bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of Ivyleaf Morningglory (Ipomoea hederacea) to Neighboring Plants and Objects
Authors: Price Andrew J. , Wilcut John W.
Published: December 2007

Field observations of morningglory (Ipomoeaspp.) showed that many plants grew out from places of comparable competitive advantage (alleys in field experiments with little or no vegetation) into neighboring plants or structures that provided climbing support. Of 223 native morningglory plants growing in rows and row middles in a 121-m2area within established corn research plots that contained no other weeds, 68% of the mature plants climbed up corn. More significant, of the 152 climbing morningglory plants, 96% grew toward and climbed the row in its closest proximity instead of growing across the row middle. Greenhouse and field experiments were initiated to determine whether morningglory grew preferentially toward certain colored structures or corn plants. Greenhouse-grown ivyleaf morningglory displayed varying frequency in locating and climbing toward black (17%), blue (58%), red (58%), white (67%), green (75%), and yellow (75%) stakes or corn (92%). Pots containing black stakes had the fewest climbing morningglory plants. In the field study, fewer ivyleaf morningglories climbed black structures compared with white- or green-colored structures or corn. The morningglory initial planting distance from colored structures or corn was also significant in the percentage of ivyleaf morningglories that exhibited climbing growth and in its final weight; morningglories that successfully located and climbed structures or corn weighed more and produced more seed than morningglories that remained on the ground. Ivyleaf morningglory appears to respond to spatial distribution of surrounding objects and possibly uses reflectance to preferentially project its stems toward a likely prospective structure for climbing.
Comparisons Between X-ray Film- and Phosphorescence Imaging-Based Autoradiography for the Visualization of Herbicide Translocation
Authors: Wehtje Glenn , Miller Michael E. , Grey Timothy L. , Brawner William R.
Published: December 2007

Autoradiography is a radioisotope-based technique that allows absorbed and translocated herbicide to be visualized. Autoradiographs are traditionally produced with X-ray film and exposure times of several weeks. Phosphorescence imaging (PI) was investigated as an alternative autoradiography procedure. Smallflower morningglory plants were root-exposed to a series of14C-atrazine concentrations, producing a series of increasing foliar radioactivity concentrations (i.e., dosage) that ranged from marginal to excessive with respect to autoradiography. Autoradiographs were subsequently produced from these14C-atrazine-dosed plants using both the X-ray film and the PI technique. Autoradiographs from both techniques were of excellent quality and nearly identical when the dosage was ∼20 to 70 Bq/mg. However, PI produces an acceptable image in dosages either above or below this optimum range. A 1-d exposure time was sufficient with PI, and longer exposure times were not detrimental to image quality. In contrast, a 3-wk exposure time was required with X-ray film. Autoradiographs of selected herbicides are presented to further demonstrate the utility of PI.
Tolerance of Selected Advanced Cowpea (Vigna unguiculata) Breeding Lines to Fomesafen
Authors: Burgos Nilda R. , Brandenberger Lynn P. , Stiers Erin N. , Shivrain Vinod K. , Motes Dennis R. , Wells Linda , Eaton Steve , Martin Larry W. , Morelock Teddy E.
Published: December 2007

Chemical options for weed control in commercial cowpea production are limited. Repeated long-term use of the acetolactate synthase (ALS) inhibitor, imazethapyr, has resulted in selection for ALS-resistant populations of Palmer amaranth. Experiments were conducted at Bixby, OK, and Kibler, AR, from 2001 to 2003 to evaluate the tolerance of cowpea cultivars and advanced breeding lines to fomesafen, a potential alternative for controlling ALS-resistant Palmer amaranth and other problematic broadleaf weeds. Eight commercial cultivars and 42 advanced breeding lines were entered in the preliminary screening, using 0.84 kg/ha fomesafen. Six breeding lines were selected for the first replicated trial and three (00-582, 00-584, and 00-609) were advanced to across-location experiments. Fomesafen doses of 0, 0.17, 0.34, and 0.67 kg/ha were tested across locations. ‘Early Scarlet’ was used as commercial standard. The advanced lines had equal or higher yield potential (1,182 to 1,936 kg/ha) than Early Scarlet (1,108 kg/ha) across locations. Of the cultivars tested, line 00-609 was the best yielder, whereas 00-584 had the highest tolerance to fomesafen. At the commercial fomesafen rate of 0.34 kg/ha, 00-584 had higher yield (974 and 1,735 kg/ha, respectively, at Bixby, OK, and Kibler, AR) than the nontreated, weed-free, Early Scarlet. Thus, fomesafen can be used on the tolerant line, 00-584, without reducing yield potential relative to Early Scarlet.
POST Weed Control Using Halosulfuron in Direct-Seeded Watermelon
Authors: Shrefler James W. , Brandenberger Lynn P. , Webber Charles L. , Roberts Warren , Payton Mark E. , Wells Lynda K.
Published: December 2007

Watermelon growers rotate crops to prevent problems, but weed populations in new fields may hold unexpected control challenges. Having effective POST herbicides would provide growers an opportunity to respond to emerging weeds on an as-needed basis. To address this need, field studies were conducted over 4 yr in Oklahoma to determine efficacy and crop response of POST halosulfuron applications to direct-seeded watermelon that received PRE application of ethalfluralin at 840 g/ha. At 5 wk after crop emergence (WAE) halosulfuron was applied at 18, 27, 36, and 54 g/ha. The 27 g/ha rate was also applied at 1, 2, 3 and 7 WAE. Halosulfuron applications made 5 WAE did not provide acceptable (> 80%) control of pigweeds and cutleaf groundcherry regardless of rate. Applications made 1 WAE provided significantly better control of pigweeds and cutleaf groundcherry than did later applications. Halosulfuron treatments of 36 and 54 g/ha made 5 WAE and of 27 g/ha made 1, 2 and 3 WAE did not result in significant yield increases compared with the hand-weeded check. These studies show that POST halosulfuron application may be a useful treatment for direct-seeded watermelon. This option would enable more judicious use of herbicides and possible reduction in production costs.
Sweetpotato Tolerance to Thifensulfuron Applied Postemergence
Authors: MacRae Andrew W. , Monks David W. , Batts Roger B. , Thornton Allan C.
Published: December 2007

