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

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

THE SYNERGISTIC ACTION OF HERBICIDE COMBINATIONS CONTAINING PARAQUAT ON AGROPYRON REPENS (L.) BEAUV.*

Summary. Herbicide combinations containing paraquat were synergistic and provided control of established Agropyron repens (L.) Beauv. (quackgrass) sods for the entire growing season. Paraquat applied at 0–5 lb/ac with simazine or diuron at 4–0 lb/ac was more phytotoxic than either herbicide applied singly and the enhanced activity was more than additive. This synergism was not due to increased absorption or translocation of either herbicide in aerial portions of the plant. Paraquat applied to the shoot increased the susceptibility of quackgrass to simazine action through the soil. Pre-treatment of quackgrass with aminotriazole or amitrole-T at 10 lb/ac 7 days before paraquat application at 0–5 lb/ac provided increased toxicity over that obtained when the two herbicides were applied together or singly. Subsequent studies indicated that aminotriazole applications prior to shoot destruction by either paraquat or clipping resulted in more chronic aminotriazole toxicity. Using methyl-¹⁴C-paraquat it was found that aminotriazole pre-loading also increased the movement of paraquat in and out of the treated leaf. This increase was even more pronounced with amitrole-T. When the two herbicides were applied together, antagonism in absorption and translocation occurred. Action synergique de combinaisons d'herbicides comprenant du paraquat sur Agropyron repens (L.) Beauv.     

Studies on the mode of action of asulam,aminotriazole and glyphosate in Equisetum arvense L. (field horsetail). I: The uptake and translocation of [14c]asulam, [14C]aminotriazole and [14C]glyphosate

The uptake and translocation of [¹⁴C]asulam (methyl 4-aminophenyl-sulphonylcarbamate), [¹⁴C]aminotriazole (1-H-1,2,4-triazol-3-ylamine) and [¹⁴C]glyphosate (N-(phosphonomethyl)glycine) were assessed in Equisetum arvense L. (field horsetail), a weed of mainly horticultural situations. Under controlled-environment conditions, 21°C day/18°C night and 70% r. h., the test herbicides were applied to 2-month-old and 2-year-old plants. Seven days following the application of 0.07-0.09 °Ci (1.14mg) of the test herbicides to young E. arvense, the accumulation of ¹⁴C-label (as percentage of applied radioactivity) in the treated shoots, untreated apical and basal shoots was as follows: [¹⁴C]asulam, 13.2, 0.18 and 1.02%; [¹⁴C] aminotriazole, 67.2, 3.65 and 1-91%; [¹⁴C]glyphosate, 35.9, 0.06 and 0.11%. The equivalent mean values for the accumulation of ¹⁴C-label in 2-year-old E. arvense were [¹⁴C]asulam, 12.0, 1-15 and 1.74%; [¹⁴C]aminotriazole, 58.6, 9.44 and 4.12%; [¹⁴C]glyphosate, 33.1, 0.79 and 2.32%. In the latter experiment, test plants received 0.25-0.30 °Ci (4mg) of herbicide, they were assessed after a 14-day period and the experiment was carried out at 3-week intervals between 2 June and 25 August on outdoor-grown plants. Irrespective of test herbicide or time of application, very low levels of ¹⁴C-label accumulated in the rhizome system. Only 0.2% of the applied radioactivity was recovered in 2-year-old plants and 0.4% in 2-month-old plants. In the young plants [¹⁴C]asulam accumulated greater amounts and concentrations of ¹⁴C-label in the rhizome apices and nodes than [¹⁴C]aminotriazole or [¹⁴C]glyphosate treatments. Inadequate control of E. arvense under field conditions may be due to limited basipetal translocation and accumulation of the test herbicides in the rhizome apices and nodes.     

