Two field studies were conducted in Louisiana to determine the impact of Nealley’s sprangletop on rough rice yield under multiple environments in 2014, 2015, and 2016. The first study evaluated optimal timings of Nealley’s sprangletop removal for optimizing rough rice yields. The second study evaluated the impact of Nealley’s sprangletop densities on rough rice yield. Nealley’s sprangletop was removed with applications of fenoxaprop at 122 g ai ha–1 at 7, 14, 21, 28, 35, and 42 d after emergence (DAE). Nealley’s sprangletop removal at 7 and 14 DAE resulted in higher rough rice yields of 7,880 and 6,960 kg ha–1, respectively, when compared with the rice from the season-long Nealley’s sprangletop competition with a 6,040 kg ha-1 yield. Delaying herbicide application from 7 DAE to 42 DAE resulted in a yield loss of 1,740 kg ha–1. Over the 35-d delay in application, rough rice yield loss from Nealley’s sprangletop interference was equivalent to 50 kg ha–1 d–1. Nealley’s sprangletop densities were established at 1, 3, 7, 13, and 26 plants m–2 by transplanting Nealley’s sprangletop when rice reached the one- to two-leaf stage. At Nealley’s sprangletop densities of 1 to 26 plants m–2, rough rice yields were reduced 10 to 270 kg ha–1, compared with the rice from weed-free plots. Based on regression analysis, Nealley’s sprangletop densities of 1, 35, 70, and 450 plants m–2 reduced rough rice yield 0.14%, 5%, 10%, and 50%, respectively.

Experiments were conducted to determine the energy requirements and the most effective rotary tiller configuration for incorporating cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile} on an 18-cm band centered on top of the previous year's corn (Zea mays L.) ridge. When the rotary tiller was operated full width at a 10-cm depth, the least cyanazine concentration was found in the center of the ridge, and the greatest concentration was found between ridges. The treatment having the greatest cyanazine concentrations in the center of the ridge and the least in the inter-row between ridges consisted of a ridge cleaner, a cyanazine application, and the rotary tiller configured to till a. 30-cm strip on the center of the ridge with a rotor enclosure. Energy requirements for operating the rotary tiller increased as the depth of operation increased, and the 10-cm depth of operation required less energy than two passes with a tandem disk.

Flucarbazone controls certain grassy weeds in wheat and may have potential for controlling perennial ryegrass in tall fescue turf. The objective of these experiments was to investigate perennial ryegrass and tall fescue tolerance to flucarbazone at two application timings. In field experiments, flucarbazone applications in May were more injurious to both species than in February and March. Single applications of flucarbazone from 30 to 60 g ai ha−1 in May injured both species 35 to 50% and sequential treatments increased injury approximately twofold. Two applications of flucarbazone at 60 g ha−1 in May injured both grasses > 90%, similar to sequential applications of trifloxysulfuron at 29 g ai ha−1. In growth chamber experiments, injury from flucarbazone on both grasses increased as temperature increased from 10 to 30 C. Flucarbazone reduced total shoot biomass of both grasses at all temperatures after 4 wk. Overall, perennial ryegrass and tall fescue are tolerant to flucarbazone at moderate temperatures (10 to 20 C). However, injury increased substantially under warmer conditions (30 C), suggesting flucarbazone could control perennial ryegrass and tall fescue during late spring and early summer.

Five johnsongrass populations collected from corn grown in northern Greece were studied to elucidate the levels and mechanisms of resistance to acetolactate synthase (ALS)- and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Whole-plant response assays indicated that two populations were highly cross-resistant to all ALS inhibitors tested (foramsulfuron, nicosulfuron, rimsulfuron, and imazamox) but were effectively controlled by the recommended rate of the ACCase-inhibiting herbicides propaquizafop and clethodim. The ALS gene sequence revealed a point mutation that resulted in the substitution of Trp574 by Leu in the ALS enzyme, suggesting that the resistance mechanism is target-site mediated. These findings highlight a serious threat against the sustainable use of the ALS-inhibiting herbicides in controlling johnsongrass and other grass weeds in cornfields, suggesting rotational use of herbicides with different modes of action, along with the use of nonchemical methods, for viable Johnsongrass management.

