Post on 16-Aug-2020
transcript
Silsoe Spray Applications Unit Ltd
Post-emergence herbicide application
Clare Butler Ellis,
Silsoe Spray Applications Unit
BCPC weed review Nov 2018
Silsoe Spray Applications Unit Ltd
Let’s go back in history…..
In 1994, a review of application for post-emergence herbicides was published
• Knocke, M (1994) Effect of droplet size and carrier volume on performance of foliage-applied herbicides. Crop protection 13 163-178• 146 references
• 1950 – 1993
• Large number of studies from the 1980s
Silsoe Spray Applications Unit Ltd
Knoche’s main conclusions
• Findings were often not consistent across different studies• Clear trends sometimes difficult to identify
• Performance improved with reducing droplet size• Most consistent for systemic herbicides
• Volume effects not so clear• Optimum volume between 100 and 400 L/ha• Most consistent for difficult-to-wet plants• Glyphosate had consistently better performance for
reduced volume
Silsoe Spray Applications Unit Ltd
Since 1994 -
• Air-induction nozzles
• Angled nozzles
• Loss of chemicals
• Improved formulations
We therefore know less now than we did in 1994!
Silsoe Spray Applications Unit Ltd
More recent UK reviews – covering all sprayed PPPs
• HGCA nozzle chart – first in 2004?
• Defra desk study: A review of methods of reducing drift without compromising efficacy (Orson, Miller) 2006 –PS2010• ~ 50 references (many from the 1980s)• 8 refs on post-em herbicide efficacy since 1994
• Further revisions of the HGCA nozzle chart (last in 2010) much less formal
• There is a significant number of studies on herbicides since 1994 – not so much from the UK, but Europe and USA
Silsoe Spray Applications Unit Ltd
But we still have some understanding of the basic principles from which we can deduce performance in the absence of data
• How application affects the quantity of spray deposited on plants• Should correlate to efficacy providing the experiment is on the right part
of the dose-response curve
• How application affects the area of plant surface covered by spray • Hypothesised correlation with efficacy in some circumstances
• Not sure that this is supported by experimental data
Silsoe Spray Applications Unit Ltd
Effect of volume on quantity of spray deposited on the target
Silsoe Spray Applications Unit Ltd
Silsoe Spray Applications Unit Ltd
Effect of volume on deposit quantity:deposit on 10 ryegrass plants
0
0.5
1
1.5
2
2.5
3
3.5
37 73 164
De
po
sit
qu
anti
ty, u
l
Applied volume, l/ha
Silsoe Spray Applications Unit Ltd
Silsoe Spray Applications Unit Ltd
Effect of volume on deposit quantity: deposit on winter wheat crop at T2 timing
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
FF110 025 FF110 025 2xFF110 025 FF110 05 FF110 05
100 l/ha 200 l/ha 200 l/ha 200 l/ha 400 l/ha
12 km/h 6 mk/h 12 km/h 12 km/h 6 km/h
De
po
sit
on
wh
ole
pla
nt,
ul/
g
Application
Silsoe Spray Applications Unit Ltd
Silsoe Spray Applications Unit Ltd
Normalised (active substance) deposit on whole plant
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14
16
18
20
22
24
0 200 400 600 800 1000 1200
ul/
g
Applied volume, L/ha
Silsoe Spray Applications Unit Ltd
• Less active ingredient deposited on plants for higher volumes
• Greatest effect on small vertical structures
• No effect on soil deposits
Effect of volume on deposit quantity:
Silsoe Spray Applications Unit Ltd
Effect of droplet size on quantity of spray deposited on plants
• Smaller droplets = higher deposits
• Lower velocities = higher deposits
• Air induction nozzles have larger droplets at lower velocities – with air bubbles lower deposits (droplet energy = ½ m v2)
Silsoe Spray Applications Unit Ltd
Effect of droplet size on quantity deposited –10 ryegrass plants
0
0.5
1
1.5
2
2.5
3
3.5
37 73 164
De
po
site
d q
uan
tity
, ul
Applied volume, l/ha
Flat fan nozzle
Air induction nozzle
Silsoe Spray Applications Unit Ltd
Effect of droplet size on deposit quantity – wind tunnel, small targets
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
100 300 500 700 900
De
po
sit,
ul
VMD, um
FF AI
Silsoe Spray Applications Unit Ltd
Effect of volume and droplet size on ‘coverage’ of the target
Silsoe Spray Applications Unit Ltd
Effect of application on area covered by spray liquid
0.0
20.0
40.0
60.0
80.0
0 50 100 150 200
% c
ove
rage
Application volume, l/ha
Conventional
AI small
AI large
Silsoe Spray Applications Unit Ltd
100 L/ha FF vs 200 L/ha AI
Silsoe Spray Applications Unit Ltd
But in 2018, formulation is everything …
Silsoe Spray Applications Unit Ltd
Area covered by droplets may be large but area covered by active substance is independent
of water volume
waterActive substance
Coverage by active ingredient –suspension or emulsion
Silsoe Spray Applications Unit Ltd
Effect of application on ‘coverage’
• … is complicated!
