bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Ragweed Parthenium (Parthenium hysterophorus) and Associated Weeds
Authors: Singh Samunder , Yadav Ashok , Balyan Rajender S. , Malik Ram K. , Singh Megh
Published: July 2006

Field experiments were conducted to evaluate control of 90- to 100-cm-tall ragweed parthenium in a noncropped situation in Haryana State, India, during 2000 and 2001. Atrazine, 2,4-D ethyl ester, atrazine plus 2,4-D, metribuzin, metsulfuron, chlorimuron, glufosinate with and without surfactant, glyphosate with and without surfactant, and glyphosate formulations MON 8793 and 8794 were sprayed on ragweed parthenium. Also, the effect of water quality was studied with flat-fan and flood-fan nozzles using glyphosate and its formulation MON 8793 against ragweed parthenium and associated weeds. Glyphosate MON 8793 and 8794 at 3.6 kg ae/ha provided excellent control of ragweed parthenium followed by glyphosate at 2.7 or 5.4 kg/ha, with no recovery until 18 wk after treatment (WAT). Addition of 0.1% v/v surfactant (MON 0818) to glyphosate at 2.7 kg/ha provided similar control to that of glyphosate alone at 5.4 kg/ha. Other herbicides failed to provide satisfactory control of ragweed parthenium. In the water quality study, glyphosate at 2.7 and 5.4 kg/ha and glyphosate MON 8793 at 2.7 and 3.6 kg/ha provided similar control of ragweed parthenium at 18 WAT. Glyphosate was antagonized less by tap water (0.45 mM Ca) than canal (0.7 mM Ca) and hand-pump water (1 mM Ca). Neither glyphosate nor glyphosate MON 8793 provided good control of purple nutsedge, velvetleaf, garden spurge, threelobe false mallow, jimsonweed, giant milkweed, Indian jujube, or tropical spiderwort, but crowfootgrass, green foxtail, sprawling signalgrass, and spiny amaranth were controlled. Glyphosate at 5.4 kg/ha and glyphosate MON 8793 at 3.6 kg/ha provided more than 80% control of bermudagrass at 8 WAT, which was significantly better than the 2.7 kg/ha rate. Flat-fan nozzles provided better efficacy of applied herbicides than flood-fan nozzles at 4 WAT on ragweed parthenium.
Effect of Separate and Combined Applications of Herbicides on Weed Control and Yield of Sugar Beet
Authors: Abdollahi Farzin , Ghadiri Hossein
Published: July 2006

Field studies were conducted to investigate the effects of different rates of herbicides on weed control, agronomic characteristics, and quality of sugar beet at Shiraz, Iran, in 2000 and 2001. Separate and combined applications of herbicides, including 14 combinations and different rates of grass and broadleaf herbicides, at two rates were used. Herbicides reduced weed biomass compared with the weedy check. In both years, maximum reduction in weed biomass was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg ai/ha and desmedipham plus phenmedipham plus propaquizafop at 0.46 + 0.46 + 0.1 kg ai/ha. Efficacy of grass herbicides was reduced when they were combined with pyrazon. Highest crop injury in both years was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg/ ha. Highest and lowest root yields in both years were produced in weed-free and weedy check plots, respectively. All herbicide treatments produced lower sugar beet yields than the hand-weeded check. Of the herbicide treatments evaluated, the highest sugar beet yields were with desmedipham plus phenmedipham plus propaquizafop at 0.46 + 0.46 + 0.1 kg/ha in 2001 and with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg/ha in 2000. Sucrose content and other sugar beet brei characteristics were not affected by the herbicide treatments.
Relative Tolerance of Four Cool-Season Turfgrass Species to Sulfosulfuron
Authors: Lycan Darren W. , Hart Stephen E.
Published: July 2006

Field experiments were conducted at Adelphia, NJ, in 2001 and 2002 to evaluate the response of Kentucky bluegrass, perennial ryegrass, tall fescue, and Chewings fine fescue to sulfosulfuron. Single applications of sulfosulfuron at 6 to 67 g ai/ha were applied to mature swards of each species. Visual chlorosis ratings were taken and clippings were collected 4 wk after treatment (WAT), and turf injury was rated 8 WAT. Chlorosis on all species increased with increasing sulfosulfuron rate. In 2001, Kentucky bluegrass, perennial ryegrass, tall fescue, and fine fescue chlorosis reached 33, 43, 65, and 61% at 4 WAT, respectively, whereas in 2002, chlorosis only reached 13, 26, 46, and 26%, respectively. Clipping weights of all species decreased as application rate increased. Reductions in Kentucky bluegrass and perennial ryegrass clipping weights were less severe than those in tall and fine fescue. By 8 WAT, Kentucky bluegrass, perennial ryegrass, and fine fescue had nearly complete recovery from any initial visual injury symptoms. However, tall fescue injury was still evident 8 WAT in both years. Initial injury of Kentucky bluegrass, perennial ryegrass, and Chewings fine fescue was in the form of discoloration and stunting. Significant stand thinning was only evident in the tall fescue studies. These studies suggest that Kentucky bluegrass and perennial ryegrass may be more tolerant than tall fescue to applications of sulfosulfuron and fine fescue is intermediately tolerant to sulfosulfuron.
Influence of Early-Season Yield Loss Predictions from WeedSOFT®and Soybean Row Spacing on Weed Seed Production from a Mixed-Weed Community
Authors: Schmidt Andrew A. , Johnson William G.
Published: July 2006

