In Flanders fields the poppies blow
Between the crosses, row on row,
That mark our place; and in the sky
The larks, still bravely singing, fly
Scarce heard amid the guns below.

(In Flanders Field by Lieut. Col. John McCrae, who died in France on January 28, 1918, after four years of service on the Western Front)

The corn poppy (Papaver rhoeas L.), simple and enduring, has been a symbol of rural beauty and tradition for thousands of years. Artist John Ruskin (1819–1900) called it the most transparent and delicate of all the field blossoms (Haughton 1978). Other names for the species include field poppy, corn rose, pepper box, Flanders poppy, canker, redfield, and red poppy (de Bray 1978; le Strange 1977).

Greenhouse and field research was conducted to determine the effect of glufosinate, glyphosate, and glyphosate plus additional adjuvant on yellow nutsedge control and tuber production. Glyphosate at 0.84 kg/ha reduced yellow nutsedge dry weight 64%, whereas glufosinate at 0.4 kg/ha reduced dry weight only 22% when averaged over diammonium sulfate (DAS) and spray volume. Furthermore, yellow nutsedge dry weight was reduced 53% in the presence and 34% in the absence of DAS; however, dry weights were similar when spray volumes of glufosinate or glyphosate ranged from 140 to 1038 L/ha. Yellow nutsedge control with glyphosate and glufosinate increased to 88 and 68%, respectively, when the herbicides were injected into the plant. In the field, glufosinate at 0.4 kg/ha and glyphosate at 0.84 kg/ha controlled yellow nutsedge 19 and 53%, respectively. Glyphosate reduced yellow nutsedge tuber density 51%, tuber fresh weight 59%, and tuber sprouting 17% 42 wk after treatment in the field. The addition of nonionic surfactant, methylated seed oil, or crop oil concentrate to glyphosate plus DAS did not increase yellow nutsedge control with glyphosate in the greenhouse or field.

Field studies were conducted in 1988 and 1989 under dryland and irrigated conditions to determine effects of various herbicides for use in peanuts on weed control and peanut yield under a reduced tillage system. Under dryland and irrigated conditions, sethoxydim + acifluorfen consistently controlled Texas panicum. Paraquat + bentazon controlled Texas panicum poorly under dryland conditions. Pendimethalin + metolachlor provided ≥ 80% Texas panicum control under irrigated conditions.

Field experiments were conducted to evaluate the critical period for velvetleaf interference with cotton and to assess the reliability of using weed growth variables as predictors of cotton lint yield losses. An inverse linear relationship existed between velvetleaf dry weight and cotton lint yield. The relationship between the number of velvetleaf main-stem nodes or velvetleaf height with cotton lint yield was best described by quadratic regression equations. Weed dry weight appeared to be the most accurate predictor followed by weed height and by number of velvetleaf main-stem nodes. A nonlinear equation best described percent lint yield loss as a function of critical-period interference intervals.

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.

An isolate of the fungus Dactylaria higginsii obtained from purple nutsedge in Florida was highly pathogenic to Cyperus spp. The potential of this isolate as a bioherbicide was field tested in natural populations of purple nutsedge in Gainesville and Jay, FL. The fungus was applied in 0.5% Metamucil® as a carrier, and the treatments were: carrier only, 105 conidia/ml + carrier, and 106 conidia/ml + carrier. Treatments were applied as single, double, or triple postemergence (POST) sprays at biweekly intervals. The disease and secondary infections developed in about 5 and 15 d after inoculation, respectively, killing most of the infected leaves. All weed growth parameters and disease progress rates were affected by inoculum dosage and inoculation frequencies. Three inoculations, each at 106 conidia/ml, provided effective control of purple nutsedge compared to a single inoculation, as measured by shoot dry weight, tuber numbers, and tuber dry weight. Higher rates of disease progress and disease levels, defined by the area under the disease progress curve (AUDPC), occurred with three inoculations at 106 conidia/ml. Disease progress was slower and the level of weed control was lower at 105 conidia/ml compared to the higher inoculum level. Three applications of 106 conidia/ml provided >90% nutsedge control. Dactylaria higginsii appears to be an effective bioherbicide candidate deserving further development for commercial use.

