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Summary: The absorption, translocation and degradation of methazole were examined in onion, Stellaria media, Matricaria matricarioides and Veronica persica grown in culture solution. After a short period of initial rapid uptake, all four species absorbed herbicide and water in the same proportions. Translocation of herbicide to the shoots was directly proportional to transpiration, but the apparent solute concentration in the xylem was less than that in the external solution and varied between the species. A smaller percentage of the total absorbed herbicide was translocated to the shoot in V. persica, the most tolerant species. Methazole was relatively stable in M. matricariodes and was degraded slowly to 3-(3,4-dicnlorophenyl)-1-methylurea (DCPMU). It was degraded rapidly to DCPMU in the other three species and this accumulated in onion and S. media. In V. persica DCPMU was degraded further to 3-(3,4-dichlorophenyl) urea (DCPU). Methazole was not an active inhibitor of photosynthesis by isolated spinach chloroplasts. Both DCPMU and DCPU inhibited photosynthesis but DCPMU was 200-times more active than DCPU. Variations in the concentrations of DCPMU in the shoots of the different species largely accounted for the variations in their response to methazole applied pre-emergence. Resume: Aspects de la phytotoxicite du met hazole. II. Comportement dans les plantes apres une penetration par les racines L'absorption, la translocation et la degradation du methazole ont eteetudiee sur oignon. Stellaria media, Matricaria matricarioides et Veronica persica cultivees sur solutions nutritives. Apres une courte periode d'absorption rapide, les quatre especes absorbent l'herbicide et l'eau dans les memes proportions. Le transport de l'herbicide vers les parties aeriennes etait directement proportionnel a la transpiration, mais la concentration dans le xylem etait inferieure a celle du milieu nourricier et variait avec les especes. Le pourcentage d'herbicide absorbe, transporte jusqu'aux organes aeriens, etait plus faible chez V. persica, espece la plus tolerante. Chez M. matricarioides, le methazole etait relativement stable et la degradation en 3-(3,4-dichlorophenyl)-1-methyluree (DCPMU) etait lente. Dans les autres especes, il a ete rapidement metabolise en DCPMU qui s'est accumule en particulier dans l'oignon et S. media. Chez V. persica. le DCPMU a ete degrade en 3-(3,4-dichlorophenyl) uree (DCPU). On a pu montrer, en isolant des chloroplasles d'epinard, que le methazole n'etait pas un inhibiteur tres actif de la photosynthese. En revanche, le DCPMU et le DCPU ont tous deux une action inhibitrice sur la photosynthese, le DCPMU etant 200 fois plus puissant que DCPU. Les variations de la teneur en DCPMU dans les organes aeriens des differentes especes expliquent leur reaction a la suite d'un traitement de pre-levee au melha-zole. Zusammenfassung Axpekte zur .selektiven Phytotoxizitat von Metha-zol. tl. Verhalten in der Pflanze nach Wurzethe-handlung Absorption, Translokation und Abbau von Methazo! wurden in Zwiebeln. Stellaria media. Matricaria matricarioides und Veronica persica. die alle in Nahrlosungen gewachsen slnd. unter-sucht. Nach einer kurzen Anfangsperiode, in der eine rasche Aufnahme erfoigte. absorbierten alle vier Pfianzenarten Herbizid und Wasser imselben Verhaltnis. Die Translokation des Herbizids in die Sprosse war direkt proportional zur Transpi-ration., doch war die gemessene Konzentration im Xylemstrom geringer als diejenige in der ausseren Losung und sie unterschied sich zwischen den Arten. In V, persica, der tolerantesten Art. wurde von der insgesamt aufgenommencn Herbi/id-menge prozentual weniger in den Stengel trans-portiert. Methazol war in M. matricarioides rela-tiv stabil und wurde langsam zu 3-(3,4-Dichlor-phcny Dl-methylharnstoff (DCPMU) abgebaut. In den drei anderen Arten erfolgte dagegen ein schneller Abbau zu DCPMU. In Zwiebeln und 5. media wurde dieser Metabolit angereichert. In V. persiea wurde DCPMU weiter zu 3-(3.4.-Dichlor-pheny Dharnstoff (DCPU) abgebaut. Methazol war bei isolierten Chloroplasten von Spinat kein aktiver Photosynthesehemmer. Dagegen hemm-ten sowoh! DCPMU als auch DCPU die Photo-synthese. allerdings erwies sich DCPMU als 200 mal aktiver als DCPU. Unterschiedliche Reak-tionen auf Methazol, das im Vorautlauf appliziert wird. konnen deshalb weitgehend mit Konzentra-tionsunterschieden in den Sprossen der betref-fenden Arten erklart werden.

Summary: Absorption of methazole by leaves of onion (Allium cepa), Stellaria media, Matricaria matricarioides and Veronica persica was rapid for the first 24 h after treatment and continued at a slower rate for up to 6 days to reach a maximum of between 35 and 60% of the amount applied. Differences in absorption between species were generally small. Absorption by the cotyledon of onion was greater than absorption into true leaves. Methazole on the leaf surface degraded to 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU) and small amounts of this degraded to 3-(3,4-dichlorophenyl) urea (DCPU). Methazole absorbed into leaves was relatively stable in M. matricarioides and DCPMU accumulated slowly. The rate of degradation was more rapid in the cotyledons than in the true leaves. Both in leaves and in cotyledons of onion and S. media, methazole degraded rapidly to DCPMU and this accumulated; in those of V. persica, DCPMU was degraded quickly to DCPU and unidentified products. The amount of DCPMU accumulated in the shoots was broadly correlated with the relative phytotoxicity of methazole to the different species, except for young seedlings of V. persica which contained no DCPMU but were susceptible to methazole. Resume: Aspects de la phytotoxicite du melhazole. III. Comportement dans les plantes apres un traitement foliaire L'absorption du methazole par des feuilles d'oignon (Allium cepa), de Matricaria matricarioides et de Veronica persica a ete rapide au cours des premieres 24 h apres le traitement et s'est poursuivie a un taux plus lent durant 6 jours, pour atteindre un maximum situe entre 35 et 60% de la quantite appliquee. Les differences d'absorption entre les especes ont ete en general petites. L'absorption par les cotyledons chez l'oignon a ete plus importante que par les feuilles vraies. Le methazole a ta surface des feuilles s'est degrade en 3-(3,4-dichlorophenyl)-1-methyluree (DCPMU) et de petites quantites de celle-ci se sont degradees en 3-(3,4-dichlorophenyl) uree (DCPU). Le methazole absorbe par les feuilles s'est revele relativement stable chez M. matricarioides et le DCPMU s'est accumule lentement. Le taux de degradation a ete plus rapide dans les cotyledons que dans les feuilles vraies. Le methazole, aussi bien dans les feuilles que dans les cotyledons de l'oignon et de S. media, s'est degrade rapidement en DCPMU et celui-ci s'est accumule dans les feuilles et les cotyledons de V. persica, le DCPMU s'est degrade rapidement en DCPU et en produits non identifies. Les quantites de DCPMU accumule dans les pousses ont ete en correlation etroite avec la phytotoxicite relative du methazole pour les differentes especes, excepte pour les jeunes plantules de V. persica qui ne contenaient pas de DCPMU mais sont cependant sensibles au methazole. Zusammenfassung Aspekte zur selektiven Phytotoxizitat von Metha-zol. in. Verhalten in Pflanzen nach Blattbehand-lung Die Absorption von Methazol durch die Blatter der Zwiebel (Allium cepa), Stellaria media., Matri-caria matricarioides und Veronica persica war wahrend der ersten 24 h nach der Behandlung schnell, verlief dann bis zum sechsten Tag lang-samer und erreichte einen Maximalwert, der zwischen 35 und 60% der apphzierten Menge lag. Die Unterschiede in der Absorption zwischen den Arten war im allgemeinen gering. Bei der Zwiebel war die Absorption durch die Kotyledonen grosser als durch die Laubblatter. Auf den Blat-tern wurde Methazol zu 3-(3,4-Dichlorphenyl)-l-methylharnstoff (DCPMU) und kleine Men-gen davon zu 3-(3,4-Dichlorphenyl)-harnstoff (DCPU) abgebaut. Methazol. das in die Blatter aufgenommen wurde. war in M. matricarioides relativ stabil und DCPMU akkumulierte nur langsam. Der Abbau verlief in den Kotyledonen schneller als in den Laubblattern. In den Laub-. wie aueh in den Keimblattern der Zwiebel und von S. media, wurde Methazol raseh zu DCPMU abgebaut und reieherte sich dort an. In den Blattern von V. persica wurde DCPMU schnel! zu DCPU und weiteren, nicht identifizierten Pro-dukten verwandelt. Die Menge an akkumulier-tem DCPMU in den Sprossen war weitgehend mit der relativen Phytotoxizitat von Methazol gegenuber den verschiedenen Arten korreliert. Ene Ausnahme hiervon machten die Samlinge von V. persica., die kein DCPMU enthielten. aber gegenuber Methazol empfindlich waren.