Seed production from weeds that are missed by herbicide application can affect future weed populations and management decisions. It may be possible to expand the utility of computerized weed management decision aids to include an estimate of weed seed production resulting from selected treatments based on crop yield potential. Field studies were conducted in soybean near Columbia, MO, to determine whether weed control recommendations based on crop yield potential from a computerized weed management decision aid influence weed seed production in two soybean row spacings. At approximately 28 d after planting, weed densities and heights were entered into WeedSOFT®to generate a list of treatments ranked by predicted crop yields. Treatments included: (1) highest predicted crop yield in a glyphosate-resistant system, (2) highest predicted crop yield in a nonglyphosate-resistant system, (3) a 10% yield reduction, (4) a 20% yield reduction, and (5) an untreated control. These treatments were applied to soybean grown in 38- and 76-cm rows. Treatments that provided 90% or higher control of an individual species at 22 d after treatment usually produced less seed than untreated checks. Weed seed production based on early-season herbicide efficacy showed a linear relationship and was relatively predictable (r2≥ 0.52) for the predominant weed species. For less dominant weed species, weed seed production was not strongly correlated (r2≤ 0.27) to early-season herbicide efficacy but apparently influenced by control of other weed species. Narrow row spacing reduced giant foxtail biomass both years but did not reduce common ragweed and ivyleaf morningglory biomass. Narrow rows did not decrease giant foxtail, common ragweed, and ivyleaf morningglory seed production.
Risk-Efficiency Criteria for Evaluating Economics of Herbicide-Based Weed Management Systems in Corn
Authors: Hoverstad Thomas R. , Gunsolus Jeffrey L. , Johnson Gregg A. , King Robert P.
Published: July 2006

Evaluation of economic outcome associated with a given weed management system is an important component in the decision-making process within crop production systems. The objective of this research was to investigate how risk-efficiency criteria could be used to improve herbicide-based weed management decision making, assuming different risk preferences among growers. Data were obtained from existing weed management trials in corn conducted at the University of Minnesota Southern Research and Outreach Center at Waseca. Weed control treatments represented a range of practices including one-pass soil-applied, one-pass postemergence, and sequential combinations of soil and postemergence herbicide application systems. Analysis of risk efficiency across 23 herbicide-based weed control treatments was determined with the mean variance and stochastic dominance techniques. We show how these techniques can result in different outcomes for the decision maker, depending on risk attitudes. For example, mean variance and stochastic dominance techniques are used to evaluate risk associated with one- vs. two-pass herbicide treatments with and without cultivation. Based on these analyses, it appears that a one-pass system is preferred by a risk-averse grower. However, we argue that this may not be the best option considering potential changes in weed emergence patterns, application timing concerns, etc. The techniques for economic analysis of weed control data outlined in this article will help growers match herbicide-based weed management systems to their own production philosophies based on economic risk.
Green Peanut Tolerance to Preemergence and Postemergence Herbicides
Authors: Teuton Travis C. , Main Christopher L. , MacDonald Gregory E. , Ducar Joyce Tredaway , Brecke Barry J.
Published: July 2006

Field studies were conducted near Sparr, FL, in 2001 and 2002 to evaluate the response of ‘Valencia 102’ grown for the green peanut market (or boiling peanut) to preemergence (PRE) and postemergence (POST) applications of herbicides registered for dry peanut production (roasted market). Green peanut exhibited excellent tolerance to most PRE and POST treatments. There was minimal injury (8%) from flumioxazin applications when evaluated early season in both years, and peanut quickly recovered. Norflurazon caused chlorosis to peanut foliage (23%) in both years. Yield reduction was observed in 2001 for flumioxazin (15%), metolachlor (20%), and norflurazon (41%) compared with the untreated control. However, there were no yield reductions for any of the PRE treatments in 2002. Bentazon + paraquat early postemergence (EPOST) followed by (fb) 2,4-DB POST, bentazon + paraquat EPOST fb clethodim POST, and imazapic EPOST caused ≤5% injury and had no effect on yield in either year.
Effect of Herbicide Systems on Weed Shifts in Soybean and Cotton
Authors: Flint S. Gregory , Shaw David R. , Kelley Franklin S. , Holloway James C.
Published: July 2006

Field studies were conducted from 1998 through 2000 to compare weed population shifts in soybean and cotton using a total glyphosate system, preemergence (PRE) herbicides followed by glyphosate, and a conventional herbicide program. In the first year of the soybean study, populations of hemp sesbania were highest for treatments of PRE herbicides followed by either glyphosate or the conventional herbicide program because of better control from the total glyphosate system. Barnyardgrass populations in the first year of the study for the nontreated plots were 0 plants/m2but increased in the third year to 61 plants/m2. Flumetsulam plus metolachlor followed by glyphosate at the lower rates and the nontreated check were the only treatments in which there was an increase in barnyardgrass over the 3-yr study. Broadleaf signalgrass populations increased in the third year with 0.1 kg ai/ha flumetsulam plus 2.1 kg ai/ha metolachlor followed by 0.84 kg ae/ha glyphosate, primarily because of reduced competition from lower populations of other weeds such as hemp sesbania. Pitted morningglory populations for all treatments decreased in the third year because of good control of this species and the high level of interference from other weed species in the first 2 yr. Johnsongrass populations decreased in the third year with 0.4 kg ai/ha flumetsulam plus 1.1 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Johnsongrass populations decreased with timely glyphosate sequential applications, with 5 plants/m2in 1998 and 0 plants/m2in 2000. Yields increased from the first year to the second year, corresponding to reduced weed pressure, and yields varied from 710 to 1,420 kg/ha. Because of weed pressure, soybean yields were not different in any of the treatments, including the nontreated, although treatments changed the species present. In the cotton study, weed populations over the 3 yr decreased, with the most significant reductions from the treatments of fluometuron plus prometryn plus metolachlor followed by either pyrithiobac or glyphosate. Weeds that showed the most significant decline were barnyardgrass and hemp sesbania, whereas johnsongrass increased, with 27 plants/m2in treatments of 0.6 kg ai/ha fluometuron plus 0.3 kg ai/ha prometryn plus 0.7 kg ai/ha metolachlor followed by 0.84 kg/ha glyphosate. Lint cotton yields varied from 0 to 128 kg/ha. Because of the weed pressure, cotton yields were not different in any of the treatments, although treatments changed the species present. This research has shown that weed species can decrease over time with the continued use of any of these herbicide programs.
Broadleaf Weed Control and Potato Crop Safety with Postemergence Rimsulfuron, Metribuzin, and Adjuvant Combinations
Authors: Hutchinson Pamela J. S. , Eberlein Charlotte V. , Tonks Dennis J.
Published: July 2006

