bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of fire on population dynamics of Mikania micrantha H.B.K. during early succession after slash‐and‐burn agriculture (jhum) in northeastern India
Authors: SWAMY P. S. , RAMAKRISHNAN P. S.
Published: July 2006

Summary: Résumé: Zusammenfassung

The population size of Mikania micrantha H.B.K. is considerably enhanced by fire in 2‐, 4‐ and 8‐year‐old fallows developing after slash‐and‐burn agriculture (jhum) in northeastern India. The recruitment pattern in burnt and unburnt sites in each fallow differed. Seedling recruitment was restricted only to burnt sites in 2‐ and 4‐year‐old fallows, whereas it occurred in both burnt and unburnt sites in an 8‐year‐old fallow. Sexual reproductive potential of the species was affected by the age of the fallow and by fire in each fallow plot. These results are related to micro‐environmental changes in the habitat as a consequence of fire in different fallow plots.

Effet du feu sur la dynamique des populations de Mikania micrantha H.B.K. dans un mode de conduite alternatif coupe‐brulage dans le nord‐est de l'Inde

L'importance des populations de Mikania micrantha a été considérablement augmentée par le feu dans des vieilles jachères de 2, 4 et 8 ans conduites selon la technique coupe‐brûlage dans le Nord‐Est de l'Inde. Le processus de reprise dans les zones brûlées et non brûlées a été différent pour chacune des jachères. La reprise de plantules n'a eu lieu que dans les zones brûlées pour les jachères vieilles de 2 et 4 ans. mais elle est survenue en tout lieu dans la jachère de 8 ans. Le potentiel de reproduction sexuée a été affectéà la fois par l'âge de la jachère et par le feu dans chaque parcelle. Ces résultats sont liés à des changements microenvironnementaux dans l'habitat, conséquence du feu dans les différentes parcelles en jachère.

Der Einfluss von Feuer auf die Populationsdynamik von Mikania micrantha H.B.K. während der Frühentwicklung einer Folgevegetation nach Brandhackbau in NO‐Indien

Die Populationsdichte von Mikania micrantha H.B.K. wird nach Rodung und Abbrennen auf 2, 4 und 8 Jahre altem Brachland durch Feuer beträchtlich erhöht. Auf den einzelnen Brachflächen war die Wiederbesiedelung von abgebrannten und nicht abgebrannten Parzellen verschieden. Die Entwicklung einer Sämlingspopulation war auf 2 resp. 4 Jahre altem Brachland auf abgebrannte Flächen beschränkt, während auf 8 Jahre alter Brache sowohl auf abgebrannten als auch nicht abgebrannten Flächen die Entwicklung einer Sämlingspopulation stattfand. Die sexuelle Reproduktionskraft der Species wird durch die Dauer der Brache und die Wirkung des Feuers beeinflusst. Diese Ergebnisse stehen in Beziehungzu kleinflächigen Umweltveränderungen im Biotop, als Folge des Feuers und des Alters der Brache.
Metabolism of chlortoluron in tolerant species: possible role of cytochrome P‐450 mono‐oxygenases
Authors: GONNEAU M. , PASQUETTE B. , CABANNE F. , SCALLA R.
Published: July 2006

Pathways of chlortoluron metabolism were compared in excised leaves of four tolerant species, namely wheat (Triticum aestivum var Clement), Bromus sterilis, Galium aparine and Veronica persica. The herbicide was principally detoxified by hydroxylation of the ring methyl in wheat and by N‐dealkylation in Veronica persica. Both pathways were involved in Bromus sterilis and Galium aparine. Kinetic study of the degradation showed that capacity to form non‐toxic conjugates could, at least partially, explain the tolerance of these species to chlortoluron. In plants treated with 1‐aminobenzotriazole, a cytochrome P‐450 enzyme inactivator, N‐dealkylation of chlortoluron was little or not affected, but ring methyl hydroxylation was strongly inhibited. This suggests that at least two distinct enzymatic systems could participate in this metabolism. Moreover, cytochrome P‐450 enzymes could be involved in the ring methyl hydroxylating reaction.
Studies on competition between wheat and Chenopodium album L.
Authors: BHASKAR* A. , VYAS K. G.
Published: July 2006

