1. Non-chemical methods of
weed control:
benefits and limitations
Stephen Moss
Rothamsted Research, UK

2. Farmers in EU will have to use
more non-chemical control
methods because:
1. Fewer pesticides available due to EU
regulatory action, and lack of new MOA
2. Increasing pesticide resistance, especially
grass-weeds such as Alopecurus myosuroides
3. New EU regulatory action requiring farmers to
adopt Integrated Pest Management (IPM)
http://www.pesticides.gov.uk (see European Union issues)

3. Loss of pesticides in European Union
How many more can we afford to lose?
Directive 91/414/EEC Comparative risk
assessment and
substitution
Data supplied by the European Crop Protection Association, Nov 2009

4. Black-grass:
“Atlantis” (mesosulfuron+iodosulfuron)
800 g/ha (2x field dose)
ALS TSR Proline 197 mutation
Three resistant populations
A susceptible
population

5. EU Thematic Strategy for Pesticides:
Sustainable use directive
‘Member states should promote low pesticide
input pest management, in particular Integrated
Pest Management………’
‘…….with priority given wherever possible to
non-chemical methods of plant protection…..’
‘…..setting quantitative targets and indicators
aimed at reducing the impact of pesticides on
human health and the environment.’

6. Non-chemical control
of grass-weeds
• Crop rotation
• Ploughing
• Delayed autumn drilling
• Spring cropping
• Fallowing
• Prevent seed return and spread of resistant seeds
• Mechanical weed control (harrowing or hoeing)
• Competitive crops
– Higher seed rates (or at least avoid low seed rates)
– More competitive varieties
– Narrower rows

7. Black-grass
Alopecurus myosuroides

8. Non-chemical control of
Alopecurus myosuroides
(black-grass) in winter wheat
Number of % reduction achieved
Method comparisons
Mean Range
Ploughing 25 67% - 20% to 96%
Delayed drilling 16 37% - 64% to 82%
Higher seed rates 15 30% + 8% to 53%
Competitive cultivars 4 27% + 9% to 36%
Spring Cropping 3 80% +70 to 90%
Fallowing 1 70% +60 to 80%
Based on review, by Lutman & Moss for Syngenta, 2009

9. Higher
seed rate

10. Rating the effectiveness of non-chemical
control methods for Alopecurus myosuroides
on same basis as herbicides
Label
Method
rating
Ploughing MR
Delayed drilling R
Higher seed rates R
Competitive cultivars R
Spring Cropping MS
Fallowing MR
Meso.+Iodo. ‘Atlantis’ S
CRD Effectiveness claims: S = >85%; MS = 75 – 85%; MR = 60 – 75%; R < 60%

11. Weed control
Black-grass R
Rye-grass R
Wild-oats R

12. Why don’t farmers use more
non-chemical control methods?
1. More complex to manage – time constraints
2. Less effective than pesticides
3. Control levels more variable
4. Control levels less predictable
5. More expensive than pesticides
6. No compensation following control failure
7. May not reduce the need for pesticides
8. Little visible evidence of success
9. More risky (to consultant as well as farmer)
10. Less return for supplier of pesticides
11. May have adverse environmental effects
12. Pesticides offer a ‘quicker-fix’
13. Harder manual effort

13. 22 June 2010
Yielded Yielded
10.01 t/ha 9.44 t/ha
2.2 black-grass heads/plant 5.3 black-grass heads/plant
170 seeds/plant 419 seeds/plant
450 wheat seeds 150 wheat
sown/m2 seeds sown/m2

15. ‘Enlightened’
farmer’s gallery

16. “Ten years ago we were drilling Claire at 80 –
120 seeds/m2 in August, and were getting 8.5
– 10 t/ha. We thought we had cracked it by
extending the growing season, but the open
canopies quickly caused problems with grass-
weeds. So now we are drilling later, at higher
seed rates of 300 – 350 seeds/m2, and one of
the first things we look for in a variety is how
competitive it is against black-grass.”
Duncan Andrews, Gloucestershire farmer
Farmers Weekly 20 May 2011

17. IPM (including IWM)
Why has uptake been so limited?
“IPM has a very successful history of
adoption by scientists, pressure groups
and policy makers, but limited success
in terms of adoption by farmers”
IPM in developing countries: the danger of an
ideal. Morse & Buhler (1997). Integrated
Pest Management Review 2, 175-185.

18. Poor adoption of IPM/IWM – why?
“Too much knowledge, not
enough application”

19. ‘TaylorReview,
‘Science for a new age of agriculture’,
2010
“However, there is now widespread
agreement that the focus of research funding
and the accompanying mechanisms of reward
and career opportunity have tilted the balance
of agricultural science towards basic research
and away from applied. This can severely
compromise the translation of research into
commercial practice. ”

20. Technology transfer issues
“…a lot of the eggheads in our research
institutes concentrate on pure science and find it
hard to communicate their ideas widely or simply
enough to change everyday life”
Matthew Naylor, farmer, Farmers Weekly, 2009

21. “We believe it again goes, almost without
saying, that relying upon the same tired
methods to diffuse IWM will not lead to
greater adoption”.
‘Investigating the human dimension of weed
management: new tools of the trade’
Doohan, Wilson, Canales & Parker, 2010
Weed Science 58: 503-510.

22. “Scientific research will be key to
securing future food security” says the
BBSRC
from ‘Food: avoiding a global security
crisis’ in the RASE book, ‘Working for the
future of agriculture’

23. “The application of scientific research will
be key to securing future food security”
says Dr Stephen Moss

24. Influencing farmers
Getting farmers to do what you want by ensuring
that they are willing to do what you want them to do
‘Expert’
Farmer
Stephen Moss, Rothamsted Research

25. Thank you
stephen.moss@rothamsted.ac.uk

26. Good Canadian advice
“ Once viable IWM systems are developed they
must be demonstrated at the field level and a
consistent message must be given by multiple
people at multiple forums over multiple years.
Patience is required by all involved, as
meaningful change is usually a slow process”
‘Ongoing development of integrated weed management
systems on the Canadian prairies’, Blackshaw et al., (2008)
Weed Science 56, 146-150