bluuebunny/crossref_metadata_2025 huggingface dataset:
Postemergence Weed Control in Corn (Zea mays) with Nicosulfuron Combinations
Authors: Dobbels Anthony F. , Kapusta George
Published: March 2018

Field studies were conducted at Carbondale and Belleville, IL to evaluate weed control in corn with a total POST herbicide program. Nicosulfuron was applied at 24 and 35 g/ha alone and in combination with 2,4-D, dicamba, bromoxynil, bentazon, atrazine, and bentazon, bromoxynil, and dicamba plus atrazine. Nicosulfuron controlled 98 to 100% of giant foxtail both years at both locations. Control of giant foxtail was reduced when nicosulfuron at 24 g/ha was applied as a tank-mix with atrazine, and with bentazon, bromoxynil, or dicamba plus atrazine at Belleville in 1991. Also, bentazon plus atrazine with nicosulfuron at 35 g/ha reduced control of giant foxtail. Control of common lambsquarters, jimsonweed, and velvetleaf was dependent on nicosulfuron rate, companion herbicide, and growing conditions. Nicosulfuron alone or as a tank-mix with the companion herbicides controlled redroot pigweed 100% at both sites both years but control of yellow nutsedge was less than 50%. Corn yield was related to level of weed control obtained in most instances.
Cheat (Bromus secalinus) Control in Winter Wheat (Triticum aestivum) with Sulfonylurea Herbicides
Authors: Driver Jacquelyn E. , Peeper Thomas F. , Koscelny Jeffrey A.
Published: March 2018

Ten field experiments were conducted in Oklahoma from 1988 to 1992 to evaluate chlorsulfuron plus metsulfuron (5:1 w/w) and triasulfuron for cheat control in winter wheat. Cheat control by chlorsulfuron plus metsulfuron at 18 and 26 g ai/ha varied from 0 to 81% and by triasulfuron at 18 and 30 g ai/ha from 0 to 60%. Grain yield was increased in four experiments and dockage was reduced in five experiments by both rates of chlorsulfuron plus metsulfuron.
Selective Torpedograss (Panicum repens) Control in Bermudagrass (Cynodonspp.) Turf
Authors: McCarty Lambert B. , Higgins Jeffery M. , Colvin Daniel L.
Published: March 2018

Torpedograss has invaded fine turfgrasses in the Southern U.S. due to its tolerance to most commonly used turfgrass herbicides. Research was conducted to determine torpedograss and ‘Tifway’ bermudagrass tolerance to quinclorac and tank-mix combinations with other turf herbicides. Quinclorac rates in excess of 2.2 kg ai/ha were required for control (≥ 80%) of torpedograss. Sequential applications were more effective than single applications. Generally, sequential applications made 3 wk after the initial were more effective than delaying sequential applications until 4 wk after the initial application. Tifway bermudagrass injury from quinclorac applied at 4.5 kg/ha, or at 2.2 kg/ha followed by a sequential application of 1.1 or 2.2 kg/ha, was observed at 4 to 10 wk; however, turf recovered thereafter. Sequential applications of quinclorac plus imazaquin (1.1 + 0.6 kg/ha) increased torpedograss control (approximate 35%) as compared to quinclorac plus MSMA (1.1 + 1.1 kg/ha) but also decreased turf quality versus quinclorac applied alone or in combination with MSMA. Quinclorac applied at 2.2 kg/ha followed by 1.1 kg/ha applied 3 or 6 wk after the initial controlled torpedograss best with least reduction in bermudagrass quality. Quinclorac is the first herbicide reported to selectively control torpedograss in bermudagrass turf.
Woolly Cupgrass (Eriochloa villosa) Control in Corn (Zea mays) with Chloroacetamide Herbicides
Authors: Owen Michael D. K. , Hartzler Robert G. , Lux James
Published: March 2018

Woolly cupgrass control with acetochlor, alachlor, and metolachlor in corn was evaluated at Stratford, IA from 1985 through 1990. Averaged over application techniques, acetochlor at 3.4 kg/ha controlled more than 85% of woolly cupgrass five out of six years, whereas alachlor at 4.5 kg/ha and metolachlor at 3.4 kg/ha controlled more than 85% of this weed one and two years out of six, respectively. Herbicide incorporation did not consistently improve woolly cupgrass control. PRE applications were more effective than incorporated treatments in years with greater than 7 mm rainfall occurring within 3 d after application.
Alternative Weed Management Systems for the Production of Kidney Beans (Phaseolus vulgaris)
Authors: Burnside Orvin C. , Krause Norman H. , Wiens Melvin J. , Johnson Michelle M. , Ristau Eric A.
Published: March 2018

Weed management experiments with kidney beans were conducted at one irrigated site in 1991 and at two irrigated sites near Staples, MN during 1992. Green foxtail was the most difficult weed to control at the three research sites which agrees with survey results from dry bean growers regarding their worst weed problems. Hairy nightshade increased rapidly when weed management methods were reduced. Dry bean seed yields were highest in cultivated check plots on the farmer's field and in conventional practices plots at the Irrigation Research Center. Net economic returns, averaged over 1991 and 1992, for producing kidney beans at the Irrigation Research Center were $899/ha using conventional practices, $791/ha with cover crop practices, $734/ha with cultivated checks, $690/ha with herbicides only, and $208/ha on weedy checks. Kidney beans are an economical crop for North Central growers, but adequate weed management technologies are necessary for profitable production.
Net Returns from Stale Seedbed Plantings of Soybean (Glycine max) on Clay Soil
Authors: Heatherly Larry G. , Wesley Richard A. , Elmore C. Dennis , Spurlock Stan R.
Published: March 2018

