|Ladybird. Kirsty Coghill [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)],|
via Wikimedia Commons
Ladybirds are predators of many small insects, and therefore provide and important natural pest-control service to agriculture. In 2008, Angelika Hilbeck and her colleagues at the Swiss Federal Institute of Technology published a study on the effects of Bt-toxins on ladybirds.
Noting that the assessments of GM crops have attracted criticism because they're based on the those used for chemicals, Hilbeck aimed to develop a more appropriate method. Her team improved the protocol by using Bt toxins in activated form (which is what Bt crops are supposed to produce) and by testing ladybird larvae (grubs) rather than the much less vulnerable adult insect.
Purified, activated Bt toxin was accordingly sprayed onto eggs of the flour moth, which are considered a high-quality food for ladybird-type insects. Such eggs were supplied to the developing larvae as their sole food-source for the duration of their existence.
One of the toxins tested was Bt protein 'Cry1Ab' which is generated, for example, by MON 810 maize approved for cultivation in the EU. When this was fed to the developing ladybirds at various concentrations, up to 44.2% of the first-stage, newly-hatched, larvae died (compared with 14.2% of control larvae with no exposure to the toxin). The surviving later-stage grubs weren't further affected.
Cry1Ab is claimed to be highly specific against moths which are a major pest in maize and cotton, and is marketed as 'environmentally-friendly' because it isn't supposed to kill other types of insects. Hilbeck's finding was among some 30 other studies which raised questions about the environmental effects of MON 810 and was used by the German government to ban the crop. The paper was, therefore, very unwelcome in biotech-circles.
What happened next is a familiar shoot-the-messenger story. Within weeks of the damning study appearing in print, two letters appeared in the journal Transgenic Research. These letters amounted to a lengthy, “disrespectful” and “unnecessarily confrontational” attack by fellow scientists. For example, the data were referred to as “alleged” and “supposedly showing a negative impact”*, the research was categorised as “ill-conceived and shoddy”, and the title of one even suggested the study was “pseudo science”. Hilbeck's team were not offered any opportunity to respond.
Barely a year later, Transgenic Research published a rushed study by another Swiss team led by Fernando Alvarez-Alfageme. This succeeded in demonstrating that Bt toxins had no adverse effects on ladybird larvae, declaring Hilbeck's results to be “artifacts of poor study design and procedures”, and the German decision-makers guilty of failing to evaluate the quality of the individual scientific studies used in its decision-making process on GM maize.
The lynch-pin of Alvarez-Alfageme's investigation was that ladybird grubs “do not consume entire prey items but instead puncture the prey and suck out the contents”. Visual observations, verbally reported, indicted that no parts of the moth egg shells were consumed, therefore the larvae “cannot be dosed with test compounds deposited on the outside of the eggs”. To present the ladybirds with “more realistic routes of exposure” to the toxins, this team used a Bt-laced sugar solution in one feeding experiment, and spider mites which had been fed on Bt maize leaves in another.
Aware of what seemed like a concerted attempt to discredit her research in these three publications (all appearing in the same scientific journal), Hilbeck carried out a further set of experiments using a further improved technique and designed to disprove the Alvarez-Alfageme's effort.
Hilbeck first subjected European corn borer, a pest which MON 810 maize is actually designed to kill, to Alvarez-Alfageme's protocol. The Bt-sensitive worms were affected only slightly or not at all. There was no need to look far for an explanation for this discrepancy: Alvalrez-Alfageme had exposed his ladybirds to the Bt toxin for only 24 hours, followed by a long (in lady-bird terms) toxin-free recovery period. This aspect of the method wasn't mentioned in the abstract.
When an attempt was made to repeat the toxic sugar solution feeding study as described, the liquid simply dried up rendering it unavailable to the test larvae.
No attempt was made by Hilbeck to repeat Alvarez-Alfageme's Bt-fed spider mite feeding study. The presence and nature of other proteins and gut microbes are known to interact with Bt proteins and can yield unexpected effects: introducing a layer of complexity in the form of a third organism-species as food simply raises more questions than it can possibly answer.
