West Lafayette, Indiana
April 5, 2001
The GMO-conscious marketplace, which is causing new
identity-preservation practices at planting, will require new harvest
habits, too.
Purdue University Extension corn specialist Bob Nielsen says farmers may be
risking future sales if they don't avoid commingling genetically modified
and conventional crops when plotting, planting and harvesting.
Crops that have been genetically modified are known to farmers and others
familiar with agriculture as ''GM crops'' or ''GMO'' for ''genetically
modified organisms.'' Because of protests from some consumers about
genetically modified ingredients in their food, some food companies and corn
and soybean processors in 1999 refused to buy genetically modified grains or
paid discounted prices for them. In response, many farmers this year are
segregating their genetically modified corn and soybean crops from their
conventional crops.
The two most common genetically modified crops are Bt corn, which is
bioengineered to produce a protein that kills the European corn borer, and
soybeans that are modified to tolerate specific brands of herbicides.
Nielsen says contamination happens either when adjacent fields cross-pollinate or when seeds get mixed or commingled. ''The latter can
occur at planting as farmers switch from one hybrid to another in the
planter,'' Nielsen says. ''Commingling can also occur during or after
harvest ,with grain mixing in the combine, trucks and wagons, drying
facility, or in storage.''
''Pure'' conventional crops begin with the seed. Nielsen suggests that
farmers get whatever assurances they can from their seed dealers on the
level of purity in the seed they buy. ''If your seed company will not share
the exact purity levels, ask their representative to at least tell you what
the company's own seed purity standards are,'' he says.
The corn expert also advises farmers that volunteer, or hold-over,
genetically modified corn plants from the previous year's crop may sprout in
conventional crop fields. To avoid that problem, he advises against planting
conventional corn into last year's genetically modified field. Pollen drift
from the volunteer plants can cause contamination, too, he says.
To avoid genetically modified seed carryover in the planter, plant
conventional hybrids first and genetically modified hybrids last for
soybeans as well as corn, Nielsen says.
Planting early maturity conventional hybrids first and later-maturing
genetically modified hybrids later can reduce the risk of pollen from a
genetically modified field contaminating the silks of an adjacent
conventional field. While it's possible to minimize cross-pollination this
way, Nielsen says it's by no means foolproof. ''This strategy is not perfect
because of interactions of corn development with weather patterns and
because the range of hybrid maturities you have purchased may not be that
great,'' he says. ''Obviously, this strategy is difficult to implement if
you do not have control of the adjacent cornfields.''
To protect the genetically modified and conventional crops from contaminating each other, Nielsen offers a variety of practical management
strategies:
- Ensure that fields next to a conventional hybrid cornfield are also
conventional crops or are planted with a different crop such as soybeans.
''If the adjacent land area is wooded or grassy pastures, all the better,''
he says.
- If a farmer doesn't control adjacent fields or cannot negotiate with the
farmers who do, he or she should plan to harvest a number of rows around the
edges of the conventional field and segregate the grain to minimize the
harvest-time commingling of that potentially ''contaminated'' grain with the
grain from the rest of the field.
- Seed company agronomists indicate that genetically modified corn pollen
should not contaminate more than the outside 20 rows with levels that exceed
1 percent if nothing separates the two fields. If the conventional field is
bordered by a buffer zone of conventional crop about 660 feet wide, the
grain from the outside 20 rows should not require segregation.
Ambitious farmers can monitor when pollination occurs in each of their
fields this season in order to can rank the conventional fields based on
their susceptibility to drifting genetically modified pollen from adjacent
fields. ''If you also monitor wind direction during the pollination period,
you can further refine your assessments by predicting which adjacent field
is most likely to cross over the line in terms of pollen drift,'' Nielsen
says.
When harvest time arrives, Nielsen recommends that all conventional crops
be harvested first to minimize the risk of commingling grain in the combine,
trucks and wagons.
The same harvest advice applies for conventional and genetically modified
soybeans, he says, even though pollination contamination is not an issue,
because soybeans are self-pollinated.
Before the harvest, farmers should be sure that their drying and storage
facilities are absolutely clean of any genetically modified grain possibly
left over from the 1999 crop. ''Consider moving or selling your genetically
modified grain directly off the farm to avoid any possibility of grain
commingling in your drying and storage facilities,'' Nielsen says.
Finally, Nielsen cautions farmers to be aware that grain buyers who limit or
segregate their genetically modified corn grain purchases this fall will
have quick test kits available for the detection of the Bt Cry1A(b) gene in
the two major Bt hybrids, Monsanto Mon810 and Novartis Bt11.
Writer: Amy H. Raley, (765) 494-6682; ahr@aes.purdue.edu
Source: Bob Neilsen, (765) 494-4802, rnielsen@purdue.edu
Related Web sites:
KingCorn, the Corn Growers' Guidebook: http://www.agry.purdue.edu/ext/corn/
Bob Nielsen's professional Web page: http://www.agry.purdue.edu/ext/corn/rln-bio.htm
Jeanne Norberg, director
Purdue University News Service
1132 Engineering Admin. Bldg.
West Lafayette, IN 47907-1132
Phone: 765-494-2096
E-mail: jnorberg@purdue.edu
Purdue University news release
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