Some factors affecting the performance of fluazifop-butyl against Elymus repens (L.) Gould (=Agropyron repens (L.) Beauv.)

In this series of glasshouse experiments, several factors influencing the foliar activity of fluazifop-butyl, butyl-2-[4-(5-trifluoromethyl-2-pyridylox-y)phenoxy] propionate, against Elymus repens (L.) Gould (=Agropyron repens(L.) Beauv.) were investigated. The growth stage of the weed even up to about 16 weeks of age was not found to be a major factor affecting the performance, if a dose of 1.0 kg ai ha^?1 is used. The activity of fluazifop-butyl was affected by low temperature, low humidity and water stress, all of which reduced the herbicide performance to varying extents. High post-treatment temperature or humidity favoured the activity of the herbicide, as measured from the regrowth ability of treated plants. Moderate water stress did not affect the activity significantly, but severe stress led to the plants becoming more tolerant of the herbicide. The effect of light/shade on foliar activity was not clear, bin showed a tendency of decreasing with increasing shade. Adverse effects of rain, probably due to wash-off of the retained spray droplets, reduced the performance of fluazifop-butyl, if rain fell within 6 h of spraying. Certains facteurs qui touchent à la performance du fluazifop-butyle contre Elymus repens (L.)Gould. (= Agropyron repens (L.) Beauv.) Cette expérimentation en serre a porté sur plusieurs facteurs qui influent sur l'activité foliaire du fluazifop-butyle, butyle-2–4-(5-trifluorométhyl-2-pyridyloxy)phénoxy proprionate, contre Elymus repens (L.) Gould (Agropyron repens (L.) Beauv.). Il en résulte que, même jusqu'à l'âge de 16 semaines, le stade végétal de l'adventice ne paraît pas jouer un rôle important dans la performance de l'herbicide à une dose de 1,0 kg ma ha^?1. L'activité du fluazifop-butyle se trouve altérée en conséquence de température faibles, d'une faible humidité et de carence d'eau; tous ces facteurs ont amené une réduction plus ou moins grande dans la performance de l'herbicide. A en juger part la croissance nouvelle des plantes traitées, une température élevée, de même qu'une forte humidité suivant l'application, favorisent l'activité herbicide. La carence d'eau n'a exercé une influence significative sur l'activité herbicide que lorsqu'elle est devenue sévère; alors les plantes ont fait preuve d'une moindre tolérance. L'influence de la lumière sur l'activité foliaire est restée imprécise mais celle-ci a eu tendance à dimineur à mesure qu'augmentait l'ombre. Les effets néfastes de la pluie, grâce sans doute au lessivage des gouttelettes retenues sur les feuilles, ont diminué l'efficacité du fluazifop-butyle lors d'une précipitation moins de 6 heures après la pulvérisation. Einflüsse auf die Wirkung von Fluazifop-butyl auf Elymus repens (L.)Gould. (= Agropyron repens (L.) Beauv.) Verschiedene Einflüsse auf die Blattwirkung von Fluazifop-butyl Butyl-2-[4-(5-trifluormethyl-2-pyridiloxy)phenoxy]propionate auf die Gemeine Quecke wurden in einer Reihe von Versuchen im Gewächshaus untersucht. Das Entwicklungsstadium des Unkrauts war auch bei bis zu 16 Wochen alten Pflanzen ohne Einfluss auf die Wirkung, solange 1,0 kgAS ha^?1 angewandt wurden. Niedrige Temperatur und Luftfeuchtigkeit sowie Wassermangel setzen die Wirkung des Herbizids, die am Wiederaustrieb gemessen wurde, herab. Hohe Temperatur und Luftfeuchtigkeit nach der Behandlung begünstigten die Wirkung. Schwacher Wassermangel beeinflusste die Wirkung nicht signifikant, aber bei starkem Wassermangel waren die Pflanzen widerstandsfähiger. Die Wirkung einer Beschattung der Pflanzen auf die Wirksamkeit des Herbizids war undeutlich, aber tendenziell zeigte sich eine Abnahme der Wirkung mit Zunahme der Beschattung. Regen innerhalb 6 Stunden nach der Behandlung verminderte die Wirkung von Ftuazifop-butyl, vermutlich wegen des Abwaschens des Spritzbelags von den Blättern.     