Thiazopyr at 0.14, 0.28, and 0.42 kg ai/ha and pendimethalin at 1.1 kg ai/ha applied preemergence (PRE) were compared as components in weed management systems for no-till cotton. Mid- and late-season control of mixtures of large crabgrass, goosegrass, and fall panicum by thiazopyr at 0.28 kg/ha was 89 to 97% and 11 to 50%, respectively, compared with 11 to 38% midseason and 0 to 5% late-season control by pendimethalin. Thiazopyr at 0.42 kg/ha and pendimethalin controlled broadleaf signalgrass 44 and 0%, respectively, late in the season. Adding fluometuron PRE at 1.7 kg ai/ha had little to no effect on large crabgrass, goosegrass, and fall panicum control but increased broadleaf signalgrass control 47 to 79 percentage points compared with thiazopyr or pendimethalin alone. Late-season control of annual grasses by thiazopyr or pendimethalin plus fluometuron PRE followed by methazole plus MSMA early postemergence (POST)-directed and cyanazine plus MSMA late POST-directed was at least 95% at two locations and 80% at the third location. Common lambsquarters was controlled 54 and 95% in systems without and with fluometuron PRE, respectively. Acceptable control of ivyleaf, pitted, and tall morningglories at all locations and smooth pigweed at two of three locations was achieved only in systems with POST-directed herbicides. Adding POST-directed herbicides to systems with thiazopyr or pendimethalin plus fluometuron PRE increased cotton yield at two of three locations. Treatments had no effect on fiber quality.

The potential effect of two sowing dates of ryegrass, Lolium perenne L. var. Elka as an interplant in winter leek, Allium porrum L., on weed control, soil nitrogen allocation and crop yield was studied at two sites in Switzerland. In order to reduce potential competition with the ryegrass, row application of the herbicide methazol (as additional treatment) and increased fertiliser doses in spring (as split-plot treatment) were used, and compared with a weed-free control. Ryegrass was sown 4 weeks (early) and 6 weeks (late) after planting of the leek, allowing for one and two mechanical weed control treatments, respectively, prior to sowing. Under the experimental conditions, intersowing ryegrass 6 weeks after planting resulted in crop yield similar to that in the control plots. Crop quality variates were increased and the overall production system was environmentally more advantageous. The combination of two mechanical weed control treatments followed by ryegrass intersowing suppressed weeds sufficiently without herbicide applications. Approximately 20 kg N/ha could be retained from being washed out over the winter, and c. 50 kg N/ha was stored in the interplants up to harvest. The interplants were incorporated into the soil after the harvest to serve as N-source for the subsequent crop. Surplus fertiliser doses in spring increased N-allocation to leek in the control plots. However, when ryegrass was present, it mainly derived a benefit, resulting in only slightly increased N-allocation to leek, or even reduced allocation when overall N-levels in the soil were low. Depending on soil conditions at harvest, full mechanical harvest could possibly be impeded when ryegrass is present. Early ryegrass sowing resulted in severe yield reductions. Row application of the herbicide methazol reduced crop yield in both ryegrass treatments, most possibly due to a direct negative impact of the high herbicide doses on leek growth.

Field experiments were established to evaluate coffee senna control in cotton with registered PRE, early POST-directed (EPD), and late POST-directed (LPD) herbicides and with pyrithiobac applied PRE and early POST. Fluometuron and norflurazon applied PRE controlled coffee senna 87 and 65%, respectively, 6 wk after planting (WAP). Methazole applied EPD controlled coffee senna 96% 2 wk after application, whereas fluometuron and MSMA applied EPD controlled 70 and 16%, respectively. LPD applications of cyanazine, diuron, and prometryn averaged only 45% control 8 WAP. MSMA applied LPD controlled coffee senna only 12%. Fluometuron and norflurazon applied PRE followed by methazole applied EPD and cyanazine applied LPD controlled coffee senna 98 and 99% 6 WAP, respectively. PRE, early POST, and PRE followed by early POST applications of pyrithiobac controlled coffee senna 88, 89, and 95% 6 WAP, respectively. Seed cotton yields were similar to weed-free cotton with all treatments except MSMA applied EPD and the LPD treatments, all of which provided unacceptable (12 to 49%) control 8 WAP.

Various combinations of methods were evaluated for the control of ivyleaf morningglory growing in cotton. The combinations included chemicals incorporated to two depths or tanked-mixed as postemergence treatments and cultural methods that included in-row cultivation and hand weeding. The most effective combinations of methods included a herbicide such as cyanazine or prometryn in some treatments resulting in reduced ivyleaf morningglory population and improved cotton yields. Cultural methods without chemical assistance gave little or no control of ivyleaf morningglory based on weed populations and cotton yield. Statistically the best combinations had lint yields equal to the weed-free treatment, but the yields were reduced from 114 to 372 kg/ha. Also, most combination treatments had enough plant debris in the lint to reduce fiber grade.

