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Khalid S. Alshallash - One of the best experts on this subject based on the ideXlab platform.
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Germination of weed species (Avena Fatua, Bromus catharticus, Chenopodium album and Phalaris minor) with implications for their dispersal and control
Elsevier, 2018Co-Authors: Khalid S. AlshallashAbstract:Climatic conditions for seed germination of four weed species, Avena Fatua, Bromus catharticus, Chenopodium album and Phalaris minor, which occur commonly in cereal fields in the north of Saudi Arabia, were compared. Proportionately, most seeds of the two collected seed lots germinated during the first three weeks of the experiment, confirming an early response pattern. Overall, germination was higher in Bromus catharticus, Avena Fatua and Phalaris minor than Chenopodium album. Compared to the other species, proportionately more Phalaris minor seeds germinated in the second period, indicating a higher propensity for slow germination. Germination in all species favoured alternating temperatures (10/20 °C or 5/25 °C) over a constant (15 °C), in a light/dark (16/8 h) regime. However, Avena Fatua and Bromus catharticus seeds also showed significant germination in a dark only (24 h) regime, indicating light has less influence on their germination. Variation in germination between geographically separate seed collections of all four species was significant in some conditions, however, the general pattern was of similar responses between the two seed lots. Results determined that, in respect of interactions between temperature and light, the most important climatic condition for maximum seed germination, in all four weed species, is alternating temperatures. The outcomes of this study can lead to the expected timings of weed species' germination and dispersal in field conditions, and are used to make recommendations for practical weed control measures. Keywords: Avena Fatua, Bromus catharticus, Chenopodium album, Phalaris minor, Climatic conditions, Weeds, Seed germination, Saudi Arabi
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Germination of weed species ( Avena Fatua , Bromus catharticus , Chenopodium album and Phalaris minor ) with implications for their dispersal and control
Annals of Agricultural Sciences, 2018Co-Authors: Khalid S. AlshallashAbstract:Abstract Climatic conditions for seed germination of four weed species, Avena Fatua, Bromus catharticus, Chenopodium album and Phalaris minor, which occur commonly in cereal fields in the north of Saudi Arabia, were compared. Proportionately, most seeds of the two collected seed lots germinated during the first three weeks of the experiment, confirming an early response pattern. Overall, germination was higher in Bromus catharticus, Avena Fatua and Phalaris minor than Chenopodium album. Compared to the other species, proportionately more Phalaris minor seeds germinated in the second period, indicating a higher propensity for slow germination. Germination in all species favoured alternating temperatures (10/20 °C or 5/25 °C) over a constant (15 °C), in a light/dark (16/8 h) regime. However, Avena Fatua and Bromus catharticus seeds also showed significant germination in a dark only (24 h) regime, indicating light has less influence on their germination. Variation in germination between geographically separate seed collections of all four species was significant in some conditions, however, the general pattern was of similar responses between the two seed lots. Results determined that, in respect of interactions between temperature and light, the most important climatic condition for maximum seed germination, in all four weed species, is alternating temperatures. The outcomes of this study can lead to the expected timings of weed species' germination and dispersal in field conditions, and are used to make recommendations for practical weed control measures.
