1. Knockdown Herbicide Resistance

2. 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

3. 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

4. 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

5. 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.

6. 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

7. 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

8. 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