Relating initial paraquat injury to final efficacy in selected weed species influenced by environmental conditions

Abstract Weed control of paraquat can be erratic and may be attributable to differing species sensitivity and/or environmental factors for which minor guidance is available on commercial labels. Therefore, the objectives of this research were to quantify selectivity of paraquat across select weed species and the influence of environmental factors. Experiments were performed under controlled conditions in the greenhouse and growth chamber. Compared with purple deadnettle (dose necessary to reduce shoot biomass by 50% = 39 g ai ha−1), waterhemp, Palmer amaranth, giant ragweed, and horseweed were 4.9, 3.3, 1.9, and 1.3 times more sensitive to paraquat, respectively. The injury progression rate over 3 d after treatment (DAT) was a more accurate predictor of final efficacy at 14 DAT than the lag phase until symptoms first appeared. For example, at the 17.5 g ha−1 dose, the injury rate of waterhemp and Palmer amaranth was, on average, 3.6 times greater than that of horseweed and purple deadnettle. The influence of various environmental factors on paraquat efficacy was weed specific. Applications made at sunrise improved control of purple deadnettle over applications at solar noon or sunset. Lower light intensities (200 or 600 μmol m−2 s−1) surrounding the time of application improved control of waterhemp and horseweed more than 1,000 μmol m−2 s−1. Day/night temperatures of 27/16 C improved horseweed and purple deadnettle control compared with day/night temperatures of 18/13 C. Though control was positively associated with injury rates in the application time of day and temperature experiments, a negative relationship was observed for waterhemp in the light-intensity experiment. Thus, although there are conditions that enhance paraquat efficacy, the specific target species must also be considered. These results advocate paraquat dose recommendations, currently based on weed height, be expanded to address sensitivity differences among weeds. Moreover, these findings contrast with paraquat labels stating temperatures of 13 C or lower do not reduce paraquat efficacy.

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Influence of Two Herbicides on Soybean Cyst Nematode (Heterodera glycines) Reproduction on Henbit (Lamium amplexicaule) Roots

Weed Technology ◽

10.1614/wt-d-12-00094.1 ◽

2013 ◽

Vol 27 (1) ◽

pp. 41-46 ◽

Cited By ~ 7

Author(s):

Rodrigo Werle ◽

Mark L. Bernards ◽

Loren J. Giesler ◽

John L. Lindquist

Keyword(s):

Soybean Cyst Nematode ◽

Block Design ◽

Dry Weight ◽

The United States ◽

Cyst Nematode ◽

Shoot Biomass ◽

Herbicide Application ◽

Weed Species ◽

Time Of Application ◽

Greenhouse Study

Soybean cyst nematode (SCN) is the most yield-limiting pathogen of soybean in the United States. Henbit is a prevalent winter annual weed species in no-till fields and is reported to be an alternative host of SCN. A greenhouse study was conducted to evaluate how the development of SCN on henbit roots was affected by herbicide mode of action and time of herbicide application. Henbit plants were grown in watertight pots placed in a water bath bench that kept soil temperature constant (27 ± 1 C) during the study. Ten d after transplanting, pots were inoculated with approximately 1,000 SCN eggs. At 7, 14, or 21 d after inoculation (DAI), henbit plants were sprayed with recommended dose of either glyphosate (870 g ae ha−1) or 2,4-D (1,070 g ae ha−1). The experiment was arranged in a randomized complete block design with five replications per treatment, and two experimental runs separated in time. At 28 DAI, the total number of SCN cysts and eggs, and plant shoot and root dry weight per pot were determined. Henbit root and shoot biomass increased as the time of herbicide application was delayed. Glyphosate reduced root biomass more than 2,4-D, but no differences in shoot biomass were detected. The number of SCN cysts per henbit plant and eggs per cyst increased as the herbicide application was delayed from 7 to 21 DAI. Glyphosate reduced the number of cysts found on henbit roots more than 2,4-D, especially at earlier application times. On plants treated with glyphosate, SCN-females produced only half the number of eggs of SCN-females on henbit plants treated with 2,4-D, regardless of time of application. These results indicate that early control of henbit plants, especially with glyphosate, can reduce SCN reproduction potential in SCN infested fields.