A. Rashid - One of the best experts on this subject based on the ideXlab platform.
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Antagonism of tralkoxydim activity in Avena Fatua by metsulfuron methyl
Weed Research, 1993Co-Authors: M D Devine, A. RashidAbstract:Summary: Resume: Zusammenfassung In growth chamber experiments, tralkoxydim activity against Avena Fatua was significantly reduced by addition of metsulfuron methyl to the spray solution. This was apparent particularly at low rates of tralkoxydim (e.g., 125 g a.i.ha−1) and at high rates of metsulfuron methyl (8 or 12 g a.i. ha−1). Metsulfuron methyl alone reduced A. Fatua growth significantly, Chlorsul-furon, which did not reduce A. Fatua growth at rates of up to 33 g a.i. ha−1, caused only a slight loss in tralkoxydim activity. When applied in combination, metsulfuron methyl reduced the uptake of foliar-applied 14C-tralkoxydim 6 h after application, but did not affect uptake or translocation of 14C-tralkoxydim at subsequent sampling times. In in vitro assays, metsulfuron methyl at 10 or 100 nM in the assay medium had no effect on acetyl-coenzyme A carboxylase (ACCase) activity in A.Fatua, nor did it interfere with the inhibition of ACCase by tralkoxydim. In addition, treatment of A. Fatua plants with metsulfuron methyl at 4, 8 or 12 g ha−1 did not reduce the level of extractable ACCase activity when the plants were harvested 24–96 h after spraying. Thus, no apparent physiological or biochemical basis for the antagonism of tralkoxydim was identified. The temporary growth inhibition induced by metsulfuron methyl may be of sufficient duration for most of the tralkoxydim to be metabolized to inactive products, thereby reducing tralkoxydim-induced injury. Antagonisme entre le metsulfuron-methyl et l'activite de la tralkoxydime sur Avena Fatua Dans des essais en chambres climatiques, l'activite de la tralkoxydime contre Avena Fatua a ete significativement reduite par l'adjonction de metsulfuron-methyl dans la bouillie de pulverisation. Ceci est particulierement apparent a de faibles doses de tralkoxydime (ex. 125 g. m.a. ha−1) et a de faibles doses de metsulfuron-methyl (8 a 12 g m.a. ha−1). Le metsulfuron-methyl seul reduit la croissance d'Avena Fatua. Le chlorsulfuron qui ne reduit pas la croissance d'Avena Fatuaa des doses jusqu'a 33 g m.a. ha−1 cause seulement une faible perte d'efficacite chez la tralkoxydime. Quand il est applique en melange, le metsulfuron-methyl a reduit l'absorption de la C14 tralkoxydime appliquee sur les feuilles 6 h apres l'application, mais n'a pas affecte l'absorption et le transport de la C14 tralkoxydime aux autres temps d'echantillonage ulterieurs. Dans les essais in vitro, le metsulfuron-methyl a 10 ou 100 nm dans le milieu d'essai n'a pas eu d'effet sur l'activite de l'acetyl coenzyme A carboxylase (ACCase), ni n'a interfere avec l'inhibition de l'ACCase par la tralkoxydime. En outre, le traitement d'Avena Fatua avec du metsulfuron-methyl a 4, 8 ou 12 g ha−1 n'a pas reduit le niveau d'activite d'ACCase quand les plantes etaient recoltees de 24 a 96 h apres l'application. Ainsi aucune base apparente physiologique ou biochimique pour l'antagonisme de la tralkoxydime n'a ete identifiee. L'inhibition temporaire de la croissance induite par le metsulfuron-methyl peut etre d'une duree suffisante pour que la plus grande partie de la tralkoxydime soit metabolisee en produits inactifs, et de ce fait reduit les effets induits par la tralkoxydime. Antagonismus von Metsulfuron-methyl auf die Wirkung von Tralkoxydim auf Avenua Fatua In Phytotron-Versuchen wurde die Wirkung von Tralkoxydim auf Avena Fatua durch Zugabe von Metsulfuron-methyl in die Spritzbruhe signifikant herabgesetzt, besonders bei niedrigen Tralkoxydim-Dosen (z. B. 125 g AS ha−1) und bei hohen Metsulfuron-methyl-Dosen (8 oder 12 g AS ha−1). Metsulfuron-methyl allein setzte das Wachstum von Avena Fatua signifikant herab. Mit Chlorsulfuron, das das Wachstum von Avena Fatua bis 33 g AS ha−1 nicht verminderte, lies sich die Wirkung von Tralkoxydim nur wenig beeintrachtigen. In Kombination reduzierte Metsulfuron-methyl die Blattaufnahme von 14C-Tralkoxydim 6 h nach der Applikation, aber bei spateren Probennahmen waren Aufnahme und Translokation von 14C- Tralkoxydim nicht beeintrachtigt. In In-vitro-Versuchen blieben 10 oder 100 mm Metsulfuron in der Versuchslosung ohne Wirkung auf die Aktivitat der Acetyl-Coenzym-A-Carboxylase (ACCase) in Avena Fatua, es wirkte auch nicht auf die Hemmung der ACCase durch Tralkoxydim. Auch eine Behandlung von Avena-Fatua-Pflanzen mit 4, 8 oder 12 g AS ha−1 Metsulfuron-methyl setzte nach 24 bis 96 h die ACCase-Aktivitat nicht herab. So konnte keine offensichtliche physiologische oder biochemische Basis fur den Antagonismus von Tralkoxydim gefunden werden. Die durch Metsulfuron-methyl induzierte zeitweilige Wuchshemmung kann lang genug sein, das das meiste Tralkoxydim zu inaktiven Produkten abgebaut wird, so das seine Wirksamkeit reduziert wird.
