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Methabenzthiazuron is a preemergence herbicide, urea derivative and photosynthetic inhibitor that inhibits photo-synthetic electron transport at the “diuron site”. After treatment with this herbicide, the wheat crop showed “physiological effects”, such as a delayed senescence of leaves, a “greening effect” and a decrease in carbohydrate content. A high number of herbicides, whose only common attribute is their photosynthetic electron transport action, give the same kind of response (1).

Weeds represent the most serious problem in wheat in Egypt. For their control, two field exper-iments were carried out during two winter seasons (2004/2005) and (2005/2006) at National Re-search Centre experimental station at Shalakan, Kalubia Governorate. Some groups of herbicides (Dirby, Harmony extra, Granstar, Ecopart, Illoxan, Topic and Arelon) as well as hand weeding and unweeded treatments were evaluated in wheat. In addition, herbicide combinations were also as-sessed. Harmony extra at 24 g / fed. provided ac-ceptable control for broad leaved weeds but failed to control completely narrow-leaved weeds. Topic at 140 g / fed. provided great control of narrow weeds (97.68% reduction in dry weight after 90 days from sowing). Mixtures of both Harmony extra +Topic at rates (18 g / fed. +105 g / fed.) were better than Harmony extra alone for weed control (99.19 % control, 90 days after sowing) and grain yield. Concerning the other herbicides, Granstar + Topic were effective in controlling both broad and narrow weeds. The efficacy of Harmony extra + Illoxan was lower (91.2% con-trol). Overall, Arelon or mixture of Harmony extra +Topic were the most effective treatments with regard to weed control and wheat growth, yield and its attributes. However, no carryover damage with all used herbicides was observed on wheat. Estimating individual amino acids in the yielded grain revealed increase in essential and nonessen-tial amino acids due to single or combined appli-cation of herbicides. Pronounced increase was recorded with Harmony extra and Topic

Summary In glasshouse experiments, the addition of four ‘pyridine herbicides’ (substituted picolinic and pyridyloxyacetic acids) to either diclofop-methyl or flamprop-methyl had little effect on wild oat (Avena fatua) control. This contrasts with the serious antagonisms which occur with 2, 4-D and 2, 3, 6-TBA. With wild and cultivated oat, l'-methylheptyl (4-amino-3, 5-dichloro-6-fluoro-2-pyridyl)oxyacetate (Dowco 433) was completely compatible with diclofop-methyl and flamprop-methyl, and there was evidence that its presence improved the control of wild oats. Picloram, 3, 6-dichloropicolinic acid and triclopyr had only slight effects on phytotoxicity. The control of cleavers (Galium aparine) by picloram, triclopyr and Dowco 433 was not significantly reduced by addition of flamprop-methyl. Preliminary metabolism studies suggest that picloram does not greatly increase the rate of diclofop detoxification as do 2, 4-D and 2, 3, 6-TBA, and the observed compatibility could well be a direct consequence of this. The absence in these greenhouse experiments of serious antagonism between the pyridine herbicides and diclofop-methyl or flamprop-methyl suggests that ‘tank mixes’ of these herbicides could be used for the control of both broad-leaved weeds and wild oats. Resume Associations compatibles et antagonistes d'herbicides antidicotyledones avec le diclofop-methyl et le flamprop-methyl Dans des experimentations menees en serre, l'addition de quatre herbicides pyridiniques (acides picolinique et pyridyloxyacetique substitues) au diclofop-methyl ou flamprop-methyl n'a pas d'influence sur la destruction de la folle avoine. Ceci differe notablement des divers antagonismes se manifestant avec le 2, 4-D et le 2, 3, 6-TBA. Sur de l'avoine cultivee et de la folle avoine, le methylheptyl (4-amino-3, 5-dichloro-6-fluoro-2-pyridyl)oxyacetate (Dowco 433) etait tout a fait compatible avec le diclofop-methyl et le flamprop-methyl. De plus, a l'evidence sa presence permet une meilleure destruction de la folle avoine. Le piclorame, l'acide 3, 6-dichloropico-linique et le triclopyr provoquent une legere phytotoxicite. La destruction du gaillet par le piclorame, le triclorpyr et le Dowco 433 n'est pas significativement abaissee par l'addition de flamprop-methyl. Des etudes preliminaires de metabolisme suggerent que le piclorame n'accelere pas dans de grandes proportions la detoxification du diclofop comme le font le 2, 4-D et le 2, 3, 6-TBA. La compatibilite observee pourrait bien etre une consequence directe de cela. Dans ces experimentations en serre, l'absence d'antagonismes serieux entre les herbicides pyridiniques et le diclofop-methyl ou le flamprop-methyl amene a penser que des melanges extemporanes de ces produits pourraient etre utilises pour lutter simultanement contre la folle avoine et les dicotyledones. Zusammenfassung Kompatible und antatognistische Mischungen von Diclofop-methyl und Fiamprop-methyl mit Herbi-ziden gegen dikotyle Unkrauter In Gewachshausversuchen wirkte sich der Zusatz von vier ‘Pyridin-Herbiziden’ (substituierte Pico-linsuuren und Pyridinoxyessigsauren) weder zu Diclofop-methyl noch zu Fiamprop-methyl kaum auf die Bekampfung von Flughafer aus, Dieser Befund steht in krassem Gegensatz zu dem starken Antagonismus mit 2, 4-D und 2, 3, 6-TBA, Gegenuber Flughafer und Kulturhafer war 1-Methylheptyl (4-amino-3, 5-dichlor-6-fluor-2-pyridyl)oxyacetat (Dowco 433) in Kombination mit Diclofop-methyl und Fiamprop-methyl voll kompatibel und ergab sogar Hinweise flir eine verbesserte Wirkung gegen Flughafer, Picloram, 3, 6-Picolinsaure und Triclopyr beeinflussten die Phytotoxizitat nur geringfugig. Die Wirkung von Picloram, Triclopyr und Dowco 433 gegen Klet-ten-Labkraut wurde durch den Zusatz von Flam-prop-methyl nicht signifikant beeinflusst, Vorlaufige Metabolismusstudien zeigen, dass Picloram die Detoxifizierung von Diclofop nicht wesentlich beschleunigt, wie es bei 2, 4-D und 2, 3, 6-TBA der Fall ist, Es wird deshalb angenommen, dass das der Grund flir die beo-bachtete Kompatibiliat ist. Da in diesen Gewachshausversuchen kein nen-nenswerter Antagonismus zwischen den Pyridin-Herbiziden und Diclofop-methyl oder Fiamprop-methyl beobachtet wurde, kann angenommen werden, dass Tankmischungen mit diesen Herbi-ziden flir die gleichzeitige Bekampfung von breitblattrigen Unkrautern und Flughafer geeig-net sind.

