The root of the issue: Corn yields surprises
Anne Cook The News-Gazette, July 13 2007 [shortened]

URBANA ­ The stacked corn traits farmers pay big bucks for aren't keeping rootworms from munching on their favorite food.
[University of Illinois entomologists Mike Gray and Kevin Steffey] and their student assistants this week started digging up corn plants in UI fields to look at their root system health, an annual ritual for these scientists who study pests that prey on the state's largest crop.
Gray said they've discovered some surprising differences in their 25-acre test plots near South Race Street. He said project overseer Ron Estes called their attention to the surprising difference in height between one transgenic variety that contains proteins engineered to kill both corn borers and rootworms, and its close relative without the traits.
The second surprise is that rootworms did significant early damage to transgenic varieties.
Gray said they started digging up roots to evaluate damage in July as well as August for a very specific reason ­ a severe storm that swept through in July a few years ago and flattened a lot of corn fields, a sure sign rootworms have been at work in the ground.
"There was more damage than expected," he said. "That was an opportunity presented to us. We decided to do a second set of evaluations to compare roots treated with soil insecticide to roots of transgenic varieties with stacked traits for rootworm and corn borer protection."
Technology incorporated into plants to make them lethal to insects relies on Bacillus thuringiensis, a bacterium that expresses a protein that breaks down the digestive system of insects when they ingest it.
But Steffey said the technology introduced in 1996 that works so well for corn borers, killing about 99 percent of the beetles that eat it, doesn't work as well on rootworms, technology introduced in 2003.
"You don't get the expression in the roots that you get in the leaves," he said, adding that many companies don't emphasize that fact when they're selling their stacked hybrids to farmers.

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the_root_of_the_issue_corn_yields