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Approved-By:  Laurel Hopwood <[log in to unmask]>
Message-ID:  <f06240838c8bd6699805b@[66.61.123.97]>
Date:         Mon, 20 Sep 2010 15:31:41 -0400
Reply-To:     Biotech Forum <[log in to unmask]>
Sender:       Biotech Forum <[log in to unmask]>
From:         Laurel Hopwood <[log in to unmask]>
Subject: Growing Roundup-Resistant Weed Problem Must be Deal with, expert says
To:           [log in to unmask]
Precedence: list


http://live.psu.edu/story/48259
Growing Roundup-Resistant Weed Problem Must be Deal with, expert says
EDITED

When Penn State weed scientist David Mortensen told members of the 
U.S. House Oversight Committee this summer that the government should 
restrict the use of herbicide-tolerant crops and impose a tax on 
biotech seeds to fund research and educational programs for farmers, 
it caused quite a stir.

Mortensen, he professor of weed ecology in the College of 
Agricultural Sciences, has spent his career researching weeds that 
affect agricultural production, sustainable ways to control them, and 
the relationships between crops, native and invasive weeds, and 
pollinators. He has published several peer-reviewed papers on the 
subject in recent years.

The resistant weeds cannot be killed by the sole use of glyphosate, 
the active ingredient in Roundup herbicide. The weeds now infest 
about 11 million acres -- a fivefold increase in three years, 
Mortensen reported.

This list includes many of the most problematic weed species, such as 
common ragweed, horseweed, johnsongrass and several of the most 
common pigweeds -- many of which are geographically widespread.

Mortensen expressed concern about herbicide- and 
germplasm-development companies responding to the 
glyphosate-resistance problem by developing a new generation of 
genetically engineered crops in which glyphosate-resistant cultivars 
are being engineered to have additional resistance traits introduced 
into the crop's genome. "These additional gene inserts will confer 
resistance to other herbicide active ingredients, including 2,4-D and 
dicamba," he said. "For a variety of reasons, it is quite likely that 
such crops will be widely adopted. Disturbingly, that would result in 
a significant increase of older, higher use-rate herbicides in 
soybean and cotton production.
"If they are adopted in the way I expect they will be, herbicide use 
in soybean production would increase by an average of 70 percent in a 
relatively short time after the release of these new genetically 
engineered, herbicide-resistant cultivars."

Vapor drift of more toxic herbicides has been implicated in many 
incidents of crop injury and may have additional impacts on natural 
vegetation interspersed in agricultural landscapes, Mortensen told 
lawmakers. Scientists have documented that nontarget terrestrial 
plant injury was 75 to 400 times higher for dicamba and 2,4-D, 
respectively, than for glyphosate.

Together the herbicide and seed-breeding industries are moving to 
address the problem of resistance with crops that have been 
engineered to be resistant to multiple herbicide active ingredients, 
according to Mortensen. If these new crop introductions occur as 
reported, we should expect to see herbicide use continue to increase 
and a significant proportion of those added herbicides will be older, 
less environmentally benign compounds, he predicted.

"Biotech companies are trying to deal with the problem by engineering 
new crop varieties that will be immune to more than one herbicide, 
but even those products will eventually run into resistance problems 
if farmers aren't careful," he said.

"Transgene seed and associated herbicides should be taxed and 
proceeds used to fund and implement research and education aimed at 
advancing ecologically based integrated weed management," he 
concluded.

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