The separate enantiomers of diclofop-methyl and fenoxaprop-ethyl were incubated with two soils under aerobic conditions. Rapid hydrolysis to the corresponding acids diclofop and fenoxaprop was observed. At various time intervals after soil treatment the parent compound and its free acid were extracted and the extracts were investigated by high-performance liquid chromatography. The determination of the K:S-ratio using a chiral stationary phase revealed that no racemisation of the esters took place. However, inversion of the hydrolysis products was observed. In both soils the acids with the S-configuration showed a significantly higher inversion tendency than the acids with the R-configuration. In one soil the S-acids of both herbicides were inverted (50% inversion in 4–7 days) to yield, ultimately, a residue containing 70% R- and 30% S-enantiomer.

A method is described for the analysis of soils for residues of the herbicide diclofop-methyl, methyl (RS)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionate, and its breakdown product diclofop, (RS)-2-[4-(2,4-dichlorophenoxy)phenoxy]propionic acid. Diclofop-methyl undergoes hydrolysis in the soil to diclofop, which also has herbicidal activity. A procedure, using a 1% phosphoric acid solution for extraction purposes, has been developed and gives good recoveries of both diclofop-methyl and diclofop at the 0.5 and 0.05 mg kg−1 levels. After methylation, gas-liquid chromatography with electron-capture detection is used to determine total residue concentrations.

In a controlled environment experiment, five phenoxy herbicides were sprayed at two rates on 14-day-old winter wheat (Triticum aestivum L. emend Thell ’Norstar’). After 7 additional days of active growth, the plants were cold-hardened for 14 days and then subjected to a freezing test. Four of the herbicides — MCPA amine, 2,4-D ester, 2,4-DB, 2,4-D amine — significantly reduced the cold hardiness of winter wheat whereas diclofop methyl had a minor effect. The reduction in hardiness was greater at the higher rates of application than at the lower rates.

A sensitive gas chromatographic method was developed for the multiresidue determination of 7 neutral herbicides in sediment. The sediment sample was ultrasonically extracted 3 times with acetone. The extract was concentrated to about 50 mL and then partitioned with 2% KHCO3 and CH2C12. The organic phase was dried over anhydrous Na2So4. The concentrated extract was then cleaned up on a 10% deactivated Florisil column, and the herbicides were separated into 2 fractions. Further cleanup of these fractions was performed on activated Florisil columns. Electron capture detection was used for analysis except for atrazine which was analyzed by nitrogen-phosphorus detection. Recoveries of the herbicides from fortified sediment samples at 3 levels were generally better than 80%. The practical detection limit of this method was 1 ppb or 1 ng/g based on a 50 g sediment sample.

Herbicides for the control of annual grass weeds were applied to established seed-producing stands of bromegrass (Bromus inermis Leyss.) and crested wheatgrass (Agropyron cristatum (L.) Gaertn.) in spring each year 1979 through 1981 and to timothy (Phleum pratense L.) in 1980 and 1981. Flamprop methyl reduced seed yields in 2 years in bromegrass and in 1 year in crested wheatgrass and timothy. Diclofop methyl and difenzoquat reduced timothy and bromegrass yields, but not yields of crested wheat-grass. Diclofop methyl and flamprop methyl stunted timothy, reduced the number of seed heads formed, and delayed their maturation. Propanil reduced timothy seed yield 1 year, but did not reduce bromegrass yields. Dichlobenil had no deleterious effects.Key words: Bromus inermis, Agropyron cristatum, Phleum pratense, seed production, herbicides

Pre-treatment with abscisic acid (ABA) can protect oats (Avena sativa) against damage from the herbicide diclofop-methyl. Examination of the uptake and translocation of diclofop-methyl showed that although 20 μg ABA induced varying degrees of stomatal closure, ABA had no significant effect on the amount of herbicide entering the leaf. Translocation of [14C] diclofop-methyl was also unafected by ABA treatment. Electrolyte leakage studies demonstrated that ABA prevented the loss of plasmalemma integrity normally associated with diclofop-methyl damage. It was concluded that ABA protection was by active metabolism, and an increase in the tolerance of the plasmalemma to diclofop-methyl.