Johnsongrass control systems that included commercially available corn herbicides applied to crop sequences of continuous corn or corn–cotton–corn rotation were evaluated over a 3-yr period at the Texas Agricultural Experiment Station in Burleson County. Herbicide treatments evaluated were EPTC + R-25788 applied preplant incorporated (PPI); metolachlor applied preemergence (PRE); nicosulfuron applied postemergence (POST); and the combination of metolachlor PRE and glyphosate POST applied after corn harvest. Weed control practices applied to plots planted to cotton in the second growing season provided excellent johnsongrass control (≈ 95%). Visual control ratings indicated that nicosulfuron provided the best johnsongrass control (> 80%) among the herbicides evaluated all three years. Metolachlor and glyphosate combinations provided acceptable johnsongrass control the third year of the experiment in both cropping sequences. Corn grain yield and johnsongrass control were best in cotton-rotated plots. The highest returns observed in continuous corn were from either nicosulfuron or the combination of metolachlor and glyphosate. Net returns for all control systems in corn–cotton–corn rotated plots were greater than the weedy check and were equivalent to the lead systems in continuous corn.

The name Polygonum is a very ancient derivative, composed of the two Greek words, polys, many, and gony, knee or joint, alluding to the numerous and conspicuous nodes in the stems of many species. The Greek physician Heraclides Tarentina (third and second centuries BC) prescribed prostrate knotweed, P. aviculare L., as a remedy against bleeding from the ear. Dioscorides, a Greek botanist, was the first to characterize Polygonum as having “numerous slender branches, creeping on the ground like grass, with fruit at each leaf.” Subsequently, other Greek physicians, poets, and botanists applied the name to the knotweed/smartweed group, and in 1753, Linneaus adopted it for the genus. The species name for pale smartweed, lapathifolium, is from lapathi, meaning sorrel-like or dock-like (Gledhill 1985; Hyam and Pankhurst 1995; Small 1895).

Field studies were conducted for four consecutive years to determine if repeated applications of trifluralin (preplant incorporated), metolachlor (preemergence), and fluazifop (postemergence) herbicides alone or combined could be utilized in soybean to effectively control grass weed populations and maintain optimum yield in an irrigated environment where metribuzin plus dinoseb (preemergence) and 2,4-DB plus linuron (postemergence) were used as a standard weed control system. After repeated applications each year, all treatments maintained similar yields that were no different from yields obtained from the standard system. Grass weed infestation did not increase significantly in the treatment that received only the standard weed control herbicides over the duration of the study.

Carpetgrass is a warm season grass used in the south as low maintenance turf, especially in wet areas where other turf species do not persist. The response of carpetgrass to postemergence (POST) herbicides currently available for turf producers has not been thoroughly investigated and was the objective of four experiments conducted over a 2-yr period. Slight reduction in turf quality followed application of atrazine (2.2 kg ai ha-1), bentazon (2.2 kg ai ha-1), imazaquin (0.4 and 0.6 kg ai ha-1), mecoprop (1.1 kg ai ha-1), triclopyr (0.6 kg ai ha-1), metsulfuron (0.2 kg ai ha-1), 2,4-D (1.1 kg ai ha-1), 2,4-D plus dicamba (0.8 + 0.3 kg ai ha-1), and 2,4-D plus dicamba plus mecoprop (0.9 + 0.1 + 0.5 kg ai ha-1). Marginally acceptable turf quality followed sulfometuron (0.2 kg ai ha-1), sethoxydim (0.3 and 0.6 kg ai ha-1), and diclofop (2.2 kg ai ha-1) treatments. Unacceptable turf quality resulted from asulam (2.2 kg ai ha-1) and MSMA (1.1 and 2.2 kg ai ha-1) treatments. Carpetgrass tolerated most POST broadleaf and sedge herbicides but was sensitive to most POST grass herbicides used in other turf species, with the exception of sethoxydim.