An experiment was conducted at two locations in 2003 and 2004 to determine the timing and rate of thifensulfuron that is safe to use on sweetpotato. Thifensulfuron was applied 1, 2, and 4 wk after transplanting (WAP) in 2003 and 4, 6, and 8 WAP in 2004. Within each timing, thifensulfuron treatments were 1.1, 2.1, 3.2, 4.3, and 8.5 g ai/ha plus a weed-free control. The 1 and 2 WAP timings of thifensulfuron reduced the yield of number 1 roots greater than 25%. The 4, 6, and 8 WAP timings had less than 15% reduction in yield, with the 6 WAP timing reducing number 1 roots and total yield 10% or less. When 4.3 g/ha of thifensulfuron was applied 4 WAP, total yield was reduced 13%. The 6 and 8 WAP timings had little yield reduction, with no rate response observed. Application of 4.3 g/ha of thifensulfuron at 6 WAP would allow for control of problematic weed species while limiting potential yield loss. Yield loss from a 4 WAP application of thifensulfuron may in fact be a delay in crop maturity that could be recovered if the sweetpotato harvest was delayed to allow for the optimal amount of number 1 grade roots to be produced.
A Comparison of Flumioxazin and Rimsulfuron Tank Mixtures for Weed Control in Potato
Authors: Hutchinson Pamela J. S.
Published: December 2007

In 2004 and 2005, field research was conducted in Idaho to compare tank mixtures of flumioxazin at the 53 g ai/ha potato use rate with comparable tank mixtures of rimsulfuron at 26 g ai/ha for broad-spectrum weed control. Flumioxazin in two-way tank mixtures with metribuzin, EPTC, pendimethalin, S-metolachlor, or ethalfluralin provided greater than 90% hairy nightshade control, which was comparable with control by similar rimsulfuron two-way tank mixtures. Flumioxazin plus metribuzin or rimsulfuron were the only two-way mixtures with flumioxazin consistently providing 90% or greater redroot pigweed, common lambsquarters, and green foxtail control. Control of these weeds by any of the rimsulfuron two-way mixtures was almost always greater than 90%. Three-way tank mixtures containing flumioxazin or rimsulfuron controlled hairy nightshade, redroot pigweed, and common lambsquarters similarly, and control ranged from 89 to 100%. When metribuzin was not included with flumioxazin in three-way mixtures, control was 80 to 97% and not always comparable with the 89 to 100% control by similar rimsulfuron mixtures. Green foxtail control by flumioxazin or rimsulfuron three-way mixtures usually was similar and greater than 90%.
Soybean Tolerance to Early Preplant Applications of 2,4-D Ester, 2,4-D Amine, and Dicamba
Authors: Thompson M. Angela , Steckel Lawrence E. , Ellis Andrew T. , Mueller Thomas C.
Published: December 2007

Preplant applications of two 2,4-D formulations and dicamba were evaluated for injury to no-till soybean. Herbicides applied 28 or 21 d before planting (DBP) at 0.56 kg ae/ha for the 2,4-D formulations and 0.28 kg ae/ha for dicamba did not injure soybean. At 14 DBP soybean injury was lower (< 6%) with applications of 2,4-D than with dicamba (13% to 17%). Injury increased when herbicides were applied at 7 DBP with soybean injury from both 2,4-D (< 11%) and dicamba (< 38%). When the herbicides were applied at planting soybean injury was < 18% with the 2,4-D formulations and < 73% with dicamba. Soybean yields were unaffected by the injury from herbicides applied 21, 14, and 7 DBP. However, soybean yield was decreased to 870 kg/ha in 2005 when dicamba was applied at planting compared to the nontreated check (1,950 kg/ha)
Student Perspectives on the Southern Weed Contest
Authors: Norsworthy Jason K. , Burgos Nilda R. , Oliver Lawrence R.
Published: December 2007

The annual Southern Weed Contest has been a valuable asset for training graduate students in the applied aspects of weed science since its inception in 1980. Recently, participation in the contest has declined, which spurred the need to assess the contest's utility. Past participants in the contest from 1980 through 2004 were surveyed (1) to determine their perception of the importance, impact, and need for a weed contest activity in the southern region; and (2) to determine whether participation in the contest is contingent upon availability of study material resources and level of emphasis placed on the contest at each university. A total of 88 of 134 electronic surveys was returned, with at least 1 survey from each of the 14 universities in the southern region. Most participants (93%) expressed having had a pleasurable experience in the contest. Fifty-five percent of the respondents indicated that the contest either “increased” or “may have increased” their employment opportunities. Ninety-two percent of the respondents indicated that they had access to “excellent” or “adequate” resources to prepare for the contest. Ninety-eight percent of the respondents felt that the contest is still needed. Faculty involvement in student preparation was closely linked to team performance in the contest. There were numerous ideas put forth to increase participation along with ways to make the contest more interesting and relevant with the changing times. With less than 25% of the graduate students in the southern region competing in the contest for the last 3 years, there is obviously a disconnect between the apparent benefits of participation and the number of students taking advantage of it. However, participation alone without preparation does little to instill within students the confidence and knowledge necessary to make the contest an enjoyable experience. Ultimately, the future of the Southern Weed Contest rests on weed science faculty involvement from each university in the southern region and on recruitment of graduate students.
Comparison of Preemergence and Postemergence Weed Control Systems in Newly Established Pecan
Authors: Faircloth Wilson H. , Patterson Michael G. , Foshee Wheeler G. , Nesbitt Monte L. , Goff William D.
Published: December 2007