The immediate and residual effect of diclofop methyl (2(4-(2,4-dichlorophenoxy)-phenoxy propionic acid methyl ester)), diclofop methyl plus 2,4-D ((2,4-dichlorophenoxy) acetic acid), and the 2,4-D/mecoprop (2,(4-chloro-1-tolyl oxy) propionic acid)/dicamba (3,6-dichloro-o-anisic acid) mixture applied during 2 consecutive yr and for two dates of soil preparation has been evaluated on plots sown and unsown with oats (Avena sativa L.). The population changes observed during the 2 yr of herbicide applications have been related to the nature of the products and were of short duration. No difference between the herbicide treatments has been observed 1 yr after the treatment. Soil preparation in early June and the presence of oats have reduced considerably the weed populations during the 2 yr of herbicide applications. This effect has been noticeable 1 yr after the treatments. Herbicides are not solely responsible for weed population changes. From this study, it appears that cultural practices play a role as important as herbicides in controlling weed populations at least on a short-term basis.

Summary Avena sativa cv. Amuri fed either low or high nitrate was sprayed with diclofop-methyl (1 kg a.i. ha-1) at the three leaf stage. The short term effects of the herbicide on chlorophyll concentration of leaves (laminae) and short and long term effects on d.wt of the component plant parts were determined by comparison with unsprayed plants. For unsprayed and sprayed plants, total leaf d.wt approximately doubled during the first twelve days after commencing treatments. Growth was substantially greater at high nitrate than low nitrate. For unsprayed plants, the increase in total leaf d.wt was due primarily to growth of leaf 3 but for sprayed plants it was due to growth of leaves 1 and 2. Twelve days after commencing treatments, d.wt of leaves 1 and 2 was substantially greater for sprayed plants than for unsprayed plants given similar nitrate, while chlorophyll concentration was substantially less. Leaf 3 d.wt and chlorophyll concentration were substantially greater in unsprayed plants than in sprayed plants given similar nitrate. For unsprayed plants, values were greater at high nitrate than low nitrate, for sprayed plants the converse was the case. Forty nine days after commencing treatments, unsprayed plants had a greater total plant d.wt than sprayed plants given similar nitrate. Total plant d.wt for unsprayed plants was greater at high nitrate than low nitrate, the opposite was the case for sprayed plants. Unsprayed plants at both nitrate levels and sprayed plants given low nitrate produced seed heads but sprayed plants given high nitrate did not. Diclofop-methyl at a rate of 0.3 kg a.i. ha-' stopped seed head production at high nitrate. Retention and uptake of diclofop-methyl were not significantly different at low and high nitrate. At 1 kg a.i. ha-l diclofop-methyl, plants switched from low to high nitrate at spraying showed damage similar to that shown by plants given high nitrate throughout. Addition of 200 μg GA into the leaf sheaths two days prior to spraying increased the efficacy of diclofop-methyl at low nitrate. It is proposed that increased efficiency of diclofop-methyl at high nitrate is due to increased leaf damage caused by a greater rate of leaf expansion.

Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatuaL.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.

Lentil (Lens culinaris Medik.) was tolerant to trifluralin, ethalfluralin, triallate, metolachlor and metribuzin applied preplant soil incorporated at rates of 1.1, 1.1, 1.7, 2.6 and 0.28 kg (a.i.)/ha, respectively. Chloramben and EPTC applied in a similar manner at rates of 2.0 and 3.0 kg (a.i.)/ha, respectively, injured lentils. Diclofop methyl, sethoxydim, fluazifop butyl, haloxyfop methyl and several experimental grass-specific herbicides were tolerated by lentil but propanil and flam-prop methyl were phytotoxic to this crop. Lentil was also tolerant to tank mixtures of trifluralin and triallate, trifluralin and metribuzin, metolachlor and metribuzin, and sequential treatments of dinitroaniline-type herbicides applied preplant incorporated followed by a post-emergence application of metribuzin or dinoseb. Lentil seed density was reduced by triallate in 1983 and seed size was reduced by flamprop methyl in 1982 and by trifluralin, triallate, metolachlor, EPTC, chloramben, metribuzin and trifluralin + metribuzin mixtures in 1983.Key words: Herbicides, lentil, preplant incorporated, postemergence, seed quality, sequential treatments

Field experiments were conducted over a 2-yr period to evaluate the need for competition by crop plants along with the application of postemergence herbicides for wild oat (Avena fatua L.) control in barley and wheat. Barban, difenzoquat, and barban plus difenzoquat were used in barley and barban, benzoylprop ethyl, diclofop methyl, flamprop methyl, and barban plus benzoylprop ethyl were used in wheat, at the two-leaf stage and the four-leaf stage of wild oats seeded alone or in a crop. Barban and diclofop methyl were effective for wild oat control at both the two-leaf and four-leaf stage of wild oats. Benzoylprop ethyl, difenzoquat and flamprop methyl alone or in combination with barban were more effective at the four-leaf than at the two-leaf stage of wild oats. Herbicide treatments increased barley yield up to 84% and wheat yield up to 177%. In the absence of herbicide treatments, crop competition from barley or wheat reduced the wild oat dry weight by about 50%. Competition by crop plants was essential for effective wild oat control with all foliage-applied wild oat herbicides included in this study.Key words: Competition, crop, wild oat, herbicides, wheat, barley

