bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Effect of 2,4-D on Whole-Stalk– and Billet-Planted Sugarcane
Authors: Siebert Jonathan D. , Griffin James L. , Jones Curtis A.
Published: July 2006

Field studies conducted for two growing seasons evaluated the effect of 2,4-D applied at 1.6 kg ai/ha to ‘LCP 85-384’ sugarcane 7, 5, 3, and 1 wk before planting (WBP). Sugarcane was planted in mid September using both whole stalks and billet (45 cm) stem sections. When 2,4-D was applied 5 wk or closer to planting, sugarcane shoot emergence and population averaged across planting methods and years were reduced up to 28 wk after planting (WAP) relative to the nontreated control. By 52 WAP, sugarcane had compensated and stalk population was equivalent among treatments. Sugarcane height in response to 2,4-D varied between years, and only in 2001 at 52 WAP was a height reduction observed when 2,4-D was applied 1, 3, or 5 WBP. Crop injury in 2001 was further reflected in reduced sugarcane yield (at least 11%) and sugar yield (at least 12%) more than 1 yr after 2,4-D had been applied 5 wk or closer to harvest of sugarcane for seed. Sugarcane and sugar yields were equivalent for the nontreated control and the 7 WBP 2,4-D treatment in 2001, but 2,4-D application in 2002 did not negatively affect yield. Even though sugarcane shoot populations across the growing seasons were consistently higher for the billet planting system, yields averaged across 2,4-D application timings were greater for billets (18%) compared with whole stalks only for the first year. Because 2,4-D can have a residual effect on sugarcane yield more than 1 yr after the initial foliar application, a 7-wk period should be allowed between herbicide application and harvest of LCP 85-384 for billet or whole-stalk planting.
Flumioxazin Preplant or POST-Directed Application Timing Followed by Irrigation at Emergence or After POST-Directed Spray Treatment Does Not Influence Cotton Yield
Authors: Price Andrew J. , Wilcut John W. , Cranmer John R.
Published: July 2006

Three experiments were conducted in Lewiston, NC, from 1999 through 2002 to evaluate the influence of various application timings of flumioxazin preplant (PP) and postemergence-directed spray (PDS) on cotton injury. In experiment 1, flumioxazin was evaluated in a reduced-tillage system at 71, 105, or 140 g ai/ha in mixture with glyphosate, applied at 28, 14, or 7 d before planting (DBP), followed by irrigation at cotton emergence. Flumioxazin applied PP at any rate and irrigated at emergence injured cotton less than 7% at 2 wk after emergence (WAE) and less than 6% 5 WAE. In experiment 2, flumioxazin was evaluated in a conventional-tillage system at 71 or 105 g/ha as a PDS treatment applied to dry soil, wet soil, and dry soil irrigated immediately after application when cotton was 20 to 30 cm height. Cotton treated with flumioxazin PDS at either rate applied to dry soil, wet soil, or dry soil followed immediately by irrigation was not injured. In the third experiment, flumioxazin at 71 g/ha alone or in mixture with glyphosate at 1.12 g/ha was applied at 30, 21, 14, and 0 DBP in a conventional-tillage system. Flumioxazin applied alone or in mixture with glyphosate applied at any time did not injure cotton. In all experiments, cotton lint yields were not influenced by herbicide treatment.
Evaluation and Adaptation of the HADSS®Computer Program in Texas Southern High Plains Cotton
Authors: Lyon Leanna L. , Keeling J. Wayne , Dotray Peter A.
Published: July 2006

Field experiments were conducted in 1999 and 2000 to evaluate and adapt the Herbicide Application Decision Support System (HADSS®) program for Texas Southern High Plains cotton production. Weed management systems (in glyphosate-resistant, bromoxynil-resistant, and nontransgenic cotton varieties) included trifluralin preplant incorporated (PPI) followed by (fb) HADSS postemergence-topical (POST) recommendations (PPI fb POST HADSS), HADSS recommendations alone (POST HADSS), and Texas Agricultural Experiment Station (TAES) recommendations for the Texas Southern High Plains. In both years, effective season-long weed control was achieved with all weed management systems in the glyphosate-resistant variety, but only the PPI fb POST HADSS and TAES weed management systems controlled Palmer amaranth and devil's-claw in the bromoxynil-resistant and nontransgenic varieties, compared with POST HADSS alone. No differences in cotton lint yield or net returns over weed control costs were observed with weed management systems across variety in 1999; however, in general, the glyphosate-resistant and nontransgenic varieties produced higher yields and net returns than the bromoxynil-resistant variety. In 2000, plots from the TAES weed management system produced higher lint yields than the plots of PPI fb POST HADSS recommendations in the glyphosate- and bromoxynil-resistant varieties, but plots of all management systems yielded similarly in the nontransgenic variety. In 2000, plots from the TAES system produced the highest net returns in the glyphosate- and bromoxynil-resistant varieties. In the nontransgenic variety, the PPI fb POST HADSS and TAES weed management systems produced higher net returns over weed control costs than the POST HADSS system.
Herbicide Effects on Established Yellow Old World Bluestem (Bothriochloa ischaemum)
Authors: Harmoney Keith R. , Stahlman Phillip W. , Hickman Karen R.
Published: July 2006

