Lisa J. Rew

Non‐native annual grasses have invaded western rangelands in the United States, and novel approaches are needed to supplement existing management strategies. The aim of this study was to investigate biofumigation, the use of Brassicaceae products to suppress weeds, as a control for two non‐native annual grasses (cheatgrass, Bromus tectorum and ventenata, Ventenata dubia ) and its effects on two dominant native perennial grasses (bluebunch wheatgrass, Pseudoroegneria spicata and Idaho fescue, Festuca idahoensis ). We tested the effect of the biofumigant Brassica juncea (brown mustard), applied as seed meal and mulch, on germination metrics of the four grass species in Petri dishes. Germination metrics included emergence and viability, time to cotyledon and radicle emergence and their lengths at 14 days after sowing. Impacts on emergence and viability were assessed using a binomial mixed effects model, while time to cotyledon and radicle emergence and lengths were assessed using linear mixed effects models. Seed meal reduced emergence and viability at lower application rates for V. dubia and F. idahoensis than the other two species. Mulch did not consistently reduce emergence or viability. P. spicata was the least inhibited by the biofumigants. When using seed meal, radicle emergence and length were inhibited in B. tectorum, V. dubia and F. idahoensis and cotyledon emergence and length were inhibited for all. The mulch did not impact these metrics consistently and may not be a viable management tool. The use of seed meal biofumigant to suppress undesired annual grasses in rangelands seems promising, but response is species‐specific.