The metabolism of the herbicide, diclofop-methyl (methyl-2-[4-(2′, 4′-dichlorophenoxy) phenoxy]propanoate), in cell suspension cultures of Avena sativa L. (cv. Garry) and in callus of Avena fatua L. (transferred to liquid) was determined as a function of time (8 h to about 3 weeks) and was compared to previous metabolism data from intact plants. A. fatua metabolized 14C-labeled diclofop-methyl more rapidly than A. sativa, but the metabolites formed were similar if not identical. Within 2 days, approximately 50% of the total 14C recovered was in A. fatua cells whereas less than 15% was in A. sativa cells. In older cultures of A. fatua, the amounts of 14C in the cells and in the medium were about 45% each; 10 to 12% was in the non-extractable cell residue. The 14C recovered from A. sativa cells increased to a maximum of about 35% at 7 days and then slowly decreased to about 18% by 21 days, whereas the 14C in the medium of A. sativa decreased to about 60% at 7 days and then increased to over 75% by 21 days. The nonextractable 14C residue was 5% or less even after 21 days. Major metabolites in methanolic extracts of cells of both A. sativa and A. fatua were diclofop (2-[4-(2′, 4′-dichlorophenoxy)phenoxy] propanoate), diclofop hydroxylated at an undetermined position on the 2,4-dichlorophenyl ring (ring OH-diclofop), and conjugates of diclofop and ring-OH diclofop.

The basis for 2,4-D [(2,4-dichlorophenoxy)acetic acid] antagonism of diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy) phenoxy] propanoate} toxicity to wild oat (Avena fatuaL.) was investigated by studying changes in the metabolism of diclofop-methyl in vitro. An esterase from wild oat, which hydrolyzes diclofop-methyl to the acid diclofop, was extracted, partially purified, and the reaction characterized. The rate of hydrolysis of14C-diclofop-methyl was 0.14 ηmoles/2 h at standard assay conditions of 0.25 mg lyophilized enzyme preparation (19.6% protein) in 0.1 ml phosphate buffer (0.1 M, pH 7.0), substrate 5 μM. The addition of 2,4-D to this reaction did not inhibit14C-diclofop formation. Higher levels of 2,4-D stimulated enzymic hydrolysis.14C-diclofop-methyl was rapidly metabolized to14C-diclofop and polar14C-conjugates when vacuum-infiltrated into wild oat leaf segments. The addition of 2,4-D caused small increases in the rates of both14C-diclofop-methyl de-esterification and14C-diclofop conjugation. It is concluded that 2,4-D does not inhibit the in vitro de-esterification of diclofop-methyl.

Growth of the second leaf of susceptible wild oat (Avena fatua L.) was inhibited within 2 days after treatment with the herbicide, diclofop-methyl, in the 1-1/2 leaf stage. Leaf growth of resistant wheat (Triticum aestivum L.) was unaffected by diclofop-methyl. In wild oat. chlorosis developed 1 day after leaf growth was inhibited. Foliar absorption of diclofop-methyl was similar between wild oat and wheat with 67 and 61% of the recovered radioactivity from [14C]diclofop-methyl being absorbed by wild oat and wheat, respectively, after 4 days. Wild oal was equally sensitive to the methyl ester and acid forms of the herbicide when the compounds were injected into the stem. Wheat was unaffected by both forms when treated similarly. Very little diclofop-methyl and diclofop (combined total of 10 to 12% in wild oat and 5 to 7% in wheat) remained in plant tissues 2 days after leaf treatment in both susceptible and resistant plants. Therefore, the active form of the herbicide must inhibit growth of susceptible plants very rapidly and at relatively low concentrations. Diclofop-methyl was rapidly hydrolyzed to diclofop by wild oat and wheat. Wild oat predominantly conjugated diclofop to an ester conjugate but wheat hydroxylated the 2,4-dichlorophenyl ring and formed a phenolic conjugate. The formation of the different conjugates between wild oat and wheat was the most significant difference in metabolism between the two species. Nearly 60 and 70% of the methanol-soluble radioactivity was present as water-soluble conjugates in wild oat and wheat, respectively, 4 days after treatment.

Oat (Avena sativaL. ‘Elgin′) seedlings were treated with combinations of diclofop-methyl {methyl ester of 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} and 2,4-D amine [dimethylamine salt of (2,4-dichlorophenoxy) acetic acid] or diclofop-methyl and chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1, 3, 5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} to determine the effect of the added herbicide on diclofop-methyl activity. Diclofop-methyl applied alone at rates of 0.50, 0.75, and 1.00 kg/ha killed the oat plants 14 days after treatment. When 2,4-D amine at 0.74 and 1.11 kg/ha was combined with diclofop-methyl, the phytotoxicity of diclofop-methyl was reduced. An antagonistic interaction between diclofop-methyl and 2,4-D was detected. Chlorsulfuron, applied alone, at 20, 40, or 60 g/ha did not affect the growth of oats. Chlorsulfuron additions did not affect the activity of diclofop-methyl. Diclofop-methyl reduced oat coleoptile elongation. Equimolar concentrations of diclofop-methyl and 2,4-D at or above 1 μM significantly reduced the 2,4-D response. A ten-fold increase of either 2,4-D or diclofop-methyl, above an equimolar concentration of 1 μM, significantly enhanced the effect of the herbicide being increased.