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Antagonism of tralkoxydim activity in Avena Fatua by metsulfuron methyl
Weed Research, 1993Co-Authors: M D Devine, A. RashidAbstract:Summary: Resume: Zusammenfassung In growth chamber experiments, tralkoxydim activity against Avena Fatua was significantly reduced by addition of metsulfuron methyl to the spray solution. This was apparent particularly at low rates of tralkoxydim (e.g., 125 g a.i.ha−1) and at high rates of metsulfuron methyl (8 or 12 g a.i. ha−1). Metsulfuron methyl alone reduced A. Fatua growth significantly, Chlorsul-furon, which did not reduce A. Fatua growth at rates of up to 33 g a.i. ha−1, caused only a slight loss in tralkoxydim activity. When applied in combination, metsulfuron methyl reduced the uptake of foliar-applied 14C-tralkoxydim 6 h after application, but did not affect uptake or translocation of 14C-tralkoxydim at subsequent sampling times. In in vitro assays, metsulfuron methyl at 10 or 100 nM in the assay medium had no effect on acetyl-coenzyme A carboxylase (ACCase) activity in A.Fatua, nor did it interfere with the inhibition of ACCase by tralkoxydim. In addition, treatment of A. Fatua plants with metsulfuron methyl at 4, 8 or 12 g ha−1 did not reduce the level of extractable ACCase activity when the plants were harvested 24–96 h after spraying. Thus, no apparent physiological or biochemical basis for the antagonism of tralkoxydim was identified. The temporary growth inhibition induced by metsulfuron methyl may be of sufficient duration for most of the tralkoxydim to be metabolized to inactive products, thereby reducing tralkoxydim-induced injury. Antagonisme entre le metsulfuron-methyl et l'activite de la tralkoxydime sur Avena Fatua Dans des essais en chambres climatiques, l'activite de la tralkoxydime contre Avena Fatua a ete significativement reduite par l'adjonction de metsulfuron-methyl dans la bouillie de pulverisation. Ceci est particulierement apparent a de faibles doses de tralkoxydime (ex. 125 g. m.a. ha−1) et a de faibles doses de metsulfuron-methyl (8 a 12 g m.a. ha−1). Le metsulfuron-methyl seul reduit la croissance d'Avena Fatua. Le chlorsulfuron qui ne reduit pas la croissance d'Avena Fatuaa des doses jusqu'a 33 g m.a. ha−1 cause seulement une faible perte d'efficacite chez la tralkoxydime. Quand il est applique en melange, le metsulfuron-methyl a reduit l'absorption de la C14 tralkoxydime appliquee sur les feuilles 6 h apres l'application, mais n'a pas affecte l'absorption et le transport de la C14 tralkoxydime aux autres temps d'echantillonage ulterieurs. Dans les essais in vitro, le metsulfuron-methyl a 10 ou 100 nm dans le milieu d'essai n'a pas eu d'effet sur l'activite de l'acetyl coenzyme A carboxylase (ACCase), ni n'a interfere avec l'inhibition de l'ACCase par la tralkoxydime. En outre, le traitement d'Avena Fatua avec du metsulfuron-methyl a 4, 8 ou 12 g ha−1 n'a pas reduit le niveau d'activite d'ACCase quand les plantes etaient recoltees de 24 a 96 h apres l'application. Ainsi aucune base