Resistance to agricultural fungicides has increaséd dramatically in the past twenty years, following the introduction of systemic fungicides. Disease control failures associated with fungicide resistance have occurred with many classes of fungicides and in many genera of plant-pathogenic fungi. In some cases, resistance evolved extremely rapidly making the chemicals ineffective for disease control only a few years after they were introduced.

The rapid development of resistance to systemic fungicides has led to efforts to develop strategies to avoid or delay the evolution of fungicide resistance in plant pathogen populations. Despite a widespread interest in managing fungicide resistance, very few experimental studies have been performed to elucidate the important factors controlling resistance development. Most fungicide resistance studies have consisted of anecdotal field observations which have rarely been followed up with experimentation. In order to understand what factors affect the evolution of resistance, and to use this information to design effective resistance management strategies, more experimental studies are required.

Plant growth regulators paclobutrazol and flurprimidol were evaluated for suppression of Poa annua spp. reptans, a perennial biotype of annual bluegrass, in a creeping bentgrass green. Paclobutrazol at 0.6 kg ai/ha applied on Mar. 15, followed by 0.3 kg/ha on Apr. 29, 0.6 kg/ha on Oct. 1, and 0.3 kg/ha on Nov. 12 for each of 2 yr suppressed P. annua spp. reptans 28% approximately 4 mo after the final treatment. When paclobutrazol was applied at 0.3 kg/ha in each of four applications during the same period, suppression was similar to that with the higher rate 1 and 2 mo after final treatment but declined to 7% by 4 mo. Suppression of P. annua spp. reptans from flurprimidol applied four times during each of 2 yr was 22 to 27% 1 mo after final treatment but no suppression was noted 2 mo after the final treatment. Maximum creeping bentgrass injury was less than 20% when either paclobutrazol or flurprimidol was applied in the spring. However, creeping bentgrass injury was approximately 30% in the fall when either chemical was applied in the spring and repeated in October at 0.6 kg/ha.

Standard operating procedures (SOPs) were developed for repetitive field research tasks to help ensure that instructions were complete and to provide consistency and continuity in the senior author's field research program. SOPs are explicit step-by-step instructions for carrying out experimental tasks that are components of experimental plans. SOPs are not the same as protocols for unique, new experimental plans. However, protocols may incorporate sequences of SOPs, if desired. SOPs are most useful for new workers and when research tasks need to be repeated infrequently in time (e.g., once every 6 mo or less per year). SOPs may help researchers enhance data accuracy, precision, and reproducibility as part of their own statistical quality control procedures. The authors' field-tested SOPs are available on diskette for critical review, modification, and use by interested weed scientists.

Leafy spurge is a troublesome, exotic weed in the northern Great Plains of the United States. Leafy spurge produces showy yellow bracts during June that give this weed a conspicuous appearance. A study was conducted to determine the feasibility of using remote sensing techniques to detect leafy spurge in this phenological stage. Study sites were located in North Dakota and Montana. Plant canopy reflectance measurements showed that leafy spurge had higher visible (0.63- to 0.69-μm) reflectance than several associated plant species. The conspicuous yellow bracts of leafy spurge gave it distinct yellow-green and pink images on conventional color and color-infrared aerial photographs, respectively. Leafy spurge also could be distinguished on conventional color video imagery where it had a golden yellow image response. Quantitative data obtained from digitized video images showed that leafy spurge had statistically different digital values from those of associated vegetation and soil. Computer analyses of video images showed/that light reflected from leafy spurge populations could be quantified from associated vegetation. This technique permits area estimates of leafy spurge populations. Large format conventional color photographs of Theodore Roosevelt National Park near Medora, ND were digitized and integrated with a geographic information system to produce a map of leafy spurge populations within the park that can be useful to monitor the spread or decline of leafy spurge.