Interspecific competition between wheat (Triticum aestivum L.) and Chenopodium album L., was studied in pots using the replacement series design of de Wit. Competitive interference for phosphorus, and to some extent for nitrogen, between the two species was noted. This played a major part in limitation of growth of wheat plants by C. album, whereas wheat exhibited greater non‐competitive interference in restricting potassium uptake by the weed. Increasing interference from the weed resulted in significant reductions in wheat grain size and yield.
Study of seasonal variation in dormancy of Spergula arvensis L. seeds in a condensed annual temperature cycle
Authors: KARSSEN C. M. , DERKX M. P. M. , POST† B. J.
Published: July 2006

Changes in dormancy of Spergula arvensis seeds were studied during pre‐incubation at constant temperatures and under a temperature regime that condensed the annual temperature cycle into 73 days. Each day in the regime represented the mean day and night temperatures and day lengths of 5 successive days of an average year in The Netherlands. Incubation occurred in water or loamy sand, in darkness. Germination of the seeds was tested in water or KNO3 over a range of temperature. Seeds were irradiated with saturating doses of red light. In half of the treatments, pre‐incubated seeds were dehydrated at the transfer to the conditions of the germination test. Breaking of dormancy occurred under conditions of 'spring'. It did not depend on exposure to low‘winter’temperatures, but was induced by rising 'spring’temperatures. Seeds developed secondary dormancy in late‘autumn'. The expression of the changes in dormancy that were induced during pre‐incubation depended on the conditions of the germination test. Light, nitrate and dehydration stimulated germination. The experiments predicted that field emergence from nitrate‐poor soils that have not been dehydrated will be restricted to a short period in autumn, whereas disturbance of nitrate‐rich soils followed by a dry spell will stimulate germination of S. arvensis seeds from early spring to late autumn. The data presented good explanations for the cosmopolitan character and the serious weediness of this species. Its classification as a summer or winter annual is discussed.
Floristic composition and agricultural importance of weeds in southern Spain
Authors: SALVÁ A. PUJADAS , HERNÁNDEZ BERMEJO J. E.
Published: July 2006

Summary: Résumé: Zusammenfassung

A survey was made of the agrestal and ruderal flora of southern Spain, mainly in the province of Córdoba, and a total of 941 weed species in 81 families were found in ecosystems showing severe human disturbance. The families with the highest numbers of species were Compositae, Leguminosae and Gramineae; other families like Amaran‐thaceae, Solanaceae and Oxalidaceae were also important because of their special behaviour as weeds. An assessment of the agricultural importance of the species in terms of the damage caused to crops showed that 36,3% could be considered rare or casual, 15,6% slightly harmful, 14,1% locally harmful. 7,3% harmful, and 26,6% very harmful. The richness of the flora in the different ecosystems is analysed and compared with that in other countries.

Composition floristique et importance agronomique des adventices dans le Sud de l'Espagne

Une enquête a été conduite sur la flore agreste et ruderale dans le Sud de l'Espagne, principalement dans la province de Cordoue, et un total de 941 espèces d'adventices de 81 familles ont été trouvées dans des écosystèmes fortement influencés par l'intervention des hommes. Les familles les plus riches en espèces étaient les composées les légumineuses et les graminées: d'autres familles, comme les amaranthacées, les solanacées el les oxalidacées avaient également de l'importance en relation avec leur comportement particulier en tant qu'adventices. Une estimation de l'importance agricole des espèces en terme de nuisances provoquées aux cultures, montre que 36,3% peuvent être considérées comme rares ou occasionnelles, 15,6% comme faiblement dangereuses, 14,1% comme localement dangereuses, 7,3% comme dangereuses et 26,6% comme extrêmement dangereuses. La richesse de la flore dans différents écosystèmes est analysée et comparée à ce qui se passe dans d'autres pays.

