WESSEX
The Illusory Benefits of Herbicide Resistant Crops
Set out below are important extracts from a paper
presented at the 1997
British Crop Protection Conference in Brighton, England,
on "North American
Developments in Herbicide Tolerant Crops" by M
D K OWEN, of
Iowa State University.
The paper concludes that the use of herbicide resistant
crops, including
genetically engineered varieties, are unlikely to provide
farmers with
economic advantages over existing weed management
strategies. The full
paper can be viewed at http://www.weeds.iastate.edu/weednews/Brighton.htm
Although this paper dates from 1997 it has since become
clear from other
reports that agronomists in the US are now advising
growers of Roundup Ready
soya beans, for example, to use multiple applications of
glyphosphate on
these crops (or to use residual herbicides in addition to
glyphosphate) in
order to achieve intended levels of weed control (see
footnote). This
technology was originally marketed as requiring just a
single application of Roundup but in
many cases this has not given the intended (i.e
weed-free) results.
Please note the following before reading the
extracts:
1) The paper refers to herbicide
resistant crops in general, not just those
which have been genetically engineered for such purposes.
2) Weed resistance to herbicides already
commonly develops because of the
over-use of a particular herbicide, through natural
selection/mutation of
weed species in response.
This phenomenon already exists whether or not there is an
additional risk of
herbicide resistance development in weeds through gene
transfer between
crops and related weed species.
3) Results from both the 1997 and
now the 1998 harvests demonstrate that in
most cases yields from genetically engineered Roundup
Ready soya varieties
are lower than non-modified varieties (see
footnote).
4) Total weed kill (a concept
promoted by biotechnology companies in
marketing GM herbicide resistant varieties) can often
only be achieved by:
- using a
single application of Roundup at a late stage of crop
development resulting in yield losses
OR
- using
multiple applications of Roundup (and/or residual
herbicides) throughout the life-cycle of the crop
These scenarios have the double disadvantage of producing
lower profits for
farmers (through low output or high input costs) as well
as destroying farm
biodiversity (see Iowa State University report on
potential effects on
Monarch butterfly at http://www.weeds.iastate.edu/weednews/monarchs.htm
)
5) Because of the lack of objective
impartial advice on these matters US
farmers are often unaware of these trade-offs, with the
result that both
farm economics and farm environment are frequently worse
of than if more
conventional approaches to farm weed management were
utilised.
6) Herbicide resistant crops have been
marketed to farmers on the basis of
simplifying management. In practice they often
complicate it for those not
prepared to accept yield penalties arising when leaving
weed control until
late in the growing season (the latter is the strategy
usually necessary for total weed
kill where only one application of a broadspectrum
herbicide like glyphosphate is to be
used).
7) US farmers have become unnecessarily
obsessed with "total weed kill" in
their crops thanks to pressure from their agro-chemical
suppliers. UK research shows that
reduced weed-kill below certain thresholds can be
tolerated (depending on species)
without substantial effect on yield, provided control of
weed populations
above such levels is achieved early in the growing
season.
In these circumstances it is tempting to describe the
prevalence of
herbicide resistant crops in the US as "a victory of
marketing over science and genuine utility".
What farmers usually get to hear about GM crops from
their suppliers ("the benefits") is not
in
practice usually what is delivered (the losses).
Herbicide resistant crops are generally only for those
farmers who don't
know how to farm properly or who can't be bothered to.
In the end this role of protecting agricultural
incompetence is the sole
"justification" (see footnote)
for taking huge risks with global food
safety and the environment when introducing genetically
engineered crops
incorporating such attributes. This role applies both to
herbicide resistant
crops as well as those with in-built insecticides (the
latter is another
similar but slightly different story - see Novartis
desperate to prevent GM Bt corn crop obsolescence).
Messrs Blair and Clinton (and UK farmers) please take
note.
NATURAL LAW PARTY WESSEX
nlpwessex@bigfoot.com
www.btinternet.com/~nlpwessex
----------------------------------------------------------------------------
-----------------------------------------------
EXTRACTS FROM IOWA STATE UNIVERSITY PAPER ON
HERBICIDE TOLERANT CROPS
----------------------------------------------------------------------------
------------------------------------------------------------------------
Objectively, when considering the use of
herbicide-tolerant corn or
soybeans, and the appropriate herbicide, weed management
is not conceptually
different than where traditional crop varieties and
herbicide programs are
used. However, farmer expectations are considerably
greater with the new
technology compared to existing crops and herbicide
treatments. Farmers
generally have failed to recognize the changes in
management skills required
to effectively use the herbicide tolerant crops. While
the herbicide
tolerant crops may have some advantages compared to
current practices, their
use also results in acceptance of risks associated with
the technology.
