Experiments were conducted to evaluate the effect of a 2.5-cm simulated rainfall 0.05, 0.25, 0.5,1, 3, 6, and 24 h after POST applications of AC 263,222 to sicklepod. Fresh weight reductions were directly related to increasing AC 263,222 rates and rain-free intervals. Fresh weight reductions with 9, 18, 36, 54, and 72 g ai/ha AC 263,222 were 32, 47, 55, 59, and 67%, respectively, with the rain-free treatment. A simulated rainfall 0.05 h after POST application lowered fresh weight reductions with 9, 18, 36, 54, and 72 g/ha AC 263,222 to 5, 7, 19, 23, and 28%, respectively, of the untreated control. As AC 263,222 rates increased, a simulated rainfall shortly after POST application was less detrimental. At 18 g/ha of AC 263,222, a 3-h rain-free interval was necessary for fresh weight reductions equivalent to the rain-free control. As the rate of AC 263,222 increased to 54 g/ha, the rain-free interval for fresh weight reductions equivalent to the rain-free control was reduced to 1 h. Radiolabeled studies indicated that at 3 h after application an equivalent amount of 14C was accumulated in the plant as compared with the rain-free control. The correlation coefficients for fresh weight reductions and 14C in the plant were r = 0.53, 0.75, 0.68, 0.74, and 0.70 at rates of 9, 18, 36, 54, and 72 g/ha AC 263,222, respectively.

Given that the Weed Science Society of America's (WSSA's) long-term objectives may include increasing the level of public funding in weed science, WSSA needs to make its case successfully in the policy arena. A strategy to influence policy in Washington should include: identifying specific goals to be achieved in a reasonable time frame; building the case for increased funding, including supporting arguments and materials; identifying the key players that can affect the policy discussion; and knowing what positions those key players currently hold. The 1995 Farm Bill may be a potential window of opportunity to affect changes in agricultural policy with regard to weed science. The next two years are an appropriate time to implement whatever strategy is developed.

The first weed scientists were under great pressure to solve weed problems and when the magic of chemical technology appeared they seized it to replace human and animal energy for weeding. Today, weed scientists are striving for a reasonable accommodation between a productive and protected environment. Many weed scientists now believe that management, not control, should dominate weed science. Full integration of weed science into future agricultural systems requires that its practitioners make the quality and quantity of food produced equivalent goals.

The relative sensitivity of various crops and weeds to celery root residue incorporated into soil was determined in greenhouse experiments. A range of concentrations was used to determine the percentage of celery residue needed to cause a 50% reduction in plant growth (I50). The most sensitive weed was spiny amaranth and the least sensitive was common purslane. The most sensitive crop was radish and the least sensitive was celery. Selectivity was calculated as crop I50/weed I50 and varied from a maximum of 13 for celery and spiny amaranth to a low of 0.4 for radish and common purslane. Selective weed suppression might be obtained when celery residue is present.

In 1991 and 1993, tolerance of ‘Zenith’ and ‘Merit’ sweet corn to 35 g ai/ha nicosulfuron post-directed (PDIR) 0, 5, 10, and 15 cm up the corn stalk or applied POST was determined. In 1991, nicosulfuron applied POST to Zenith caused approximately 30% visible injury, 30% height reduction, and 50% reduction of U.S. No. 1 marketable ear weight. In 1991 no visible injury was observed in the PDIR treatments. Zenith was not injured by any treatment in 1993. Both years, Merit was killed by nicosulfuron applied POST. In 1991 and 1993, nicosulfuron PDIR 0 and 5 cm up the corn stalk of Merit caused approximately 5% and 65% visible injury, respectively, and resulted in yield loss. PDIR application increased nicosulfuron tolerance of moderately tolerant Zenith but did not improve that of least tolerant Merit.

