Knockdown Herbicide Resistance

Increase in glyphosate resistance in 7 years Country Number of species 2011 2018 USA 11 17 Australia 5 Canada 1 6 Czech Republic Brazil 8 Israel 2 Argentina 3 South Africa Chile China Spain Malaysia France Italy In 2011 US had the jump on us. We use glyphosate in a wide range of applications. Big numbers in the US, Brazil & Argentina is RR technology In Australia they are coming from chemical fallow, roadsides and non-crop areas. Heap, 2018

Herbicide fallow; roadsides Herbicide fallow; channels Glyphosate resistant Species – Sept 18 First Year Number of populations Where do you get it? annual ryegrass 1996 678# Everywhere gly is used awnless Barnyard grass 2007 102 herbicide fallow liverseed grass 2008 4 flaxleaf fleabane 2010 65 Roadsides bigly windmill grass 11 Herbicide fallow; roadsides wild radish 3 Herbicide fallow great brome 2011 5 fencelines Tall fleabane 2012 8 roadsides sowthistle 2014 red brome 1 Sweet summer grass Prickly lettuce Feathertop Rhodes grass 2015 Tridax daisy 2016 1 (Ord Irrig) Herbicide fallow; channels Winter grass 2017 3* golf courses Wild / willow-leaved lettuce 2 vegetables Northern barley grass 2018 Fences, buildings # stopped counting; * Multiple Resistance BCDMZ

Glyphosate resistance mechanisms Reduced translocation (metabolic) Altered EPSPS gene (target site) EPSPS gene amplification Fleabanes (Conyza spp.) Crowfoot grass (Eleusine indica) Common ragweed (Ambrosia artemisiifolia) Narrow leaf plantain (Plantago lanceolata) Awnless BYG (Echinochloa colona) Giant ragweed (Ambrosia trifida) Johnsons grass (Sorghum halepense) Palmer amaranth (Amaranthus palmeri) Sour grass (Digitaria insularis) Common water hemp (Amaranthus tuberculatus) Annual ryegrass Brome grass (Bromus diandrus) Italian ryegrass (Oregon, USA) Italian ryegrass (Chile) Italian ryegrass (Arkansas, USA) Three different mechanisms conferring glyphosate resistance to weeds Wild radish – multiple resistance to B, I, F, M

Paraquat resistance Arctotheca calendula Capeweed 1984 Victoria Species Common name Year confirmed State Crop Resistance to other MOAs / herbicides Arctotheca calendula Capeweed 1984 Victoria lucerne diquat (L) Hordeum glaucum Northern barley grass 1983 Hordeum leporinum Barley grass 1988 Vulpia bromoides Silver grass 1990 Mitracarpus hirtus Small square weed 2007 Queensland mangoes Lolium rigidum annual ryegrass 2010 South Australia pasture seed A Wimmera ryegrass M Gamochaeta pensylvanica Cudweed 2015 tomatoes, sugar cane Solanum nigrum Blackberry nightshade Eleusine indica Crowsfoot grass Conyza bonariensis flaxleaf fleabane 2016 NSW grape vines Red arrow – 17 year gap in new cases. Reflects people using more paraquat in response to glyphosate resistance.

Glufosinate – Group N Weed Where Year first confirmed Other modes of action Eleusine indica crowsfoot grass Malaysia - 2 MOAs Malaysia - 4 MOAs 2009 paraquat (L) Fluazifop, butroxydim (A) + paraquat (L) + glyphosate (M) Lolium perenne Perennial Ryegrass New Zealand - 3 MOAs 2015 amitrole (Q) + glyphosate (M) Lolium perenne ssp. multiflorum Italian Ryegrass United States (Oregon) – 2 MOAs New Zealand – 3 MOAs United States (California) 2010 Lolium rigidum Wimmera Ryegrass Greece 2017

Amitrole - Group Q Species Country Year first confirmed Other MOA Agrostis stolonifera Creeping Bentgrass Belgium 1986 Lolium perenne Perennial Ryegrass New Zealand 2015 M + N Lolium perenne ssp. multiflorum Italian Ryegrass Lolium rigidum Wimmera Ryegrass W.A. South Australia 1988 2008 M Poa annua Winter grass 1983 Polygonum aviculare wireweed 1984

Preventing resistance to knockdown herbicides Use tank mixes of two different modes of action at robust rates that are effective on the target species – remember synergy is rare – keep both rates high! Prevent any survivors of spraying from setting seed. Use a double knock – 2 effective herbicide applications or non-herbicide tactics in close succession – 1 to 14 days apart monitor spray effectiveness Rotate modes of action See WEEDsmart “Big 6” for cropping