Impact of Bt corn pollen on monarch butterfly populations: a risk assessment. Proc Natl Acad Sci U S A

Department of Environmental Biology, University of Guelph, Guelph, ON, Canada N1G 2W1.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 11/2001; 98(21):11937-42. DOI: 10.1073/pnas.211329998
Source: PubMed


A collaborative research effort by scientists in several states and in Canada has produced information to develop a formal risk assessment of the impact of Bt corn on monarch butterfly (Danaus plexippus) populations. Information was sought on the acute toxic effects of Bt corn pollen and the degree to which monarch larvae would be exposed to toxic amounts of Bt pollen on its host plant, the common milkweed, Asclepias syriaca, found in and around cornfields. Expression of Cry proteins, the active toxicant found in Bt corn tissues, differed among hybrids, and especially so in the concentrations found in pollen of different events. In most commercial hybrids, Bt expression in pollen is low, and laboratory and field studies show no acute toxic effects at any pollen density that would be encountered in the field. Other factors mitigating exposure of larvae include the variable and limited overlap between pollen shed and larval activity periods, the fact that only a portion of the monarch population utilizes milkweed stands in and near cornfields, and the current adoption rate of Bt corn at 19% of North American corn-growing areas. This 2-year study suggests that the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible.

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Available from: Blair D Siegfried, Mar 14, 2014
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    • "The stated assessment endpoint for this evaluation was " healthy and sustainable avian populations in upland habitats, " a populationlevel assessment endpoint. A similar illustration is offered by an assessment of the risk to monarch butterfly populations from exposure to Bt corn pollen (Sears et al. 2001), which related mortality and sublethal growth effects in monarch larvae to pollen exposure probabilistically. However, as has been argued many times (e.g., Barnthouse 1993, see also Barnthouse et al. 2006), risks to populations cannot be assessed comprehensively using organism-level toxicity data alone (but see Suter et al. 2005), owing to the spatial and temporal context of multiple stressors in the environment among other issues. "
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    ABSTRACT: Wildlife populations are experiencing increasing pressure from human-induced changes in the landscape. Stressors including agricultural and urban land use, introduced invasive and exotic species, nutrient enrichment, direct human disturbance, and toxic chemicals directly or indirectly influence the quality and quantity of habitat used by terrestrial and aquatic wildlife. Governmental agencies such as the U.S. Environmental Protection Agency are required to assess risks to wildlife populations, in its broadest definition, that result from exposure to these stressors, yet considerable uncertainty exists with respect to how such assessments should be conducted. This uncertainty is compounded by questions concerning the interactive effects of co-occurring stressors, appropriate spatial scales of analysis, extrapolation of response data among species and from organisms to populations, and imperfect knowledge and use of limited data sets. Further, different risk problems require varying degrees of sophistication, methodological refinement, and data quality. These issues suggest a number of research needs to improve methods for wildlife risk assessments, including continued development of population dynamics models to evaluate the effects of multiple stressors at varying spatial scales, methods for extrapolating across endpoints and species with reasonable confidence, stressor-response relations and methods for combining them in predictive and diagnostic assessments, and accessible data sets describing the ecology of terrestrial and aquatic species. Case study application of models and methods for assessing wildlife risk will help to demonstrate their strengths and limitations for solving particular risk problems.