Field studies were conducted for three years in each of two successive experiments and analyzed to determine net return from stale seedbed plantings of soybean. Treatments in the first experiment were early May and late May/early June plantings in seedbeds that had combinations of tillage at various times between harvest and planting, incorporation of trifluralin, or no preplant tillage. Treatments in the second experiment were irrigated and nonirrigated stale or no-till seedbed plantings with weed control treatments that included POST cultivation plus combinations of preplant foliar-applied (PFA) glyphosate, PRE metribuzin, and POST herbicides. Results indicate that 1) early planting of soybean resulting from use of a stale seedbed will result in higher net returns when irrigation is used, 2) use of a wheat cover crop does not justify the expense, 3) soybean planted in a no-till seedbed will result in net return similar to that from plantings in fall-tilled, spring-tilled, or prepared seedbeds, 4) use of only a PFA herbicide plus POST cultivation in a stale seedbed planting where competitive weeds such as common cocklebur appear later will result in a significant reduction in net returns, and 5) use of PRE herbicides in conjunction with PFA herbicide and POST cultivation in a stale seedbed planting will result in the highest net return with the least input.
Characterization of Chlorsulfuron Resistant and Susceptible Kochia (Kochia scoparia)
Authors: Thompson Curtis R. , Thill Donald C. , Mallory-Smith Carol A. , Shafii Bahman
Published: March 2018

Kansas and North Dakota kochia populations identified as chlorsulfuron resistant (R) contained 20 and 30% susceptible (S) plants, respectively. Biotypes that were chlorsulfuron R or S were selected from each field R or S collection and selfed through three generations in the greenhouse. Chlorsulfuron at 7.6 and 17.8 g ai/ha suppressed shoot biomass of the Kansas and North Dakota R biotypes by 50%, respectively, which was a 30- and 105-fold greater dose than that required to reduce the respective S biotypes growth 50%. The R and S kochia biotypes are diploid with 2N = 18 chromosomes. Chlorsulfuron resistance is inherited in kochia as a dominant trait controlled by a single nuclear gene. Thus, the resistance trait can be spread by seed and pollen.
Influence of Norflurazon Induced Chlorosis on Bermudagrass (Cynodon dactylon) Hay Production
Authors: Smith Albert E. , McLean Henry
Published: March 2018

Research was conducted in central Georgia to determine the influence of norflurazon on bermudagrass stand and production when applied to newly sprigged bermudagrass and in the spring to dormant bermudagrass. Norflurazon at rates up to 1.12 kg ai/ha on newly sprigged bermudagrass caused moderate chlorosis to the emerging leaves but did not adversely influence stand density or ground cover at 60 and 90 days after treatment (DAT). Norflurazon applied to dormant bermudagrass the spring of 1993 resulted in greater than 50% foliage chlorosis at rates ≥ 1.68 kg/ha. Foliage chlorosis was 94% on bermudagrass treated with 3.36 kg/ha 30 DAT and at spring growth initiation. However, chlorosis level was reduced when bermudagrass began rapid growth. Forage production was not influenced by the early season chlorosis when compared to nontreated areas or areas treated with diuron at 1.12 kg/ha and the weed free check.
Effect of Cover Crop Mulches on Weed Emergence, Weed Biomass, and Soybean (Glycine max) Development
Authors: Moore Monica J. , Gillespie Terry J. , Swanton Clarence J.
Published: March 2018

Field studies were conducted in 1988/89 and 1989/90 at two locations to determine the effect of rye, wheat, and triticale cover crop mulches on weed emergence patterns, weed biomass, and soybean development. Redroot pigweed and common lambsquarters emergence patterns were not altered by mulches. Early in the season, mulches reduced weed biomass; however, the results were inconsistent between locations and years. Under weed-free conditions, the cover crop mulches had no detrimental effects on soybean development and yields were not different from bare soil controls.
Effect of Imazethapyr on Legumes and the Effect of Legumes on Weeds
Authors: Wilson Robert G.
Published: March 2018

A three-year experiment was conducted near Scottsbluff, NE, to evaluate the selectivity of POST-applied imazethapyr for weed control in alfalfa, birdsfoot trefoil, cicer milkvetch, red clover, sainfoin, and yellow sweetclover. Imazethapyr injured all legumes 15 DAT. Imazethapyr also reduced the height of birdsfoot trefoil, cicer milkvetch, red clover, and yellow sweeclover 28 DAT. Legume first cutting yields were not reduced by imazethapyr and with alfalfa, birdsfoot trefoil, cicer milkvetch, and sainfoin, first cutting yields were increased by imazethapyr. Imazethapyr reduced weed biomass in all legume seedings. Weed biomass in new seedings of alfalfa was reduced more than that of the other legumes.
Management of Fringed Sagebrush (Artemisia frigida) in Saskatchewan
Authors: Peat Heather C. , Bowes Garry G.
Published: March 2018

Fringed sagebrush is a native, drought-resistant, increaser species in Saskatchewan pastures and rangelands. Conventional control by cultivating and reseeding is neither highly effective nor sustainable. Two field experiments were conducted in 1988 and 1989 through 1991 to develop a management plan for fringed sagebrush. Comparison of fringed sagebrush control using various applications of clopyralid, dicamba, dichlorprop, fluroxypyr, picloram, triclopyr and 2,4-D, showed control was sufficient using the low-cost herbicide 2,4-D isooctyl ester at 1.5 kg ai/ha. Total yield of crested wheatgrass plus smooth brome was compared and the plots subjected to two applications of 2,4-D yielded the greatest accumulation of grass over the length of the experiments. The economic threshold of fringed sagebrush is the density at which yield is reduced by approximately 290 kg/ha; above this density it is economically viable to use 2,4-D at 1.5 kg/ha to control fringed sagebrush. Grazing practices can aid greatly in management of fringed sagebrush by allowing the forage to out-compete fringed sagebrush.
Relationship of Leaf Position to Herbicide Absorption and Organosilicone Adjuvant Efficacy
Authors: Roggenbuck Frank C. , Burow Richard F. , Penner Donald
Published: March 2018

