Monsanto Canada recently reported that the Canadian Food Inspection Agency (CFIA) has granted approval for its latest GM offering, the intriguingly named “refuge in a bag” Bt corn. With all the hype surrounding GM crops, it would be easy to dismiss this announcement as just another piece of press puff from the GM giant. But unfortunately this new development is actually something we need to keep a close eye on. As we have come to expect, the government has let the GM community police itself, leaving the companies that are peddling the new technology to regulate its use.
First, it is important to understand what a “refuge” is when it comes to GM crops. Despite the fact that Animal Welfare Approved has blogged extensively on the many drawbacks and dangers of GM technology, the concept of “refuge” actually relates to a problem that we haven’t covered in detail before – namely the inevitable development of pest resistance to GM crops.
The requirement for a “refuge” arose because it is widely accepted that pest insects will, over time, develop resistance to the crops that have been genetically modified to poison them. One would logically expect that if you expose a large number of pests to a single pesticide year after year, the survivors will eventually breed, leading in time to the emergence of a resistant population. This same process happens with GM crops – it’s simply that the GM crop has been genetically modified to express the thuringiensis (Bt) insecticide within its plant tissues, rather than the farmer spraying it on to the crops to control the pests. Indeed, the GM companies themselves admit that the development of resistance to their GM crops is inevitable, and the requirement for a “refuge” is promoted as an attempt to preserve the efficacy of the GM technology for as long as possible. So how does this “refuge” system work?
Whenever farmers sow a field with GM crops they are required to plant a certain proportion of non-GM seeds of the same crop type in order to provide a safe place – a so-called “refuge” – so that some insects which are still susceptible to the insecticide can survive and breed. The idea is that these susceptible insects will breed with resistant insects, thereby slowing down the development of resistance among the pest population. If you don’t plant the refuge area then the only insects that survive are those which have developed some resistance to the GM toxin expressed by the crops. If those resistant insects are the only ones that breed, then the entire population will quickly become resistant and the insect-resistant genetic modification will be worthless.
Initially, farmers were required to sow 20% non-GM seed alongside 80% GM seed. But once the GM companies began “stacking” GM traits – that is, incorporating more than one mode of insect protection and herbicide resistance together in the same crop – the requirement dropped to 5% of non-GM crop to be grown with 95% GM. However, farmers were expected to follow strict guidelines on how the non-GM component was to be incorporated in their cropping plans. Farmers had the option of growing blocks of non-GM corn either within a particular field of GM crops or in an adjacent field. Alternatively, farmers could plant strips of non-GM seed within the GM crop, but the strips had to be at least four – and preferably six – rows wide. These blocks or strips then provided a clear non-GM “refuge” area.
So what’s the problem with Monsanto’s “refuge in a bag” system? Well, the requirement for 5% non-GM corn is still there. But instead of the farmer having to buy different bags of GM and non-GM seed, and sow them separately, Monsanto has mixed the 5% non-GM seed in with the GM seed – hence the “refuge in a bag.” On the plus side, this means the farmer can’t get out of planting the non-GM portion (which has been a problem in some states). But what happened to the block or strip of non-GM seed? Well, as the seeds are mixed up together, the non-GM plants now grow scattered throughout the crop, rather than in dedicated areas. So how will a significant population of non-resistant insects survive and breed over time on random single non-GM plants, rather than in dedicated areas?
These thoughts have crossed the minds of others, too. Christian Krupke, an entomologist from the University of Purdue, has real concerns about Monsanto’s “refuge in a bag” technology, namely that using such seed mixes can actually promote greater pest resistance. In a press release from Purdue Krupke says that:
“The concern with refuge-in-a-bag, or seed mixes, has always been sub-lethal exposure with toxic plants and non-toxic plants standing side-by-side. You could have a young corn rootworm beetle larva emerge, feed on a toxic plant but not die, and then move over to a non-toxic plant and feed until reaching adulthood. The larva now has sub-lethal exposure to Bt. That's one of the ways that resistance can develop in an insect population more rapidly… It's that old adage that whatever doesn't kill you makes you stronger. We could be giving those larvae selective advantage in the long term. That was one of the reasons this technology wasn't embraced initially.”
Sub-lethal exposure works the other way, as well, Krupke explains. Larvae could feed on a refuge corn plant and become larger, then move to a Bt plant to continue eating. Because the larvae are larger, and it takes more Bt toxin to kill bigger insects, the larvae might not ingest enough toxin to die.
Aside from Krupke, other published papers, such as Agi et al (2001) and Onstad et al (2011), also express reservations at the efficacy of “refuge in a bag” to ensure the survival of susceptible insects. Even the Environmental Protection Agency has released a report stating that it expects resistance to occur within 8.1 years for a 5% blended refuge, 11.3 years for a 10% blended refuge and 20.2 years for the 20% block refuge.
So it would seem that Monsanto’s “refuge in a bag” is also a “shot in the foot,” as it will actually hasten the spread of resistance to Bt among the insect population. This obviously has huge implications for both GM and non-GM growers. Bt (or Bacillus thuringiensis) is a naturally occurring bacterium that produces proteins called endotoxins that act as a natural insecticide. As Bt is not a synthetic chemical product and it is very selective (it’s only toxic to a very specific range of target pests) it is often used by organic growers. The spread of resistance to this natural pesticide – a product that is selectively fatal to certain insects and non-toxic to just about everything else – could cause real problems for growers who have never embraced GM technology, and certainly had no part in promoting resistance.
So why would Monsanto promote a product that could actively reduce the efficacy of one of its GM seed lines? We’ve seen this time and again with other insecticide and pesticide products. Rather than encourage the sustainable use of pesticides, too often agrochemical companies seek only to maximize short-term sales and profits. Once insect or weed resistance begin to cause problems in the fields, the company can simply abandon it and roll out another “improved” product range – and the whole process starts again. You can bet your bottom dollar that Monsanto will have the next GM crop with a built-in insecticide already in development. Besides, do you really think that Monsanto and the other Biotech companies are worried about creating problems for organic and other responsible growers, who rank among the most vociferous opponents of GM technology? Me neither.
Agi, A. L., Mahaffey, J. S., Bradley, Jr. J. R., and Van Duyn, J.W. (2001) Efficacy of Seed Mixes of Transgenic Bt and Nontransgenic Cotton Against Bollworm, Helicoverpa zea Boddie. The Journal of Cotton Science 5:74-80
Onstad, D. W., Mitchell, P. D., Hurley, T. M., Lundgren, J. G., Porter, R. P., Krupke, C. H., Spencer, J. L., Difonzo, C. D., Baute, T. S., Hellmich, R. L., Buschman, L. L., Hutchison, W. D., and Tooker, J. F. (2011) Seeds of Change: Corn Seed Mixtures for Resistance Management and Integrated Pest Management. Journal of Economic Entomology 104(2)