<p style="text-align: justify;"><b>Field Testing</b></p>

<p style="text-align: justify;">Field testing has demonstrated that CBH-351 maize plants are well protected from European corn borer and exhibit tolerance to glufosinate ammonium herbicides at concentrations that provide effective weed control. CBH-351 maize has undergone field testing in a wide variety of locations, in 31 States and territories of the United States since 1995, and in Canada, Belgium, France, Chile and Argentina. This field testing was conducted, in part, to confirm that CBH-351 maize exhibits the desired agronomic characteristics and to demonstrate that CBH-351 maize did not pose a plant pest risk. The kernel composition, quality and other characteristics of CBH-351 maize were found to be similar to non-transgenic maize and should have no adverse impact on raw or processed agricultural commodities.</p>

<p style="text-align: justify;"><b>Outcrossing</b></p>

<p style="text-align: justify;">Since pollen production and viability were unchanged by the genetic modification resulting in CBH-351, pollen dispersal by wind and outcrossing frequency should be no different than for other maize varieties. Gene exchange between CBH-351 maize and other cultivated maize varieties will be similar to that which occurs naturally between cultivated maize varieties at the present time. In North America, where there are few plant species closely-related to maize in the wild, the risk of gene flow to other species appears remote. Cultivated maize, or maize, <i>Zea mays</i> L. subsp. mays, is sexually compatible with other members of the genus Zea, and to a much lesser degree with members of the genus Tripsacum.</p>

<p style="text-align: justify;">Wild diploid and tetraploid members of Zea collectively referred to as teosinte are normally confined to Mexico, Guatemala, and Nicaragua; however, a fairly rare, sparsely dispersed feral population of teosinte has been reported in Florida. All teosinte members can be crossed with cultivated maize to produce fertile F1 hybrids. Nonetheless, in the wild, introgressive hybridization from maize to teosinte is currently limited, in part, by several factors including distribution, genetic incompatibility, differences in flowering time, developmental morphology, dissemination, and dormancy. First-generation hybrids are generally less fit for survival and dissemination in the wild, and show substantially reduced reproductive capacity which acts as a significant constraint on introgression.</p>

<p style="text-align: justify;">In Central America, many of these species occur where maize might be cultivated, however, gene introgression from CBH-351 maize under natural conditions is highly unlikely. It is further unlikely that potential introgression of European corn borer resistance or glufosinate tolerance traits from CBH-351 maize would cause teosinte to become more weedy in the absence of glufosinate herbicide selection.</p>

<p style="text-align: justify;">The genus Tripsacum contains up to 16 recognized species, most of which are native to Mexico, Central and South America, but three of which exist as wild and/or cultivated species in the U.S. Hybrids of Tripsacum species with Zea are difficult to obtain outside of a laboratory and are often sterile or have greatly reduced fertility, and none are able to withstand even the mildest winters. Furthermore, none of the sexually compatible relatives of maize in the U.S. are considered to be weeds in the U.S. therefore it is unlikely that introgression of the bar gene would provide a selective advantage to these populations as they would not be routinely subject to herbicide treatments.</p>

<p style="text-align: justify;"><br />
<b>Weediness Potential</b></p>

<p style="text-align: justify;">No competitive advantage was conferred to CHB-531 maize, other than that conferred by resistance to European corn borer and herbicide tolerance to glufosinate. Maize is not a weed, and resistance to European corn borer or herbicide tolerance will not render maize weedy or invasive of natural habitats since none of the reproductive or growth characteristics were modified. Potential introgression from CBH-351 maize into wild relatives is not likely to increase the weediness potential of any resulting progeny nor adversely effect genetic diversity of related plants any more than would introgression from traditional maize hybrids.</p>

<p style="text-align: justify;">Cultivated maize is unlikely to establish in non-cropped habitats and there have been no reports of maize surviving as a weed. Maize volunteers are not uncommon but are easily controlled by mechanical or by using herbicides that are not based on glufosinate as appropriate. <i>Zea mays</i> is not invasive and is a weak competitor with very limited seed dispersal.</p>

<p style="text-align: justify;"><b>Secondary and Non-Target Adverse Effects</b></p>