The purpose of my presentation is to demonstrate the impact that weeds have on man and the U.S. economy. My approach will be to introduce the concept of weed impacts. What do I mean when I reference weeds and the effects that they have on man and his activities? Second, what are the sectors of the U.S. economy that are impacted by weeds? Third, I will illustrate the types of impacts that weeds have on various sectors of the economy and I will categorize these impacts so that they become meaningful. Last, I will discuss the economics of weed management, covering indexes of weed management inputs over time and discuss the relative value of various weed management tactics.

Scientists, above all others, approach public policy believing it to be scientifically rational—as it has been portrayed by the Good Government Movement, the League of Women Voters, and Mark Twain. Today, the problem is that public policy does not appear rational to scientists. While there is great opportunity for scientific input, neither the policy process nor the most influential policy input is necessarily scientifically rational. To understand the relationship of science to policy, one has to look at how the public views science today, the style of policy, the style of science, and how the policy process may have been captured by “irrational” interests. Only then can a realistic marriage be made between science and policy.

Mixtures of herbicides have been proposed as strategies to prevent or delay the evolution of resistance to the resistance-prone sulfonylurea and imidazolinone herbicides that inhibit acetolactate synthase. These herbicides have become or are becoming widely used in soybean, wheat, rice, and other major crops. For a mixture to be efficacious in preventing resistance, the less resistance-prone component(s) should have the following traits compared to the vulnerable herbicide: a) control the same spectra of weeds; b) have the same persistence; c) have a different target site; d) be degraded in a different manner; and e) preferably exert negative cross-resistance. We compared the proposed mixing partners for use with several widely used acetolactate synthase inhibiting herbicides to these criteria and found that: a) all have somewhat different weed spectra; e.g. none control common cocklebur as well as imazaquin or imazethapyr in soybean, or kochia as well as chlorsulfuron in winter wheat; b) all are far less persistent than these vulnerable herbicides. Less persistent sulfonylureas are now on the market but are in limited use. Late in the season, the mixing partner is not present while the vulnerable herbicide remains active; c) most have different target sites; d) in soybean most mixing partners are degraded differently than vulnerable herbicides. In wheat virtually all herbicides used without safeners are degraded by monooxygenases, thus it is impossible to meet this criterion in this crop; e) none of the mixing partners exert negative cross-resistance. The present mixtures may have superior or more cost-effective weed control properties than the acetolactate synthase inhibitors used alone, but they do not meet all the criteria for resistance management. Not meeting the key criteria of identical control spectra and equal persistence aggravates future resistance problems, as has happened with insecticides.

For this presentation we would like to discuss some history of weeds and their control, the evolution of weed science, the development of herbicides and the changing dynamics of weed science research. As mentioned by previous speakers, weeds cause great loss to almost every crop production enterprise in the United States and around the world. Man has sought to control weeds by various methods including cultural practices, cultivation, hoeing, and with herbicides. Pioneer weed scientists were individuals trained in the areas of physiology, botany, and agronomy. They applied their knowledge and training to the understanding of growth, development, and control of weeds in the late 1800's and early 1900's.

Science shapes and is shaped by policy decisions. Yet scientists seem to have the greatest difficulty engaging in the policymaking process. When Congress makes public policy it does not work in a vacuum. It is responsive to public pressure. Interest groups that are effective at influencing policy know how Congress works, what are its rules, and who are the players. There is a need for scientists to engage in the process. Several important issues on the agenda involve weed science. There are a number of actions the weed science community can take to make itself available and helpful to policy makers.

Weed scientists regularly attend conferences, symposiums, and workshops to communicate with colleagues about their current weed research programs. Communication of research can be hindered by poor visual aids. Computer programs, film recorders, and color printers have greatly increased the ease of visual aid production but have also increased the opportunity to prepare incomprehensible presentations. The size of the text, the amount of information presented, and the contrast between the text color and background color are the most important factors that affect the legibility of visual aids. Text, tables, and graphs should be short, simple, and legible. Computers and film recorders are not essential to produce good visual aids. The greatest assets in the production of visual aids are common sense, familiarity with the production equipment, sufficient preparation time, and critical assessment of the visual aids well in advance of the presentation date.