Effects of repeated applications of fluazifop-butyl, haloxyfop and sethoxydim on Elymus repens in strawberries

Fluazifop-butyl, haloxyfop and sethoxydim with adjuvant oil were applied for three successive growing seasons to established strawberries infested with Elymus repens. The weed was virtually eradicated by three applications of haloxyfop (0.8 kg a.e. ha^?1) in successive years. A similar effect was given by five applications of haloxyfop (0.4 kg a.e. ha^?1) and fluazifop-butyl (1.6 kg AI ha^?1) in three growing seasons. Lower rates of haloxyfop and fluazifop-butyl, and a high rate of sethoxydim (1.6 kg AI ha^?1) applied five times were less effective, the ground cover of E. repens shoots not being reduced by the end of the experiment although weight of living rhizome was only 10-30% of that on untreated plots. Fruit yields on treated plots generally reflected the level of E. repens control, but there was some evidence of crop phytotoxicity from herbicide treatments. During the experiment E. repens untreated plots increased from about 30-100% ground cover and reduced yield 13, 28 and 68% in successive years compared with weed-free plots.     

Effects of fluazifop-butyl on shoot growth and rhizome buds of Elymus repens (L.) Gould

A series of glasshouse experiments was conducted to evaluate the activity of fluazifop-butyl, butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate, against Elymus repens. Foliar applications of doses 0·25–1·0 kg ha^?1 consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome-bud viability. At low doses (0·125 and 0·25 kg ha^?1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop-butyl was sprayed at a dose range of 0·125–1·0 kg ha^?1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha^?1, 31, 72 and 92% of rhizome buds were found to be non-viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha^?1 all the buds had accumulated sufficient herbicide to prevent sprouting 48 h after spraying.     

Pre-treatment environmental effects on the uptake, translocation, metabolism and performance of fluazifop-butyl in Elymus repens

The performance of fluazifop-butyl against Elymus repens (L.) Gould was significantly influenced by the environmental conditions in which the plants had grown prior to treatment as follows: soil moisture deficit (greatest reduction of herbicide performance) > cool temperatures > low light intensity. The level of control under conditions in which none of these factors was reduced (so-called ‘standard’ conditions) was similar to that observed for‘low light’regime plants. Significant effects of environment on spray retention, foliar uptake and amounts of herbicide translocated to the roots and rhizomes were observed. The lowest rates of herbicide uptake were found with plants grown under cool conditions, the greatest amount of basipetal herbicide translocation being associated with low light intensities. Rates of herbicide de-esterification were much lower in plants grown under low light intensities, cool temperatures, or soil moisture deficits than in those plants grown under the ‘standard’ conditions. This result was confirmed by studies of herbicide deesterification using cell-free leaf homogenates.     

Growth of Elymus repens (L.) Gould and Agrostis gigantea Roth. at different light intensities

Elymus repens (L.) Gould and Agrostis gigantea Roth. raised from rhizomes both responded to reduced light intensity by increased stem length, while the number of aerial shoots was reduced. The weight of the aerial parts was not influenced by a 50% reduction of the daylight intensity, but a further reduction of light caused a significant decrease in weight. The production of new rhizomes was more influenced by shading than were the aerial shoots. The consequence was an increase in the shoot/rhizome ratio. The food reserve per bud measured as inter-node weight in E. repens and A. gigantea was reduced only with intensive shading, and the vitality of the rhizomes appeared independent of light intensity. Intensive shading in early as compared to late summer caused a reduction in the number and weight of aerial shoots, but not in the weight of new rhizomes. Light intensities equal to those found in a spring wheat crop allowed more E. repens growth than light intensities equal to those in a spring oat crop. E. repens raised from seeds and grown at light intensities equal to those found in a cereal crop, showed insignificant rhizome production.     

Modelling the effects of Elymus repens (L.) Gould competition on yield of cereals, peas and oilseed rape

