Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 4427 IREC Farmers' Newsletter No. 197 — Autumn 2017 RISK OF RESISTANCE TO KNOCKDOWN HERBICIDES Limited options for weed management along irrigation infrastructure is putting additional pressure on the longevity of knockdown herbicides in irrigated farming systems. l  Non-cropped areas of irrigation farms are high risk areas for the build-up of herbicide resistant weeds, particularly resistance to glyphosate. l  A survey of cotton farms in 2016–17 showed glyphosate resistance in a high proportion of fleabane, feathertop Rhodes grass, windmill grass and sowthistle samples. l  With widespread areas of zero and minimum tillage, knockdown herbicides provide effective weed control but weed management tactics must be diversified to preserve the longevity of these useful herbicides in cropping systems. l  Individual plants that survive a spray application may be a sign of resistance in the plant population. A second warning sign is the need for higher rates of herbicide to achieve the same results as in previous years. Herbicide resistance is frequently identified first along fence lines, roadways and irrigation channels where herbicide use tends to be the same year in, year out. Cindy Benjamin WeedSmart OFTEN less attention is paid to herbicide efficacy or survivor weeds in non-productive areas of the farm compared with cropped areas. This can be a high risk practice unless survivors are removed after every spray application as there is no crop competition to restrict weed growth, resulting in production of large volumes of seed. Eric Koetz, NSW DPI weeds research agronomist, said the limited options for managing weeds along irrigation infrastructure and other non-crop areas is a problem, and is putting additional pressure on the longevity of knockdown herbicides in irrigated farming systems. Build-up of resistance on cotton farms “A recent survey of cotton fields in Queensland and NSW showed that cotton paddocks were generally relatively weed free, however the incidence of resistance to glyphosate is quite high in fleabane and QUICK TAKE