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Time of Application Influences Translocation of Auxinic Herbicides in Palmer Amaranth (Amaranthus palmeri)

Weed Science ◽

10.1017/wsc.2017.36 ◽

2017 ◽

Vol 66 (1) ◽

pp. 4-14 ◽

Cited By ~ 4

Author(s):

Christopher R. Johnston ◽

Peter M. Eure ◽

Timothy L. Grey ◽

A. Stanley Culpepper ◽

William K. Vencill

Keyword(s):

Mechanism Of Action ◽

Resistance Management ◽

Time Of Day ◽

Palmer Amaranth ◽

Effective Control ◽

Application Time ◽

Time Of Application ◽

Group 4 ◽

Treated Leaf ◽

Root Treatment

The efficacy of WSSA Group 4 herbicides has been reported to vary with dependence on the time of day the application is made, which may affect the value of this mechanism of action as a control option and resistance management tool for Palmer amaranth. The objectives of this research were to evaluate the effect of time of day for application on 2,4-D and dicamba translocation and whether or not altering translocation affected any existing variation in phytotoxicity seen across application time of day. Maximum translocation (Tmax) of [14C]2,4-D and [14C]dicamba out of the treated leaf was significantly increased 52% and 29% to 34% in one of two repeated experiments for each herbicide, respectively, with application at 7:00 AM compared with applications at 2:00 PM and/or 12:00 AM. Applications at 7:00 AM increased [14C]2,4-D distribution to roots and increased [14C]dicamba distribution above the treated leaf compared with other application timings. In phytotoxicity experiments, dicamba application at 8 h after exposure to darkness (HAED) resulted in significantly lower dry root biomass than dicamba application at 8 h after exposure to light (HAEL). Contrasts indicated that injury resulting from dicamba application at 8 HAEL, corresponding to midday, was significantly reduced with a root treatment of 5-[N-(3,4-dimethoxyphenylethyl)methylamino]-2-(3,4-dimethoxyphenyl)-2-isopropylvaleronitrile hydrochloride (verapamil) compared with injury observed with dicamba application and a root treatment of verapamil at 8 HAED, which corresponded to dawn. Overall, time of application appears to potentially influence translocation of 2,4-D and dicamba. Furthermore, inhibition of translocation appears to somewhat influence variation in phytotoxicity across times of application. Therefore, translocation may be involved in the varying efficacy of WSSA Group 4 herbicides due to application time of day, which has implications for the use of this mechanism of action for effective control and resistance management of Palmer amaranth.

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The Effect of Time of Day on the Activity of Postemergence Soybean Herbicides

Weed Technology ◽

10.1614/wt-d-13-00035.1 ◽

2013 ◽

Vol 27 (4) ◽

pp. 690-695 ◽

Cited By ~ 15

Author(s):

Gregory J. Stopps ◽

Robert E. Nurse ◽

Peter H. Sikkema

Keyword(s):

Weed Control ◽

Yield Loss ◽

Early Morning ◽

Field Trials ◽

Time Of Day ◽

Weed Species ◽

Time Of Application ◽

Late Evening ◽

Chlorimuron Ethyl ◽

Herbicide Activity

The effect of time of day (TOD) on the activity of six common POST herbicides was investigated in field trials from 2007 to 2009 at two locations in southwestern Ontario. Percentage weed control was assessed following application of bentazon, chlorimuron-ethyl, fomesafen, glyphosate, imazethapyr, or quizalofop-p-ethyl applied at 3-h intervals from 6:00 A.M. to midnight, when weeds averaged 15 cm tall. The effect of time of day varied with weed species, but weed control was generally reduced when herbicides were applied at 6:00 A.M., 9:00 P.M., and midnight. Herbicide activity on velvetleaf was most frequently reduced, especially for chlorimuron-ethyl, glyphosate, and imazethapyr. Control of common ragweed with glyphosate and imazethapyr was also affected by the timing of application, and pigweed species only showed an effect with glyphosate. Variation in temperature, relative humidity, and dew presence/absence at different times of the day, as well as morphological/physiological characteristics such as weed size at time of application and diurnal leaf movement in response to light intensity, may account for the variation in weed control at different times of the day. Significant soybean yield loss was not observed in this study, but may occur if herbicide efficacy is severely reduced by application at inappropriate times of day. These results provide valuable information for growers, and suggest that POST herbicides are most effective when applied midday, rather than in the early morning or late evening.