apparente physiologique ou biochimique pour l'antagonisme de la tralkoxydime n'a ete identifiee. L'inhibition temporaire de la croissance induite par le metsulfuron-methyl peut etre d'une duree suffisante pour que la plus grande partie de la tralkoxydime soit metabolisee en produits inactifs, et de ce fait reduit les effets induits par la tralkoxydime. Antagonismus von Metsulfuron-methyl auf die Wirkung von Tralkoxydim auf Avenua Fatua In Phytotron-Versuchen wurde die Wirkung von Tralkoxydim auf Avena Fatua durch Zugabe von Metsulfuron-methyl in die Spritzbruhe signifikant herabgesetzt, besonders bei niedrigen Tralkoxydim-Dosen (z. B. 125 g AS ha−1) und bei hohen Metsulfuron-methyl-Dosen (8 oder 12 g AS ha−1). Metsulfuron-methyl allein setzte das Wachstum von Avena Fatua signifikant herab. Mit Chlorsulfuron, das das Wachstum von Avena Fatua bis 33 g AS ha−1 nicht verminderte, lies sich die Wirkung von Tralkoxydim nur wenig beeintrachtigen. In Kombination reduzierte Metsulfuron-methyl die Blattaufnahme von 14C-Tralkoxydim 6 h nach der Applikation, aber bei spateren Probennahmen waren Aufnahme und Translokation von 14C- Tralkoxydim nicht beeintrachtigt. In In-vitro-Versuchen blieben 10 oder 100 mm Metsulfuron in der Versuchslosung ohne Wirkung auf die Aktivitat der Acetyl-Coenzym-A-Carboxylase (ACCase) in Avena Fatua, es wirkte auch nicht auf die Hemmung der ACCase durch Tralkoxydim. Auch eine Behandlung von Avena-Fatua-Pflanzen mit 4, 8 oder 12 g AS ha−1 Metsulfuron-methyl setzte nach 24 bis 96 h die ACCase-Aktivitat nicht herab. So konnte keine offensichtliche physiologische oder biochemische Basis fur den Antagonismus von Tralkoxydim gefunden werden. Die durch Metsulfuron-methyl induzierte zeitweilige Wuchshemmung kann lang genug sein, das das meiste Tralkoxydim zu inaktiven Produkten abgebaut wird, so das seine Wirksamkeit reduziert wird.
Roger D. Cousens - One of the best experts on this subject based on the ideXlab platform.
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A simulation model of Avena Fatua L. (wild-oat) growth and development.
Annals of Applied Biology, 1993Co-Authors: S. E. Weaver, Martin J. Kropff, Roger D. CousensAbstract:Summary An eco-physiological simulation model of the growth and development of Avena Fatua was parameterised and tested. The model simulates growth ofA. Fatua, in kg dry matter ha-1 day-1 from sowing to maturity as a function of irradiance, temperature and various species characteristics. Parameter values were derived from the literature and from field experiments, including both autumn and spring sowings of A. Fatua over three years at two sites in southern England. With two exceptions, a single set of parameter values was sufficient to accurately simulate the emergence, growth and development of both autumn and spring cohorts over all years and sites. The two exceptions were the result of differences between autumn and spring cohorts of A. Fatua in the rate of early leaf area growth and in the relationship between specific leaf area and developmental stage.
