Modified corn spreads the love around

U. MINNESOTA (US) — Transgenic corn’s resistance to pests benefits even corn that has not been genetically modified, according to new research.

A study published in the Oct. 8 edition of the journal Science, finds that widespread planting of genetically modified Bt corn throughout the Upper Midwest has suppressed populations of the European corn borer, historically one of corn’s primary pests.

The area wide suppression has dramatically reduced the estimated $1 billion in annual losses caused by the European corn borer, even on non-genetically modified corn.

Bt corn, introduced in 1996, is so named because it has been bred to produce a toxin from the soil bacterium Bacillus thuringiensis (Bt) that kills insect pests.

Corn borer moths cannot distinguish between Bt and non-Bt corn, so females lay eggs in both kinds of fields, says William Hutchison, professor of entomology at the University of Minnesota.

Once eggs hatch in Bt corn, young borer larvae feed and die within 24 to 48 hours. Because it is effective at controlling corn borers and other pests, Bt corn has been adopted on about 63 percent of all U.S. corn acres.

As a result, corn borer numbers have also declined in neighboring non-Bt fields by 28 percent to 73 percent in Minnesota, Illinois and Wisconsin, depending on historical pest abundance and level of Bt-corn adoption.

The study, the first to show a direct association between Bt corn use and an area wide reduction in corn borer abundance, documents similar declines of the pest in Iowa and Nebraska.

Economic benefits of this area wide pest suppression have totaled $6.9 billion over the past 14 years for the 5-state region. Surprisingly, non-Bt corn acres accounted for $4.3 billion (62 percent of this total benefit.)

The primary benefit of Bt corn is reduced yield losses, and Bt acres received this benefit after the growers paid Bt corn technology fees. But as a result of area wide pest suppression, non-Bt acres also experienced yield savings without the cost of Bt technology fees, and thus received more than half of the benefits from growing Bt corn in the region.

“Previous cost-benefit analyses focused directly on transgenic crop acres.  This study is the first to include the value of area wide pest suppression and the subsequent benefits to growers of non-transgenic crops,” says Paul Mitchell, an agricultural economist at the University of Wisconsin-Madison, and a co-author of the study.

“In this case, the value of the indirect yield benefits for non-Bt corn acres exceeded the net value of direct benefits to the Bt corn acres.”

The analysis does not consider benefits for other important Midwestern crops affected by European corn borer, such as sweet corn, potatoes, and green beans.

Hutchison observes however, “that additional environmental benefits from corn borer suppression are likely occurring, such as less insecticide use, but these benefits have yet to be documented.”

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