The absorption of14C-bentazon and14C-acifluorfen by individual leaves of velvetleaf was measured from the cotyledons to the most recently developed leaf in plants that had developed seven leaves beyond the cotyledons. Herbicide absorption 1 min after application was greatly enhanced by the organosilicone adjuvant Sylgard 309 explaining previously observed enhanced efficacy and rainfastness by this adjuvant.14C-herbicide absorption was greatest by the cotyledons and decreased upward to the most recently developed leaf. Absorption of the14C-Sylgard 309 was similar to that of the14C-labelled herbicides and was not related to the number of stomata or leaf area covered by the spray droplets. These results are consistent with the hypothesis that the mode of action of Sylgard 309 is to enhance cuticular absorption and not stomatal infiltration.
Fall Application of Prodiamine for Spring Crabgrass (Digitariaspp.) Control
Authors: Fermanian Thomas W. , Haley Jean E.
Published: March 2018

Fall application of a PRE herbicide offers professional lawncare applicators additional flexibility in scheduling necessary weed control operations. A 3-yr field study was established on common Kentucky bluegrass in Urbana, IL to examine the effectiveness of fall- or spring-applied prodiamine and DCPA for spring large and smooth crabgrass control. Prodiamine was effective for crabgrass control in turf (≥ 91% control) when applied in spring at ≥ 0.4 kg/ha or when it was applied in the fall at ≥ 0.6 kg/ha (≥ 82% control). In most cases, fall-applied prodiamine at the 0.8 kg/ha rate (≥ 91% control) controlled crabgrass as well as spring-applied DCPA at the 11.8 kg/ha rate (≥ 94% control). Little reduction in turf quality (≥ 8.3) occurred when prodiamine was applied in the fall at 0.8 kg/ha or less. Only when prodiamine was applied at 2.2 kg/ha was there significant quality loss (7.3) with spring applications. In a second experiment to evaluate split fall and spring prodiamine applications for crabgrass control, all split applications had 100% crabgrass control which was not significantly different from single applications of ≥ 1.4 kg/ha.
Application of Prodiamine to Immature Turfs
Authors: Fermanian Thomas W. , Haley Jean E.
Published: March 2018

Turf managers use prodiamine to control annual grasses in mature turfs. Earlier, evaluations of prodiamine have indicated it has an elevated soil persistence and high activity on susceptible species. This persistence raises concern for prodiamine's effect on juvenile turf. An experiment was established to evaluate the effect of prodiamine on juvenile Kentucky bluegrass turf. Significant loss of quality occurred on turf less than one year old receiving a single application of prodiamine at ≥ 1.4 kg/ha. Split applications of prodiamine did not significantly decrease turf quality. Prodiamine at 0.8 and 2.2 kg ai/ha and DCPA at 23.5 kg ai/ha, applied in the fall the previous three years, significantly reduced the number of overseeded Kentucky bluegrass seedlings two years after planting. In a subsequent study, prodiamine at ≥ 0.8 kg/ha and DCPA at 23.5 kg/ha applied once the previous fall significantly reduced the number of overseeded Kentucky bluegrass dlings 56 d after planting. An analysis of prodiamine rate versus seedling density was found to be significantly correlated (r2= 0.79).
Are Herbicide mixtures useful for Delaying the Rapid Evolution of Resistance? a Case Study
Authors: Wrubel Roger P. , Gressel Jonathan
Published: March 2018

Mixtures of herbicides have been proposed as strategies to prevent or delay the evolution of resistance to the resistance-prone sulfonylurea and imidazolinone herbicides that inhibit acetolactate synthase. These herbicides have become or are becoming widely used in soybean, wheat, rice, and other major crops. For a mixture to be efficacious in preventing resistance, the less resistance-prone component(s) should have the following traits compared to the vulnerable herbicide: a) control the same spectra of weeds; b) have the same persistence; c) have a different target site; d) be degraded in a different manner; and e) preferably exert negative cross-resistance. We compared the proposed mixing partners for use with several widely used acetolactate synthase inhibiting herbicides to these criteria and found that: a) all have somewhat different weed spectra; e.g. none control common cocklebur as well as imazaquin or imazethapyr in soybean, or kochia as well as chlorsulfuron in winter wheat; b) all are far less persistent than these vulnerable herbicides. Less persistent sulfonylureas are now on the market but are in limited use. Late in the season, the mixing partner is not present while the vulnerable herbicide remains active; c) most have different target sites; d) in soybean most mixing partners are degraded differently than vulnerable herbicides. In wheat virtually all herbicides used without safeners are degraded by monooxygenases, thus it is impossible to meet this criterion in this crop; e) none of the mixing partners exert negative cross-resistance. The present mixtures may have superior or more cost-effective weed control properties than the acetolactate synthase inhibitors used alone, but they do not meet all the criteria for resistance management. Not meeting the key criteria of identical control spectra and equal persistence aggravates future resistance problems, as has happened with insecticides.
Effect of Organosilicone Surfactants on the Rainfastness of Primisulfuron in Velvetleaf (Abutilon theophrasti)
Authors: Sun Jinxia , Foy Chester L. , Witt Harold L.
Published: March 2018

