University of Missouri | November 11, 1999 | Forrest Rose
COLUMBIA, Mo. - Bt, or non-Bt? That is the question.
University of Missouri researchers sought the answer this year with greatly expanded variety tests of Bt and non-Bt corn hybrids at 15 different sites across the state. Their preliminary conclusions are that Bt hybrids yield comparably to non-Bt hybrids, but lack of pressure from the European corn borer made Bt hybrids less profitable in Missouri this year.
Last year, MU Extension agronomist Harry Minor compared Bt and non-Bt corn at three Missouri sites. This year, he planted corn research plots at locations across the state. About one-third of the entries were Bt hybrids this year, compared to "just a sprinkling" last year.
"It looks like yields from Bt and non-Bt hybrids are within about one bushel of each other, averaged over 15 sites where the pest was not artificially introduced," Minor said. "We found no yield drag or yield lag associated with the Bt hybrids."
That doesn't mean it was more profitable to plant Bt corn, as about 30 percent of corn growers in the North Central region did this year. Because the number of European corn borers was so low, "there was no return on the technology fee," Minor said. The Bt hybrids cost between $9 and $9.50 per acre more than non-Bt corn. Non-Bt hybrids were more profitable "just because of lower seed costs."
The testing sites were in or near the towns of Albany, Mo., Osborn, Mo., Chillicothe, Mo., Novelty, Mo., Richmond, Mo., Marshall, Mo., Columbia, Mo., Truxton, Mo., Annada, Mo., Laddonia, Mo., Garden City, Mo., Lamar, Mo., Oran, Mo., and Charleston, Mo.
Bt stands for Bacillus thuringiensis, a bacterium that occurs naturally in the soil and produces an endotoxin. Bt corn has been genetically altered to produce the endotoxin, which kills the corn borer after it ingests a few bites of leaf material.
"This year, we didn't have economic pressure from European corn borer at any of our 15 test sites," Minor said. "The advantage of the hybrids is protection against this pest."
Maureen O'Day, Extension associate with the MU Integrated Pest Management program. worked with Minor on the test plots. "Corn borer pressure is at a 10-year low in much of the Corn Belt, even in places where it is usually found," she said.
But in three additional tests where O'Day artificially infested the plants with corn borers, non-Bt hybrids were at a distinct disadvantage. "When they were heavily infested, it consistently cost almost 20 bushels per acre, or 12 percent in yield loss," O'Day said.
Minor says those findings demonstrate Bt hybrids pay off "in hot spots where the insect is present, or over wider areas when there are outbreaks." But some non-Bt hybrids, he noted, yield well even when infested by the corn borer.
"There is definitely some difference in tolerance to stalk tunneling."
O'Day's research shows how the corn borer impacts profits. At current prices for corn, she figures economic infestation at about one borer per plant, assuming infestation at the silking stage.
Minor said the data about the level of corn borer infestation at each of the 15 test sites is a valuable component of the research. "If we have the infestation, Bt corn can protect yields. But we don't have a good handle yet on the distribution or long-term significance of this pest in Missouri.
"I think our variety testing program is a natural for monitoring that. It provides more extensive and timely data than has been available."