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Growth and development of Avena Fatua (Wild-oat) in the field
Annals of Applied Biology, 1992Co-Authors: Roger D. Cousens, S. E. Weaver, J. R. Porter, Joy M. Rooney, D. R. Butler, Mark P. JohnsonAbstract:Summary The growth and development of field-grown Avena Fatua plants were studied for autumn and spring sowings in two consecutive years. The duration of various growth stages from sowing until anthesis was quantified in terms of thermal time (accumulated degree days) or photothermal time (degree days modified by photoperiod). Base temperatures and photoperiods for developmental phases were estimated as those which minimised the coefficient of variation among sowing dates. Relationships were derived between leaf emergence, canopy height, plant leaf area, and photothermal time. Stem extension and flowering occurred earlier in autumn-sown plants than spring-sown plants. Autumn-sown plants produced more leaves on the main stem, and had greater leaf area and above-ground biomass at anthesis than spring-sown plants.
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Dynamics of competition between wild oats (Avena Fatua L.) and winter cereals
Weed Research, 1991Co-Authors: Roger D. Cousens, S. E. Weaver, T. D. Martin, A. M. Blair, J WilsonAbstract:Summary: This study examined the effects of competition on the growth of Avena Fatua, winter wheat and winter barley. Plants were sampled at frequent intervals from replacement series experiments at two contrasting sites in the U.K. A. Fatua was much slower to establish than the two cereals, but thereafter exhibited a faster rate of growth. In monoculture, it took a considerable time for A. Fatua to reach a size equal to that of the cereals, but by the end of the experiments it was the largest of the three species. The change-over from cereal dominance in mixtures to A. Fatua tiominance was rapid, and in three cases coincided with cereal flag leaf emergence. In the fourth case, it appeared to coincide with the art of canopy height extension. At one site the rder of competitiveness at anthesis was A. Fatua= barley>wheat, and at the other site the order was A. Fatua>wheat>barley. In order to explain and predict differences between years and sites, more studies are required on morphological development in relation to abiotic variables. Resume: Cette etude examine les effets de la competition entre les croissances d'Avena Fatua, des orges et des bles d'hiver. Les plantes ont eteechantillonnees a intervalles frequents a partir d'experimentation en series de remplacement dans deux sites contrastes du Royaume-Uni. Avena Fatua s'etablit beaucoup plus lentement que les deux cereales, mais par la suite a un taux de croissance plus rapide. En monoculture, il faut un temps important pour qu'A. Fatua atteigne une taille egale a celles des cereales, mais a la fin des experimentations, c'etait la plus grande des 3 especes. Le changement de dominance des cereales en melange avec d'A. Fatua est rapide et coincide dans les 3 cas a la sortie de la derniere feuille. Dans l'autre cas, il a coincide au depart de Textension de la hauteur de la canopee. Sur un site, l'ordre de competitivitea l'anthese etait: A. Fatua= orge>ble, et sur l'autre A. Fatua>ble>orge. En vue d'expliquer et de prevoir les differences entre les annees et les lieux, un travail supplementaire est necessaire sur le developpement morphologique en relation avec des variables abiotiques. Zusammenfassung: Es wurde die Wirkung der Konkurrenz auf das Wachstum von Avena Fatua, Winterweizen und Wintergerste untersucht. Die Pflanzenproben wurden zu verschiedenen Zeitpunkten aus sub-stitutiven Versuchen an 2 gegensatzlichen Orten im Vereinigten Konigreich gezogen. Avena Fatua etablierte sich viel langsamer als die beiden Getreidearten, aber spater hatte das Unkraut eine grosere Wachstumsrate. In Reinkultur erreichte Avena Fatua die gleiche Grose wie die Getreide erst nach einiger Zeit, doch am Versuchsende war die Art die groste von allen drei. Der Ubergang von der Getreidedominanz in Mischungen zur Avena-Fatua-Dominanz war schnell und fiel in 3 Fallen mit dem Erscheinen des Fahnenblatts zusammen. Im anderen Fall schien er mit dem Bestandesschlus zusammenzufallen. Zur Zeit der Blute war das Konkurrenzverhaltnis an dem einen Ort Avena Fatua= Wintergerste > Winterweizen, am anderen Avena Fatua > Winterweizen > Wintergerste. Fur die Interpretation und die Prognose von Unterschieden zwischen den verschiedenen Jahren und Orten sind weitere Untersuchungen uber die morphologische Entwicklung in Abhangigkeit von abiotischen Faktoren erforderlich.