Plant growth regulators (PGRs) [antigibberellins (mepiquat chloride, uniconazole, ancymidol, daminozide, chlormequat, ethephon, methazole), cytokinins (BAP, kinetin, BTP, 2iP), and ABA] were evaluated at various concentrations and timings for promotion of seed trace development and germination of four stenospermic grape cultivars (Vitis spp.): `Venus', `Mars', `Reliance', and `Saturn'. Data include seed trace number per berry, percent of seed traces with endosperm (sinkers), sinker fresh weight, and percent seed trace germination. Several PGRs effectively increased seed number and percent sinkers over control treatments. PGRs had little effect on seed fresh weight and percent germination. PGRs promoted greater increases in percent sinkers than seed number on all cultivars. The number of viable seeds per sample (seed number × percent sinkers) was increased over controls by up to 802% on `Reliance', 239% on `Saturn', 154% on `Mars', and 153% on `Venus'. A moderate percentage of viable seeds from treatments and controls of `Mars', `Venus', and `Saturn' germinated and established normal seedlings. The very small seed traces of `Reliance' did not germinate from either controls or treatments. The results indicate that PGRs can stimulate seed trace formation in some stenospermic cultivars and therefore may be useful tools in grape breeding programs. Chemical names used: abscisic acid (+/-)cis-trans isomer (ABA); a-cyclopropyl-a-(4-methoxy-phenyl)-5-pyrimidinemethanol (ancymidol); 6-benzylaminopurine (BAP); 6-benzylamino-9-(2 tetra-hydropropanyl)-9H-purine (BTP); (2-chloroethyl) trimethyl-ammonium chloride (chlormequat); succinic acid 2,2 dimethyl-hydrazide (daminozide); (2-chloroethyl) phosphonic acid (ethephon); 6-(dimethyl-allylamino) purine (2iP); 6-furfurylaminopurine (kinetin); N,N-dimethyl-piperidinium chloride (mepiquat chloride); [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] (methazole); E-1-(4-chlorophenyl)-4,4-di-methyl-2-(1,2,4-triazol-1-yl)-1-pentan-3-ol (uniconazole).

A study was conducted to evaluate efficacy of 17 PRE herbicides on seven weed species that are important competitors in container-grown ornamentals. Treatments included napropamide, metolachlor, acifluorfen, lactofen, oxyfluorfen, oryzalin, pendimethalin, prodiamine, trifluralin, isoxaben, oxadiazon, simazine and combination products. Control was evaluated by counting weed seedlings 42, 202, and 249 d after treatment. Some treatments provided nearly total control of less than 1.0 seedling per container at each rating over two years. Those treatments were: common groundsel—diphenyl ethers, isoxaben, oxadiazon, oxyfluorfen + oryzalin, and oxyfluorfen + pendimethalin; prostrate spurge—pendimethalin, prodiamine, prodiamine-ABD, trifluralin, oxadiazon, isoxaben + oryzalin, and methazole + prodiamine; common chickweed—isoxaben and isoxaben + oryzalin; hairy bittercress—oxyfluorfen, pendimethalin, prodiamine, prodiamine-ABE, oxadiazon, oxyfluorfen + oryzalin, oxyfluorfen + pendimethalin, and methazole + prodiamine; common ragweed—oxyfluorfen, prodiamine-ABD, methazole + prodiamine; Virginia pepperweed—lactofen, oxyfluorfen, oryzalin, pendimethalin, prodiamine, prodiamine-ABD, isoxaben, oxadiazon, oxyfluorfen + oryzalin, oryzalin + pendimethalin, isoxaben + oryzalin, and methazole + prodiamine; horseweed—oxyfluorfen, dinitroanilines, oxadiazon, oxyfluorfen + oryzalin, oxyfluorfen + pendimethalin, isoxaben + oryzalin, and methazole + prodiamine.

Weed control and cotton yield with a herbicide program of sethoxydim and DPX-PE350 applied postemergence over-the-top was compared with that of a standard herbicide program of trifluralin applied PPI plus fluometuron applied PRE plus methazole and MSMA applied postemergence-directed. Control of pitted and entireleaf morningglory, smooth pigweed, and prickly sida was similar with the postemergence over-the-top program and the standard herbicide program when DPX-PE350 was applied to cotton in the V2 or V4 growth stages. Less weed control and lower yield were observed when DPX-PE350 was applied to V6-stage cotton. Good control of annual grasses was obtained with all herbicide programs. Nomenclature: DPX-PE350, 2-chloro-6-(4,5dimethoxypyrimidin-2-ylthio)benzoate; fluometuron, N,N-dimethyl-N'-[3-(trifluoromethyl)phenyl]urea; methazole, 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione; MSMA, monosodium salt of methylarsonic acid; sethoxydim, 2-[1-(ethoxyimino)butyl]-5-[2(ethylthio)propyl]-3-hydroxy-2-cyclohexen1-one; trifluralin, 2,6-dinitro-N,N-dipropyl-4(trifluoromethyl)benzenamine; entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray #3 IPOHG; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; smooth pigweed, Amaranthus hybridus L. # AMACH; cotton, Gossypium hirsutum L. 'Stoneville 825', 'Stoneville 453', 'Deltapine 50', and 'Arkott 518'. Additional index words: Application timing, fluometuron, methazole, MSMA, trifluralin, Ipomoea hederacea var. integriuscula Gray, Ipomoea lacunosa L., Sida spinosa L., Amaranthus hybridus L., IPOHG, IPOLA, AMACH, SIDSP.

An isocratic normal-phase liquid chromatographic (LC) method for measuring methazole in technical and formulated products was collaboratively studied by 12 laboratories. Samples of technical or formulated products are dissolved in 1,4-dioxane-hexane containing 2-chloro-5-nitrobenzophenone as internal standard. Following centrifugation and further dilution, the sample is analyzed by LC on a 25 cm x 4.6 mm stainless steel column packed with 5 μm silica, with ultraviolet detection at 254 nm. Premixed 1% 2-propanol in hexane is used as the mobile phase. Peak areas are obtained at the retention times corresponding to the internal standard and methazole. The quantity of active ingredient is determined by comparing the area ratio of active ingredient to internal standard in the sample with the same ratio in a single calibration solution. Collaborators were provided with 1 Youden matched pair for each of the technical, 75% wettable granular, and 4 lb/gal flowable products studied. The reproducibility relative standard deviations (RSDR) for the product types studied were 1.05% for technical, 1.80% for granular, and 4.76% for flowable. The method has been adopted first action by AOAC International.