Greenhouse experiments were conducted to evaluate the influence of three organosilicone surfactants (Silwet L-77®, Silwet® 408, and Sylgard® 309) and two blends of organosilicone surfactants with conventional adjuvants (Dyne-Amic® and Kinetic®) on the rainfastness of primisulfuron in velvetleaf. Four conventional adjuvants, Rigo Oil Concentrate, Agri-Dex®, methylated soybean oil, and X-77® were selected for comparison. Primisulfuron at 40 g ai/ha was applied alone or with the organosilicones, blends, or X-77 at 0.25% (v/v); the other adjuvants were tested at 1% (v/v). Simulated rainfall (1.25 cm/0.5 h) was applied at 0.25, 0.5, 1, or 2 h after treatment. Control ratings were made at 5-d intervals and shoot fresh weights were recorded 20 DAT. The organosilicone surfactants significantly increased the rainfastness of primisulfuron, even when simulated rainfall was applied at 0.25 or 0.5 h after treatment. Rigo Oil Concentrate and Kinetic also increased rainfastness when rainfall was applied 1 h after treatment. Differences among adjuvants were not as apparent when rainfall was applied 2 h after treatment. Regardless of the timing of simulated rainfall after treatment, there were significant differences between treatments and nontreated check; however, control was not acceptable in several instances.
Effect of Growth Stage and Application Site on Tolerance of Rice (Oryza sativa) to Haloxyfop
Authors: Baldwin John L. , Coats G. Euel , Street Joe E. , Langston Vernon B.
Published: March 2018

Greenhouse experiments were conducted to evaluate seedling rice tolerance to haloxyfop and to determine soil moisture effects on root, shoot, and root plus shoot uptake. Visible injury to rice at 4 wk after treatment increased with each increase of haloxyfop rate from 40 to 160 g ai/ha, regardless of growth stage. Less injury was observed at equivalent rates in four-leaf than in younger rice. Similarly, equivalent haloxyfop rates reduced shoot fresh weight of one- to three-leaf rice more than shoot fresh weight of four-leaf rice. There was no interation between soil moisture levels (19 and 24%) and haloxyfop activity. Fresh weights were less when haloxyfop at 40 or 80 g/ha was absorbed by both roots and shoots than when absorption was by either roots or shoots alone. However, at 80 g/ha fresh weight was similar whether haloxyfop was absorbed by roots or shoots alone. Root uptake, in the presence of 160 g/ha haloxyfop, did not contribute to reduced fresh weight with root plus shoot treatments because of the initial foliar activity incurred.
Nitrogen Application Timing Effects on Downy Brome (Bromus tectorum) and Winter Wheat (Triticum aestivum) Growth and Yield
Authors: Ball Daniel A. , Wysocki Donald J. , Chastain Thomas G.
Published: March 2018

Field studies were conducted for two years at two locations near Pendleton and Moro, OR to evaluate the influence of single sub-surface nitrogen (N) fertilizer application timings and multiple N applications on downy brome and winter wheat growth and yield. N applications in fallow, at planting, during the crop season, and several split N application timings were compared to evaluate downy brome interference in winter wheat. N application rates varied between locations as a function of average annual precipitation and accepted agricultural practice. Pendleton and Moro were considered high and low precipitation sites, respectively. At Pendleton in a year of above average precipitation, N applied at planting, in-crop, or split applications of N with part of N applied at planting and part in-crop, increased downy brome dry matter production compared to N applied in fallow. Downy brome infestation eliminated otherwise positive wheat yield benefits of split N application compared to the conventional commercial practice of N application in fallow. In a year of moderate precipitation, N applications at planting, in-crop, or split N applications did not benefit wheat yield compared to N application in fallow, but downy brome dry matter was increased. In a dry season, N rates and timings did not increase downy brome dry weight or wheat grain yield. In the absence of downy brome, alternative N application techniques increased wheat yield only under high growing season precipitation.
Spring-Planted Winter Rye (Secale cereale) as a Living Mulch to Control Weeds in Soybean (Glycine max)
Authors: Ateh Comfort M. , Doll Jerry D.
Published: March 2018

The effects of rye planting time, rye seeding rate, and rye/weed management systems on weed control and soybean yield were determined in field experiments near Arlington, WI from 1992 to 1994. Insufficient precipitation in 1992 resulted in limited soil moisture, less ground cover, less weed control, and lower soybean yields than in 1993 and 1994. The higher rye seeding rate provided more ground cover and better weed control than the lower rate in all years; however, it reduced soybean vigor. The optimum rye seeding rate was 112 kg/ha. The rye-only system reduced weed shoot biomass by 90, 82, and 60%, in 1992, 1993, and 1994, respectively, relative to the no-rye weedy check treatment. Killing rye 45 d after planting soybean gave optimum weed control. In 1993, rye alone suppressed the weeds without decreasing crop yield, but in 1994 crop yield was decreased due to inadequate weed control by rye. The results indicate that the rye living mulch technique can adequately control weeds without causing soybean yield reduction if weed pressure is low, ground cover and soil moisture are adequate and rye interference is minimal.
Adjuvants and Growth Stage Affect Purple Nutsedge (Cyperus rotundus) Control with Chlorimuron and Imazethapyr
Authors: Jordan David L.
Published: March 2018

