1. Poster board divided into grids containing 4 columns and 4 rows. Each square represents a hotel room/corn plant and needs to have a slot cut to accommodate the cards as the corn borers “check in”. The analogy of “hotel rooms” refers to the corn plants that the corn borer larvae will be feeding and growing on. The corn plant is a fully accommodated suite that the European corn borer use for food and protection.
2. Printed corn borer cards and plant type cards available here for print in pdf or Microsoft word document.
European corn borer cards:
1/3 of the insects are labeled susceptible and will die after eating Bt (SS)
1/3 of the insects are labeled carriers and will die after eating Bt (RS)
1/3 of the insects are labeled resistant and will survive to produce offspring (RR)
one of each type for every hotel room
1. Hotel rooms will be divided into a 4X4 grid. Cut two slots in each “room” to accommodate the cards with the corn borer and corn cards. The slots should be placed one above the other leaving 3 inches between each slot within each square (see diagram)
2. Divide the corn borer cards into a set of 16, one for each hotel room. The ratio of corn borer cards in this set should be SS=10, SR=4, RR=2. This ratio roughly mimics the distribution of traits in a natural population.
3. In each grid place a corn borer card in the top slot. This card should be turned around so that you cannot see the picture of the larvae. Distribute one in each hotel room as they will be checked in randomly.
4. In the first exercise, feed only Bt corn to insects. Place a Bt corn card in the bottom slot of each square.
5. Once each slot is filled, turn around all corn borer cards to determine the effect on the corn borers residing in the hotel room. SS and SR corn borers residing in the Bt corn hotel rooms will die. SS and SR corn borers residing in the refuge hotel rooms will survive. RR insects in all rooms will survive. These survivors will mate.
6. Create a new generation with surviving insects. Use the population chart to determine what traits the next generation will have. The population chart is found here in pdf format or Microsoft excel document.
7. Repopulate the field, as in step #3, with the next generation of corn borer larvae and observe the results. Obviously only resistant (RR) corn borers will exist the second year.
8. Discuss the results of the first all Bt corn planting.
9. Repeat the experiment providing an area of non-Bt refuge in your field. In the real world farmers are required by law to provide at least a 20% refuge to ensure susceptible corn borers. Have your students determine how much refuge they would need to plant (how many squares) to insure that resistance is kept at a minimum 2 per 16, or reduced to 0. You may not want to tell your students the correct number of hotel rooms to plant with refuge. Let them come up with the amount and experiment.
10. Repopulate the field as in steps 2 and 3
11. Flip cards over to determine what happens to the larvae.
12. Create new generation with surviving insects. Use the chart to determine the traits of the offspring.
13. Repeat the experiment with refuge, as many times as needed to get a correct number of susceptible SS corn borers.
14. Discuss the results.
1. Review the need to maintain susceptible populations of insects.
2. Discuss the merits and risks of selective mating of populations.
3. Develop a set of guidelines for planting Bt corn.
European corn borers mate in weedy field edges and pairing is thought to be random.
Mixing of seed types is a concept that many students will wish to attempt. However, in real world applications refuge and Bt corn is planted in separate blocks or stripes in order to help preserve susceptible populations.
Additional information about refuge mangagement can be found by clicking
Additional Articles for Review
Biotechnology in Food and Agriculture at the Food & Agriculture Organization of the United Nations. http://www.fao.org/biotech/index_glossary.asp
Canadian Plant Inspection Agency, Plant Health and Production Division, Plant Biosafety Office. http://www.inspection.gc.ca/english/plaveg/pbo/btcormai1e.shtml February 8, 1999.
EPA, Office of Pesticide Programs. http://www.epa.gov/pesticides/biopesticides/otherdocs/bt_position_paper_618.htm
Nebraska Cooperative Extension http://www.ianr.unl.edu/pubs/insects/nf425.htm NF00-425 Revised November 2000.
This group activity can be based upon the results the students obtained in the exercise. Track the number of insects of each type through the successive generations and have students record and submit data. Each student should be able to develop a refuge that would maintain the insect susceptibility using the data as a guideline. Compare student recommendations with the guidelines from the EPA located at http://agbiosafety.unl.edu/refugebuilder.shtml