Antagonistic effects of 2, 4-D), MCPA and MCPB on uptake and translocation of haloxyfop-ethoxyethyl in oat (Avena sativa L.)

The antagonism of haloxyfop-ethoxyethyl (HE) by selected phenoxy herbicides was evaluated through studies of the foliar absorption and translocation of ¹⁴C]HE in oat (Avena sativa L.). Uptake of [¹⁴C]HE, from simultaneous application in mixture with a phenoxy herbicide, was inhibited by the latter in the order MCPB MCPA2,4-D. In mixtures, the foliar absorption of [¹⁴C]HE was reduced more by salts of the phenoxy herbicides than by the corresponding butyl esters. 2,4-D-butyl enhanced uptake of [¹⁴C]HE. The application rate of phenoxy herbicides (from 0.5 to 1.5 kg a.e. ha^?1) did not affect the uptake of [¹⁴]HE, but did influence translocation. Movement of [¹⁴C]herbicide out of the treated leaf was less than 5% of the total ¹⁴C applied; translocation was significantly reduced by all phenoxy herbicides and was antagonized most by 2,4-D-salt and least by MCPB-butyl. Phenoxy salts invariably reduced [¹⁴C]HE translocation more than the corresponding butyl esters. Prior application of phenoxy salts reduced uptake of [¹⁴C]HE, but this antagonism was reduced as the time interval between spray applications increased. Translocation of ¹⁴C out of the treated leaf was antagonized most by prior application of 2,4-D, and by phenoxy salt formulations. When applied up to 2 days after HE, phenoxy salts reduced uptake, but translocation of ¹⁴C was generally unaffected. Les effets antagonistes du 2,4-D, du MCPA et du MCPB sur la pénétration et la migration de l'haloxyfop-éthoxyéthyl dans l'avoine (Avena sativa L.) L'effet antagoniste de plusieurs herbicides de type phénoxy à l'égard de l'haloxyfopéthoxyéthyl (HE) a étéétudié dans des études de pénétration foliaire et de migration du [¹⁴C]HE chez l'avoine (Avena sativa L.) Lorsqu'il est appliqué en mélange avec un herbicide phénoxy, la pénétration du [¹⁴C]HE est inhibée dans l'ordre suivant: MCPB MCPA 2,4-D. La pénétration foliaire du [¹⁴C]HE était davantage réduite par les sels d'herbicides phénoxys que par les esters butyles correspondants. Le 2,4-D butyle augmentait la pénétration du [¹⁴C]HE. La dose d'herbicides phénoxys (de 0,5 à 1,5 kg m.a. ha^?1) n'affectait pas la pénétration de [¹⁴C]HE mais modifiait sa migration. La migration d'herbicide ¹⁴C hors de la feuille traitée était inférieure à 5 % de la radioactivité appliquée. Elle était significativement réduite par tous les herbicides phénoxys, le plus par le sel de 2,4-D et le moins par le MCPB-butyle. Les phénoxys sous forme de sels diminuaient toujours la migration du [¹⁴C]HE davantage que les esters butyles correspondants. Si l'application de phénoxys sous forme de sel précédait celle de [¹⁴C]HE, sa pénétration était réduite mais cet antagonisme était réduit lorsque l'intervalle de temps entre les deux applications était augmenté. La migration de ¹⁴C hors de la feuille traitée était le plus diminuée par le 2,4-D et par les phénoxys sous forme de sels. Quand ils étaient appliqués jusqu'à deux jours après [¹⁴C]HE, les phénoxys sous forme de sel réduisaient sa pénétration, mais la migration de ¹⁴C n'était généralement pas affectée. Antagonistische Wirkung von 2,4-D, MCPA und MCPB auf die Aufnahme und Translokation von Haloxyfop-ethoxyethyl in Hafer (Avena sativa L.) Die antagonistische Beeinflussung von Haloxyfop-ethoxyethyl (HE) durch ausgewählte Phenoxy-Herbizide wurde anhand der Blattaufnahme und Translokation von [¹⁴C]HE in Hafer (Avena sativa L.) untersucht. Die Aufnahme von [¹⁴C]HE bei gleichzeitiger Anwendung in Mischung mit einem Phenoxy-Herbizid wurde durch die letztgenannten Stoffe in der Reihenfolge MCPB MCPA 2,4-D gehemmt, wobei die Salz-Verbindungen stärker wirkten als die entsprechenden Butylester. 2,4-D-butyl förderte die Aufnahme von [¹⁴C]HE. Die Aufwandmenge der Phenoxy-Herbizide (0,5 bis 1,5 kg AS ha^?1) blieb ohne Einflus auf die Aufnahme von [¹⁴C]HE, beeinflußte aber die Translokation. Aus den behandelten Blättern wurde weniger als 5 % der gesamten [¹⁴C]Menge transloziert; die Translokation wurde durch alle PhenoxyHerbizide signifikant reduziert, am meisten durch 2,4-D-Salz, am wenigsten durch MCPB-butyl. Die Salz-Verbindungen verminderten die [¹⁴C]HE-Translokation mehr als die entsprechenden Butylester. Eine vorausgehende Behandlung mit den Salz-Verbindungen senkte die Aufnahme von [¹⁴C]HE, aber mit zunehmender Zeit zwischen den Anwendungen nahm dieser Antagonis mus ab. Hierbei war der Einfluß von 2,4-D und von den Salz-Verbindungen am stärksten. Wurden diese Stoffe bis zu 2 Tagen nach HE ausgebracht, beeinträchtigten sie die Aufnahme, jedoch im allgemeinen nicht die Translokation von ¹⁴C.     