Nine herbicides were tested in a field trial during 2001 and 2002 for the ability to suppress growth of established plants of yellow old world bluestem (OWB) that had invaded native vegetation in central Kansas. Herbicide treatments were applied to OWB at the V4 stage of growth using the Nebraska staging method. At 9 wk after treatment (WAT), plots treated with imazapyr at 1.40 kg ai/ ha had much lower OWB plant frequency than the untreated plots, and plots sprayed with imazapyr and bromacil at 7.84 kg ai/ha had much lower OWB tiller densities than the control plots. Imazapyr and glyphosate at 3.36 kg ai/ha provided greater OWB control than other herbicides. At the first frost after treatment application, imazapyr and bromacil treatments continued to have lower OWB frequency and tiller density than the control plots. Visible herbicide control was closely related to end-of-season yield (R= −0.97). Imazapic at 0.16 kg ai/ha, glyphosate, sulfometuron at 0.21 kg ai/ ha, bromacil, and imazapyr controlled OWB from 54 to 94%. Split applications, altered timing of herbicide application, or varied rates of herbicides that exhibited suppressive potential may further improve efficacy of these herbicides.
Control of Protoporphyrinogen Oxidase Inhibitor–Resistant Common Waterhemp (Amaranthus rudis) in Corn and Soybean
Authors: Shoup Douglas E. , Al-Khatib Kassim
Published: July 2006

Field experiments were conducted in 2001 and 2002 to evaluate the efficacy of herbicides on protoporphyrinogen oxidase (protox, EC 1.3.3.4) inhibitor–resistant common waterhemp in corn and soybean. All corn herbicides tested gave greater than 90% common waterhemp control by 8 wk after postemergence herbicide treatment (WAPT). In soybean, common waterhemp control was less than 40% by 8 WAPT with postemergence protox-inhibiting herbicides lactofen and acifluorfen. However, preemergence protox-inhibiting herbicides sulfentrazone and flumioxazin gave greater than 85% common waterhemp control in both years. The greatest common waterhemp control in soybean was with glyphosate alone, alachlor + metribuzin, alachlor followed by (fb) glyphosate, and S-metolachlor + metribuzin fb glyphosate.
Sugarcane Tolerance and Italian Ryegrass (Lolium multiflorum) Control with Paraquat
Authors: Griffin James L. , Miller Donnie K. , Ellis Jeffrey M. , Clay Patrick A.
Published: July 2006

Paraquat applied from mid-February through early April over 2 yr was evaluated for sugarcane tolerance and Italian ryegrass control. Sugarcane 31 cm tall at application was injured 16 to 25% and 8 to 14% 28 and 56 d, respectively, after mid-March application of paraquat at 0.35 or 0.70 kg ai/ha. Early-April application to 61-cm-tall sugarcane caused 13 to 25% injury. The observed injury was not reflected in reduced sugarcane shoot population or height or sugarcane or sugar yield when compared with diuron, the standard herbicide treatment. Italian ryegrass control 28 d after the mid-February application of paraquat alone at 0.53 or 0.70 kg/ha was variable, ranging from 80% in 1994 to no more than 66% in 1995. For each year, diuron at 3.2 kg/ha in combination with both rates of paraquat increased Italian ryegrass control 28 d after the mid-February application 11 to 17 percentage points. At 56 d after the mid-February application, addition of diuron proved beneficial only in 1994 when the paraquat and diuron combinations controlled ryegrass 93% compared with no more than 62% for paraquat applied alone. In contrast, Italian ryegrass was controlled the second year no more than 80% 56 d after the mid-February application of paraquat alone or with diuron. Paraquat applied at 0.70 kg/ha with diuron in mid-March controlled Italian ryegrass 80 and 86% 28 d after treatment in 1994 and 1995, respectively. For the standard herbicides metribuzin, terbacil, and diuron applied in mid-March, weed control was no greater than 38%. Although differences in Italian ryegrass control among herbicide treatments were observed, efficacy was sufficient to reduce weed competition such that sugarcane growth and yield were not negatively affected.
Control of Silvery-Thread Moss (Bryum argenteumHedw.) in Creeping Bentgrass (Agrostis palustrisHuds.) Putting Greens
Authors: Burnell Keith D. , Yelverton Fred H. , Neal Joseph C. , Gannon Travis W. , McElroy J. Scott
Published: July 2006

Field experiments were conducted to evaluate chemicals for silvery-thread moss control and bentgrass turfgrass quality. Treatments included iron (Fe)-containing products, nitrogen fertilizers, Ultra Dawn dishwashing detergent (UD) at 3% (v/v), and oxadiazon. In general, greater silvery-thread moss control was achieved with Fe-containing products. Ferrous sulfate at 40 kg Fe/ha plus ammonium sulfate at 30 kg N/ha, a combined product of ferrous oxide, ferrous sulfate, and iron humates (FEOSH) at 125 kg Fe/ha, and a combined product of iron disulfide and ferrous sulfate (FEDS) at 112 kg Fe/ha reduced silvery-thread moss populations 87, 81, and 69%, respectively, 6 wk after initial treatment (WAIT). UD reduced silvery-thread moss populations 57% 6 WAIT. The addition of oxadiazon to Fe-containing treatments did not improve silvery-thread moss population reduction. Other experiments evaluated two formulations of chlorothalonil, each applied at two rates, chlorothalonil with zinc at 9.5 and 17.4 kg ai/ha and chlorothalonil without zinc at 9.1 and 18.2 kg/ ha, and two spray volumes (2,038 and 4,076 L/ha). Greater silvery-thread moss population reduction was observed at Jefferson Landing in 1999 compared with Elk River in 1999 and 2000. Rainfall events at Elk River in 1999 and 2000 within 24 h after application and no rain at Jefferson Landing may account for variation in performance of products between sites. However, no difference in chlorothalonil formulation, rate, or spray volume was observed in any location or year. These data indicate that Fe-containing fertilizers or chlorothalonil can be used to reduce silvery-thread moss populations in creeping bentgrass putting greens.
Efficacy of Methyl Bromide Alternatives on Purple Nutsedge (Cyperus rotundus) Control in Tomato and Pepper
Authors: Gilreath James P. , Santos Bielinski M.
Published: July 2006