Floristische Zusammenseizung und landwirtschaftliche Bedeutung von Unkräutern in Südspanien

Die Segetal‐ und Ruderalvegetation in Südspanien, vor allem in der Provins Cordoba, wurde aufgenommen, wobei insgesamt 941 Unkrautarten aus 81 Familien in den am meisten vom Menschen beeinflussten Ökosystemen gefunden wurden. Die artenreichsten Familien waren die Compositen, Leguminosen und Gramineen; wichtig waren auch die Amaranthaceen, Solanaceen und Oxalidaceen, weil zu ihnen besonders ausgeprägte Unkrautarten gehören. Im Hinblick auf die landwirtschaftliche Bedeutung, d.h. die Schadwirkung, welche die Arten in Kulturpflanzenbeständen haben, konnlen 36,3% als selten oder gelegentlich und 15,6% als wenig schädlich eingestuft werden, 14,1% als lokal schädlich, 7,3% als schädlich und 26,6% als sehr schädlich. Der Florenreichtum in den verschiedenen Ökosystemen wurde analysiert und mit dem anderer Länder verglichen.
Photosensibilite des bromes annuels (Bromus L. spp.)
Authors: JAUZEIN P.
Published: July 2006

Une sensibilisation des agriculteurs au problème des bromes envahissant des céréales nous a incitéà rechercher si les caractéristiques germinatives de ces espèces pouvaient expliquer leur comportement au champ. Cet article étudie plus particulièrement la réponse des bromes à la lunnère. Douze espèces annuelles ont été testées: 6 pour le sous‐genre Bromus, 6 pour le sous‐genre Anisantha Koch; Bromus catharticus Vahl a été rajouté car il peut se comporter comme annuel. La photosensibilité est très marquée surtout à basse température où elle est négative. Les différentes espèces ont été comparées entre elles en tenant compte de leur origine géographique. La photosensibilité négative est beaucoup plus importante pour le sous‐genre Anisantha Koch et pour les lots d'origine méditerranéenne. L'intensité et la persistance de ce phénoméne lui permettent certainement de jouer un rôle non négligeable dans le comportement de ces graminées en milieu naturel.
Untersuchungen zum Einfluss einer Pflanzenschutzmittelspritzfolge auf das Rückstandsverhalten von Terbutryn und die mikrobielle Aktivität im Boden. Teil II. Beeinflussung der mikrobiellen Aktivität
Authors: AUSPURG B. , PESTEMER W. , HEITEFUSS R.
Published: July 2006

Laborversuehe zum Einfluß von Terbulryn unter verschicdenen Inkubationsbedingungen (10 und 20°C; 30 und 60% WKmax) auf die mikrobielle Aktivität des Bodens (Dehydrogenaseaktivität, Atmung nach Glukosezugabe, N‐Umsatz) lifeßen selbst bei der zehnfachen Aufwandmenge kaum Beeinträchtigungen der Mikroflora in zwei unter‐sehiedlich sorptiven Böden erkennen. Demgegenüber verursachte Dinoscbacetat—allein und in Kombination mit Terbutryn und weiteren Pflanzenschutzmitteln (Triadimefon, Parathion)—bereits bei der einfachen Aufwandmenge bei allen Inkubationsbedingungen deutliche Hemmungen der Dehydrogenaseaktivität und der Bodenatmung. Nach Anwendung der zehnfachen Aufwandmenge setzte im sorptionsschwachen Boden nach einer anfänglichen Nitrifikationshemmung eine verstärkte Mineralisation bodenbürtigen Stickstoffs ein. Triadimefon und Parathion riefen sowohl Hemmungen als auch Stimulationen der mikrobiellen Aktivität hervor, die sich auch in den Kombinationen mil den übrigen Pflanzenschutzmitteln bemerkbar machten, deren Ursachen aber nicht eindeutig zu klären waren. Im Freiland konnten die Beeinflussungen der Bodenatmung und der Dehydrogenaseaktivität in ihrer Tendenz bestätigt werden, wobei eine deutliche Wiedererholung zu erkennen war. Die Dehydrogenaseaktivität reagierte insgesamt am empfindlichsten und ist daher zur Erfassung der Nebenwirkungen von Pflanzenschutzmitteln auf Bodenmikroorganismen gut geeignet. Eine zusätzliche Untersuchung des N‐Umsatzes kann weitere Hinweise für die Interpretation der Ergebnisse geben.
Growth pattern of diploid and tetraploid spotted knapweed, Centaurea maculosa Lam. (Compositae), and effects of the root‐mining moth Agapeta zoegana (L.) (Lep.: Cochylidae)
Authors: MÜLLER H.
Published: July 2006