Chlorimuron and imazethapyr applied with nonionic surfactant, crop oil concentrate, or organosilicone-based adjuvant were evaluated for purple nutsedge control in the field. Additional experiments compared chlorimuron and imazethapyr control of purple nutsedge when applied with crop oil concentrate at two growth stages. Chlorimuron controlled purple nutsedge better than did imazethapyr in most experiments. Chlorimuron performed better when applied with crop oil concentrate than with nonionic surfactant or organosilicone-based adjuvant. Imazethapyr control with the organosilicone-based adjuvant or crop oil concentrate was similar and greater than imazethapyr with nonionic surfactant. Control was greater when herbicides were applied to 2- to 6-cm tall purple nutsedge compared with plants 8 to 10 cm tall in two of three trials.
Impact of Alien Plants on Grant Basin Rangelands
Authors: Young James A. , Longland William S.
Published: March 2018

Our purpose is to discuss the impact of alien plants on rangeland ecosystems of the Great Basin in terms of their effects on biological functions. The sagebrush/bunchgrass ranges of western North America are used as a model ecosystem for the impact of alien plants. Alien weed species have been introduced in successive waves, with the success of each new introduction dependent on how well adapted to the environment and how competitive the new weed is with those previously introduced. Annual species have been successful across extensive areas of Great Basin rangelands. Biennial and short- and long-lived perennial introductions have been restricted to much more specific habitats. Alien plants impact rangelands through stand renewal and successional processes. Alien weeds can cause such processes to be accelerated and/or truncated depending on the species and range site.
Imidazolinone Herbicides Improve Restoration of Great Plains Grasslands
Authors: Masters Robert A. , Nissen Scott J. , Gaussoin Roch E. , Beran Daniel D. , Stougaard Robert N.
Published: March 2018

The productivity and native species diversity of Great Plains grasslands have been substantially reduced by past management that facilitated the establishment of invasive exotic weeds and displacement of native species. Management strategies are needed to rapidly restore the productive capacity and biological diversity of these degraded grasslands. Critically important phases of the grassland restoration process are the reintroduction and establishment of native species. Weed interference is the primary constraint to successful establishment of native plants. The goal of our research is to develop strategies that use multiple technologies, including herbicides, to expedite grassland revegetation with native grasses and forbs. Imidazolinone herbicides (AC 263,333, imazapyr, and imazethapyr) were used successfully to improve establishment of native perennial grasses (big bluestem, switchgrass, little bluestem) and selected forbs (blackeyed-susan, purple prairieclover, Illinois bundleflower, trailing crownvetch, and upright prairie coneflower) on cropland and as components of a strategy to revegetate leafy spurge-infested rangeland with native tallgrasses. Imazethapyr at 70 or 110 g ai/ha applied at planting resulted in stands of big bluestem and little bluestem that were similar or superior to stands established where atrazine was applied. Seedling grasses were susceptible to imazapyr at two of three study sites. Imazapyr at 560 g ai/ha plus sulfometuron at 100 g ai/ha applied in fall was the optimum treatment for suppression of leafy spurge and exotic cool-season grasses and establishment of big bluestem and switchgrass on degraded rangeland sites. Establishment of selected forbs was improved by PRE treatment with AC 263,222 or imazethapyr at 70 g ai/ha. This research provides evidence that the imidazolinone herbicides can be important components of integrated weed management strategies designed to reverse deterioration of grasslands by reestablishing native species, improving grassland productivity, and decreasing the prevalence of exotic weeds.
Detection of Yellow Starthistle (Centaurea solstitialis) and Common St. Johnswort (Hypericum perforatum) with Multispectral Digital Imagery
Authors: Lass Lawrence W. , Carson Hubert W. , Callihan Robert H.
Published: March 2018

Ground-based surveys to regularly document the size, shape, and location of weed populations usually are not economically feasible. Digital images of vegetation in semiarid rangeland were obtained from four charge-coupled devices with spectral filters mounted in an airplane. The ability to distinguish yellow starthistle and common St. Johnswort from other rangeland vegetation in images with 0.5, 1, 2, and 4 m spatial resolution was assessed. Detection, positioning, and measurements of size and density of yellow starthistle and common St. Johnswort colonies with densities as low as 30% ground cover were possible at all those resolutions. Images indicated yellow starthistle occupied about one-third of a 180-ha study area. Images taken in June indicated 2 to 10 ha less yellow starthistle ranging from 30 to 100% cover than images taken in July for all resolutions. Images indicated common St. Johnswort occupied less than 4 ha of the 180-ha study area. This procedure provides a method to establish baseline plant community composition and a way to monitor species population changes and dispersal over time.
Weed Control in Ecofallow Corn (Zea mays) with Clomazone
Authors: Wicks Gail A. , Mahnken Gary W. , Hanson Gordon E.
Published: March 2018

Field studies were conducted from 1986 through 1989 to determine the feasibility of using clomazone in a winter wheat-corn-fallow rotation. Clomazone at 1.1 kg ai/ha did not control emerged downy brome in autumn nor did it control redroot pigweed and tumble pigweed that emerged after a spring application of paraquat at 0.6 kg ai/ha. However, clomazone plus atrazine at 0.6 plus 2.2 kg ai/ha provided weed control in winter wheat stubble from October to corn harvest 12 mo later. Corn yields from this treatment were equal to or greater than the conventional practice of applying atrazine plus glyphosate at 2.2 plus 0.4 kg ae/ha in the fall followed by a spring application of metolachlor plus dicamba at 2.8 ai plus 0.3 kg ae/ha. When kochia densities were high, clomazone plus atrazine controlled triazine-resistant kochia better than metolachlor plus dicamba. Atrazine at 2.2 kg/ha applied in autumn followed by clomazone at 0.8 kg/ha in April generally caused more corn injury than when the same rate of clomazone was applied in autumn with the atrazine. The percent of bleached corn plants varied with planter, year, time of application, and rate of clomazone applied. The optimum time to apply clomazone at 0.6 kg/ha was in autumn with atrazine. This treatment caused some corn bleaching but produced the highest corn yield over 3 yr. In a dry autumn and spring, less clomazone injury occurred with a planter equipped with row cleaners than those without. The injury pattern associated with planters was inconsistent when precipitation was average and no injury occurred in a wet autumn and spring.
Response of Dry Edible Bean (Phaseolus vulgaris) Cultivars to Four Herbicides
Authors: Urwin Carl P. , Wilson Robert G. , Mortensen Dave A.
Published: March 2018