Six weed control programs with and without irrigation were investigated in a newly established pecan orchard. Irrigation increased crown diameter growth in only one of seven growing seasons but increased nut yield an average of 35% in the first two bearing years. Weed control program significantly influenced crown diameter beginning in the fourth growing season and continued through season six while also impacting final crown diameter. The use of postemergence (POST) herbicides increased crown diameter a minimum 4 mm vs. preemergence (PRE) herbicides. Mowing neither increased nor decreased crown diameter when used with herbicides; however, when used solely, crown diameter was 29% less. Highest growth rates were obtained with a combination PRE plus POST weed management system. Nut yields were closely linked to growth data. No differences in nut yield were observed between PRE- or POST-herbicide programs alone or in combination with mowing. Mowing alone decreased nut yield 57% vs. herbicide-based approaches. A combination PRE- plus POST-weed control program increased yield 38% vs. all other treatments.
Sweetpotato Tolerance to Halosulfuron Applied Postemergence
Authors: MacRae Andrew W. , Monks David W. , Batts Roger B. , Thorton Allan C. , Schultheis Jonathan R.
Published: December 2007

Studies were conducted in 2003 and 2004 to determine the effect of application timing and halosulfuron rate on sweetpotato yield and quality. Halosulfuron was applied 1, 2, and 4 wks after transplanting (WAP) sweetpotato in 2003, and 2, 3, and 4 WAP in 2004. Treatments within each timing included halosulfuron at 13, 26, 39, 52, and 65 g ai/ha plus a weed-free control. Combined over year, site, cultivar and rate, halosulfuron applied at 1, 2, 3, and 4 WAP stunted sweetpotato 32, 15, 11, and 14%, respectively, rated 2 wks after treatment. The stunting observed with the 1 and 2 WAP timings caused a 17 and 10% reduction in yield of No. 1 roots, respectively, compared with the weed-free control. The 3 and 4 WAP timings of halosulfuron did not reduce yield of No. 1 roots. Total yield was reduced approximately 11% at the 1, 2, and 3 WAP application timings. Halosulfuron at 4 WAP did not reduce total yield. Combined over year, site, and cultivar, halosulfuron applied at 39 g/ha did not reduce the weight of No. 1 roots or total crop yield and thus could be an effective POST option for weed control in sweetpotato.
Rice Cultivar Response to Penoxsulam
Authors: Bond Jason A. , Walker Timothy W. , Webster Eric P. , Buehring Nathan W. , Harrell Dustin L.
Published: December 2007

A study was conducted in 2005 and 2006 to evaluate the response of 10 rice cultivars to penoxsulam applied at 70 g ai/ha to two- to three-leaf rice. A related study was conducted in 2004 and 2005 to compare the rice response to applications of penoxsulam at 35 and 70 g/ha and bispyribac-sodium at 28 g ai/ha. In the first study, all 10 rice cultivars exhibited tolerance to penoxsulam as evidenced by plant height, number of days to 50% heading, and rice grain yield. In the second study, applications of both rates of penoxsulam and bispyribac-sodium reduced mass of rice roots 65 to 71% 2 wk after treatment compared with a nontreated control. However, rice grain yield was higher following application of penoxsulam at 70 g/ha compared with yield of the nontreated control or yield following penoxsulam at 35 g/ha and bispyribac-sodium. Rice recovered from injury observed following herbicide application with no negative impact on grain yield. Results indicate that, even though rice root injury can be severe following application, penoxsulam is safe for application to rice cultivars currently grown in the southern U.S. Rice Belt.
Canada Thistle (Cirsium arvense) Control with Aminopyralid in Range, Pasture, and Noncrop Areas
Authors: Enloe Stephen F. , Lym Rodney G. , Wilson Robert , Westra Phil , Nissen Scott , Beck George , Moechnig Michael , Peterson Vanelle , Masters Robert A. , Halstvedt Mary
Published: December 2007

Canada thistle is a serious weed of many crop, rangeland, pasture, and natural areas throughout North America. Aminopyralid is a new pyridine carboxylic acid herbicide that has activity on Canada thistle at lower use rates than current standard treatments. The objectives of this study were to compare aminopyralid efficacy, rates, and application timing with several commercial standards for Canada thistle control. Studies were conducted across the Great Plains at ten locations, which encompassed a wide range of environments. Aminopyralid provided Canada thistle control comparable to picloram, picloram + 2,4-D amine, and clopyralid and better control than clopyralid + 2,4-D amine, dicamba, dicamba + 2,4-D amine and dicamba + diflufenzopyr. Canada thistle control was similar when aminopyralid was applied between 0.08 and 0.11 kg ai/ha and application timing (spring bolting vs. fall rosette/regrowth) did not strongly influence control 1 yr after treatment (YAT). Aminopyralid provided effective Canada thistle control at lower use rates than current commercial standards and might be useful in areas where herbicides such as picloram and clopyralid are not recommended for use.
Cover Crop Management Affects Weeds and Yield in Organically Managed Sweetpotato Systems
Authors: Treadwell Danielle D. , Creamer Nancy G. , Schultheis Jonathan R. , Hoyt Greg D.
Published: December 2007