Joint action of sulfonylurea herbicides and MCPA

The joint action of mixtures of the sulfonylurea herbicides chlorsulfuron, metsulfuron and tribenuron and MCPA as a dimethylamine salt was assessed on Stellaria media L. and Lamium purpureum L. Two statistical analyses, and appropriate experimental designs, were used—the additive dose model (ADM) and the principle of parallel dose-response curves. The ADM analyses revealed that mixtures of the sulfony-lureas and MCPA were less potent than expected on Stellaria while the parallel-line assay analyses showed that activity of the sulfonylurea herbicides on Stellaria and Lamium was reduced in mixtures with MCPA. The antagonism was found to be dependent on the ratio of the two herbicides. Activity decreased with increasing MCPA ratios in the mixtures. Sequential spraying and selective placement of droplets revealed that MCPA only antagonized the sulfonylureas when the herbicides were in physical contact with each other. The benefits of applying both statistical methods when studying the joint action of two herbicides both possessing activity on the test plants are discussed. Action de melanges d'herbicides sulfonylurées et de MCPA L'action de melanges des herbicides sulfonylurées chlorsulfuron, metsulfuron et tribénuron avec le MCPA formulé en sel de diméthylamine, a été etudiée sur Stellaria media L. et Lamium purpureum L. Deux analyses statistiques asso-ciées a deux systèmes expérimentaux appropriés ont été utilisés: le modèle à doses additives (ADM) et le principe du parallélisme des cour-bes dose-effet. Les analyses ADM ont montré que les melanges de sulfonylurées et de MCPA ont été rnoins efficaces qu'attendu sur Stellaria. Les analyses en courbes parallèles ont montré que 1'activité des herbicides sulfonylurées sur Stellaria et Lamium était réduite dans des mélanges avec le MCPA.L'antagonisme dépendait du rapport entre les doses des deux herbicides, 1'activité décroissant avec 1'augmentation du taux de MCPA. Des traitements séquentiels et des dépôts localisés de gouttelettes ont montré que le MCPA n'était an-tagoniste des sulfonylurées que lorsque les herbicides étaient physiquement en contact. L'intérêt est discuté, d'utiliser les deux méthodes statistiques de concert pour étudier les interactions entre deux herbicides actifs sur les plantes test. Gemeinsame Wirkung von Sulfonylharnstoff-Herbiziden und MCPA Die Wirksamkeit von Mischungen der Sulfonyl-hamstoff-Herbizide Chlorsulfuron, Metsulfuron und Tribenuron mil MCPA als Dimethylamin-salz wurde an Stellaria media L. und Lamium purpureum L. bestimmt. Die Versuche wurden so angelegt, um 2 statistische Analysen anzuwen-den: das Additiv-Dosis-Modell (ADM) und das Prinzip paralleler Dosis-Wirkungs-Kurven. Die ADM-Analyse ergab, daß diese Mischungen gegenüber Stellaria weniger wirksam als erwartet waren, während die Parallel-Analyse zeigte, daß die Wirksamkeit der Sulfonylharnstoff-Herbiz-ide in Mischungen mil MCPA gegeniiber den beiden Arten herabgesetzt war. Es ergab sich, daß der Antagonismus vom Verhältnis der Mischungspartner abhängt. Die Wirkung nahm mit steigenden MCPA-Anteilen in den Mischungen ab. In Spritzfolgen und bei separater Applikation zeigte sich, daß MCPA nur dann gegenüber Sulfonylharnstoffe antagonistisch wirkte, wenn sich die Herbizide vermischten. Die Vorzüge der Anwendung der beiden statistischen Methoden zur Untersuchung des gemeinsamen Effektes von 2 Herbiziden ähnlicher Wirkung werden diskutiert.     