Field studies were conducted near College Station, TX, in 2006 and 2007 to evaluate the economic impact of common sunflower interference in field corn. A density of one common sunflower per 6 m of crop row caused a yield loss of 293 kg ha−1. Estimated losses at a net corn price of $0.08 kg−1 was $92 ha−1 for infestation levels of four common sunflower plants per 6 m of row. Corn yield was increased by 32 kg ha−1 by each 1,000 plant ha−1 increase in corn planting density. Corn planting densities of 49,400 and 59,300 plants ha−1 provided the greatest net returns with or without the presence of common sunflower competition. Corn yields were reduced by extended duration of sunflower competition, with losses exceeding 1,500 kg ha−1 per week and increasing in magnitude at a decreasing rate throughout the growing season. Herbicide treatments provided net returns of $600 to $1,300 ha−1 above no weed control in both 2006 and 2007. Net returns of $609 and $653 ha−1 were obtained without the use of any herbicide for sunflower control. Determining the economic impact of common sunflower interference in field corn allows producers to estimate the overall net return on the basis of duration of common sunflower interference and density, while considering varying net corn prices, crop planting density, and herbicide application costs.

Conventional grain sorghum is highly susceptible to POST grass control herbicides. Development of aryloxyphenoxypropionate-resistant grain sorghum could provide additional opportunities for POST herbicide grass control in grain sorghum. Field experiments were conducted at Hays and Manhattan, KS, to determine the effect of quizalofop rate and crop growth stage on injury and yield of aryloxyphenoxypropionate-resistant grain sorghum. Quizalofop was applied at 62, 124, 186, and 248 g ai ha−1 at sorghum heights of 8 to 10, 15 to 25, and 30 to 38 cm, which corresponded to early POST (EPOST), mid-POST (MPOST), and late POST (LPOST) application timings, respectively. Grain sorghum injury ranged from 0 to 68% at 1 wk after treatment (WAT); by 4 WAT, plants generally recovered from injury. The EPOST and MPOST applications caused 9 to 68% and 2 to 48% injury, respectively, whereas injury from LPOST was 0 to 16%, depending on rate. Crop injury from quizalofop was more prominent at rates higher than the proposed use rate in grain sorghum of 62 g ha−1. Grain yields were similar in treated and nontreated plots; applications of quizalofop at different timings did not reduce yield except when applied MPOST at the Manhattan site.

Field experiments were conducted in Louisiana and Mississippi from 2011 through 2013 to evaluate crop injury, weed control, and yield in field corn following pyroxasulfone applied PRE and POST. Pyroxasulfone PRE or POST did not injure corn at any evaluation. Barnyardgrass control was not improved with the addition of any POST treatment to pyroxasulfone alone or atrazine plus pyroxasulfone PRE; however, all POST treatments increased barnyardgrass control to at least 95% at all evaluations following atrazine PRE. All treatments that contained a PRE followed by POST application controlled browntop millet ≥90% at all evaluations. All POST treatments increased ivyleaf morningglory control to ≥92% following atrazine or pyroxasulfone alone PRE. However, control with atrazine plus pyroxasulfone PRE was similar or greater 28 d after POST than all treatments that received a POST application. In the absence of a POST treatment, pyroxasulfone or atrazine plus pyroxasulfone PRE controlled Palmer amaranth 93 to 96% at all evaluations, but atrazine alone PRE provided 84, 82, and 66% control 7, 14, and 28 d after POST, respectively. All programs that contained a PRE followed by POST herbicide treatment controlled Palmer amaranth >90% at all evaluations. Corn yield following all treatments except atrazine alone PRE and the nontreated were similar and ranged from 10990 to 12330 kg ha−1. This research demonstrated that pyroxasulfone can be a valuable tool for weed management in a corn weed management program.