A biotype of rigid ryegrass (Lolium rigidum G. #3 LOLRI) has become resistant to amitrole and atrazine after 10 yr of exposure to a mixture of these herbicides. Resistance has also been demonstrated to the chloro-s- triazines: simazine, cyanazine, propazine; the methylthio- s-triazines: ametryn, prometryn; the substituted ureas: chlortoluron, isoproturon, metoxuron, diuron, fluomet- uron, methazole; and the triazinone herbicide metribuzin. The biotype remains susceptible to chlorsulfuron, metsul- furon, sulfometuron, sethoxydim, diclofop, fluazifop, gly- phosate, carbetamide, and oxyfluorfen. Inhibition of oxygen evolution by atrazine, diuron, and metribuzin was similar in thylakoids isolated from both resistant and susceptible biotypes. Therefore, resistance to the pho- tosystem II inhibitors is not caused by an alteration of the target site of these herbicides. Resistant plants treated with a 3-h pulse of 0.12 mM chlortoluron recover photosynthetic activity more rapidly than susceptible plants. This suggests that the basis for resistance is enhanced metabolism or sequestration of the herbicide within the leaf. Nomenclature: Ametryn, N-ethyl-N'-(1- methylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine; amitrole, 11I-1,2,4-triazol-3-amine; atrazine, 6-chloro-N- ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine; car- betamide, (R)-N-ethyl-2-(((phenylamino)car- bonyl)oxy)) proponamide; chlorsulfuron, (2-chloro- N-(((4-methoxy-6-methyl-1,3,5-triazin-2- yl)aminolcarbonyl)benzenesulfonamide); chlortoluron, N'- (3-chloro-4-methylphenyl)-N,N-dimethylurea; cyan- azine, 2-(14-chloro-6-(ethylamino)-1,3,5-triazin-2- yl)amino)-2-methylpropanenitrile; diclofop, (?)-2-(4-(2,4- dichlorophenoxy)phenoxy)propionic acid; diuron, N'-(3,4- dichlorophenyl)-N,N-dimethylurea; fluazifop, (?)-2-(4-((5- (trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propionic acid; fluometuron, N,N-dimethyl-N'-(3-(trifluoro- methyl)phenyl)urea; glyphosate, N-(phosphonomethyl)gly- cine; isoproturon, N,N-dimethyl-N'-(4-(1- methylethyl)phenyl)urea; methazole, 2-(3,4-dichlorophen- yl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione; metoxuron, N'-(3-chloro-4-methoxyphenyl)-N,N-dimethylurea; metrib- uzin,-amino-6-(1,-dimethylethyl)-3-(methylthio)-1,2,4

Summary. A range of herbicides and combinations of herbicides were evaluated for controlling nutgrass (Cyperus rotundus L.) in 5 experiments in irrigated cotton in northern New South Wales. Control was assessed by comparing the density of tubers before and after treatment. Cotton lint yield and ginning percentage were also assessed. Combinations of herbicides, including 2,4-D, were evaluated in an additional experiment in fallow. Multiple in-crop applications of glyphosate reduced tuber density by up to 96% over 2 seasons. This was improved with successive applications of glyphosate. Nutgrass tuber density was also reduced when glyphosate was combined with norflurazon (96%), benfuresate (92%), fluometuron (84%) or EPTC (87%). Similar reductions in nutgrass density were observed with methazole, dimethenamid, atrazine, and the combination of norflurazon + MSMA. Treatments which reduced nutgrass density generally resulted in average or above-average lint yields. From these results, a strategy for controlling nutgrass in cotton can be developed using norflurazon preplanting, and multiple applications of glyphosate and/or MSMA in-crop.

Six prodiamine treatments, three applied alone and three applied in combination with methazole, were compared with oxyfluorfen/oryzalin, oxadiazon, and controls (weeded and non-weeded) on ornamental and weed species. Ornamentals included green liriope, Asiatic jasmine, serissa, gardenia, `Needlepoint' holly, Japanese yew, `Prostrata' juniper, and `Carror' azalea. Weeds grown in separate containers were goosegrass, crabgrass, pigweed, and prostrate spurge. At 13 days after treatment (DAT), oxadiazon and oxyfluorfen/oryzalin caused some contact burn on liriope, and the injury persisted until the 81 DAT rating. Methazole/prodiamine treatments caused chlorosis on gardenia leaf tips, with plants recovering by 61 DAT. These combinations also resulted in slight injury to azalea at the first rating, but the injury disappeared by the second rating. Control of goosegrass, crabgrass, and pigweed was good to excellent with all chemical treatments. Control of spurge using oxadiazon and oxyfluorfen/oryzalin decreased at 81 and 100 DAT.

Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine -3,5 -dionel , metribuzin [4-amino -6-tert -butyl -3 -(methyl thio) -as -triazin -5 (4H) -one] , and combinations of MSMA (monosodium methanearsonate) with either methazole or metribuzin were applied to bare ground at 0, 1, 2, and 4 weeks before planting with bermudagrass [Cynodon dactylon (L.) Pers. 'Common'] as sprigs, stolons, and seed. In most instances, the growth of newly planted bermudagrass was as good or better from combination of MSMA (2.2 kg/ha) with either methazole or metribuzin at 0.1 kg/ha than with methazole or metribuzin applied alone at higher rates. MSMA + methazole can be applied safely on day of planting with sprigs and seed, but a 1 -week interval between treatment and planting was needed with stolons in 1 of 2 yr. The MSMA + metribuzin combination can also be applied safely to sprigged bermudagrass on day of planting, but a 1 -week interval was needed between treatment and planting with stolons and a 2-week interval between treatment and planting with seed to insure minimum bermudagrass injury. Additional index words. Sprigs, stolons, seed, turf growth, methods of planting, methazole, metribuzin, MSMA, dates.

[14C]-Labelled methazole was incubated in six soils at 25°C and with soil moisture at field capacity. Under these conditions, methazole was unstable, the concentration declined following first-order kinetics with half-life values in the soils ranging from 2.3 to 5.0 days. The main degradation product was 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) which was more stable than the parent compound. After about 160 days, DCPMU accounted for 30 to 45% of the initial methazole concentration. Degradation of methazole and DCPMU was affected by soil temperature and moisture content. With methazole, half-lives in one soil at field capacity moisture content and temperatures of 25, 15 and 5°C were 3.5, 8.7 and 31.1 days respectively. The half-life at 25°C was increased to 5.0 days at 50% of field capacity and 9.6 days at 25% of field capacity. A proportion of the initial radioactivity added to the soil could not be extracted and this proportion increased with time. After 160 days this unextractable radioactivity accounted for up to 70% of the amount applied.

Translocation of the14C-labeled methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] was determined in cotton (Gossypium hirsutumL. ‘DPL 16′) from preemergence treatments and applications to leaves and stems in the field. Significantly greater methazole concentrations occurred in cotton from treatments to stems of 18 to 22-cm tall cotton than to leaves of 10 to 12-cm tall cotton or when applied preemergence. The radiolabel translocated primarily into the mature stems and leaves with lesser amounts translocating into the roots. Little14C moved into the young growing points or into the seed and fiber of mature cotton. The distribution pattern of the14C-label is characteristic of compounds which move primarily in the apoplast.

Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] were evaluated in separate experiments for postemergence control of large crabgrass [Digitaria sanguinalis(L.) Scop.] and goosegrass [Eleusine indica(L.) Gaertn.] and on tolerance of centipedegrass [Eremochloa ophiuroides(Munro) Hack.], St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze], and bermudagrass [Cynodon dactylon(L.) Pers. ‘Common’]. Methazole was also evaluated on tolerance of Kentucky bluegrass (Poa pratensisL. ‘Common’). Metribuzin applied at 0.6 kg/ha and methazole at 1.1 kg/ha as single treatments controlled 82 and 87% goosegrass, respectively. Repeated treatments were needed for similar control of large crabgrass. These treatments did not permanently injure bermudagrass or centipedegrass. St. Augustinegrass was severely injured when treated with single applications of methazole at 1.1 kg/ha or metribuzin at 0.6 kg/ha while Kentucky bluegrass was severely injured by methazole applied at any rate. Methazole caused moderate to severe injury to bermudagrass when applied at 2.2 kg/ha in each of two applications and to centipedegrass when applied at 4.4 kg/ha in each of two applications.

Summary: Methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] was applied post-emergence at 2-1 kg/ha to crops of onion (Allium cepa L.) grown on a sandy loam and the activity present in the surface 0–5 cm of soil assessed by bioassay. In spring-sown crops, activity at harvest varied from 25 to 78% of the initial acitivity in different years; losses were restricted by low temperature and low rainfall. In autumn-sown crops, little loss occurred during winter and most of the activity remained in the surface 0-5 cm. The results emphasize the need for caution in choice and timing of following crops. Resume: Persistance de I'aciiviti du meihazole dans le sol Le methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] a ete applique en postlevee a 2,1 kg/ha sur des cultures d'oignons (Allum cepa L.) poussant sur un limon sableux; l'activite presente dans les 5 premiers centimetres du sol a ete mise en evidence par un essai biologique. Dans des cultures semees au printemps, l'activitea la recolte a varie, au cours de differentes annees, de 25 a 78% de l'activite initiale. Les pertes ont ete limitees par des temperatures basses et une pluviosite faible. Dans des cultures semees en automne, il n'y eut que peu de pertes pendant l'hiver et la plus grande part de l'activite est restee localisee dans la couche 0–5 cm. Les resultats metlent l'accent sur la necessite de choisir avec prudence l'espece cultivee suivante et sa date d'implantation. Zusammenfassung Die Persistenz der Aktivitdt von Meihazol im Boden Methazol [2-(3,4-Dichlorphenyl)-4-methyl-1,2,4-oxydiazolidin-3,5-dion) wurde mit 2,1 kg/ha im Nachaullauf in Zwiebeln (Allium cepa L.) auf sandigem Lehm angewendet und die Herbizidaktivitat in der Bodenschicht von 0–5 cm mit einem Biotest festgestellt. Zum Zeitpunkt der Ernte betrug die Herbizidaktivitat in den im Fruhjahr gesaten Kulturen in verschiedenen Jahren zwlschen 25 und 78% der Anfangsaktivitat. Das Abklingen der Herbizidaktivitat wurde durch niedrige Temperaturen und mangelnde NiederschlSage verzogert. In im Herbst gesaten Kulturen war der Herbizidverlust wahrend des Winters gering und der grosste Teil des Herbizids beschrfankte sich auf die oberen 5 cm. Die Ergebnisse weisen nachdrucklich darauf hin, dass Wahl und Zeitpunkt der nachfolgenden Kulturen mit Vorsicht getroffen werden mussen.

The differential tolerance of prickly sida (Sida spinosaL.) and cotton (Gossypium hirsutumL.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione]was studied under greenhouse conditions. Methazole at dosages up to 8.96 kg/ha did not affect emergence of either species. Applications via nutrient solution, as well as preemergence and postemergence (over-the-top) treatments were phytotoxic to both species, becoming more pronounced with increasing concentration and time. However, a margin of selectivity between species occurred at dosages from 0.56 to 3.36 kg/ha preemergence. Directed sprays of methazole were not injurious to cotton. Selectivity would be influenced by plant size and method of application as well as biochemical differences between species.

The degradation and leaching of methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and metabolites in Elmwood sandy loam soil over time in response to average spring environmental conditions was studied by using soil columns placed on a rainfall simulator in an environmental growth chamber. Methazole was degraded to 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU) and 3-(3,4-dichlorophenyl) urea (DCPU) over a 6-week period following methazole application, during which the soil columns received simulated rainfall of 1.27 cm every fourth day. Methazole level decreased to 27% of the original amount while DCPMU and DCPU levels increased to 53% and 1%, respectively. Of the total radioactivity remaining in the soil columns after 44 days and after 14 cm rainfall, approximately 80% remained above a depth of 6.35 mm.

Summary: A simple extraction method with water is described which allows the quantitative determination, within 1 day of the residues of soil-applied herbicides which are potentially available to plants. The validity of this method has been examined with a growth test using Brassica rapa in soils containing residues of different ages. Resume: La partie des residus d'herbicides disponible pour les plantes dans le sol. Partie I: Une methode rapide pour la determination de la partie active et potentiellement disponible pour les plantes des residus d'herbicides dans le sol. Une methode simple est decrite basee sur l'extraction du sol au moyen d'eau et qui permet de determiner dans une journee la quantite de residus potentiellement disponible et active La preuve de la surete de cette methode est fournie par un biotest avec des jeunes plants de Brassica rapa dans des sols qui contiennent des residus d'âges differents. Zusammenfassung Pflanzenverfugbarkeit von Herbiziden im Boden. Teil I: Eine Schnellmethode fur die Bestimmung des potentiell pflanzenverfugbaren Anteils von Herbiziden im Boden. Es wird eine einfache Extraktionsmethode mit Wasser beschrieben, die es erlaubt, innerhalb eines Tages den potentiell pflanzenaktiven, pflanzen verfugbaren Anteil von Boden-Herbiziden quantitativ zu erfassen. Die Zuverlassigkeit dieser Bestimmungsmethode wird durch einen Wachstumstest mit Herbstrubenkeimlingen (Brassica rapa) in Boden mit unterschiedlich alten Ruckstanden erbracht.

Com a finalidade de estudar a ação dos herbicidas oxadiazon, napropamide, methazole e A-3587 na cultura de cana -de-açúcar (Saccharum sp), foram conduzidos em 1971/72 dois ensaios de campo nos municípios paulistas de Capivari e Leme. Os herbicidas acima citados foram comparados, em trés doses, com 2,4-D anina e atrazine, aplicados em pré -emergência. Oxadiazon a 2,0 kg/ha e A-3587 a 3,0 kg e 4,0 kg/ha foram eficientes no controle das principais plantas daninhas que apareceram nos experimentos: capim-marmelada, Brachiaria plantaginea (Link) Hitch; capim-de-colchão, Digitaria sanguinalis (L.) Scop; capim-pé-degalinha, Eleusine indica (L.) Gaertn.; beldroega, Portulacca oleracea L e guanxumas, Sida spp. Napropamide a 3,0 kg/ha e methazole a 3,5 kg e 4,0 kg/ha só não con trolaram as guanxumas. Nas doses empregadas, nenhum dos herbicidas mostrou-se prejudicial às plantas e à produção de cana-de-açúcar. This paper reports on two field trials carried out during 1971/72, in Capivari and Leme, with the herbicides oxadiazon, napropamide, methazole and A-3587, in sugar-cane crops. In these experiments the four herbicides, in three doses, were compared, in preemergence, with 2,4-D amine and atrazine. Oxadiazon at 2.0 kg/ha and A-3587 at 3.0 kg and 4,0 kg/ha gave good control against Brachiaria plantaginea, Digitaria sanguinalis, Eleusine indica, Portulacca oleracea and Sida spp, wich were found in the trials. Napropamide at 3.0 kg/ha and methazole at 3.5 kg and 4.0 kg/ha gave good control against those weeds but except Sida spp. None of the herbicides caused injuries to the crop or reduced yield.