Dry edible bean tolerance to PPI-applied EPTC, alachlor and POST-applied imazethapyr was evaluated over two years at Scottsbluff, NE. Eight market classes of dry edible beans comprising 12 cultivars were studied. Crop tolerance was assessed by measuring crop injury, stand, leaf area index, leaf chlorosis, plant canopy volume, projected canopy cover, crop maturity, and seed yield. Leaf area index measured late in the growing season provided the best correlation with seed yield in both years. In 1993 and 1994, imazethapyr treatment caused crop injury, which resulted in a decrease of leaf area and in 1994 decreased seed yield. Differences in herbicide tolerance existed between market classes and cultivars, although the level of herbicide tolerance varied between years.
Kochia (Kochia scoparia) Interference with Oat (Avena sativa)
Authors: Manthey Frank A. , Hareland Gary A. , Zollinger Richard K. , Huseby Donna J.
Published: March 2018

A field experiment was conducted over five years to determine the effect of season-long kochia interference on oat yield and quality. Kochia interference did not affect oat height, test weight, 500-kernel weight, or groat percentage. Similarly, ash, starch, and total β-glucan percentages in oat groat were not affected by kochia interference. Oat grain yield was reduced in 1991 and 1994 by 30 kochia plants/m2, the highest density. Lipid and protein content were not affected by kochia except in 1992 where protein content was reduced and lipid content was increased by kochia.
Timing and Measurement of Weed Seed Shed in Corn (Zea mays)
Authors: Forcella Frank , Peterson Dean H. , Barbour James C.
Published: March 2018

In west central Minnesota the extent and duration of weed seed shed was measured for two years in corn that received cultivation but no herbicides. Percentage of seed production represented by viable (filled) seeds was about 79% for green foxtail, 68% for wild mustard, 49% for Pennsylvania smartweed, 48% for common lambsquarters, and 35% for redroot pigweed. Percentage viable seeds varied from 11% in 1993 to 59% in 1994 for redroot pigweed, but was more stable for other species. Seed shed commenced in late August in a cool year (1993) and early August in a warm year (1994). Average growing degree days (base 10 C) from corn planting until 25% seed shed was 983 for common lambsquarters, 984 for wild mustard, 1004 for Pennsylvania smartweed, and 1034 for both green foxtail and redroot pigweed. Brief weather events, such as wind storms, dispersed large percentages of total seed production within a single day. More than one-fifth of all viable seeds of green foxtail, redroot pigweed, and common lambsquarters were retained by the seedheads and dispersed by combines at harvest. In contrast, seeds of early-maturing species, such as wild mustard, were completely dispersed before corn harvest in the warmer year, but one-third of seeds were retained by seedheads at harvest in the cooler year. Measurement of seed shed was compared using five seed trap designs. The preferred design consisted of a 10-cm-diam plastic cup, whose bottom was replaced by a brass screen, and the entire unit attached to a small wooden stake for support. This design provided, on average, the highest estimates of seed production, least among-replication variability, highest correlation with weed population density and aboveground dry-weight, lowest assembly cost, and greatest ease for sample access and seed processing.
Rhizobacteria as Biocontrol Agents of Weeds
Authors: Kremer Robert J. , Kennedy Ann C.
Published: March 2018

There is a current need to develop alternative weed management techniques in response to demands for reduction in herbicide use due mainly to health and environmental concerns. Therefore, all possible nonchemical strategies for weed control should be considered, including biological control. Deleterious rhizobacteria (DRB), largely overlooked as potential biological control agents for weeds until recently, are able to colonize root surfaces of weed seedlings and suppress plant growth. Limited field studies indicate that DRB suppressed weed growth, and reduced weed density, biomass, and seed production. In this manner, crops out-compete the suppressed weeds for growth requirements, eliminating the necessity for eradication of weeds in the crop. Establishment of DRB as a viable biological control strategy initially will require integration with other weed control approaches including other biocontrol agents, agrichemicals, and cultural and residue management practices. To achieve success, more in-depth research is needed on ecology of bacteria-plant relationships, mechanisms of action (including characterization of phytotoxins), inocula formulations, and methods to enhance crop competition.
Temperature and Photoperiod Effects on Onionweed (Asphodelus fistulosus) and Its Potential Range in the United States
Authors: Patterson David T.
Published: March 2018

Environmental factors that affect the growth and development of onionweed were evaluated in order to predict its potential range and impact in the U.S. In controlled-environment experiments, onionweed achieved 60 to 100% of its maximum vegetative growth at temperatures ranging from 18/11 to 30/23 C day/night. The greatest biomass was produced at day temperatures of 18 or 24 C and night temperatures of 11 or 17 C. Leaf production and reproductive development were greatest at 18/11 C. Plants eventually flowered also at 18/17, 24/17, and 24/11 C but not in any regime with a 30 C-day or a 23 C-night. Flowering occurred earlier in 16-h photoperiods than in 16-h photoperiods than in 8-h photoperiods. Climatic analyses revealed no U.S. analogs of the principal Australian onionweed sites. Based on its environmental responses and its pattern of distribution as a weed in Australia, onionweed will likely remain confined to the southwestern U.S.
Mechanical and Chemical Control of Cogongrass (Imperata cylindrica)
Authors: Willard Thomas R. , Shilling Donn G. , Gaffney James F. , Currey Wayne L.
Published: March 2018

