1. Recognize potential issues and major topics in the case. What is this case about? Underline terms or phrases that seem to be important to understanding this case. Then list 3 or 4 biology related topics or issues in the case.

2. What specific questions do you have about these topics? By yourself, or better yet, in a group, make a list of what you already know about this case in the “What Do I Know?” column. List questions you would like to learn more about in the “What Do I Need to Know?” column.

3. Put a check mark by 1–3 questions or issues from the “What Do I Need to Know?” list that you think are most important to explore.

4. What kinds of references or resources would help you answer or explore these questions? Identify two different resources and explain what information each resource is likely to give that will help you answer the question(s). Choose specific resources.

As the local farmers waited for the DeWitt County Extension monthly meeting to begin, they began discussing the surprising news that corn containing a new Bt gene not approved for human consumption had been found in a grain elevator in neighboring Macon County.

“I just don’t understand it,” Emmet said. “Now those growers have to sell all the corn in that elevator as animal feed. How did this happen if no one in that county planted the new Bt seed?” “Well, they may not plant it in Macon County, but we certainly grow all types of Bt corn here,” John replied.

“I always get some volunteer corn from the year before,” Sam offered. “Do you think someone planted new acreage and didn’t check for volunteers from the prior owner’s crop?”

“I’m pretty sure the new Bt seed only became available this year,” Emmet responded. “Do you think the seed company might have packaged some of the new Bt seed with the wrong label?” “I know that new Bt corn hybrid was planted in at least two fields just north and west of the Macon County border,” John declared. “So, what about pollen drift? Remember how windy it was this summer? Why, some of my late-planting corn seedlings in the flood plain were knocked down just about the same time the higher-ground corn was tasseling.”

The conversation was interrupted as Roger, the county extension agent, signaled for the meeting to start. “Let’s get down to today’s business—new alternatives for planting European corn borer refuges—always a popular topic,” he announced with a tentative smile.

European corn borers (ECB), which cause many kinds of damage in corn, are mentioned in the case. The problem of ECB damage allows a meaningful introduction of plant growth and morphology covered in this unit. The creation of transgenic crops is also covered in this unit. The information about refuges is an opportunity to study genetic change. While not included in the unit, the problem of the spread of resistance genes in ECB populations lends itself to analysis using the Hardy-Weinberg equation.

European corn borers were introduced accidentally in the United States in 1909. Early control methods centered on burning infected fields and quarantining crops. The discovery that strains of Bacillus thuringiensis (Bt) produce a toxin effective against the European corn borer (and other lepidopterans) was made in the 1920s. Sprays of whole, dried cultures of B. thuringiensis have been used widely to control ECB since the 1930s in conventionally and organically grown corn. Because Bt sprays are effective only for a matter of days, use of sprays necessitates repeated scouting in the fields to detect ECB larvae. Most areas of the United States average two to five generations of ECB in a given field each year. Chemical pesticides are less effective than Bt spray and are costly and hazardous.

The mid-1990s saw the production of the first transgenic Bt corn hybrids. As of 2004, approximately 25% of U.S.-grown corn was Bt hybrid corn. A hybrid not approved for human consumption (with a toxin named Cry9C) was grown for feed. Some of this corn was discovered in taco shells and several other corn products. That hybrid has been taken off the market.

Because the continuous expression of the Bt gene in corn puts strong selection pressure on the ECB, mutations for resistance are likely to be selected for. The Environmental Protection Agency requires that a refuge of non-Bt corn be planted in each field. By maintaining a population of nonresistant ECB in the refuge, the spread of resistance genes is slowed. Some seed companies have suggested that a particular Bt hybrid will remain effective for about 3 times as long in fields where growers use refuges. Refuges are required for most transgenic crops and range from 20% to 50% of planted acreage for that crop.

The corn grown in the refuge will mature normally. It will likely be damaged by ECB because the grower is not permitted to spray it with Bt spray or use chemical pesticides that could kill ECB. However, the corn is harvested and sold mixed in with the grain produced by the Bt hybrids. In fact, due to pollen drift, many of the kernels on the non-Bt ears will be Bt seeds.

The seed companies are responsible for informing growers of the EPA rules and are required to instruct the growers in the planting and care of refuges. To obtain seeds produced by biotechnology, growers have been required since 2002 to sign an insect resistance management agreement. However, even with these regulations, there is still a lot of miscommunication, misunderstanding, and noncompliance.