The effects of postemergence rimsulfuron, metribuzin, and adjuvant combinations on potato crop safety and weed control were evaluated in field studies conducted at the University of Idaho Aberdeen Research and Extension Center in 1999 and 2000. Rimsulfuron at 26 g ai/ha plus metribuzin at 0, 140, or 280 g ai/ha was combined with nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO) in a 3 by 3 factorial with two controls. Under cool, cloudy conditions in 1999, initial ‘Russet Burbank’ potato injury was greater when metribuzin was included in the tank mixture than when rimsulfuron was applied alone, regardless of adjuvant. Under warmer conditions in 2000, however, adding MSO or COC to the tank mixture caused more injury than adding NIS. Rimsulfuron did not provide acceptable season-long common lambsquarters control in 1999 (76%) or in 2000 (88%), regardless of adjuvant. Rimsulfuron combined with metribuzin at 140 or 280 g/ha provided ≥95% common lambsquarters control both years, regardless of adjuvant. Among adjuvants, using MSO (1999 and 2000) or COC (2000) in the spray mixture improved common lambsquarters control compared with using NIS. Tuber yield and quality were not reduced as a result of metribuzin rate or adjuvant treatments either year compared with the weed-free control.
‘Russet Burbank’ Potato Tolerance to Dimethenamid-p
Authors: Hutchinson Pamela J. S. , Ransom Corey V. , Tonks Dennis J. , Eberlein Charlotte V.
Published: July 2006

‘Russet Burbank’ potato tolerance to dimethenamid-p applied preemergence at 0.7, 1.4, or 2.9 kg ai/ha was assessed in field studies conducted at Aberdeen, ID and Ontario, OR. Although crop injury was evident approximately 2 wk after treatment, most injury had diminished by row closure 2- to 3-wk later. Initial injury did not translate to yield loss and U.S. No. 1 and total tuber yields in dimethenamid-p–treated plots were similar to yields in the untreated, weed-free control.
Detection of Leafy Spurge (Euphorbia esula) Using Multidate High-Resolution Satellite Imagery
Authors: Casady Grant M. , Hanley Rodney S. , Seelan Santhosh K.
Published: July 2006

Leafy spurge is a deep-rooted perennial weed that displaces native rangeland vegetation and replaces forage for cattle and other forages used by vertebrate herbivores. Strategic planning to control this weed requires monitoring its distribution and spread. Classical monitoring techniques, which often involve extensive ground survey efforts, can be aided by the synoptic nature of remotely sensed imagery. This research addresses the use of Space Imaging's 4-m multispectral Ikonos imagery for the survey and detection of leafy spurge infestations. Survey data were collected at a site in western North Dakota and used to produce supervised classifications of leafy surge infestations with Ikonos imagery. Multiple image dates per year were combined with each other to assess the added accuracy afforded by multitemporal imagery. Finally, individual patches of leafy spurge were analyzed to determine the minimum patch size and percent cover that were detectable with supervised classification of Ikonos imagery. Under some circumstances, the imagery was effective at detecting leafy spurge, but in areas with a higher forb component, the classification was not as effective. Multidate imagery provided increased accuracy, but improvements were not consistently significant. Leafy spurge infestations of <30% cover and 200 m2were not reliably detected.
Herbicide Timing and Rate Effects on Weed Management in Three Herbicide-Resistant Canola Systems
Authors: Harker K. Neil , Clayton George W. , O'Donovan John T. , Blackshaw Robert E. , Stevenson F. Craig
Published: July 2006

Herbicide-resistant canola dominates the canola market in Canada. A multiyear field experiment was conducted at three locations to investigate the effect of time of weed removal (two-, four-, or six-leaf canola) and herbicide rate (50 or 100% recommended) in three herbicide-resistant canola systems. Weeds were controlled in glufosinate-resistant canola (GLU) with glufosinate, in glyphosate-resistant canola (GLY) with glyphosate, and in imidazolinone-resistant canola (IMI) with a 50:50 mixture of imazamox and imazethapyr. Canola yields were similar among the three canola cultivar–herbicide systems. Yields were not influenced by 50 vs. 100% herbicide rates. Timing of weed removal had the greatest effect on canola yield, with weed removal at the four-leaf stage giving the highest yields in most cases. Percent dockage was often greater for GLU and IMI than for GLY. In comparison with the other treatments, dockage levels doubled for GLU after application at 50% herbicide rates. The consistency of monocot weed control was usually greater for GLY than for GLU or IMI systems. However, weed biomass data revealed no differences in dicot weed control consistency between IMI and GLY systems. Greater dockage and weed biomass variability after weed removal at the six-leaf stage or after low herbicide rates suggests higher weed seed production, which could constrain the adoption of integrated weed management practices in subsequent years.
Velvetleaf (Abutilon theophrasti) Interference and Seed Production in Corn Silage and Grain
Authors: Werner Edward L. , Curran William S. , Harper Jayson K. , Roth Gregory W. , Knievel Daniel P.
Published: July 2006