Glass‐faced growth containers were used to study the phenology of three demes of Centaurea maculosa Lam. (Compositae), and the impact of root‐mining by the moth Agapeta zoegana (L.) (Lep.: Cochylidae) on rooting intensity. This moth was recently established in North America for the biological control of spotted and diffuse knapweed, C. maculosa and C. diffusa. The life cycle, biomass production and longevity of the diploid European host plant (monocarpic biennial) and the tetraploid North American target species (polycarpic perennial) differed considerably, providing a possible explanation for the rapid spread of the tetraploid species in North America. Compared to controls, plants of German and Canadian origin infested by A. zoegana showed increased root growth during the mining period and after the emergence of the moths. However, no such difference was found in diploid plants of Hungarian origin. The observed plant reactions partly support, therefore, the hypothesis of a nutritionally controlled response to herbivory. Infested plants did not differ in fecundity compared to controls, but root‐mining tends to reduce the survival rate of immature plants The consequences for the plant population density are discussed.
Estimation of thresholds for weed control in Australian cereals
Authors: STREIBIG J. C. , COMBELLACK J. H. , PRITCHARD G. H. , RICHARDSON R. G.
Published: July 2006

A non‐linear model relating crop yield to the density of weeds was fitted to nine Victorian weeds to evaluate their competitive abilities. The weeds were: Acroptilon repens (L.) DC. (creeping knapweed), Chondrilla juncea L. (Skeleton weed, Raphanus raphanistrum L. (Wild radish), lolium rigidum Gaud. (Annual ryegrass), Lithospermum arvense L. (White iron weed), Brassica tournefortii Gouan (Wild turnip), Lamium amplexicaule L. (Deadnettle), Fumaria parviflora Lam. (White fumitory) and Amsinckia hispida (Ruiz & Pav.) I.M. Johnston (Amsinckia). Where more than one experiment was available for a weed, the net return for a herbicide treatment over a range of weed densities was calculated to obtain the economic threshold density.

Generally, the economic threshold densities within a weed species were the same order of magnitude, except for the perennial Chondrilla Juncea L., For this species data were collected in years of contrasting rainfall. The model used here is discussed in view of the threshold approach currently used in continental Europe.
Effect of sucrose taken up by developing Avena fatua L. panicles on the dormancy and α‐amylase synthesis of the seeds produced
Authors: CAIRNS A. L. P. , de VILLIERS O. T.
Published: July 2006

Dormancy of seeds harvested from excised Avena fatua panicles grown in solutions containing sucrose increased with increasing concentrations of sucrose. Induction of this sucrose‐imposed dormancy could be partially inhibited by the inclusion of GA4/7 in the growing medium. The sucrose‐grown seeds were fully viable and dormancy could be broken by methods commonly used to break dormancy, such as treatment with GA3 or dehusking and pricking the caryopsis. Low concentrations of sucrose added to the incubation medium stimulated GA3‐induced α‐amylase synthesis in mature de‐embryonated A. fatua caryopses but higher concentrations inhibited it. The relevance of these findings to the explanation of the environmental component of A. fatua seed dormancy is discussed.
Physiological responses of maize and sorghum to four different safeners for metazachlor
Authors: EKLER Z. , STEPHENSON G. R.
Published: July 2006