磺酰脲类除草剂加二甲四氯的除草效果

江苏省淮安市楚州区麦田杂草种类繁多 ,主要为禾本科杂草及阔叶杂草。阔叶杂草主要有猪殃殃、荠菜、牛繁缕、大巢菜等。前几年小麦田阔叶杂草的化学防除主要以冬前使用氯磺隆和甲磺隆 ,春后使用施甲合剂 ,防除效果比较理想。但随着氯磺隆和甲磺隆的限制使用 ,冬前的化除有一定难度。近年来除氯磺隆和甲磺隆以外的其它磺酰脲类除草剂如苄磺隆、噻磺隆、苯磺隆等防除麦田阔叶草具有较明显的防治效果 ,也比较经济 ,但防效表现慢 ,对大巢菜效果较差。为了筛选冬后麦田防除阔叶杂草高效、安全、经济的除草剂配方 ,我们进行了本试验1　材料与方法1…     

Effect of MCPA and MCPB on 32P accumulation and its incorporation into ATP in Vicia faba L.

Treatment of excised bean root tissue with MCPA and MCPB resulted in a reduced uptake and incorporation of ³²P into ATP accompanied by enhanced or reduced respiration. In all cases MCPB was found to be more toxic than MCPA. These results are explained on the basis that ATP is the energy source for phosphate uptake and that a reduction in ATP synthesis with MCPA and MCPB results in lowered phosphate uptake.     

Metabolism and selectivity of rice herbicides in plants

Chemical weed control with effective and highly active herbicides has been very useful and convenient means. It has contributed to stable crop production and is labor saving. Recent herbicides have had characteristics such as high effectiveness without causing environmental pollution or harmful effects, and appropriate herbicides having high activity, low toxicity, high selectivity and being non-persistent have been developed. The metabolism of rice herbicides used mainly in Japan, such as sulfonylurea, chloroacetamide, acylamide, urea, thiocarbamate, pyrazole, triazine, diphenyl ether, phthalimide, phenoxy, aryloxyphenoxypropionate, etc., is reviewed, and its involvement in selectivity is also discussed. The metabolism of herbicides is closely related to their activity and selectivity. Differential herbicide metabolism in plants is a contributing factor of selectivity between crops and weeds. Chemicals that are more detoxified in crops and/or more activated or less detoxified in weeds are considered as being effective and selective herbicides. The metabolism of various types of rice herbicides includes: oxidative reaction (ring and chain hydroxylation, O - and N -dealkylation), hydrolysis and subsequent glucose conjugation, and glutathione conjugation in rice. These detoxicative activities are much higher in rice than weeds in paddies, and this leads to the selectivity of herbicides. Enzymes, oxidase, P-450 mono-oxygenase, esterase, acylamidase, glucosyl transferase, glutathione transferase, etc., play important roles in herbicide metabolism and selectivity.     

