Farm Journal: Pollen In The Air
Greg D. Horstmeier
From the pages of the May/June 2001 edition of Farm Journal magazine.
Imagine it's late July in the U.S. Corn Belt. Somewhere, a 100-acre
field of corn is pollinating, casting to the winds some 13 trillion
pollen grains. To that vision add that farmers will plant some 18.4
million acres of genetically modified (GM) hybrids this year. Add in the
tens of thousands of acres of such things as GM inbreds, parent lines
and experimental plots. Welcome to the land of milk and "adventitious
presence." That's the latest buzzword for what happens when pollen ends
up where it's not supposed to be. It was called outcrossing by seed
companies back when their biggest concern was farmer complaints that a
field was not consistent in plant height or color.
In the seed. In these post-StarLink days, unintended pollen shed can
mean the bag of seed corn you planted has more traits than you may have
paid for or wanted. There is growing concern that farmers may plant seed
that already has genetic traits that may hurt their ability to sell the
harvest.
At a recent seed industry workshop on adventitious presence, Tom
O'Connor, head of technical services for the National Grain and Feed
Association, called for labeling seed corn bags with the amount of GM or
other adventitious contamination present. "If you're buying an
unapproved [trait], you should know that if you plan to market corn in
an area where that event can't be sold," O'Connor says.
Seed companies fear labeling bags could be misleading and, until
tolerances and testing standards are set, meaningless.
"The seed industry has always been concerned with outcrossing," says
Tim
Gutormson, president of Mid-West Seed Services, Inc. His company tests
seeds for companies and foundation seed developers, looking for
everything from simple germination information to genetically modified
content.
In the past two years, Gutormson's company has seen increased demand for
genetic purity testing. "Now that we've gone through the Cry9c
[StarLink] situation, it's definitely raised the bar in the amount of
genetic purity testing seed companies are doing," he says.
That should be good for farmers, he says. For example, federal law
stipulates that a bag of seed corn be 95% hybrid seed. While most
companies strive for only 1% or 2% impurity, or outcrossing of a hybrid,
the StarLink situation has everyone learning just how good a job they
were doing, and what areas to improve to meet zero tolerances.
"Historically, there has been a fair amount of work on pollination and
pollen travel," says Mike Lauer, a research coordinator at Pioneer
Hi-Bred International. "But there are a lot of things about it that we
may never fully understand."
Tracking the wind. Since 1998, Lauer and others in the seed industry
have sampled 155 seed production fields for the amount of foreign pollen
that has entered the field. Only fields with a high likelihood of
outcrossing were tested, Lauer reports.
Most seed production fields have 8 to 16 all-male border rows--an
attempt to minimize outcrossing from a nearby field by overloading field
edges with "correct" pollen.
For the adventitious presence study, researchers started at the
innermost border row and sampled grain produced at intervals of 6.8',
31', 68', 118' and 660' into the field. The percentage of outcrossed
seed was averaged over all fields.
Wind conditions year to year were critical, Lauer reports. "How one
year's wind patterns varied from another's, and the influence on pollen
movement, is tremendous."
In 1998, average adventitious contamination was 0.9%. In 1999,
contamination was 1.7%. Data from 2000 hasn't been fully examined.
"Increasing the distance [from other corn] tends to decrease
outcrossing," Lauer says. As predicted, samples from far inside the
field had lower amounts of contamination than did rows near the outside.
But the drop in contamination across any field was not linear, with hot
and cool spots at various distances. Those peaks and valleys of
contamination varied greatly from field to field.
"One thing we don't fully understand is how much influence wind
turbulence above the field has on mixing pollen from that field and
nearby fields," Lauer says. "You may think a wind break would be a
good
thing, slowing wind and decreasing how far pollen goes. That may not be
true."
Pollen worries don't stop with crops that cross-pollinate. "The cotton
seed market in Greece, a premium-priced market, isn't driven by
science," says Chip Sundstrom, executive director of Parsons Seed
Certification Center at the University of California, Davis.
To keep the high-value Greek market, California seed producers must
guarantee zero GM content.
Cotton, like soybeans, is a self-pollinating crop. Yet Roundup Ready and
BXN cotton are popular in the same areas where premium cotton seed is
produced. "We've learned that cotton pollen is the top source of honey
in California," Sundstrom says.
Role of bees. In 2000, Sundstrom and colleagues from Parsons sampled
seed fields at distances from 80' to nearly a mile from
adventitious-pollen producing fields.
"We found outcrossing from 0.2% up to 1%," Sundstrom says. "We
found
cases where outcrossing was 0.1% up to a mile from other cotton. And
these are fields that get a lot of insecticides. I was out in those
fields and there were basically no bees, no insects of any kind."
The center will conduct more rounds of pollen tests this year to get a
better feel for common flow levels. Sundstrom also plans to test nearby
bee hives to see how much GM pollen bees may be carrying and if they are
actually the culprits.
What seed production changes seed companies may have to make also
depends on what tolerance levels are allowed.
"StarLink taught us that zero tolerance won't work," says Gutormson.
"Before companies can really say they're doing an adequate job of
isolation, we have to know what tolerances they have to meet."
Seed companies prefer more standardized tolerances for new traits. "It's
going to be very difficult to establish a threshold for all unapproved
varieties," says Michael Schechtman, USDA's biotechnology coordinator.
"You can't pass judgment on the safety of [modified] organisms that have
not even been evaluated yet."
Sidebar: Don't Volunteer Trouble
Never has so much attention been paid to volunteer corn. Those ugly
reminders of what slipped through the combine's grasp have special
relevance this season. Some volunteer plants may contain the outlawed
StarLink trait.
Greatest concern is around fields that in 2000 grew hybrids containing
StarLink. Pollen from volunteers there could cross-pollinate with
neighboring corn, continuing the chance of the Cry9c gene showing up in
human foods. Officials with Aventis CropScience, the company that
created StarLink, say representatives from Aventis and from seed
companies that sold StarLink hybrids are contacting producers who grew
the hybrids in 2000 to make sure they control volunteer plants.
Fields that adjoined StarLink hybrids are also suspect. If plants in
those fields received StarLink pollen, 2001-season volunteers may also
carry the trait.
Post-emergence grass herbicides for soybeans--Fusilade, Select, Poast or
Roundup in Roundup Ready soybeans-will control volunteer corn. In
continuous corn, the treatment is more complicated. Planting Clearfield
hybrids and using imidazolinone-based herbicides may not work if the
2000 hybrid had stacked Clearfield-StarLink traits. Same goes for using
Liberty Link hybrids--all StarLink hybrids contained the Liberty Link
trait. Volunteers will tolerate Liberty herbicide.
Roundup or other glyphosate herbicides will control volunteers in
Roundup Ready corn. However, the National Corn Growers Association and
others warn against planting Roundup Ready corn in areas where grain may
be exported. Roundup Ready corn has not been cleared for export to
Europe.
Concern about Roundup Ready pollen flowing into conventional cornfields
is also stirring controversy. Researchers at the University of Missouri
decided not to allow Roundup Ready corn in statewide corn trials,
fearing the pollen could blow into other fields near test plots.
Similar concerns were cited by agronomists with Farmers Independent
Research of Seed Technologies. That group also will not include Roundup
Ready hybrids in trials this year.
Aventis officials are still lobbying for a temporary tolerance for the
Cry9c gene, which produces the StarLink trait. With the current zero
tolerance for Cry9c, Aventis officials contend, the issue will remain
for four or more years.