That's one of the topics covered in a new SDSU publication about biotechnology issues. The publication is available online at http://agbiopubs.sdstate.edu/articles/ABS3-02.pdf .
Bt corn is a transgenic crop that has been genetically altered by having genetic material from a soil bacterium called Bacillus thuringiensis added to it in its early stages of development. The added genetic material enables the corn to express a protein lethal to specific insects such as European corn borers. Growers pay more to purchase Bt corn hybrids.
SDSU Extension Entomologist Mike Catangui says there's a definite yield advantage to growing Bt corn in outbreak years such as 1996 and 1997. During those years, SDSU research showed yields of 13-14 bu more per acre on average from Bt corn compared to nontreated, conventional corn hybrids, he says.
However, there was no yield advantage to growing Bt corn for the four years following that, Catangui says. 2002 was another year in which there was a distinct advantage.
"2002 turned out to be a good year to grow Bt corn since the mild winter allowed many corn borer larvae to survive. On top of that, the weather in June and July was favorable for egg-laying by the corn borer moths," Catangui says.
Catangui says SDSU research found a 32-bu/acre advantage at Beresford for Bt corn in 2002 over nontreated conventional corn. At South Shore there was an advantage of up to 13 bu/acre for Bt corn compared to nontreated conventional hybrids.
Catangui notes that conventional corn, when treated with insecticide, performed similarly to Bt hybrids during corn borer outbreaks.
Catangui's study was supported initially by the South Dakota Corn Utilization Council.
SDSU tracks corn borer populations with the help of volunteers at locations around South Dakota. For more information, visit Catangui's Web site, http://plantsci.sdstate.edu/ent/ .
Catangui adds that a new Bt product will be commercially available to growers this year. It makes a protein lethal to corn rootworms.