A 3-yr field experiment was initiated in 2001 to evaluate weed suppression and sweetpotato productivity in three organic sweetpotato production systems. Organic systems were (1) compost and no cover crop with tillage (Org-NC), (2) compost and a cover crop mixture of hairy vetch and rye incorporated before transplanting (Org-CI), and (3) compost and the same cover crop mixture with reduced tillage (Org-RT). A conventional system with tillage and chemical controls (Conv) was included for comparison. Suppression of monocot and dicot weed density and biomass was similar between Org-NC and Org-CI each year, and were frequently similar to Conv. Org-RT was as effective as Org-NC in controlling dicot weed density and biomass each year, but did not suppress monocot weeds. At sweetpotato harvest, an increase in cover crop surface residue biomass in Org-RT was associated with a decrease in cumulative total weed density (R2= 0.43, P = 0.0001); however, the amount of that residue was insufficient to suppress late-emerging monocot weeds. Total sweetpotato yield in Org-RT was at least 45% lower than other systems in 2002 and was most likely due to an increase in monocot weed density and biomass concurrent with a decrease in sweetpotato vine biomass. Total sweetpotato yield was similar among all systems in 2001 and 2004; the exception was lowest yields obtained in the Org-RT system in 2002. Organically managed sweetpotato with or without an incorporated cover crop produced sweetpotato yields equal to conventionally managed systems despite difficulties controlling weeds that emerged later in the season.
Physiological and Molecular Characterization of Atrazine Resistance in a Wild Radish (Raphanus raphanistrum) Population
Authors: Friesen L. J. Shane , Powles Stephen B.
Published: December 2007

This study documents the physiology and genetics of evolved atrazine resistance in a wild radish population from Western Australia. Plant response to atrazine treatment confirmed a high level of resistance in population WARR5. At 0.25 kg atrazine/ha, all plants from a susceptible population were killed, whereas resistant WARR5 was unaffected at the highest dose tested (4 kg atrazine/ha). Leaf photosynthesis in susceptible plants was inhibited after 1 kg atrazine/ha treatment, whereas leaf photosynthesis in WARR5 plants was unaffected. Furthermore, atrazine resistance was maternally inherited. Sequencing of apsbAgene fragment in resistant WARR5 and susceptible plants revealed a single point mutation resulting in a coding change from Ser264to Gly of the D1 protein in resistant plants. We are confident that this mutation is the basis of resistance to the photosystem II inhibitors in this wild radish population.
Cotton Response to Simulated Drift of Seven Hormonal-Type Herbicides
Authors: Marple Molly E. , Al-Khatib Kassim , Shoup Douglas , Peterson Dallas E. , Claassen Mark
Published: December 2007

Field experiments were conducted at Manhattan and Hesston, KS, in 2004, and at Manhattan, KS, in 2005, to evaluate cotton response to seven hormonal-type herbicides. Herbicides 2,4-D amine, 2,4-D ester, clopyralid, picloram, fluroxypyr, triclopyr, and dicamba were each applied at 0, 1/100, 1/200, 1/300, and 1/400 of the herbicide use rates on cotton in the six- to eight-leaf stage. Herbicide use rates were 210 and 280 g ae/ha for fluroxypyr and clopyralid and 561 g ae/ha, for 2,4-D amine, 2,4-D ester, dicamba, picloram, and triclopyr. At 14 d after treatment (DAT), all herbicides caused leaf cupping and epinasty, except triclopyr and clopyralid, which caused severe bleaching and chlorosis. The order of visual injury ratings was 2,4-D ester > 2,4-D amine > picloram > dicamba > fluroxypyr > triclopyr > clopyralid. By 56 DAT, slight injury symptoms were observed on plants treated with all herbicides, except all rates of 2,4-D, from which symptoms were severe. All rates of 2,4-D and the highest rate of picloram caused more than 60% flower abortion. Ranking of fiber yield reduction after herbicide treatment was 2,4-D ester > 2,4-D amine > picloram > fluroxypyr > dicamba > clopyralid > triclopyr. This research demonstrated that cotton is extremely susceptible to simulated drift rates of 2,4-D and picloram, whereas clopyralid and triclopyr caused early injury, with minimal effect on cotton yield.
Bundleflower (Desmanthus bicornutus) Response to Postemergence Herbicides
Authors: Grichar W. James , Ocumpaugh W. R.
Published: December 2007

Field studies were conducted from 2003 through 2006 to evaluate bundleflower tolerance to several postemergence (POST) herbicides commonly used in pastures. All herbicides except imazapic, metsulfuron, and 2,4-DB injured bundleflower at least 88% when rated 4 wk after treatment (WAT). When rated 8 WAT, metsulfuron, picloram, and picloram plus 2,4-D injured bundleflower greater than 90%. Imazapic stunted bundleflower (10 to 35% injury) throughout the growing season. When rated 52 WAT, dicamba plus 2,4-D, picloram alone, and picloram plus 2,4-D injured bundleflower at least 97% in one of two years. Emergence of bundleflower with picloram-containing treatments ranged from 16 to 67% of the nontreated control, whereas emergence after dicamba-containing treatments ranged from 67 to 97%.
Selective Nimblewill (Muhlenbergia schreberi) Control in Cool-Season Turfgrass
Authors: Willis John B. , Beam Josh B. , Barker Whitnee L. , Askew Shawn D. , McElroy J. Scott
Published: December 2007