Influence of weather on the efficacy of dichlorprop-P/MCPA and trihenuron-methyl

The influence of weather on the efficacy of dichlorprop-P/MCPA and tribenuron-methyl on annual weeds in spritig barley was studied in the field during 4 years at six locations in southern Sweden. The herbicides were applied at one-eighth to three-quarters of the full dose at three application times with approximately 6-day intervals. Weather stations, placed in the experiments, recorded climatic data, Maximum herbicide efficacy was obtained when spraying 1 week after the cotyledon stage with half or three-quarters of the recommended dose. Dose-response curves were estimated and the ED₈₀ doses were calculated. On average, the herbicide dose required to obtain an effect of 80% was about 40% of the recommended dose. The influence of weather was analysed for seven different periods: 7 and 2 days before and after herbicide application, 1 day before and after application, and the day of herbicide treatment. The most pronounced eftects of weather were found for the day of and the day before herbicide application, revealing the strong influence of weather on herbicide uptake and plant metabolism. High air tetnperature and low global radiation during the day of treattnent reduced the ED₈₀ dose of dichlorprop-P/MCPA, whereas the ED₈₀ dose of tribenuron-methyl increased. For both herbicides, precipitation and high soil temperature increased the ED₈₀ dose, which reflects the importance of rain on herbicide uptake and the effect of soil temperature on plant growth. The R² values were higher in the analyses of dichlorprop-P/MCPA than of tribenuron-methyl, indicating that the effect of dichlorprop-P/MCA was more weather-dependent than that of tribenuron-methyl. Separate analyses of the ED₈₀ doses for Brassica napus L., Chenopodium, album L. and Stellaria media (L.) Vill. generally resulted in increased R² values. but otherwise gave results similar to those for the total weed population. Although the analyses revealed significant effects of indivtdual weather factors on herbicide efficacy, it was not possible to discern a consistent and causal relationship between weather and herbicide performance.     

DIE WIRKUNG DER HERBIZIDE 2,4-D, AMITROL, ATRAZIN, CHLORPROPHAM UND CHLORFLURENOL AUF DIE NUCLEINSÄURE-BIOSYNTHESE DES ASCOMYCETEN NEUROSPORA CRASSA

Zusammenfassung. Es wurde die DNS- und RNS-Biosynthese von Neurospora crassa Wildstamm 3a6A unter Einfluss unterschiedlicher Konzentrationen von 2,4-D, Amitrol, Atrazin, Chlorpropham und Chlorflurenol untersucht. Die Variation der Herbizide erfolgte von 10^?3 bis 10^?6 M. Der in beliifteten Kulturen gezüchtete Pilz ist gegenuber Chlorpropham am empfindlichsten. Bei 10^?3 M ist die Toxizitätsgrenze überschritten und das Wachstum vollständig gehemmt. 2,4-D hat in einer Konzentration von 10^?3 M den grössten Einfluss auf die Nucleinsäure-Biosynthese. Die DNS-Werte erhöhen sich gegenüber der Kontrolle aiif 140%. Unter Einfluss von Atrazin (10^?3 M) scheint besonders die Protein-Synthese stimuliert zu werden. Die Zunahme beträgt hier fast 140%. Allgemein haben die untersuchten 5 Herbizide einen relativ geringen Einfluss auf die Nucleinsäure-Biosynthese. Ein grösserer Effect ist nur bei der höchsten Herbizid-Konzentration von 10^?3 M ZU erkennen. Der Pilz ist gegenüber diesen Herbiziden wenig empfindlich. Effets des herbicides 2,4-D, aminotriazole, atrazine, chlorprophame et chlorflurénol sur la biosynthése de l'acide nucléique chez un ascomycéte; Neurospora crassa Résumé. La biosynthése de l'ADN et de l'ARN fut déterminée chez la race sauvage 3a6A de Neurospara crassa, cultivé sur des milieux contenant du 2, 4-D, de l'aminotriazole, de l'atrazine, du chlorprophame et du chlorflurenol à des concentrations de 10^?3 a 10^?6 M. En culture aéréc, JV. crassa fut plus sensible au chlorprophame et à 10^?3 M. sa croissance fut complétement inhibée. L'effet le ptus marqué sur la biosynthésc de I'acide nucléique fut observé avec lc 2,4-D à 10^?3 M. concentration qui porta la teneur en ADN à 140% de celle du téemoin. Avec l'atrazine à 10^?3 M. la synthése des proteines en particulier sembla stimulée jusqu’à atteindre environ 140% du témoin. En général, les cinq herbicides etudids n'eurent qu'un effet relativement faibie sur la biosynthése de l'acide nucléique; seule la concentration la plus forte, 10^?3 M. cut un effet appreciable. N. crassa ne se montra pas tres sensible à ces herbicides. Effects of the herbicides 2,4-D, aminotriazole, atrazine, chlorpropham and chlorflurenol on nucleic-acid biosynthesis in the ascomycete Neurospora crassa Summary. Biosynthesis of DNA and RNA was determined in Neurospora crassa wild race 3a6A grown in cultures containing 2,4-D, aminotriazole, atrazine, chlorpropham and chlorflurenol in concentrations of 10^?3-10^?6 M. In aerated culture, N. crassa was most sensitive to chlorpropham and at 10^?3 M growth was completely inhibited. The greatest effect on nucleic-acid biosynthesis was given by 2,4-D at 10^?3 M which increased the DNA value to 140% of the control. With atrazine at 10^?3 M. protein synthesis in particular appeared to be stimulated, to almost 140% of the control. In general, the five herbicides studied had a relatively slight effect on nucleic-acid biosynthesis; only with the highest concentration of 10^?3 M was the effect appreciable. N. crassa was not very susceptible to these herbicides.     

