We've just been alerted by Dr Jonathan Latham, Director of Programmes and Outreach of the Bioscience Resource Project to a new paper on the effects of pollen from the GM maize Bt176 on the European common swallowtail butterfly. The study shows that less than 5 grains of this Bt pollen has a negative impact on the butterfly's life history.
The summary of the paper is given below. As it notes, uptake of Bt maize pollen led to swallowtail larvae consuming less plant material, having a lower body weight, and taking longer to develop. Larvae that consumed Bt-maize pollen also had a lower body weight as adult females and smaller forewings as adult males.
It's also worth noting that although this is a lab study and field conditions can be different, the pollen densities in this study are in accordance with maize pollen densities found on swallowtail host plants in the field. In fact, the field densities can be much higher, notably during the pollen shedding period of maize fields. The pollen shedding time also usually spans a much longer period than the 48 hours of this study. This might suggest that the actual impact of the Bt maize pollen on butterflies might be considerably greater.
The researchers conclude that possible effects of Bt maize on European butterflies and moths must be evaluated more rigorously before Bt maize cultivation expands. It's certainly alarming that this GM maize was approved for commercialization in 1997 and we're now looking at the results of this simple lab study showing its negative effects 9 years later!
Bt maize effects on Papilio machaon
The effects of pollen consumption of transgenic Bt maize on the common swallowtail, Papilio machaon L. (Lepidoptera, Papilionidae)
Andreas Lang a, Eva Vojtech a,b
a Bavarian State Research Centre for Agriculture, Institute of Plant Protection, Lange Point 10, D-85354 Freising, Germany b Institute of Environmental Sciences, University Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland Received 10 March 2005; accepted 31 October 2005
Effects of exposure to maize pollen of event Bt176 (cultivar "Navares") on the larvae of the European common swallowtail (Papilio machaon L.) were studied in the laboratory. First instar larvae were exposed to different pollen densities applied to leaf disks of Pastinaca sativa L. for 48 h. Pollen densities applied in this study were in the range recorded from the field. Larvae which were exposed to higher Bt maize pollen densities consumed more pollen and had a lower survival rate. The LD50 with regard to larvae surviving to adulthood was 13.72 pollen grains consumed by first-instar larva. Uptake of Bt maize pollen led to a reduced plant consumption, to a lower body weight, and to a longer development time of larvae. Effects on pupal weight and duration of the pupal period were present but less pronounced and smaller than effects on larvae. Larvae having consumed Bt-maize pollen as first instars had a lower body weight as adult females and smaller forewings as adult males. We conclude that possible effects of Bt maize on European butterflies and moths must be evaluated more rigorously before Bt maize should be cultivated over large areas.
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