Summary In pot and field experiments the addition of Ethylan D256 surfactant to spray solutions improved control of black-grass (Alopecurus myosuroides Huds.) by diclofop-methyl. Various other surfactants and oil adjuvants enhanced phytotoxicity but, generally, to a lesser extent. Ethylan D256 had most effect with applications made at early growth stages. Control of older plants was generally poor, whether or not the surfactant was added. Addition of Ethylan D256 had little effect on selectivity between A. myosuroides and cereals from lower than recommended doses of diclofop-methyl, but there was a suggestion of yield reduction from higher doses. Tank mixing with esters of ioxynil and bromoxynil sometimes improved control by diclofop-methyl but in other circumstances either had no effect or reduced phytotoxicity. Applications of diclofop-methyl in 60 or 120 1 ha−1 spray volume were as effective as applications in 240 1 ha−1. Resume L‘utilisation d'adjuvants pour ameliorer l'efficacite du diclofop-methyl sur le vulpin (Alopecurus myosuroides Huds.) Dans des experimentations en pots et sur le champ, l'adjonction du surfactant Ethylan D 256 aux bouillies de pulverisation a ameliore l'efficacite sur vulpin du diclofop-methyl. D'autres surfactants et adjuvants huileux ont egalement ameliore l'activite herbicide mais, en general, d'une facon moindre. Les meilleurs resultats d'Ethylan D 256 ont ete obtenus avec des applications a des stades de developpement precoces. La destruction des plantes plus âgees etait en general insuffisante, qu'il y ait eu ou non adjonction de surfactant. L'adjonction d'Ethylan D 256 a eu un leger effet sur la selectivite vis-a-vis des cereales des des doses de diclofop-methyl inferieures aux doses recommandees, mais il avait une presupposition de baisse de rendement pour des doses plus elevees. Le melange dans la cuve avec des esters de ioxynil et bromoxynil a parfois ameliore l'efficacite du diclofop-methyl, mais dans d'autres circonstances on a eu soit pas d'effet, soit une activite herbicide reduite. Des applications de diclofop-methyl avec un volume de bouillie de 60 ou 120 1 ha−1 ont ete aussi efficaces qu'avec 240 1 ha−1. Zusammenfassung Die Verwendung von Hilfsstoffen zur Erhohung der Wirkung von Diclofop-methyl gegen Ackerfuchsschwanz (Alopecurus myosuroides Huds.) In Topf- und Feldversuchen erhohte der Zusatz des Netzmittels Ethylan D526 zur Spritzbruhe den Bekampfungserfolg gegen Ackerfuchsschwanz (Alopecurus myosuroides Huds.). Verschiedene andere Netzmittel und Oelzusatze steigerten die Phytotoxizitat, aber im allgemeinen in einem geringeren Masse. Den Grossten Effekt zeigte Ethylan D526 bei Applikationen auf fruhe Wachstumsstadien. Bei alteren Pflanzen war der Erfolg, mit oder ohne Netzmittel, meist gering. Der Zusatz von Ethylan D526 zu Spritzbruhen, deren Konzentration unter den fur die Praxis empfohlenen Dosierungen lag, hatte wenig Einfluss auf die Selektivitatsmarge zwischen A. myosuroides und den Getreidearten; bei hoheren Dosierungen wurde jedoch eine Tendenz zu Ertragsverminderungen festgestellt. Tankmischungen mit Estern von Ioxynil und Bromoxynil erhohten in gewissen Fallen die Wirkung von Diclofop-methyl, in anderen Fallen wurden jedoch keine Wirkungsveranderungen oder gar eine Verringerung der Phytotoxizitat beobachtet. Die Applikation von Diclofop-methyl in Spritzbruhemengen von 60 oder 120 1 ha−1 war gleich wirksam wie die Applikation in 240 1 ha−1.

SUMMARY Winter wheat varieties were treated with the wild-oat herbicides difenzoquat and diclofop-methyl at several growth stages in a series of four field experiments. High rates of difenzoquat damaged the winter wheat varieties Bouquet, Sportsman, Hobbit and Maris Huntsman but not Hustler. Treatment of the sensitive varieties during tillering stimulated excessive tiller production, resulting in more ears with fewer and smaller grains than on the unsprayed controls; later applications reduced the number of grains and severely depressed yield. In contrast, the early applications of diclofop-methyl, during tillering, were more damaging than the later ones. Bouquet was more tolerant of diclofop-methyl than were the other varieties tested.

Ultrastructural effects, absorption, and translocation of the experimental compound methyl-2-(4-(2,4-dichlorophenoxy)phenoxy)propanoate (MPP), topically applied to resistant wheat (Triticum aestivum L.) and susceptible wild oat (Avena fatua L.), were studied.The two species were affected differently by MPP when greenhouse-grown seedlings were treated at the [Formula: see text]-leaf stage. The second leaf of both species was damaged, but wild oat leaves were affected much more than wheat leaves. Although tissues formed after treatment and the apical region of the second leaf of wheat did not appear to be injured, ultrastructural modifications occurred. In wild oat, both visible injury and ultrastructural modifications were seen. Chloroplasts were the organelles most affected by the compound in both species. Cellular alterations ranging from slight to complete destruction of the cytoplasm were observed in cells of treated leaves. Frequently cells with undamaged chloroplasts were located next to cells with damaged chloroplasts. The translocation patterns of [14C]MPP applied as a drop were similar in wheat and wild oat and could not account for the differences in their sensitivities. About 95% of the 14C was recovered in the region of application in both species.

