Wild Oat Herbicide Research Articles

Case Report of Avena sterilis subsp. sterilis ACCase Herbicide Resistance in Southern Spain

Wild oats are worldwide grassy weeds that cause substantial yield losses, particularly in winter cereal crops. In addition, wild oat herbicide resistant cases have increased; indeed, up to 52 cases have been registered. Despite this, no wild oat herbicide resistant cases have been described in Spain, where farmers and technicians have reported poor herbicide efficacy in sterile oats (Avena sterilis subsp. sterilis L.). A dose-response experiment was conducted comparing the behavior of two populations of A. sterilis from southern Spain to a susceptible population. These populations were collected from two commercial farms where a low efficacy of chemical control had been described. Clodinafop-propargyl and Pinoxaden were tested as active ingredients in the dose-response experiment. Additionally, an alternative herbicide, which consisted of a mixture of Mesosulfuron-methyl and Propoxycarbazone-Na, was also tested at a field dose. The two populations of A. sterilis studied provided a resistant factor higher than 10 for Clodinafop-propargyl and higher than 4 for Pinoxaden. A total control was achieved for plants treated with Mesosulfuron-methyl and Propoxycarbazone-Na.

The profitability of diverse crop rotations and other cultural methods that reduce wild oat (Avena fatua)

With the increasing resistance of wild oat (Avena fatua L.) to herbicides, there is a need to evaluate the potential of alternative cropping systems based on integrated weed management principles. A 5-yr field study at eight sites across Canada was used to evaluate the profitability of alternative cropping systems that have the potential to control wild oat using cultural practices in conjunction with herbicides. Cultural practices included twice the recommended seeding rates, fall-seeded winter crops, barley (Hordeum vulgare L.) silage, fallow, and alfalfa (Medicago sativa L.). Seven of the 14 cropping systems in this study did not include wild oat herbicide for three consecutive years, controlling wild oat entirely by cultural practices. Cropping system profitability varied by location. For many locations, combinations of barley silage and fall-seeded winter crops without wild oat herbicide application were as profitable as a system of canola (Brassica napus L.) and wheat (Triticum aestivum L.) with wild oat herbicide applied every year. Unprofitable systems generally included those with fallow, alfalfa, and fall-seeded winter crops in regions with rates of high winter kill. Wild oat control can be achieved with diverse cropping systems that are as profitable as conventional annual cropping that relies on herbicide control of wild oat.

Diverse Rotations and Optimal Cultural Practices Control Wild Oat (Avena fatua)

In western Canada, more money is spent on wild oat herbicides than on any other weed species, and wild oat resistance to herbicides is the most widespread resistance issue. A direct-seeded field experiment was conducted from 2010 to 2014 at eight Canadian sites to determine crop life cycle, crop species, crop seeding rate, crop usage, and herbicide rate combination effects on wild oat management and canola yield. Combining 2× seeding rates of early-cut barley silage with 2× seeding rates of winter cereals and excluding wild oat herbicides for 3 of 5 yr (2011 to 2013) often led to similar wild oat density, aboveground wild oat biomass, wild oat seed density in the soil, and canola yield as a repeated canola–wheat rotation under a full wild oat herbicide rate regime. Wild oat was similarly well managed after 3 yr of perennial alfalfa without wild oat herbicides. Forgoing wild oat herbicides in only 2 of 5 yr from exclusively summer annual crop rotations resulted in higher wild oat density, biomass, and seed banks. Management systems that effectively combine diverse and optimal cultural practices against weeds, and limit herbicide use, reduce selection pressure for weed resistance to herbicides and prolong the utility of threatened herbicide tools.