Isoxaflutole and mesotrione have been used to control creeping bentgrass in cool season turf, these experiments evaluate these two products for selective nimblewill control. Three experiments were conducted in Virginia and Tennessee to evaluate selective control options for nimblewill in cool-season turfgrass. Single applications of isoxaflutole control nimblewill more effectively than single applications of mesotrione. Nimblewill control 8 wk after initial treatment (WAIT) increased as mesotrione rates increased from 28 to 280 g ai/ha, and isoxaflutole rates increased from 28 to 168 g/ha. Isoxaflutole at 84 and 168 g/ha were the only single application treatments that controlled nimblewill greater than 80% 8 WAIT. However, sequential applications of isoxaflutole and mesotrione at 28 g/ha, 10 d apart controlled nimblewill 94 and 80%, respectively 8 WAIT. Triclopyr and fenoxaprop-p did not effectively control nimblewill and caused unacceptable turfgrass injury. Long-term control was not evaluated in these studies. However, it was concluded that isoxaflutole and mesotrione at appropriate rates and applied in sequence selectively control nimblewill without harming desirable turf.
Strategies for Managing Early Succession Habitat for Wildlife
Authors: Harper Craig A.
Published: December 2007

Early succession plant communities consisting of a diverse mixture of grasses, forbs, and scattered shrubs are required by a variety of wildlife species. Early seral stages follow some form of disturbance but can become dominated by shrubs and trees rather quickly, especially in areas with abundant rainfall and relatively long growing seasons, such as the southeastern United States. In the absence of natural disturbance regimes, the quality and maintenance of these plant communities for wildlife is largely dependent upon management. Prescribed fire, disking, herbicide applications, and mowing are practices commonly used to maintain early succession plant communities for various wildlife species throughout this region. Prescribed fire consumes vegetative debris, provides open structure at ground level, and facilitates travel and foraging for wildlife throughout the field. Burning during the dormant season may promote cool-season grasses if they are present in the field. Burning in late March or early April generally promotes warm-season grasses and forbs. Late growing-season fire (September) will reduce woody encroachment and may encourage additional forb cover. Disking promotes vegetation decomposition, provides open structure at ground level, and generally promotes annual plant species. Disking in the fall and winter stimulates more forb growth than disking in the spring, which will stimulate undesirable nonnative warm-season grasses if present in the seedbank. Selective herbicides can influence plant composition and can be used to encourage grasses where forbs dominate, to promote forbs where grasses dominate, and to reduce woody cover. Mowing during midsummer encourages additional grasses in fields dominated by forbs but is not recommended for field maintenance because mowing produces thatch, which limits the ability of several wildlife species to travel and forage through the field, suppresses the seedbank, and destroys nests and young wildlife. Several practices can be used in combination to meet specific objectives. Succession should be set back every 2 to 4 yr, depending on plant response and focal wildlife species. It is important to intersperse disturbance in space and time, so that a variety of cover types are always available, even to those animals with small home ranges.
The Effect of Imazamox Application Timing and Rate on Imazamox Resistant Wheat Cultivars in the Pacific Northwest
Authors: Carter Arron H. , Hansen Jennifer , Koehler Thomas , Thill Donald C. , Zemetra Robert S.
Published: December 2007

Grass weeds are a major problem in winter wheat fields in the Pacific Northwest (PNW). Control of these weeds is now enhanced with the use of imazamox resistant winter wheat cultivars, which have been rapidly adopted by wheat growers. However, the effect of spray rate and timing on crop injury and agronomic traits of wheat cultivars with different genetic backgrounds has not been adequately evaluated. Thus, experiments were conducted near Moscow and Genesee, ID in the 2003–2004 and 2004–2005 growing seasons to evaluate the effect of imazamox on four resistant cultivars and seven resistant breeding lines. Wheat plants were treated at the 3- to 5-leaf stage and the 3- to 7-tiller stage with 45 and 90 g ai/ha of imazamox. Visible crop injury was evaluated from 14 to 35 d after treatment (DAT). Heading date, plant height, grain yield and test weight, and end-use grain quality also were measured. The cultivar by treatment interaction was significant at 21 DAT, caused by a differential response of wheat lines to imazamox treatment. This interaction also was significant for plant height and grain yield. Although cultivars and breeding lines responded differently to imazamox treatment, two lines consistently showed the least levels (3 to 8%) of crop injury, with no reductions in plant height or grain yield following imazamox application. Orthogonal contrasts of visible crop injury at 21 DAT showed that the 2× imazamox rate caused more crop injury (12%) than the 1× rate (7%). The 2× rate of imazamox reduced plant height 1%, grain yield 8%, test weight 1%, and percent flour yield 1%. All other traits were not affected by application of imazamox. Application timing only minimally affected crop injury, and had no effect on agronomic or end-use quality traits.
Reduced-Input, Postemergence Weed Control with Glyphosate and Residual Herbicides in Second-Generation Glyphosate-Resistant Cotton
Authors: Scroggs Derek M. , Miller Donnie K. , Griffin James L. , Steckel Lawrence E. , Blouin David C. , Stewart Alexander M. , Vidrine P. Roy
Published: December 2007

