Field experiments were conducted to evaluate the tolerance of 79 winter wheat cultivars to cyanazine, BAY SMY 1500, and metribuzin. When known, the pedigree of the more cyanazineand BAY SMY 1500-tolerant hard red winter cultivars included ‘Hope’ and/or ‘Cheyenne’ parentage. However, the cultivars more sensitive to BAY SMY 1500, notably those with ‘Vona’ parentage, were not consistently sensitive to cyanazine. Visible injury on the hard red and soft red winter cultivars did not consistently indicate yield reductions. The soft red winter cultivars, compared to the hard red winter cultivars, were generally more sensitive to cyanazine than BAY SMY 1500.

Experiments were conducted at three North Carolina research stations in 2003 to evaluate weed control and corn yield in glyphosate-resistant, glufosinate-resistant, imidazolinone-tolerant, and conventional corn weed management systems. Late-season control of common lambsquarters, large crabgrass, and yellow nutsedge increased with metolachlor PRE compared with no PRE herbicide treatment. Common lambsquarters, pitted morningglory, entireleaf morningglory, spurred anoda, and tropic croton control was improved by a single early POST (EPOST) application regardless of herbicide system. Control of common lambsquarters, pitted morningglory, entireleaf morningglory, and spurred anoda was similar for glyphosate and glufosinate systems for each POST over-the-top (POT) herbicide system. A single EPOST application of imazethapyr plus imazapyr to imidazolinone-tolerant corn controlled common lambsquarters, pitted morningglory, entireleaf morningglory, and spurred anoda and was better than a single EPOST application of glyphosate, glufosinate, or nicosulfuron. Tropic croton was controlled ≥ 95% with glufosinate or glyphosate, applied once or twice, or in mixture with metolachlor. A single EPOST application of imazethapyr plus imazapyr or nicosulfuron did not control tropic croton. Common lambsquarters, entireleaf morningglory, large crabgrass, Palmer amaranth, and yellow nutsedge control was greater with a late-POST–directed (LAYBY) of ametryn than no LAYBY. Systems that did not include a POT herbicide system had the lowest percentage in the weed-free yield and the lowest yield. Treatments that included a POT system with or without a PRE treatment of metolachlor yielded within 5% of the weed-free treatment, regardless of herbicide system.

Research on weed management in furrow-irrigated rice is needed as water availability becomes more limited in rice production regions of Arkansas. Research was conducted at Keiser and Pine Tree, AR, with the objectives being to determine (1) whether the addition of clomazone to imazethapyr would improve PRE weed control in furrow-irrigated, imidazolinone-tolerant rice, and (2) whether increasing the imazethapyr rates would improve weed control without injuring rice. Imazethapyr was applied at 70, 87.5, and 105 g ai/ha PRE with and without clomazone followed by imazethapyr POST at the same rate as used PRE. No rice injury was observed during the growing season at either site. Clomazone plus imazethapyr applied PRE did not improve early season control of Palmer amaranth, pitted morningglory, prickly sida, barnyardgrass, or broadleaf signalgrass over imazethapyr alone. Increasing the PRE imazethapyr rate to 105 g/ha did not improve Palmer amaranth or pitted morningglory control. Imazethapyr applied PRE on a clay soil generally provided lower weed control than on the silt loam soil. Increasing the imazethapyr rate did not improve rice yields.

The English daisy, Bellis perennis L., is a widespread lawn weed and a bane to those who favor daisy-free lawns and golf courses. The genetic name Bellis, a designation used by Pliny, means “pretty”; perennis means “through the years,” “continuing,” or “perennial” (Gledhill 1985; Mabberley 1989). While pretty, the English daisy is a persistent weed that spreads by short stolons (Tutin et al. 1976). It is a member of the cosmopolitan family Compositae, which encompasses 1,100 genera and 25,000 species (Heywood 1993). The genus Bellis comprises about 15 European and Mediterranean species. Some of them are medicinal and some are cultivated ornamentals, especially forms of B. perennis. The signature of this species is a flower head that Closes at night and in wet weather (Tutin et al. 1976).