Field studies were initiated in 1985 and 1986 to evaluate the effects of dalapon, glyphosate, imazapyr, and sulfometuron applications to established cogongrass alone or in combination with either mowing or discing. Mowing and discing treatments were performed 4 mo before and 8 months after the herbicide treatments in the 1985 experiments and 2 months before and 7 months after the herbicide treatment in the 1986 experiments. When applied alone, glyphosate at 3.4 kg ai/ha and imazapyr at 0.8 kg ai/ha caused the greatest reduction in shoot and rhizome biomass about 2 yr after application. However, the rhizome infestation was reduced only 43% by glyphosate and 51% by imazapyr, as compared to the nontreated control. With no herbicide, two mowing or discing were generally more effective than a single mowing or discing treatment. The reduction in shoot and rhizome biomass for two mowing without herbicide was 65 and 38% and for two discing, 73 and 66%, respectively. Acceptable (> 80%) levels of cogongrass control, based on reductions in rhizome biomass occurred only when applications of dalapon, glyphosate, or imazapyr were made in combination with two discing despite the fact that mowing before and after treatment reduced shoot biomass by at least 89%.
Highbush Blackberry (Rubus argutus) Control in Bahiagrass (Paspalum notatum)
Authors: McCarty Lambert B. , Colvin Daniel L. , Higgins Jeffery M.
Published: March 2018

A 3-yr study investigated highbush blackberry control in bahiagrass turf using selective herbicides. Triclopyr applied alone at ≤ 0.56 kg/ha and in combination with other herbicides provided best (75 to 95%) control for up to 52 wk after treatment with minimal damage to bahiagrass turf. Triclopyr formulations (3A vs 4EC) provided similar highbush blackberry control and bahiagrass tolerance. The addition of either 2,4-D, dicamba, hexazinone, or sulfometuron to triclopyr provided slightly better blackberry control, but increased bahiagrass turf damage. Fluroxypyr applied at 0.14 to 0.28 kg/ha provided 60 to 80% control of highbush blackberry 12 WAT. Glyphosate and glufosinate treatments provided unacceptable highbush blackberry control and/or unacceptable bahiagrass turf injury. The addition of oxadiazon for residual control of subsequent highbush blackberry emergence was ineffective.
Broadleaf Weed Control in Soybean (Glycine max) with Sulfentrazone
Authors: Vidrine P. Roy , Griffin James L. , Jordan David L. , Reynolds Daniel B.
Published: March 2018

Experiments were conducted at three locations in Louisiana from 1992 to 1994 to evaluate broadleaf weed control with sulfentrazone. Sulfentrazone at 0.42 kg ai/ha applied PPI or PRE provided at least 93% control of entireleaf morningglory in all years at all locations, which was greater than control with metribuzin PRE. Prickly sida control with sulfentrazone ranged from 83 to 94%, which was equal to or greater than control with metribuzin. Hemp sesbania and sicklepod control with sulfentrazone was unacceptable (≤75%) regardless of application method and generally was lower than control with metribuzin. Greater than 90% control of smellmelon and hophornbeam copperleaf was observed with all treatments. Minor but transient soybean injury was noted at one location in one year. Soybean yields following sulfentrazone PRE at St. Joseph were greater than yields with metribuzin as a result of the general increase in broadleaf weed control.
A Theoretical Framework for Developing Successional Weed Management Strategies on Rangeland
Authors: Sheley Roger L. , Svejcar Tony J. , Maxwell Bruce D.
Published: March 2018

Sustainable rangeland management will require successional strategies to deal with the expanding weed problem. These strategies must be consistent with the view that plant communities are dynamic and technology is used to enhance the natural processes and mechanisms that direct vegetation change. The goal is to shift the dynamics toward a desired plant community. A unified conceptual model is necessary to direct the development and application of successional weed management systems. We propose using a resource management model as a conceptual basis for successional weed management. This model is based on the primary causes of succession: site availability, differential species availability, and differential species performance. This model provides the mechanistic framework necessary for developing successional weed management systems and it is meant to enhance communication among rangeland weed managers and scientists.
Broomrape (Orobanche crenata) Control with Imazethapyr Applied to Pea (Pisum sativum) Seed
Authors: Jurado-Expósito Montserrat , Castejón-Muñoz Mercedes , García-Torres Luis
Published: March 2018

Studies were conducted from 1993 through 1995 to determine broomrape control from imazethapyr applied to pea seeds. Soaking seeds for 1 to 10 min in 0.0001% to 1% imazethapyr (Pursuit-10) solutions or coating seeds with imazethapyr at 0.025 to 0.30 mg/g (herbicide/seed, equivalent to 5 to 60 g/ha for a seeding rate of 200 kg/ha) did not affect seed germination or crop emergence and growth. Broomrape control with imazethapyr applied by coating seed at 0.1 to 0.2 mg/g (herbicide/seed, 20 to 40 g/ha) or by soaking seeds for 5 min in 0.1% to 1% imazethapyr solution was from 75 to 80% and 50 to 70%, respectively. Pea biomass and seed yield increased, compared to broomrape-infested nontreated control, when pea seeds were treated with imazethapyr and imazapyr at 5 g/ha was applied late postemergence, as a result of the excellent broomrape control.
A Relational Database as Decision Support System in Chemical Weed Control
Authors: Stigliani Lucia , Santospirito Giuseppe , Cardinale Nicola , Resina Cosimo
Published: March 2018