Field trials were conducted in 2001 at the Tobacco Research Station near Oxford, NC, and in 2002 at the Lower Coastal Plains Research Station near Kinston, NC, to determine tobacco yield, injury, and shikimic acid accumulation in response to simulated glyphosate drift. Glyphosate was applied to 12- to 13-cm-high tobacco ‘K326’ early postemergence at 0, 9, 18, 35, 70, 140, 280, 560, and 1,120 (1×) g ai/ha. Crop injury was rated 7 and 35 d after treatment (DAT) and shikimic acid accumulation in leaves at 7 DAT, tobacco yield, and leaf grade index (whole-plant index of harvest interval leaf value) were also assessed. Shikimic acid accumulation and injury symptoms increased similarly as glyphosate rate increased. Glyphosate rates of 140 g/ha (0.125 of recommended rate) or higher resulted in significant crop injury, reduced tobacco yield, and decreased leaf grade index. Shikimic acid accumulation at 7 DAT was inversely related to tobacco yield. Shikimic acid accumulation was found to be an effective diagnostic tool to determine glyphosate drift in tobacco; however, in-season data are needed to correlate shikimic acid accumulation with yield loss.

During the establishment of alfalfa, POST applications of imazethapyr at 50 g/ha, following PPI applications of trifluralin at 1,100 g/ha, consistently provided ≥ 80% control of wild oat, volunteer canola, and shepherd's-purse with no crop injury. POST applications of the same rate of imazethapyr without PPI applications of trifluralin provided similar volunteer canola and shepherd's-purse control, but ≥ 80% wild oat control was achieved only 25% of the time. Imazethapyr, alone or following trifluralin, did not control common groundsel. Broadleaf weed control from imazethapyr at 50 g/ha tank mixed with fluazifop-P at 125 g/ha or sethoxydim at 200 g/ha was not reduced compared to imazethapyr alone. However, the probability of controlling wild oat by ≥ 90% was reduced from 83% to 0 when the same rate of imazethapyr was tank mixed with fluazifop-P, compared to fluazifop-P alone. Tank mixtures of imazethapyr at 50 g/ha and sethoxydim controlled wild oat only slightly less than sethoxydim alone. First cut and total herbage yields, obtained 1 yr after alfalfa establishment, increased where treatments effectively controlled broadleaf weeds and wild oat, compared to check plots. Second cut herbage and seed yields, also obtained 1 yr after alfalfa establishment, were not affected by any of the treatments.

The potential of Colletotrichum dematium f.sp. epilobii (ATCC 20981) to control fireweed (Epilobium angustifolium) was investigated. Under controlled environment conditions, plant age, inoculum density, length of the dew period, and temperature during the dew period affected the efficacy of C. dematium f.sp. epilobii. Seedlings sprayed with 1 × 109 conidia/m2 sustained the most damage. Susceptibility decreased with increasing plant age, and 10-wk-old plants were slightly affected by the fungus. Satisfactory levels of control were achieved when the dew period was >20 h and temperature during the dew period was 30 C. Control of fireweed increased when the C. dematium f.sp. epilobii conidia were suspended in a 25% v/v canola oil/water emulsion. Using this formulation, control of 4-wk-old seedlings was obtained with a 10-fold reduction in inoculum concentration (1 × 108 conidia/m2), the required dew period was reduced to 12 h, and the effect of the temperature during the dew period was minimized. In the field, C. dematium f.sp. epilobii alone or when amended with an oil emulsion failed to control fireweed growth. When the oil formulation of C. dematium f.sp. epilobii was tank mixed with a low rate of glyphosate, high levels of control were consistently achieved. Growth reduction achieved with this formulation was more than additive, suggesting a synergistic interaction. The effectiveness of the formulated conidial suspension of C. dematium f.sp. epilobii decreased with plant maturity, and 15-wk-old plants were not controlled. C. dematium f.sp. epilobii alone has limited potential as a candidate bioherbicide, but when formulated in an oil/water emulsion and combined with low rates of glyphosate, suppression of fireweed can be attained in the field.