Studies were conducted during a 2-yr period measuring corn silage and grain yield and velvetleaf seed production in response to velvetleaf density. Velvetleaf densities of 0, 2, 5, 10, and 21 plants/m2were established in conventionally tilled corn. The percent corn yield reduction in response to velvetleaf density was similar for both years despite differences in total corn yield. Corn grain and silage yield responded differently to velvetleaf interference. Although both were adversely affected, silage yield reductions were twice that of grain at the low velvetleaf densities. A hyperbolic yield model predicted a maximum yield loss for corn silage and grain of 36 and 37% with incremental losses of 7 and 3%, respectively, as velvetleaf density increased. Velvetleaf seed production ranged from 2,256 to 4,844 seed/m2from the lowest to the highest density. This study demonstrates that corn silage yield is more sensitive than corn grain yield to velvetleaf interference, as well as how crop value plays an important role in determining economic thresholds. Finally, this research confirms the prolific nature of velvetleaf and shows that even at low densities, velvetleaf seed production could affect weed control decisions for many seasons to come.
Star-of-Bethlehem (Ornithogalum umbellatum) Control with Postemergence Herbicides in Dormant Bermudagrass (Cynodon dactylon) Turf
Authors: Main Christopher L. , Robinson Darren K. , Teuton Travis C. , Mueller Thomas C.
Published: July 2006

Field studies were conducted near Knoxville, TN, during late March and early April 2002 and 2003, respectively, for star-of-Bethlehem control in dormant bermudagrass turf that was established over 25 yr ago. Halosulfuron, imazaquin, metsulfuron, 2,4-D plus dicamba plus mecoprop, and triclopyr plus clopyralid controlled star-of-Bethlehem 35% at most 35 d after treatment (DAT). Bromoxynil alone or mixed with halosulfuron, imazaquin, or metsulfuron controlled star-of-Bethlehem at least 80% at 35 DAT. Imazaquin and imazaquin plus bromoxynil injured bermudagrass 51% 35 DAT. This injury was characterized by decreased bermudagrass postdormancy transition and was transient.
Weed Management in Imidazolinone-Resistant Corn with Imazapic
Authors: Ducar Joyce Tredaway , Wilcut John W. , Richburg John S.
Published: July 2006

Field studies were conducted in 1992 and 1993 to evaluate imazapic alone and in postemergence (POST) mixtures with atrazine or bentazon for weed control in imidazolinone-resistant corn treated with carbofuran. Nicosulfuron and nicosulfuron plus atrazine also were evaluated. Imazapic at 36 and 72 g ai/ha controlled large crabgrass 85 and 92%, respectively, which was equivalent to control obtained with nicosulfuron plus atrazine. Imazapic at the higher rate controlled large crabgrass better than nicosulfuron alone. Imazapic at 36 and 72 g/ha controlled Texas panicum 88 and 99%, respectively, and at the higher rate control was equivalent to that obtained with nicosulfuron alone or in mixture with atrazine. Imazapic plus bentazon POST controlled Texas panicum less than imazapic at the lower rate applied alone. Redroot pigweed was controlled 100% with all herbicide treatments. Imazapic at either rate alone or in tank mixture with bentazon or atrazine controlled prickly sida >99%, which was superior to control obtained with nicosulfuron or nicosulfuron plus atrazine. Smallflower, entireleaf, ivyleaf, pitted, and tall morningglories were controlled 96% or greater with all herbicide treatments except nicosulfuron alone. Sicklepod control was >88% with all imazapic treatments, whereas control from nicosulfuron alone was 72%. Corn yields were improved by the addition of POST herbicides with no differences among POST herbicide treatments.
Effect of Growth Stage on Trifloxysulfuron and Glyphosate Efficacy in Twelve Weed Species of Citrus Groves
Authors: Singh Samunder , Singh Megh
Published: July 2006

Efficacy of trifloxysulfuron with and without surfactant was evaluated against balsamapple, cat's claw vine, Florida beggarweed, hairy beggarticks, ivyleaf morningglory, johnsongrass, prickly sida, redroot pigweed, sicklepod, strangler vine, tall morningglory, and yellow nutsedge at 21, 42, and 63 g ai/ha applied at the four- or six-leaf stages and compared with glyphosate at 280, 560, and 840 g ae/ha. Delayed application from the four- to six-leaf stage significantly reduced trifloxysulfuron efficacy; reduction was less with glyphosate. Trifloxysulfuron plus 0.25% X-77 was more effective on the four-leaf stage than on the six-leaf stage plants of redroot pigweed, johnsongrass, hairy beggarticks, strangler vine, and prickly sida; effect was similar on yellow nutsedge, sicklepod, Florida beggarweed, balsamapple, ivyleaf morningglory, and tall morningglory. Trifloxysulfuron at 63 g/ha plus surfactant reduced the fresh weight of all test plants more than 80% compared with control, except prickly sida, strangler vine, and cat's claw vine. Glyphosate was less effective than trifloxysulfuron plus surfactant against tall morningglory, sicklepod, ivyleaf morningglory, and yellow nutsedge but was significantly better against balsamapple, prickly sida, and cat's claw vine. None of the herbicides provided satisfactory control of cat's claw vine, strangler vine, and prickly sida.
Yield and Physiological Response of Flue-Cured Tobacco to Simulated Glyphosate Drift
Authors: Burke Ian C. , Thomas Walter E. , Pline-Srnić Wendy A. , Fisher Loren R. , Smith W. David , Wilcut John W.
Published: July 2006