Effects of Elymus repens (L.) Gould competition on yield of winter rye (Secale cereale L.), winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), peas (Pisum sativum L.), and spring oilseed rape (Brassica napus L.) were studied in field trials conducted on the same location through 3 years. The competitiveness of the five crops against E. repens could be ranked as follows, with the most competitive crop mentioned first: rye wheat, barley rape, peas. Yield losses ranged from 8% in rye to around 35% in peas and rape at a density level of 100 primary shoots m^?2 in spring. The different prevailing climatic conditions in the growing seasons had no effect on the yield-density relationships in rye, peas, and barley, whereas significant interactions were found in wheat and rape. The cumulative emergence patternsof primary shoots were described in the spring-sown crops, and models were derived to simulate the sensitivity of competition parameters to the actual time of shoot recording. The importance of choosing the right time for shoot emergence counts in relation to threshold recommendations and other aspects is discussed. Modélisation de l'effet de la concurrence de Elymus repens (L.) Gould sur les rendements de céréales, de pois et de colza Nous avons étudié au champ les effets de la concurrence de Elymus repens (L.) Gould sur le rendement du seigle d'hiver (Secale cereale L.), du blé d'hiver (Triticum aestivum L.), de l'orge de printemps (Hordeum vulgare L.), du pois (Pisum sativum L.) et du colza de printemps (Brassica napus L.). Les essais ont été conduits durant trois ans sur le même site. L'aptitude à la concurrence des cinq cultures à l'égard de E. repens peut être classée ainsi, en ordre décroissant: seigle blé et orge colza et pois. Les pertes de rendement allaient de 8% chez le seigle à environ 35% chez le pois et le colza, à un densité de pousses primaires 100 m^?2, mesurée au printemps. Les différentes conditions météorologiques ayant régné lors des périodes de croissance n'ont eu aucun effet sur les relations densité-rendement chez le seigle, le pois et l'orge, alors que des interactions significatives ont été observées chez le blé et le colza. Le patron cumulatif de l'émergence des pousses primaires a été décrit pour les cultures de printemps, et des mode les en ont été déduits pour simuler la sensibilité des paramètres de concurrence à la date à laquelle les levées sont enregistrées. L'importance est discutée du choix d'une date correcte pour les comptages de levées dans l'optique de recommandations de seuils de densité. Modellierung der Wirkung der Konkurrenz von Elymus repens (L.) Gould auf den Ertrag von Getreide, Erbse und Raps Die Wirkung der Konkurrenz der Gemeinen Quecke (Elymus repens) auf Winterroggen (Secale cereale L.), Winterweizen (Triticum aestivum L.) Sommergerste (Hordeum vulgare L.), Saat-Erbse (Pisum sativum L.) und Sommerraps (Brassica napus L.) wurde in Feldversuchen über drei Vegetationsperioden am selben Ort untersucht. Für die Konkurrenzkraft der fünf Kulturen gegenüber der Quecke ergab sich folgende Reihenfolge: Roggen Weizen, Gerste Raps, Erbse. Die Ertragsverluste lagen bei einer Dichte von 100 Queckenhalmen m² im Frühjahr zwischen 8 % beim Roggen und rund 35 % bei Erbse und Raps. Die verschiedenen Witterungsbedingungen in den Versuchsjahren blieben ohne Einfluß auf die Ertrags-Dichte-Beziehungen bei Roggen, Erbse und Gerste, während bei Weizen und Raps eine signifikante Beeinflussung gefunden wurde. Das Austriebsverhalten der Queckentriebe wurde in den Sommerkulturen festgehalten, und es wurden Modelle entwickelt, um die Empfindlichkeit der Konkurrenzparameter in Abhängigkeit vom Zeitpunkt der Zählung der Triebe zu simulieren. Die Bedeutung der Wahl des richtigen Zeitpunkts für die Erfassung des Austriebs der Quecke hinsichtlich der Empfehlung von Schwellenwerten und anderen Aspekten wird diskutiert.     

Effect of fluazifop-butyl on the chlorophyll content, fluorescence and chloroplast ultrastructure of Elymus repens (L.) Gould. leaves

Some aspects of the action of fluazifop-butyl on the chlorophyll content, chloroplast functioning and chloroplast ultrastructure of Elymus repens are reported. Over a period of 0–12 days after spraying with 0.25 or 1.0 kg ha^?1 of the herbicide, chlorophyll a and b contents of this susceptible plant decreased, progressing from the youngest to the more mature leaves. Newly formed tillers and the youngest expanding leaves exhibited a more severe type of chlorosis and were often found to be devoid of chlorophyll. A similar progressive decline of the chlorophyll content was observed in an experiment where leaf segments were floated in fluazifop-butyl. Evidence of a rapid and significant alteration of the normal chlorophyll fluorescence of E. repens leaves treated with fluazifopbutyl was obtained. The herbicide, at a concentration range of 0.25–1.0 μg μ1^?1, caused a significant loss of the fast fluorescence rise, fluorescence yield and, after 24 h, caused a total abolition of the fluorescence decay (PS decas). These results are discussed. Ultrastructural damage to chloroplasts was seen within 24 h after treatment with fluazifop-butyl. This damage ranged from a partial to total disruption of the outer chloroplast envelope and a disorganization of the internal thylakoid system. Such Ultrastructural effects on chloroplasts were found to intensify up to about 6–7 days after spraying, by which time nearly all chloroplasts in tissue sections were affected to some degree.     

Comparison of physiological effects of fluazifop-butyl and sethoxydim on oat (Avena sativa L.)

Laboratory experiments were conducted to compare the physiological effects of two herbicides: fluazifop-butyl {butyl ( RS )-2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy]-propionate} and sethoxydim {(±)-2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} on oat ( Avena sativa L. cv. Zenshin). The herbicides strongly inhibited growth of oat and induced chlorosis at the basal part of shoots and ethylene production from the seedlings. The phytotoxicity of these herbicides in oat seedlings was alleviated by 2,4-D (2,4-dichlorophenoxyacetic acid), but not by IAA (indole-3-acetic acid). Coleoptile elongation induced by 2,4-D or IAA was inhibited by fluazifop-butyl and sethoxydim, suggesting both herbicides possess the activity to inhibit this auxin action. Fluazifop (free acid) and sethoxydim inhibited proton excretion from oat roots but fluazifop-butyl did not. This proton excretion was not restored by 2,4-D or IAA. Furthermore, cellular electrolyte leakage in oat shoots was increased by both herbicides, indicating that the membrane permeability was increased. We conclude that fluazifop-butyl and sethoxydim may have the same mechanism of action which leads to disruption of membrane integrity, although fluazifop-butyl acts as a free acid after hydrolysis (fluazifop).     