The health effects of two pesticides, chlordimeform and propanil, are discussed. Chlordimeform and 2‐methyl‐4‐chloroaniline, a major metabolite of chlordimeform, cause severe hemorrhagic cystitis in humans. In cats, however, only a mild effect on the bladder was noted. The herbicide propanil has produced chloracne in humans, and along with 3,4‐dichloroaniline, hyperkeratosis in rabbits. The contaminants 3,4,3’,4'‐tetrachloroazobenzene and 3,4,3’,4'‐tetrachloroazoxybenzene are responsible for the chloracnegenic characteristics of propanil, 3,4‐dichloroaniline, and methazole.

Effects of methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and of its plant degradation products, DCPMU [3-(3,4-dichlorophenyl)-1-methylurea] and DCPU [3-(3,4-dichlorophenyl)urea], on photosynthesis, protein synthesis, ribonucleic acid (RNA) synthesis, and lipid synthesis of enzymatically isolated leaf cells of velvetleaf (Abutilon theophrasti Medic) were compared. Photosynthesis and protein, RNA, and lipid synthesis were assayed by the incorporation of NaH14CO3, [14C]-leucine, [14C]-uracil, and [14C]-acetate, respectively, into the isolated cells. Time-course and concentration studies included incubation times of 30, 60, and 120 min and concentrations of 0.1, 1, 10, and 100 μM of all three chemicals. DCPMU was a more potent inhibitor of the four metabolic processes examined than either the parent herbicide methazole or DCPU. The sensitivity of the four metabolic processes to DCPMU decreased in the order: photosynthesis>lipid>RNA >protein synthesis. Inhibition of all metabolic processes by methazole was time-dependent, increasing in magnitude with concomitant increases in incubation time. It is probable that the observed effects of methazole were caused by DCPMU, formed through metabolism of methazole by the isolated leaf cells of velvetleaf rather than by methazole itself. DCPU was less active than the parent herbicide methazole and DCPMU and seems to be a terminal metabolite of methazole with limited phytotoxicity.

Putting green turf containing perennial ryegrass (Lolium perenne L. 'Medalist IV') overseeded on a ber- mudagrass (Cynodon dactylon (L.) Pers. 'Tifway') was treated with single and sequential herbicide treatments during the spring and transition period from cool to warm season grass. Oxadiazon (2-tert-butyl442,4-dichloro-5-isopropoxyphenyl)- A2_1,3,4-oxadiazolin-5-one) at 2.2 or 4.4 kg/ha and butralin (4-( 1, 1 -dimethylethyl)-N4 1-methylpropyl)-2,6-dinitroben- zenamine) at 3.4 or 6.7 kg/ha reduced the quality of putting green turf immediately after treatment in early spring. Turf injury was greater with oxadiazon than with butralin. Two applications of MSMA (monosodium methanearsonate) at 2.2 or 3.4 kg/ha resulted in a lower quality turf with less ryegrass when compared with the untreated check. Methazole (2-( 3 ,4-dichloro phenyl)-4-methyl-1 ,2,4-oxadiazolidine-3,5- dione) at 1.1 kg/ha severely injured ryegrass and resulted in a lower turf quality. Most herbicides now used to control summer weeds in ber- mudagrass turf injure the cool-season species used to overseed bermudagrass greens during the winter. Since injury is not de- sirable on overseeded bermudagrass greens, studies are required to evaluate herbicides which can be applied during the spring and transitional season for weed control. This transitional period refers to the change of ryegrass turf back to bermuda- grass turf. This study was conducted to determine the effects of rate and frequency of herbicide applications on tolerance of overseeded perennial ryegrass on bermudagrass turf and the effects of these treatments on both grasses during the transi- tion period.

[14C]-Labelled methazole, 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU), 1-(3,4-dichlorophenyl)urea (DCPU), and diuron were incubated in soil at 20°C and field capacity soil moisture content. Decomposition followed first-order kinetics; half-lives for degradation of these four compounds were 2.4, 144, 30 and 108 days respectively. The amount of DCPMU and DCPU that could be extracted decreased with time and the decrease was accompanied by the generation of an equivalent amount of 14CO2. This was not so in the studies with diuron and methazole, however, and the decrease in the concentrations of radioactivity extracted from soil treated with these compounds could not be entirely accounted for as carbon dioxide. It is concluded that the unextractable radiochemical that was present was DCPMU. Methazole appeared to be degraded through DCPMU to 3,4-dichloroaniline (DCA) with the production of only traces of DCPU.