Field trials were conducted to compare the effect of various soil fumigants along with in-bed pebulate and row-middle metribuzin applications on purple nutsedge control and on tomato and bell pepper growth and yield. Treatments consisted of combinations of soil fumigants, pebulate, and metribuzin. Fumigants levels were (1) untreated control, (2) methyl bromide (MBr) + chloropicrin (Pic) (67 + 33%, respectively), (3) Pic, (4) metham, (5) dazomet, and (6) 1,3-dichloropropene (1,3-D) + Pic (83 + 17%, respectively). Pebulate levels were either applied in-bed or not applied. Row middles were either sprayed with metribuzin or untreated. In both crops, purple nutsedge populations were independently influenced by fumigants and pebulate applications, with the highest number of purple nutsedge plants in the untreated control. The addition of pebulate reduced purple nutsedge populations in all treatments. In tomato trials, the yield was affected by fumigants, with the highest losses (53 and 50% reductions in fruit number and weight) observed in the nonfumigated control. In pepper trials, fruit number and weight were individually influenced by fumigants and metribuzin sprayings. Application of metribuzin to row middles increased yields 10% relative to nontreated plots.
Ground Ivy (Glechoma hederacea) Populations Respond Differently to 2,4-D or Triclopyr
Authors: Kohler Eric A. , Throssell Clark S. , Reicher Zachary J.
Published: July 2006

Ground ivy is an invasive, perennial, broadleaf weed common in turf sites. A recent survey of lawn care professionals suggests ground ivy populations respond differently to herbicides. Our study was conducted to determine the variation in response among and within ground ivy populations to 2,4-D or triclopyr application. Ground ivy populations were sampled from nine sites in the United States and Canada. Leaf width, petiole length, and internode length varied by population by as much as 31, 36, and 45%, respectively. In a greenhouse study, applying 4.5 kg/ha 2,4-D or 0.9 kg/ha triclopyr to all populations resulted in a phytotoxic response that varied according to population by as much as 47% for 2,4-D and 31% for triclopyr. Random-amplified polymorphic DNA analysis identified 52 genotypes in the nine populations, and these genotypes varied in response to 2,4-D application in some populations. Difficulty in control of ground ivy with 2,4-D or triclopyr may be because of the presence of ecotypes and biotypes.
2,4-D Rate Response, Absorption, and Translocation of Two Ground Ivy (Glechoma hederacea) Populations
Authors: Kohler Eric A. , Throssell Clark S. , Reicher Zachary J.
Published: July 2006

Ground ivy is a stoloniferous, perennial weed that persists in lawn turf. With the widespread use of 2,4-D on turf sites, the development of 2,4-D–tolerant ground ivy is a possibility. Ground ivy populations showed a highly variable response to foliar 2,4-D application. Ground ivy from Nebraska (NE) was tolerant to 2,4-D, whereas Ohio (OH) ground ivy was susceptible. The 2,4-D–susceptible OH population absorbed 37% more foliar-applied14C–2,4-D than the 2,4-D–tolerant NE population. Although OH and NE populations total translocation of applied14C was similar and averaged 5%, the OH population translocated 42% more toward the apical meristem of the primary stolon than the NE population, primarily because of the OH population's higher14C–2,4-D absorption. The variation in response to 2,4-D found between these two populations occurred after exposure of roots to 2,4-D, but the effect was less pronounced. These results suggest that the difference in foliar uptake may partially contribute to differences in response to 2,4-D between these two populations. Likewise, differences in acropetal translocation may contribute to the differential sensitivity of 2,4-D–tolerant and –susceptible ground ivy populations.
Phytotoxicity of Clippings from Creeping Bentgrass Treated with Glyphosate
Authors: Goss R. M. , Gaussoin R. E. , Martin A. R.
Published: July 2006

Recent advances in genetic engineering have led to the development of glyphosate-resistant (GR) crops for genetic markers and selective weed control. The effects of glyphosate residue on turfgrass clippings could be toxic to non-GR species. The objective of this experiment was to determine whether glyphosate would retain activity within clippings of creeping bentgrass when applied to Kentucky bluegrass and perennial ryegrass. Greenhouse-grown ‘Penncross’ and GR ‘ASR-368’ were treated with glyphosate at 2.24 kg/ha. Clippings were collected 1, 3, 7, and 12 d after application and applied to greenhouse-grown Kentucky bluegrass and perennial ryegrass. Kentucky bluegrass and perennial ryegrass dry weight and percent cover were reduced by clippings receiving glyphosate that were harvested 1 and 3 d after glyphosate application from both susceptible and resistant creeping bentgrass. Results indicate that glyphosate remains active in clippings for up to 3 d after treatment within creeping bentgrass clippings. Glyphosate-applied creeping bentgrass clippings will need to be managed to prevent injury to susceptible species.
Natural Product Herbicides for Control of Annual Vegetation Along Roadsides
Authors: Young Steve L.
Published: July 2006

