adaptable enough to become weedy in many other sites as well. East of the Cascades, distribution is more sporadic, although there are certainly areas with dense populations. Wild carrot poses a potential contamination risk to carrot seed production, and is a high priority weed in wildlands and other extensively managed land uses surrounding current carrot seed production areas.
Despite its wide distribution, I was able to find surprisingly little public information regarding the efficacy of many herbicides currently important in non-crop settings for control of wild carrot. As part of a larger project focusing on proactively managing wild carrot risk around Oregon carrot seed production areas (funded by the Oregon Department of Agriculture Specialty Crop Block Grant Program), trials were initiated in the spring of 2022 at 2 non-crop sites in the Willamette Valley with the intent of providing weed managers with a straightforward comparison of the efficacy of common non-crop herbicide options for control of wild carrot.
Final data from these trials are not yet available and they will be repeated in 2024, but preliminary results show marked differences in efficacy between products. In both trials, herbicides (Figure 1) were applied to wild carrot plants in the rosette stage shortly after resumption of active spring growth in mid-March. Control was rated on a 0 to 100% scale at intervals throughout the season, with no plant damage at 0 and complete plant death at 100. Figure 1 shows raw control data at 12 weeks after treatment (WAT) for 4 replicate plots of each treatment at each of 2 trial locations (site 1 in red tones, site 2 in grey).