Soil persistence studies with [14C]MCPA in combination with other herbicides and pesticides

The persistence of [¹⁴C]MCPA at a rate equivalent to 1 kg ha^?1 was studied under laboratory conditions in a clay loam, heavy clay and sandy loam at 85% of field capacity moisture and 20±1°C both alone and in the presence of tri-allate, trifluralin, tri-allate and trifluralin, malathion, Vitaflow DB, malathion and Vitaflow DB, bromoxynil, bromoxynil and asulam, bromoxynil and difenzoquat, dicamba, dicamba and mecoprop, linuron, MCPB, metribuzin, propanil, TCA, benzoylprop-ethyl, diclofop-methyl, and flamprop-methyl. Except in the soils treated with asulam, the half-lives of [¹⁴C]MCPA in all three soil types were similar, being approximately 13±1 days, thus indicating that none of the other chemicals studied adversely affected the soil degradation of MCPA. In the asulam treated soils, the half-lives of the MCPA were about 3 days longer than in non-asulam treated soils; the effect was most marked in the clay loam.     

Mode of action,crop selectivity,and soil relations of the sulfonylurea herbicides

The sulfonylurea herbicides are characterized by broad-spectrum weed control at very low use rates (c. 2–75 g ha^?1), good crop selectivity, and very low acute and chronic animal toxicity. This class of herbicides acts through inhibition of acetolactate synthase (EC 4.1.3.18; also known as acetohydroxyacid synthase), thereby blocking the biosynthesis of the branched-chain amino acids valine, leucine and isoleucine. This inhibition leads to the rapid cessation of plant cell division and growth. Crop-selective sulfonylurea herbicides have been commercialized for use in wheat, barley, rice, corn, soybeans and oilseed rape, with additional crop-selective compounds in cotton, potatoes, and sugarbeet having been noted. Crop selectivity results from rapid metabolic inactivation of the herbicide in the tolerant crop. Under growth-room conditions, metabolic half-lives in tolerant crop plants range from 1–5 h, while sensitive plant species metabolize these herbicides much more slowly, with half-lives > 20 h. Pathways by which sulfonylurea herbicides are inactivated among these plants include aryl and aliphatic hydroxylation followed by glucose conjugation, sulfonylurea bridge hydrolysis and sulfonamide bond cleavage, oxidative O-demethylation and direct conjugation with (homo)glutathione. Sulfonylurea herbicides degrade in soil through a combination of bridge hydrolysis and microbial degradation. Hydrolysis is significantly faster under acidic (pH 5) than alkaline (pH 8) conditions, allowing the use of soil pH as a predictor of soil residual activity. Chemical and microbial processes combine to give typical field dissipation half-lives of 1–6 weeks, depending on the soil type, location and compound. Very short residual sulfonylurea herbicides with enhanced susceptibility to hydrolysis (DPX-L5300) and microbial degradation (thifensulfuron-methyl) have been developed.     

Metabolism of some sterol inhibitors in fungi and higher plants,with special reference to the selectivity of fungicidal action

The metabolism of triforine, chloraniformethan, the α-(pyrimidin-5-yl)benzhydryl alcohols (fenarimol, nuarimol and triarimol), the trityl-azoles (fluotrimazole and clotrimazole), and the morpholine types of sterol inhibitors is reviewed; the metabolism of the azolyl-alkane derivatives (mainly triadimefon and triadimenol) is discussed in detail. Redox and hydrolytic reactions are of primary importance. Enzymic inactivation may be one factor influencing fungicide selectivity. Metabolism is the dominant factor of selectivity if it represents the activation process, as with triadimefon. Transformations in higher plants do not differ significantly from those occurring in fungi, except that factors such as the formation of conjugates with natural compounds of plant tissues also play a role, as with triforine and triadimenol. The selectivity of fungitoxic action may be influenced by metabolism both in the host plant and the pathogen.     