Torpedograss is a serious problem in southern turfgrass, especially along the U.S. gulf coast. Studies were conducted during 1998, 1999, and 2000 to evaluate quinclorac for torpedograss control in bermudagrass turf. Three applications of quinclorac at 0.6 kg/ha spaced 21 d apart provided better torpedograss control (88%) than two applications at 0.8 kg/ha (69%) or one application at 1.7 kg/ha (69%). Two applications of quinclorac (0.8 kg/ha) plus diclofop (0.8 kg/ha) provided better torpedograss control (82%) than either herbicide applied alone when evaluated after a single season of application. Increasing the mowing interval prior to quinclorac application to allow for more foliage to be present did not improve control. Nitrogen application prior to quinclorac treatment did not improve torpedograss control. Long-term control will most likely require quinclorac applications for more than one season.

Rhizobacteria have been shown to be phytotoxic to leafy spurge in laboratory assays. This field study investigated the influence of two strains of Pseudomonas fluorescens [Trevisan, (Migula)], deleterious rhizobacteria (DRB), on root weight, root bud number, and root carbohydrate content of leafy spurge at three sites located in northeast and north-central South Dakota. Soils were inoculated with 2 g of starch-based granules containing no bacteria or starch granules containing 108colony-forming units (cfu)/g of either bacterial strain LS102 (Montana origin) or LS174 (South Dakota origin). Bacterial strains were detected on root samples from treated areas. Root weight and root carbohydrate content were reduced about 20% compared to roots from control plots.

Field studies were conducted from 1998 to 2000 at Belleville, IL, to evaluate tolerance and weed control in glyphosate-resistant soybean with sulfentrazone application. Sulfentrazone alone caused 14 to 16% height reduction 14 d after treatment (DAT), and sulfentrazone plus chlorimuron caused 26% height reduction 14 DAT. Minimal height reduction (0 to 11%) was observed 56 DAT. Sulfentrazone alone controlled giant foxtail 97 to 100%, yellow nutsedge 96 to 98%, common waterhemp 97 to 98%, common cocklebur 91 to 94%, and ivyleaf morningglory 100%. Sulfentrazone alone controlled common ragweed 63 to 89% and giant ragweed 50 to 72%. Sulfentrazone plus chlorimuron or cloransulam increased control of common and giant ragweed to 95% or greater. Sulfentrazone followed by glyphosate increased control of yellow nutsedge, common waterhemp, and ivyleaf morningglory compared with a single application of glyphosate. Sequential applications of glyphosate controlled weeds 93 to 100%. Sulfentrazone plus chlorimuron or cloransulam postponed the application of glyphosate at the 10-cm weed height by 12 d. Despite the injury, sulfentrazone did not reduce grain yield. Inadequate giant ragweed control reduced grain yield by approximately 48%.

Field studies were conducted from 1991 through 1994 in several locations of Southern Spain to determine the efficacy of imazapyr as late postemergence application in sunflower for broomrape control and the crop response to this herbicide under weed-free conditions. Single applications of imazapyr at 10 to 15 g/ha on sunflower plants at about the V12 (12 leaves) to V19 (19 leaves) growth stages, infected with broomrape plants at the predominant growth stages “c” (small nodule with shoot bud visible) and “d” (shoot bud and roots well developed), resulted in effective control without damaging the crop. Double applications of imazapyr at 10 + 10 g/ha at about the same crop growth stages V12 to V19, at a time interval of 12 to 14 d between single applications, were also efficacious and well tolerated by the crop. The same herbicide treatments applied to weed-free sunflower did not adversely affect the biomass, head diameter or yield of the crop as compared with the nontreated check. As a result of the low rate of imazapyr required for broomrape control, the herbicide treatments are economical (about $3 to $6/ha), non-residual and not affected by the type of soil texture and rainfall conditions.

