Bt-Corn
Bt-corn and its Effects on Danaus plexippus
Recently, in response to the chronic problem of insects destroying crops and from the known effects of pesticides on humans and on the environment, a new form of insecticide was discovered, particularly for corn. In this new case, the organism itself is genetically modified for protection. This insect-resistant corn is the new Bt-corn and contains genetic material from the donor organism, a bacterium. Bacillus thuringiensis contains a protein that kills the larvae of Ostrinia nubilalis, European corn borers, but is harmless to other insects (Bessin, 1999). When the Bt is consumed by the larvae, toxins paralyze the insectfs intestines, eventually causing death (Peairs, 2001). A small material of this genetic material is added to the inserted into the Bt-corn and thus enables the Bt-corn to produce its own insecticide. This Bt-corn has the same nutritional value as non-genetically modified corn but with a tolerance to insects (Bessin, 1999). Although Bt-corn may seem like a picture perfect crop, there are questions about it possible harm, which has been causing controversy.
The greatest scientific controversy regarding this new Bt-corn has been the effects that it has on Danaus plexippus | the Monarch butterflies. The larvae feed primarily on milkweed, and if there is milkweed growing next to Bt-corn farms, the Bt-corn pollen drifts onto the milkweed, affecting the Monarch population. To test the effects of Bt-corn pollen on Monarch butterflies, a research team at Cornell University performed an experiment in a controlled environment, where three groups of larvae fed on milkweed leaves either dusted with Bt-corn pollen, non-Bt-corn pollen, or with no pollen. From this experiment, it showed that slightly less than half of the larvae that fed on the milkweed dusted with Bt-corn pollen did not survive to adulthood. In addition, the larvae that survived were less than half of the size of those larvae that did not come into
Recently, in response to the chronic problem of insects destroying crops and from the known effects of pesticides on humans and on the environment, a new form of insecticide was discovered, particularly for corn. In this new case, the organism itself is genetically modified for protection. This insect-resistant corn is the new Bt-corn and contains genetic material from the donor organism, a bacterium. Bacillus thuringiensis contains a protein that kills the larvae of Ostrinia nubilalis, European corn borers, but is harmless to other insects (Bessin, 1999). When the Bt is consumed by the larvae, toxins paralyze the insectfs intestines, eventually causing death (Peairs, 2001). A small material of this genetic material is added to the inserted into the Bt-corn and thus enables the Bt-corn to produce its own insecticide. This Bt-corn has the same nutritional value as non-genetically modified corn but with a tolerance to insects (Bessin, 1999). Although Bt-corn may seem like a picture perfect crop, there are questions about it possible harm, which has been causing controversy.
The greatest scientific controversy regarding this new Bt-corn has been the effects that it has on Danaus plexippus | the Monarch butterflies. The larvae feed primarily on milkweed, and if there is milkweed growing next to Bt-corn farms, the Bt-corn pollen drifts onto the milkweed, affecting the Monarch population. To test the effects of Bt-corn pollen on Monarch butterflies, a research team at Cornell University performed an experiment in a controlled environment, where three groups of larvae fed on milkweed leaves either dusted with Bt-corn pollen, non-Bt-corn pollen, or with no pollen. From this experiment, it showed that slightly less than half of the larvae that fed on the milkweed dusted with Bt-corn pollen did not survive to adulthood. In addition, the larvae that survived were less than half of the size of those larvae that did not come into
Citations: Anonymous. March 29, 2004. "Bt Corn and Monarch Butterflies." Available: http://www.ars.usda.gov/is/br/btcorn/index.html#bt1 [Date visited: 3/2/06]. Bartholomew, C.S.; Yeargan, K.V. 2001. Phenology of milkweed (Asclepiadaceae) growth and monarch (Lepidoptera: Nymphalidae) reproduction in Kentucky and ovipositional preference between common and honeyvine milkweed. Journal of the Kansas Entomological Society. 74 (4): 211-220. Bessin, Ric. 1999. "Bt-corn: What it is and How it Works." Available: http://www.uky.edu/Ag/Entomology/entfacts/fldcrops/ef130.htm [Date visited: 3/2/06]. Divley, G.P.; Rose, R; Sears, M.K., et al. 2004. Effects on monarch butterfly larvae (Lepidoptera: Danaidae) after continuous exposure to Cry1Ab-expressing corn during anthesis. Environmental Entomology. 33 (4): 1116-1125. Milius, S. 2004. Rethinking Refuges? Drifting pollen may bring earlier pest resistance to bioengineered crops. Science News. 165 (20): 310. Peairs, F.B. February 4, 2005. "Bt Corn: Health and the Environment. h Available: http://www.ext.colostate.edu/pubs/crops/00707.htm [Date visited: 3/2/06]. Rice, Marlin. June 14, 1999. "Monarchs and Bt corn: Questions and Answers." Available: http://www.ent.iastate.edu/Ipm/Icm/1999/6-14-1999/monarchbt.html [Date visited: 3/2/06].