STUDIEN ZUR VERTEILUNG VON 14C-MARKIERTEM 2,4-D IN VERSCHIEDEN EMPFINDLICHEN UNKRÄUTERN

Studies of the absorption and translocation of ¹⁴C-2,4-D in Chenopodium album L., Galinsoga parviflora Cav., Datura stramonium L. and Galium aparine L. in relation to their susceptibility gave the following results: In G aparine (resistant) there was little transport of 2,4-D applied to the leaves, and a probable relationship between resistance and the immediate binding of the 2,4-D in the treated leaf. D. stramonium (relatively resistant) transported 2,4-D in considerable amounts alter uptake through the leaf, while C. album (very susceptible) and G. parviflora (susceptible) were intermediate in respect of 2,4-D translocation. No relationship between susceptibility of these four species and 2,4-D uptake and translocation from the leaves could be established. After application to the root systems of the four species, 2,4-D was taken up and translocated in the shoot to varying extents. In G. aparine much 2,4-D was taken up and translocated. In contrast to leaf application, the herbicide was not immediately converted into a strongly-held immobile form. In C. album, G. parviflora and D. stramonium, however, no 2,4-D was translocated in the shoot. There was thus no correlation between susceptibility and shoot transport of 2,4-D in the four species studied. Distribution du 2,4-D marqué au ¹⁴C dans des espèces de mauvaises herbes présentant des sensibilités diverses     

Quantifying the detrimental effect of airborne dust on herbicide efficacy

One side effect of human activity and global climatic change is more airborne dust. This not only has undesirable effects on human health and the environment, but may also adversely affect many agricultural processes, including herbicide efficacy. This is particularly relevant in parts of the world where dust storms are common and limited rainfall means dust persists on plants for protracted periods. Accordingly, a series of greenhouse dose–response pot experiments was carried out to quantify the effect of a dust concentration of 1,500 µg/m³ on the performance of paraquat, glyphosate, sulfosulfuron and 2,4-D+MCPA. Dust-treated and untreated seedlings of Hordeum spontaneum and Sinapis arvensis were sprayed with sulfosulfuron and 2,4-D+MCPA, respectively, while paraquat and glyphosate were applied to both weed species. The efficacy of glyphosate and paraquat decreased significantly in the presence of dust on both species. Similar results were observed for 2,4-D+MCPA on S. arvensis. In contrast, the efficacy of sulfosulfuron on H. spontaneum was not affected by dust. In the presence of dust, the doses of glyphosate, paraquat and 2,4-D+MCPA required for a 90% effect were enhanced by a factor of 1.9 to 2.6. The negative impact on glyphosate efficacy was more pronounced in S. arvensis than H. spontaneum, while it was similar for paraquat. Future studies should consider the amount, duration and composition of dust as well as its impact on other weeds and herbicides. Potential approaches to overcome the detrimental influence of dust on the performance of herbicides were also suggested for future studies.     

Genetic variation in herbicide resistance in scentless mayweed (Tripleurospermum inodorum (L.) Schultz Bip.) II. Intraspeciffc variation in response to ioxynil and MCPA, and the role of spray retention characteristics

Forty-eight populations of Tripleurospermum inodorum (L.), Schultz Bip. (scentless mayweed) were collected from southern Britain and northern France between 1970 and 1972 and screened simultaneously for resistance to the herbicides ioxynil and MCPA. The mean fresh weights per plant in different population samples sprayed with ioxynil at 28 mg/m² a.i. ranged from 2·2 to 39·5% of those of the corresponding controls, with a mean for all populations of 20·0 ± 1·09%, and the mean fresh weights per plant in different population samples sprayed with MCPA at 175 mg/m² a.e. ranged from 10·3 to 60·1% of those of the corresponding controls, with a mean for all populations of 43·0 ± 1·60%. Resistance to ioxynil differed significantly between populations from different geographic areas but showed no correlation with spraying history. Resistance to MCPA also differed significantly between populations from different geographic areas, and showed a strong positive correlation with ioxynil resistance, but MCPA resistance was significantly greater in populations with a history of heavy spraying than in other populations. Spray retention and other physical characteristics were measured in six populations, but showed no correlation with herbicide resistance. It is suggested that most of the differences in herbicide resistance between populations of T. inodorum are side effects of genotypic differentiation in physiological characters not directly related to herbicide resistance, but that there has been some direct selection for resistance to MCPA.     