Alligator weed is a serious weed in many countries. In Australia, it is a “weed of national significance” because of its actual and potential impact. We surveyed all local governments in New South Wales in 2001 and 2007 to determine whether the weed is being contained. We found an increased number and extent of infestations, despite more resources and a better knowledge base. Most considered that further research is needed in tactics for control of the weed. On the basis of current containment in urban gardens, we recommend that governments better mobilize the community (e.g., bush restoration consultants, Landcare groups) to deal with alligator weed infestations.

Redstem filaree is becoming widespread and abundant on the Canadian prairies. A field study was conducted to determine the growth, development, and seed yield response of redstem filaree when grown under noncropped conditions and planted at various dates throughout the growing season in Alberta. Redstem filaree emerged within 7 to 13 d of planting with an accumulated 57 to 134 growing degree days (GDD). Flowering occurred within 46 to 65 d (327 to 779 GDD) of planting. Plants that emerged in August or later did not flower in that season and survived as winter annuals. Spring-emerging redstem filaree plants matured within 79 to 100 d (729 to 1,193 GDD). Plants that emerged in May and June attained more biomass and produced threefold more seeds than plants that emerged in July or later. Redstem filaree seed production ranged from 2,400 to 9,900 seeds/plant depending on emergence date and environmental conditions. Information from this study will assist in developing integrated management strategies for this increasingly important weed.

Glyphosate and package mixtures of glyphosate plus dicamba or 2,4-D were evaluated for the selective control of jointed goatgrass and downy brome in seeded perennial grasses. Glyphosate at 560, glyphosate plus dicamba at 550 + 220, and glyphosate plus 2,4-D at 420 + 350 and 570 + 470 g ai/ha controlled 90% or more jointed goatgrass in 1988 and 1991. Glyphosate plus 2,4-D at 150 + 120 and 280 + 240 g/ha were the only treatments that controlled less than 90% of jointed goatgrass in 1991. In 1988, glyphosate at 210 g/ha and glyphosate plus dicamba at 210 + 80 g/ha were the only treatments that controlled less than 90% of downy brome. Glyphosate at 210, 280, 420, and 560 g/ha, glyphosate plus dicamba at 210 + 80, 280 + 110, 420 + 170, and 550 + 220 g/ha, and glyphosate plus 2,4-D at 150 + 120, 280 + 240, 420 + 350, and 570 + 470 g/ha controlled 90% or more downy brome in 1990. Pubescent wheatgrass and crested wheatgrass were stunted or killed if they were growing when herbicides were applied.

Three experiments were conducted to evaluate early POST control of yellow woodsorrel using PRE-applied herbicides. In experiment 1, yellow woodsorrel was seeded at two dates in a commercial pine-bark substrate and grown until reaching either the cotyledon–one-leaf (C-1L) or two- to four-leaf (2-4L) growth stage. The herbicides isoxaben, indaziflam, and dimethenamid-p were applied at these growth stages. Two rates of isoxaben and indaziflam provided yellow woodsorrel control (≥ 80% reduction in fresh weight [FW]) when applied at the C-1L stage; however, once yellow woodsorrel reached the 2-4L stage, indaziflam was the only herbicide that provided effective control at both rates tested. Experiments 2 and 3 were similar to experiment 1, except two labeled rates of dithiopyr were also evaluated. In experiment 2, all herbicides evaluated provided ≥ 90% reduction in FW of yellow woodsorrel at the C-1L stage. Although no differences in FW were observed among any of the herbicide treatments when yellow woodsorrel were treated at the 2-4L stage, control ratings indicated that indaziflam provided the most effective yellow woodsorrel control. Experiment 3 results also indicated that isoxaben, indaziflam, and dithiopyr controlled yellow woodsorrel (≥ 95% reduction in FW) when treatments were applied at the C-1L stage, whereas dimethenamid-p reduced shoot FW 70%. When yellow woodsorrel was treated after reaching the 2-4L stage, indaziflam provided the greatest control of any herbicide evaluated.