The activation of triadimefon and its role in the selectivity of fungicide action

The uptake and metabolism of triadimefon by mycelia of fungi, sensitive or resistant to triadimefon, were studied. In the mycelia the triadimefon content accumulated to 20-40-fold of the external concentration, irrespective of the sensitivity of the fungus. In the course of the metabolism a highly fungitoxic product, triadimenol, was formed. In mycelia of sensitive fungi this transformation was at a high rate whereas it could not be demonstrated or only to a low extent in resistant types. The material produced by the sensitive fungi was effective also against fungi basically resistant to triadimefon. Based on these observations, triadimefon has to be regarded as the precursor of triadimenol. In the species investigated, selectivity may be related mainly to the rate of activation. In higher plants the metabolism of triadimefon showed a similar pattern, but was slower than with fungi. As the transformation into triadimenol (activation) begins thus early in the host tissues, the systemic fungitoxic effect is also influenced by the host plant itself. Regarding the speed of activation differences were found between the four plant species investigated.     

Uptake, translocation, metabolism and selectivity of glyphosate in Canada thistle and leafy spurge

The uptake, translocation and metabolism of glyphosate [N-(phosphonomethyl) glycine] by Canada thistle (Cirsium arvense (L.) Scop.) (susceptible) and leafy spurge (Euphorbia esula (L.)) (resistant) were examined in an attempt to elucidate the nature of the differential sensitivity. The pattern of uptake and translocation was similar in both species. Glyphosate moved readily in the apoplast and the symplast. High humidity and/or surfactant greatly increased the amount of ¹⁴C-glyphosate absorbed and translocated over that in low humidity and/or without surfactant. No ¹⁴Cmetabolites were detected in either species 1 week after treatment with ¹⁴C-glyphosate. More of a glyphosate spray solution containing a fluorescent dye was received and retained on Canada thistle by virtue of its growth habit than on leafy spurge. More glyphosate should therefore be available for uptake by Canada thistle and this may account for the differential sensitivity of these two species.     

Control of Avena fatua and Fagopyrum tataricum with tank mixtures of linuron or linuron + MCPA and sequential applications of linuron, and post-emergence A. fatua herbicides

Linuron (0.21 and 0.28 kg/ha) and linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture with field rates of barban, difenzoquat and flamprop-methyl reduced the phytotoxicity of these herbicides to Avena fatua. When linuron was applied immediately following or 6 days after the A. fatua herbicides no reduction in phytotoxicity to A. fatua occurred, suggesting that the antagonism may be occurring as a result of physical or chemical incompatability when the herbicides are mixed together. The possibility of obtaining broad-spectrum weed control with one trip over the field by applying linuron and one of these wild oat herbicides separately but at the same time using a double-boom, double-tank system deserves evaluation. When linuron was applied in a tank mixture (0.21 and 0.28 kg/ha), immediately after, or 6 days after diclofop-methyl (0.70 kg/ha), there was no reduction of A. fatua control, and wheat tolerance to the tank mixture was good. This tank mixture offers potential for control under field conditions of A. fatua and some broad-leaved weeds in one spray operation. Linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture severely reduced A. fatua control with diclofop-methyl. No loss of phytotoxicity to Fagopyrum tataricum occurred when the A. fatua herbicides tested were tank mixed with linuron or linuron + MCPA. Lutte contre Avena fatua et Fagopyrum tataricum avec des mélanges extemporanés de linuron ou de linuron + MCPA et des applications successives de linuron et d'herbicides de postlevée actifs contre A. fatua     

Spray retention, foliar penetration, translocation and selectivity of asulam in wild oats and flax