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Glyphosate Resistance in Perennial Ryegrass (Lolium perenneL.) is Associated with a Fitness Penalty

Weed Science ◽

10.1614/ws-d-15-00065.1 ◽

2016 ◽

Vol 64 (1) ◽

pp. 71-79 ◽

Cited By ~ 27

Author(s):

Marcos Yanniccari ◽

Martín Vila-Aiub ◽

Carolina Istilart ◽

Horacio Acciaresi ◽

Ana M. Castro

Keyword(s):

Perennial Ryegrass ◽

Water Availability ◽

Field Experiments ◽

Seed Mass ◽

Selection Effect ◽

Glyphosate Resistance ◽

Shoot Biomass ◽

Seed Number ◽

Fitness Costs ◽

Weed Species

The net selection effect of herbicides on herbicide-resistance traits in weeds is conditioned by the fitness benefits and costs associated with resistance alleles. Fitness costs play an important evolutionary role preventing the fixation of adaptive alleles and contributing to the maintenance of genetic polymorphisms within populations. Glyphosate is widely used in world agriculture, which has led to the evolution of widespread glyphosate resistance in many weed species. The fitness of glyphosate-resistant and -susceptible perennial ryegrass plants selected from within a single population were studied in two field experiments conducted during 2011 and 2012 under different soil water availability. Glyphosate-resistant plants showed a reduction in height of 12 and 16%, leaf blade area of 16 and 33%, shoot biomass of 45 and 55%, seed number of 33 and 53%, and total seed mass of 16 and 5% compared to glyphosate-susceptible plants in 2011 and 2012, respectively. The reduction in seed number per plant resulted in a 40% fitness cost associated with the glyphosate-resistance trait in perennial ryegrass. Fitness costs of glyphosate-resistant plants were expressed under both conditions of water availability. These results could be useful for designing management strategies and exploiting the reduced glyphosate-resistant perennial ryegrass fitness in the absence of glyphosate selection.

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EXAMINATION OF THE WEED FLORA OF RUDER HABITATS AND THE POSSIBILITY OF SUPPRESSION WITH HERBICIDES

Applied Researches in Technics Technologies and Education ◽

10.15547/artte.2018.04.007 ◽

2018 ◽

Vol 6 (4) ◽

pp. 329-332

Author(s):

Milić Vojinović ◽

Jelica Živić ◽

Sanja Perić ◽

Miroljub Aksić

Keyword(s):

Chenopodium Album ◽

Working Environment ◽

Xanthium Strumarium ◽

Weed Species ◽

Construction Sites ◽

Convolvulus Arvensis ◽

Human Settlements ◽

Time Of Application ◽

Vegetation Complex ◽

Selection Of

Ruderal flora, as well as the vegetation that flora forms, represent an extremely dynamic floristic-vegetation complex and arean integral part of the most immediate living and working environment of human. It is formed and developed mainly in human settlements, as well as in the other anthropogenic environments that are occasionally or permanently under direct or indirect influence of various forms of human activity. Ruderal vegetation is found not only directly around the settlements, but also around all urban and accompanying facilities: along roads, paths and fences around houses, yards, walls and roofs, in avenues, on ruins, construction sites, landfills, along railway tracks, road and defense embankments, on wet and nitrified banks of rivers, near human settlements, in abandoned lawns, on the street walks with sandy areas, cemeteries, in degraded pastures, forests, etc. This essay presents the distribution and representation of economically harmful, invasive and quarantine weed species (Abutilon theophrasti, Agropyrumrepens, Amaranthusretroflexus, Calystegiasepium, Cirsiumarvense, Chenopodium album, Chenopodiumhybridum, Convolvulus arvensis, Cynodondactylon, Daturastramonium, Sonchusarvensis, Sorghum halepense, Xanthium strumarium…) at ten sites in the Nisava district. The assessment of species representation was done in two shootings (May and August) according to scale 1-4. The proper selection of herbicides depends, in a large extent, on the presence of dominant weed species and on the time of application.

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Darwin’s naturalization hypothesis does not explain the spread of nonnative weed species naturalized in México

PeerJ ◽

10.7717/peerj.5444 ◽

2018 ◽

Vol 6 ◽

pp. e5444

Author(s):

Judith Sánchez-Blanco ◽

Ernesto V. Vega-Peña ◽

Francisco J. Espinosa-García

Keyword(s):

