Tolerance of native wildflower species to postemergence herbicides

Postemergence herbicides may facilitate weed control in native wildflower seed production fields. In a greenhouse study, we assessed the impact of 4 postemergence herbicides (linuron, halosulfuron, imazapic, and pendimethalin) on 4 wildflower species: white prairie clover ( Dalea candida Michx. ex Willd. [Fabaceae]), blanketflower ( Gaillardia aristata Pursh [Asteraceae]), silverleaf phacelia ( Phacelia hastata Douglas ex Lehm. [Hydrophyllaceae], and prairie coneflower ( Ratibida columnifera (Nutt.) Woot. & Standl. [Asteraceae]). Pendimethalin applied at 1.9 kg ai/ha (1.69 lb ai/ac) caused the least seedling injury across all species and therefore may help weed management in wildflower production systems. Although linuron applied at 0.56 kg ai/ha (0.5 lb ai/ac) appeared to be a promising alternative for weed control, oven-dry biomass for G. aristata was reduced by this herbicide. Imazapic and halosulfuron applied at 0.14 kg ai/ha (0.125 lb ai/ac) and 0.048 kg ai/ha (0.042 lb ai/ac), respectively, caused severe damage on wildflower seed lings.