Potential safeners for protecting sorghum (Sorghum bicolor (L.) Moench) against chlorsulfuron,fluazifop-butyl and sethoxydim*

In greenhouse studies, the efficacy of the herbicide safeners NA(1,8-naphthalic anhydride), R-25788 (N,N-diallyl-2,2-dichloroacetamide), cyometrinil and CGA-92194 [N-(1,3-dioxolan-2-yl-methoxy)imino-benzeneaceto-nitrile] in protecting grain sorghum (Sorghum bicolor (L.) Moench, cv. ‘Funk G623’) against injury from pre-emergence or early post-emergence applications of the herbicides chlorsulfuron, fluazifop-butyl and sethoxydim was examined. NA as a seed dressing at 0·5 or 1·0% (w/w) was the most effective of the four safeners and offered partial to good protection to sorghum against injury from the lower rates of pre-emergence applications of all three herbicides. R-25788 was totally ineffective as a sorghum protectant against fluazifop-butyl injury but it did antagonize partially the injurious effects of the lower rates of sethoxydim and chlorsulfuron on sorghum. Cyometrinil and CGA-92194 offered partial protection to sorghum against injury from the lowest rate of all herbicides but their efficacy against higher rates of the three herbicides was very limited. None of the four safeners was effective in protecting grain sorghum against injury from post-emergence applications of the three herbicides tested.     

Influence of light, temperature and humidity on the translocation and activity of glyphosate in Elymus repens (=Agropyron repens)

The effects of light, température and humidity on the performance and translocation of glyphosate in Elymus repens (L.) Gould (=Agropyron repens L. (Beauv.)), during the period of 48 h after treatment, were studied in controlled-environment cabinets. Increases in the levels of all three factors resulted in increases in herbicide performance. In general, these differences were statistically significant at all treatment periods except the longest when almost full control was achieved. The results highlight the important influence of environmental factors on herbicide performance during the short-term, post-spraying period. The application of ¹⁴C-labelled glyphosate to the adaxial leaf-sheath surface resulted in very rapid uptake and was used as a method of treating plants to study herbicide translocation under different environmental conditions. Increased light levels and temperatures enhanced basipetal translocation to the crowns and rhizomes but increased humidity had no significant effect with this form of application.     

Effects of ethephon pre-treatment on the response of Elymus repens to fluazifop-butyl

Growth inhibition of pot-grown Elymus repens (L.) Gould by fluazifop-butyl was occasionally enhanced by pre-treatment with ethephon. Studies with ¹⁴C-labelled fluazifop-butyl showed that ethephon increased the accumulation of ¹⁴C in basal buds and proximal parts of the rhizome system. This potential modification in the distribution of fluazifop-butyl within E. repens rhizomes may have reduced regeneration and recovery of the E. repens, particularly from the basal buds, although there was no increase in the proportion of ¹⁴C translocated into the rhizome. Also, ethephon not only activated the sinks in the rhizome but in the foliage of E. repens as well, and could initiate buds without sinks. The effects of ethephon on fluazifop-butyl phototoxicity were irregular in their occurrence and degree, and possible reasons for this are discussed. Effets depré-traitements à I'étéphon sur la réponse de Elymus repens au fluazifop-butyl Lors d'expériences en pots, des pré-traitements & 1'étéphon augmentaient occasionnellement 1'inhibition de croissance d'Elymus repens (L.) Gould traité au fluazifop-butyl. Des etudes avec du fluazifop-butyl marqué au ¹⁴C ont montré que l'éléphon augmentait l'accumulation de ¹⁴Cdans les bourgeons de la base et dans les parties proximales des rhizomes. Bien que la proportion de ¹⁴C transportée dans le rhizome ne soit pas accrue, cette modification de la distribution du fluazifop-butyl à l'intérieur des rhizomes d'E. repens pourrait limiter la régénération et la reprise de croissance, en particulier à partir des bourgeons de la base. En outre, l'étéphon activait des puits métaboliques non seulement dans le rhizome mais aussi dans le feuillage d'E. repens et pouvait initier des bourgeons qui ne se comportaient pas comme des puits métaboliques. Tant 1'existence que 1'intensité des effets de 1'étéphon sur la phytotoxicité du fluazifop-butyl étaient irréguliers et les raisons possibles en sont discutées. Wirkung einer Vorbehandlung mit Ethephon auf die Reaktion von Elymus repens (L.) Gould auf Fluazifop-butyl In Gewächshausversuchen war die Wuchshem-mung von Elymus repens durch Fluazifop-butyl gelegentlich durch eine Vorbehandlung mil Ethephon verstärkt. Untersuchungen mil ¹⁴C-Fluazifop-butyl ergaben, daß Ethephon die Ak-kumulation von ¹⁴C in basalen Knospen und proximalen Teilen des Rhizoms förderte. Die so mögliche Veränderung der Verteilung von Fluazifop-butyl in den Quecke-Rhizomen kann zu der reduzierten Regeneration der Pflanzen geführt haben, vor allem aus den basalen Knospen, obwohl insgesamt keine groBere ¹⁴C-Menge im Rhizom gefunden wurde. Ethephon aktivierte nicht nur die Sinks im Rhizom, son-dern auch in den oberirdischen Teilen und kon-nte zur Ausbildung von Knospen ohne Sinks führen. Die Wirkungen des Ethephons auf die herbizide Wirkung des Fluazifop-butyls war unregelmaßig, und die moglichen Grunde dafiir werden diskutiert.     

