As the growing season unfolds over North America, farmers have an opportunity to try some would-be 21st-century crops.
Varieties of corn and cotton genetically engineered to make their own pesticide are making a repeat appearance.
Farmers who use them will be taking part in a second "reality" test of these biotech wonders. Companies that developed them - such as St. Louis-based Monsanto, Mycogen in San Diego, and Ciba Biotechnology in Research Triangle Park in North Carolina (a subsidiary of Switzerland's Ciba-Geigy) - expect they will greatly reduce the need for chemical sprays to control certain major insect pests.
The companies hope this will reduce environmental pollution and cut farmers' costs even though the gene-tailored seed is more expensive than the regular varieties.
Those expectations have yet to be verified. Last year's plantings yielded mixed results.
Corn engineered to protect itself from the European corn borer performed well. But the jury is out as to whether this made any difference in the payoff to the farmer. The engineered corn accounted for less than 1 percent of total corn planting and less than 2 percent of the harvest. More seed should be available this year since Monsanto, which didn't offer it in 1996, is in the market.
Cotton designed to fend off attacks of three insects repelled two: the tobacco budworm and pink budworm. But farmers had to use some spray on 40 percent of plantings across the Southern US to control the bollworm when infestations reached unusually high levels.
Nevertheless, Monsanto spokesman Gary Barton says a company survey found that 4 out of 5 of the 5,600 growers who used Monsanto's Bollgard cotton (the crop involved) were "satisfied or very satisfied." Only 2 percent said they wouldn't buy Bollgard this year. Bollgard covered 1.8 to 2 million of the 14.5 million acres of cotton in the US last year. There were also 75,000 acres of it in Australia and 2,200 acres in Mexico. Mr. Barton expects 3 million acres of Bollgard to be planted this year.
We've learned that "things are more complicated than we expected" when genetically engineered plants are in a farmer's field, observes entomologist Fred Gould at North Carolina State University in Raleigh. "We're still on a learning curve" when it comes to transgenic farming, he says.
How it works
What biotechnologists have done is transfer certain genes from the soil bacterium Bacillus thuringiensis (Bt) to various crop plants. These genes code for proteins that are harmless to humans and most other animals but deadly to specific insects. Such proteins are already widely used as so-called Bt insecticide sprays.
Sprays are shortlived, however, and must be reapplied. Plants that have Bt genes make the pesticide proteins continuously in many parts of their structure. This gives long-lasting protection. And, in the case of corn borers that get inside plants, it is better protection than external sprays can provide.
Technologists are working on several Bt crops, including potatoes and tomatoes. But the payoff lies with "big ticket" crops such as corn and cotton.
Agricultural economist Marshall Martin and entomologist Larry Bledsoe at Purdue University in West Lafayette, Ind., note that realizing the payoff requires honing the Bt crop tool to fit an individual farmer's need. Differing soil conditions, climate conditions, and crop mixes require differing characteristics in the corn or cotton varieties planted.
Bt insect resistance is just one factor. Professor Martin notes that corn farmers, for example, are less concerned about borers than they are about rootworm. Dr. Bledsoe adds that farmers have been growing corn varieties that can produce good yields even when under borer attack.
The more expensive Bt corn won't have any advantage if it fends off borers but yields less than those varieties. Dr. Gould makes a similar point about Bt cotton. So many factors are at work on a farm it will take more practical experience to learn when, where, and how to make best use of Bt crops.
Monsanto's Gary Barton agrees. He also points out that the lack of a wide range of Bt varieties that have a variety of desirable characteristics beyond making pesticide has limited their use. He expects that limitation to ease as more varieties are developed.
Overhanging all these considerations is the question of whether, when, or how insects might develop resistance to the Bt crops themselves. Plantings are carried out under guidelines designed to minimize resistance development. Yet as Bledsoe notes, there are "an awful lot of questions about resistance" at this stage.
Meanwhile, all experts interviewed emphasize that the watchword for introducing Bt corn and cotton is "caution." They point out that there's no such thing as a one-size-fits-all solution in dealing with crop pests.
Says entomologist Gould, "The idea that you can have complete control of insect resistance in commercial settings - I don't think anyone has that."