• Greater area of plant covered by water at higher volumes
• Do you need a greater area of plant covered by water???
• How the active substance is distributed is likely to be more important
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Effect of volume on distribution within the canopy
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Penetration into a canopy
• Labels often state for denser crops and later growth stages, use higher volumes
• 3 years of data from an HGCA-funded project on cereals• Application technique much less important than growth
stage of crop
• Other data on other crops shows similar results:-• Increasing volume does not increase penetration
Silsoe Spray Applications Unit Ltd
Effect of volume on distribution in canopy - wheat
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
FF110 025 FF110 025 2xFF110 025 FF110 05 FF110 05
100 l/ha 200 l/ha 200 l/ha 200 l/ha 400 l/ha
12 km/h 6 mk/h 12 km/h 12 km/h 6 km/h
ul/
g
Lower stem
Silsoe Spray Applications Unit Ltd
What do we know about low volumes and weed control since 1994?
• Low volumes LINK project found no significant change in performance with volumes down to 25 l/ha (flat fan, twin fluid and air induction nozzles)• Grass & broadleaved weeds
• Biggest effect was seen between traditional flat fan and large droplet air induction nozzles
• Soil applied herbicides – information is confusing• HGCA & TAG funded trials showed pre-emergence weed treatments
tended to work better at 100 l/ha than at 200 l/ha
• A brief review of published data suggests no volume effect (paper in CPSB Feb 2017)
Silsoe Spray Applications Unit Ltd
Effect of spray volume and nozzle type on 1-2 leaf rye-grass with 0.7 l/ha Grasp
0
20
40
60
80
100
120
Flat fan AI Flat fan AI Flat fan AI
2002, lsd = 23 2003, lsd = 16 2006, lsd = 12
% c
on
tro
l ry
eg
ras
s
37 l/ha 73 l/ha 164/147 l/ha
Silsoe Spray Applications Unit Ltd
Nozzle angling
• Nozzles angled by 30o or more now commercially available• Forwards, backwards, alternate f&b, twin, asymmetric
twin etc• Or take your favourite nozzle and put into a twin cap or
single angled cap
• Put more on vertical targets• Forward angling has bigger effect than backwards
• Have little impact on other targets
• Particularly effective for small upright grass weeds
Silsoe Spray Applications Unit Ltd
Effect of nozzle angle on relative performance of herbicide on perennial ryegrass
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
LD-015, 120l/ha expt 1
LD-015, 120l/ha expt 2
FF-02, 150 l/ha AI-015, 120l/ha
Re
lati
ve c
on
tro
l
45 forward30 forward10 back30 back45 back
P K Jensen, 2010, International Advances in Pesticide Application, p81-88
Silsoe Spray Applications Unit Ltd
Field studies into the effect of application on efficacy are difficult -
• Large areas are needed for full-scale equipment at realistic speeds
• Weeds are patchy over large areas• Pre-emergence is particularly challenging as you don’t have ‘before’
and ‘after’
• Good control of application difficult with real sprayers
• Plot sprayers are not relevant to real application conditions
• Everything is connected – so usually cannot change one parameter without changing something else
• Need to be on the right part of the dose-response curve
• Knoche’s review shows that multiple trials needed to identify the main ‘trends’
Silsoe Spray Applications Unit Ltd
Understanding underlying processes is very important
• Target location on plant
• Mode of action
• Uptake into plant/movement across surface
• Distribution over target
• Pre- and post-application losses
SSAU’s approach is to explore underlying mechanisms to develop hypotheses and inform limited field trials – most cost effective
Silsoe Spray Applications Unit Ltd
To summarise:• Physics suggests low application volumes may give better
performance than high, for a number of reasons
• More retained on plants
• Higher concentration may be more important than higher ‘coverage’
• Good formulation can also result in high ‘coverage’ even with low volumes
• No reduction in pesticide reaching the lower part of a cereal canopy (within typical practical volume ranges)
• Consistent, as far as we can establish, with measurements of efficacy.
• Where a high level of coverage of the plant surface by water is genuinely beneficial, higher volumes may work best.
Silsoe Spray Applications Unit Ltd
Thank you for your attention
Thanks to the team at SSAU who contributed to all aspects of this work