Summary Influence of 2,4-D on toxicity of diclofop-methyl to Avena sativa (cv. Selma) and Arena fatua at 2·5 leaf stage has been evaluated under controlled conditions. Effects of 2,4-D on the fate of diclofop-methyl in cultivated oat have also been studied. Mixture with 2,4-D reduced the toxicity of diclofop-methyl to both species. When applied immediately after diclofop-methyl treatment, 2,4-D still reduced herbicide toxicity to wild oat. This reduction was smaller in cultivated oat. and was only observed at higher phytotoxicity. No interaction was observed when a 10-day period separated the two applications. In mixture, 2,4-D enhanced diclofop-methyl penetration and diclofop acid conjugation in cultivated oat, and it slightly increased conjugation when applied separately. None of these effects clearly explain the reduction of diclofop-methyl toxicity by 2, 4-D in cultivated oat. Other processes are possibly involved and could be connected with the site of action of diclofop-methyl. Resume Interaction entre le diclofop-melhyle et le 2,4-D chez la folle avoine (Avena fatua L.) et l'avoine cultivee (Avena sativa L.), et comportement du diclofop-methyle dans l'avoine cultivee. L'influence du 2,4-D sur la phytotoxicite du diclofop-methyle a l'egard d'Avena saliva (cv. Selma) et d'Avena fatua au stade 2,5 feuilles a eteevaluee en conditions controlees, et les effets du 2.4-D sur le comportement du diclofop-methyl dans l'avoine cultivee ont eteetudies. En melange, te 2,4-D reduit la phytotoxicite du diclofop-methyle pour les deux especes. Applique immediatement apres le traitement au diclofop-methyle, il reduit encore l'efficacite de ce dernier sur Avena fatua. Cet effet est moins important dans le cas de l'avoine cultivee et s'observe lorsque la phytotoxicite est forte. Aucune interaction ne se manifeste lorsque dix jours separent les deux applications. En melange, le 2,4-D favorise la penetration du diclofop-methyle et la conjugaison du diclofop acide dans l'avoine cultivee. Applique separement, il augmente legerement la conjugaison de l'acide. Aucun de ces effets ne permet d'expliquer clairement la reduction de la phytotoxicite du diclofop-methyle par le 2,4-D dans l'avoine cultivee, ce qui suppose l'intervention d'autres phenomenes pouvant mettre enjeu les sites d'action du diclofop-methyle. Zusammenfassung Wechselwirkung zwischen Diclofop-methyl und 2,4-D in Flug-Hafer (Avena fatua L.) und Saat-Hafer (Avena sativa L.) und Verhalten von Diclofop-methyl im Saat-Hafer Der Einflus von 2,4-D auf die Phytotoxizitat von Diclofop-methyl auf Avena sativa (‘Selma’) und Avena fatua im 2- bis 3-Blatt-Stadium wurde unter kontrollierten Bedingungen untersucht, auch der Einflus von 2,4-D auf das Verhalten von Diclofop-methyl im Saat-Hafer. Die Mischung mit 2,4-D setzte die Wirkung von Diclofopmethyl auf die beiden Arlen herab. Wenn 2,4-D unmittelbar nach der Diclofop-melhyl-Behand-lung angewendet wurde. senkte es noch die herbizide Wirkung auf den Flug-Hafer. Diese Reduktion war geringer als beim Saat-Hafer und wurde nur bei hoheren Konzentrationen beobachtet. Lagen die beiden Behandlungen 10 Tage auseinander, wurde keine Wechselwirkung fest-gestellt. In Mischungen beschleunigte 2,4-D die Penetration von Diclofop-methyl und die Konjugation von Diclofop-Saure beim Saat-Hafer, bei getrennter Ausbringung nahm die Konjugation nur wenig zu. Durch keinen dieser Effekte konnte die Verringerung der Diclofop-methyl-Wirkung durch 2,4-D beim Saat-Hafer erklart werden. Es sind wahrscheinlich am Wirkort des Diclofop-methyls andere Prozesse beteiligt.