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    • "Research has established potential impacts on many terrestrial organisms, including monarch butterfly (Danaus plexippus) populations (Losey et al. 1999; Sears et al. 2001; Kaplan 2002; Dively et al. 2004), soil bacteria (Baumgarte & Tebbe 2005), slugs (Hönemann & Nentwig 2010), ladybirds (Schmidt et al. 2009), common green lacewings (Chrysoperla carnea) (Hilbeck 2001), earthworms (Zwahlen et al. 2003), and land snails (Kramarz et al. 2009). Although knowledge on Bt toxin impacts on terrestrial ecosystems has been assessed (Barton & Dracup 2000; Conner et al. 2003; Rose and Diverly 2007), there is uncertainty regarding the impacts of Bt corn detritus on stream ecosystems. "
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    ABSTRACT: Bt crops are one of the most commonly used genetically modified crops worldwide. Bt crops contain a gene that is derived from the bacteria Bacillus thuringiensis, which produces the Cry1Ab toxin. Bt corn that contains the Cry1Ab toxin is used throughout the Midwest United States to control crop pests such as the European corn borer (Ostrinia nubilalis). Headwater streams in regions known for intensive agriculture receive Bt corn detritus after the fall harvest, which is then consumed by a diverse community of stream invertebrates. The rusty crayfish (Orconectes rusticus) is a common invertebrate detritivore in these headwater streams. Both isogenic and Bt corn were grown under the controlled environmental conditions of a greenhouse and, after senescence, were tested for nutritional equality. Rusty crayfish were exposed to one of several detrital treatments composed of Bt corn, Bt corn plus American sycamore (Platanus occidentalis), isogenic corn alone, isogenic corn plus P. occidentalis, or P. occidentalis alone for 8 weeks. Both strains of corn were grown under the controlled environmental conditions in a greenhouse and were tested for nutritional equality after senescence. Crayfish were housed in live streams with a water temperature of 12.8 °C and a 12:12 h light-to-dark photoperiod. Survival and growth of animals within each experimental treatment were monitored each week. After 8 weeks of exposure, there was no statistically significant difference in growth between crayfish in Bt and isogenic treatments. However, survivorship was 31 % lower in the Bt treatment compared with the isogenic treatment. These results suggest that the Bt corn and isogenic corn were of equivalent nutritional value but that Bt corn does have a toxic effect on rusty crayfish during long-term exposure.
    Archives of Environmental Contamination and Toxicology 07/2014; 67(3). DOI:10.1007/s00244-014-0061-3 · 1.90 Impact Factor
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    • "Studies of entomofaunistic diversity in agroecosystem are rare (Pérez et al. 2011). There are studies on how insect diversity behaves in transgenic crops with pest insects (Betz et al. 2000), nontarget organisms (Naranjo 2005, Torres and Ruberson 2008, Yu et al. 2011, Comas et al. 2013, Dhillon and Sharma 2013), resistance (Wilson et al. 1992, Benedict et al. 1996) and insects without agricultural importance (Sears et al. 2001). Plants with Cry proteins are resistant to damage by certain insects (Romeis et al. 2008, Sainsbury et al. 2012). "
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    ABSTRACT: Studies are lacking of entomofaunistic diversity studies in artificial ecosystems such as agroecosystems. It is estimated that in agroecosystems only 3% of the species behave as pests and 97% are auxiliary fauna. Transgenic cotton (Gossypium hirsutum L.) has a protein toxic against some lepidopterans; however, some studies mention that it harms other orders of insects. The purpose of this study was to identify the entomological diversity in transgenic cotton in the State of Coahuila, Mexico (25°49’25’’N and 103°13’21’’W). Entomological net, pitfall traps, and direct sampling were used each week. All adults collected were identified to species per family and order and deposited in the entomological collection of the Biological Sciences Faculty of Juárez University of Durango State. In total, 570 specimens were collected, of which 192 seemed to be distinct species belonging to 57 families in 10 orders. The order with the most insects was Hemiptera with 40% of the specimens, followed by Hymenoptera and Coleoptera, with 22 and 19%, respectively. The orders with the most species were Hymenoptera with 42% and Hemiptera with 30%. The families with the greatest numbers of insects were Cicadellidae with 140 and Curculionidae with 47. The families with the most species were Sphecidae with 15, Cicadellidae with 14 and Formicidae with 13. Only one insect was collected from each of 16 families.
    Southwestern Entomologist 06/2014; 39(2):317-326. DOI:10.3958/059.039.0209 · 0.46 Impact Factor
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