The ability of the herbicide safeners, BAS‐145138 (1‐dichloroacetyl‐hexahydro‐3,3,8a‐trimethyl‐pyrrolo(1,2a)pyrimidin‐6(2H)‐one), dichlormid (N,N‐diallyl‐2,2‐dichloroacetamide), flurazole (phenylmethyl ester), and MG‐191 (2‐dichloromelhyl‐2‐methyl‐1,3‐dioxolane) for preventing metazachlor injury to maize (Zea mays L.) and sorghum (Sorghum bicolor L.) seedlings were compared with their effects on 14C‐metazachlor metabolism to a glutathione (GSH) conjugate, effects on non‐protein thiol contents (mainly GSH) and effects on Glutathione S‐transferase (GST) activity in these two species.

Sorghum shoot growth was reduced by 41% and maize shoot growth was reduced by 54%, by metazachlor concentrations in vermiculite nutrient culture of 0·6 μM and 7·5μM, respectively. In this system, all four compounds had significant activity as safeners for metazachlor in both sorghum and maize seedlings. BAS‐145138 and flurazole were the most effective safeners in maize and sorghum, respectively. In the absence of safeners, the rate of non‐enzymatic conjugation of metazachlor and GSH was much greater than the enzymatic rate. However, the rate of enzymatic conjugation of metazachlor with GSH was increased by safener treatment in both maize and sorghum. Safener effectiveness was highly correlated with increases in 14C‐metazachlor uptake and metabolism in both species. Safener effectiveness was more highly correlated with safener effects on GST activity in maize or sorghum when 14C‐metazachlor was used as the substrate than when the non‐specific CDNB (1‐chloro‐2,4‐dinitrobenzene) was used as the substrate. Safener effectiveness was also strongly correlated with safener effects on GSH levels in sorghum, but not in maize, possibly because of the greater importance of non‐enzymatic conjugation of metazachlor with GSH in sorghum as compared to maize.
Response of maize (Zea mays L.) inbred lines and hybrids to chlorsulfuron
Authors: LANDI P. , VICARI A. , CATIZONE P.
Published: July 2006

Twenty inbred maize lines, raised in a growth chamber, were treated with 0 or 1 ng g−1 of chlorsulfuron which caused a variable reduction in root‐length. In a second experiment, all crosses (reciprocals included) among two tolerant lines (T: Va85 and Mes44) and two susceptible lines (S: B73 and B79) were raised in a growth chamber together with the parental lines and exposed to 0,0×5 or 1 ng g−1, The interaction of reciprocal effects x rates was not significant for all traits, The T × S hybrids showed an intermediate response between the T × T and S × S responses for root‐length and dry weight. Interaction (hybrids vs. parental lines) × rates was not significant for all traits. These results indicate that susceptibility to chlorsulfuron is not controlled by extra‐nuclear factors and that additive gene actions prevail. Four crosses (one T × T, two T × S and one S × S) were further investigated at nine rates from 0 to 1 ng g−1. The responses confirmed the intermediate behaviour of T×S hybrids, resulting in a GR20 of 0×07, 0×55 and 0×94 ng g−1 for S × S, T × S and T × T, respectively. In a third experiment, the four crosses previously considered were grown in the field with parental lines and treated at five rates from 0 to 1·12 g a.i. ha−1. Effects on shoot height and dry weight were consistent with root effects found in growth chamber experiments.
Effects of shading and soybean Glycine max (L.) interference on Solanum ptycanthum (Dun.) (eastern black nightshade) growth and development
Authors: STOLLER E. W. , MYERS R. A.
Published: July 2006

