Field experiments were conducted at Vegreville and Lacombe, AB, to determine the influence of barley (Hordeum vulgare) variety and seeding rate on interference of wild oat (Avena fatua) with barley. Barley variety and seeding rate affected barley density, height at maturity, and seed yield, as well as wild oat shoot dry weight and seed yield in most experiments, but there was no variety by seeding rate interaction. As expected, the semidwarf varieties Falcon and CDC Earl were the shortest. Barley seedling emergence and subsequent plant densities varied among varieties, locations, and years. The hull-less varieties Falcon and CDC Dawn had the poorest emergence in most cases, whereas AC Lacombe and Seebe had the highest emergence. Wild oat shoot dry matter and seed production was highest in the Falcon, CDC Dawn, and CDC Earl plots, suggesting that these were the least competitive with wild oat. Barley yield loss from wild oat interference also tended to be highest in these varieties. Poor emergence of Falcon and CDC Dawn and the shorter stature of Falcon and CDC Earl likely contributed to their relatively poor competitiveness with wild oat. Increasing the seeding rate improved the competitiveness of all varieties, as evidenced by reduced wild oat shoot dry matter and seed production and, in some cases, improved barley yields.

Diagnosing herbicide-resistant weeds as a first step in resistance management and monitoring their nature, distribution, and abundance demands efficient and effective screening tests. This review summarizes and recommends appropriate seed sampling techniques, protocols for screening weeds for resistance to herbicides of different sites of action, interpretation of results, and information given to the grower. Elements common to all screening procedures are reviewed. Choosing appropriate discriminating doses to distinguish between resistant and susceptible weed biotypes is the most important factor in achieving accurate and consistent results. Interpretation of results is also critical because resistant weeds may comprise a small portion of the population in suspected accessions or biotypes.

Producers in the semiarid Great Plains are including corn (Zea mays) in dryland rotations; however, weed management is difficult because the corn canopy is not competitive with weeds. My objective was to determine if cultural practices can enhance corn's competitiveness with weeds, thus supplementing current weed management strategies. Cultural systems, comprised of different row spacing, plant population, and nitrogen placement, were evaluated for effects on foxtail millet (Setaria italica) growth during three growing seasons. A cultural system comprised of 38-cm row spacing, 47,000 plants/ha, and N banded near the seeds reduced foxtail millet biomass 60% compared with the conventional system of 76-cm row spacing, 37,000 plants/ha, and N broadcast. Narrow rows had the greatest effect on foxtail millet growth. Corn's tolerance to foxtail millet interference also was improved, as yield loss in the system with narrow rows, high population, and banded fertilizer was reduced threefold compared with the conventional system. Integrating cultural systems with rotation design and residue management will further strengthen weed management in semiarid corn production.

Site-specific herbigation using a linear-move irrigation system equipped with an automated irrigation control system was evaluated in a series of field trials conducted at the University of Idaho Aberdeen Research and Extension Center near Aberdeen, ID. In the first study, the experimental area was divided into site-specific management zones that were randomly assigned herbigation treatments of metolachlor at 0, 1.8, 2.7, or 3.6 kg ai/ha. In a second study, site-specific herbigation treatments of metribuzin at 0, 0.28, 0.42, or 0.56 kg ai/ha were applied. The tests covered a range in system flow rate from 29 to 90% of maximum design flow. Average metolachlor rates applied were within 1, 2, and 4% of the target 1.8, 2.7, and 3.6 kg/ha rates, respectively, and average metribuzin rates were on target at the 0.28 kg/ha rate and within 5 and 2% of the 0.42 and 0.56 kg/ha target rates, respectively. In a third study, potato (Solanum tuberosum) fields were divided into management zones, and low, medium, or high populations of Indian mustard (Brassica juncea) and foxtail millet (Setaria italica) were seeded in each zone. Different rates of a metolachlor plus metribuzin mixture were herbigated in each zone—higher rates in zones with high populations and lower rates in zones with low populations. Weed control was excellent in all zones. Results suggest good potential for site-specific herbigation when linear-move or center-pivot irrigation systems are equipped with the automated irrigation control system.