Field studies were conducted 2004 and 2005 to evaluate weed control following POST applications of glyphosate in combination with eitherS-metolachlor (premix formulation), pyrithiobac, or trifloxysulfuron in conjunction with glyphosate in second-generation glyphosate-resistant cotton (Roundup Ready Flex). These herbicides were applied in combination with glyphosate in a two-application program at the 2-leaf (LF) (followed by glyphosate alone at the 10-LF growth stage), 6-LF (following glyphosate alone at the 2-LF growth stage), or 10-LF (following glyphosate alone at the 2-LF growth stage) cotton growth stages. No differences in weed control between residual herbicide were observed for goosegrass, hemp sesbania, Johnsongrass, Palmer amaranth, redroot pigweed, sicklepod, or smellmelon. Optimum control of barnyardgrass and browntop millet was achieved with glyphosate plusS-metolachlor. No differences were observed among application timings for control of goosegrass, hemp sesbania, Johnsongrass, pitted morningglory, and smellmelon. Control of barnyardgrass, browntop millet, Palmer amaranth, redroot pigweed, and sicklepod was optimized with residual herbicide application at the 2- or 10-LF timing. No yield differences were observed between residual herbicides, and seed cotton yield averaged 2,800 kg/ha. Yield was maximized when residual herbicide was applied at the 2- or 10-LF growth stage (2,960 to 2,730 kg/ha). Analysis based on numerical yield at particular residual-herbicide application timings and calculated yield for each timing based on the percentage of a standard three-application glyphosate program indicated the most consistent residual-herbicide timing for optimizing yield in a reduced-input Roundup Ready Flex weed-control program occurred at the two-leaf growth stage. All reduced-input programs, however, resulted in cotton yield of at least 93% of that obtained with the standard program.
Compatibility of Diclosulam with Postemergence Herbicides and Fungicides
Authors: Lancaster Sarah H. , Beam Joshua B. , Lanier James E. , Jordan David L. , Johnson P. Dewayne
Published: December 2007

Diclosulam is registered for residual and postemergence control of several broadleaf weeds and suppression of annual sedges in peanut in the southeastern United States. Many producers apply herbicides and other pesticides simultaneously to increase the spectrum of pest control or to increase efficiency of operations. However, compatibility of coapplication of pesticides is a concern. Field trials were conducted to evaluate the compatibility of diclosulam with other herbicides and fungicides. Horseweed control by diclosulam in combination with glyphosate, sulfosate, or paraquat was compared to combinations of these herbicides with flumioxazin, tribenuron plus thifensulfuron, or 2,4-D. All treatments that contained diclosulam controlled horseweed at least 86%. Broadleaf signalgrass control by clethodim and sethoxydim was not affected by diclosulam; however, large crabgrass control was reduced when graminicides were coapplied with diclosulam. Common ragweed control was reduced when diclosulam was applied with chlorothalonil and pyraclostrobin but not by azoxystrobin or tebuconazole.
Rimsulfuron for Postemergence Weed Control in Corn in Humid Tropical Environments of Nigeria
Authors: Chikoye David , Udensi Udensi E. , Lum A. Fontem , Ekeleme Friday
Published: December 2007

Cogongrass and guineagrass are serious perennial weeds in small-scale farms in lowland subhumid zones of West Africa. Field studies were conducted in 2002 and 2003 at two sites in Ibadan, Nigeria [Ijaye and the International Institute of Tropical Agriculture (IITA)], to evaluate the effect of rimsulfuron on weed communities dominated by cogongrass and guineagrass in corn. At both sites, treatments were rimsulfuron dosages of 0 (nontreated control), 10, 20, 30, 40, 50, 60, 70, and 80 g ai/ha. Rimsulfuron did not cause any visible phytotoxicity on the corn at any dosage at either site. There was a rapid increase in weed control as the dosage of rimsulfuron increased from 0 to 20 g/ha. Weed control was not improved at rates higher than 20 g/ha. Rimsulfuron was very effective against sedges,Ipomoea involucrata, Bengal dayflower, gulf leafflower, old-world diamond-flower, and wild jute providing more than 80% control at dosages between 10 and 20 g/ha at Ijaye. Rimsulfuron was less effective for cogongrass, with a maximum of only 38% control observed. At IITA, the herbicide was very effective against guineagrass, Bengal dayflower, nodeweed, coat buttons, redfruit passionflower, and waterleaf; all of which were controlled more than 70% with any rate of rimsulfuron. Regression analysis showed that the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 5 g/ha for guineagrass and 35 g/ha for cogongrass at 3 wk after treatment (WAT). At crop maturity, the dosage of rimsulfuron required to reduce shoot dry biomass by 70% was 43 g/ha for guineagrass and 200 g/ha for cogongrass. The dry biomass of cogongrass and guineagrass was higher at crop harvest than at 2 WAT regardless of herbicide dosage. Corn grain yield was 1.8 times higher at IITA than at Ijaye. At both sites, corn grain yield increased with increased herbicide dosage. Maximum corn grain yields were obtained at a rimsulfuron dosage of 20 g/ha.
Sugarcane Response to Bermudagrass Interference
Authors: Richard Edward P. , Dalley Caleb D.
Published: December 2007

The competitiveness of three phenotypically different sugarcane cultivars with bermudagrass was determined in field trials. In trial one, bermudagrass biomass was 22% less in CP 70-321 than in HoCP 85-845 in the plant-cane crop, but biomass was 130 to 170% greater in CP 70-321 than in the other two cultivars during the second-ratoon crop. CP 70-321 emerges quickly following planting, which might have reduced bermudagrass growth in the plant-cane crop, but the lower stalk population of CP 70-321 might have promoted bermudagrass survival and growth during the second-ratoon crop. In trial two, there were no differences in bermudagrass biomass when comparing its establishment in the different cultivars. Sugarcane, averaged across cultivar, produced fewer stalks and was shorter when competing with bermudagrass. In the plant-cane crop, stalk populations were reduced 13 to 23%. In the first-ratoon crop, stalk population was reduced 8 to 15%. In the second-ratoon crop, stalk population was reduced 8 to 10%. Bermudagrass interference reduced sugar yields by 8 to 32% in the plant-cane crop, with reductions of no more than 9% in the first- and second-ratoon crops. The greater yield loss in the plant-cane crop in the first production year shows the importance of controlling bermudagrass in the summer fallow period prior to planting and during establishment of the plant-cane crop.
Effectiveness of Preemergence Herbicide and Postemergence Glyphosate Programs in Second-Generation Glyphosate-Resistant Cotton
Authors: Scroggs Derek M. , Miller Donnie K. , Griffin James L. , Wilcut John W. , Blouin David C. , Stewart Alexander M. , Vidrine P. Roy
Published: December 2007