Field trials were conducted in 2001 at the Tobacco Research Station near Oxford, NC, and in 2002 at the Lower Coastal Plains Research Station near Kinston, NC, to determine tobacco yield, injury, and shikimic acid accumulation in response to simulated glyphosate drift. Glyphosate was applied to 12- to 13-cm-high tobacco ‘K326’ early postemergence at 0, 9, 18, 35, 70, 140, 280, 560, and 1,120 (1×) g ai/ha. Crop injury was rated 7 and 35 d after treatment (DAT) and shikimic acid accumulation in leaves at 7 DAT, tobacco yield, and leaf grade index (whole-plant index of harvest interval leaf value) were also assessed. Shikimic acid accumulation and injury symptoms increased similarly as glyphosate rate increased. Glyphosate rates of 140 g/ha (0.125 of recommended rate) or higher resulted in significant crop injury, reduced tobacco yield, and decreased leaf grade index. Shikimic acid accumulation at 7 DAT was inversely related to tobacco yield. Shikimic acid accumulation was found to be an effective diagnostic tool to determine glyphosate drift in tobacco; however, in-season data are needed to correlate shikimic acid accumulation with yield loss.
Determining Exposure to Auxin-Like Herbicides. II. Practical Application to Quantify Volatility
Authors: Sciumbato Audie S. , Chandler James M. , Senseman Scott A. , Bovey Rodney W. , Smith Ken L.
Published: July 2006

Volatility and drift are problems commonly associated with auxin-like herbicides. Field and greenhouse studies were conducted at Texas A & M University to develop a method of quantifying volatility and subsequent off-target movement of 2,4-D, dicamba, and triclopyr. Rate–response curves were established by applying reduced rates ranging from 4 × 10−1to 1 × 10−5times the normal use rates of the herbicides to cotton and soybean and recording injury for 14 d after treatment (DAT) using a rating scale designed to quantify auxin-like herbicide injury. Injury from herbicide volatility was then produced on additional cotton and soybean plants through exposure to vapors of the dimethylamine salt of 2,4-D, diglycolamine salt of dicamba, and butoxyethyl ester of triclopyr using air chambers inside a greenhouse and volatility plots in the field. Injury resulting from this exposure was evaluated for 14 d using the same injury-evaluation scale that was used to produce the rate–response curves. Volatility-injury data were then applied to the rate–response curves so that herbicide rates corresponding with observed injury could be calculated. Using this method, herbicide volatility rates estimated from greenhouse-cotton injury were determined to be 3.0 × 10−3, 1.0 × 10−3, and 4.9 × 10−2times the use rates of 2,4-D, dicamba, and triclopyr, respectively. Greenhouse-grown soybean developed injury consistent with 1.4 × 10−2, 1.0 × 10−3, and 2.5 × 10−2times the normal use rate of 2,4-D, dicamba, and triclopyr, respectively. Under field conditions, cotton developed injury symptoms that were consistent with 4.0 × 10−3, 2.0 × 10−3, and 1.25 × 10−1times the recommended use rates of 2,4-D, dicamba, and triclopyr, respectively. Field soybean displayed injury symptomology concordant with 1.6 × 10−1, 1.0 × 10−2, and 1.1 × 10−1times the normal use rates of 2,4-D, dicamba, and triclopyr, respectively. This procedure provided herbicide volatility rate estimates that were consistent with rates and injury from the rate–response injury curves. Additional research is needed to ascertain its usefulness in determining long-term effects of drift injury on crop variables such as yield.
Redvine (Brunnichia ovata) and Trumpetcreeper (Campsis radicans) Management in Glufosinate- and Glyphosate-Resistant Soybean
Authors: Reddy Krishna N. , Chachalis Demosthenis
Published: July 2006

Three field studies were conducted during 1998 to 2002 at Stoneville, MS, to examine the efficacy of glufosinate and glyphosate on redvine and trumpetcreeper control in glufosinate- and glyphosate-resistant soybean. Glyphosate at 2.52 kg ae/ha applied approximately 3 wk before planting soybean reduced trumpetcreeper density (45 to 52%) but not redvine compared with no glyphosate in both glufosinate- and glyphosate-resistant soybean. However, glyphosate applied preplant reduced biomass of both species in glufosinate-resistant soybean. Glyphosate early postemergence (EPOST) followed by (fb) late postemergence (LPOST) had no effect on redvine density but reduced trumpetcreeper density (70%) compared with the no-herbicide control. There were no differences in densities and biomass of redvine and trumpetcreeper and soybean yield among isopropylamine, diammonium, and aminomethanamide dihydrogen tetraoxosulfate salts of glyphosate. Overall, trumpetcreeper is more susceptible to glyphosate than redvine. Glufosinate EPOST with or without acifluorfen or glufosinate EPOST fb LPOST had no effect on densities of redvine and trumpetcreeper but reduced biomass 45 to 76% and 35 to 58%, respectively, compared with the nontreated control. These results show that glyphosate preplant and POST in-crop applications can reduce trumpetcreeper density but not redvine, and glufosinate POST applications can suppress growth of both species.
Influence of Spring Tillage and Glyphosate Treatment on Dandelion (Taraxacum officinale) Control in Glyphosate-Resistant Canola
Authors: Froese Nathan T. , Van Acker Rene C. , Friesen Lyle F.
Published: July 2006

