By Roberta Attanasio
To label or not to label? The debate is still on — despite the defeat of the ballot initiative in Washington state that would have required special labels for foods containing genetically engineered ingredients. A year ago, a similar measure was defeated in California. Why? One of the reasons is that there is no scientific evidence to support the notion that genetically modified organisms (GMO) are dangerous — to our health.
The danger here is that “no need for labeling” could be thought of as “no reason to worry”. Even if we should not worry that much about the health risks of GMOs, there are other worrisome aspects may be worth keeping in mind.
Here is an example – with scientific evidence.
Genetically modified Bt cotton plants contain a poisonous substance (a protein derived from Bacillus thuringiensis, a species of soil bacteria) that kills their major enemies, the voracious caterpillars. However, while the Bt poison kills the caterpillars, it helps aphids — those little pests that suck the sap from the stems and leaves of plants — to spread across cotton fields. How?
Jörg Romeis at the Agroscope Reckenholz-Tänikon Research Station in Switzerland and his collaborators provide an answer. The answer comes from a study published in the scientific journal Proceedings of the Royal Society B: Biological Sciences (March 2013) and entitled “Pest trade-offs in technology: reduced damage by caterpillars in Bt cotton benefits aphids”
Caterpillars nibble on cotton plants. The plants fight back by producing defensive substances, which are called terpenoids and knock down caterpillars.
The Bt poison kills the caterpillars before they cause enough damage to induce production of terpenoids by the cotton plants and, because these plants don’t produce terpenoids, aphids grow almost undisturbed.
Although cotton aphids generally do not cause severe agricultural damage as they succumb to their natural enemies out in the open, Romeis and collaborators point out that similar mechanisms could have wide-reaching implications for a large variety of crops and the organisms that are associated with these crops.
May be by attempting to control certain pests, genetic modifications will allow other pests to go out of control.