ALABAMA A&M and AUBURN UNIVERSITIES

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Bt CORN OFFERS ADVANTAGES

Auburn, March 5---Under certain conditions, genetically engineered Bt corn seems to be a good bet for Alabama producers, especially in southern Alabama.

Bt corn hybrids are special varieties that produce the same toxin as the bacterium Bacillus thuringensis that protects them against major caterpillar pests, such as the European corn borer, fall armyworm and corn earworm.

"Based on research in the Midwest, there's no question Bt corn hybrids, compared with conventional varieties, sustain far less damage from European corn borer, fall armyworm and corn earworm," says Dr. Kathy Flanders, an Alabama Extension entomologist.

But Flanders and other experts, including Auburn Extension agronomist Paul Mask, wanted to know how well these genetically modified varieties performed under Alabama conditions.

In 1997, they began conducting tests in several locations: North, Central and South Alabama. Test results from that year showed most Bt-corn hybrids performed as well as commercial standards in 1997. On the other hand, no clear yield advantage was seen from the Bt technology.

"This reinforces what already has been seen in theMidwest - namely insect pressure needs to be there in order for the added price of Bt corn to be profitable," Flanders says.

"In fact, most insect experts in the Midwest view Bt corn as an insurance policy, which is most likely to pay off in areas where European corn-borer populations are high.

Results from Alabama test plots in 1998 confirmed that premise. Following an unusually bad outbreak of fall armyworms last year, results from Bt-corn tests in southern Alabama showed the varieties performed much better than conventional corn varieties - more so than in tests in Central Alabama, where only light armyworm outbreaks occurred.

"One problem with conventional (non-Bt) corn varieties is that they have to be planted so early in the year," Flanders says.

"While early planting protects conventional corn against drought and insect infestations, it often precludes planting a winter cover crop. But the insect-resistant properties of Bt corn may allow it to be planted after these recommended dates, allowing producers more flexibility."

Tests showed on the first planting date, one Bt hybrid at Headland in Southeast Alabama and two Bt hybrids at Fairhope in Southwest Alabama produced more than 10 percentgreater yields than the best non-Bt standards.

On the second planting, three of four Bt hybrids in Headland and Fairhope outperformed the best non-Bt standard.

By the third planting, all of the Bt hybrids produced more than 10 percent better yields than their conventional counterparts.

"In fact, at Headland and Fairhope (in South Alabama) non-Bt hybrids were so damaged by fall armyworms that they no longer had a harvestable yield," Flanders says. "Even the Bt hybrids weren't immune to fall armyworm damage and sustained heavy defoliation."

Still, compared with conventional hybrids, performance tests show Bt-corn to be highly profitable technology during periods of high-insect infestation, Flanders says. As plant breeders are able to develop more Southern-adapted Bt corn, the potential for Bt corn will be even greater, she says.

Even more Bt-corn hybrids will be planted this year. Seed costs for Bt-corn hybrids are running between $30 and $35 a bag - still more than conventional varieties, running an additional $10 or $12 an acre.

Most of the Bt-corn hybrids express the toxin throughout the plant, but these whole-plant-expression hybrids are subject to acreage restrictions. No more than 50 percent of the Alabama corn acreage can be planted tothose hybrids.