Site-specific wild oat (Avena fatua L.) management

Beckie, H. J. and Shirriff, S. 2012. Site-specific wild oat ( Avena fatua L.) management. Can. J. Plant Sci. 92: 923–931. Variation in soil properties, such as soil moisture, across a hummocky landscape may influence wild oat emergence and growth. To evaluate wild oat emergence, growth, and management according to landscape position, a study was conducted from 2006 to 2010 in a hummocky field in the semiarid Moist Mixed Grassland ecoregion of Saskatchewan. The hypothesis tested was that wild oat emergence and growth would be greater in lower than upper slope positions under normal or dry early growing season conditions. Three herbicide treatments were imposed on the same plots each year of a 2-yr canola (Brassica napus L.) – wheat (Triticum aestivum L.) sequence: (1) nontreated (weedy) control; (2) herbicide application to upper and lower slope positions (i.e., full or blanket application); and (3) herbicide application to lower slope position only. Slope position affected crop and weed densities before in-crop herbicide application in years with dry spring growing conditions. Site-specific wild oat herbicide application in hummocky fields in semiarid regions may be justified based on results of wild oat control averaged across slope position. In year 2 of the crop sequence (wheat), overall (i.e., lower and upper slope) wild oat control based on density, biomass, and dockage (i.e., seed return) was similar between site-specific and full herbicide treatment in 2 of 3 yr. Because economic thresholds have not been widely adopted by growers in managing wild oat, site-specific treatment in years when conditions warrant may be an appropriate compromise between no application and blanket herbicide application.

The level of wild oat resistance to ACC-ase inhibitors in South-Eastern Poland

In the years 2003-2004 two experiments: laboratory and field, were carried out to detect the level of wild oat herbicide resistance. Weeds were collected from fields in south-eastern Poland, on the basis of survey conducted between farmers who have problems with wild oat herbicidal fighting. Two herbicides were tested: fenoxaprop- P-ethyl and diclofop methyl, both ACC-ase inhibitors. The laboratory test was established by modified Letouze et al. (1997) method. After 6-day growth on each herbicide water solution, the number of alive wild oat seedlings was assesed. In the field experiment plants in 3-5 leaf stage were sprayed with field dose of each herbicide. Two weeks after spraying the percentage of plants damage and in July the percentage of flowering plants were assesed. The wild oat plants that survive in laboratory test in ≥50% and plants that flowered in ≥50% in field conditions were recognized as resistant. On that basis wild oat resistace to fenoxaprop-P-ethyl and to diclofop methyl was stated on 17% and 28% fields from overall number of 18 fields, respectively.

Developing an Empirical Yield-Prediction Model Based on Wheat and Wild Oat (Avena fatua) Density, Nitrogen and Herbicide Rate, and Growing-Season Precipitation

To develop a more complete understanding of the ecological factors that regulate crop productivity, we tested the relative predictive power of yield models driven by five predictor variables: wheat and wild oat density, nitrogen and herbicide rate, and growing-season precipitation. Existing data sets were collected and used in a meta-analysis of the ability of at least two predictor variables to explain variations in wheat yield. Yield responses were asymptotic with increasing crop and weed density; however, asymptotic trends were lacking as herbicide and fertilizer levels were increased. Based on the independent field data, the three best-fitting models (in order) from the candidate set of models were a multiple regression equation that included all five predictor variables (R2= 0.71), a double-hyperbolic equation including three input predictor variables (R2= 0.63), and a nonlinear model including all five predictor variables (R2= 0.56). The double-hyperbolic, three-predictor model, which did not include herbicide and fertilizer influence on yield, performed slightly better than the five-variable nonlinear model including these predictors, illustrating the large amount of variation in wheat yield and the lack of concrete knowledge upon which farmers base their fertilizer and herbicide management decisions, especially when weed infestation causes competition for limited nitrogen and water. It was difficult to elucidate the ecological first principles in the noisy field data and to build effective models based on disjointed data sets, where none of the studies measured all five variables. To address this disparity, we conducted a five-variable full-factorial greenhouse experiment. Based on our five-variable greenhouse experiment, the best-fitting model was a new nonlinear equation including all five predictor variables and was shown to fit the greenhouse data better than four previously developed agronomic models with anR2of 0.66. Development of this mathematical model, through model selection and parameterization with field and greenhouse data, represents the initial step in building a decision support system for site-specific and variable-rate management of herbicide, fertilizer, and crop seeding rate that considers varying levels of available water and weed infestation.