An investigation of herbicide interaction with the H+-ATPase activity of plant plasma membranes

This study has investigated the activity of several herbicide classes at the plant plasma membrane. Two-phase partitioning was used to prepare highly purified plasma membrane vesicles from the monocotyledon weed black-grass (Alopecurus myosuroides Huds.) and the dicotyledon crop sugar beet (Beta vulgaris L. cv. Celt). The purity of the plasma membrane H⁺-ATPase activity was characterised with respect to inhibitors, pH and substrate specificity. In both species, contamination of the plasma membrane by tonoplast fragments was largely eliminated and chlorophyll was absent. In addition, the plasma membrane H⁺-ATPase from black-grass and sugar beet exhibited high vanadate sensitivity and a sharp pH profile around 6·5. Subsequently, H⁺-ATPase activity was assayed in the presence (100 μM ) and absence of four graminicide classes and auxin-type herbicides. Graminicides, including the aryloxyphenoxypropionate diclofop-methyl and the thiocarbamate triallate, inhibited H⁺-ATPase activity by 50–80% in both species. However, other graminicides, including the cyclohexanediones and the chloroacetamide alachlor, had no affect. Similarly, auxin-type herbicides such as 2,4-D and MCPA did not inhibit H⁺-ATPase activity. Results are discussed in relation to the proposed mode of action of these herbicides. © 1998 SCI     

Uptake, translocation and fate of 2,4-D and chlorsulfuron in Silene vulgaris (Moench) Garcke

Experiments were conducted to examine the up take, translocation and metabolism by S. vulgaris of two distinctly different herbicides: 2,4-D, a phenoxyalkanoic acid with growth regulator activity to which this species exhibits complete tolerance, and chlorsulfuron, a sul-fonylurea to which S. vulgaris is highly sensitive. Despite their structural dissimilarities 2,4-D and chlorsulfuron was readily absorbed by S. vulgaris with 65 and 69%, respectively, of the applied dosage being absorbed within 72 hours after treatment. Approximately 35% of the 2,4-D and 10% of the chlorsulfuron label was translocated out of the treated leaf after 72 hours. Neither herbicide accumulated in the terminal bud. Seventy-two hours after treatment 63% of the recovered ¹⁴C remained as unaltered 2,4-D in S. vulgaris, while in tomato, a 2,4-D sensitive species, 65% of the recovered ¹⁴C remained as intact herbicide. In S. vulgaris approximately 86% of the radioactivity remained as intact chlorsulfuron 72 hours after treatment compared to 12% in the tolerant wheat. The tolerance of S. vulgaris to 2,4-D could not be accounted for by limited absorption, translocation nor metabolic degradation of the herbicide. The sensitivity of S. vulgaris to chlorsulfuron would appear to be related to the inability of this species to metabolize the herbicide molecule.     

Chemical control of nodding thistle (Carduus nutans L.) in New Zealand pastures

Broadcast sprays of several herbicides were applied at different times of the year at several sites in Hawkes Bay, Canterbury and Otago. For good thistle control, date of application was more important than types of herbicide. In Hawkes Bay, applications made in April, May and June tended to be the most effective. Under slightly cooler Canterbury conditions, April, September and October were the best application dates. In the Otago trials, spring emergence of thistle seedlings meant that the most consistent results came from September or October applications. At all sites, applications made in July or August were relatively ineffective, probably because of low winter temperatures and slow thistle growth rates. MCPA (potassium salt) at 1·0 kg ha^?1 was the standard herbicide used in all experiments. MCPA at 0·5 kg ha^?1, MCPB (sodium salt) at 0·5 and 1·0 kg ha^?1 and 2,4-D at 0·5 kg ha^?1 did not kill as many thistles as MCPA at 1·0 kg ha^?1. MCPA at 1·5 kg ha^?1 and MCPB (butyl) ester + clopyralid at 0·5 + 0·015 or 1·0+0·03 kg ha^?1 gave consistently better control than MCPA at 1·0 kg ha^?1 2,4-D at 1·0 or 1·5 kg ha^?1, MCPB at 1·5 or 2·0 kg ha^?1, and MCPA + MCPB at 0·33 + 1·0 or 0·67 + 0·5 kg ha^?1 gave results very similar to MCPA at 1 kg ha^?1. Thistle control varied between sites and years. Some of the variation may have been due to different proportions of first and second year thistles present at spraying, and to variation in genetically determined herbicide susceptibility. Chemical control of thistles was short term only, because of dormant seeds in the soil.     