Summary: The responses of onion (Allium cepa). Veronica persica, Matricaria matricarioides and Stellaria media to post-emergence applications of methazole were measured in field and glasshouse experiments. Stellaria media was the most susceptible species and V. persica the least. Plants of all species became more tolerant the larger they were at the time of treatment, and this was most pronounced in onion. Onion generally retained less spray per unit of dry weight than the other three species and retention was less on old compared with young plants, whereas with the weed species, this did not change appreciably with age. There was a progressive increase in the amount of structured crystalline wax on successive onion leaves which resulted in larger contact angles between droplets and the leaf surfaces and lower spray retention per unit of dry weight. There was less wax development on the leaf surfaces, increased spray retention, and increased susceptibility to methazole in onion treated pre-emergence with ethofumesate thus confirming that these factors are interrelated. While the increased tolerance of onion to methazole with age could be explained in part by decreased retention of herbicide, this was not so for the weed species, and other factors must determine their change in tolerance with age. Resume: Aspects de la phytotoxicite du methazole. I. Evaluations des reactions des vegetaux traitees et de la fixation de la bouillie sur les feuilles en fonction de leurs caracteristiques Les reactions de l'oignon, de Veronica persica, Matricaria matricarioides et Stellaria mediaa des applications de methazole ont eteevaluees au champ et en serre. Stellaria mediaetait l'espece la plus sensible et V. persica celle qui l'etait le moins. Toutes les especes resistent d'autant mieux qu'elles etaient plus developpees lors du traitement, ceci etant particulierement notable pour l'oignon. L'oignon retient moins de bouillie par unite de surface que les trois autres especes et la retention de produit est plus faible sur les plantes adultes que sur les jeunes plantes, par opposition aux adventices ou ce caractere change tres faiblement avec l'âge. Il y a une augmentation progressive de l'epaisseur de cire de structure cristalline sur la feuille d'oignon, ceci entrainant: (1) un accroissement des angles de contact des gouttes sur le feuille et (2) une diminution de la retenue de bouillie par unite de poids sec. Sur des oignons traites a l'ethofumesate en prelevee, l'epaisseur de cire, a la surface de la feuille, est moindre, la retention de bouillie augmente et, en consequence, la sensibilite au methazole augmente egalement confirmant ainsi qu'il existe une correlation entre ces caracteres. Alors que l'augmentation de la resistance de l'oignon au methazole peut etre partiellement expliquee par la diminution de la retention de l'herbicide, ceci ne peut etre invoque pour les adventices et d'autres facteur doivent etre invoques pour les adventices el d'autres facteurs doi-vent etre etudies pour expliquer la variation de la tolerance avec Page. Zusammenfassung Aspekte zur selektiven Phytotoxizitat von Metha-2ol. I. Reaktion von Pflanzenarten, Retention der Spritzbruhe und Blattoberfldchencharakteristika Es wurde die Reaktion von Zwiebein, Veronica persica. Matricaria matricarioides und Stellaria nift/iaauf Nachauflaufbehandlungen mit Metha-zol in Feld- und Gewachshausversuchen gepruft. Stellaria media war die empfindlichste und V. persica die am wenlgsten empfindliche Art. Alle Pflanzenarten wurden umso toleranter, je grosser sie zum Zeitpunkt der Behandlung waren, und dies war bei der Zwiebel besonders ausgepragt. Bezogen auf das Trockengewicht, wurde von den Zwiebein im allgemeinen weniger Spritzbruhe reteniert als von den anderen drei Arten, und die Retention war bei alten Pflanzen geringer als bei jungen. wogegen bei den Unkrautern das Alter eine geringere Rolle spielte. Bei den nachfol-genden Zwiebelblattern war eine standige Zunahme an strukturiertem krislallinen Wachs zu beobachten. was einen grosseren Kontaktwin-kel zwisehen den Tropfchen und der Blattober-flache zur Folge hatte und, bezogen auf das Trockengewicht, mit einer geringeren Briihere-tention verbunden war. Eine geringere Wachsbil-dung, zunehmende Bruheretention und zuneh-mende Empfindlichkeit gegenuber Methazol waren zu beobachten, wenn die Zwiebein im Vor-auflauf mit Ethofumesat behandelt waren. wodurch bestatigt wird, dass sich diese Faktoren gegenseitig bedingen. Wahrend die zunehmende Toleranz alterer Zwiebel gegeniiber Methazol sich teilweise mit einer geringeren Herbizid-retention erklaren lasst, trifft dies aber fur die Unkrautarten nicht zu. Hier mussen dann im Alter noch andere Faktoren die Toleranz veran-dern.

Combinations of MSMA (Monosodium methanearsonate) with either methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were applied at various rates for postemergence control of fully developed goosegrass [Eleusine indica(L.) Gaertn.], a major weed grass in bermudagrass [Cynodon dactylon(L.) Pers.] turf. Two applications of MSMA at 2.24 kg/ha applied in combination with either methazole or metribuzin at 0.14 kg/ha controlled 96 to 98% of the goosegrass and it was as effective as methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) applied alone. Two applications of methazole (1.12 kg/ha) or metribuzin (0.56 kg/ha) had lower quality ratings (28 and 39, respectively) on bermudagrass putting green at 2 weeks after treatment than combinations of MSMA (2.24 kg/ha) with either methazole (0.14 kg/ha) or metribuzin (0.14 kg/ha) (54 and 59, respectively). The initial injury from combination treatments was not severe and turf recovered within 3 to 4 weeks.

Germination studies on camphorweed [Heterotheca subaxillaris(Lam.) Britt. & Rusby] revealed that freshly harvested disk achenes germinated best at 17.5 C (88%) while ray achenes were dormant. Camphorweed seed from disk achenes also germinated at temperatures as low as 3 C. Seedlings grown under long-day conditions at 23 C day and 8 C night temperatures for 144 days elongated at the rate of 0.18 cm/day. Plants grown under short-day conditions at the same temperature regime elongated at the rate of 0.06 cm/day. Total leaf surface area, fresh weight, and dry weight of shoots of plants grown under long days were at least 1.5 times greater than plants grown under short day conditions. Camphorweed, regardless of size and age, survived a 2-h exposure at −5 C. All plants in the rosette stage survived at −15 C in the freezer and an overnight temperature of −11.7 C in the field, whereas larger plants were killed at these temperatures. Stage of growth was an important factor in the herbicidal control of camphorweed. Plants in the rosette stage were generally more susceptible to herbicides than older plants. Simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 3.4 kg/ha, paraquat (1,1′-dimethyl-4,4′-bypyridinium ion) at 0.6 kg/ha, methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] at 5.0 kg/ha, and a formulated mix of diuron [3–3,4-dichlorophenyl)-1,1-dimethylurea] and terbacil (3-tert-butyl-5-chloro-6-methyluracil) at 4.5 kg/ha provided adequate control of camphorweed in the rosette stage. Asulam (methyl sulfanilylcarbamate) at 2.2 or 4.5 kg/ha applied alone did not control camphorweed in the rosette form but was more effective on older plants. Various combinations of these herbicides were generally effective at both stages of growth.

Broadleaf weeds continue to be a major problem in turfgrass during mild winters throughout the Southeast. Therefore, experiments were conducted with herbicides applied postemergence to determine the maximum weed control with the least amount of chemical treatment. Two new herbicides alone with presently available chemicals were applied to dormant bermudagrass [Cynodon dactylon L. Pers.] in singly and repeatedly at 1 and 2✕ rates at three locations. Soil types were Cecil sl (Typic Hapludult), Durham scl (Typic Haludult), Gwinnett scl (Typic Rhodudult), and Pacolet-Wickham sl (Typic Hapludult). Parsley-piert (Alchemilla microcorpa Boissier Reuter) was completely controlled with single treatments of methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] and cisanilide (cis-2,5-dimethyl-N-phenyl-1-pyrrolidinecarboxamide) while two applications were required to obtain satisfactory control with silvex [2-(2,4,5-trichlorophenoxy)propionic acid], paraquat (1,1'-dimethyl-4,4'-bipyridinium ion), dicamba (3,6-dichloro-o-anisic acid), and combination treatments of 2,4-D [(2,4-dichlorophenoxy)acetic acid] with either dicamba, silvex + dicamba, or mecoprop {2[(4-chloro-otolyl)oxy]propionic acid} + dicamba. Paraquat resulted in excellent corn speedwell (Veronica arvensis L.) control with a single treatment, but two applications were required for similar control with cisanilde or methazole. Two applications were generally required of 2,4-D, silvex, dicamba and the two and three combination treatments for satisfactory corn speedwell control, especially in plots treated with 1✕ rates. All the herbicides gave good to excellent henbit (Lamium amplexicaule L.) and common chickweed [Stellaria media (L.) Cyrillo] control except for 2,4-D when applied to henbit at the 1✕ rate.

