A US pharmaceutical
company is set to introduce a controversial new genetically modified
corn to help farmers fight resistant weeds.
Dow Agrosciences says its new GM product will use a chemical
that was once a component of the Vietnam war defoliant, Agent Orange.
It is needed they say because so called "superweeds" are now affecting up to 15 million acres of American crops.
Dow argues the new approach is safe and sustainable.
For a farmer like Jeremy Leech who grows corn and soybeans
near Humboldt, Nebraska, resistant weeds are a constant threat to his
farm and his family.
Last year he spent around $7,500 on chemical sprays to combat the threat to his crops.
The herbicide failed to kill the giant ragweed that had grown
on his land, strangling his soybeans and his income. Worse, the pungent
pollen from the towering pests exacerbated his eight year-old
daughter's asthma.
"When that stuff is pollinating it makes it hard for her to
breathe outside and when you live on a farm you know the kids play
outside all the time and they love it and when that pollen gets really
bad she gets choked up," he says.
Farming revolution
Thousands of farmers across the US now face similar problems
with weeds that can withstand powerful herbicides. Scientists say it is
because of the success of GM crops that were introduced in the mid
1990s.
Monsanto became a world leader in the field thanks to the
introduction of Roundup-ready corn and soybeans. These crops were
engineered to be able to survive spraying with glyphosate, a chemical
marketed as Roundup.
Jeremy Leech has battled resistant weeds on his Nebraska farm.
Farmers just needed to use this one spray on their fields and
it killed all the weeds but left the crops intact. Growers rapidly
adopted the new technology as it cut their costs substantially.
"Roundup was the one that was supposed to do wonders," says Jeremy Leech's father, Van.
"And it did for the first few years; anybody could raise
clean beans. Obviously over the last few years, bean fields are
beginning to look more and more like this," he says, pointing to a field
where weeds tower over shrunken crops.
To see how bad the weed problem can get, I travelled to an
experimental plot near David City run by the University of Nebraska with
Prof Stevan Knezevic.
We stand in a cornfield surrounded by towering green plants.
But there is not an ear of corn in sight. The stalks that surround us
are Giant Ragweed, one of the "dirty dozen" weeds that have acquired
resistance to Roundup.
Harvesting corn on the Leech farm in Nebraska
So powerful have these monster weeds become become that even
spraying them with 24 times the recommended dose of Roundup fails to
kill them.
These plants suck the light and the life from the crops. Just
one resistant weed every 10 square metres can reduce the yields from
productive plants by 50%.
"Over the past 15 years I said that if we continued using
roundup, roundup roundup, we're going to have a problem - now we have
that problem," says Prof Knezevic.
"The reason why we are here is that we all mismanaged this technology."
Back to the future
Recognising the scale of the problem, the biotechnology
industry believes that newer more effective forms of GM are the
solution. Dow Agrosciences is now seeking US government approval for the
Enlist weed control system.
Instead of the crop being resistant to one chemical, it is
engineered to resist two. Dow says this is a more effective solution
because it allows farmers to mix and match their sprays more
effectively, making for a far more sustainable system.
What is causing controversy though is the new trait which makes
the crops resistant to a chemical called 2,4-D. Developed by a British
team during the war, this powerful weed killer was a component part of
Agent Orange, the defoliant used extensively by the US Army during the
Vietnam war.
2,4-D is currently utilised as a herbicide in agriculture,
though it is used sparingly because it is highly toxic. The change here
would expand options for farmers to use 2,4-D.
Although it was is one of two chemical ingredients in Agent
Orange, the chemical was not implicated in causing the devastating
health impacts suffered by many people exposed to the defoliant.
Continue reading the main story
Alternative approaches
- Bright orange flames shoot from the back of a propane powered
weed burner as it trundles slowly across a field. This is a modern
demonstration at the University of Nebraska of an old technique
- According to the university's Prof Stevan Knezevic, around
70,000 farming families in the US used flaming as their main defence
against weeds in the 1950s
- The device is still popular with organic farmers who have few
chemical sprays that they can utilise. But according to Dr Knezevic the
rise of weed resistance is increasing interest from conventional farmers
as well
- This prototype can concentrate flames at temperatures up to 1,100C, sufficient to kill most weeds
- "Any weeds that come from a seed, you can smoke it... Literally," says Prof Knezevic
Prof Dallas Peterson of Kansas
State University who has co-operated with Dow in the past says this
makes the chemical very suitable for working in combination with others.
"It is an old herbicide, one of the oldest synthetic
herbicides around; we've used it for over 50 years in many different
situations and to quite a large degree, and we haven't had many cases of
resistance develop yet," he explains.
The US Environmental Protection Agency says that 2,4-D is
safe for use in farming. The Department of Agriculture is expected to shortly grant final approval for planting next spring.
But weed scientists are concerned that if farmers are not
educated to use the new GM product properly, resistance issues will soon
re-appear.
"It will certainly help with weed resistance; it's a new mode of action," says Prof Dallas Peterson.
"But it's not a silver bullet - and if we utilise the
technology too extensively and rely on it too exclusively, eventually we
will develop resistance."
Back on the farm in southeastern Nebraska, Jeremy Leech is
carefully cleaning his combine harvester to make sure he does not
transport resistant seeds from one field to the next. He is also
sceptical that a new GM alone is the answer.
"To me, it's a short-term fix. I think 2,4-D will work fine,
but what I'm afraid is what's going to happen 4-5 years down the road if
we keep using it. I think we 'll have the same problems we have now
with Roundup."
These giant ragweeds have grown tall despite the application of herbicide
What is emerging from Dow and other biotech companies in this
field is the growing acceptance that greater education of farmers and a
more comprehensive approach to weed management are crucial to the
success of their products.
"When we grow Roundup-ready corn and rotate it with
Roundup-ready soybeans the biodiversity is out of the window," says Prof
Knezevic.
"It's just two crops, same chemical. We need more
biodiversity if the biotech bandwagon is to succeed, like the organic
farmers who rotate their crops more."
Ironically, the future of GM may well depend on
re-incorporating some of the older skills that the technology once
threatened to replace.
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