Residence Time ◽

Lag Phase ◽

Herbarium Specimens ◽

Weed Species ◽

Species Groups ◽

Biological Attributes ◽

Darwin's Naturalization Hypothesis ◽

Stochastic Events ◽

Close Relatives ◽

Darwin’S Naturalization Hypothesis

BackgroundDespite numerous tests of Darwin’s naturalization hypothesis (DNH) evidence for its support or rejection is still contradictory. We tested a DNH derived prediction stating that nonnative species (NNS) without native congeneric relatives (NCR) will spread to a greater number of localities than species with close relatives in the new range. This test controlled the effect of residence time (Rt) on the spread of NNS and used naturalized species beyond their lag phase to avoid the effect of stochastic events in the establishment and the lag phases that could obscure the NCR effects on NNS.MethodsWe compared the number of localities (spread) occupied by NNS with and without NCR using 13,977 herbarium records for 305 NNS of weeds. We regressed the number of localities occupied by NNSversus Rtto determine the effect of time on the spread of NNS. Then, we selected the species withRtgreater than the expected span of the lag phase, whose residuals were above and below the regression confidence limits; these NNS were classified as widespread (those occupying more localities than expected byRt) and limited-spread (those occupying fewer localities than expected). These sets were again subclassified into two groups: NNS with and without NCR at the genus level. The number of NNS with and without NCR was compared usingχ2tests and Spearman correlations between the residuals and the number of relatives. Then, we grouped the NNS using 34 biological attributes and five usages to identify the groups’ possible associations with spread and to test DNH. To identify species groups, we performed a nonmetric multidimensional scaling (NMDS) analysis and evaluated the influences of the number of relatives, localities, herbarium specimens,Rt, and residuals of regression. The Spearman correlation and the Mann–WhitneyUtest were used to determine if the DNH prediction was met. Additionally, we used the clustering objects on subsets of attributes (COSA) method to identify possible syndromes (sets of biological attributes and usages) associated to four groups of NNS useful to test DNH (those with and without NCR and those in more and fewer localities than expected byRt).ResultsResidence time explained 33% of the variation in localities occupied by nonnative trees and shrubs and 46% of the variation for herbs and subshrubs. The residuals of the regression for NNS were not associated with the number or presence of NCR. In each of the NMDS groups, the number of localities occupied by NNS with and without NCR did not significantly differ. The COSA analysis detected that only NNS with NCR in more and fewer localities than expected share biological attributes and usages, but they differ in their relative importance.DiscussionOur results suggest that DNH does not explain the spread of naturalized species in a highly heterogeneous country. Thus, the presence of NCR is not a useful characteristic in risk analyses for naturalized NNS.

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Weed Management with Glyphosate- and Glufosinate-Based Systems in PHY 485 WRF Cotton

Weed Technology ◽

10.1614/wt-d-10-00008.1 ◽

2011 ◽

Vol 25 (2) ◽

pp. 183-191 ◽

Cited By ~ 31

Author(s):

Jared R. Whitaker ◽

Alan C. York ◽

David L. Jordan ◽

A. Stanley Culpepper

Keyword(s):

Weed Control ◽

Weed Management ◽

Fiber Quality ◽

Palmer Amaranth ◽

Weed Species ◽

Crop Tolerance ◽

The North ◽

Annual Grasses ◽

Resistance Trait ◽

Cotton Belt

Glyphosate-resistant (GR) Palmer amaranth has become a serious pest in parts of the Cotton Belt. Some GR cotton cultivars also contain the WideStrike™ insect resistance trait, which confers tolerance to glufosinate. Use of glufosinate-based management systems in such cultivars could be an option for managing GR Palmer amaranth. The objective of this study was to evaluate crop tolerance and weed control with glyphosate-based and glufosinate-based systems in PHY 485 WRF cotton. The North Carolina field experiment compared glyphosate and glufosinate alone and in mixtures applied twice before four- to six-leaf cotton. Additional treatments included glyphosate and glufosinate mixed withS-metolachlor or pyrithiobac applied to one- to two-leaf cotton followed by glyphosate or glufosinate alone on four- to six-leaf cotton. All treatments received a residual lay-by application. Excellent weed control was observed from all treatments on most weed species. Glyphosate was more effective than glufosinate on glyphosate-susceptible (GS) Palmer amaranth and annual grasses, while glufosinate was more effective on GR Palmer amaranth. Annual grass and GS Palmer amaranth control by glyphosate plus glufosinate was often less than control by glyphosate alone but similar to or greater than control by glufosinate alone, while mixtures were more effective than either herbicide alone on GR Palmer amaranth. Glufosinate caused minor and transient injury to the crop, but no differences in cotton yield or fiber quality were noted. This research demonstrates glufosinate can be applied early in the season to PHY 485 WRF cotton without concern for significant adverse effects on the crop. Although glufosinate is often less effective than glyphosate on GS Palmer amaranth, GR Palmer amaranth can be controlled with well-timed applications of glufosinate. Use of glufosinate in cultivars with the WideStrike trait could fill a significant void in current weed management programs for GR Palmer amaranth in cotton.