Field studies were conducted from 1991 to 1994 to investigate the effectiveness of reduced rates of bentazon in tank-mixtures with imazethapyr, thifensulfuron, or HOE 075032 for improved control of redroot pigweed and common lambsquarters in navy bean. Tank-mixtures of bentazon at 600 g ai/ha plus imazethapyr at 25 g/ha or HOE 075032 at 5 to 15 g/ha controlled both redroot pigweed and common lambsquarters. These rates represent an approximate 45% reduction in total amount of active ingredient needed to control these weeds compared with full label rates. Bentazon tank-mixtures with 2 or 4 g/ha of thifensulfuron controlled these weeds but caused severe injury and delayed crop maturity. In greenhouse studies, the GR25 for HOE 075032 in navy bean was > 90 g/ha, while in soybean it was 16 to 24 g/ha.

The first significant cases of herbicide-resistant weed populations were to the triazines in the 1970s. In the last 10 years there has been an increase in the number of weed populations that have become resistant to an array of herbicides. In some of these cases, like rigid ryegrass in Australia, a multitude of resistant biotypes has evolved with different mechanisms of resistance. If the present trend continues, the number of herbicides effective on certain weed species may diminish rapidly. To counteract this trend, industry has organized a number of intercompany working groups to specifically address the development of resistance and to implement plans to manage resistance. University and extension along with industry personnel across the world have begun educating growers on resistance management. However, this effort needs to be intensified to find new solutions for controlling weeds through the use of integrated weed management practices that incorporate new and established herbicides with cultural, mechanical, and biological control methods. The challenge is to develop cost effective, environmentally sustainable programs for weed control while maintaining the present efficiency in food and fiber production so that needs of an ever expanding human population can be met.

In 1753, Carolus Linnaeus described tansy ragwort, Senecio jacobaea, in Species Plantarum. This species is a member of the largest genus of the sunflower family (Asteraceae), which encompasses 1300 genera and 21 000 species worldwide. Taxa in the genus Senecio L. range from herbs to shrubs and occur globally. Comparatively few senecios are of economic importance and many of them are weeds, among them tansy ragwort, which can infest pastures, crowding out more desirable forage and poisoning grazing livestock.

Experiments were conducted near Scottsbluff, NE in 1991 and 1992 to evaluate the selectivity of imazethapyr for weed control in blue grama, intermediate wheatgrass, little bluestem, Russian wildrye, switchgrass, and western wheatgrass. Imazethapyr reduced weed biomass in all seedings and injured all perennial grasses 12 days after treatment (DAT). Imazethapyr reduced the height of intermediate wheatgrass, Russian wildrye, and switchgrass 35 DAT. Russian wildrye, and switchgrass biomass 50 DAT was reduced by imazethapyr. Weed biomass in new seedings of intermediate wheatgrass and western wheatgrass were reduced more than that of the other grasses.

Seeds of suspected herbicide-resistant Palmer amaranth and common waterhemp were collected in Clay County and Douglas County, KS, respectively. An experiment was established in a greenhouse to determine if these species had developed resistance to imazethapyr and thifensulfuron. Imazethapyr was applied pre- (PRE) and postemergence (POST) at 1×, 2×, 4×, and 8× the suggested use rate (70 g/ha), and thifensulfuron was applied POST at 1×, 2×, 4×, and 8× the suggested use rate (4.5 g/ha). Both species had developed resistance to all rates of these herbicides. The occurrence of resistance at the Clay County site (Palmer amaranth) fit the typical pattern for the development of herbicide resistance, i.e., multiple applications of the same class of herbicide for several years. However, the Douglas County (common waterhemp) site had a limited history of use of ALS-inhibiting herbicides and did not follow typical models of resistance development.

Morocco has a large number of edible weeds, but seventeen are mostly eaten by the population, collected for sale in different provinces, or even exported. Eight weeds have edible shoots while the others have edible stems, fruits, roots, flowers, or petioles. Thirteen weed species are marketed either seasonally or throughout the year and generate money for the people. Morocco's tassel grapehyacinth bulbs and products extracted from pennyroyal mint are exported. Further research should focus on the nutritive value of these weeds and their economic role in the country.

In 1753 Linneaus named the genus Potentilla in his Species Plantarum. The common name five finger is used frequently for this group of plants. The genus, in the rose family (Rosaceae), is composed of about 500 north temperate species (50 in North America, 75 European species) of mostly boreal herbs and shrubs. Indeed, Potentilla extends far into arctic regions. However, a few species are south temperate. And although less common, some species are also found in alpine and high mountain regions of the tropics and South America; P. anserinoides Lehm. is a New Zealand native.