Atrazine has been used for control of many weeds, primarily broadleaf weeds, in U.S. corn fields since 1957. Recently, the adoption of glyphosate-resistant corn hybrids have led to glyphosate eclipsing atrazine as the most commonly used herbicide in corn production. However, the evolution and spread of glyphosate-resistant weeds is a major concern. Atrazine use in Wisconsin is prohibited in 102 areas encompassing 0.49 million ha where total chlorinated residues were found in drinking water wells at concentrations > 3 μg L−1. Atrazine has been prohibited in many of those areas for > 10 yr, providing an opportunity to evaluate weed community composition differences due to herbicide regulation. In question, has the abundance of broadleaf weeds increased, coupled with an increased reliance on glyphosate, where atrazine use has been discontinued? To answer this, an online questionnaire was distributed to Wisconsin growers in June and then weeds present in 343 fields in late July through mid-September in 2012 and 2013 were counted. Data were summarized for frequency, uniformity, density, and relative abundance to compare weed community composition in fields with discontinued vs. recent atrazine use. Growers used glyphosate in 70 vs. 54% of fields with discontinued vs. recent atrazine use, respectively (P = 0.021). Moreover, broadleaf weeds were found more frequently, (73 vs. 61%; P = 0.03), they had 50% greater in-field uniformity (P = 0.002), and density was 0.4 vs. 0.19 plants m−2 (i.e., twofold greater; P < 0.0001) in discontinued vs. recent atrazine-use fields. Changes were most evident with troublesome glyphosate-resistant broadleaf weeds such as Amaranthus species and giant ragweed. In conclusion, weed community composition consisted of more broadleaf weeds in fields where atrazine has not been used in the recent decade coupled with greater glyphosate use. These results provide evidence of negative long-term implications for glyphosate resistance where growers increased reliance on glyphosate in place of atrazine.

In weed science literature, models such as concentration addition, independent action, effect summation, and the parallel line assay technique have been used to predict and analyze whole-plant response to herbicide mixtures. Although a joint action reference model is necessary for determining whether the herbicide mixture provides less than (antagonistic), equal to (zero-interaction or additive), or greater than (synergistic) expected control, model selection often occurs with little regard to the model's underlying biological assumptions. The joint action models of concentration addition (CA) and independent action (IA) are the appropriate models to consider for analysis of herbicide mixtures of two active components. CA assumes additivity of dose, with herbicides differing only in potency, whereas IA assumes multiplicativity of effects, in which herbicides behave independently and sequentially within the plant. CA and IA predicted mixture responses were computed for a sample mixture data set of mesotrione plus atrazine. IA predicted lower mixture responses than CA; for example, mesotrione at 17.5 g ha−1 + atrazine at 140 g ha−1 was predicted to provide 45% (IA) compared with 53% (CA) control of Palmer amaranth. Joint action claims of synergism and antagonism were shown to be dependent on the reference model selected. Although mesotrione plus atrazine combinations were synergistic under IA assumptions, analysis under CA assumptions indicated mesotrione plus atrazine to be synergistic, additive, and antagonistic according to the selected effective concentration (ECx ) level and fixed-ratio mixture. Because it is not possible to determine the appropriate joint action model on the basis of fit of predicted to observed mixture data, the appropriateness of underlying biological assumptions was considered for the sample mixture data set. Additionally, we provide decision criteria to aid researchers in their selection of an appropriate joint action reference model.