Enhanced dissipation of atrazine has been documented in many parts of the world where the herbicide has been extensively used. Atrazine is widely used in corn in Illinois, but enhanced dissipation in the field has not been documented. In this study, the dissipation of atrazine was measured in three fields. Two of the fields (URB-1 and URB-2) had not been treated with atrazine for 3 and 4 yr, respectively, whereas the third field (ORR-1) had received annual applications of atrazine for 9 yr. A laboratory assay conducted on soil collected from these fields prior to atrazine application indicated that soil from ORR-1 had enhanced atrazine dissipation (half life [DT50] 1.7 d). Soil from fields URB-1 and URB-2 dissipated atrazine much slower (DT50 was 13 and 11d, respectively). In the field, the rates of atrazine dissipation were similar to those measured in the laboratory. The DT50s were 2.4, 8.4, and 12.6 d for ORR-1, URB-2, and URB-1, respectively. Testing the soils collected from the fields at the last sampling time for atrazine dissipation showed that all of them had enhanced atrazine dissipation, suggesting that the soil microbial populations had adapted to the presence of atrazine in the field.

Devil's-claw and smellmelon are summer annual broadleaf weed problems in the southwest cotton production region. Field studies conducted in 1993 and 1994 evaluated the efficacy of pyrithiobac for postemergence (POST) control of devil's-claw and smellmelon compared with soil-applied fluometuron or prometryn. Pyrithiobac at 0.07 and 0.14 kg ai/ha early POST and 0.14 kg ai/ha mid-POST controlled devil's-claw more than 84% at the late rating. Devil's-claw control with mid-POST applications of pyrithiobac at 0.07 kg ai/ha was reduced when compared with other rates and application timings. Smellmelon control with pyrithiobac ranged from 57 to 84% and, except when applied at 0.07 kg ai/ha early POST, was equivalent to or greater than either fluometuron or prometryn. Crop injury with pyrithiobac treatments 16 d after treatment was 5 to 13%, but 33 d later, was no more than 3%.

The movement and degradation of agricultural chemicals in soil and groundwater is a complex process, influenced by climatic conditions, site characteristics, chemical properties, and agricultural practices. Because of this complexity, mechanistic models are useful tools in evaluating environmental fate. Although currently available unsaturated zone models often do not provide accurate concentration profiles when compared with field measurements, they can be used to estimate the depth and extent of movement. Another application of modeling is to compare predicted movement under different simulation conditions to determine the significance of the various factors affecting the behavior of agricultural chemicals. When properly designed and interpreted, modeling studies can contribute to the understanding of the environmental fate of agricultural chemicals. When necessary, modeling can also be useful in developing management practices included on the label or in state regulations. Modeling has been a frequently used tool in developing restrictions for minimizing the movement of aldicarb residues into groundwater and preventing residues in drinking water. Examples of model use include optimizing application timing, estimating well setback distances, and identifying vulnerable soils.

Seasonal variations in tolerance of jack pine and white spruce to glyphosate and triclopyr were investigated in field and growthroom studies. Foliar injury was higher in both species following field applications of herbicides in July during periods of active growth than in September and October when the plants were not growing actively. Herbicides applied to trees in the growthroom 3 weeks after bud break caused greater injury than applications either before or 14 weeks after bud break. White spruce tolerated both glyphosate and triclopyr better than jack pine. Triclopyr injured both species more than glyphosate. Chemical analysis and electron micrographs showed that the cuticular wax deposition on both species was greater in field-grown trees than in growthroom-grown trees and was greater at 14 weeks after bud break than at 3 weeks. Increased wax deposition with time after bud break may reduce herbicide uptake and may account partially for the increased tolerance of both species to glyphosate and triclopyr.