The Weed Society of America (WSA) was organized in 1954. At that time, 114 scientists were identified as conducting research on weeds and their control, although only part of these scientists' time was devoted to weeds. Although “selective” herbicides were used in the late 1800s and the “sinox” or “dinitro” herbicides were fairly important from the 1930s, the discovery of the broadleaf selective phenoxy herbicides in the 1940s gave scientists and farmers an exciting new way to manage weeds and played a major role in advancing the notion that there was a need for a separate discipline of weed science. It was noted by C. J. Willard in 1954 at an address to the American Society of Agronomy (ASA) that there was an urgent need for research on weed biology and ecology and on the behavior of herbicides in plants and soils. WSA held its first meeting in January, 1956. There were 621 charter members of WSA.

Yellow mignonette (Reseda lutea (L.) # RESLU) is a broadleaf perennial weed that is native to the Mediterranean Basin and Asia Minor. It has been spread around the world and is widely recognized in Australia as a troublesome noxious weed in croplands. It is a problem in cropland and pastures because of its high seed output, extensive reproductive root system, ability to thrive under disturbed conditions, and high nitrate levels. While nitrate levels of 2.5 to 3.1% have been detected in plants during the rosette to early flower growth stages, when yellow mignonette is most palatable, no livestock injury or deaths have been reported. Yellow mignonette was first reported in Montana in 1958 but was not recognized as a weed problem until 1990. Since 1988 it has invaded several hundred hectares of small grains and alfalfa (Medicago sativa L.)-grass pastures in Central Montana and is spreading rapidly along gravel road shoulders.

The spread of noxious weeds on rangeland and forests in the United States has been described as a raging biological wildfire. This analogy applies to aspects of spread, impact, and control of weeds. Patterns and means of spread are similar. Noxious weeds and wildfires can dramatically change natural plant communities, alter distribution and species composition of wildlife populations, damage watersheds and increase soil erosion, and adversely affect recreation and aesthetic values. Wildfire management involves prevention, early detection, timely control, and site rehabilitation; elements which are also the foundation of sound weed management. Principles and practices associated with wildfire suppression can be used to illustrate many weed science fundamentals, and to improve weed management programs. Federal land management agencies are directed to train employees in effective weed management and to increase public awareness about noxious weeds. Most agency employees are familiar with wildfire management; knowledge which could be useful in teaching weed management principles. Fire prevention could serve as a model to promote greater public awareness of the impact of noxious weeds and the need for weed prevention and early detection.

This paper describes the planning, designing, constructing, and initial operating phases of a state-of-the-art agricultural pesticide facility (APF). The APF on the University of Minnesota, St. Paul Campus is located within a major metropolitan area, causing environmental and human safety to be priority considerations. The building site was located adjacent to a greenhouse complex and field plots to provide access for all users of pesticides on the St. Paul Campus for storing, measuring, packaging for off campus use, applying, and disposing of pesticides. This central facility eliminated the need for about 25 generally inadequate locations on campus where pesticides were previously stored and handled. Changing state and federal pesticide regulations and in-house operating requirements may require future modification and retrofitting of the APF. However, the APF is a valuable research and education addition to the St. Paul Campus, and it has provided greater safety for personnel, students, visitors, the community, and the environment.

Literature concerning interactions between herbicides and insects is reviewed. Herbicides can be toxic to insects or can affect them indirectly, such as by destroying food supplies, but they usually can be used with proper application timing without affecting insects adversely. Herbicides and biocontrol insects can interact either favorably or unfavorably depending on the life cycle stage of weed and insect, effect on predatory insects, changes in food quality, mobility of the biocontrol insect, and impact of herbicides on weed growth. Thus, interactions between a biocontrol insect and herbicide can be antagonistic, additive, complementary, or synergistic. Split-plot techniques to evaluate these interactions at an early stage of insect establishment are proposed to improve weed biocontrol.