检疫性杂草匍匐矢车菊的学名考证

匍匐矢车菊为我国进境植物检疫性有害生物,其中文名、英文名及拉丁学名在与其相关的研究及文献中存在不同程度的混乱,为了避免引起不必要的误解,经过对匍匐矢车菊的原始文献和其他相关文献的分析和考证,在植物保护及植物检疫领域,中文名建议采用顶羽菊,英文名建议采用Russian knapweed,拉丁学名建议采用Acroptilon repens(L.)DC.,以便于学术交流和统一调查防除。     

The effect of temperature and nitrogen level on the morphology of Agropyron repens (L.) Beauv.

The effects of temperature and nitrogen level on the morphology of Agropyron repens (L.) Beauv. were investigated in a factorial experiment involving three temperatures (10°, 15° and 20°C) and three nitrogen levels (15, 120 and 960 ppm N). The main effects on axillary bud outgrowth were found at 15 ppm N and 10°C. At 15 ppm N there was an increase in the frequency of dormant buds in the axils of the coleoptile and leaf 3, and a tendency for the buds in the axils of leaves 1 and 2 to produce rhizomes or rhizome-tillers instead of tillers. At 10°C there was a high proportion of dormant buds in the colcoptile axil but all buds in higher axils grew out. Both 15 ppm N and 10°C led to the production of relatively fewer secondary rhizomes and tillers. Maximum leaf length was attained at 20°C/120 ppm N, when leaves were 40–50% longer than those at 10°C/15 ppm N. Nitrogen level had little effect on total stem height, but at all nitrogen levels stem height and the height of individual internodes increased with increasing temperature. The size of the shoot apex and the number of leaf primordia borne on it increased with decreasing temperature and increasing nitrogen level. Effets de la temperature et du niveau d'azote sur la morphologie de l'Agropyron repens (L) Beauv. Les effets de la témperature et du niveau d'azote sur la morphologie de l'Agropyron repens (L.) Beauv. ont étéétudiés dans une expérience factorielle mettant en jeu trois températures (10°, 15° et 20° C) et trois niveaux d'azote (15, 120 et 960 ppm). L'effet principal sur l'éclosion du bourgeon axillaire a été observéà 15 ppm d'azote et 10° C. A 15 ppm d'azote, il y a eu un accroissement de la fréquence des bourgeons dormants aux aisselles du coleoptile, et de la feuille 3, et une tendance pour les bourgeons aux aisselles des feuilles 1 et 2 à produire des rhizomes ou des tallesrhizomes au lieu de talles. A 10° C il y a eu une proportion élevée de bourgeons dormants à l'aisselle du coléoptile, mais tous les bourgeons des aisselles plus élevées sc sont dévetoppés. 15 ppm d'azolc et 10° C ont provoqué une production reiativement plus faible de rhizomes secondaires et de talles. La longueur maximale des feuilles a été atteinte a 20° C et 120 ppm d'azote, lorsque les feuilles furent 40 à 50% plus longues que celles obtenues a 10° C et 15 ppni d'azote. Le niveau d'azote a eu peu d'influence sur la hauteur totale de la tige, mais, à tous les niveaux d'azote, la hauteur de la tige et celle des internoeuds individuets a augments avec la temperature. La taille de l'apex des pousses et le nombre d'ébauches de feuilles apparaissant dessus a augmentéà mesure que la température diminuait et que s'accroissait le niveau d'azote. Die Wirkung von Temperatur und Stickstoffversorgung auf die Morphologie von Agropyron repens (L.) Beauv. In einem mehrfaktoriellen Versuch wurde der Einfluβ von Temperatur (10, 15 and 20°C) und Stickstoffgaben (15, 120 und 960 ppm N) auf die Morphologie von Agropyron repens (L.) Beauv. untcrsucht. Die Hauptwirkung auf den Austrieb der Achselknospen wurde bei 15 ppm N und 10°C beobachtet. Bei 15 ppm N war eine Zunahme in der Häufigkeit dormanter Knospen in der Koleoptilenachsel und der Achsel des dritten Blattes zu verzeichnen. Weiterhin bestand die Tendenz, daβ die Knospen in den Blattacbseln des 1. und des 2. Blattes Rhizome oder Rhizom-Bestockungstriebe siatt Bestockungstriebe bildelen. Bei 10°C war ein groβer Anteil dormanter Knospen in der Koleoptilachsel vorhanden; aber alle Knospen der höheren Achseln trieben aus. 15 ppm N, als auch 10°C bewirkten die Bildung von relaliv wenigen sekundären Rhizomen und Bestockungstrieben. Maximale Blattiängen wurden bei 20°C/120 ppm N erhalten. Hierbei waren die Blätter um 40–50% Iänger als bei 10°C/15 ppm N. Der Slickstoffgehalt hatte nur eine geringe Wirkung auf die gesamte Sproβhöhe, aber bei alien Stickstoffgehaiten nahm die Sproβhöhe und die Länge der Internodien mit steigender Temperatur zu. Das Ausmaβ der Sproβspitze und die Zahl der Blattaniagen nahm mit abnehmender Temperatur und steigender Stickstoffversorgung zu.     

