Monarch butterfly pollen

Concerns over the safety of transgene introduction into environment was sensitized early in the GMO debate with significant focus on the potential toxicity of Bt endotoxins to monarch butterfly [Danaus plexippus) larvae exposed to transgenic pollen. Early data suggested that Bt corn pollen could result in potentially significant reactions in the monarch gut. 

Ecological concerns are real as we do not know what may occur with the widespread propagation of transgenic plants. There were initial fears that Bt corn was toxic not only to the European corn borer but also to the monarch butterfly larvae that may eat milkweed leaves laced with Bt corn pollen. However, EPA studies dismissed this threat. It is possible that other insects, not intended as targets of bioengineered proteins, may also be affected. It is absolutely essential that these ecological issues be addressed. However, these are not food safety issues. The same concerns occur with the widespread use of organic pesticides relative to runoff and water pollution. Both must be addressed on their own merits. 

Even if the main target of a toxin is an insect which causes considerable damage to the crop, very often other insects can feed on the plant. If they are sensitive to the expressed toxin, they will also be affected which, of course, is advantageous in terms of crop protection. However, some insects could be affected in a nonintended way. An example of this is the monarch butterfly Danaus plexippus), a mythic butterfly of North America. Losey et al. [88] observed a higher mortality rate in butterfly larvae fed milkweed coated with 5t-maize pollen as compared to larvae fed leaves coated with nontransformed maize pollen or with leaves free of pollen. However, it is important to note that this study was performed under artificial laboratory conditions which do not reflect most of the characteristics of the monarch way of life [89]. In a very recent report, the EPA (September 22, 2000), on the basis of further trials, concluded that monarch butterflies were at very little risk from Bt com products, contrary to widely published reports. EPA further found that In fact, some authors are predicting that the widespread cultivation of Bt crops may have huge benefits for monarch butterfly survival. ... 

In response to public concerns raised by recent monarch butterfly/Bt-corn pollen studies [26, 27], tests are also under way to compare the respective effects of purified lepidopteran-active Bt toxins, of a Bt biopesticide preparation, and of a conventional chemical pesticide commonly used on corn and potentially present when pollen is produced (M.H. Pham-Delegue, unpubhshed data). Such work is expected to assess the biosafety correlates of the different methods used for crop protection, rather than simply comparing the effects of GM plants versus control plants, which is not agronomically realistic. 

Jesse, L.C.H. and Obrycki, J.J. (2000). Field deposition of Bt transgenic corn pollen Lethal effects on the monarch butterfly. Oecologia, available at athene.em.springer.de. 

Although Bt corn pollen imder certain conditions has the potential of adversely affecting the population levels of monarch butterflies and other non-target Lepidoptera, we consider these impacts to be minimal when compared with habitat loss and the widespread use of pesticides throughout the ecosystem. 

Impact of Bacillus ihuringiensis Corn Pollen on Monarch Butterfly Populations... 

In May of 1999, a note submitted to the editor of Nature from scientists at Cornell University purported to demonstrate that pollen from a Bt com hybrid caused harm to monarch butterfly larvae diat consumed it widi their diet of milkweed leaves This led to the formation of a collaborative group of scientists from Canada and the United States to investigate the nature of pollen from Bt com hybrids and the potential of pollen from these commercial hybrids to intact populations of monarch butterflies in the Com Belt. 

In fliis paper, a weight-of-evidence approach is described for the risk of exposure of monarch larvae to Bt com pollen and the inq>act of such etqrasure on populations of the monarch butterfly in eastern Norfli America (2). Our conclusions are based on collaborative research by scientists in the United States and Canada (5-6). This approach to risk assessment has been performed for many non-target species in relation to pesticides (7-70), industrial by-products (77-75) and other potential toxicants found in the environment (7 ). The approach to fliis process is consistent, well documented and standardized. It requires consideration of both flie expression of a toxicant and the likelihood of... 

Anderson, P.L., R.L.Hellmich, J.R. Prasifka, and L.C. Lewis. 2005. Effects on fitness and behaviour of monarch butterfly larvae exposed to a combination of CrylAb expressing corn anthers and pollen. Environ. Entomol. 34 944-952. 

Sears, M.K., R.L. Hellmich, D.E. Stanley-Horn, K.S. Oberhauser, J.M. Pleasants, H.R. Mattila, B.D. Siegfi"ied, and G.P. Dively. 2001. Impact of Bt corn pollen on monarch butterfly populations A risk assessment. Proc. Natl. Acad. Sci. (USA) 98 11937-11942. 

Wolt, J.D., R.K.D. Peterson, P. Bystrak, and T. Meade. 2003. A screening level approach for non-target risk assessment transgenic Bt corn pollen and the monarch butterfly (Lepidoptera Danaidae). Environ. Entomol. 32 237-246. 

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