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Genetically Modified Crops: Caterpillars versus Aphids

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.

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Author: Roberta Attanasio

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4 Comments

  1. Genetic engineering hold a lot of good potential for the future of our food supply, both quality and quantity, and we have been doing this for a very long time. A problem seems to be that the pace of GMO development allows much faster turnaround time. Any ‘mistakes’ we make in the process from lab to field to table can quickly expose global populations too fast for corrective action to take place adequately for societal wellbeing. If the AG process, focused too heavily on profit-taking at the expense of high quality science and ‘ground-truthing’ of the products, does not adequately cover all of the due diligence bases before wide dispersal of understudied GMO products, there is much higher risk of adverse effects. Currently nearly all GMO products are designed as pesticide resistant organisms so that higher amounts of glyphosate can be applied and remain as food residue. As weeds have rapidly adjusted to reduce the effectiveness of glyphosate, increased applications are needed. This becomes increasingly problematic, and more innovation in weed control technique is needed that can reduce toxicologic potential environmentally. The industry, instead of applying some of the ‘profit’ to develop far less toxic alternatives, appear to be taking a less responsible approach in falling back on short-term profit gain by producing GMOs that use 2,4,D and dicamba resistance. These toxic chemicals are even more toxicologically problematic than glyphosate. This shortcut by industry is moving in the wrong direction and harming the ability to gain less toxic and innovative approaches to safe food production. There is urgent need for less toxic, or non toxic, innovation for AG production. Industry appears to be stuck using shorter term thinking and short term profit gain to the detriment of longer term societal gain for a more sane future.

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  2. I just hope GMOs don’t come here. I’m very interested in knowing what else Professor Romeis is studying about all of this. We need more of these studies because I suspect that the impact on the environment is way higher compared to what we think now. Makes me want to become a scientist and go to work with him to help all of us live better on this planet.

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  3. The truth is that farming practices should be changed all around the world – there is one word to remember: SUSTAINABILITY. We need sustainable farming practices, with or without GMOs.

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  4. This post makes a very important point, and we should ask two questions. One is: are GMOs safe for us? And the other one is: are GMOs safe for the environment? We need more answers to both questions. The problem is there are too many types of GMOs and what we find for a type of them may be very different from what we find for other types.

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