The mechanisms for the tolerance of purple nutsedge (Cyperus rotundus L.) and susceptibility of yellow nutsedge (Cyperus esculentus L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were studied. Both species absorbed and translocated[14C]methazole and metabolites from nutrient solution; however, greater amounts of 14C per unit weight were detected in yellow than in purple nutsedge. Although intact plants and excised leaves of both species rapidly metabolized methazole to DCPMU [1-(3,4-dichlorophenyl)-3-methylurea], detoxification of DCPMU to DCPU [1-(3,4-dichlorophenyl) urea] occurred more slowly in yellow than in purple nutsedge. Compared to yellow nutsedge, a greater percentage of the radioactivity in purple nutsedge was recovered as polar products. Polar products were converted to the free forms of the parent herbicide and to phytotoxic DCPMU by proteolytic enzyme digestion. Based on the findings of this study, at least three mechanisms (differential absorption, metabolism, and formation of polar products) account for the differential tolerance of these two species to methazole.

Single and repeated applications of MSMA (monosodium methanearsonate) with and without 2,4-D [(2,4-dichlorophenoxy)acetic acid], metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one], and methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-di-one] were evaluated for control of large crabgrass (Digitaria sanguinalis L. Scop.) and goosegrass (Eleusine indica L. Gaertn.). Large crabgrass was controlled satisfactorily at Griffin in 1972 and 1973 with a single application of 1.7 kg/ha of MSMA, however, repeated applications were required for similar control at Griffin in 1974 and at Blairsville in 1973 and 1974. Repeated treatments at 0.6 kg/ha resulted in satisfactory large crabgrass control in only 2 of 3 years at Griffin and 1 of 3 experiments at Blairsville. The optimum time interval between the first and second MSMA treatments (average 1973 and 1974) was 12 days for the 1.1 kg/ha rate and anytime between 12 and 19 days for the 1.7 and 2.2 kg/ha rates. There was no advantage in large crabgrass control from treatments of methazole, metribuzin, or combinations of MSMA + 2,4-D when compared with MSMA. Single applications of 1.1 kg/ha of metribuzin or 2.2 kg/ha of methazole resulted in excellent goosegrass control without causing any permanent injury to common bermudagrass [Cynodon dactylon (L.) Pers.]. Repeated treatments of 3.3 kg/ha of MSMA were required to obtain satisfactory goosegrass control.

Adsorption and desorption of14C-methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] were characterized on two silt loam soils (Dundee and Palouse; 0.7 and 3.0% organic matter, respectively) using the batch equilibration technique. Freundlich adsorption isotherm coefficients (Kfand l/n) were calculated after equilibration of methazole solutions (initial concentrations = 0.11 to 4.10 nmol/ml) with soil for various times. After a rapid attainment of an apparent equilibrium,14C- concentration in solution for the Palouse soil decreased at a low rate. The greater adsorption (Kf) on the Palouse soil, for a given equilibration period, was attributed to the greater organic matter content. The continued trend of increase in apparent Kfwith time was due to degradation of methazole in solution to 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU), which was highly adsorbed, rather than to increased adsorption of the parent compound. The calculated adsorption coefficients expressed in terms of soil organic carbon would classify methazole and DCPMU as immobile in Palouse soil and methazole as slightly mobile in Dundee soil. Calculated desorption isotherms, which exhibited a hysteretic effect, were also dependent on the rate of methazole degradation. The adsorption, desorption, and degradation data indicate that methazole would not leach readily in most soils.

The absorption and translocation of14C-labeled α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione methazole from nutrient solutions of various temperatures by(Arachis hypogaeaL. ‘Starr’) seedlings were determined. The accumulation of trifluralin in roots at 24 hr after exposure to trifluralin was greatest at 21 C and decreased at higher temperatures up to 38 C. The amounts of trifluralin translocated and accumulated in hypocotyls, tops, and cotyledons were small but generally increased with temperature. The initial rate of absorption of trifluralin was greater in excised lateral root tips than in tap root tips, but there was a greater accumulation in excised tap roots at 24 hr. The initial rates of absorption were higher for excised lateral roots at high temperatures. Total absorption of trifluralin at equilibrium was not proportional to the initial rates of absorption but was highest at low (21 C) and high (38 C) temperatures for excised lateral roots. The absorption of methazole by roots and translocation to other plant parts increased linearly with temperature, and it tended to accumulate in the mature leaf tissue.

The metabolic fate of the 14 C-labeled herbicide, 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone), in cotton ( Gossypium hirsutum L. “Acala 4-42-77”) was studied using thin-layer chromatography, autoradiography, and counting. Bioxone- 14 C was readily metabolized by cotton tissue to 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) and 1-(3,4-dichlorophenyl)urea (DCPU). Leaf discs metabolized bioxone- 14 C rapidly; 12 hr posttreatment, 65% of the 14 C in methanol extracts was in forms other than intact herbicide. Excised leaves treated through the petiole with either heterocyclic ring-labeled or phenyl ring-labeled herbicide contained little bioxone- 14 C after 1 day; DCPMU was formed early then decreased with time. DCPU accounted for 55–70% of the 14 C in excised leaves 3 days posttreatment. In intact plants treated via the roots, the herbicide was rapidly metabolized in the roots to DCPMU and DCPU; little or no intact herbicide was translocated to the leaves. Little radioactivity accumulated in the roots with time; the radioactivity in the leaves accounted for 80–90% of the methanol-soluble 14 C 47 days posttreatment. Most of the 14 C in the leaves was recovered as DCPU (50–60%) and unidentified polar metabolite(s) which remained at the origin of the thin-layer plates (30–40%). The percentage of radioactivity which remained in cotton residue after methanol extraction increased with time. Digestion of the plant residues with the proteolytic enzyme pronase indicated that some of the nonextractable 14 C may be DCPMU and DCPU complexed with proteins. Similar metabolic patterns were noted after treatment with either heterocyclic ring-labeled or phenyl ring-labeled bioxone- 14 C. Generally, bioxone was metabolized to DCPMU which in turn was demethylated to DCPU. The herbicide and DCPMU were 20 times as toxic as DCPU to oat ( Avena sativa L.), a susceptible species.

An infrared method was developed for the analysis of Probe 75% wettable powder formulation for methazole content. The procedure involves an extraction of the powder by agitation with acetone. The suspension is centrifuged, and the clear supernatant liquid is measured for absorbance at 755 cm−1. A collaborative study was conducted with 10 laboratories participating. One laboratory omitted the centrifugation, which resulted in a low assay. Statistical analysis of the data showed no significant variances. The coefficient of variation for 10 laboratories analyzing 2 samples in duplicate was 1.29%. The method has been adopted interim official first action.