Studies on the mode of action of asulam,aminotriazole and glyphosate in Equisetum arvense L. (field horsetail). II: The metabolism of [14C]asulam, [14C]aminotriazole and [14C]glyphosate

The metabolism of [¹⁴C]asulam (methyl 4-aminophenylsulphonylcarbamate), [¹⁴C] aminotriazole (1H-1,2,4-triazol-3-ylamine) and [¹⁴C]glyphosate (N-(phosphonomethyl)glycine) were assessed in Equisetum arvense L. (field horsetail). Following application of the test herbicides (4mg?0.3 °Ci herbicide/shoot) to the shoots of 2-year-old pot-grown plants, the total recovery of ¹⁴C-label after 1 week and 8 weeks was high for all three herbicides (>80-0% of applied radioactivity). Asulam was persistent (>69-7% of recovered radioactivity) in both shoots and rhizomes. Sulphanilamide, a hydrolysis product of asulam, accounted for the remainder of the recovered radioactivity. Aminotriazole showed evidence of conjugation in shoots and rhizomes. The principal ¹⁴C-labelled component in shoots was composed of high proportions of aminotriazole (>76-3%) together with the metabolites: X (ninhydrin positive), β-(3-amino-1,2,4-triazolyl-1-)α-alanine, Y (diazotization positive) and various unidentified compounds. Rhizomes generally contained lower proportions of intact aminotriazole (>59.4%) together with the metabolites X,Y and unidentified compounds. The proportion of aminotriazole did not decrease with time in shoots or rhizomes; however, the ratio of metabolite X: Y moved in favour of Y as the interval after treatment increased. Glyphosate was extensively metabolised in shoots and rhizomes to yield aminomethylphosphonic acid (AMPA) and various unidentified compounds. Differential metabolism appears to be one of the factors which may govern the persistence and toxicity of the test herbicides in E. arvense.     

Biological Control of Lantana

Abstract

Experiments conducted at the International Rice Research Institute (IRRI) in the Philippines, showed that all commonly marketed formulations and derivatives of 2,4-D and MCPA were equally effective in controlling barnyard grass [Echinochloa crusgalli (L.) Beauv.] and other annual weeds in transplanted rice (Oryza sativa L). In the Philippines, these phenoxy acid herbicides cost US$2.50/ha as liquid formulations and US$5.50/ha as granular formulations. These low-cost herbicides provide excellent alternatives to hand weeding in transplanted tropical rice. Other herbicides which can control weeds before or after the weeds emerge are more expensive than 2,4-D or MCPA. Some of these selective herbicides, such as butachlor and TCE-styrene + 2,4-D, are in the Philippine market. Their prices vary from US$8 to US$12/ha.

For direct-seeded flooded rice, granular formulations of several new herbicides, such as butachlor, benthio-carb and C-288 (chemistry not yet disclosed), were highly selective in controlling barnyardgrass and other annual weeds under tropical conditions. C-288 controls algae in addition to annual weeds in direct-seeded flooded rice. Of these three promising herbicides, only butachlor is marketed in the Philippines at US$8/ha. For upland rice, the chemicals which look promising are butachlor, benthiocarb and fluorodifen. Butachlor liquid is available to rice farmers in Asia at about US$16/ha. These herbicides provide an excellent alternative to hand weeding. Generally a complete job of weed control in upland rice requires more than one hand weeding.     