Area-of-influence experiments were conducted on high–organic matter soils to assess the effect of common lambsquarters distances from ‘South Bay’ lettuce on yield and quality under two phosphorus (P) regimens. P was applied either banded (125 kg P/ha) or broadcast (250 kg P/ha) before lettuce planting. Lettuce plants were harvested at 0, 25, 50, 75, 100, and 125 cm from each side of the common lambsquarters plant after season-long interference. The regression equations were y = 0.40 + 0.36/(1 + e−0.09(x−52.5)), r 2 = 0.92, for banded P; and y = 0.40 + 0.29/(1 + e−0.07(x−69.3)), r 2 = 0.94 for broadcast P. Banded P produced 9% more fresh weight per head than the broadcast P treatment under weed-free conditions. Within the broadcast P treatments, common lambsquarters growing at 125 and 100 cm did not affect fresh weight of harvested lettuce. Values for fresh weight per head declined 18, 34, 38, and 38% when lettuce grew at 75, 50, 25, and 0 cm distance from common lambsquarters, respectively. Fresh weight of lettuce in banded P treatments was reduced only at 50, 25, and 0 cm distance from common lambsquarters plants, representing 31, 44, and 44% less than its weed-free control, respectively. Banding P at 50% (125 kg/ha) of the recommended broadcast rate reduced the area of influence of common lambsquarters with lettuce.

This research was designed to determine if sethoxydim-resistant corn hybrids exhibited levels of cross-resistance to other acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides. Three sethoxydim-resistant hybrids were tested in 1995 and four in 1996. The hybrids were treated with the 1 × (labeled use rate for annual grass control) and 4 × rate of clethodim, fenoxaprop-P plus fluazifop-P, fluazifop-P, quizalofop-P, and sethoxydim. At the 1 × rate, similar levels of corn safety were observed in both years with sethoxydim, quizalofop-P (except Asgrow RX620SR in 1995), and in 1996, fenoxaprop-P plus fluazifop-P. Corn treated with the 4 × rate of sethoxydim did not exhibit injury, while all other ACCase-inhibiting herbicides cause > 50% corn injury. Sethoxydim-resistant com hybrids used in this study did not consistently exhibit acceptable levels of cross-resistance to other ACCase-inhibiting herbicides. The use of clethodim will control volunteer sethoxydim-resistant corn in rotational crops.

Southern wax myrtle is a pernicious weed in south Florida pastures and this plant can eliminate all forage production under high densities. Previous work has shown that triclopyr at 1.12 kg/ha is the most effective herbicide on this species. The introduction of the Burch Wet Blade (BWB) mowing system provides an alternative application method to traditional broadcast herbicide applications. The objective of this experiment was to compare the efficacy of triclopyr and other herbicides using both broadcast and the BWB application systems. In general, broadcast applications of at least 1.1 kg/ha triclopyr provided better control than the same treatments applied with the BWB system in 1998. In 1999, control was lower overall compared to 1998, but the same trend was observed. Broadcast applications of triclopyr reduced wax myrtle densities better than when herbicides were applied with the BWB system in 1998. However, in 1999, dicamba + triclopyr, and at least 1.1 kg/ha triclopyr reduced wax myrtle densities compared to the mow-only treatment, regardless of application method. Although the BWB system provided an initial overall reduction in plant height, recovery of plants was sufficient and often outgrew those receiving broadcast applications of herbicides. Regardless of application method, retreatment of wax myrtle plants 1 yr after the initial application will likely be needed to obtain adequate control.

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.

Known for thousands of years to produce a cleansing soaplike lather when crushed in water, bouncing-bet (Saponaria officinalis L. ♯3 SAWOF) is as pretty as its name. Though it has followed man around the world, it has always been an invited guest–until the 1900s, when our changing viewpoint redefined this millennial source of soap, fragrance, and beauty as a weed.