Early-Harvest Barley (Hordeum vulgare) Silage Reduces Wild Oat (Avena fatua) Densities Under Zero Tillage1

Effective, long-term wild oat management requires an integrated approach that uses management techniques beyond simple herbicide application. A 5-yr (1996 to 2000) zero tillage study was conducted to assess the influence of barley harvest timing on wild oat densities in subsequent years at Lacombe, AB, Canada and Melfort, SK, Canada. Harvest timings included barley harvested 1 wk after heading (early), approximately 14 to 16 d later at the soft dough stage (normal), and at maturity (grain). In the absence of herbicides, wild oat densities decreased in silage plots harvested early and increased in grain plots. Reductions were more distinct at Lacombe where barley phenological differences and whole plant moisture contents between early and normal silage harvests were greater than at Melfort. Half rates of wild oat herbicides (ICIA 0604 and imazamethabenz) did not augment reductions in wild oat densities after early silage harvest, but did improve wild oat management after normal silage harvest, and in grain production. At Lacombe, early silage harvest reduced wild oat densities more than did herbicides in grain production. Similar trends were apparent at Melfort but were not statistically significant. Early barley silage harvests may be an effective integrated weed management tool for wild oat.Nomenclature: ICIA 0604 (proposed common name: tralkoxydim), 2-[1-(ethoxyimino)propyl]-3-hydroxy-5-(2,4,6-trimethylphenyl)cyclohex-2-enone; imazamethabenz; wild oat, Avena fatua L. #3 AVEFA; barley, Hordeum vulgare L. (‘AC Lacombe’).Additional index words: Cultural control, green forage, integrated weed management, seed rain, timing.

Herbicidal potential of pyrenophorol isolated from aDrechslera avenae pathotype

A pathotype of Drechslera avenae (Eidam) Scharif exhibited host-specificity, being pathogenic to Avena sterilis L but not to a number of related or unrelated species tested. In culture, the fungus produces a metabolite which was identified as the macrodiolide pyrenophorol (5,13-dihydroxy-8,16-dimethyl-1,9-dioxa-cyclohexadeca-3,11-diene-2,10-dione). This compound at a concentration of 320 µM was phytotoxic to A sterilis and considerably less so to Avena fatua L. The phytotoxicity was expressed as leaf necrosis on seedling cuttings partially immersed in pyrenophorol solution and as ‘green islands’ on detached leaves on which droplets of the solution were placed. Seed germination and seedling growth of A sterilis were not affected. Pyrenophorol at concentrations up to 640 µM did not cause any symptoms of phytotoxicity to a number of other monocotyledons or dicotyledons tested, with the exception of Lycopersicon esculentum Miller on which leaf necrosis was observed after application of the substance through the vascular system to seedling cuttings. These findings are discussed in relation to the exploitation of such compounds of natural origin as wild oat herbicides. © 2000 Society of Chemical Industry

Wild oat control and tolerance of grass seed crops to fenoxaprop-P-ethyl

Fenoxaprop P-ethyl, a wild oat herbicide was applied to five grass species. Perennial ryegrass was tolerant to 37 g/ha, but there was a trend for a reduction in seed yield at 75 g/ha. Two Bromus species had good tolerance, but Phalaris aquatica seed yields were reduced by 80%. In a second trial, there was no significant effect on seed yield of perennial and hybrid ryegrass to fenoxaprop applied at 56 g/ha. However, there was a trend for 75 g/ha to reduce seed yield in perennial ryegrass. In a perennial ryegrass seed crop, wild oats were very competitive, reducing seed yields from 2600 kg/ha (best herbicide treatment) to 660 kg/ha in the untreated control. Excellent wild oat control was achieved with fenoxaprop at rates of 45 g/ha in August and 56 g/ha in September.