Natural product herbicides for vegetation control are being considered as alternatives to synthetic herbicides by many public agencies. Studies were conducted along roadsides at the Hopland Research and Extension Center (HREC) in 2001 and 2002 and on California State Route 29 (SR29) in 2002 to evaluate acetic acid, pine oil, and plant essentials compared with glyphosate for control of herbaceous vegetation. In 2001, annual grass control after a single application of pine oil at HREC was 40% or less effective, whereas acetic acid was at least 79% effective. A second application of pine oil or acetic acid did not control regrowth or new plants. In 2002, plant essentials was the most effective (>80%) natural product at HREC for control of annual grasses, except slender oat. Pine oil often provided similar control of slender oat as plant essentials (71 and 69%, respectively). At SR29, five applications of acetic acid provided 83% or better control of slender oat, hare barley, medusahead, and broadleaf filaree. Plant essentials and pine oil controlled hairy vetch, broadleaf filaree, and hare barley at least 83%, but yellow starthistle, soft chess, buckhorn plantain, and medusahead control never exceeded 85%. Glyphosate controlled all vegetation in these experiments with one or two applications. The cost of one or more applications of the natural products was greater than 10 times the cost of using one or two applications of glyphosate. Natural products were neither efficaciously nor economically comparable with glyphosate for control of annual roadside vegetation.
Addition of Nonionic Surfactant to Glyphosate Plus Chlorimuron
Authors: Norsworthy Jason K. , Grey Timothy L.
Published: July 2006

Field studies were conducted in South Carolina and Georgia to evaluate weed control and soybean tolerance and yield after nonionic surfactant addition to combinations of chlorimuron plus an adjuvant-containing glyphosate formulation. Treatments included glyphosate alone, at 420 or 840 g ae/ha, or in combination with 6 or 9 g ai/ha chlorimuron and all possible combinations with or without 0.25% (v/v) nonionic surfactant. Other treatments included a weed-free and nontreated check. Chlorimuron plus glyphosate improved entireleaf, smallflower, and tall morningglory control over glyphosate alone, but nonionic surfactant addition did not further improve the control of any species, except tall morningglory. Up to 31% early-season injury was observed with the three-way mixture. Soybean injury was greater, and yields were reduced in one of three trials when nonionic surfactant was added to chlorimuron plus glyphosate combinations. This research indicates that there would be no benefit from the nonionic surfactant addition to this adjuvant-containing glyphosate formulation when combined with chlorimuron.
Acrolein Reduces Biomass and Seed Production of Potamogeton pectinatus in Irrigation Channels
Authors: Bentivegna Diego J. , Fernández Osvaldo A. , Burgos María A.
Published: July 2006

Chemical weed control with acrolein has been shown to be a lower cost method for reducing submerged plant biomass of sago pondweed in the irrigation district of the Lower Valley of Rio Colorado, Argentina (39°10′S–62°05′W). However, no experimental data exist on the effects of the herbicide on plant growth and its survival structures. Field experiments were conducted during 3 yr to evaluate the effect of acrolein on growth and biomass of sago pondweed and on the source of underground propagules (i.e., rhizomes, tubers, and seeds). Plant biomass samples were collected in irrigation channels before and after several herbicide treatments. The underground propagule bank was evaluated at the end of the third year. Within each treatment, plant biomass was significantly reduced by 40 to 60% in all three study years. Rapid new plant growth occurred after each application; however, it was less vigorous after repeated treatments. At the end of the third year at 3,000 m downstream from the application point, plant biomass at both channels ranged from 34 to 3% of control values. Individual plant weight and height were affected by acrolein treatments, flowering was poor, and seeds did not reach maturity. After 3 yr, acrolein did not reduce the number of tubers. However, they were significantly smaller and lighter. Rhizomes fresh weight decreased by 92%, and seed numbers decreased by 79%. After 3 yr of applications, operational functioning of the channels could be maintained with fewer treatments and lower concentrations of acrolein.
Determining Exposure to Auxin-Like Herbicides. I. Quantifying Injury to Cotton and Soybean
Authors: Sciumbato Audie S. , Chandler James M. , Senseman Scott A. , Bovey Rodney W. , Smith Ken L.
Published: July 2006

Crop injury caused by drift of auxin-like herbicides has been a concern since their development. Research was conducted to describe a method of quantifying injury from auxin-like herbicides as a first step in determining crop damage. Reduced rates of 2,4-D, dicamba, and triclopyr were applied to cotton and soybean plants in the three- to six-leaf stage in field and greenhouse studies. Injury to leaves and stems were evaluated separately, and the values were combined so that one injury estimate was obtained for each individual plant rated. Injury symptoms were typical for auxin-type herbicides and ranged from slight bending of stems or petioles and wrinkled leaves to necrosis. Specific descriptions of leaf and stem injury levels were used to describe plant injury consistently. These descriptions were very detailed for the lower injury levels, but the characterizations became more general as the injury increased because of the prominence of factors such as necrosis. The injury evaluation method provided repeatable results for each herbicide and herbicide rate used. This injury evaluation method has many possible uses in auxin-like herbicide research and lays the foundation for forecasting the impact of early-season injury to cotton and soybean yield.
Use of Quinclorac for Large Crabgrass (Digitaria sanguinalis) Control in Newly Summer-Seeded Creeping Bentgrass (Agrostis stolonifera)
Authors: Hart Stephen E. , Lycan Darren W. , Murphy James A.
Published: July 2006