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The response of spring barley and winter wheat to Avena Fatua population density
Annals of Applied Biology, 1990Co-Authors: Bernard J. Wilson, Roger D. Cousens, K. J. WrightAbstract:Summary Populations of Avena Fatua were established in crops of spring barley and winter wheat, and relationships derived between yield and other crop parameters, and weed density. Competitive effects of A. Fatua, which were similar to those found in other countries, were greatest at low crop densities. Crop head numbers were reduced proportionately less than crop yield, indicating that competition was affecting other yield components. Competition increased the proportion of thin grain of barley but not of wheat. Competition had little effect on the moisture content and the contamination of the harvested grain by A. Fatua, suggesting that at threshold populations these factors are unlikely to be of economic significance. It was concluded that at average crop densities, low infestations of A. Fatua are likely to result in cereal yield losses in the region of 1 % for each A. Fatua plant m-2.
Guo Qing-yun - One of the best experts on this subject based on the ideXlab platform.
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Effect of 81.5% Acetochlor EC on the Weeds Avena Fatua L. Control in Spring Rape Field
Weed Science, 2012Co-Authors: Guo Qing-yunAbstract:Before sowing of the spring rape seeds the soil was sprayed with 81.5% acetochlor EC at the dosage of 993.87 g/hm2 mixed with 300 L/hm2 water.Effective controlling rate of weeds(Avena Fatua L.) was 73.63% which should be safe to crops,and the rape yield could be increased by 8.06% after this herbicide treatment.
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Control Effects of Fenoxaprop-p-ethyl against Avena Fatua in Highland Barley Field
Hubei Agricultural Sciences, 2011Co-Authors: Guo Qing-yunAbstract:Trials of fenoxaprop-p-ethyl EW for control of Avena Fatua were conducted in highland barley field.The result showed that the normal dosage of 69 g/L fenoxaprop-p-ethyl EW was 900～1 200 mL/hm2(effective dose was 62.1～82.8 g/hm2).It was sprayed on stems and leaves at 300 kg/hm2 during 3～5 leaves in highland barley.Its plant control effect was 81.2%～89.0%,and fresh control effect was 83.2%～90.8% after 40 days.It had good control effect on weeds and was safe to highland barley.After the application,the yield of highland barley increased by 3.5%～11.8%.
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Identification and Virulence of Three Fusarium Strains against Avena Fatua and Safety on 5 Crops
Journal of Biological Control, 2010Co-Authors: Guo Qing-yunAbstract:Based on morphology observation and sequence analysis,three strains isolated from Avena Fatua L.,ill soil of Microula sikkimensis Hemslon and Melilotus suaveolens Ledeb in Qinghai province were identified as Fusarium Avenaceum,F.proliferatum and F.chlamydosporum,respectively.The tests in vitro and in vivo showed that three strains presented intensive inhibitory effects on the germination of A.Fatua seeds.These three strains demonstrated significant herbicidal activity against A.Fatua,with high inhibitory rate of seedling fresh weight. Their safety to major crops in Qinghai was tested by pot bioassay.Results indicated that they were sensitive to cereal crops such as wheat and highland barley,but safe to other major crops such as broad bean,pea and cole.The three Fusarium strains were promising to be candidates of herbicide to broad bean,pea and cole.
Hugh J. Beckie - One of the best experts on this subject based on the ideXlab platform.