Vinasse and biochar are by-products of biofuel production that can be used as sources of nutrients to crops or soil amendments to improve soil quality. Despite the recent interest in biochar and vinasse effects on soil properties, little is known about their effect on weed communities. We hypothesized that the addition of biochar and vinasse to the soil could affect weed seed germination and growth, and that different weed species would show different responses to these soil amendments. Therefore, the objectives of this study were to determine the effects of vinasse and biochar on the germination and growth of Palmer amaranth, sicklepod, and southern crabgrass. The study was conducted under laboratory and growth chamber conditions. Treatments consisted of four levels of vinasse (0, 10, 20, and 40 L m−2) and biochar (0, 0.5, 2.5, and 12.5 kg m−2) applied to a sandy loam soil. Biochar at 0.5 and 2.5 kg m−2 increased germination of Palmer amaranth but had no effect on sicklepod and southern crabgrass. Vinasse reduced germination of all species. However, sicklepod germination was less affected by vinasse at 10 and 20 L m−2 than the other two species. Vinasse at 40 L m−2 decreased Palmer amaranth, southern crabgrass and sicklepod germination 57, 26 and 87%, respectively. Biochar had no consistent effect on the vegetative growth of the species studied. Vinasse at 10 L m−2 stimulated growth of sicklepod and southern crabgrass compared to the nontreated control. Our results suggested that vinasse used as a soil amendment could affect weed community structure by decreasing germination of susceptible species, but plants and weed species that can get established in vinasse amended soils might show higher growth rates.

The introduction of 2,4-D–resistant soybean will provide an additional POST herbicide site of action for control of herbicide-resistant broadleaf weeds. The introduction of this technology also brings concern of off-site movement of 2,4-D onto susceptible crops such as sensitive soybean and tomato. The 2,4-D formulation approved for use in 2,4-D–resistant soybean restricts application of the herbicide to nozzles that produce very coarse to ultra-coarse droplet spectrums. The use of larger droplet spectrums for broadcast applications can reduce herbicide deposition onto target weeds and thus influence herbicide efficacy. Field experiments were conducted to evaluate the influence of nozzle design on herbicide deposition onto target plants and the resulting efficacy of a POST application of 280 g ha−1 glyphosate plus 280 g ha−1 2,4-D. The TTI11004 nozzle produced an ultra-coarse droplet spectrum and reduced coverage and deposition density on spray cards as compared with the XR11004 and TT11004 nozzles that produced medium droplet spectrums. The AIXR11004 nozzle also reduced deposition density on spray cards but did not reduce coverage. Herbicide solution deposition onto glyphosate-resistant Palmer amaranth, tall waterhemp, giant ragweed, and horseweed ranged from 0.28 to 0.72 µl cm−2 and was not influenced by nozzle design. Herbicide efficacy was reduced by the TTI11004 nozzle on Palmer amaranth and horseweed compared with the AIXR11004, TT11004, and XR11004 nozzles when applications were made to either high densities of plants or plants exceeding the labeled height. The use of the AIXR11004 and TTI11004 nozzles that are listed as approved nozzles for glyphosate plus 2,4-D applications on 2,4-D–resistant soybean did not reduce herbicide deposition onto four of the most troublesome broadleaves and did not reduce herbicide efficacy when applied in conjunction with lower weed densities and smaller weeds.

Turfgrass managers can reduce foliar bleaching of smooth crabgrass from mesotrione by tank-mixing triclopyr ester with applications. These tank mixtures also have potential to enhance smooth crabgrass control compared to mesotrione alone. The objectives of this research were to evaluate the influence of triclopyr on the efficacy, absorption, and translocation of mesotrione in multitiller smooth crabgrass. In field experiments, tank-mixing triclopyr at 560 or 1,120 g ae ha−1 with mesotrione at 140 g ai ha−1 applied sequentially or at 280 g ha−1 applied singly provided excellent control (> 90%) of multitiller smooth crabgrass in tall fescue. These treatments were more effective than mesotrione alone and fenoxaprop at 195 g ai ha−1 that averaged 66 and 81% control after 6 wk, respectively. Mesotrione alone at 280 g ha−1 bleached smooth crabgrass 53% at 2 wk after initial treatment (WAIT), and was 14% greater than the 140 g ha−1 treatment. Sequential treatments of the low mesotrione rate bleached smooth crabgrass 16 to 22% from 3 to 5 WAIT. Triclopyr tank mixtures reduced smooth crabgrass bleaching from mesotrione on all dates to < 5%. Tall fescue injury was not detected at any evaluation date. In laboratory experiments, smooth crabgrass reached peak foliar absorption of 14C-mesotrione at 24 and 168 h after treatment (HAT; 23% and 15%) when mesotrione was applied with triclopyr at 1,120 and 0 g ha−1, respectively. Triclopyr reduced translocation of radioactivity 12% at 72 and 168 HAT, compared to 14C-mesotrione alone. Enhanced foliar uptake of mesotrione from triclopyr tank mixtures might improve control of multitiller smooth crabgrass compared to mesotrione alone. Reduced foliar bleaching from triclopyr is associated with less translocation of mesotrione or derivatives in smooth crabgrass.