Field trials were conducted in 2000 and 2001 in New Jersey to evaluate quinclorac and siduron for large crabgrass control in summer-seeded creeping bentgrass (‘L-93’). Bentgrass was surface seeded on June 30 and June 26 in 2000 and 2001, respectively. Treatments consisted of preemergence (PRE) applications of siduron at 3.4, 5.0, and 6.7 kg ai/ha and PRE and postemergence (POST) applications of quinclorac at 0.4, 0.6, 0.8, and 1.7 kg ai/ha. POST applications were timed to a crabgrass growth stage of three leaves to one tiller. All POST quinclorac applications included methylated seed oil at 1% (v/v). Percent crabgrass cover in untreated plots at 30 d after planting (DAP) averaged 10 and 50% in 2000 and 2001, respectively. All PRE treatments, with the exception of quinclorac applied at 0.4 kg/ha in 2001, reduced crabgrass cover by 80% or more at 30 DAP. Crabgrass control decreased in late August when siduron and quinclorac were applied at the lower rates in 2001. PRE quinclorac applications at the rate of 0.6 kg/ha or higher in 2000 or 1.7 kg/ha in 2001 caused significant thinning of the bentgrass stand at 30 DAP. All POST quinclorac treatments provided excellent crabgrass control in 2000, but the 0.8-kg/ha or higher rate was required to reduce crabgrass infestation levels by at least 80% in 2001. All POST quinclorac applications caused significant chlorosis to the creeping bentgrass in both years. However, significant thinning of the bentgrass stand was not evident, with the exception of 1.7 kg/ha, in 2001. These studies suggest that PRE applications of siduron should be used for the highest level of creeping bentgrass safety in summer restoration projects. The use of quinclorac should be limited to POST applications to control escaped crabgrass once the newly emerging creeping bentgrass has become well established.
Influence of Formulation on the Activity and Persistence of Pendimethalin
Authors: Hatzinikolaou Ageliki S. , Eleftherohorinos Ilias G. , Vasilakoglou Ioannis B.
Published: July 2006

The activity of emulsifiable concentrate (EC) formulation of pendimethalin was studied using a petri dish bioassay based on root response of corn, oat, sorghum, and sugar beet grown in soil. Furthermore, the oat bioassay was used to determine the activity of EC, microencapsulated (ME), and water-dispersible granule (WDG) formulations of pendimethalin. Also, field persistence in soil of these pendimethalin formulations was studied with petri dish and pot bioassays, based on root response of oat and sugar beet. All bioassays indicated that activity of all pendimethalin formulations was increased with increasing herbicide concentration. In silty clay loam soil, oat and sugar beet exhibited the highest sensitivity to EC-pendimethalin concentrations and corn the lowest; sorghum showed intermediate herbicide sensitivity. EC of pendimethalin showed the highest activity on oat and ME pendimethalin the lowest; WDG-pendimethalin showed similar activity to that of ME pendimethalin. Field persistence was significantly increased with increasing rate of application, but it was slightly increased by the ME formulation.
Wheat Tolerance to AE F130060 00 plus AE F115008 00 as Affected by Time of Application and Rate of the Safener AE F107892
Authors: Crooks H. Lane , York Alan C. , Jordan David L.
Published: July 2006

Soft red winter wheat response to the herbicides AE F130060 00 plus AE F115008 00 applied alone or with the safener AE F107892 at the three-leaf, two-tiller, and six-tiller growth stages was determined in a field experiment in North Carolina. AE F130060 00 at 25 g ai/ha plus AE F115008 00 at 5 g ai/ha, twice the anticipated use rate, applied with safener injured wheat 9% but did not affect grain yield, grain test weight, number of spikes, number of kernels per spike, or kernel weight. Results were similar with safener at herbicide–safener ratios of 1:1 and 1:3 regardless of the wheat growth stage at application. Without the safener, AE F130060 00 plus AE F115008 00 applied at the three-leaf, two-tiller, and six-tiller growth stages injured wheat an average of 27% and reduced grain yields 5, 5, and 11%, respectively. Yield losses were attributed to reduced numbers of kernels per spike. AE F130060 00 at 12.5 g/ha plus AE F115008 00 at 2.5 g/ha plus AE F107892 at 15 g ai/ha did not affect grain yield or yield components.
Management Practices Influencing Herbicide Resistance in Wild Oat
Authors: Beckie Hugh J. , Hall Linda M. , Meers Scott , Laslo James J. , Stevenson F. Craig
Published: July 2006

A 3-yr study was conducted in Wheatland County, Alberta to determine if agronomic practices of growers influenced the occurrence of herbicide resistance in wild oat. Wild oat seeds were collected in 33 fields in 1997 and in 31 fields in each of 1998 and 1999 (one field per grower). Seedlings were screened for resistance to two acetyl-CoA carboxylase (ACCase) inhibitors, imazamethabenz, an acetolactate synthase (ALS) inhibitor, and triallate, a thiocarbamate herbicide. A questionnaire on herbicide resistance awareness and management practices was completed by each grower. Both ACCase and ALS inhibitor resistance in wild oat were linked to a lack of crop rotation diversity. In addition, ALS inhibitor–resistant wild oat was associated with conservation-tillage systems and recent use of herbicides with that mode of action. Results of this study suggest that timely tillage and inclusion of fall-seeded and perennial forage crops in rotations will effectively slow the selection of resistance in this grass species.
Management of Acetolactate Synthase (ALS)–Resistant Common Cocklebur (Xanthium strumarium) in Soybean
Authors: Schmidt Lance A. , Talbert Ronald E. , McClelland Marilyn
Published: July 2006

A fixed-plot management study for control of acetolactate synthase (ALS)–resistant common cocklebur in soybean was initiated in 1994 at Fayetteville, AR. Three susceptible and three imazaquin-resistant common cocklebur plants were transplanted into the field, and seed (burs) were distributed throughout the plots in the fall of 1994. Herbicide treatments included imazaquin, chlorimuron, and chlorimuron plus metribuzin applied each year from 1995 through 1999 and herbicide rotations containing ALS inhibitors and herbicides with alternative modes of action. Effectiveness of management systems and the dynamics of the development of common cocklebur resistance, including development of resistance to imazaquin and chlorimuron, were evaluated. Imazaquin controlled susceptible common cocklebur populations in 1995 but not the resistant population, resulting in significant soybean yield reduction. By the end of the 1996 season, the resistant biotype dominated imazaquin plots, and a high level of cross-resistance to chlorimuron was observed in the population. Resistant populations were reduced by non-ALS herbicide programs of sulfentrazone plus clomazone applied preemergence (PRE), metribuzin plus clomazone applied PRE followed by bentazon applied postemergence (POST), and transgenic herbicide programs of glyphosate and glufosinate applied POST. Rotating ALS inhibitors with non–ALS-inhibiting heribicides may slow the development of resistance, but resistant individuals may eventually dominate the population.
White Bean Sensitivity to Preemergence Herbicides
Authors: Soltani Nader , Shropshire Christy , Cowan Todd , Sikkema Peter
Published: July 2006

