Optimising the impact of glyphosate

1. Optimising the impact of
glyphosate
- Glyphosate resistance
- Factors affecting glyphosate performance
- Improving glyphosate performance
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. Where & why has glyphosate resistant ryegrass evolved?
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
Intensive use of glyphosate >15yr with little alternative weed control practices

5. Uni of Adelaide random weed surveys between 2004-2014
(Glyphosate resistance)
16%
(2012)
1%
(2013)

6. Facts about glyphosate resistant weeds
• All growth stages are resistant- seedlings,
pollen etc.
• Younger growth stages can be more sensitive.
• Resistance transferred by pollen & seed
• Progeny from survivors can be more resistant
(accumulation of mechanisms)

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

8. Reduced glyphosate efficacy
– Herbicide resistance (weak or strong)
– Depends on type of resistance mechanism
• Target-site resistance: weak to strong (not common)
• Increased expression of EPSP (brome)
• Uptake and translocation/ sequestration (common)
– Depends on the nr of resistance mechanisms
present in individuals

9. 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

10. Reduced glyphosate efficacy
• The below factors are not independent of each
other:
– Treating older/ larger plants
– Poor coverage  sub-lethal rate
• Nozzles, water rates, calibration
– 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  sub-lethal effect

11. 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 can improve control of HR individuals.
– Avoid using higher rates unless a resistance test confirms effective.
– 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).
– Test for glyphosate resistance (several rates) important.

12. Quick-Test: Survivors resistant ??

13. Glyphosate resistance testing
• Seed Testing from 2014:
– 275 ryegrass samples & 251 Glyphosate testing
requests (91%)
– Data not available on % resistant samples
• Seed Testing from 2013:
– 305 ryegrass samples & 232 Glyphosate testing
requests (76%)
– 71% exhibited glyphosate resistance

14. 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

15. Are survivors always Glyphosate resistant?
Paraquat mixtures,
bromacil
2L/ha Glyphosate

16. Control of Glyphosate -R ryegrass on a fence
line in Kapunda SA with herbicide mixtures-
2013
Fenceline was sprayed in late winter, 2013

17. Kapunda SA, 2013
At
spraying
Untreated
Uragan 3kg/ha + Basta 5 L/haUragan 3kg/ha + Paraquat 2 L/ha

18. Life Impact The University of Adelaide

19. Life Impact The University of Adelaide

20. Life Impact The University of Adelaide

21. Life Impact The University of Adelaide

22. Life Impact The University of Adelaide

23. Life Impact The University of Adelaide

24. The End
Plant Science
Consulting