Physiological effects of buthidazole on Zea mays L., Amaratithus retroflexus L., Medicago sativa L. and Agropyron repens(L.) Beauv.*

Buthidazole (3-[5-(1,1-dimethylethyl)-1,3.4-thiadiazol-2-yl]-4-hydroxy-l-methyl-2-imidazolidinone) at concentrations of 10^?6-10^?4M did not affect germination of corn (Zea mays L.,‘Pioneer 3780’), redroot pigweed (Amaranlhus retroflexus L.), alfalfa (Medicago saliva L., ‘Vernal’), and quackgrass (Agropyron repens(L.) Beauv.) seeds. Stressing the seeds obtained from mature corn plants treated either pre-emergence or pre- plant incorporated with buthidazole at several rates by accelerated ageing and cold treatments further indicated that this herbicide did not affect germination. Total photosynthesis and dark respiration of corn plants 12 days after pre-emergence application and of redroot pigweed, alfalfa, and quackgrass plants after postemergence application of buthidazole at several rates were measured with an infrared CO₂ analyser. The results suggested that buthidazole was a rapid inhibitor of photosynthesis of the sensitive redroot pigweed and quackgrass plants, with less effect on corn and alfalfa. Buthidazole did not affect respiration of the examined species except for a transitory increase in corn and alfalfa 12 days after pre-emergence or 4 h after postemergence treatment with buthidazole at 0.56 or 1.12 and 2.24 kg/ha, respectively. A long-term inhibition of quackgrass respiration 96 h after treatment with buthidazole at 1.12 and 224 kg/ha was also evident.     

Interval between sequential applications of asulam for regrowth control of torpedograss (Panicum repens L.)

Two field experiments each conducted during a 1 year period at the Agricultural Experiment Farm, University of the Ryukyus, Japan evaluated the interval needed between sequential applications of asulam (3 kg ai ha⁻¹) for successful control of torpedograss ( Panicum repens L.). Regrowth of torpedograss from rhizomes was lowest when asulam was applied at 40-day intervals. Application at intervals of 70 days or longer completely controlled above-ground shoots but not regrowth from rhizomes. Above-ground biomass of torpedograss regrowth was 7- and 49-fold higher when asulam was applied at 70 and 100 day intervals, respectively, compared with 40-day intervals. Asulam applied three times at 40-day intervals starting 40 days after land preparation provided almost total torpedograss control 1 year after the initial application.     

Fate of glyphosate in Agropyron repens (L.) Beauv. growing under low temperature conditions

Absorption, translocation and distribution of ¹⁴C-glyphosate were examined in Agropyron repens (L.) Beauv. plants growing under field conditions in the autumn. Glyphosate absorption did not increase beyond 3 days after application, whereas translocation to the rhizomes continued up to 7 days after application. The translocated glyphosate accumulated more in new rhizomes than in older parts of the rhizomes. Ten per cent of the glyphosate translocated out of the treated shoot was recovered in younger shoots 7 days after application. Plants harvested the following spring contained less than 20% of the glyphosate originally applied. Although a growth cabinet experiment indicated that 34% of the glyphosate in the rhizomes of treated plants could be remobi-lized into new aerial shoots, considerably less was recovered in new, aerial shoots in the spring in the field-grown plants. Freezing experiments showed that glyphosate translocation to the rhizomes was only prevented when cold treatment caused visible damage to A. repens foliage.     