Although dandelion has been recognized for some time as a common weed of perennial plant stands, recent weed surveys in western Canada indicate that dandelion has become more common in fields where annual spring crops are grown. Because little has been published on dandelion control in annual crops, a field study was conducted at two locations in southern Manitoba in 1999 and 2000 investigating the effect of spring tillage, glyphosate dosage, and application timing on dandelion control in a spring annual glyphosate-resistant canola crop. The experiments were situated in areas known to have natural infestations of dandelion. Final assessments of dandelion control were performed the spring following treatment, i.e., the next year, to provide a better indication of treatment efficacy on this perennial weed. Spring tillage alone did not significantly reduce dandelion density, as assessed the following spring, but did reduce dandelion shoot dry matter at three of the five site-years by up to 84%. Glyphosate was applied preplant, in-crop, and postharvest at dosages ranging from 450 g ae/ha in-crop to 2,700 g ae/ha postharvest. Glyphosate application after the canola crop had been harvested provided the greatest level of dandelion control, with a single postharvest application of 900 g ae/ha of glyphosate reducing dandelion density and shoot dry matter by 88 and 96%, respectively, the following spring. Applications of glyphosate either preplant or in-crop were not nearly as effective as the postharvest treatments in reducing dandelion density and shoot dry matter the following spring.
Imazethapyr is Safe and Effective for Imidazolinone-Tolerant Rice Grown on Coarse-Textured Soils
Authors: Ottis Brian V. , O'Barr John H. , McCauley Garry N. , Chandler James M.
Published: July 2006

A study was conducted in 2001 and 2002 in Texas to evaluate red rice control and crop response of imidazolinone-tolerant rice with imazethapyr on coarse-textured soils. Because imazethapyr was not registered for use on imidazolinone-tolerant rice on coarse-textured soils in Texas, crop response was evaluated to determine whether imidazolinone-tolerant rice yields would be reduced with sequential applications of imazethapyr on soils having greater than 50% sand content. The treatment factors consisted of preemergence (PRE) applications of imazethapyr at 50, 70, or 87 g ai/ ha followed by (fb) preflood (PREFLD) applications of 35 or 50 g/ha. Imazethapyr at 70 g/ha PRE fb 70 g/ha PREFLD was added as a seventh treatment. PRE applications were activated by rainfall or surface irrigation after application, and PREFLD applications were sprayed 1 to 2 d before application of the permanent flood. In both years, 100% red rice control was achieved with all rate combinations. Early-season visual rice injury ranged from 5 to 21% and did not result in yield losses, indicating that imazethapyr is safe on coarse-textured soils.
Increasing and Decreasing pH to Enhance the Biological Activity of Nicosulfuron
Authors: Green Jerry M. , Hale Theresa
Published: July 2006

Increasing the pH of the spray water to solubilize the weak acid herbicide nicosulfuron and then decreasing pH below its pKaso that it converts into a neutral form enhances biological activity under some conditions. The water-dispersible granule formulation of nicosulfuron starts as dispersed particles. Adding 1% wt/wt K3PO4solubilizes nicosulfuron and increases its activity compared to its dispersion without base. The type of buffer and the surfactant HLB or hydrophilic lipophilic balance, a measure of the molecular balance of the hydrophilic and lipophilic groups, altered the activity of nicosulfuron. Adding 1% wt/wt K3PO4increases the pH, and the optimum HLB ranged from 13 to 17 on large crabgrass. Adding 1% wt/wt H3PO4reduces the pH and lowers the optimum HLB range from 10 to 14 on large crabgrass. Adding the acidic buffer converts the solubilized nicosulfuron into its neutral form and increases activity under some surfactant conditions. Thus, neutral nicosulfuron is more active with lipophilic surfactants, while ionic nicosulfuron is more active with hydrophilic surfactants. When tested on other species, low HLB surfactants are the most active at low pH. These results support the concept that the physicochemical properties of the herbicide, adjuvants, and weed species should be matched for optimum activity.
Broadleaf Herbicide Effects on Clethodim and Quizalofop-P Efficacy on Volunteer Wheat (Triticum aestivum)
Authors: Blackshaw Robert E. , Harker K. Neil , Clayton George W. , O'Donovan John T.
Published: July 2006

Field experiments were conducted at three locations in 2003 and 2004 to examine clethodim and quizalofop-P efficacy on spring wheat seedlings when applied alone or in tank mixtures with herbicides used to control broadleaf weeds. Clethodim at the recommended rate of 30 g/ha reduced spring wheat biomass by 63 to 98% and was only >90% in three of six site years. In contrast, quizalofop-P at the recommended rate of 36 g/ha reduced wheat biomass >90% in all cases. Clethodim or quizalofop-P could be tank mixed with 2,4-D ester, bromoxynil, or bromoxynil plus MCPA ester with little risk of reduced efficacy on wheat. However, 2,4-D amine was highly antagonistic to both herbicides. The commercial mixture of thifensulfuron plus tribenuron reduced clethodim, but not quizalofop-P, efficacy on wheat. Herbicide options exist for simultaneous control of volunteer glyphosate-resistant canola and glyphosate-resistant wheat if the latter technology were to be commercialized in the future.
Weed Management with Oxyfluorfen and Napropamide in Mulched Strawberry
Authors: Gilreath James P. , Santos Bielinski M.
Published: July 2006

Two trials were conducted to evaluate the effects of herbicide and mulch on weed management and strawberry yield. Napropamide at rates of 4.50, 6.75, or 9.00 kg ai/ha; oxyfluorfen at 0.57 kg ai/ha; and napropamide plus oxyfluorfen at 4.50 plus 0.57 kg/ha were applied pretransplant on pressed beds covered with either low-density polyethylene mulch or virtually impermeable film. There was no herbicide by mulch interaction. Mulch types had no influence on weed counts and fruit yield, whereas herbicides affected both variables. The napropamide plus oxyfluorfen treatment resulted in the highest fruit number and weight, increasing yield by 20% with respect to the nontreated control. This herbicide combination provided the best weed suppression.
Developing National Research Teams: A Case Study with the Jointed Goatgrass Research Program
Authors: Anderson Randy L. , Hanavan Darrell , Ogg Alex G.
Published: July 2006