Summary. Solanum ptycanthum (Dun.) vegetative and reproductive growth was evaluated under shade and in the field with soybean interference. In full sunlight without soybean interference, a S. ptycanthum plant produced 243 g shoots and 5957 berries in 20 weeks, but only 38 g and 576 berries in 11 weeks. Plants grown in 94% shade produced 3 g of shoots and 23 berries in 20 weeks, and 1 g and 1 berry in 11 weeks. S. ptycanthum plants that emerged with the soybeans and were positioned between 75‐cm rows produced 43 g shoots and 264 berries, whereas plants positioned in 75‐cm rows and emerging 6 weeks after the soybeans produced 1 g and 16 berries. When grown between 37·5‐cm rows for the same period of time this weed produced 12 g and 2 berries plant−1; plants positioned in 37·5‐cm rows produced shoots less than 1 g in weight and one berry plant−1. Shoot growth and berry production of S. ptycanthum increased from 80 to 200% in a 2‐week period between the initiation of soybean leaf abscission and maturity. In a season about 50 000 seeds weed−1 were produced in full sunlight; 20 000 or less were produced under soybean interference. When grown in irradiance levels from full sunlight to 94% shade, viable seeds were first detected 10 days after anthesis and essentially all seeds in the berry were viable 24 days after anthesis
Solarization; a physical control method for weeds and parasitic plants (Orobanche spp.) in Mediterranean agriculture
Authors: SAUERBORN J. , LINKE K‐H. , SAXENA M. C. , KOCH W.
Published: July 2006

Summary. Experiments were conducted between 1985 and 1988 to evaluate the effect of duration and time of solarization on the control of two broom rapes (Orobanche aegyptiaca Pers., O. crenata Forsk.) and other weeds common in the fields of faba bean (Vicia faba L.) and lentil (Lens culinaris Medik.) in West Asia. Solarization was performed by applying clear polyethylene sheet to the soil for 0, 10, 20, or 40 days in 1985/86, 0, 30, or 40 days in 1986/87 and 0, 20, 30, 40 or 50 days in 1987/88 during the hot season (July and August) and for 50 days immediately before sowing during milder weather (September and October) in 1986/87. Best control was obtained with solarization for 30–50 days in the hot season. Maximum soil temperature under polyethylene at 5 cm was 55°C in 1985, 48°C in 1986 and 57°C in 1987. Broomrape dry weight decreased in the first experiment by more than 90% in both faba bean and lentil fields. Solarization controlled broom‐rape and other weeds in the following two seasons when the soil was left undisturbed during the season of the treatment.
Einfluß des Zersetzungsgrades organischer Sub‐stanzen auf die Keimung von Striga hermonthica (Del.) Benth
Authors: COMBARI A. , PINEAU R. , SCHIAVON M.
Published: July 2006

De la poudre de cellulose ou des fragments de paille de blé sont mélangées á un substrat inerte (sable stérilisé). A l'issue de différents temps d'incubation (0 á 8 semaines) du substrat ainsi amendé des graines de sorgho sont semées et une extraction des exsudats racinaires et produits de décomposition des matiéres organiques est réali‐sée aprés deux semaines de culture. L'influence de ces extraits sur la germination de graines de Striga hermonthica (Del.) Benth. est la suivante: dans tous les cas, on assiste á une réduction importante du taux de germination au terme de 4 á 6 semaines d'incubation des produits organiques. Un effet stimulant de l'apport de paille est toutefois noté dans les premiéres semaines de sa dégradation. Une meilleure connaissance des mécanismes et processus de stimulation et d'inhibition liés aux apports de matiére organique devrait permettre une rationalisation des amendements en pays d'Afrique tropicale séche.
A model of the effects of cultivation on the vertical distribution of weed seeds within the soil
Authors: COUSENS R. , MOSS S. R.
Published: July 2006

