GMO Corn Contamination 101

Updated: Sep 16, 2020

On March 28, 2016 /   Corn, GE Avoidance, GE Contamination, GMO Contamination Mitigation, GMO Testing, GMOs, Organic, Organic Farming, Organic Seed Integrity, Organic Seed Production, OSGATA, Roundup Ready Corn, Seed News, Seeds

Corn (Zea mays)

Ninety percent of all corn grown in the U.S. is genetically engineered. This fact, coupled with corn’s outcrossing nature, equals significant risk of GE contamination for organic corn growers.

Of course, the individual degree of risk differs based on various factors: the region in which the organic corn is being grown and its proximity to GE corn fields are key considerations.

Planting, harvest, and storage, are all potential points of genetic contamination, and organic corn seed faces high risk of GE contamination from cross-pollination during the growing season.

Conventional seed industry wisdom has maintained that 660 ft. is a sufficient isolation distance for maintaining seed purity in corn. Is this enough for avoiding GE contamination? An international survey of literature pertaining to isolation found recommendations ranging from 82 ft. to 6 miles. The organic seed industry in the U.S. has yet to establish its own universal standard, but many experts advocate for a minimum isolation distance of 2 miles.

Research shows isolating by both time and space to be the most effective strategy. Corn pollen has a short viability window, 2 to 24 hours on average, and a planting difference of at least eight days between corn crops has been shown to reduce cross-pollination.

If you’re planting corn this season and want to decrease your crop’s risk of GE contamination, read the full chapter on corn in Protecting Organic Seed Integrity: The Organic Farmer’s Handbook to GE Avoidance and Testing. The handbook is available as a free download.

Here is a brief overview of best management strategies regarding corn:

Keep Your Corn Seed GE-Free…

  • Identify potential points of GE contamination.

  • Purchase seed that has been tested for GE content.

  • Plant seed a minimum of 2 miles from GE corn plantings. Greater isolation distance is recommended. If possible, plan isolations for time to create dissimilar pollination windows from area GE corn.

  • Stagger plantings by 1 week minimum; 3-4 weeks is recommended.

  • Treat rows on the field perimeter as a different seed lot and harvest them separately. Clean up residual whole cobs to avoid volunteer plants next season. Avoid mixing during harvest, cleaning, storage, transport, and sales.

  • Use dedicated equipment and facilities if possible. Otherwise, clean between use.

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