a four-fold rise - Center for Food Safety

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Center for Food Safety – Science Comments – FG72 Soybean 22 Michigan and Minnesota, two other corn –growing states, also decided to require more restrictive conditions on the use of isoxaflutole in corn, following public concern about the new herbicide (AP 2003; Hemphill 2003; US Water News). According to press accounts, the company’s response (Aventis was the manufacturer at the time) was to leave Michigan, Wisconsin and Minnesota off of the list of states on the federal label for Balance herbicide, saying that the extra restrictions were too onerous (Hemphill 2003). These states are still missing from the federal label, and no isoxaflutole is used on corn. d. Herbicide use patterns with FG72 soybean result in greater risk to non-‐target species Because FG72 soybean has been engineered to withstand isoxaflutole, thus removing biological constraints, this herbicide can be used from preplant through postemergence, until the FG72 soybean has 4 to 5 trifoliate leaves expanded (Petition at 59). It is therefore likely that isoxaflutole applications will occur later in the season when used with FG72 than with corn. As we have described, these applications on FG72 soybeans may occur as late as mid-‐August, whereas the last likely applications of isoxaflutole on corn would be in July (depending on planting dates, crop varieties, weather, and so on). i. Timing of isoxaflutole applications in the growing season Herbicide applications are more likely to coincide with life-‐stages of plants that are the most sensitive to injury because the FG72 soybean itself is less sensitive to injury during spring and summer than is corn. This is a general outcome of herbicide-‐resistant crop systems: “Increased use of herbicide-‐resistant technology by producers creates the possibility of off-‐site movement onto adjacent conventional crops. The role of total postemergence programs to control grass and broadleaf weeds has expanded with the development of herbicide-‐resistant crops. Because of the diversity of cropping systems in the United States, it is not uncommon for herbicide-‐resistant crops to be planted near susceptible conventional crops. Postemeregence application of a herbicide to a genetically-‐modified (GM) crop often occurs when non-‐GM plants are in the early reproductive growth stage and most susceptible to damage from herbicide drift….Consequently, most drift complaints occur in spring and summer as the use of postemergence herbicide applications increase.” (Lee et al. 2005, p. 15) Plants – both crop and wild species –are often most sensitive to herbicide injury as pollen is forming (Olszyk et al. 2004). ii. Total use of isoxaflutole at landscape level Another way that the FG72 soybean will increase isoxaflutole use is by increasing the total number of acres that are treated with these herbicides. Within a given year, both corn and FG72 soybean acres will be sprayed, as we show in our comments on herbicide use. Also, since corn and soybeans are often rotated on the same acreage within a region. And because of the
Center for Food Safety – Science Comments – FG72 Soybean 23 corn-‐soybean rotation, the likelihood that isoxaflutole will be used on the same acreage year after year is greater as well. At a landscape level this change in 2,4-‐D use pattern will result in a larger number of individuals of a wider array of species in proximity to FG72 soybean and thus isoxaflutole, with attendant impacts. Drift injury will be more likely, and runoff from the greater area may result in higher levels of isoxaflutole in water bodies. e. Injury to non-‐target crops and wild plants from change in use patterns of associated herbicides Herbicide use in agriculture results in injury to non-‐target crops and wild plants, and approval of FG72 soybean that will result in increased herbicide use and changes in herbicide use patterns will increase this risk, as we have discussed in detail. In soybeans, herbicide use, including drift, volatilization and runoff from such herbicide use, can cause poor seedling emergence, yellowing of leaves, necrotic lesions, and cupped leaves, similar to the injuries from pests or pathogens (Shumway and Scott 2012; UW Agronomy). For example, cupped leaves in soybeans, a symptom of injury from auxinic herbicides such as 2,4-‐D and dicamba, can also be caused by Soybean mosaic virus, bean pod mottle virus and alfalfa mosaic virus (Legleiter et al. 2012). Similarly, herbicide drift causes injuries to tomato like those from pathogen damage: “Cucumber mosaic virus and herbicide injury are almost identical. Cucumber mosaic virus causes tomato plants to yellow and become bushy and stunted. Leaves may be mottled.”(Edmunds and Pottorff 2009). As explained in detail, crop injury from herbicide use is a significant issue associated with the increased use of over-‐the-‐top applications of herbicides accompanying the cultivation of the FG72 soybean system. In the PPRA, then, APHIS needs to consider – as a plant pest risk – the injury to non-‐target plants from increased herbicide use and different patterns of herbicide use as part of the FG72 soybean system, and ways to prevent such injury. f. Herbicides can directly and indirectly affect pests and pathogens of non-‐target plants Herbicides can have direct effects on plant pathogens, either stimulating or suppressing the growth of particular bacteria and fungi (Duke et al. 2007; Sanyal and Shrestha 2008). Indirect effects on plant diseases are also common, and involve a variety of mechanisms: “Another potential indirect effect is alteration of plant metabolism or physiology in a way that makes it more susceptible or resistant to plant pathogens. For example, induction of higher levels of root exudate (e.g., Liu et al., 1997) or altered mineral nutrition (proposed by Neumann et al., 2006).” (Duke et al. 2007).
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a four-fold rise - Center for Food Safety

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