Weed scientists are facing research problems, such as invasive weeds, that may require multidisciplinary approaches to solve. One example is jointed goatgrass, a winter annual grass invading winter wheat fields and not easily managed with conventional control tactics. A national research program was started in 1994 to develop jointed goatgrass management strategies. Involving more than 35 scientists with diverse scientific expertise, this national approach fostered cooperative research projects across 11 states. Research involved entomology, economics, plant breeding, plant physiology, genetics, and weed science, leading to successful management systems for jointed goatgrass. To help other scientists organize regional or national programs, we describe development and performance of the jointed goatgrass program as well as suggest ideas for possible improvement. Pivotal to the success of the program was a Steering Committee, whose role was to establish research priorities and coordinate research across the western United States.
A Screening of Weed Control Options During Juneberry (Amelanchier alnifolia) Establishment
Authors: Hatterman-Valenti Harlene M.
Published: July 2006

Few weed management options are available for juneberry, which has limited the potential for this new crop. Field trials were initiated at three locations in North Dakota to evaluate efficacy and crop safety associated with chemical and physical weed control treatments applied just before or immediately after transplanting. All treatments except norflurazon and trifluralin provided at least 85% control of redroot pigweed, common lambsquarters, common purslane, and yellow foxtail for the duration of the trial at Absaraka, ND, during 2001. Stinkgrass weed control 8 wk after treatment (WAT) dropped to unacceptable levels (<85%) with all treatments except azafenidin at 0.5 kg ai/ ha, norflurazon, and oxyfluorfen at 1.1 kg ai/ha at Dawson, ND, during 2001. However, juneberry injury 4 WAT by azafenidin at 0.5 kg/ha, flumioxazin at both locations, or azafenidin at 0.34 kg/ha and oxyfluorfen at 1.1 kg ai/ha at Absaraka, ND, was greater than observed for plants within the physical treatments. Juneberry injury generally decreased with time, yet remained >20% at 8 WAT for azafenidin and flumioxazin at Absaraka, ND, and for all treatments except the mulches at Dawson, ND. Plant injury 8 WAT at Absaraka in 2002 was 10% or less for all treatments and was lower compared with 2001. All physical treatments—azafenidin at 0.34 and 0.5 kg/ha, flumioxazin at 0.29 kg/ha, and oryzalin at 4.5 kg/ha—provided at least 85% control of all weed species at Carrington and Absaraka, ND, during 2002.
Response of ‘TifEagle’ Bermudagrass (Cynodon dactylon×C. transvaalensis) to Fenarimol and Trinexapac-Ethyl
Authors: McCullough Patrick E. , McCarty Lambert B. , Liu Haibo
Published: July 2006

Fall applications of fenarimol on hybrid Bermudagrass (Cynodon dactylon×C. transvaalensis) provide effective preemergencePoa annua(L.) control and suppressOphiosphaerellaspp. pathogens; however, concerns exist for turf injury and root growth restrictions. Two 60-d greenhouse studies were conducted to evaluate the effects of fenarimol at 0, 1.6, and 3.2 kg ai/ha per 30 d with and without trinexapac-ethyl (TE) at 0.017 kg ai ha/15 d on ‘TifEagle’ Bermudagrass. Turf color was enhanced by TE 14 d after initial treatment (DAIT) and was continually superior throughout the experiment. Fenarimol at 3.2 kg/ha per 30 d decreased turf color 14 DAIT, but was similar to nontreated turf on all other observation dates. Increased fenarimol rates applied twice caused approximately 10% injury at 42, 49, and 56 d after treatment; however, injury was acceptable after initial and repeat applications. TE reduced clipping yield an average 39% from six sampling dates. Initial fenarimol applications (without TE) reduced clippings by 37% 20 DAIT and repeated applications reduced clippings 40, 50, and 60 DAIT. Increased fenarimol rate linearly decreased root mass for turf treated with and without TE; however, Bermudagrass receiving TE averaged 23% enhanced root mass 60 DAIT over all fenarimol rates. Bermudagrass receiving fenarimol at 0, 1.6, and 3.2 kg/ ha per 30 d with TE averaged 27, 24, and 16% higher root mass, respectively, compared to turf receiving fenarimol without TE. Treatments had no influence on root length. Results indicate that two consecutive fenarimol applications at 1.6 and 3.2 kg/ha per 30 d may cause minor injury to TifEagle Bermudagrass and restrict root growth. Repeated TE applications, however, could decrease injury from fenarimol and enhance rooting relative to fenarimol applied exclusively.
Survey of Soybean Weeds in Mississippi
Authors: Rankins Alfred , Byrd John D. , Mask Donald B. , Barnett Jimmy W. , Gerard Patrick D.
Published: July 2006

A survey was conducted in 2000 across 38 counties in Mississippi on 192 randomly selected soybean fields to assess the most common occurring weeds. Statewide, prickly sida, which was present in 40% of the fields sampled, was the most common. Pitted and entireleaf morningglory were present in 34 and 29% of the soybean fields, respectively. Broadleaf signalgrass and barnyardgrass were the most common annual grasses, and yellow nutsedge was the most common sedge observed. Trumpetcreeper and redvine were the most common perennial vines. In the Mississippi Delta region of Mississippi, prickly sida was present in 45% of the fields sampled. The trend of occurrence of other species in the Delta mirrored statewide results. In eastern Mississippi, prickly sida and broadleaf signalgrass were found in 43% of soybean fields. Sicklepod, common cocklebur, and balloonvine were more prevalent in eastern Mississippi, when compared with the Mississippi Delta. Since 1982, there has been a sevenfold decline in the occurrence of common cocklebur and a fourfold decline in the occurrence of johnsongrass in Mississippi soybean. Also, the occurrences of redroot pigweed, common ragweed, and fall panicum have declined. Conversely, the occurrences of yellow nutsedge and broadleaf signalgrass have increased. The occurrences of barnyardgrass, prickly sida, redvine and trumpetcreeper have been relatively static over the past two decades.
Increased Glyphosate Tolerance in ‘Aurora Gold’ Hard Fescue (Festuca longifolia)
Authors: Hart Stephen E. , Derr Jeffrey F. , Lycan Darren W. , Rose-Fricker Crystal , Meyer William A.
Published: July 2006