A crops ability to both suppress weed growth and tolerate weed competition is a key consideration when taking an agroecological approach to weed management. Amongst other cereals, oats are widely considered to have superior weed competitiveness yet studies examining competitive ability of oat varieties are rare. We investigated the ability of oats to suppress weeds and yield in the presence of competition from weeds in trials involving five husked and three naked oat varieties at an organic site in the east of England over four trial years (2009-13). We identified a number of key traits that were important for weed suppression including establishment rate, tillering ability, and early leaf area index (LAI) which highlight the importance of rapid early growth rate. Furthermore, taller varieties tended to be more weed tolerant but not necessarily more suppressive. Trade-offs between competitive traits and yield were not found in this study. Crop tillering ability was highlighted as an important trait for selection due to its beneficial effects on weed suppression as well as grain yield and also its high heritability.

The duration of the soil activity of an acetolactate synthase-(ALS) inhibiting herbicide which is currently under approval for sugar beet cultivation was determined in a field trial series in Germany in 2013 and 2014. The herbicide containing foramsulfuron (FSN; 50 g L−1) and thiencarbazone-methyl (TCM; 30 g L−1) was applied in different dosages (25+15, 37.5+22.5 and 50+30 g FSN+TCM ha−1) to the bare soil. Five weed species (rapeseed, common lambsquarters, wild chamomile, blackgrass, barnyardgrass) were sown at 5, 10, 15 and 20d after application. The duration of the soil activity was assessed by determining percent weed control in the treated plots. The longest duration was observed after applying 50+30 g FSN+TCM ha−1, but the influence of environment was much stronger than the dosage effect. The mean duration of soil activity was 10 to 15 d in 2013 and longer than 20 d in 2014. Differences among weed species in their response to the herbicide treatments were small.

Longspine sandbur is a troublesome weed infesting corn in the Great Plains. However, herbicides are now available to control this species. This study characterized longspine sandbur ecology in irrigated corn to aid producers in integrating herbicides into their production systems. Longspine sandbur began emerging May 25, and by June 15, 84% of the seasonal emergence had occurred. Plant development was related to cumulative growing degree days. Seeds were viable early in longspine sandbur's development, with 20% of seeds viable by heading. Producers can minimize seed production of longspine sandbur in field borders by mowing plants at the boot stage. Bur production per plant was related to time of emergence, with seedlings emerging in late May producing 1,120 burs per plant. Seedlings emerging 4 wk later produced 84% fewer burs. Controlling longspine sandbur before 4 wk of interference prevented loss of corn grain yield.

Field studies were conducted from 1997 to 1999 to evaluate the influence of broadleaf herbicides on double-crop glyphosate-resistant soybean injury and yield at Belleville, IL. Diphenylether herbicides applied postemergence (POST) caused 10 to 48% necrosis 7 days after treatment (DAT). POST herbicides caused 0 to 8%, 8 to 37%, and 0 to 12% height reduction 7 DAT in 1997, 1998, and 1999, respectively. In most instances, diphenylether herbicides did not delay soybean maturity, whereas imazethapyr applied POST delayed soybean maturity in 1998 and 1999. Acifluorfen plus bentazon reduced soybean height at maturity in 1997 and 1998, whereas lactofen, imazethapyr, and imazamox reduced height only in 1998. Diphenylether herbicides did not reduce grain yield when compared to the no-herbicide hand-weeded treatment, but imazamox reduced yield by 18%. Furthermore, the soil herbicides applied preemergence and diphenylether herbicides applied POST did not reduce grain yield when compared to glyphosate alone.