----------------------------------------------------------------------------
Hess (1996) indicates that the risks associated with an
integrated weed
management system based on herbicide-tolerant crops are
due to a lack of
knowledge about the ecology and biology of the crop and
associated weeds.
Farmer expectations for weed control are greater than
what the use of these
strategies, in conjunction with herbicide-tolerant crops,
will provide.
----------------------------------------------------------------------------
The author suggests that herbicide-tolerant crops and the
resultant use of
specific herbicides will increase the potential for the
development of
resistant weed populations, but the technology could also
be used
effectively to deter weed resistance. Even if, as
suggested by the industry,
there is little potential for resistance to glyphosate to
develop in weed
populations (Anon., 1997), selection will still occur
resulting in weed
populations that are not effectively managed by the
herbicide (Radosevich &
Holt, 1984).
----------------------------------------------------------------------------
Ideally, herbicide-tolerant crops will improve the use of
alternative weed
management strategies. Wyse (1992) and Burnside (1996)
suggest that
herbicide-tolerant crop technology will increase the
utilization of
alternative strategies for weed management. However, a
recent survey
conducted by the Weed Issue Team at Iowa State
University, and supported by
the Leopold Center for Sustainable Agriculture,
demonstrates clearly that it
is unlikely that herbicide-tolerant crop technology will
increase the use of
alternative weed management strategies.
----------------------------------------------------------------------------
Farmers have expectations for weed control that are
unreasonable from an
environmental, ecological, and economic perspective. The
herbicide industry
has done an effective job of educating farmers about the
level of weed
control herbicides will provide and the consistency that
this level of
efficacy will be delivered. As a result, farmers have
learned that weed
control is synonymous with weed-free and a zero-tolerance
for weed escapes
now exists in much of the Midwest.
----------------------------------------------------------------------------
The expectation by farmers that herbicide-tolerant crops
will improve
potential yields, and thus economics, by eliminating
risks of weed
interference is not likely to be realized. Economic
models suggest that
herbicide-tolerant crops will not likely impact the
economics of crop
production (Tauer & Love, 1989). Typically, the level
of weed control
provided by herbicide-tolerant crop management systems is
equal, but no
better than conventional systems. Farmers also expect
weed control costs to
be reduced when herbicide-tolerant crop management
systems are used.
Experience in Iowa suggests that the cost of weed control
with the new
technology is similar to existing systems.
----------------------------------------------------------------------------
In Iowa, herbicide drift complaints were higher in 1997
than in past years
(Charles Eckerman, Iowa Department of Agriculture and
Land Stewardship,
personal communication). The increased use of
herbicide-tolerant crops and
the resultant herbicide applications possibly contributed
to this increase.
------------------------------------------------------------------------
Glufosinate-tolerant corn, in conjunction with
glufosinate, were positioned
as a strategy to manage problem weeds and for use in no
tillage production
systems. Often, the glufosinate was applied in
combination with a residual
herbicide. Farmer success was varied, depending on the
management skills and
expectations. Performance of glufosinate-based systems in
Iowa State
University research was variable depending on the level
of weed infestation
and environmental conditions.
-----------------------------------------------------------------
Glyphosate-tolerant soybean varieties are viewed by
farmers as the answer to
all weed management problems. Monsanto has positioned
this technology in no
tillage and narrow row spacing systems and farmers
presume that it will
eliminate all risks associated with weed control. In
1996, in Iowa planting
was very late and, as a result most of the postemergence
herbicide
applications were applied in late June and July. At this
time, most of the
weed germination events had occurred and a single
application of a
postemergence herbicide was generally effective.
In 1997, planting occurred early and weed germination
required an earlier
application of the postemergence treatments. In many
instances, unless
alternative weed management was included, second and
third applications were
considered necessary by farmers. Glyphosate-tolerant
soybeans allowed these
later applications. Experiences in 1997 suggest that
better management
skills are required and often second applications may be
needed for
glyphosate-based weed control systems.