Studies were conducted in New Jersey and Virginia to evaluate the response of ‘Aurora Gold’ hard fescue, which had undergone five cycles of phenotypic recurrent selection for increased glyphosate tolerance, to direct applications of glyphosate. ‘Discovery’ hard fescue, which had not undergone recurrent selection, was also included in the study. Glyphosate treatments were initiated in early/mid-May and applied once, twice, or three times at 4- to 5-wk intervals at rates ranging from 0.1 to 1.6 kg ae/ha. Aurora Gold was more tolerant to glyphosate than Discovery in all experiments, indicating that recurrent selection was successful in increasing glyphosate tolerance in hard fescue. Single applications of glyphosate at rates ranging from 0.6 to 0.8 kg/ha could be applied to Aurora Gold with minimal injury or stand thinning (<20%), whereas multiple applications of glyphosate could be applied at rates ranging from 0.4 to 0.6 kg/ha. The use of Aurora Gold in areas planted to hard fescue, such as golf course roughs, vineyards, orchards, and landscapes, would allow the integration of direct glyphosate applications into an overall weed management program providing potential economic and environmental benefits.
Experimental Substrate Affects Rate of Seed Removal in Assays of Invertebrate Seed Predation
Authors: Gallandt Eric R.
Published: July 2006

Postdispersal seed predation by ground beetles may be an important form of biological weed control. Field experiments conducted in 2002 and 2003 determined invertebrate seed predators' ability to detect and remove seeds from different experimental substrates. Predation of wild mustard and common lambsquarters was greater when seeds were presented on sand compared with the two types of synthetic finishing pads; however, predation of velvetleaf, redroot pigweed, and hairy galinsoga was unaffected by substrate. Predation rates were not consistent across all experimental substrates. Estimates of invertebrate predation of common lambsquarters, yellow foxtail, and velvetleaf were greater for seeds offered on sand or synthetic pads than for seeds offered on soil or double-sided tape covered with soil. Although each substrate would be useful to estimate treatment effects on relative predation rates, the weed species by substrate interaction should be considered when comparing predation rates across experiments or when the absolute rate predation is of critical importance.
Tolerance of Processing Tomato to Thifensulfuron-Methyl
Authors: Soltani Nader , Robinson Darren E. , Hamill Allan S. , Bowley Stephen , Sikkema Peter H.
Published: July 2006

Limited information exists on the tolerance of processing tomato to postemergence (POST) application of thifensulfuron-methyl. The tolerance of 13 processing tomato varieties, ‘CC337’, ‘H9144’, ‘H9314’, ‘H9478’, ‘H9492’, ‘H9553’, ‘H9909’, ‘N1069’, ‘N1082’, ‘N1480E’, ‘N1480L’, ‘N1522’, and ‘PETO696’, to POST applications of thifensulfuron-methyl at the maximum use rate (6 g ai/ha) and twice the maximum use rate (12 g/ha) for soybean was evaluated at two Ontario locations in 2001 and 2002. At 7 days after treatment (DAT), thifensulfuron applied POST caused 0.2 to 1% visible injury to CC337, H9144, N1082, N1522, and PETO696 at the high rate. H9553, H9909, N1069, and N1480E were the most sensitive to POST thifensulfuron-methyl, with visible injury ranging from 1 to 6% at the high rate. There was no visible injury to H9314, H9478, H9492, or N1480L at either application rate of thifensulfuron-methyl. By 28 DAT, no visible injury was noted to any variety, except for H9909, N1069, and N1480L, which showed minimal (<2%) visible injury. There were no adverse effects on shoot dry weight and marketable yield for any variety at either rate. Although thifensulfuron-methyl applied POST caused minimal and transient injury to the varieties tested, more tolerance trials with other fresh and processing tomato varieties are required to confirm these initial results.
Preemergence Weed Control in Direct-Seeded Watermelon
Authors: Brandenberger Lynn P. , Shrefler James W. , Webber Charles L. , Talbert Ronald E. , Payton Mark E. , Wells Lynda K. , McClelland Marilyn
Published: July 2006

Studies were conducted at eight sites during a 3-yr period in Oklahoma and Arkansas to determine the effectiveness and safety of preemergence applications of halosulfuron both alone and in tank mixtures with bensulide, clomazone, ethalfluralin, and naptalam. Ethalfluralin, naptalam plus bensulide, and sulfentrazone also were applied alone. Although halosulfuron caused up to 20% seedling stunting, watermelon plants recovered by 5 to 7 wk after planting, and yield was similar to that of hand-weeded plots. Halosulfuron treatments controlled hophornbeam copperleaf, Palmer amaranth, carpetweed, and cutleaf groundcherry 80 to 100%. Control of goosegrass was at least 97% with clomazone plus ethalfluralin plus halosulfuron. Injury to watermelon treated with sulfentrazone ranged from 76 to 98% at 2 to 4 wk after treatment. This was reflected by yields that were lower than any other herbicide treatment in the studies.