White bean producers have a limited number of herbicide options available for annual grass and broadleaf weed control. Tolerance of two white bean cultivars to preemergence (PRE) applications ofS-metolachlor,S-metolachlor + imazethapyr, flumetsulam +S-metolachlor, cloransulam-methyl, clomazone, clomazone + imazethapyr, and clomazone +S-metolachlor at the maximum labeled rate in soybean (1×) and twice the labeled rate (2×) were studied at two Ontario locations (Exeter and Ridgetown) in 2001 and 2002.S-Metolachlor, clomazone, and clomazone +S-metolachlor generally had no negative effect on plant height, dry weight, maturity, and yield.S-Metolachlor + imazethapyr and clomazone + imazethapyr reduced plant height, dry weight, and yield as much as 21, 42, and 24%, respectively. Flumesulam +S-metolachlor and cloransulam-methyl reduced plant height, dry weight, and yield as much as 39, 58, and 43%, respectively. White beans are tolerant to PRE applications ofS-metolachlor, clomazone, and clomazone +S-metolachlor. White beans are sensitive to PRE applications ofS-metolachlor + imazethapyr, flumetsulam +S-metolachlor, clomazone + imazethapyr, and cloransulam-methyl.
Weed Management with Fomesafen Preemergence in Glyphosate-Resistant Cotton
Authors: Stephenson Daniel O. , Patterson Michael G. , Faircloth Wilson H. , Lunsford James N.
Published: July 2006

Field studies were conducted in Alabama in 1998 and 1999 to evaluate fomesafen preemergence (PRE) in glyphosate-resistant cotton. Fomesafen (0.3 and 0.4 kg ai/ha), fluometuron (1.4 kg ai/ha), and pyrithiobac (0.05 kg ai/ha) were applied alone or in tank mixtures. Glyphosate (0.4 kg ae/ha) was applied postemergence over-the-top (POT) and postemergence directed (PD). Regardless of PRE treatment, POT followed by (fb) PD applications of glyphosate were necessary for greater than 82% sicklepod control at midseason. In the absence of glyphosate, fomesafen, and fomesafen-containing tank mixtures controlled common cocklebur andIpomoeaspecies 77 and 72%, respectively, 14 d after PD application. However, two applications of glyphosate were needed for >94% season-long control of common cocklebur andIpomoeaspecies because of continued germination throughout the growing season. Postemergence applications of glyphosate added a 1,000 kg/ha seed cotton yield increase to all PRE treatments at both locations. Common cocklebur,Ipomoeaspecies, and sicklepod control was not significantly increased by the addition of fomesafen PRE tank mixtures fb glyphosate postemergence as compared with glyphosate postemergence only.
Reduced Tillage, Rye Residues, and Herbicides Influence Weed Suppression and Yield of Pumpkins
Authors: Rapp Heidi S. , Bellinder Robin R. , Wien H. Chris , Vermeylen Francoise M.
Published: July 2006

Field experiments were conducted to study the effects of various tillage and mulching practices on fruit maturity and weed suppression in pumpkins. Conventional tillage (CT), disking, no tillage with rye removed (RR), no tillage with standing rye (SR), and strip tillage (ST) were evaluated with and without ethalfluralin plus halosulfuron (1.5 plus 0.036 kg ai/ha, respectively) applied preemergence. In 2001, when heavy rain after herbicide application caused significant crop injury, the herbicides delayed maturity and significantly reduced yields of mature pumpkins within each herbicide treatment, total yields did not differ with tillage. In 2002, weed populations were significantly greater than those in 2001, and in 2002, regardless of herbicides, yields of mature fruit were greater in tillage treatments with higher rye residues (SR, ST). Although weed populations were less in one year than the other, herbicides provided effective control in both seasons, and RR, ST, and SR effectively suppressed weeds compared with CT. Averaged over treatments, greater yield losses were attributable to weed competition (42%) in 2002 than to herbicide injury (32%) in 2001.
Potential for Preseason Herbicide Application to Prevent Weed Emergence in the Subsequent Growing Season. 1. Identification and Evaluation of Possible Herbicides
Authors: Walsh Michael J. , Devlin Richard D. , Powles Stephen B.
Published: July 2006

The earliest possible seeding of wheat crops in the southern Australian dryland cropping zone is prevented by the lack of a weed control practice that adequately controls initial weed seedling emergence at the start of the growing season. The objective of this study was to determine the potential for using residual herbicides applied up to 1 mo before the start of the growing season to control rigid ryegrass seedlings that emerge after the season-opening rains. In a series of glasshouse studies, S-metolachlor and propyzamide were found to effectively persist on the soil surface through prolonged exposure to hot, dry, and intense sunlight conditions, preventing the establishment of rigid ryegrass seedlings. In addition, these herbicides caused little or no effect on subsequently seeded wheat. It also was determined that S-metolachlor had the potential to retain efficacy on rigid ryegrass seedlings after 12 wk of exposure on the soil surface to these conditions. These studies have identified two herbicides with the potential for use at the novel application timing, i.e., before the commencement of the growing season, in Mediterranean climates of southern Australia.
Annual Bluegrass (Poa annua) Resistance to Simazine in Mississippi
Authors: Hutto K. C. , Coats G. E. , Taylor J. M.
Published: July 2006

