The arguments for and against placing a symbol containing a letter to denote the mode of action on herbicide labels in Europe are reviewed. There is no clear view within and between the organizations that may influence the decision. However, it is generally accepted that such an initiative only should be part of an integrated approach to prevent the development of herbicide resistance in weeds.

Large crabgrass is a problem weed in horticultural crops, particularly in turfgrass in the southeastern United States. If growth of large crabgrass could be suppressed via soil pH or calcium levels, control of this weed in turfgrass might be improved while minimizing herbicide usage. To determine the effect of soil calcium and pH on germination and growth of large crabgrass, seeds were sown in a loamy sand soil amended with calcium carbonate (CaCO3) or magnesium carbonate (MgCO3) that established a range of soil pH from 4.8 to 7.8. Seeds were also sown in soil amended similarly with calcium sulfate (CaSO4), which does not affect pH, that established a range of exchangeable Ca levels corresponding to the Ca range in CaCO3 from pH 4.8 to 7.8. Seed germination of large crabgrass was unaffected by pH when soil was amended with CaCO3, whereas seed germination decreased with increasing pH when soil was amended with MgCO3. Crabgrass germination was not affected by Ca (CaSO4) independent of pH changes. Increasing soil pH reduced shoot and root dry weights of seedlings regardless of material used to raise pH. Maximum shoot dry weights occurred at pH 4.8 in the unamended soil, whereas maximum root dry weights occurred at ranges from pH 5.8 to 6.3 for CaCO3 and pH 5.3 to 5.8 for MgCO3. Shoot and root dry weights were not affected by Ca when soil was amended with CaSO4. By raising soil pH levels, the growth of large crabgrass and its ability to compete with turfgrass may be reduced. Raising exchangeable Ca does not appear to be an effective management tool for control of this weed species.

Industry, public-sector researchers and extension agents, and growers were surveyed in 1998 to determine their perspectives on how labeling herbicides with their site of action (group number) would affect the herbicide use practices of growers. The crop protection industry in Canada represented by the Crop Protection Institute (CPI) generally supports herbicide resistance labeling but has some concerns regarding the wording of the labels, including the identification symbol. Most researchers and extension agents believe that labeling herbicides with their site of action will facilitate herbicide group rotation by growers who frequently use herbicides from the same group. Of the two-thirds of the 126 surveyed growers who were familiar with herbicide groupings, 58% practiced herbicide group rotation. Those who did not tended to lack understanding of the basis and purpose of herbicide classification. Grower responses were similar to those from the research and extension community, although only 29% of the growers who currently do not rotate herbicides from different groups believed that resistance management labeling would influence them.

Herbicides from several chemical families were evaluated in the greenhouse for preemergence control of perennial weed species emerging from seeds. Weed species were bermudagrass, johnsongrass, Canada thistle, common milkweed, common pokeweed, hemp dogbane, and horsenettle. Atrazine, cloransulam, chlorimuron, clomazone, flumetsulam, imazaquin, linuron, metolachlor, metribuzin, pendimethalin, and sulfentrazone were used representing common preemergence herbicide families used in the mid-Atlantic region for corn and soybean in a sandy loam soil. Hemp dogbane and common pokeweed were controlled (greater than 85%) by eight of the 11 herbicides in this study, indicating they may be the two most susceptible species in the trial. Metolachlor and pendimethalin provided control of only bermudagrass, and linuron controlled only Canada thistle. Cloransulam controlled all species except bermudagrass. Clomazone provided greater than 80% control of all species except horsenettle. Metribuzin alone or in combination with chlorimuron provided the broadest spectrum and highest level of control. Metribuzin provided greater than 85% control of all species except johnsongrass. Soil-applied herbicides can limit the establishment of perennial species from seeds.

One of the most consistent recommendations, from both the private and public sectors, for the prevention and management of herbicide-resistant weeds is to rotate herbicides with different sites of action. Therefore, it is imperative that those who make herbicide recommendations and those who apply herbicides know which herbicides have the same or different sites of action. An herbicide's site of action is not obvious from its trade, common, or chemical name, and it is not possible to determine from the label if it has the same site of action as another herbicide.

The North American Herbicide Resistance Working Group (NAHRWG), an organization to facilitate the effective management of herbicide resistance by fostering understanding among manufacturers and distributors, academics, consultants, government, and end users requested I speak with you on the legal ramifications of placing resistance information on the herbicide label. As an Assistant General Counsel for Regulatory Affairs with Monsanto Company, my practice is devoted to agricultural biotechnology, crop chemical regulatory matters, and to a large extent, the proper stewardship of Monsanto's agricultural products.

The genus Bromus in the Poaceae includes 100 species of annuals, biennials, and perennials. Several species are important as forage crops while others are grown as ornamentals. It is distributed in the temperate areas and in tropical mountainous regions (Hyam and Parkhurst 1995). Bromus tectorum L., downy brome, an introduced annual, occurs throughout most of the U.S., Canada, and northern Mexico (Sheley and Petroff 1999). It was introduced to North America from Europe before 1861. Downy brome has a dual role as a serious weed and as an important forage (Upadhyaya et al. 1986).