Determining the extent of herbicide resistance in the rice growing regions of southern Australia

摘要

Weed seed samples were collected from across the rice-growing regions of southern New South Wales (NSW). These samples were tested against a relevant range of commercial herbicides to establish benchmark levels of resistance for each weed and herbicide combination. High levels of resistance to bensulfuron were detected in the three weed species tested. Approximately 50% of dirty Dora (Cyperus difformis L.), 40% of starfruit (Damasonium minus (R.Br.) Buchenau) and 38% of arrowhead (Sagittaria montevidensis Cham. & Schlechter) samples were resistant. All dirty Dora, arrowhead and starfruit samples were susceptible to all of the other herbicides tested. No barnyard grass samples were classed as resistant to any of the four herbicides tested. A total ofsix barnyard grass species (barnyard grass (Echinochloa crus-galli (L.) P.Beauv.), awnless barnyard grass (E. colona (L.) Link), hairy millet (E. oryzoides (Ard.) Fritsch), prickly barnyard grass (E. microstachya (Wieg.) Rydb), Japanese millet (E. es-culenta (A.Braun) H.Scholz) and channel millet (E. inundata P.W.Michael & Vickery)) were detected. Four species were collected during a first survey and five in the second. Three of the six species were present in both surveys. In a number of the samples two different species were present. These species had slightly different rates of germination that resulted in them being at slightly different growth stages at the time of herbicide application. Where mixed populations occur in the field this is of majorimportance when dealing with any herbicides that have a narrow range of growth stages for effective application. At present, herbicide resistance in weeds of rice appears to be confined to bensulfuron. However it remains important for farmers to implement appropriate herbicide resistance management in order to protect the viability of the herbicide options.