Research was conducted in winter of 2000 and spring of 2001 to determine the extent of simazine-resistant annual bluegrass in Mississippi. Samples of annual bluegrass seed or mature plants were collected from 71 locations across the state and grown in the greenhouse. Four weeks after treatment with 22.4 kg ai/ha simazine (10× rate), samples from 31 of 71 locations (30 golf courses and one nongolf course) evaluated in the greenhouse had simazine-resistant annual bluegrass plants. Thus, 43% of the golf courses tested in the greenhouse had triazine-resistant annual bluegrass present. When natural field populations were treated with an equivalent simazine rate, simazine-resistant annual bluegrass plants were observed in 90% of the sites found to be resistant in the greenhouse screen.
A Laboratory Exercise for Teaching Depth of Weed Emergence Concepts
Authors: Gibson Lance , Liebman Matt
Published: July 2006

The influence of weed seed burial depth on seedling emergence is a common and important topic in undergraduate weed science courses. A laboratory exercise was developed at Iowa State University to actively demonstrate changes in weed seedling emergence with increased seed-burial depth. Twenty-five ivyleaf morningglory and wild mustard seeds were sown in pots in monoculture, and the number of emerging seedlings was counted for 3 wk. The results from two semesters were analyzed to determine whether the experiment was successful in meeting its intended outcomes. Assessment of student perceptions and attitudes indicated that the activity increased students' understanding of weed biology; improved students' critical thinking, reading, and writing skills; and improved students' ability to make scientific observations, interpret graphical information, and analyze and summarize research data.
Sweet Corn Cultivar Sensitivity to Bentazon
Authors: Diebold Shane , Robinson Darren , Zandstra John , O'Sullivan John , Sikkema Peter H.
Published: July 2006

Five sweet corn cultivars were evaluated for tolerance to bentazon in five field experiments conducted during 2 yr in Ontario. Bentazon was applied postemergence (POST) at 1.08 and 2.16 kg ai/ha, the highest registered rate and twice the highest registered rate, respectively, used in sweet corn in Ontario. When bentazon was applied POST at 1.08 and 2.16 kg/ha to sweet corn cultivar ‘DelMonte 2038’, injury included plant stunting and leaf damage ranging from 6 to 69% and 15 to 90%, respectively. Plant height was reduced to 48 and 100% of the untreated check when treated with bentazon at 1.08 and 2.16 kg/ha, respectively. The visual injury and height reductions were reflected in the marketable yields, which were reduced to 94% when treated with bentazon. Significant reductions in height and marketable yield were not observed in the other four cultivars tested. No correlation was observed between bentazon sensitivity and endosperm genotype. Based on visual injury ratings, sweet corn height, and marketable yield, it was concluded that ‘Calico Belle’, ‘GH 2684’, ‘Reveille’, and ‘Rival’ are tolerant to POST application of bentazon.
Herbicide-Resistant Grass Weed Development in Imidazolinone-Resistant Wheat: Weed Biology and Herbicide Rotation
Authors: Rainbolt Curtis R. , Thill Donald C. , Yenish Joseph P. , Ball Daniel A.
Published: July 2006

A general life cycle model was modified to demonstrate how agronomic practices and weed biology factors affect the rate of appearance of herbicide-resistant downy brome, jointed goatgrass, and wild oat in Pacific Northwest wheat cropping systems. The model suggests herbicide rotation strategies for cropping systems that include imidazolinone-resistant wheat as a weed management tool. Simulation of continuous annual imidazolinone-resistant winter wheat and imazamox herbicide use resulted in the resistant soil seed banks of downy brome, jointed goatgrass, and wild oat surpassing their susceptible soil seed banks in 5, 7, and 10 yr, respectively. Reducing the initial seed bank density of downy brome before beginning a rotation that includes imidazolinone-resistant winter wheat reduces the likelihood of selecting for herbicide-resistant biotypes. The best simulated management option for reducing the total jointed goatgrass soil seed bank in low-precipitation areas is an imidazolinone-resistant winter wheat–fallow rotation. Rotations that include winter and spring crops and rotations that include non–group 2 herbicides minimize herbicide resistance selection pressure and reduce the wild oat soil seed bank.
Diuron Sorption by Pine-Bark Substrate and Foliar vs. Root Absorption by Yellow Woodsorrel (Oxalis stricta)
Authors: Simpson Carey V. , Wehtje Glenn , Gilliam Charles H. , Sibley Jeff L. , Altland James E.
Published: July 2006

Postemergence-applied diuron effectively controls yellow woodsorrel in nursery crops grown in pine bark–based container substrate. Whether the phytotoxicity of diuron on yellow woodsorrel is exclusively the result of foliar activity or is partially the result of root-based activity has not been determined. Application in which diuron was allowed to contact both the foliage and the pine bark–based substrate provided 84% control as determined by shoot fresh-weight reduction relative to that of a nontreated control. Foliar-only and root-only applications provided 52 and 12% shoot fresh-weight reduction, respectively. Absorption and translocation of foliar-applied diuron by yellow woodsorrel was evaluated using radiotracer techniques. After 24 h, 86% of the applied diuron had been absorbed, and 76% of the amount applied remained in the treated leaflet, indicating minimal translocation. Diuron sorption by the pine bark–based substrate was evaluated using radiotracer techniques. After 3 h, less than 6% of applied diuron remained in the aqueous phase, indicating 94% sorption. Exposing yellow woodsorrel roots to diuron concentrations as low as 0.50 mg/L resulted in injury, and concentrations equal to or greater than 10 mg/L resulted in death. Calculations described herein indicate the concentration that probably would occur within the aqueous solution held within the substrate following a 1.12-kg ai/ha application is sufficient to be phytotoxic to yellow woodsorrel. Thus, root-based absorption is a contributing factor in the overall efficacy of postemergence-applied diuron in controlling yellow woodsorrel.
Lateral Spread of Glyphosate-Resistant Transgenic Creeping Bentgrass (Agrostis stolonifera) Lines in Established Turfgrass Swards
Authors: Gardner David S. , Danneberger Tom K. , Nelson Eric K.
Published: July 2006

