USDA’s Economic Research Service (ERS) recently updated the data product Adoption of Genetically Engineered Crops in the U.S., and the new data provides important insights on the prevalence of so-called “stacked” varieties.

A “stacked” variety of GMO corn or cotton is engineered to express two or more distinct traits — typically herbicide tolerance (e.g., Roundup Ready) and Bt transgenic (i.e., insect protected).

The new release includes this USDA chart  illustrating the change over the last decade in the percentage of corn and cotton acreage planted to corn and soybean seed with stacked, GMO traits.  These types of GE seeds have been altered to be both

As evident in the chart, in 2008 45% of U.S. cotton and 40% of corn acreage were planted to stacked-trait varieties.  A decade later, these numbers doubled – with 82% of cotton acres and 80% of corn planted to GE corn expressing more than one trait.

We have discussed the stacking of GE traits before on Hygeia.  In many cases, traits that are individually considered “safe” are stacked with others without any research or assessment of the possible cumulative ecological or human health impacts of each new combination.

Number of Stacked Traits Undercounted

These data underestimate the number of stacked traits planted.  As Bt resistance-management provisions were relaxed, and insects in some regions became resistant to different Bt traits, companies added additional Bt traits in the hope of sustaining effective control.  Today on average, each acre of stacked-trait corn is expressing about 3 Bt traits, as well as one or more herbicide-tolerance trait.

In fact, Monsanto-Dow AgroScience’s SmartStax corn expresses 6 separate Bt traits, and two herbicide-tolerance traits, making it one of the most expensive corn seed technologies on the market. (The premium price charged for GMO corn and cotton is driven by the number of traits expressed).

More stacked traits in a variety of corn or cotton translate into higher seed costs for farmers, which is one reason the USDA is tracking trends in the number of stacked traits.

Source:

USDA, “Most U.S. corn and cotton acreage in 2018 used genetically engineered seeds with stacked traits,” July 20, 2018.