Wild oat (Avena fatua) seed production in spring barley (Hordeum vulgare) is affected by the interaction of wild oat density and herbicide rate

The efficacy of current wild oat herbicides and their high cost have resulted in use rates that are less than those recommended. While acceptable weed control may be attained at less cost, this practice does not consider the potential for increased wild oat seed production. The objective of this experiment was to determine the interaction of wild oat density and reduced imazamethabenz rates on wild oat seed production in spring barley. As wild oat densities increased from 8 to 1,100 plants m−2, wild oat seed production increased from 180 to 9,950 seed m−2without herbicide, and from 0 to 2,810 seed m−2using 0.53 kg ai ha−1imazamethabenz. This general pattern was modeled using a cumulative logistic function. Estimates from this model indicated that < 1 wild oat seed m−2was produced at population densities of ≤ 20 plants at any imazamethabenz rate. Imazamethabenz rates of 0.26 kg ha−1or greater at wild oat densities of less than approximately 190 plants m−2did not result in wild oat seed production above the initial population density. As wild oat density increased, however, imazamethabenz rates below 0.40 kg ha−1resulted in substantially greater wild oat seed production compared to the recommended rate.

Response of Triallate-Resistant Wild Oat (Avena fatua) to Alternative Herbicides

Wild oat populations resistant to triallate have been identified in Alberta. Dose response experiments were conducted in the greenhouse to determine if triallate-resistant wild oat was controlled by other selective wild oat herbicides. Triallate-resistant wild oat populations were effectively controlled by atrazine, ethalfluralin, fenoxaprop-P, flamprop, imazamethabenz, and tralkoxydim. EPTC and cycloate, which are chemically related to triallate, differed in their efficacy on triallate-resistant wild oats. EPTC at the 0.25x field use rate was more efficacious on triallate-resistant than triallate-susceptible wild oat. In contrast, cycloate at the 0.25 to 0.5x field use rate was less efficacious on triallate-resistant than susceptible wild oats. At higher rates, both EPTC and cycloate killed triallate-resistant wild oat populations. Growers have several herbicide choices to selectively control triallate-resistant wild oat in prairie field crops but should plan to rotate herbicides among different chemical families and adopt integrated weed management practices to reduce the risk of these wild oat populations developing resistance to other wild oat herbicides.

Inheritance of resistance to diclofop-methyl and fenoxaprop-p-ethyl in two Avena sativa × A. fatua populations

Since the late 1980s, several reports of herbicide-resistant wild oat have raised concern about potential weed control problems in western Canada. This study was conducted to determine the mode of inheritance, number of genes and type of gene action governing herbicide resistance in two Avena sativa × A. fatua crosses. The herbicide-susceptible A. sativa cultivars, Random and Derby, were crossed with a resistant A. fatua genotype, GP-HR-01. Parents, F2s and F2:3 families were tested for their reactions to two post-emergent wild oat herbicides, diclofop-methyl and fenoxaprop-p-ethyl, in the greenhouse. Inheritance of resistance to diclofop-methyl and fenoxaprop-p-ethyl was dominant and monogenic in the Derby/GP-HR-01 cross, but was controlled by two dominant complementary genes in the Random/GP-HR-01 cross. Resistance to both herbicides appeared to be controlled by the same genes or groups of tightly linked genes. Key words:Avena sativa, Avena fatua, herbicide resistance, weed (genetics), diclofop-methyl, fenoxaprop-p-ethyl

Cross-Resistance of Several Diclofop-Resistant Wild Oat (Avena fatua) Biotypes From the Willamette Valley of Oregon

The first occurrences of wild oat resistance to diclofop in the Willamette Valley of Oregon were reported in 1990. Among eight resistant biotypes, GR50values for diclofop were 3 to 64 times greater than the GR50for a susceptible wild oat biotype. GR50values for other aryloxyphenoxypropionate herbicides varied from 1 to over 100 times greater than a susceptible biotype. Only one resistant biotype was resistant to cyclohexanedione herbicides, and this was only a three-fold increase in GR50. Except for one biotype that had a low level of resistance to pronamide, none of the wild oat biotypes were cross-resistant to any other commonly used wild oat herbicide. Levels of resistance and cross-resistance did not follow a consistent pattern among biotypes in this study, suggesting more than one resistance trait. There were significant differences in the light use efficiency, height, dry weight, leaf area, and extent and timing of tillering and flowering of four wild oat biotypes studied. These physiological and morphological differences suggest that these resistant biotypes were selected independently. The diversity of resistance patterns and the coevolution of resistance at several locations will add to the difficulty of resistance management