Summary: Résumé: Zusammenfassung The spray retention, foliar penetration and translocation of asulam [methyl (4 aminobenzenculphonyl) carbamate] by wild oats (Avena fatua L.) (Susceptible) and flax (Linum usitatissimum L.)(Tolerant) were examined in an attempt to elucidate the nature of differential sensitivity. Wild oat plants retained about four times as much spray solution of a commercial formulation of asulam as did flux. Penetration into flax was much more rapid than into wild oats. Added surfactant and high relative humidity greatly enhanced the penetration of the herbicide into wild oats. An increase in temperature from 10 to 30° C resulted in a large increase in penetration into both species. After foliar application of ¹⁴C-asulam the radioactivity was distributed throughout the wild oat plants. But the translocation in flax was very limited. Here most of it remained in the treated leaf, probably as a result of contact injury caused by the chemical No detectable qualitative or quantitative differences in the metabolism of asulam in the two species were found. Our studies suggest that spray retention, foliar penetration and translocation all play an important role in the selectivity of asulam between wild oats and flax. Rétention'de la pulvérisation, pénélration foliaire, migration el selectivity de I'asulamt chez la folle-avoine et Ie lin La rëtention de la pulvérisation, la pénétration foliaire et la migration de I'asusulame (4 aminobenzënesulfonyl carbamate de méthyle) not étéétudJiees chez la folle avoine (Avfna fatua L.) (sensible)ct chez le lin (Linum usitalissimum L) (resistant) pour tenter d'ëlucider la nature de la difference de scnsibilité. LES plantes de folle-avoine ont retenu quatre fois plus que le lin de la pulvérisation d'une formulation commercial d'asulame. La pénétration dans Ie lin a été beaucoup plus rapide que dans la folle-avoine. L'addition d'un agent de surface et one humidité relative êlevêe ont grandement favorisê la pênetration de I'herbicide dans la folle-avoine one élévation de la temperature de 10 à 30° C a provoqué one import ante augmenta tion de la pênêtration dans les deux espèces. Après one application foliaire d'asulame marqué au ¹⁴C. la radioactivité a été rêpartie dans l'ensemble de la plante chez la folle-avoine. mais la migration chez le lin a êtê três limitêe. La plus grande panie de cette radioactivitê est restêe dans la feuille traitèe. probablement en raison des damages provoquês par le contact duproduit. ll n'a pasêtêdecelê de differences, ni qualitatives. niquantitatives. Dans)le mêtabolisme de l'asulame chez les deux espêces. Nos recherches suggèrent que la retention de la pulvêrisation, la pénétration fotiaire et la migration jouent un röle important dans la sélectivité de l'asulame entre la folle-avoine et le lin. Spritzmitelrterenrntion, Blmprnetlration, Tronslokation and Selekrivitär von Asulam hei Flughafer and Flachs Spritzmittelretention. Blat penetration and Translokation von Asuiam [Methyl-l-aminobenzolsulfonyl)-carbamat] bei Flughafer (Avina fatua L.)empfindlich) and Flachs (Limum usiiaiis imum L.)(tolerant) wurden untersucht mit dem ziel. Aufklärung über die Ursache der unter Mhiedlichen Emptindlichkeit zu erhalten Flughaferpflanzen hielten etwa vicnnai so vicl Spritzmittellösung ciner handclsüblichen Asulamformulierung zurück wie Flachs. Die Penetration bei Flachs erfolgte vicl schnelier als bei Flughafer. Der Zusatz von oberflächenaktiven Stoffen and hohe Luftfeuchtigkeit erhöhten die Penetration des Herbizids bei Flughafer beträchtlish. Tcmperaturerhöhung von 10 auf 30°C führte bei beiden Pflanzenarten zu einer starken Zunahme der Penetration. Nach Blattapplikation von ¹⁴C-Asu lam war bei Flughafer die Radioaktivität über die gesamte Pflanze verleilt; bei Flachs dagegen fand nur eine sehr beschränkteTranslokation statt. Hier verblieb die meiste Radio aktivität im behandelten Blatt. was wahrscheinlich auf eine Schädigung durch Kontaktwirkung des Mittels zURÜCKZU führenist. Qualitative oder quantitative Unlerschiede im Metabolismus von Asulam in den beiden Pflanzen konnten nicht gefunden werden. Unscre Untersuchungen lassen vermuten. dass Spritzmittelretention. Biattpenetration and Translokation gemeinsam für die Selektivität von Asulam zwisehen Flughafer und Flachs eine wichiige Rolle spielen.     