Spreading and penetration of herbicides dissolved in oil carriers*

Four non-phytotoxic paraffinic oils of increasing viscosities and boiling ranges were compared as carriers for 2,4-D, dinoseb and terbacil under glasshouse conditions. Terbacil and dinoseb activity was increased approximately ten-fold in the oil carriers (150 1/ha) v. water on ivyleaf morning glory (Ipomoea hederacea (L.) Jacq.), cucumber (Cucumis sativus L.) and sorghum (Sorghum bicolor (L.) Moench). 2,4-D activity on bean (Phaseolus vulgaris L.) and sorghum was not increased by the oil carriers. The four oils showed similar effectiveness as herbicide carriers except that a trend existed towards increased herbicide activity in the medium to high viscosity, low volatile oils. ¹⁴C-chlorpropham was applied in a non-phytotoxic oil carrier to the leaves of morning glory, cucumber and sorghum. It moved externally on the upper but not on the lower leaf surface to the shoot apex of all plants, but internal herbicide transport was not evident. Similarly, greater surface movement and penetration of ¹⁴C-2,4-D occurred in sorghum, when applied in the same oil carrier v. water with surfactant, but herbicide translocation was not affected. The penetration and translocation pattern of ¹⁴C-2,4-D applied in four non-phytotoxic oil carriers of increasing viscosities were studied in bean (Phaseolus vulgaris L.). All oil carriers, as compared to 2,4-D in water-surfactant greatly enhanced herbicide penetration through both upper and lower primary leaf surfaces and subsequent translocation. The extent of oil carrier movement on the leaf surface did not determine the distance of subsequent herbicide translocation which was the same for all four oil carriers, but did influence amount of the herbicide translocated. Approximately the same quantity of ¹⁴C was absorbed through both upper and lower leaf surfaces for both ¹⁴C-chlorpropham and ¹⁴C-2,4-D in oil carriers, indicating that stomatal penetration is not a factor in determining rate of oil entry into leaves. This work indicates the importance of measuring oil carrier mobility on the leaf surface, when studying the effects of such carriers on herbicide penetration and translocation. Etalement et penetration d'herbicides dissous dans des supports huileux. Quatre huiles paraffiniques non toxiques ayant des viscosityés et des zones d'ébullition croissantes ont été comparées, en serre, comme supports pour le 2,4-D, le dinosébe et le terbacile. L'activité du terbacile et du dinosébe a été approxi-mativement multipliée par dix dans les supports huileux (150 1/ha) par rapport au support hydrique, sur le liseron (Ipomoea hederacea (L.) Jacq.), le concombre (Cucumis sativus L.) et le sorgho (Sorghum bicolor (L.) Moench). L'activité du 2,4-D sur le haricot (Phaseolus vulgaris L.) et le sorgho n'a pas été accrue par les supports huileux. Les quatre huiles ont manifeste une efficacité analogue en tant que supports pour les herbicides; toutefois, l'activitd herbicide tend à s'accroître entre les viscosityés moyennes et fortes, pour des huiles à basse volatilityé. Le chlorprophame-¹⁴C a été appliqué dans un support huileux non phytotoxique sur les feuilles de liseron, de concombre et de sorgho. II migre extérieurement sur la face foliaire supérieure mais pas sur la face inférieure vers l'apex des tiges de toutes ces plantes; cependant la migration en surface et une pénétration plus importantes du 2,4-D-¹⁴C se sont manifestoes dans le sorgho lorsque I'herbicide a été appliqué dans le meme support huileux, en comparaison avec le support eau plus agent tensio-actif, mais la migration interne de I'herbicide n'a pas été affectée. Le mode de pénétration et de migration du 2,4-D-¹⁴C appliqué dans quatre supports huileux non phytotoxiques, de viscosités croissantes, a étéétudié chez le haricot (Phaselous vulgaris L.). Tous les supports huileux, par comparaison avec l'eau plus un agent tensio-actif, ont hjrtement augmenté la pénétration du 2,4-D à travers les faces supérieure et inférieure de la feuille, ainsi que sa migration ultérieure. L'étendue du déplacement du support huileux sur la surface foliaire n'a pas déterminé la distance de la migration ultérieure de I'herbicide, laquelle fut identique pour les quatre huiles, mais elle a influencé la quantité d'herbicide transportée. Une quantité approximativement identique de ¹⁴C a été absorbie á travers les faces supérieure et inférieure de la feuille pour le chlorprophame ¹⁴C et le 2,4-D-¹⁴C dans les supports huileux, ce qui montre que la pénétration par les stomates n'est pas un facteur déterminant de la dose de pénétration de I'huile dans les feuilles. Ce travail met en évidence l'importance de la mesure de la mobilité du support huileux sur la surface foliaire lorsqu'on étudie les elTets de tels supports sur la pénétration et la migration de I'herbicide. Verteilung und Penetration von in öl gekosten Herbiziden Vier nicht phytotoxische Paraffinöle unterschiedlicher Viskos-ität und von verschiedenem Siedebereich wurden als Träger für 2,4-D, Dinoseb und Terbacil unter Gewächshausbeding-ungen miteinander verglichen. Die Wirkung von Terbacil und Dinoseb mit den Ölen als Träger (150 1/ha) gegenüber Ipomoea hederacea (L.) Jacq., Cucumis sativus L. und Sorghum bicolor (L.) Moench. war, verglichen mit Wasser als Trager, um etwa zehnmal besser. Die Wirkung von 2,4-D auf Phaseolus vulgaris L. und Sorghum wurde durch die Ole nicht verbessert. Die vier Öle wirkten als TrSgersubstanz fur die Herbizide etwa gleich gut. Es bestand aber eine Beziehung derart, dass Öle mit mittlerer bis hoher Viskositat und geringer Fluchtigkeit eine verbesserte Herbizidaktivitat bewirkten. ¹⁴C-Chlorpropham wurde in einem nicht phytotoxischen Öl auf die Blätter von Ipomoea, Cucumis und Sorghum appliziert. Es breitete sich bei alien Pflanzen auf der Blatto-berseite, nicht jedoch auf der Biattunterseite, bis zum Sprossapex aus. Ein Transport des Herbizids in der Pflanze wurde nicht beobachtet. Ahnlich war es mit ¹⁴C-2,4-D bei Sorghum: verglichen mit Wasser plus Surfactant bewirkte das gleiche Öl eine grössere Flächenausbreitung und eine verbesserte Penetration; die Translokation des Herbizids wurde jedoch nicht beeinflusst. Die Penetration und Translokation von ¹⁴C-2,4-D, appliziert in vier nicht phytotoxischen Oien mit unterschiedlicher Viskosität, wurde an Phaseolus untersucht. Im Yerg-leich zu 2,4-D in Wasser plus Surfactant bewirkten alle Ole eine wesentlich verbesserte Penetration und Translokation des Herbizids. Die mit Öl bedeckte Blattoberflache hatte keinen Einfluss auf die Translokationsstrecke des Herbizids. Diese Distanz der Herbizidtranslokation war bei alien Ölen gleich gross. Die Menge an transloziertem 2,4-D war jedoch unterschiedlich gross. Von dem in den verschiedenen Ölen gelösten ¹⁴C-Chlor-propham und ¹⁴C-2,4-D wurde ungefahr die gleiche Menge an ¹⁴C sowohl durch die Blattober- wie auch durch die Biattunterseite absorbiert, was darauf hinweist, dass die Penetration des Öls in das Blatt nicht durch die Aufnahmer-ate über die Stomata bestimmt wird. Diese Arbeit weist auf die Bedeutung von Untersuchungen hin, die sich mit der Messung der Beweglichkeit von Öl-Trägerstoffen auf der Blattfläche beschäftigen, wenn die Wirkung solcher Träger auf die Penetration und Translokation von Herbiziden untersucht werden soll.     