Straight-backed sentinels in high crowned busbies
rise in crowded companies
from river bank and marsh.
Grown old and fluffed with a thousand florets
gone to seed, the heads make fine torches
for skaters on the pond.
(“Cattails,” Prentice and Sargent 1973)

Until recent times, Typha was the sole genus of Typhaceae, the cattail family. Now the family has been extended to include Sparganium, the burreeds. The 15 species of Typha are prevalent and bothersome emergent aquatic weeds with a worldwide distribution (Heywood 1993; Hickman 1993). The genus Typha was erected in 1753 by Carolus Linnaeus in his Genera Plantarum.

Woollyleaf bursage (Ambrosia grayi) is a noxious, rhizomatous perennial with an extensive creeping root system. It is found in the central and southern Great Plains of the U.S. Clopyralid alone or fluroxypyr, picloram, or glyphosate with either 2,4-D or dicamba were applied to woollyleaf bursage at anthesis and 30 d later in three field experiments. With the exception of treatments containing picloram, the effect of application timing was inconsistent. All treatments containing picloram consistently controlled woollyleaf bursage 93% or greater for 9 mo and 74% or greater for 11 mo. Control was poor or inconsistent with all other treatments. Although a rate response was seen with clopyralid, a level higher than 0.28 kg/ha may be necessary to control woollyleaf bursage. After 11 mo, control was less than 60% with treatments containing 1.7 kg/ha of glyphosate in 10 of 12 herbicide treatments and timing combinations over 3 yr.

This study assessed the tolerance of ‘Midlawn’ (Cynodon dactylon × C. transvaalensis) and ‘OKS 91-11’ (C. dactylon) bermudagrass to commonly used postemergence herbicides and compared visual assessment with vehicle-mounted optical sensing (V-MOS) for evaluating herbicide phytotoxicity. Two postemergence herbicides were applied to mature stands of Midlawn and OKS 91-11 at two and four times label rates, and seven postemergence herbicides were applied at standard and two times label rates. Visual evaluation and spectral assessments were made for turf color 2, 7, 14, and 21 d after treatment (DAT). Triclopyr and triclopyr plus clopyralid at 2× and 4× label rates caused significant damage on OKS 91-11 and Midlawn bermudagrass in both July and September experiments. MSMA at 2× rate and MSMA + metribuzin at 1× and 2× rate caused up to 73% color reductions that disappeared within 21 DAT in both cultivars. During July, 2,4-D plus mecoprop plus dicamba at the 2× rate caused at least 18% injury to Midlawn bermudagrass for 21 d. Metribuzin was safe at the 1× rate but caused significant injury for up to 7 d at the 2× rate. Imazaquin and halosulfuron-methyl each caused significant damage on one rating date. Pronamide caused no change in color regardless of rate or time of application. OKS 91-11 tolerated 2× rates of 2,4-D plus mecoprop plus dicamba better than Midlawn, but cultivar responses to other herbicide treatments were similar. V-MOS was effective for measuring green color reduction on bermudagrass turf. V-MOS and visual evaluation were linearly related (P < 0.01) at a strength of r = 0.58. Statistical results obtained using visual rating and V-MOS were the same in 86% of all cases.

Diuron, simazine, and terbacil were applied in field plots annually from 1981 to 1995. Soil was sampled at selected times after herbicide application in 1993, 1994, and 1995 to determine herbicide residue changes with time and soil depth. Diuron residues were found mainly in the upper 20 cm of soil; residue concentration decreased exponentially with time. Less than 1% of the initial concentration after application in summer was present the following spring. Terbacil residues were found in soil below the upper 20 cm. Terbacil degraded more slowly than diuron, and residues in spring were less than 30% the level of the previous summer. Simazine plus hydroxysimazine soil residues were present in all depths to 100 cm and were higher than diuron or terbacil at these depths. Simazine plus hydroxysimazine residues in spring were nearly 40% the level of the previous summer. With all three herbicides, soil residues were greatest in the upper 20 cm of soil during 2 to 3 wk following application. Data confirmed that diuron did not leach, whereas simazine can migrate through the soil. Terbacil migrated intermediately in depth relative to diuron and simazine. After 15 annual applications, herbicide residues were present but were not accumulating.

