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  • From: "Lawrence F. London, Jr." <lfl@intrex.net>
  • To: permaculture@lists.ibiblio.org
  • Subject: [permaculture] [Fwd: Resistance to Glyphosate]
  • Date: Thu, 10 Jul 2003 00:40:07 -0700

-------- Original Message --------
Subject: Resistance to Glyphosate
Date: Wed, 9 Jul 2003 14:37:44 -0700
From: Chuck Benbrook <benbrook@HILLNET.COM>
Reply-To: Sustainable Agriculture Network Discussion Group
<SANET-MG@LISTS.IFAS.UFL.EDU>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Excessive reliance on any single pest management tool heightens
the selection pressure imposed on pest populations and sets in motion
evolutionary processes that ultimately will undermine efficacy, as Lewis et
al. pointed out so eloquently in their seminal 1997 article in the
"Proceedings of the NAS." Accordingly, it is no surprise that Roundup
(glyphosate) resistant weeds have evolved in the U.S. and are beginning to
force farmers to add additional herbicides to their weed management programs.

I am writing SANET colleagues to alert them to new evidence of how
fast and broadly resistance is spreading and to ask for help in compiling
information on the likely consequences, i.e. what farmers growing RR crops
will likely have to do/spray to deal with weed escapes and resistance. I
ask for this input because I am going to write something over the next
couple months on the slipping performance of RR technology and what farmers
need to do if they want this technology to last longer than another few years.

Earlier this month university scientists reported the first significant
breakdown in the efficacy of Roundup Ready technology triggered by a
resistant weed. The Associated Press covered the findings in a June 4,
2003 story, "Weed Could Cost Farmers Millions to Fight." University of
Arkansas weed management specialists are projecting that about 600,000
acres in the State will be infested with glyphosate resistant marestail
(also known as horseweed) by next crop year. They estimate that farmers
will have to spend an additional $8.00 to $15.00 per acre to control the
resistant weeds on much of the 600,000 acres next year and annually
thereafter as long as Roundup Ready crops are planted. Some weed
scientists are apparently advocating preventive applications of 2,4-D or
dicamba as a measure to stop the spread of resistance.

The severity of this problem in Arkansas reinforces the urgency of
rethinking how RR technology is used. In recent years in Arkansas, USDA
pesticide use data show that about 3.5 million acres of soybeans have been
grown, with about three-quarters planted to Roundup Ready varieties. About
970,000 acres are planted to cotton, with perhaps one-quarter Roundup
Ready. Accordingly, Roundup Ready technology has been used on some 2.9
million acres annually in recent years, use that has led to a projected
600,000 acres infested with resistant horseweed. This is already about 20
percent of the 2.9 million acres on which Roundup Ready technology has been
used!

Without aggressive measures to control resistant phenotypes, horseweed will
spread throughout regions where Roundup crops are common. These measures
will markedly increase both grower costs and herbicide use. I suspect
other types of weeds will become resistant, if they are not already.

In 1999, Bob Hartzler of Iowa State University wrote a piece re "Will
Roundup Resistance Weeds be a Part of Your Future?" He set out the reasons
why RR technology dramatically increases selection pressure and urged
vigilance in watching for the emergence of resistant phenotypes. Hartzler
has recently returned to the topic and has some striking things to say
about the emergence of glyphosate resistance in the Midwest --

http://www.weeds.iastate.edu/mgmt/2003/monad.shtml

I have also pasted in below a recent story in a Peoria newspaper
that quotes Hartzler. Recent evidence on the levels of resistance in Iowa
has been posted at --

http://www.weeds.iastate.edu/mgmt/2003/glyphosatescreen.shtml

So -- a request. Please pass along any new data/evidence re
glyphosate resistant weeds; any newly recommended glyphosate resistance
management plans; and, information of how farmers will change their
herbicide program if/when they have to contend with resistant
weeds. Please note active ingredients added to the program, rate per acre,
and approximate cost. Thanks, I'll share the results as they come to me at
<benbrook@hillnet.com>

Chuck Benbrook

xxxxxxxxxxxxxxxxxxxxxxx

Journal Star
July 8, 2003
Weed Resistance May Be Issue with Genetically Modified Soybeans
By Steve Tarter

PEORIA, Ill.--An agronomist from Iowa State University has a message for
the Monsanto Corp., makers of Roundup Ready seed: Resistance may be an issue.

Actually, the issue is weed resistance in genetically modified organisms
like Roundup Ready soybeans, which now makes up 80 percent of the nation's
soybean crop.

Farmers who use Roundup Ready beans treat their fields with glyphosate, a
chemical that kills weeds by inhibiting a specific enzyme that plants need
in order to grow.

Without that enzyme, plants can't produce proteins essential to growth and
die. A majority of plants use this same enzyme, so almost all weeds succumb
to Roundup.

But not all.

What farmers say makes Roundup Ready soybeans popular is that fields are
treated just once with glyphosate -- which doesn't harm the soybeans --
eliminating the cost and time-consuming task of applying a variety of other
herbicides.

But herbicide resistance is increasing around the country and that includes
resistance to glyphosate, said Bob Hartzler, the extension weed management
specialist at Iowa State.

Hartzler suggested Monsanto take another look at its oft- stated assurance
to customers that resistance is not an issue.

"If it's a dead weed, it won't produce seed," Monsanto's David Heering told
the Farm Industry News, noting the company has worked with glyphosate for
28 years with few resistance concerns.

But Hartzler said more weeds are developing a resistance to glyphosate.

"When glyphosate resistances develops in Iowa, there will be a real cost to
those growers who must deal with glyphosate-resistant (weeds)," Hartzler said.

"Almost all weed scientists agree that the evolution of resistant biotypes
is inevitable with the current use of glyphosate. We now have ample
evidence that nature indeed can duplicate the efforts of Monsanto's
scientists and thus it seems a change in philosophy toward resistance
management is warranted," he said.

Weed scientist Christy Sprague at the University of Illinois agreed that
weed resistance is on the rise. "More weeds are developing resistance
because of the use of the same herbicides over and over again," she said.

Farmers need to scout their fields after a herbicide treatment , said
Sprague. If they don't, they're likely to see the problem of weed
resistance expand, she said.

"The big thing is that if you find that some (herbicide) is not working,
that you find out why," said Sprague.

_________________________________________________________________

Charles Benbrook Ag BioTech InfoNet <http://www.biotech-info.net>
Benbrook Consulting Services CU FQPA site <http://www.ecologic-ipm.com>
5085 Upper Pack River Road IPM site <http://www.pmac.net>
Sandpoint, Idaho 83864
Voice: (208)-263-5236
Fax: (208)-263-7342
E-mail: <benbrook@hillnet.com>

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--
L.F.London
lfl@intrex.net
http://market-farming.com
http://www.ibiblio.org/ecolandtech





  • [permaculture] [Fwd: Resistance to Glyphosate], Lawrence F. London, Jr., 07/10/2003

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