Control of Solatium karsensis in grain sorghum

Solatium karsensis Symon, an Australian native perennial, has become an important weed in irrigated summer crops in far western New South Wales. A screening trial of 14 herbicides showed that atrazine was the most effective treatment, though 2,4-D also suppressed S. karsensis in grain sorghum (Sorghum bicolor L. cv. Rico) for the duration of the crop. Grain sorghum yields were higher in plots treated with atrazine at 2–5 kg (a.i.) ha^?1 than for any other herbicide treatment or the untreated control. Because the root system remained viable annual herbicide application would be necessary for the continued control of 5. karsensis.     

Use of corn root protoplasts in herbicide absorption studies

Intact and viable protoplasts were enzymatically isolated from corn (Zea mays L.) seedling roots and collected for herbicide absorption studies by differential centrifugation and flotation through a Ficoll density gradient. A method was developed for terminating herbicide absorption by rapid centrifugation of protoplasts out of solutions without washing the protoplasts. Within 10 sec, atrazine [2-chloro-4-ethylamino-6-isopropylamino-s-triazine] accumulated in protoplasts to a concentration 36% greater than the external concentration; no further absorption occurred through 30 min. However, 2,4-D [2,4-dichlorophenoxyacetic acid] accumulated to twice and 16 times the external concentration at pH 6.5 and 4.5, respectively. Calculations of theoretical 2,4-D concentrations in protoplasts also predicted greater accumulation at pH 4.5 than at pH 6.5. Both atrazine and 2,4-D absorption were consistent with previous measurements of absorption by plant tissues. Thus, corn root protoplasts are feasible experimental material for studying absorption of herbicides at the cellular level.     

Foliar absorption and translocation of nicosulfuron and rimsulfuron in five annual weed species

Ambrosia artemisüfolia L. (common ragweed) and Digitaria ischaemum Schreb. (smooth crabgrass) are not controlled by nicosulfuron and rimsulfuron at the highest recommended application rates, whereas Panicum miliaceum L. (wild proso millet), Amaranthus retroflexus L. (redroot pigweed) and Avena fatua L. (wild oat) are susceptible. The foliar absorption and translocation of ¹⁴C-nicosulfuron and ¹⁴C-rimsulf uron were studied in these weed species up to 48 h after treatment (HAT). Differences in herbicide uptake and translocation were not correlated with the species susceptibility. By 48 HAT, more than 50% of both herbicides remained on the treated leaf surface. Foliar absorption of rimsulfuron was greater than that of nicosulfuron in A. retroflexus, P. miliaceum and A. artemisüfolia. Most of the absorbed herbicide remained in the treated leaf of each weed species. Export of ¹⁴C–nicosulfuron ranged from 28 to 54% of that absorbed, in contrast to 15 to 39% for ¹⁴C–rimsulfuron. The absorption and translocation rates of both herbicides were highest within the initial 6 HAT, and decreased thereafter. Both herbicides showed approximately the same distribution pattern within each weed species.     