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Effect of Ensiling and Rumen Digestion by Cattle on Weed Seed Viability

Weed Science ◽

10.1017/s0043174500057957 ◽

1991 ◽

Vol 39 (1) ◽

pp. 104-108 ◽

Cited By ~ 46

Author(s):

Robert E. Blackshaw ◽

Lyle M. Rode

Keyword(s):

Time Course ◽

Seed Viability ◽

Grass Species ◽

Lag Phase ◽

Rapid Decline ◽

Weed Species ◽

Embryo Viability ◽

Seed Survival ◽

Gradual Process ◽

Broadleaf Species

Studies were conducted to determine the effect of ensiling and/or rumen digestion by cattle on the germination and viability of several common weed species. Seed survival of grass species subjected to ensiling and/or rumen digestion tended to be less than that of broadleaf species. Downy brome, foxtail barley, and barnyardgrass were nonviable after either ensiling for 8 weeks or rumen digestion for 24 h. Some green foxtail (17%) and wild oats (0 to 88%) seeds survived digestion in the rumen but were killed by the ensiling process. Varying percentages of seeds of kochia, redroot pigweed, common lambsquarters, wild buckwheat, round-leaved mallow, and field pennycress remained viable after ensiling (3 to 30%), rumen digestion (15 to 98%), and ensiling plus rumen digestion (2 to 19%). A time course study of rumen digestion indicated that loss of seed viability often was not a gradual process. With some species, there was an initial lag phase while degradation of the protective seed coat likely occurred, followed by a rapid decline in embryo viability. The diet fed to livestock appeared to affect viability losses caused by rumen digestion. Estimates of seed survival with varying rates of passage through the rumen due to differing ratios of grain to forage in the diet are presented.

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Winter Wheat (Triticum aestivum) Growth Stage Effect on Paraquat Bioactivity

Weed Technology ◽

10.1017/s0890037x00028396 ◽

1991 ◽

Vol 5 (2) ◽

pp. 439-441

Author(s):

Randy L. Anderson ◽

David C. Nielsen

Keyword(s):

Triticum Aestivum ◽

Winter Wheat ◽

Growth Stage ◽

Time Of Day ◽

Growth Stages ◽

Leaf Stage ◽

Time Of Application ◽

Biomass Reduction

Paraquat was applied at 0.28 and 0.56 kg ai ha-1to winter wheat at five growth stages at 0800, 1300, and 1600 hr to determine whether growth stage or time of application influenced winter wheat response to paraquat. Paraquat bioactivity was affected by growth stage. Biomass reduction by paraquat was 84% when winter wheat was in the 1 to 3 leaf stage, but only 68% when application was delayed until tillering. Paraquat bioactivity continued to decrease at later growth stages. The time of day when paraquat was applied did not affect its bioactivity on winter wheat.

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Weed management with CGA-362622 in transgenic and nontransgenic cotton

Weed Science ◽

10.1614/p2002-014 ◽

2003 ◽

Vol 51 (6) ◽

pp. 1002-1009 ◽

Cited By ~ 19

Author(s):

Dunk Porterfield ◽

John W. Wilcut ◽

Jerry W. Wells ◽

Scott B. Clewis

Keyword(s):

North Carolina ◽

Weed Control ◽

Weed Management ◽

Field Studies ◽

Palmer Amaranth ◽

Management Systems ◽

Weed Species ◽

Crop Tolerance ◽

Prickly Sida ◽

Smooth Pigweed

Field studies conducted at three locations in North Carolina in 1998 and 1999 evaluated crop tolerance, weed control, and yield with CGA-362622 alone and in combination with various weed management systems in transgenic and nontransgenic cotton systems. The herbicide systems used bromoxynil, CGA-362622, glyphosate, and pyrithiobac applied alone early postemergence (EPOST) or mixtures of CGA-362622 plus bromoxynil, glyphosate, or pyrithiobac applied EPOST. Trifluralin preplant incorporated followed by (fb) fluometuron preemergence (PRE) alone or fb a late POST–directed (LAYBY) treatment of prometryn plus MSMA controlled all the weed species present less than 90%. Herbicide systems that included soil-applied and LAYBY herbicides plus glyphosate EPOST or mixtures of CGA-362622 EPOST plus bromoxynil, glyphosate, or pyrithiobac controlled broadleaf signalgrass, entireleaf morningglory, large crabgrass, Palmer amaranth, prickly sida, sicklepod, and smooth pigweed at least 90%. Only cotton treated with these herbicide systems yielded equivalent to the weed-free check for each cultivar. Bromoxynil systems did not control Palmer amaranth and sicklepod, pyrithiobac systems did not control sicklepod, and CGA-362622 systems did not control prickly sida.

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