This paper outlines three case studies of weed species that have demonstrated a great propensity for HR gene flow: B. scoparia in western North America, Amaranthus palmeri S. Watson (Palmer amaranth) in the United States (U.S.), and Lolium rigidum Gaud. (annual or rigid ryegrass) in Australia. These three species share three common features: (1) a top troublesome and economically damaging weed in their respective jurisdictions; (2) high incidence of multiple resistance in populations; and (3) rapid expansion of resistance incidence across jurisdictions in a short period of time.
Preventing the introduction of weeds into the farming system through sowing of clean seeds is an essential component of weed management. The weed seed contamination of cleaned grain and herbicide resistance levels of the recovered weed seeds were examined in a study conducted across 74 farms in the Western Australian grainbelt.