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The Biology of Canadian Weeds. 27. Avena Fatua L. (updated)
Canadian Journal of Plant Science, 2012Co-Authors: Hugh J. Beckie, Ardath Francis, Linda M. HallAbstract:Beckie, H. J., Francis, A. and Hall, L. M. 2012. The Biology of Canadian Weeds. 27. Avena Fatua L. (Updated). Can. J. Plant Sci. 92: 1329-1357. An updated review of biological information is provided for Avena Fatua. A widespread species originating in Eurasia, A. Fatua is one of the 10 worst annual weeds of temperate agricultural regions of the world. Key weediness traits of this highly selfing species include fecundity, seed shatter, and a large and persistent seed bank with variable degrees of primary seed dormancy. The species occurs in all Canadian provinces and most states in the USA. In Canada, it is most troublesome as a weed in the prairies, where it has spread throughout crop areas in all climatic zones. Depending upon plant density and relative time of emergence, A. Fatua competition may reduce annual crop yields by as much as 70%. First cohort emergence of A. Fatua coincides with planting and emergence of spring-seeded crops, although additional cohorts can emerge throughout the growing season. Avena Fatua is more abundant in zero-than intensive-tillage systems; the former regime promotes earlier and greater emergence because of a shallower and less persistent seed bank. Despite the introduction of highly efficacious herbicides in the 1970s and 1980s, abundance of the species has not declined across the Canadian prairies or elsewhere. The continual evolution of herbicide-resistant A. Fatua populations, seed spread via farm machinery, and limited herbicide modes of action for its control threaten sustained annual field crop production in many temperate agricultural areas. Further adoption and integration of multiple non-herbicidal weed management practices, such as enhanced crop seeding rate, competitive crops and cultivars, and precision fertilizer placement, should help mitigate A. Fatua interference. The species has some beneficial uses as an alternative feed and food constituent or industrial feedstock, as well as potential in cultivated oat (Avena sativa L.) improvement.
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nature occurrence and cost of herbicide resistant wild oat Avena Fatua in small grain production areas
Weed Technology, 1999Co-Authors: Hugh J. Beckie, A G Thomas, Anne Legere, D J Kelner, R C Van Acker, Scott MeersAbstract:Surveys were conducted across the northern Great Plains of Canada in 1996 and 1997 to determine the nature and occurrence of herbicide-resistant (HR) biotypes of wild oat (Avena Fatua). The surveys indicated that resistance to acetyl-CoA carboxylase (ACCase) inhibitors (Group 1) occurred most frequently relative to other herbicide groups. Group 1-HR wild oat occurred in over one-half of fields surveyed in each of the three prairie provinces. Of particular concern was the relatively high incidence of multiple-group resistance in wild oat in Saskatchewan and Manitoba. In Saskatchewan, 18% of Group 1-HR populations were also resistant to acetolactate synthase inhibitors (imidazolinones), even though these herbicides were not frequently used. In Manitoba, 27% of fields surveyed had wild oat resistant to herbicides from more than one group. Four populations were resistant to all herbicides registered for use in wheat (Triticum aestivum). Depending on the nature of resistance in wild oat, alternative herbicides available for their control may substantially increase costs to the grower. The cost to growers of managing HR wild oat in Saskatchewan and Manitoba using alternative herbicides is estimated at over $4 million annually. For some HR biotypes, alternative herbicides either are not available or all have the same site of action, which restricts crop or herbicide rotation options and threatens the future sustainability of small-grain annual cropping systems where these infestations occur. Nomenclature: Wild oat, Avena Fatua L. #3 AVEFA; wheat, Triticum aestivum L. Additional index words: Surveys, acetyl-CoA carboxylase (ACCase) inhibitors, acetolactate synthase (ALS) inhibitors; multiple-group resistance, AVEFA. Abbreviations: ACCase, acetyl-CoA carboxylase (EC 6.4.1.2); ALS, acetolactate synthase (EC 4.1.3.18); AOPP, aryloxyphenoxy propionate; CHD, cyclohexanedione; HR, herbicide-resistant; POST, postemergence; PRE, preemergence; S, susceptible.