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.

DC X2-5309 organosilicone adjuvant added at 1% (v/v) spray solution increased the efficacy of bentazon, pyridate, and terbacil on kochia in greenhouse trials. DC X2-5309 decreased the rain-free period needed after application of bentazon and bromoxynil to 6 and 1 h, respectively, and increased the uptake of 14C-bentazon and 14C-bromoxynil by kochia at 1, 3, 6, and 24 h after application compared with crop oil concentrate (COC). In field trials, bentazon and bromoxynil rates required to control equal amounts of kochia were reduced by half when adding DC X2-5309 compared with adding crop oil concentrate. DC X2-5309 added at 0.5% (v/v) spray solution with bentazon did not injure spearmint and controlled kochia equal to or better than bentazon with COC added at 1% (v/v) spray solution.

A reason given by cash-grain farmers for not using manure from neighboring livestock operations is that manure may cause greater field weediness. To address this concern, trials were established in corn on 11 cash-grain farms, in which manure from six nearby dairy farms was spread for the first time in at least 10 yr. A split-plot design was used in which manured and nonmanured treatments were established as whole-plots, and split-plot treatments were either with or without the farmer's regular weed control. In the multisite analysis, weed seedling density at the time of corn emergence was not greater in the manured vs. nonmanured treatments. At 7 to 8 wk following planting, weed density was not greater in the manured plots. Just before corn canopy closure, weed biomass also did not differ between manured and nonmanured treatments. Although neither weed species richness nor species diversity differed significantly between manured and nonmanured treatments, these measures did have significant environment-by-manure interactions, indicating that weed species distributions responded differently to manure across the different trial environments. However, farmers' weed control practices were highly successful in both the manured and nonmanured plots. Large portions (280 m2) of all whole plots were visually inspected for introduced weed species after all weed control practices had been completed. The manured treatments did not differ significantly in the set of species observed, suggesting that manure did not introduce new weed species. Thus, this exploratory study showed that, contrary to some farmers' concerns, an application of dairy manure neither increased field weediness nor required alterations in the farmers' weed control programs.

Experiments were conducted in 1985 and 1986 at three locations in eastern Arkansas to evaluate red rice control in soybeans with postemergence grass herbicides and plant growth regulators applied singly or sequentially at early to late-tillering growth stages of red rice. Haloxyfop at 0.21 kg ai/ha and quizalofop at 0.14 kg ai/ha applied singly or sequentially and fluazifop at 0.21 kg ai/ha applied sequentially consistently controlled red rice and suppressed seedhead production in soybeans. Mid-season treatments were not beneficial when high soil moisture stress conditions existed. Mefluidide or sethoxydim applied singly or sequentially or amidochlor applied singly provided erratic control and seedhead suppression of red rice in soybeans.

Treatments of dimethenamid-p at 0.7 kg ai/ha applied PRE in tank mixtures with EPTC (3.4 kg ai/ha), metribuzin (560 g ai/ha), pendimethalin (1.1 kg ai/ha), or rimsulfuron (26 g ai/ha) were compared with the same herbicides applied PRE alone in field efficacy trials in Idaho, Oregon, and Washington. Common lambsquarters, kochia, and redroot pigweed control was generally improved with dimethenamid-p tank mixtures compared with control by any herbicide applied alone except metribuzin. Hairy nightshade control at two locations was generally improved with tank mixtures compared with control by any herbicide applied alone. At Washington, where row spacing was narrower than at other locations, dimethenamid-p alone or in tank mixtures provided similar hairy nightshade control, and this control was greater than control by EPTC, metribuzin, or pendimethalin applied alone. ‘Alturas’, ‘Bannock Russet’, ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, and ‘Shepody’ potato tolerance to dimethenamid-p PRE at 0, 0.7, or 1.4 kg ai/ha was assessed in weed-free field trials conducted at Aberdeen, ID, in 2002 and 2003. Little or no crop injury was evident during the growing seasons and there were no reductions in U.S. No. 1 and total tuber yields regardless of dimethenamid-p rate or potato variety.