Summary The feasibility of achieving selective wild oat (Avena fatua L.) control in a stand of the Australian oat (Avena sativa L.) cv. Savena I was examined. Diclofop-methyl was applied at rates of 0·4–0·7 kg a.i. ha−1 at the three- and five-leaf stages of A. fatua (84–132 culms m2). Although all rates of diclofop-methyl caused initial chlorosis and necrosis to the crop, the subsequent control of A. fatua permitted increased crop tillering. Avena fatua control and crop yield response were maximized when diclofop-methyl was applied at the three-leaf stage. Crop grain yield was increased by as much as 32% and 22% during 1984 and 1985, respectively. In the absence of A. fatua competition, crop shoot dry weight at ear emergence was reduced only where diclofop-methyl was applied at 0·6 or 0·7 kg ha−1. However, final grain yield was not reduced by any treatment. Only 11 of 240 cultivars or lines tolerated diclofop-methyl, and none reached the level attained by Savena I and a closely related Australian line [(Irwin × (West × New Zealand Cape/42)) × West]/24. The nature of the inheritance of diclofop-methyl tolerance was examined (1983–1985) by crossing and backcrossing (BC) Savena I with four diclofop-methyl susceptible, but agronomically superior, lines. Inheritance of diclofop-methyl tolerance appeared to be controlled by two genes, with susceptibility being dominant to tolerance in F3, BCIF2 and BCIF3 lines. Resume La tolerance des avoines cultivees (Avena sativa L.) vis-a-vis du diclofop-methyl La possibilite d'aboutir a un controle selectif de la folle avoine (Avena fatua L.) dans un champ d'avoine cultivee australienne (Avena sativa L.), variete Savena I, a eteetudiee. Le diclofop-methyl a ete applique a des doses variant de 400 g a 700 g de m.a. ha−1 au stade de 3 et 5 feuilles de la folle avoine (les populations variant de 84 a 132 pieds au m2). Bien que toutes les doses de diclofop-methyl provoquent une chlorose et une necrose initiales de la culture, l'elimination ulterieure d'A. fatua a permis une augmentation du tallage de la culture. Le pourcentage d'elimination de A. fatua et le gain de rendement maximum ont ete constates lorsque le diclofop-methyl a ete applique au stade 3 feuilles. Le gain de rendement a atteint 32 et 22% respectivement au cours des annees 84 et 85. En absence de competition avec A. fatua, le poids sec de la culture a l'epiaison n'a ete affecte que lorsque le diclofop-methyl etait appliquea la dose de 600 ou 700 g ha−1. Cependant, la recolte ne fut affectee in fine par aucun des traitements. Parmi les lignees ou 240 cultivars existants, 11 seulement se sont montres tolerants au diclofop-methyl mais aucun ne le fut autant que Savena I ainsi qu'une lignee australienne proche. (Irwin × (West × New Zealand Cape/42)) × West 1/24). La nature de la transmission de la tolerance au diclofop-methyl a ete examinee (1983–1985) par hybridation (BC) entre Savena I et 4 lignees sensibles au diclofop-methyl mais agronomiquement superieures. Cette transmission semble etre sous le controle de deux genes susceptibles d'etre dominants vis-a-vis de cette tolerance dans les lignees F3, BCIF2 et BCIF3. Zusammenfassung Toleranz des Saat-Hafers (Avena sativa L.) gegenuber Diclofop-methyl In einem Bestand der australischen Sorte 'Savena l'des Saat-Hafers (Avena sativa L.) wurde unter-sucht, ob Flug-Hafer (Avena fatua L.) selektiv bekampft werden kann. Diclofop-methyl wurde mit 0,4 bis 0,7 kg AS ha−1 im 3- und 5-Blatt-Stadium von A, fatua (84 bis 132 Halme m−2) angewandt. Obwohl das Herbizid in allen Auf-wandmengen zunachst an den Kulturpflanzen Chlorosen und Nekrosen verursachte, konnten sie sich infolge der Bekampfung der A. fatua starker bestocken. Bekampfung und Ertrag waren am grossten, wenn Diclofop-methyl im 3-Blatt-Stadium angewandt wurde; der Kornertrag wurde in den Versuchsjahren 1984 und 1985 um 32 bzw. 22% erhoht. Bei fehlender Konkurrenz von A. fatua war die Trockenmasse der Getreidehalme beim Spitzen nur bei 0,6 oder 0,7 kg AS ha−1 Diclofop-methyl berabgesetzt; der Kornertrag war bei keiner Aufwandmenge verringert. Nur 11 von 240 Sorten oder Linien tolerierten Diclofop-methyl, aber keine erreichte den Grad, wie er bei 'Savena l'und einer nahe verwandten australischen Linie vorlag. Der Vererbungsgang fur die Toleranz gegenuber Diclofop-methyl wurde uber die Jahre 1983 bis 1985 durcb Kreuzung und Ruckkreuzung von 'Savena l'mit vier gegen Diclofop-methyl empfindlichen, aber pflanzenbaulich hervorragenden Linien untersucht.

The chlorophyll levels and growth of oat (Avena sativa L. 'Elgin') seedlings were drastically reduced after foliar application of diclofop -methyl {methyl 2[4-(2,4-dichlorophenoxy)phenoxy] propanoate1 . The leaves were chlorotic and necrotic with the newly emerging eaves being most affected. Plants treated with 2,4-D [(2,4-dichlorophenoxy)acetic acid] were similar to the controls. When 2,4-D was applied to intact plants in combination with diclofopmethyl the toxicity symptoms produced by diclofop-methyl were reduced. Diclofop-methyl disrupted membrane integrity and inhibited chlorophyll formation in excised leaf segments. Addition of 2,4-D with diclofop-methyl did not change the effects produced by diclofopmethyl alone in excised leaf segments. Additional index words. Antagonism, chlorophyll, membrane.

The degradation of the herbicide [14C]-diclofopmethyl was investigated in moist parabrown podzol soil at 22°C. Radiochemical procedures were used to monitor the herbicide breakdown. The mineralization of the uniformly labelled aromatic ring was pursued by trapping the14CO2 generated for 96 days. Diclofop-methyl was rapidly degraded in the soil with a half-life of about 8 days. The major breakdown product was the corresponding acid-diclofop, formed by a very rapid hydrolysis of the esterbond. With time the acid appeared to undergo strong binding or complexing to the soil. An intermediate 4-(2,4-dichlorophenoxy) phenol was recovered from the treated soil. Concentration of the phenoxyphenol increased upto 6 days followed by quick decline. Insecticide combination of parathion + Demeton-Smethylsulphoxide partially inhibited diclofop degradation in the soil