Response of winter wheat (Triticum aestivum L.) and weeds to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl

Field and greenhouse experiments were conducted in 2004 and 2005 to study weed control and the response of winter wheat to tank mixtures of 2,4-D plus MCPA with clodinafop propargyl. The field experiments were conducted at Yazd and Oroumieh, Iran, with factorial combinations of 2,4-D plus MCPA at 0, 975, and 1300 g ai ha⁻¹ and with clodinafop propargyl at 0, 64, 80, 96, and 112 g ai ha⁻¹ in four replications. The greenhouse experiments further evaluated the effect of these tank mixtures on weed control, where each herbicide mixture was considered as one treatment and the experiment was established in a randomized complete block design with four replications. In the field experiments, the herbicides were applied at wheat tillering, while in the greenhouse experiments they were applied at the beginning of the tillering stage and at the four-leaf stage of the grass and broadleaf weeds, respectively. The results indicated antagonistic effects between 2,4-D plus MCPA and clodinafop propargyl. The best tank mixture with regard to weed control efficacy was 2,4-D plus MCPA at 975 g ai ha⁻¹ with clodinafop propargyl at 96 g ai ha⁻¹. The wheat grain yield was also increased by the tank mixture of clodinafop propargyl with 2,4-D plus MCPA. Generally, to inhibit clodinafop propargyl efficacy reduction due to tank-mixing with 2,4-D plus MCPA, it is recommended that the application dose of 64 g ai ha⁻¹ should be increased to 96 g ai ha⁻¹.     

STUDIES ON HERBICIDE CONTENTS IN ROOTS OF SKELETON WEED (CHONDRILLA JUNCEA L.) FOLLOWING LEAF APPLICATIONS

Summary. The herbicides studied were 2,4-D, 2,4-DB, dicamba and orthoarsenic acid. Herbicide content in the roots was taken as an overall measure of penetration into and absorption by the leaves, and of translocation to the roots.
A significantly greater 2,4-D content resulted from foliar application at pH 3–5 than at higher values, though at pH 8–5 the inclusion of triethanolamine significantly increased the 2,4-D content. No evidence was obtained that a greater 2,4-D content should result from foliage applications of 2,4-DB than from 2,4-D. Dicamba gave a greater herbicide content than 2,4-D when applied at high concentration at 20° C but not at 25° C, probably because of less injury at the lower temperature.
Concentrations of Tween 20 up to 2% had no deleterious effect on the 2,4-D content; on the other hand 2,4-D content was lowered by 0–25% or more of cetyltrimethyl-ammonium bromide. Poor wetting is not the cause of the variable herbicide contents sometimes obtained.
Orthoarsenic acid, which has given better control of the weed than 2,4-D, was very poorly translocated; its effectiveness is due to its high intrinsic toxicity.
Etudes sur la teneur en herbicide des racines de Chondrilla juncea L. á la suite d'applications sur les feuilles     

Asulam mixtures for weed control in flax

Five field experiments were conducted from 1972 to 1975 to evaluate weed control in flax (Linum usitatissimum L.) using post-emergence treatments of asulam [methyl (4-aminobenzenesulphonyl) carbamatel alone and in combination with other herbicides. The ¹⁴C-asulam absorption by leaf segments and roots of glasshouse grown wild oats (Avena fatua L.) was also investigated. Asulam at 1.12 kg/ha gave good wild oat control and acceptable control of green foxtail (Setaria viridis (L.) Beauv.). However, wild oat control was poorer when asulam was combined with other herbicides: on a 3-year average, as compared with asulam alone at equal rates, the asulam+MCPA mixture resulted in a greater antagonism and a significant 6% reduction in flax seed yield, whereas the asulam+bromoxynil/MCPA mixture gave the least antagonistic effect, improved broadleaf weed control and increased yield by 13%. In mixtures, the potassium salt of MCPA was more compatible with asulam for weed control than the amine form. Both leaf segments and roots of wild oats absorbed and distributed less ¹⁴C-asulam from solutions containing MCPA than from those containing bromoxynil or bromoxynil/MCPA.