A study was conducted in 2004 and 2005 to evaluate the benefit of applying fluometuron PRE versus glyphosate-only POST programs in second-generation GR cotton (Roundup Ready Flex®). Fluometuron was either included or excluded with POST application timings of glyphosate at the following cotton growth stages: (1) 3 leaf (lf) followed by (fb) 7 lf fb 14 lf (over the top) OT (2) 3 fb 7 lf OT (3) 7 lf OT fb 14 lf postemergence directed (PD), and (4) 7 fb 14 lf OT. Control of goosegrass, Palmer amaranth, pitted morningglory, sicklepod, and smellmelon was increased 2 to 8 percentage points with the addition of fluometuron PRE. The inclusion of fluometuron PRE did not improve control of barnyardgrass, browntop millet, hemp sesbania, johnsongrass, or redroot pigweed and control ranged from 81% to 84%, 69% to 75%, 94% to 94%, 87% to 89%, and 92% to 93%, respectively. By 56 d after the last POST application, control of johnsongrass, Palmer amaranth, pitted morningglory, and smellmelon was at least 83%, 93%, 92%, and 86%, respectively, with only slight differences noted among POST glyphosate programs. Control of barnyardgrass, browntop millet, and redroot pigweed was 68%, 47%, 86%, respectively, with the POST glyphosate program of 3 fb 7 lf OT, which was significantly less than all other glyphosate POST programs. Cotton yield increased 32% and 36% with the addition of fluometuron PRE to glyphosate POST programs consisting of 7 lf OT fb 14 lf PD and 7 lf fb 14 lf OT, respectively. Cotton yield for other glyphosate POST programs including an earlier 3 lf application was not improved when fluometuron was applied PRE. Without inclusion of fluometuron PRE, yield was maximized with the glyphosate POST program that included three applications of glyphosate (2,510 kg/ha). Overall, this research emphasizes the fact that weed control is important in the early season as well as in the late season in second-generation GR cotton.
Oat and Rye Tolerance to Mesosulfuron and Tribenuron
Authors: MacRae Andrew W. , Culpepper A. Stanley , Grey Timothy L.
Published: December 2007

The affect of mesosulfuron and tribenuron applied POST to oat and rye was determined at three locations in Georgia during 2004 and 2005. Five herbicide treatments were applied to oat and rye in Feekes scale (FS) 1.2 or 2 developmental stage. Herbicide treatments consisted of tribenuron at 13 or 26 g ai/ha, tribenuron at 13 g/ha plus MCPA at 561 g ai/ha, MCPA at 561 g/ha, and mesosulfuron at 15 g ai/ha. Tribenuron, MCPA, and tribenuron plus MCPA injured both crops less than 4% and did not affect grain yield. Mesosulfuron applied to rye in FS 1.2 injured the crop 36% at 2 wk after treatment (WAT), 12% at 5 WAT, and 0% at harvest. Mesosulfuron applied at FS 2 injured rye less than 9%. Mesosulfuron did not influence rye-grain yield with either application timing. Mesosulfuron injured oat 65 to 86% at 5 WAT and reduced yield at least 70% regardless of application timing.
Nonvertical Spray Angles Optimize Graminicide Efficacy
Authors: Jensen Peter Kryger
Published: December 2007

Annual grasses constitute a major weed problem in winter annual crops in Northern Europe and especially in cropping systems where ploughing is omitted. At the optimum growth stage for control with POST herbicides, grasses have a predominantly vertical leaf orientation. This represents a very difficult spray target using the standard technique where nozzles are mounted more or less vertically downward. In this study, efficacy of the foliar-acting herbicide, haloxyfop, on perennial ryegrass at the two- to three-leaf stage was investigated in field experiments using some alternative configurations of nozzle mounting on the sprayer. Angling the spray either forward or backward relative to the direction of travel increased herbicide efficacy using standard commercially available flat-fan and pre-orifice nozzles. Efficacy increased generally with increasing angling relative to vertically downward and the forward-angled spray improved efficacy most. The largest improvement in efficacy was obtained using a 60° forward-angled spray in combination with a reduced boom height. Using this configuration, herbicide dose could be reduced by approximately 30% without loss of efficacy in comparison with the standard vertical mounting of nozzles. There was no advantage of using combinations of forward- and backward-angled nozzles.
Yield and Physiological Response of Peanut to Glyphosate Drift
Authors: Lassiter Bridget R. , Burke Ian C. , Thomas Walter E. , Pline-Srnić Wendy A. , Jordan David L. , Wilcut John W. , Wilkerson Gail G.
Published: December 2007