Decision making in weed control is complex and time-consuming. Moreover, the structure of the available information does not facilitate the comparison of different herbicides. Indeed, information format can be the limiting factor in the performance of sophisticated computer programs intended to supply appropriate advice on weed control treatments. A relational database for decision support on chemical weed control has been developed. It uses a detailed structure by subdividing the information where possible. The database includes programs for entering, updating, and printing data, as well as programs for retrieving information and giving treatment advice. The information access on herbicides is organized around searches based on a specific crop and multiple weed species at their respective growth stages. Optimization of the selected herbicides is carried out and supplies the lowest number of herbicides controlling all the chosen weeds. Information on critical parameters for herbicide application such as varietal restrictions, rotational crops, and compatibility with other products is also interactively available.
Effect of AC 263,222, Imazethapyr, and Nicosulfuron on Weed Control and Imidazolinone-Tolerant Corn (Zea mays) Yield
Authors: Monks C. Dale , Wilcut John W. , Richburg John S. , Hatton Joseph H. , Patterson Michael G.
Published: March 2018

Imidazolinone herbicides injure currently available commercial field corn cultivars; however, cultivars resistant to these herbicides have been developed. Sicklepod, Texas panicum, and annual morningglory control using AC 263,222 (36 and 72 g ai/ha), imazethapyr (36 and 72 g ai/ha), or nicosulfuron (35 g ai/ha) applied POST at 2,4, and 6 wk after planting were evaluated in imidazolinone-tolerant corn. Studies were conducted at Attapulgus and Plains, Georgia from 1992 through 1993. Nicosulfuron and AC 263,222 at 72 g/ha controlled Texas panicum at least 87% when applied 2 wk after planting. Imazethapyr did not consistently control Texas panicum or sicklepod, regardless of application rate. AC 263,222 at both rates and nicosulfuron controlled sicklepod at least 86% when applied 2 wk after planting; however, later application or application under dry conditions generally resulted in reduced control. All herbicides controlled the entireleaf and pitted morningglory complex at least 84% when applied 2 wk after planting. Imidazolinone-tolerant corn was tolerant to all herbicides, regardless of rate and timing, and generally yielded greater when weeds were controlled early in the season.
Dicamba Antagonizes Grass Weed Control with Imazethapyr by Reducing Foliar Absorption
Authors: Hart Stephen E. , Wax Loyd M.
Published: March 2018

Greenhouse and laboratory studies were conducted to determine the effects of tank-mixing the sodium salt of dicamba (Na-dicamba) with imazethapyr on the efficacy and foliar absorption of imazethapyr, applied with non-ionic surfactant (NIS) or methylated seed oil (MSO), by shattercane, giant foxtail, and large crabgrass. The effects of various salt formulations of dicamba and the addition of ammonium sulfate on efficacy,14C-absorption and on foliar spray retention by the same species were also evaluated. Na-dicamba antagonized imazethapyr efficacy by reducing14C-absorption. Using MSO instead of NIS prevented antagonism when Na-dicamba was applied at 70 and 140 g/ha and reduced the severity of the antagonism at greater application rates by greatly increasing14C-absorption compared to NIS. Reductions in14C-absorption and spray retention were due to the salt formulations of dicamba rather than the parent acid. The addition of ammonium sulfate prevented dicamba antagonism of imazethapyr toxicity to grassy weeds by maintaining14C foliar absorption and spray retention at normal levels.
Dose-Responses of Weeds and Winter Wheat (Triticum aestivum) to MON 37500
Authors: Geier Patrick W. , Stahlman Phillip W.
Published: March 2018

Greenhouse studies determined the dose-responses of cheat, downy brome, Japanese brome, jointed goatgrass, and winter wheat to preplant-incorporated MON 37500 and its residual effects on kochia. Concentrations of MON 37500 up to 60 ppbw did not affect winter wheat. MON 37500 did not prevent weed emergence, but increasingly inhibited weed growth as the dose was increased up to about 20 ppbw. GR50values were 16, 16, 11, and 31 ppbw for cheat, downy brome, Japanese brome, and jointed goatgrass, respectively. Japanese brome was more susceptible than cheat or downy brome, and jointed goatgrass tolerated two to three times more MON 37500 than theBromusspecies. Plant dry weights of kochia seeded after removal of the winter annual grasses decreased with increasing initial MON 37500 concentrations up to 20 ppbw. Kochia density was influenced by which winter annual grass was grown previously.
Efficacy of KIH-2023 in Dry- and Water-Seeded Rice (Oryza sativa)
Authors: Braverman Michael P. , Jordan David L.
Published: March 2018

Efficacy of KIH-2023 applied POST at rates of 15 to 40 g ai/ha was evaluated in dry-seeded and water-seeded rice production in 1994 and 1995. Purple ammannia, ducksalad, and Indian jointvetch control with KIH-2023 was similar, and alligatorweed control was greater with KIH-2023 compared with propanil or tank mixtures of propanil plus thiobencarb in water-seeded rice. Barnyardgrass was controlled similarly with KIH-2023 and sequential applications of propanil in dry-seeded rice. Rice yields generally reflected differences in weed control, with yields of rice treated with KIH-2023 similar to sequential propanil applications or propanil plus thiobencarb in dry-, and water-seeded rice, respectively. Minor rice foliar and root injury were noted with KIH-2023.