Genetically engineered varieties of creeping bentgrass, resistant to glyphosate, have been developed. Studies were initiated in 2000 and 2001 to examine the relative competitive lateral spread of several transformed lines of creeping bentgrass, nontransformed controls, and cultivar standards. Five-centimeter-diameter vegetative plugs of creeping bentgrass were transplanted into a 1-yr-old stand of perennial ryegrass in Columbus, OH, and 10-yr-old bermudagrass or 10-yr-old St. Augustinegrass in Loxley, AL. Plots were watered to prevent moisture stress to either the bentgrass plugs or surrounding turf swards. Monthly average diameter of the creeping bentgrass was determined by measuring the longest spread and shortest spread. At the end of the experiment, no differences (P = 0.05) in lateral spread were observed between individual lines of transgenic bentgrass, standard cultivars, and nontransformed control lines. Lateral spread of transgenic lines was similar to or less than their nontransformed parent and the standard cultivars tested. Results indicate that glyphosate-resistant creeping bentgrass lines do not spread laterally more than nontransgenic lines. Therefore, if the glyphosate-resistant creeping bentgrass escaped into surrounding turfgrass swards, the potential for spread would not be greater than other creeping bentgrass cultivars currently in use.
Herbage Yield Losses in Perennial Pasture Due to Canada Thistle (Cirsium arvense)
Authors: Grekul Chad W. , Bork Edward W.
Published: July 2006

Although the impact of Canada thistle (CT) on annual crop production is relatively well established, few investigations report on this weed's impact within perennial pastures. This field study assessed herbage yield losses within eight central Alberta pastures from 1999 to 2001. Each pasture was sampled in 1999 to quantify thistle and herbage biomass within 25 permanent plots. CT was controlled in 2000 and the response of vegetation measured in 2000 and 2001. Before removal, significant negative relationships (P < 0.05) between thistle abundance and herbage were noted at six sites. After thistle removal, herbage at several sites displayed positive responses. Both thistle density and biomass adequately predicted herbage yield loss. Yield losses due to CT can be substantial, peaking at 2 kg/ha for each kilogram of standing thistle biomass and 4.3 kg/ha with each additional thistle stem per square meter. Demonstrated yield losses were variable among sites however, likely due to factors such as heterogeneity in soils, available moisture, and variation in disturbance history or pasture vegetation composition. CT management in perennial pastures of western Canada may enhance pasture production, but further research is required to reliably predict the ability of pastures to respond.
Effects of Phosphorus Fertilization on the Area of Influence of Common Lambsquarters (Chenopodium album) in Lettuce
Authors: Santos Bielinski M. , Dusky Joan A. , Stall William M. , Gilreath James P.
Published: July 2006

Area-of-influence experiments were conducted on high–organic matter soils to assess the effect of common lambsquarters distances from ‘South Bay’ lettuce on yield and quality under two phosphorus (P) regimens. P was applied either banded (125 kg P/ha) or broadcast (250 kg P/ha) before lettuce planting. Lettuce plants were harvested at 0, 25, 50, 75, 100, and 125 cm from each side of the common lambsquarters plant after season-long interference. The regression equations were y = 0.40 + 0.36/(1 + e−0.09(x−52.5)),r2= 0.92, for banded P; and y = 0.40 + 0.29/(1 + e−0.07(x−69.3)),r2= 0.94 for broadcast P. Banded P produced 9% more fresh weight per head than the broadcast P treatment under weed-free conditions. Within the broadcast P treatments, common lambsquarters growing at 125 and 100 cm did not affect fresh weight of harvested lettuce. Values for fresh weight per head declined 18, 34, 38, and 38% when lettuce grew at 75, 50, 25, and 0 cm distance from common lambsquarters, respectively. Fresh weight of lettuce in banded P treatments was reduced only at 50, 25, and 0 cm distance from common lambsquarters plants, representing 31, 44, and 44% less than its weed-free control, respectively. Banding P at 50% (125 kg/ha) of the recommended broadcast rate reduced the area of influence of common lambsquarters with lettuce.
Emergence and Growth of Trumpetcreeper (Campsis radicans) as Affected by Rootstock Size and Planting Depth
Authors: Edwards Jeffrey T. , Oliver Lawrence R.
Published: July 2006

Trumpetcreeper, a deciduous, perennial vine found in the midwestern and southeastern United States, causes crop losses through direct competition and by crop entanglement, and control measures include both herbicides and tillage. The regenerative capacity of trumpetcreeper rootstocks of varying length and diameter when planted at different depths was evaluated in greenhouse experiments in Arkansas. Deeper placement of rootstocks delayed trumpetcreeper emergence but had no effect on shoot growth after emergence. Larger rootstock segments produced more shoots per plant and more total biomass production. However, smaller rootstock segments produced more shoots and total biomass per centimeter of rootstock. Overall, decreasing trumpetcreeper rootstock size will delay shoot emergence but may not result in increased long-term control.