2015 ballarat crop updates-optimising the impact of glyphosate
TRANSCRIPT
Optimising the impact of glyphosate
- Glyphosate resistance- Factors affecting glyphosate performance- Improving glyphosate performance
Plant ScienceConsulting
Glyphosate resistance
Winter weeds
Year
Nu
mb
er o
f p
op
ula
tio
ns
1996 2000 2004 2008 20120
100
200
300
400
500
600
Annual ryegrass
Wild radish
Red brome
Great brome
Summer weeds
Year
Nu
mb
er o
f p
op
ula
tio
ns
2006 2008 2010 2012 20140
20
40
60
80
100 Barnyard grass
Liverseed grass
Fleabane
Windmill grass
Sowthistle
1996-2014 2007-2014
Where & why has glyphosate resistant ryegrass evolved?
Intensive use of glyphosate >15yr with little alternative weed control practices
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)
Increasing the level of glyphosate resistance: mechanisms are additive
Surv
ival
(%)
TS
S
Translocation
Cross: Translocation + TS
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
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
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
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.
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
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
Control of Glyphosate -R ryegrass on a fence line in Kapunda SA with herbicide mixtures-
2013Fenceline was sprayed in late winter, 2013