How to optimise glyphosate and the latest on herbicide resistance

1. Understanding glyphosate
resistance in ryegrass
Plant Science
Consulting

2. Glyphosate resistance
W in te r w e e d s
Y e a r
Numberofpopulations
1 9 9 6 2 0 0 0 2 0 0 4 2 0 0 8 2 0 1 2
0
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
6 0 0
A n n u al ryeg rass
W ild rad ish
R e d b ro m e
G re a t b ro m e
S u m m e r w e e d s
Y e a r
Numberofpopulations
2 0 0 6 2 0 0 8 2 0 1 0 2 0 1 2 2 0 1 4
0
2 0
4 0
6 0
8 0
1 0 0 B arn y ard g ra ss
L iv e rs e e d g ra s s
F le a b a n e
W in d m ill g rass
S o w th is tle
1996-2014 2007-2014

3. Confirmed cases in Australia

4. Situation Number of sites States
Broadacre
cropping
Chemical fallow 32 NSW
Winter grains
Summer grains
Irrigated crops
295
1
1
Vic, SA, WA, NSW
NSW
SA
Horticulture Tree crops 10 NSW, SA
Vine crops
Vegetables
25
2
SA, WA
Vic
Other Driveway 5 NSW, Vic, SA, WA
Fence line /Crop
margin
Around buildings
89
2
NSW, SA, Vic, WA
NSW
Irrigation channel
/Drain
14 NSW, SA, Vic
Airstrip 1 SA
Railway 2 WA, NSW
Roadside 95 SA, NSW, WA
Where & why has glyphosate resistant ryegrass evolved?
Intensive use of glyphosate >15yr with little alternative weed control practices

5. 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)

6. 2015 random weed survey- Wimmera
Incidence of glyphosate resistance=9%

7. 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.

8. Increasing the level of glyphosate resistance:
mechanisms are additiveSurvival(%)
TS
S
Translocation
Cross: Translocation + TS

9. 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)

10. 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

11. 2016 Quick-Test Glyphosate resistance results
• Received April-June, 2016
• 20 ryegrass plant samples from knockdowns for Glyphosate
testing
• 14 = not resistant
• 6 = resistant

12. 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

13. 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).

14. Elmore Vic
Some 2016 farmer results from 2016 Quick-Tests from Victoria

15. Lake Bolac , Vic
Some 2016 farmer results from 2016 Quick-Tests from Victoria

16. Some 2016 farmer results from 2016 Quick-Tests from SA
Bordertown, SA

17. Some 2016 farmer results from 2016 Quick-Tests from SA
Cummins, SA

18. Some 2016 farmer results from 2016 Quick-Tests from WA
Mukinbudin, WA

19. Some 2016 farmer results from 2016 Quick-Tests from WA
Esperance, WA

20. 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 29
1.5 300 25
2.0 100 15
3.0 125 10
 Increasing rates can improve control of plants resistant to lower rates.

21. Increasing the level of glyphosate resistance:
mechanisms are additiveSurvival(%)
TS
S
Translocation
Cross: Translocation + TS

22. Plant Science
Consulting
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

23. Slight increase in control from 1L to 3L glyphosate

24. Weak and strong glyphosate survivor from same paddock

25. Weak glyphosate survivor

26. Crop Margins- Fenceline control?
Paraquat mixtures,
bromacil (Uragan)
2L/ha Glyphosate
Use residuals along fencelines early in the season starting from pre-sowing

27. Control of Glyphosate -R ryegrass on a fence
line in Kapunda SA with herbicide mixtures-
2013
Fenceline 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

28. Life Impact The University of Adelaide

29. Life Impact The University of Adelaide

30. Life Impact The University of Adelaide

31. www.plantscienceconsulting.com.au
PLANT SCIENCE CONSULTING
RESISTANCE TESTING

32. 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.

33. 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

34. The End
Plant Science
Consulting