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Understanding glyphosate resistance in ryegrass
Plant ScienceConsulting
Glyphosate resistance
Winter weeds
Year
Num
ber o
f pop
ulat
ions
1996 2000 2004 2008 20120
100
200
300
400
500
600Annual ryegrassWild radishRed bromeGreat brome
Summer weeds
Year
Num
ber o
f pop
ulat
ions
2006 2008 2010 2012 20140
20
40
60
80
100 Barnyard grassLiverseed grassFleabaneWindmill grassSowthistle
1996-2014 2007-2014
Confirmed cases in Australia
Where & why has glyphosate resistant ryegrass evolved?
Intensive use of glyphosate >15yr with little alternative weed control practices
Points indicate fields surveyed by the University of Adelaide GRDC funded random weed surveys.
Incidence of Glyphosate resistant fields in red
16%(2012)
1% (2013)
3% (2015)
9% (2015)
1% (2014)
4% (2014)
0% (2012)
2015 random weed survey- WimmeraIncidence of glyphosate resistance=9%
Facts about glyphosate resistant weeds
• All growth stages are resistant- seedlings, pollen etc. • Younger growth stages usually more sensitive.• Resistance transferred by pollen & seed• Progeny from survivors usually more resistant
(accumulation of mechanisms)• From fencelines glyphosate resistance detected out to
at least 50m• Some glyphosate-resistant populations have reduced
fitness (less competitive than susceptible ryegrass in the absence of glyphosate). Produce less seed.
Increasing the level of glyphosate resistance: mechanisms are additive
Surv
ival
(%)
TS
S
Translocation
Cross: Translocation + TS
Reduced glyphosate efficacy
1. Herbicide resistance (weak or strong)
– Depends on type of resistance mechanism
1. Translocation/ sequestration (to leaf tips)- ryegrass
2. Target-site resistance: weak R detected in ryegrass
– Pro106 (S) to Ser/Thr at target site (EPSPS gene)
3. Both 1 & 2 in ryegrass
4. Increased expression of EPSP (brome) (Amaranthus spp in
USA (waterhemp, palmer amaranth)
Reduced glyphosate efficacy
2. Other factors:– Treating older/ larger plants eg. fencelines in spring!!– Poor coverage sub-lethal rate
• Nozzles, water rates, calibration, correct boom height– Stressed plants
• temperature extremes, moisture, nutrition, pest damage etc. affect translocation etc.
• Reduced efficacy at high temperatures (better effect spraying high 20oC’s than 30oC’s)
– Dust covering leaves reduced effect
2016 Quick-Test Glyphosate resistance results• Received April-June, 2016
• 20 ryegrass plant samples from knockdowns for Glyphosate
testing
• 14 = not resistant
• 6 = resistant
Percent survival (%) of a selection of grower resistance tests from 2013 and 2014 treated with Glyphosate (540g ai/L). Data ranked according to percent survival at 1000ml/ha.
Different resistance profiles! Data courtesy of P. Boutsalis, Plant Science Consulting
Improving glyphosate efficacy
– Increased glyphosate rates can aid in buffering the effect of:• Treating older plants
• stressed plants
• high temperatures
• Poor coverage
• Dust covering leaves
– Increased glyphosate rates sometimes improve control of resistant individuals.
– Test for glyphosate resistance (several rates) to determine resistance level (Quick-Test or Seed test).
– Do not let glyphosate resistant individuals set seed to avoid accumulation of resistance mechanisms.
– Rotate from glyphosate even if no resistance (paraquat products/ residuals eg. bromacil along fencelines/ non-cropped areas).
Elmore Vic
Some 2016 farmer results from 2016 Quick-Tests from Victoria
Lake Bolac , Vic
Some 2016 farmer results from 2016 Quick-Tests from Victoria
Some 2016 farmer results from 2016 Quick-Tests from SA
Bordertown, SA
Some 2016 farmer results from 2016 Quick-Tests from SA
Cummins, SA
Some 2016 farmer results from 2016 Quick-Tests from WA
Mukinbudin, WA
Some 2016 farmer results from 2016 Quick-Tests from WA
Esperance, WA
Glyphosate resistance in ryegrass. Results from 2015 Plant Science Consulting Quick-Test
and Seed testing of farmer samples
Glyphosate 540 rate (L/ha)
Ryegrass Samples Tested % resistant
1.0 200 291.5 300 252.0 100 153.0 125 10
Increasing rates can improve control of plants resistant to lower rates.
Increasing the level of glyphosate resistance: mechanisms are additive
Surv
ival
(%)
TS
S
Translocation
Cross: Translocation + TS
Plant ScienceConsulting
1000ml/ha 1500ml/ha
Glyphosate 540g ai/L
1000ml/ha 1500ml/ha
Survivors to 1000ml/ha indicates low-level glyphosate resistance
which is becoming common
Slight increase in control from 1L to 3L glyphosate
Weak and strong glyphosate survivor from same paddock
Weak glyphosate survivor
Crop Margins- Fenceline control?
Paraquat mixtures, bromacil (Uragan)
2L/ha Glyphosate
Use residuals along fencelines early in the season starting from pre-sowing
Control of Glyphosate -R ryegrass on a fence line in Kapunda SA with herbicide mixtures-
2013Fenceline was sprayed in late winter, 2013
Rather than treating fencelines (large plants) in spring:
- Use knockdown+residuals before sowing starts or once sowing finished
- Sow as close as possible to fenceline with crop-residuals crop competition
along fenceline = fewer ryegrass seeds
- When sowing outer laps, use outer nozzle to apply residuals along fenceline.
- Mowing is used in some cases
Life Impact The University of Adelaide
Life Impact The University of Adelaide
Life Impact The University of Adelaide
www.plantscienceconsulting.com.au
PLANT SCIENCE CONSULTING
RESISTANCE TESTING
Testing: www.plantscienceconsulting.com.au
Testing Plants Testing Seed
- Even plants with 50+ tillers can be tested!!
- May be interested in a couple of survivors only, eg 5 plants.
Results using Seed Testing
Herbicide Product Rate
Herbicide Group Farmer paddock
(g or ml/ha) Survival(%) Rating
Verdict + 1% Hasten 85 A-FOP 70 RR
Select + 1% Hasten 250 A-DIM 20 R
Select + 1% Hasten 500 A-DIM 0 S
Hussar + 1% Hasten 200 B-SU 90 RRR
Glyphosate 540 1500 M 0 S
Triflur X 1000 D 0 S
The End
Plant ScienceConsulting