Leafy spurge (Euphorbia esula) along long distances of railroad right-of-ways is often treated with the least expensive herbicides available that only control top growth. The objective of this research was to evaluate flea beetles, Aphthona nigriscutis and a mixed population of A. czwalinae and A. lacertosa, for establishment and potential to reduce leafy spurge infestations along railroad right-of-ways. In separate experiments, both Aphthona species established the first year following release, and the rate of spread was similar regardless of the initial number released. Aphthona nigriscutis reduced leafy spurge approximately 65% up to 16 m from the release point by 3 to 5 yr after release. The mixed population of A. czwalinae and A. lacertosa reduced leafy spurge density over 95% within 4 yr of release. Biological control is an alternative to chemical control for leafy spurge along railroad right-of-ways, and establishment at these sites could facilitate biological control agent movement into remote areas.

Diuron, simazine, and terbacil were applied together or separately in the field each May from 1981 through 1996. Weed control was over 90% in 1981 and 1982, but by 1984 weeds increased in plots treated with diuron and simazine. Weed abundance was relatively low from 1981 through 1996 in plots treated with terbacil. Broadleaf and grass species abundance was similar in most herbicide-treated plots from 1992 through 1996. Perennial species, particularly fescue (Festuca arundinacea) and ailanthus (Ailanthus altissima), dominated sites treated with diuron and simazine. The weed community changed within 3 yr of the implementation of the weed management program that relied solely on herbicides. A relatively stable weed community persisted from 1992 through 1996. Repeated use of the combined high rate of diuron and low rate of terbacil provided excellent weed control for 15 yr.

A Research Committee was established by the Weed Science Society of America to outline the direction of weed science research during the next decade. Weeds adversely affect humans in both agricultural and nonagricultural environments. It is the opinion of the research committee that weed science will be advantageously positioned for the future if research focuses on research decision processes, weed biology and ecology, weed control and management practices, herbicide resistance, issues related to transgenic plants, environmental issues, and potential benefits of weeds. These future weed science research directions endorse those of the commodity and grower input group Coalition for Research on Plant Systems (CROPS)'99, a U.S. Department of Agriculture (USDA)-supported initiative. The future of weed science is dependent on a joint effort from industry, government regulators, and the public sector consisting of grower groups, as well as USDA, Agriculture and Agri-Food Canada (AAFC), and university researchers. It is our opinion that efforts spent on these research areas will benefit not only growers, commodity groups, homeowners, and industry, but society at large, through the maintenance and improvement of the food and fiber production system, and the environment in North America.

Oxeye daisy (Chrysanthemum leucanthemum L.), a European perennial, was brought to North America as an ornamental. The plant is still grown in decorative gardens and it is one parent of ‘Shasta’ daisy (Holm et al. 1997). Tradition says that the oxeye daisy crept out of Massachusetts Governor Endicott's garden between Tuesdays, and claimed the whole nation in two centuries (Haughton 1978). It also arrived as a contaminant in imported hay and grain seeds (Haughton 1978). Oxeye daisy escaped cultivation and also spread quite readily from agricultural activities to become an aggressive competitor. It often forms thick patches, especially in cattle-grazed areas, reducing hay or forage production (Olson and Wallander 1999). Consequently, oxeye daisy has been declared a noxious weed in many areas (Holm et al. 1997). It is found throughout most of the United States and north into southern Canada from Labrador to British Columbia (USDA 1970).

A field study was conducted over 2 yr to compare efficacy and economics of glyphosate-resistant, sulfonylurea-tolerant, and conventional soybean (Glycine max) weed control programs. Herbicide programs in the three soybean systems provided at least 90% control of browntop millet (Brachiaria ramosa), prickly sida (Sida spinosa), yellow nutsedge (Cyperus esculentus), pitted morningglory (Ipomoea lacunosa), and hemp sesbania (Sesbania exaltata) in most cases and postemergence (POST)-only programs were as effective as preemergence (PRE) followed by POST programs. Control of hyssop spurge (Euphorbia hyssopifolia) ranged from 93 to 100% in glyphosate-resistant soybean and from 88 to 100% in conventional soybean, but control was 60 to 100% in sulfonylurea-tolerant soybean. Sicklepod (Senna obtusifolia) control was at least 91% in glyphosate-resistant and sulfonylurea-tolerant soybean but was 81% for the standard SAN 582 plus imazaquin PRE and acifluorfen plus bentazon early POST treatment in conventional soybean. In glyphosate-resistant soybean, glyphosate applied sequentially resulted in an average yield of 3,020 kg/ha with a net return of $407/ha. In sulfonylurea-tolerant soybean, chlorimuron applied sequentially yielded 2,500 kg/ha with a net return of $271/ha. Conventional soybean yield with the standard herbicide program was 2,770 kg/ha with a net return of $317/ha. Yields for the cultivars were equivalent when the same standard herbicide program was used. When weed control is satisfactory and herbicide costs relatively comparable, yield potential of the cultivar and seed cost, including any technology fee, would be key factors in selecting a weed management system.