Cross-resistance pattern and alternative herbicides for Cyperus difformis resistant to sulfonylurea herbicides in Korea

A Cyperus difformis L accession from Chonnam province, Korea was tested for resistance to the sulfonylurea herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, the pyrimidinyl thiobenzoate herbicide, bispyribac-sodium, and the imidazolinone herbicide imazapyr, but not to imazaquin. Multiple resistance was tested using twelve herbicides with target sites other than acetolactate synthase (ALS). The R biotype could be controlled by other herbicides with different modes of action such as butachlor, carfentrazone-ethyl, clomeprop, dithiopyr, esprocarb, mefenacet, oxadiazon, pretilachlor, pyrazolate and thiobencarb, applied to soil at recommended rates. Several sulfonylurea herbicide-based mixtures can control both the R and S biotypes of C difformis, except sulfonylurea plus dimepiperate, molinate or pyriftalid, and pyrazolate plus butachlor. Although mixtures of sulfonylurea herbicides might be more effective, they should be avoided and used only in special cases. In terms of in vitro ALS activity, the R biotype was 1139-, 3583-, 1482-, 416-, 5- and 9-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, pyrazosulfuron-ethyl, bispyribac-sodium and imazapyr, respectively, than the S biotype. The in vivo ALS activity of the R biotype was also less affected by the sulfonylurea herbicides, imazosulfuron and pyrazosulfuron-ethyl, than the S biotype. Results of in vitro and in vivo ALS assays indicated that the resistance mechanism of C difformis to ALS inhibitor herbicides was primarily due to an alteration in the target enzyme, ALS. Greenhouse experiments showed delayed flowering and reduced seed production of the R biotype, which could possibly result in reduced fitness. This unusual observation needs to be confirmed in field situations.     

The seasonal response of Lantana camara to selected herbicides

At 7- to 8-week intervals between September 1990 and February 1993, blocks of Lantana camara L. cv. `Helidon White' were treated with four herbicides (fluroxypyr, metsulfuron-methyl, glyphosate and dichlorprop) as an overall high-volume spray at the recommended label rates. Mortality for each treatment was recorded and correlated with climatic data (maximum, minimum air and soil temperature, rainfall, day length and humidity) recorded for the site. Fluroxypyr killed more than 90% of the L. camara if at least 35 mm of rain was received in the preceding 6 weeks and provided that the average minimum daily temperature for the week before the application was above 15 °C. Similarly, glyphosate caused more than 80% mortality when the rainfall was greater than 60 mm in the preceding 6 weeks, with a similar temperature requirement to fluroxypyr. In contrast, dichlorprop and metsulfuron-methyl caused maximum kills of 35–80% and 83% respectively. This occurred in the summer or early autumn (at times when fluroxypyr and glyphosate also gave maximum kills), but times of maximum kill for dichlorprop and metsulfuron-methyl did not correlate with any specific climatic characteristics. Current field practice is to apply all herbicides in autumn (March–May) when L. camara is growing actively. The consequence of this is that, if some plants are not killed, they can go undetected until the next growing season. However, this study shows that fluroxypyr and glyphosate can be sprayed earlier in the year, thus allowing for follow-up sprays later in the same growing season to kill any regrowth.     

The efficacy of several herbicides in the vineyard and their toxicity to grapevines

Application of several herbicides and a combination of herbicides in two vineyards resulted in a perfect control of Bermuda grass by glyphosate and mixed or alternate applications of MSMA and dalapon. Johnson grass was eliminated by MSM A with and without the addition of dalapon. Dalapon combined with MSMA reduced the yield of the grapevines and their growth, as measured by the weight of pruning. Yields were also significantly reduced by aminotriazole and in one vineyard also by simazine. Reduced vegetative growth was caused by MSMA and glyphosphate. MSMA and glyphosphate reduced the chlorophyll content of the grape leaves and the reducing sugar content of the canes in winter. Amino triazole reduced the reducing sugar content of both leaves and canes and the nitrogen content of the canes. In one vineyard simazine reduced the chlorophyll content of the leaves and increased the nitrogen content of the canes. MSMA alone and in combination with dalapon increased the arsenic content of leaves, canes and fruits of grapevines. Arsenic levels were the highest in the canes, but still did not exceed 0.6 ppm. Levels were lowest in fruits and did not exceed 0.1 ppm. Dalapon reduced the chlorophyll content of leaves in June and increased it in July. It also affected the reducing sugar content of leaves and canes without affecting yields or growth.     

