a four-fold rise - Center for Food Safety

More documents

Recommendations

Info

Center for Food Safety – Science Comments – FG72 Soybean 52 Stahlman et al. (2011) state that the original four populations in Kansas likely evolved glyphosate-‐resistance independently, but the rapid emergence across such a broad swath of the state suggests the potential for spread of the original populations, perhaps by resistant seed dispersal, as kochia “tumbleweed” can disperse seeds at considerable distances (see CFS RRSB 2010). CFS (2010) also documents that kochia is a serious weed of both alfalfa and sugarbeets, Roundup Ready versions of which have been recently introduced and are widely grown. GR kochia infesting these RR crops would seriously impair the efficacy of the RR trait; likewise, selection pressure from glyphosate use with these crop systems (especially in rotation with other RR crops, as seen particularly with RR sugar beets, which are frequently rotated with RR corn and/or RR soybeans) could rapidly lead to still more extensive emergence of GR kochia. h. Potential for glufosinate resistant weeds FG72 soybeans engineered with resistance traits for use with isoxaflutole and/or glyphosate, but glufosinate could also be applied if the trait is stacked with FG72 soybean. As discussed above, glufosinate use on soybeans has been growing rapidly since the 2009 introduction of LibertyLink soybeans, but is still used on just 1.3% of soybean acres. Overall use of glufosinate in U.S. agriculture is minuscule – estimated above at just 1.92 million lbs./year – in comparison to glyphosate, hence there has been much less selection pressure for weeds to evolve resistance to glufosinate. The entirely foreseeable emergence of weeds resistant to both isoxaflutole and glyphosate with the introduction of FG72 soybean would drive greater use of glufosinate in the future. However, there is already reason to question the efficacy of glufosinate in forestalling or managing resistance to isoxaflutole and/or glyphosate in the event that it were to be used. Avila-‐Garcia and Mallory-‐Smith (2011) have recently discovered Italian ryegrass resistant to both glyphosate and glufosinate in an orchard with a history of glyphosate use, but where little or no glufosinate had been used, and suspect a common, non-‐target site mechanism – reduced translocation – for resistance to both herbicides. They regard the potential for evolution of resistance to both herbicides where both glyphosate-‐ and glufosinate-‐resistant crops are grown as an “alarming weed management issue.” Growers of FG72 soybean who have GR Italian ryegrass infestations would likely rely heavily on both isoxaflutole and glufosinate, since isoxaflutole is not as effective on grasses as on broadleaf weeds. Tranel et al. (2010) find that glufosinate may soon be the only effective post-‐emergence herbicide option for control of already multiple-‐HR waterhemp in soybeans; that glufosinate is not well-‐suited to control this weed; and that “there is no reason to expect [waterhemp] will not evolve resistance to glufosinate if this herbicide is widely used.” As noted above, waterhemp has already evolved massive resistance to glyphosate and has shown the ability to develop resistance to isoxaflutole as well. Bayer CropScience’s FG72 soybean as the “solution” to weeds resistant to glyphosate, ALS inhibitors, as well as other modes of action, just as RR crop systems were regarded as the solution to prior resistance, particularly epidemic ALS inhibitor-‐resistant weed populations in
Center for Food Safety – Science Comments – FG72 Soybean 53 soybeans. As documented above, dual resistance to glyphosate and ALS inhibitors is quite common in weeds, particularly common waterhemp and Palmer amaranth. If HR crop systems really did “solve” resistant weed problems, one would certainly not expect multiple HR weeds to expand dramatically with their use – yet that is precisely what has happened with its predecessor Roundup Ready system. As also discussed above, there are already very good scientific reasons to suspect that the major near-‐term consequences of widespread use of FG72 soybean would be to foster resistance to isoxaflutole and glufosinate, with extremely serious consequences for farmers, the agricultural economy, the environment and public health. i. Stewardship It is highly doubtful whether Bayer CropScience’s stewardship plan for FG72 soybean (DEA at 58) will be effective in forestalling weed resistance to isoxaflutole. For at least 15 years, companies and weed scientists have touted voluntary stewardship guidelines and best management practices as the chief bulwark against evolution of resistant weeds in the context of HR crop systems. These programs and exhortations have demonstrably failed with Roundup Ready crops, or there would not be an epidemic of glyphosate-‐resistant weeds. A critical assessment of Monsanto’s failed stewardship messages, practices and actions may be useful to inform an assessment of Bayer CropScience’s similar approach. Monsanto insisted that weeds would not evolve glyphosate resistance to any serious extent when RR crops were first being introduced, based mostly on assumptions concerning the presumed rarity of glyphosate-‐resistance mutations, the lack of glyphosate-‐resistant weed evolution up to that time, and nuances of the herbicide’s mode of action (Bradshaw et al. 1997). Many weed scientists were not convinced, and called for serious measures to forestall evolution of GR weeds (Freese 2010, question 1). Monsanto introduced its RR crops as “RR crop systems” designed for sole reliance on glyphosate for weed control. Even several years after GR weeds had emerged, Monsanto promoted “glyphosate-‐only” weed control programs in farm press advertisements that leading weed scientists castigated as irresponsible for promoting weed resistance (Hartzler et al. 2004). Monsanto continues to advocate voluntary stewardship programs as an effective means to forestall or manage GR weeds, despite their obvious failure. If Bayer CropScience was serious about stewardship, the company would include a requirement that farmers not use isoxaflutole with FG72 soybean and corn in sequential years, or on FG72 soybean in sequential years, providing a gap. This is because corn and soybeans are quite often grown in a two-‐year rotation (DEA at 28), and continual use of isoxaflutole and/or glyphosate on both corn and soybeans, year-‐in and year-‐out, is the surest way to foster rapid evolution of isoxaflutole-‐resistance in already glyphosate-‐resistant weeds. 18 Yet Bayer CropScience’s stewardship plan for FG72 soybean has no such requirement. Instead, it suggests that growers “…apply no more than two applications of a single herbicide MoA to the 18 As noted above, the increasing use of RR corn by farmers already growing RR soybeans led to continual, year-‐in, year-‐out glyphosate selection pressure that is the major factor driving GR weed evolution in the Midwest.
Page 1 and 2: Docket No. APHIS-‐2012-‐0
Page 3 and 4: Center for Food Safety - Scien
Page 51: Center for Food Safety - Scien
Page 85 and 86: ___________________________________
Page 87: ___________________________________

a four-fold rise - Center for Food Safety

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?