Bt Corn Case Study

Bacillus thuringiensis, more commonly known as Bt, is a type of soil bacterium that naturally occurs in nature and which produces insecticidal toxins. There are several species of insects to which the Bt endotoxin is deadly. When one of these pests tries to digest part of a plant with the protein Bt delta endotoxin in it, the insect’s digestion system becomes paralyzed and eventually kills the bug. Many crops, including corn, have been genetically modified to include the Bt gene. Bt corn then becomes resistant to pests such as caterpillars and rootworms, namely the European corn border.
This new technology is great for farmers who can save thousands each year on blanket pesticide applications. However there are already problems with the Bt endotoxin. Insects seem to be developing an immunity to the Bt much sooner than scientists could have ever predicted. Bt corn was introduced in 2003. Already there are multiple cases in four mid-west states in which rootworms have been reported to have damaged the roots of Bt corn.
The most popular theory as to why insects are already becoming immune to the Bt corn is that farmers are misusing the product. It has long been common practice to rotate crops in order to slow the spread of pests. However, in recent year corn prices have reached an all time high, and farmers are giving up crop rotation in favor of growing the profitable corn each year. The idea is that when farmers plant the same Bt corn every year, pest insects begin to evolve and will eventually become completely immune to the strand. So the question becomes, are farmers completely to blame for the rapidity by which these caterpillars are becoming immune to Bt corn, or could there be another reason that explains why Bt is not 100% effective?
I believe that while Farmer’s bad habits no doubt have some impact on the issue, I am of the belief that there could be another explanation as to why the effectiveness of Bt corn is not complete. I believe that it could be a matter of how the corn plants are inserted with Bt that is causing some of the problem. I believe that it could be possible that there are certain hybrid varieties of Bt corn in which the roots may not contain Bt levels that are high enough to effectively kill their target. According to an article by F.B. Peairs of Colorado State University, there are two factors that control where the Bt delta toxins are produced in the plant and how much the plant will produce. These factors are called the “event” and the “promoter.” Every seed company uses different events and promoters so each company’s hybrids will be different in which parts of the plant produce the Bt toxin.
The event is the act of physically inserting the Bt toxin into the plant. Depending on where the Bt gene is inserted into the corn plant, the plant will produce different levels of Bt in different parts of the plant. There is no technology out there yet to control exactly where the plant is injected so each event results in plants that differ in where and how much Bt endotoxin they produce. The promoter then is in control of deciding which parts of the plant receive certain levels of the Bt. Since there are several types of promoters, and each different promoter determines a different amount of Bt that is produced, there is a great variety among each plant as to where and how much of the Bt endotoxin is produced. It is also because of this, that the structure of the plant and the amount of Bt produced in the leaves vs. the stalk vs. the roots can vary dramatically.
With this in mind, I am of the opinion that it could very well be that the reported cases of rootworm damage could have come from plants in which did not have Bt in the roots. Every article I read talked about how it was unclear as to which part of the plant contained the Bt and nobody could give a definitive answer as to how much Bt each plant produces. It is because of this uncertainty of the experts along with my understanding of how the Bt endotoxin is distributed through the plant, that I have come to believe it possible that the reported cases of root damage by rootworms could have been because the plants in question may not have had sufficient levels of Bt.