<p style="text-align: justify;">The history of use and literature suggest that the bacterial Bt protein is not toxic to humans, other vertebrates, and beneficial insects. This protein is active only against specific lepidopteran insects and no lepidopteran species are listed as threatened or endangered species in North America. The Cry9C toxin is also toxic against other Lepidoptera, including members of the families Pyralidae, Plutellidae, Sphingidae, and Noctuidae.</p>

<p style="text-align: justify;">Studies were conductive on several nontarget organisms to determine the potential toxic effects of Cry9C protein on test organisms including adult honeybees, a predator ladybird beetle (<i>H. convergens</i>), juveniles of the soil-dwelling invertebrate Collembola (springtails) (<i>Folsomia candida</i>), earthworms, juveniles of the freshwater invertebrate Daphnia magna, Northern bobwhite chicks, and mice. The Cry9C was expressed in either whole plant powder or pollen derived from CBH-351 maize plants; or as purified from a Cry-minus B.t. bacterial strain engineered to express the protein toxin. Control maize plant powder and pollen test substances lacking insecticidal activity (as assayed against the European corn borer) were used in these studies to determine whether effects were specific to the CBH-351 transformation event. No effects on these organisms were detected during any of these studies that could be related to the presence of the insecticidal Cry9C protein in CBH-351 maize.</p>

<p style="text-align: justify;">Small scale field studies conducted in 1996 in Johnston, Iowa demonstrated that the number of predators observed on plots planted to either CBH-351 maize or a non-transformed counterpart did not show a significantly different pattern among plots. In addition, the diversity of predators observed in both types of plots was equal.</p>

<p style="text-align: justify;">In summary, it was concluded that cultivation of CBH-351 maize should not have a significant potential to harm nontarget and beneficial organisms common to agricultural ecosystems, nor should it significantly impact species recognized as threatened or endangered.</p>

<p style="text-align: justify;"><b>Impact on Biodiversity</b></p>

<p style="text-align: justify;">CBH-351 maize has no novel phenotypic characteristics that would extend its use beyond the current geographic range of maize production. Since the risk of outcrossing with wild relatives in North America is remote, it was determined that the risk of transferring genetic traits from CBH-351 maize to species in unmanaged environments was insignificant.</p>

<p style="text-align: justify;">CBH-351 maize plants are not likely to eliminate the use of chemical insecticides which are traditionally applied to about 25 to 35% of the total maize acreage planted, since the primary target for most of these applications has been the coleopteran, corn rootworm. CBH-351 maize may positively impact current agricultural practices used for insect control by 1) offering an alternative method for control of European corn borer (and potentially other Cry9C-susceptible pests of maize); 2) reducing the use of insecticides to control European corn borer and the resulting potential adverse effects of such insecticides on beneficial insects, farm worker safety, and ground water contamination; and 3) offering a new tool for managing insects that have become resistant to other insecticides currently used or expressed in maize, including other Bt-based insecticides.</p>

<p style="text-align: justify;">CBH-351 maize exhibits tolerance to glufosinate ammonium herbicides at concentrations that provide effective weed control and excellent crop safety. CBH-351 maize, along with glufosinate ammonium herbicides, is expected to positively impact current agricultural practices used for weed control by 1) offering growers a broad spectrum, post-emergent weed control system; 2) providing the opportunity to continue to move away from pre-emergent and residually active herbicides; 3) providing a new herbicidal mode of action in maize that allows for improved management of weeds which have developed resistance to herbicides with different modes of action; and 4) decreasing cultivation needs and increasing the amount of no-till acres. Volunteers of CBH-351 can be easily controlled by selective mechanical or manual weed removal or by the use of herbicides with active ingredients other than glufosinate ammonium.</p>

<p style="text-align: justify;"><b>Other Considerations</b></p>

<p style="text-align: justify;">In order to prolong the effectiveness of plant-expressed Bt toxins, and the microbial spray formulations of these same toxins, regulatory authorities in Canada and U.S. have required developers to implement specific Insect Resistant Management (IRM) Programs. These programs are mandatory for all transgenic Bt-expressing plants, including CBH-351 maize, and require that growers plant a certain percentage of their acreage to non-transgenic varieties in order to reduce the potential for selecting Bt-resistant insect populations. Details on the specific design and requirements of individual IRM programs are published by the relevant regulatory authority.</p>