Five experiments were conducted during 2001 and 2002 in North Carolina to evaluate peanut injury and pod yield when glyphosate was applied to 10 to 15 cm diameter peanut plants at rates ranging from 9 to 1,120 g ai/ha. Shikimic acid accumulation was determined in three of the five experiments. Visual foliar injury (necrosis and chlorosis) was noted 7 d after treatment (DAT) when glyphosate was applied at 18 g/ha or higher. Glyphosate at 280 g/ha or higher significantly injured the peanut plant and reduced pod yield. Shikimic acid accumulation was negatively correlated with visual injury and pod yield. The presence of shikimic acid can be detected using a leaf tissue assay, which is an effective diagnostic tool for determining exposure of peanut to glyphosate 7 DAT.
Optimizings-Metolachlor and Dimethenamid-P in Sugarbeet Microrate Treatments
Authors: Bollman Scott L. , Sprague Christy L.
Published: December 2007

Field trials were conducted in East Lansing, MI in 2004 and 2005 and in St. Charles, MI in 2004, 2005, and 2006 to compare weed control and sugarbeet tolerance from microrate herbicide treatments that includeds-metolachlor and dimethenamid-P. Treatments included the base microrate treatment alone and with full- and split-application rates ofs-metolachlor at 1.4 kg/ha or dimethenamid-P at 0.84 kg/ha at the various microrate application timings. All treatments injured sugarbeet. In 2004 and 2006, full rates of boths-metolachlor and dimethenamid-P applied PRE or in the first microrate application injured sugarbeet more than the base microrate treatment. Whens-metolachlor or dimethenamid-P were split-applied between PRE and the third microrate application or between the first and the third microrate applications, injury was still greater than from the base microrate treatment. Furthermore, applying dimethenamid-P at one-fourth the full rate in all four microrate applications injured sugarbeet more than the base microrate treatment. A full rate ofs-metolachlor or dimethenamid-P applied in either the third or fourth microrate applications or splitting the applications between the second and fourth microrate treatments did not increase sugarbeet injury compared with the base microrate treatment. Control of common lambsquarters and giant foxtail from all treatments containings-metolachlor or dimethenamid-P, regardless of the time of application, was greater than from the base microrate treatment at all locations. Pigweed spp. control was 94% or greater from all treatments. In 2004, late-season control of giant foxtail was greater from all treatments that includeds-metolachlor or dimethenamid-P compared with the base microrate treatment. In 2005, the only treatments that did not improve late-season giant foxtail control compared with the base microrate treatment were the treatments that included a full rate ofs-metolachlor or dimethenamid-P applied in the fourth microrate application. Even though some herbicide treatments that includeds-metolachlor or dimethenamid-P injured sugarbeet more than the base microrate treatment, recoverable sucrose per hectare was similar among treatments.
Wheat Response to Simulated Glyphosate Drift
Authors: Roider Christopher A. , Griffin James L. , Harrison Stephen A. , Jones Curtis A.
Published: December 2007

Glyphosate at simulated drift rates representing 12.5, 6.3, and 1.6% of the usage rate of 1,120 g ai/ha (140, 70, and 18 g/ha, respectively) was applied to wheat at first node, boot stage, or at early flowering. At 14 d after treatment (DAT) wheat injury, expressed as bleaching of leaf foliage and growth inhibition, was 40 to 55% for 70 g/ha applied at first node and for 140 g/ha applied at all growth stages. Wheat height 28 DAT was reduced 47% with glyphosate applied at 140 g/ha at first node and was reduced around 26% for 70 g/ha applied at first node and 140 g/ha applied at boot stage. Wheat height was not reduced with glyphosate at 18 g/ha applied at first node or boot stage and with all rates applied at early flowering. Wheat yield was reduced 72% when glyphosate was applied at 140 g/ha at first node, 45% when applied at boot stage, and 54% when applied at early flowering. For 70 g/ha, wheat yield was reduced 25 to 30% for the three application timings. Wheat yield was not reduced for 18 g/ha glyphosate. In another study, six wheat varieties responded the same to glyphosate applied at 140 and 70 g/ha. Wheat height 28 DAT was reduced an average of 34% for 140 g/ha glyphosate and 17% for 70 g/ha applied at first node, but height was not reduced when applied at early flowering. Yield was reduced an average of 58 and 43% for 140 and 70 g/ha applied at first node and 38 and 19% for 140 and 70 g/ha applied at early flowering. In both studies yield reductions in most cases were reflected in reduced spike density, spikelet number per spike, and seed weight.
Dark Tobacco (Nicotiana tabacum) Tolerance to Trifloxysulfuron and Halosulfuron
Authors: Bailey William A.
Published: December 2007

Field experiments were conducted at two locations in 2003 and 2004 to determine dark tobacco tolerance and weed control from postemergence over-the-top (POT) and postemergence-directed (PD) applications of trifloxysulfuron and halosulfuron. Trifloxysulfuron was applied at 3.6 or 5.3 g ai/ha and halosulfuron was applied at 36 or 53 g ai/ha. Trifloxysulfuron POT injured ‘Narrowleaf Madole’ dark tobacco 16 to 33% and halosulfuron POT caused 32 to 33% injury at 1 wk after treatment (WAT). Tobacco plant height at 1 WAT with POT applications was also reduced by up to 31% at one of two locations. Tobacco injury from POT applications had dissipated to 6 to 12% by 4 WAT. Despite extensive early-season injury, most POT herbicide applications did not significantly reduce tobacco yield, mean grade index, and gross revenue compared to tobacco that only received pretransplant applications of sulfentrazone plus clomazone. Dark tobacco was much more tolerant to PD applications of either herbicide, with no more than 4% injury observed at 1 WAT. Neither herbicide controlled horsenettle more than 57% at either application rate or method. Although trifloxysulfuron and halosulfuron could contribute to tobacco weed control programs by providing postemergence control of several common weed species, PD applications would be the only acceptable method of application due to excessive injury observed from POT applications of these herbicides.