Studies were conducted to determine effects of preharvest applications of glyphosate on the seed and seedling quality of ‘Alpowa’ and ‘Penawawa’ soft white spring wheat (Triticum aestivum) varieties. Glyphosate was applied at 0.62 or 0.84 kg ae/ha at the milk (Zadoks' scale 70 to 79), soft dough (Zadoks' scale 85), or hard dough stage (Zadoks' scale 87) of wheat development; 7 d following the hard dough treatment; and 1 d prior to wheat harvest. In harvest aid applications, wheat yields were reduced only with glyphosate applied at the milk stage of development. Yield reduction ranged from 20 to 77% depending on the year, variety, and glyphosate rate. Likewise, kernel weight and germination were affected only by glyphosate applications at the milk stage with reductions from 19 to 73% and from 2 to 46% for kernal weight and percent germination, respectively, compared to untreated wheat. Using wheat from harvest-aided glyphosate treatments at the milk stage as seeds the following year resulted in reductions ranging from 28 to 99%, 19 to 39%, and 12 to 97% for seedling density, plant height, and seed yield, respectively, compared to seeds from untreated wheat. In this study, wheat seed and seedling quality following preharvest glyphosate applications were most greatly influenced by crop maturity stage at time of application than by herbicide rate or variety.

Field studies were conducted in 1994 and 1995 to evaluate CGA-152005 for weed control and effect on peanut (Arachis hypogaea) yield in Texas peanut production areas. CGA-152005 at 10 to 20 g/ha controlled eclipta (Eclipta prostrata), golden crownbeard (Verbesina enceliodes), and Palmer amaranth (Amaranthus palmeri) > 90% when applied preemergence (PRE) or soon after peanut emergence (EPOST). CGA-152005 postemergence (POST) controlled eclipta > 95%; sandhills amaranth (Amaranthus arenicola) 99%; golden crownbeard, pitted morningglory (Ipomoea lacunosa), and hophornbeam copperleaf (Acalypha ostryifolia) < 80%; and Palmer amaranth and ivyleaf morningglory (Ipomoea hederacea) from 37 to 89%. CGA-152005 injured peanut up to 37% and reduced yield up to 94%.

Effective methods are needed to eradicate tall fescue (Festuca arundinacea) and convert tall fescue fields into habitats more suitable to wildlife species. The objectives of this study were to determine the efficacy of (1) a single glyphosate application during the spring or fall and (2) AC 263,222, alone and in combination with glyphosate, applied during four different tall fescue growth stages for control of established tall fescue. Studies were conducted during 1996 to 1998 in fields dominated by tall fescue located in central Kentucky. Pre- and posttreatment plant communities were described to quantify differences in vegetative characteristics due to herbicide applications. Glyphosate at 2.2 kg ai/ha applied during the spring or fall was effective in reducing tall fescue to less than 12% cover. AC 263,222 at 0.2 kg ai/ha, AC 263,222 at 0.2 kg/ha plus glyphosate at 0.6 kg/ha, or AC 263,222 at 0.2 kg/ha plus glyphosate at 1.1 kg/ha applied during the spring growth, boot, summer dormancy, and fall growth stages were equally effective, reducing tall fescue cover to less than 3% at 2 to 7 mo after treatment. Glyphosate and AC 263,222 are effective tools for the initial removal of tall fescue.

Indigenous to tropical and East Asia, 20 species comprise the genus Pueraria in the Leguminosae (pea or bean family) (Mabberley 1989). The generic name commemorates Swiss botanist Marc Nicolas Puerari (1766–1845). The specific epithet lobata, from the Greek lobos, refers to kudzu's three-lobed leaves (Brown 1956).