----------------------------------------------------------------------------
The issue of yield potential with glyphosate-tolerant
soybean varieties was
also a point of discussion. It is suggested that there is
no loss of genetic
yield potential with the glyphosate-tolerant soybean
varieties (Harper,
1997) yet farmer complaints from 1996 experiences were in
evidence. Further
investigation suggests that many of the reported
"low" yields were
attributable to delayed glyphosate applications resulting
in weed
interference. As with all postemergence herbicide
systems, management skills
are important. The understanding of crop/weed
interaction, the impact of the
environment on plant development, and the implications of
weed populations
on potential crop loss are critically important for
maximizing yield
potential; these are not simple strategies!
----------------------------------------------------------------------------
One of criticisms about weed management programs based on
a single herbicide
is the potential for select resistant weed populations
(Duke et al., 1991).
Monsanto has suggested that due to the mechanism of
action, weed resistance
will not occur (Anon., 1997). Weed scientist have
cautioned that regardless
of whether or not resistance in weeds does develop,
population shifts to
weeds that are more tolerant to a particular herbicide or
"avoid" the
strategy are likely (Holt, 1994).
Experiences in Iowa during 1997 suggest that these
population shifts can
occur rapidly. Common waterhemp (Amaranthus rudis)
populations demonstrate
delayed germination and have "avoided" planned
glyphosate applications.
Velvetleaf (Abutilon theophrasti) demonstrates greater
tolerance to
glyphosate and farmers are reporting problems controlling
this weed with the
rates of glyphosate for which they are willing to pay.
----------------------------------------------------------------------------
Farmers have extremely high expectations for weed control
resulting from the
herbicide tolerant crop systems. Importantly, the use of
herbicide tolerant
crops and appropriate herbicides is perceived to require
lower management
than conventional weed management strategies. Evidence
suggests this is not
the case.
Proponents suggest that there will be increased use of
alternative
management strategies as a result of the herbicide
tolerant crop systems.
However, given farmer expectations and marketing
strategies, it is unlikely
that alternative strategies will be used, and in fact, a
greater reliance
placed upon herbicides for weed control. When considered
objectively, the
use of herbicide tolerant crops as a weed management
strategy does not
differ greatly from current strategies.
----------------------------------------------------------------------------
----------------------------------------------------------------------------
FOOTNOTE:
Here is an additional comment (17 March 1999) on
the Roundup Ready situation
in the US from independent agronomist Dr Charles Benbrook
who is author of the book
"Pest Management at the Crossroads" (1996) and
and who is the former Executive
Director of the Board on Agriculture for the US National
Academy of Sciences (italics ours):
"......Every independent set of data, recent
analysis of RR beans I have
seen reaches the same conclusion; the technology
increases costs somewhat,
but imposes a 'price' farmers are willing to pay for the
simplicity/robustness of the weed management
system. Oplinger et al. end
their paper saying: 'It is anticipated that soybean
growers will continue
to increase acres planted to RR varieties and will
sacrifice yield for ease
of weed control.' They will also sacrifice
some net income per acre.
This is a perfectly rational reason for farmers to adopt
the technology;
weed management is probably the number one management
challenge all soybean
farmers face.
Monsanto should not be ashamed to cite these reasons in
explaining why the technology is being adopted. But
Monsanto needs to drop
the "feeding the world", "lowering
costs", "lowering pesticide use" claims
because they do not hold water and will
undermine, further, the reputation
of the corporation, and in so doing feed the already
considerable cynicism
abroad about the trustworthiness of this company.....
.....As weed shifts continue in areas planted heavily to
RR beans, and as
resistance spreads to additional weed species (the first
signs of tolerant
weeds are appearing in several states), farmers
will have to increase rates of Roundup
applications and intensify use of other active
ingredients, to fill gaps in control.
Costs
will rise, the income squeeze will get even worse.
Contrary to a Monsanto scientist's claim on the NPR
piece, Roundup
does not kill everything green except for transgenic crop
varieties. If
that were the case, most farmers using RR systems would
not be applying at
least 2, and on many farms, three additional active
ingredients."
Charles
Benbrook
208-263-5236 (voice)
Benbrook Consulting
Services
208-263-7342 (fax)
5085 Upper Pack River
Road
benbrook@hillnet.com
[e-mail]
Sandpoint, Idaho
83864
http://www.pmac.net
Benbrook Consulting Services (BCS) provides a public
service to those working to
advance the sciences and art of biointensive
Integrated Pest Management.
Dr. Charles M. Benbrook is a consultant working on
environmental, food
safety and pest management issues.
(Natural Law Party Wessex - March 1998)
Monsanto
approach to sustainability
Will GM crops deliver benefits to
farmers? - some realities behind biotechnology myths