Effects of repeated late-fall applications of the isopropylamine salt of glyphosate at 1.7 kg ae/ha plus 0.5% (v/v) surfactant on adventitious root buds, thickened propagative roots (> 1.3 mm diam), and shoot density of Canada thistle were studied in continuous hard red spring wheat over a 4-yr period. Glyphosate suppressed Canada thistle shoot density more quickly and to a greater extent than thickened root fresh weight or root bud number. A single fall application of glyphosate drastically decreased Canada thistle shoot density for 1 yr after treatment. However, shoot density was the same as the untreated control by 2 yr after a single fall treatment. Two consecutive late-fall applications of glyphosate in 2 yr decreased Canada thistle shoot density 94% in the fall 1 yr after the last treatment. Glyphosate reduced Canada thistle thickened root fresh weight 70% in the first fall 1 yr after a single fall treatment. However, 2 yr after a single fall application of glyphosate, root fresh weight equalled the controls. Two consecutive fall applications of glyphosate reduced thickened root fresh weight 77% 1 yr after the second treatment.

Evolution of glyphosate-resistant (GR) weeds, such as horseweed, presents major challenges in no-till soybean production systems. Effective GR horseweed control with preplant burndown applications is necessary to prevent potential soybean yield losses due to competition and to manage the soil weed seedbank. Halauxifen-methyl is a new synthetic auxin herbicide for broadleaf weed control in preplant burndown applications for soybean and other crops at low use rates (5 g ae ha–1). Experiments were conducted to evaluate the efficacy of herbicide treatments containing halauxifen-methyl for control of GR horseweed in comparison to existing herbicide treatments utilized in no-till GR soybean systems. Glyphosate alone controlled horseweed 33%. Herbicide treatments that included halauxifen-methyl, dicamba, or saflufenacil in combination with glyphosate controlled horseweed 87% to 96%, 89%, and 93%, respectively, 35 d after burndown application (DAB). Horseweed control, horseweed density reduction, and ground cover reduction by halauxifen-methyl plus glyphosate was similar to dicamba plus glyphosate. Horseweed control was greater for halauxifen-methyl plus glyphosate than for 2,4-D plus glyphosate. Cloransulam, cloransulam plus flumioxazin, and cloransulam plus sulfentrazone added to halauxifen-methyl plus glyphosate increased horseweed control and reduced horseweed density. No herbicide injury or soybean yield reduction was observed for treatments containing halauxifen-methyl.

Field experiments were conducted to determine the efficacy of fluazifop-P-butyl for the control of green foxtail, wild oat, barley, and wheat in flax as influenced by spray nozzle orientation, time of day, and growth stage. Under drought conditions in 1988, control of wild oat, wheat, and barley with fluazifop-P-butyl was enhanced 75%, 53% and 78%, respectively, when nozzles were oriented to spray forward 45°. Under adequate soil moisture conditions enhancement of control was minimal. Green foxtail control improved when fluazifop-P-butyl was applied from 1700 to 2100 h, but time of day had no effect on control of wild oat, barley, or wheat. Fluazifop-P-butyl effectiveness was reduced when applied 4 d after flax emergence due to late emerging grass seedlings. Green foxtail was the most tolerant to fluazifop-P-butyl, whereas wild oat, wheat, and barley were the most susceptible.

The grasses or Poaceae (Gramineae) comprise some 9,000 species grouped into about 650 taxa. Although not the largest, the family is ecologically the most dominant and economically the most important in the world (Heywood 1993).

Field studies were conducted at three locations in 1993 and 1994 to evaluate weed control and crop response to combinations of glyphosate, metolachlor, 0.5 X and 1 X label rates of chlorimuron plus metribuzin applied prior to planting (PP), and 0.5 X and 1 X label rates of imazethapyr applied early postemergence (EPOST) or postemergence (POST) in no-till narrow-row soybean production. Giant foxtail densities were reduced with sequential PP followed by (fb) EPOST or POST treatments. Large crabgrass was reduced equivalently with all herbicide combinations involving chlorimuron plus metribuzin PP fb imazethapyr. Common cocklebur control was variable but was usually greater with treatments that included imazethapyr. Ivyleaf morningglory densities were not reduced with any herbicide combinations. Sequential PP fb EPOST or POST treatments tended to provide slightly better weed suppression than PP-only treatments, but the difference was rarely significant. Soybean yields with treatments utilizing 0.5 X rates were usually equal to 1 X rates.