Integrated Wild Oat (Avena fatua) Management Affects Spring Barley (Hordeum vulgare) Yield and Economics

The effect of barley seeding rate and row spacing, and triallate, diclofop, and difenzoquat herbicide rate on barley grain yield and quality, and wild oat control were evaluated in field experiments near Bonners Ferry, Idaho, in 1989 and 1990. The purpose of the study was to develop integrated control strategies for wild oat in spring barley. Barley row spacing (9 and 18 cm) did not affect barley grain yield. Barley grain yield was greatest when barley was seeded at 134 or 201 kg ha–1compared to 67 kg ha–1. Wild oat control increased as wild oat herbicide rate increased and barley grain yield was greatest when wild oat herbicides were applied. However, barley grain yield was similar when wild oat biomass was reduced by either 65 or 85% by applications of half and full herbicide rates, respectively. Net return was greatest when the half rate of herbicide was applied to 100 wild oat plants per m2and was greatest when half or full herbicide rates were applied to 290 wild oat plants per m2. Net return increased when the seeding rate was increased to 134 or 201 kg ha–1when no herbicide was applied and when 290 wild oat plants per m2were present.

Wild-oat herbicide studies: barban herbicidal activity for wild-oat ( Avena fatua L.) control as influenced by adjuvants

The effect of barban at 0·35 kg a.i./ha alone or in mixture with eight surfactants at 0·5% (v/v), and two organic salts at 0·5% (v/w) on wild oat ( Avena fatua L.) fresh weight was investigated in the glasshouse. Barban with Atplus 411F and with Renex-36 reduced wild-oat fresh weight by 68–77% and 69–86%, respectively, compared with the untreated control, whereas barban alone reduced fresh weight by 36–48%. Barban with added ammonium sulphate also reduced fresh weight by 71%. The three-way mixture (barban+surfactant+ammonium sulphate) did not further reduce fresh weight. Mixtures of Atplus 411F and Renex-36 added in different proportions to barban reduced fresh weight by amounts similar to individual combinations of each surfactant and barban. The increased activity of barban when applied with Renex-36 counteracted the antagonistic effect of 2,4-D isopropyl ester or MCPA iso-octyl ester on wild-oat fresh-weight reduction, compared with barban plus 2,4-D or MCPA without surfactant. Simulated rainfall did not decrease wild-oat fresh-weight reduction with the barban/Renex-36 mixture. Under field conditions, barban plus Atplus 411F and ammonium sulphate gave better wild-oat control than barban alone and increased wheat-grain yield. This treatment also did not reduce wheat tolerance. More [ 14C]-barban was absorbed by wild oat when [ 14C]-barban was mixed with Atplus 411F or Renex-36 than when applied alone. The increased adsorption may provide some explanations for the improved wild-oat control with barban/adjuvant mixture.

Synthesis and plant growth regulating properties of derivatives of alkyl 3‐benzoyl‐3‐(3‐chloro‐4‐substituted phenyl)‐2‐methylcarbazates

AbstractAlkyl 3‐benzoyl‐3‐(3‐chloro‐4‐substituted‐phenyl)‐2‐methylcarbazates (isoelectronic analogues of wild oat herbicides) have plant growth regulating properties for various weeds and crops. Some derivatives of carbazates, bearing halogen in the 4‐position of the phenyl group, have been shown to have the highest activity of the prepared compounds.

The chromosomal locations in wheat of genes conferring differential response to the wild oat herbicide, difenzoquat

SummaryF2, monosomic analysis involving crosses between the monosomic series of a resistant wheat variety, Chinese Spring, and a susceptible variety, Sicco, has located a major gene locus, designated Dfql, on chromosome 2B of wheat which determines the differential response of these varieties to treatment with the wild oat herbicide, difenzoquat. The allele from Chinese Spring conferring resistance is dominant and studies of the responses of Chinese Spring single chromosome substitution lines and nullisomic–tetrasomic lines for chromosome 2B indicate that this allele actively promotes resistance to the herbicide. It is suggested that this gene may prevent inhibition of DNA synthesis in the apical meristem, which is the site of action of the herbicide (Pallett & Caseley, 1980).Other chromosomes were also implicated as carrying ‘modifier genes’ which affect the ratio of resistant: susceptible plants in F2 monosomic families, namely 1D, 2D, 3A, 3B, 5B and 5D. These chromosomes may affect the retention and translocation of the herbicide to the target site and hence the threshold of response.The simple inheritance of difenzoquat resistance indicates that it should be easy by conventional breeding techniques to transfer the resistance into susceptible varieties.