双氟磺草胺、2甲4氯联合作用及作物安全性评价

为明确双氟磺草胺、2甲4氯复配的联合作用类型及在小麦田应用的可行性,采用温室盆栽生物测定法和田间药效试验,研究了二者对播娘蒿、猪殃殃等的联合毒力、田间除草效果及其对当茬小麦和后茬作物的安全性。结果显示,双氟磺草胺、2甲4氯复配对播娘蒿为增效作用,对猪殃殃为相加或增效作用,二者适宜配比为1：100~120。43%双氟磺草胺·2甲4氯SE（混配比例为1：110） 387、516、645和1 032 g/hm²防除小麦田阔叶杂草效果均较好,秋季施药鲜重防除效果为99%以上,春季为95%以上。43%双氟磺草胺·2甲4氯SE对当茬作物小麦和后茬作物玉米、大豆、花生、棉花出苗和生长均无影响。     

The impact of uptake, translocation and metabolism on the differential selectivity between blackgrass and wheat for the herbicide pyroxsulam

BACKGROUND: Wheat shows selectivity to pyroxsulam, a new broad‐spectrum herbicide with high activity on blackgrass. Studies were performed to establish whether uptake, translocation or metabolism were responsible for the differential activity in wheat compared with blackgrass. In addition, the effect of the safener cloquintocet‐mexyl on metabolism was evaluated in wheat and blackgrass shoots. RESULTS: Root uptake of pyroxsulam in blackgrass was significantly higher than in wheat, suggesting a possible activity enhancement in blackgrass owing to root uptake. Translocation to foliage from root uptake as well as translocation out of treated foliage following foliar applications was low in wheat compared with blackgrass, likely owing to the rapid metabolism of pyroxsulam in wheat. Wheat metabolized pyroxsulam significantly faster than blackgrass to the less active O‐dealkylation product. Wheat shoots metabolized pyroxsulam faster when the safener cloquintocet‐mexyl was present, but cloquintocet‐mexyl did not increase the rate of metabolism in blackgrass. CONCLUSIONS: The selectivity of pyroxsulam to wheat relative to blackgrass was connected primarily with differences in the rate of metabolism and generation of an inactive metabolite. Metabolism in wheat restricted subsequent movement of radioactivity out of the treated leaf. The rapid metabolism in wheat was increased by the addition of cloquintocet‐mexyl. Copyright © 2010 Society of Chemical Industry     

Weed Control in Berseem using Stale Seed-bed,EPTC, and MCPB

Abstract

A field experiment was conducted in 1973 and 1974 at Udaipur, India to evaluate the selective weed control efficacy of stale seed-bed prepared with paraquat (1 kg/ha) or by cultivation, pre-planting incorporation of EPTC (1.5 kg/ha), and post-emergent application of MCPB (0.5 kg/ha). Two crop protectants, NA and activated carbon, were also field tested as seed treatments against injury by EPTC. It was found that stale seed-bed prepared by desiccation of weed seedlings with paraquat a day before planting berseem (Trifolium alexandrinum L.) and pre-planting incorporation of EPTC were both effective in significantly reducing weed growth and boosting yields of berseem. Berseem seeds coated with activated carbon before planting provided appreciable protection to the crop against EPTC, but NA stunted berseem growth. A combination of stale seed-bed and EPTC caused maximum reduction in weed growth. Post-emergent MCPB, though efficient in controlling weeds, was highly phytotoxic to the crop. Chenopodium spp. and Phalaris minor were lower in net energy content than berseem.