Concerns in the public and agricultural sectors about the impacts of agricultural practices have led many weed scientists to refocus research efforts toward development of alternative strategies of weed management. To develop methods of weed management that will supplement or replace herbicides, the impacts of agricultural practices on weeds must be better understood. With a foundation of knowledge in basic weed biology, alternatives to herbicides can be made available in the future.

The Environmental Protection Agency (EPA) is required by law to assure that the use of pesticides does not cause unreasonable risks to humans or the environment when risks are compared with benefits. Weed scientists conduct hundreds of comparative efficacy tests each year, but the results are often of little use to the Agency in benefit assessments because the tests are unpublished or otherwise unavailable to the Agency, the tests are conducted in a manner unusable for regulatory purposes, or there are inconsistencies between tests conducted year to year or at different sites. Despite the lack of high quality data, the Agency is compelled to make the best regulatory decision possible with the information at hand, and it may appear to some that decisions are based more on policy than science. EPA is looking for experimental methods that will improve the quality of benefits data available to the Agency.

Weed science has a long history of solving weed management problems for farmers. Over the last four decades most of the solutions to weed problems have been based on herbicide technology. Thus, most crop production systems in the United States rely heavily on herbicides as the primary method of weed management. During the last decade environmentalists, farmers, agricultural scientists, policy makers, and the general public have begun to question the long-term sustainability of conventional farming systems. The sustainability of these systems is being questioned because of environmental, social, and economic concerns caused by global competition, cost of production, soil erosion, water pollution, and concern over the quality of rural life. Weeds are the major deterrent to the development of more sustainable agriculture systems. Since weeds dictate most of the crop production practices (e.g., tillage, herbicides, cultivation, row spacing) weed scientists must become the leaders of collaborative integrated approaches to agriculture systems research. New crop production systems must be developed that are less destructive to the environment, are profitable, conserve energy, and support rural community development. The goal is to facilitate the development of ecologically based alternative methods of weed management that will support crop production systems that require less tillage and herbicide inputs. To accomplish this goal, research efforts must be radically expanded in weed/crop ecology and in the development of ecologically based technologies for weed management.

Worldwide, 10 genera and 400 species comprise the Hypericaceae, the St. Johnswort Family. The genus Hypericum, with 350 of these species (11), includes evergreen or deciduous shrubs, subshrubs, and herbaceous perennials. The hypericums have simple, opposite or whorled leaves and usually golden-yellow many-stamened flowers.

Common St. Johnswort (Hypericum perforatum L.) is a hairless perennial, reproducing by seeds and by runners from the base of the stem. It grows 20 to 100 cm tall, with spreading branches and small deep green glabrous oblong-ovate leaves, perforated by many translucent glandular dots. Branched clusters of golden yellow flowers with tiny black spots are produced from May to August (14).

Phytolaccaceae, virtually a tropical family, encompasses from 15 to 18 genera (11), usually herbs, but also a few tropical trees and shrubs (13). Of the 25 species in the genus Phytolacca (11), only one is represented in eastern North America (1).

During 1992, the Research Committee of the Weed Science Society of America (WSSA) prepared a list of research needs for the discipline of weed science. The identified needs fit well with the recommendations of the Future Directions for Weed Science Symposium held in Washington D.C. on April 15, 1993, thus are provided as a supplement to the Symposium publication. The Research Committee concluded weed science research should focus on increasing knowledge related to the economic and biological impact of weeds across a wide variety of environments (crop production, forestry, right-of-way and aquatic). An increased understanding of the biology, ecology and genetics of weeds is needed to optimize their management. Research on control of weeds with biological agents and natural products should be conducted with emphasis on optimizing performance in the field environment. The development of weed populations resistant to chemical and biological control agents should be studied so the occurrence of such populations can be minimized. Because herbicides will continue to be the primary basis of weed management for the foreseeable future, research is needed to optimize herbicide application technology and to minimize their impact on the environment, particularly related to surface and groundwater contamination. Finally, new and reliable methods to detect herbicide residues in water, soil and vegetation are needed.