Important new data on the feeding habits of ladybird larvae was presented in photographic form: these grubs have short biting mouth-parts which they sink “deeply into the eggs” afterwards “biting their way through the egg shells ... the egg content leaks out of the eggs and the larvae lick and suck up whatever they can get out of it”. In other words, ladybird young are messy eaters, bound to be in contact with anything on the outside of their food. Hilbeck went on to confirm that her larvae had in fact ingested Bt toxin while eating the moth eggs by chemical analysis of their bodies.
It's unclear why the journal, Transgenic Research, should have become a platform for this concerted attack on science. Trangenic Research is associated with the International Society of Transgenic Technology established in Spain in 2006: the Society website specifies its aims as to “encourage knowledge generation ... used for the genetic modification of animals, in particular ... in the biology, biomedicine and biotechnology disciplines”. The journal isn't so restricted and publishes any type of GM research, animal, plant, or microbes. Perhaps its access to expertise in the fields of environmental science and toxicology are inadequate to evaluate such submissions adequately: indeed this may be part of the bigger picture of why GM development and its safety assessment have become so polarized. However, since there are signs here, the Transgenic Research is being used by the pro-biotech lobby for political ends, it might be worth remembering the name: it might well crop up again next time someone publishes GM-unfriendly results.
The most interesting thing to come out of all this is how little is known about the environmental interactions of any Bt toxin, and that “even in target pests the mode of action of Bt toxins is not fully understood” (Schmidt).
All these warring scientists did agree on one thing: Bt toxins generated in GM plants end up inside the animals living on and around them (including humans). So, what happens when you stack up six different Bt toxins in the same plant, like Monsanto's super-duper insect-killing GM maize machine, 'SmartStax'?
If you're wondering about the increased presence of ladybirds recorded in Bt cotton fields in China (see APHID-FRIENDLY COTTON - July 2012), this crop generates a different Bt protein from the one tested by Hilbeck. However, the next generation of GM cotton there will likely have Cry1Ab stacked on top of what it has now, and Chinese ladybirds might be cut off in their prime.
If the name 'Ricroch' seems familiar, this is the same French scientists who cobbled together a review of long-term and multigenerational GM feeding studies in 2011. The timing and nature of this review looked suspiciously like a counter-attack on other scientists whose earlier reviews had not been favourable towards GM. Check out THREE REVIEWS OF GM SAFETY - March 2012.
Remember these stories. If GM was safe to eat and safe for the environment, scientists would be able to prove it without resorting to ungentlemanly behaviour.
- Jörg E. U. Schmidt et al., 2009, Effects of Activated Bt Transgene Products (Cry1Ab, Dry3Bb) on Immature Stages of the Ladybird Adalia bipunctata in Laboratory Ecotoxicity Testing, Archives of Environmental Contamination Toxicology, 56
- Lethal Effects of Genetically Modified Bt Toxin Confirmed On Young Ladybird Larvae, www.sciencedaily.com, 27.02.12
- Bt Toxicity Confirmed: Flawed Studies Exposed, Institute of Science in Society Report 11.07.12
- Agnès Ricroch et al., 2010, Is the German suspension of MON810 maize cultivation scientifically justified?, Transgenic Research 19
- Stefan Rauschen, 2010, A case of “pseudo science”? A study claiming effects of the Cry1Ab protein on larvae of the two-spotted ladybird is reminiscent of the case of the green lacewing, Transgenic Research 19
- Fernanado Alvarez-Alfageme et al., 2011, Laboratory toxicity studies demonstrate no adverse effects of Cry1Ab and Cry3Bb1 to larvae of Adalia bipunctata coleoptera Coccinellidae): the importance of study design, Transgenic Research, 20
- Angelika Hilbeck et al., 2012, A controversy re-visited: is the coccinellid Adalia bipunctata adversely affected by Bt toxins?, Environmental Sciences Europe, 24:10
- Angelika Hilbeck et al., 2012, Underlying reasons of the controversy over adverse effects of Bt toxins on lady beetle and lacewing larvae, Environmental Sciences Europe, 24:9
- Snell Chelsea et al., 2011, Assessment of the health impact of Gm plant diets in long-term and multigenerational animal feeding trials: A literature review, Food Chemical Toxicology
- International Society for Transgenic Technologies, www.transtechsociety.org