Influence of plant age on the allelopathic potential of nodding thistle (Carduus nutans L.) against pasture grasses and legumes

The allelopathic influence of four developmental stages of nodding thistle (small rosette, large rosette, bolting and dead plants) on eleven test species (six grasses, four legumes and itself) was investigated using aqueous extract bioassays, aqueous leachate bioassays, and bioassays based on addition of ground material to soil. The aqueous extract and leachate bioassays indicated that nodding thistle was most allelopathic at the rosette stages, while the bioassays involving amendment of soil with thistle tissue showed bolting live and dead plants to be the most allelopathic. It is proposed that nodding thistle is allelopathic at two phases of its development, i.e. at the early bolting stage when the larger rosette leaves are decomposing and releasing soluble inhibitors, and at the stage when bolting plants are dying and releasing insoluble inhibitors. Nodding thistle seedlings appear to be stimulated by addition of thistle tissues to soil, indicating that thistle plants may weaken pasture and simultaneously encourage recruitment of its own species. This is consistent with previous studies detecting high densities of thistle seedlings in the vicinity of deceased parent plants. The six grass species were generally more tolerant to thistle allelopathic effects than were the four legume species, but no consistent differences emerged between different grass or legume species. Influence de l'age de la plante sur le potentiel allélopathique du chardon penche (Carduus nutans L.) vis a vis des prairies de graminées et de légumineuses L'influence allélopathique de 4 stades de développement du chardon penché (petite rosette, grande rosette, montaison, plantes mortes) sur 11 espèces tests (6 graminées, 4 légumineuses et lui-même) a étéétudiée en utilisant des bioessais d'extraction acqueuse, des bioessais de lessivage acqueux et des bioessais fondés sur l'addition au sol d'amendement. Les bioessais d'extraction acqueuse et de lessivage ont montré que le chardon penchéétait plus allélopathique au stade rosette tandis que les bioessais impliquant l'amendement de sol avec des tissues de chardon ont montré que la montaison et les plantes mortes étaient les plus allélopathiques. Il est proposé que le chardon penché est allélopathique à 2 phases de son développement, par exemple au stade montaison précoce quand les plus grandes feuilles de la rosette se décomposent et relachent les inhibiteurs solubles, et au stade où les plantes montées meurent et relächent les inhibiteurs insolubles. Les plantules de chardon penché apparaissent être stimulées par l'addition de tissus de chardon au sol, montrant que les plantes de chardon peuvent affaiblir une prairie et simultanément favoriser sa propre réimplantation. Ceci est conforme avec des études précédentes montrant des fortes densités de plantules de chardon au voisinage de plantes parentes mortes. Les 6 espèces de graminées ont été de façon générale plus tolérantes aux effets allélopathiques que les 4 espèces de légumineuses, mais aucune différence importante ne s'est exprimée entre les différentes espèces de graminées ou de légumineuses. Einfluβ des Pflanzenalters der Nickenden Distel (Carduus nutans L.) auf die allelopathische Wirkung gegen Weidegräser und Leguminosen Die allelopathische Wirkung der Nickenden Distel wurde in 4 Entwicklungsstadien (in kleiner und in voller Rosette, blütentreibend und abgestorben) gegen 11 Pflanzenarten (6 Gräser, 5 Leguminosen und sich selbst) mit wäßrigen Auszügen, Perkolationswasser und Bodenmaterial zum Substrat geprüft. Mit den wäßrigen Auszügen und dem Perkolationswasser zeigte sich die Nickende Distel im Rosetten-Stadium am meisten allelopathisch, während Bodenmaterial mit Resten blütentreibender und abgestorbener Pflanzen wirksamer war. Es kann angenommen werden, daß die Nickende Distel in 2 Entwicklung sphasen allelopathisch wirkt, nämlich wenn die größeren Rosettenblätter oder wenn die blütentreibenden Pflanzen vergeben und 1ösliche Hemmstoffe entlassen. Keimpflanzen der Nickenden Distel werden offensichtlich durch Pflanzenmaterial der Distel im Wachstum angeregt; die Distel schwächt also Weide-Pflanzenarten und fördert zugleich ihre eigene Entwicklung. Dieser Befund deckt sich mit der Beobachtung hoher Keimpflanzen-Dichten um abgestorbenen Mutterpflanzen. Die 6 Gräser waren durchweg gegenüber der allelopathischen Wirkung der Distel unempfindlicher als die 4 Leguminosen, doch innerhalb dieser Gruppen zeigten sich keine klaren Unterschiede.     

Effect of nitrogen fertilizer application on growth, biomass production and N-uptake of torpedograss (Panicum repens L.)