Summary: Wild oat (Avena fatua L.) plants sprayed at the 2-or 3-leaf stages of growth with diclotop-methyl developed chlorosis over the entire leaf blade of all leaves. The leaves became necfrotic 7days after spraying Shool growth was inhibited. In wheat (Triticum aesicum L cv.Waldron) discrete chlorotic areas developed only where the herbicide convicted the 2nd or 3rd leaf with no visible injury so new growth uf'ter treutment. Growth inhibition of susceptible oat (Avena sativa L. cv. Garry) was sensitive to placement of diclutop-methyl near the upica and meristematic sites of the plant. Chlorosis and necrosis were independent of herbicide placement. Selective herbicide placement induced chlorosis only or both chlorosis and growth inhibition Root growth in wild oat and barley (Hordeum rulgare L. cv. Dickson) was strongly inhibited by 1–0 μM diclofop-methyl. Wild oat shoots were killed when seedlings were root-treated with 10 μM diclofop-melhyl. The 100 μM rool treatment killed barley shoots but only stunted the growth of wheat shoots by approximately 50%. In root-ireated wheat plants the shoots were turgid and developed a light purple colour, whereas in foliar-treated plants the shoots developed discrete chlorotic areas. Resume: Reaction des plantes resistantes et des plantes sensibles audiclo-fop methyle Des plantes de folle-avoine (Avena fatua L.) traiteers stades de croissance 2 ou 3 feuilles avec du diclofop-methyle ont presente de la chlorose sur la surface entiere du limbe de toutes les autres feuilles, Les feuilles sont devenues necrotiques 7 jours apries le traitement. La croissance des pousses a ete inhibee Chez le bie (Triticum aestivum L. cv Waldron) des zones necrosees discontinues se sont devcloppeesseulement la ou l'herbicide a touche la 2eme et la 3eme feuille. sans deguts visibles sur la nouvelle poussse, de-veloppee apres le traitement. L'inhibition de la croissance d'une variete sensible d'avoine (Avena sativa L, cv Garry) a ete influcncee par le positionnement du diclofop-me-thyle pries des zones apicales et meristematiques de la plante. Chloroses et necroses se sont revelee independantes du posi-tinnement de l'herbicide, l'apport d'herbicide selectif induit, soit seulement des chloroses. soit a la fois des chloroses et tine inhibition de la croissane. La eroissance des racines de la folle-avoine et de l'orge (Hordeum vulgare L, cv Dickson) a ete fortement inhibeer par 1.0 μM de diclofop-methyle Les jeunes pousses de folle-avoine ont ete tuees quand les plantules ont ete traitees. par les racines avec 10 μM de diclofop-methyle, Le traitement des racines avec 100 μM a tue les pousses d'orge, mais a seulement inhibe les pousses de ble de 50% environ. Chez les plantes de ble traitees par les racines, les pousses etaient turgescentes et ont presente une legere coloration rouge viola-cee, cependant que chez les plantes traitees par les feuilles se developpaient des zones chlorotiques discuntinues. Zusammenfassung Die Reaktion resistener und empfindlicher Pflanzen auf Diclofop-methyl Bei Flughaferpflanzen (Avena fatua L.). die im 2-oder 3-Blatt-stadium mit Diclofop-methyl behandelt wurden. wurde bei allen Bluttern die gesamte Blattspreite chlorotisch und sieben Tage nach der Behandlung nekrotisch: das Sprosswachstum war gehemmt. Bei Weizen (Triticum aestivum L.Sorte Waldron) entwiekelten sich charakteristische chlorotische Fleeken nur dort. wo das zweite oder dritte Blatt mit dem Herbizid in Kontakt kam; sichtbare Schuden waren bei der weiteren Entwicklung der Pflanze nicht zu beobachten. Die Wuchshem-mung des empfindlichen Hafers (Avena sativa L. Sorte Garry) war davon abhungig ob Diclofop-methyl in die Nuhevon apika-lem und meristematischem Gewebe appliziert wurde, wuhrend das Auftreten von Chlorosen und Nekrosen unabhungig vom Applikationsort war. Je nachdem, an welchen Stellen das Her-bizid appliziert wurde, traten entweder nur Chlorosen oder Chlorosen und eine Wuchshemmung auf. Das Wurzelwach-stum von Flughafer und von Gerste (Hordeum vulgare L, Sorte Dickson) wurde durch 1,0 μM Diclofop-methyl stark gehemmt Die Sprosse von Flughaferpflanzen wurden abgetotet wenn die Wurzeln der Sumlinge mit 10 μM Diclofop-methyl behandelt wurden, Durch eine Wurzelbehandlung mit 100 μM starben die Gerstensprosse ab, die von Weizen wurden hingegen nur um etwa 50% gestaucht Wurden bei Weizen die Wurzeln behan-delt. blieben die Sprosse turgeszent und verfurbten sich blaurot, wuhrend durch eine Blattbehandlung charakteristische Chlorosen am Spross auftraten.

In controlled environment experiments diclofop methyl, difenzoquat, flamprop methyl, fluazifop-P and seythoxydim were applied to wild oat at the three-leaf stage at recommended rates 10 h before or after a single night of freezing (−4 °C) temperature. Herbicide efficacy, as determined by the change in post-treatment dry weight accumulation of treated wild oats during the ensuing 3 wk period, was unaffected by the freezing temperature. The dry matter accumulation of wild oat exposed to the −4 °C temperature was reduced by 10–20% compared to plants which were grown under a constant 15/5 °C day/night regime.Key words: Oat (wild), frost, diclofop methyl, flamprop methyl, difenzoquat, fluazifop-P, sethoxydim

In controlled environment experiments, the efficacy of diclofop methyl applied to wild oat was reduced more than the efficacy of difenzoquat or flamprop methyl when the soil water content (SWC) was cycled between −0.24 and −2.18 MPa (low SWC) compared to when it was cycled between −0.03 and −0.06 MPa (high SWC). Similarly, at low SWC diclofop methyl was much less effective than either fluazifop-p-butyl or sethoxydim in reducing the post-treatment dry weight accumulation of the weed.Key words: Oat (wild), soil moisture, diclofop methyl, flamprop methyl, difenzoquat, fluazifop-p-butyl