Variability for Response to Herbicides in Wild Oat (Avena fatua) Populations

Reaction of some wild oat (Avena fatuaL. ♯4AVEFA) populations to the herbicide triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] was investigated in a controlled-environment chamber. Under specified conditions, 1.0 mg active ingredient of triallate incorporated in 1 kg of soil was a satisfactory diagnostic rate for 14-day-old seedlings. Five seedling growth parameters were studied. These parameters were emergence, survival to produce first leaf, mesocotyl length, first-leaf length, and seedling height. Of these, mesocotyl length was least affected by triallate treatment, and significant differences in variability for triallate reaction were found within and among historically triallate unexposed, as well as exposed populations. Within-population variation for seedling emergence and survival was higher in unexposed than in exposed populations. Populations with recurrent exposure to triallate were more tolerant to the herbicide under experimental conditions than historically unexposed populations. Triallate-tolerant lines were identified which were tolerant to two other common wild oat herbicides.

Response of Spring Wheat to N Fertilizer Placement, Row Spacing, and Wild Oat Herbicides in a No‐Till System1

AbstractA 2‐year study was conducted on a north facing Thatuna silt loam (fine‐silty, mixed, mesic Xeric Argialbolls) to evaluate the influence of N fertilizer placement, crop row spacing, and wild oat (Avena fatuaL.) herbicides on wild oat populations and wheat (Triticum aestivumL.) yield in no‐till spring wheat. The treatments were factorial arrangements of ammonium nitrate either surface applied preplant or banded 50 mm below the crop seed at planting; wild oat control using triallate [S‐(2,3,3‐trichloroallyl)diisopropylthiocarbamate]pre‐emergence, difenzoquat [1,2‐dimethyl‐3,5‐diphenyl‐1H‐pyrazolium] post‐emergence, or no herbicide (check); and crop row spacings of either 200,300, or 400 mm. Surface‐applied fertilizer N significantly increased wild oat populations compared with banding the N fertilizer below the seed, but had no effect on dry weight or N uptake. Banded N increased total dry weight N uptake, and grain yields of wheat. These responses indicate that banded fertilizer N was positionally more available to wheat than was broadcast N, but banding N did not reduce availability of N to wild oat. However, surface‐applied N stimulated wild oat emergence. Triallate decreased wild oat populations compared to difenzoquat or no herbicide, but was no more effective than difenzoquat in reducing wild oat dry weight and total Kjeldahl N uptake. Both herbicides reduced wild oat dry weight as compared to the no herbicide check and significantly increased wheat yields. Row spacing did not affect wild oat dry weight or total N uptake, but the 200 m row increased wheat dry weight, total Kjeldahl N uptake, and grain yields compared to the 300 and 400 cm rows. There were no significant interactions.

Chlorsulfuron Reduced Control of Wild Oat (Avena fatua) with Diclofop, Difenzoquat, and Flamprop

The influence of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} on control of wild oat (Avena fatuaL. ♯3AVEFA) when mixed in the spray tank with three herbicides was tested in greenhouse and in field trials at Lacombe and Scott, Canada, during 1981 and 1982. In field experiments, chlorsulfuron mixed with diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid} caused a 4 to 35% reduction in control of wild oat. Mixtures of chlorsulfuron with difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) caused a 0 to 19% reduction and mixtures with flamprop {N-benzoyl-N-(3-chloro-4-fluorophenyl)-DL-alanine} a 2 to 30% reduction in control of wild oat. Addition of chlorsulfuron to the wild oat herbicides under greenhouse conditions also resulted in losses in control of wild oat. Increasing the rate of the wild oat herbicide in the mixture tended to overcome these losses.