A glasshouse study was conducted to evaluate the effects of different rates (0, 50, 100, 200 and 400 kg ha^?1) of nitrogen (N) fertilizer application on the growth, biomass production and N‐uptake efficiency of torpedograss. The growth responses of torpedograss to the N application were significant throughout the observation periods. Torpedograss grown for 60 days obtained the highest total biomass of 23.0 g plant^?1 with an application of 200 kg ha^?1 N, followed by 20.4 g plant^?1 with an application of 100 kg ha^?1 N; when it was grown for 90 days a significantly higher biomass of 102.3–106.0 g plant^?1 was obtained with the 200–400 kg ha^?1 N than the biomass (68.0 g plant^?1) obtained with the fertilizer applied at a lower rate. When the torpedograss was grown for 130 days the highest biomass was 230.0 g plant^?1 with the 400 kg ha^?1 N application, followed by a biomass of 150.0 g plant^?1 with the 200 kg ha^?1 N application, but the above‐ground shoot in all treatments was over mature for animal food. The ratio of the above‐ground shoot to the underground part increased with the increase in N application up to 400 kg ha^?1 during the 90 days after planting (DAP), but the above‐ground shoot biomass was the same with the 200 and 400 kg ha^?1 N. The agronomic efficiency of the N application decreased to 5–38 with the increase in N application to 400 kg ha^?1, which was less than half the agronomic efficiency with the 200 kg ha^?1 N. The agronomic efficiency of N was very low (5–22) during the 60 DAP, which indicated that the N application would not be economically viable in this period for torpedograss as a pasture, and short‐duration plants could be cultivated in torpedograss‐infested fields to minimize weed‐crop competition. The nitrogen concentration (%) in the torpedograss increased with the increase in N application, but N‐uptake efficiency was the opposite and the value was very low with the 400 kg ha^?1 N. The above results lead us to conclude that the N application rate of 200 kg ha^?1 is the most effective for torpedograss growth.     

Some effects of manual and chemical defoliation on the growth and carbohydrate reserves of Panicum repens (L.) Beauv.

In pot experiments on Panicum repens manual and chemical defoliation at intervals of 2–6 weeks decreased the growth of shoots, roots and new rhizomes and reduced the carbohydrate reserves. The most frequent manual defoliation did not completely suppress growth even when continued for 9 months. The plants were killed, however, by application of paraquat at doses of 0–14-0′56 kg/ha every 2 weeks for a period of 3 months. It is suggested that repeated mechanical defoliation may help to reduce plant vigour and limit the rate of spread in the field and that it may be possible to develop a method of more permanent control based on repeated application of paraquat. Quelques effets de la ddfoliation manuelle et chimique sur la croissance el les reserves en hydrates de carbone de Panicum repens (L.) Beauv. Dans des expériences en pots sur Panicum repens, des défoliations manuelles et chimiques effectuées à des inter-valles de 2 à 6 semaines ont diminué la croissance de la partie aérienne, des racines, et des nouveaux rhizomes et ont réduit les réserves en hydrates de carbone. Dans la plupart des cas, Ia défoliation manuelle n'a pas complétement supprimé la croissance, mêmc lorsquété a ete poursuivie pendant 9 mois. Toutefois, les plantes ont été tuées par une application de paraquat à des doses de 0,14 à 0,56 kg/ha, toutes les deux semaines pendant une pédode de 3 mois. Ceci suggére que les défoliations mécaniques répétées peuvent contribuer à la réduction de la vigueur de la plante et à la limitation du taux d'infestation au champ, ce qui rendrait possible l'établissement d'une méthode de lutte plus définitive, basée sur des applications répétées de araquat. Einige Auswirkungen von mechanischer und chemischer Blattabtötung auf das Wachstum und die Kohlehydratreserven von Panicum repens (L.) Beauv. Bei Topfversuchen mit Panicum repens verminderte mechanische und chemische Blattabtötung in AbstSaUden von 2–6 Wochen das Wachstum von Spross, Wurzel und neuen Rhizomen. Ebenso wurden die Kohlehydratreserven herabgesetzt. Die in Abstönden von zwei Wochen durchgeführte mechanische Blattabtötung führte auch nach neun Monaten nicht zu einer vollständigen Unterdrückung des Wachstums. Jedoch wurden die Pftanzen durch Paraquat abgetötet wenn dieses in zweiwöchigem Abstand drei Monate hin-durch in Aufwandmengen von 0.14–0.56 kg/ha angewandt wurde. Es wird angenommen, dass wiederholte mechanische Blattabtötung dazu beilrägt, die Widerstandsfähigkeit der Pflanzen zu vermindern und die Ausbreitung im Feld zu begrenzen, Es wird der Hoffnung Ausdruck gegeben, dass es möglich sein wird, eine Methode fur länger anhaltende Bekämpfung auf der Grundlage von wiederholt ausge-brachtem Paiaquat zu entwickeln.