A matrix model was constructed for the prediction of vertical seed movement within the soil. This was inserted into a model of the life‐cycle of Alopecurus myosuroides in order to predict seed population dynamics. Parameter values were obtained from published sources and from a single field cultivation experiment using coloured plastic beads. In simulations, stability of vertical distribution was reached sooner under ploughing than under rigid tine cultivation. Stable distributions were very different for the two cultivation methods, being reached by damped oscillations in the case of ploughing and asymptotically in the case of rigid tine cultivation.
The use of thermal calendar models to improve the efficiency of herbicide applications in Sorghum halepense (L.) Pers
Authors: GHERSA C. M. , SATORRE E. H. , VAN ESSO M. L. , PATARO A. , ELIZAGARAY R.
Published: July 2006

The dynamics of sprout emergence and rhizome populations of Sorghum halepense (L.) Pers. were followed in two field experiments. In addition, the herbicide dalapon was applied at various stages during rhizome development and the degree of control was evaluated. Rhizome biomass oscillated during the growth cycle, whereas the number of rhizome sprouts increased asymptotically until mid‐summer. Observed values were compared against those predicted from a thermal calendar model. The dynamics of the rhizome population was predicted accurately in both experiments, but only in one of them was the prediction of the sprout emergence satisfactory. The degree of control differed markedly between herbicide applications at various intervals during population development. Best results were obtained from applications when rhizome biomass was at a minimum. The time of minimum biomass was predicted by a thermal calendar model. The advantages of using the thermal calendar model to determine the time of herbicide application, and the possible influence of the distribution of the rhizome population in the soil profile on the predictions of the model, are discussed.
Efficacy of five different formulations of clopyralid on Cirsium arvense (L.) Scop, and Polygonum convolvulus L
Authors: KLOPPENBURG DAVID J. , HALL J. CHRISTOPHER
Published: July 2006

Experiments were conducted in a controlled environment growth room to compare the phytotoxicity of five formulations of clopyralid and to determine the effect of post‐treatment simulated rainfall applications on the efficacy of these formulations. Clopyralid, formulated as the acid, monoethanolamine salt, potassium salt, 2‐ethylhexyl ester or 1‐decyl ester was applied to Cirsium arvense or Polygonum convolvulus at the 8–10 and 4–6 leaf stage of development, respectively.

Based on the shoot and root dry weight data from both species, the 2‐ethylhexyl ester was consistently less phytotoxic than the other four formulations. With respect to Cirsium arvense shoot and root dry weight, there was no difference in efficacy between the acid, monoethanolamine salt, potassium salt and 1‐decyl ester. Root dry weight changes of Polygonum convolvulus did not correlate well with an increase in dose of the five formulations. Maximum increase in stem diameter of Polygonum convolvulus occurred after application of 100 g a.e. ha−1 of the acid, monoethanolamine salt, potassium salt and 1‐decyl ester whereas with the 2‐ethylhexyl ester, the maximum increase occurred after application of 200 g a.e. ha−1. Simulated rainfall was applied 3, 6, 9 or 12 h after application of 200 g a.e. ha−1 of the five clopyralid formulations to both species. Rainfall reduced the efficacy of clopyralid, regardless of the formulation or species. The 2‐ethylhexyl ester was less efficacious than the other four formulations, irrespective of the timing of simulated rainfall.
Growth behaviour and leaf morphology of Philippine strains of Sphenoclea zeylanica showing differential response to 2,4‐D
Authors: MERCADO B. L. , DE DATTA S. K. , MIGO T. R. , BALTAZAR A. M.
Published: July 2006

The germination and growth of three strains of gooseweed (Sphenoclea zeylanica Gaertn.) that showed susceptibility, moderate susceptibility, and tolerance for foliar‐applied 2,4‐D isobutyl ester were studied in the laboratory and greenhouse. The plants were isolated from samples collected from major rice (Oryza sativa L.) growing areas in the Philippines. The seeds of all three strains possessed dormancy; light stimulated germination but did not completely overcome dormancy. Without N application, stem elongation and leaf production did not differ among the strains. With 60 kg N ha−1, the susceptible and moderately susceptible strains responded better than the tolerant strain, the difference being apparent at 6 weeks after emergence. Measurements of the leaf cuticle showed significant differences among the strains starting at the 8‐ to the 10‐leaf stage, a trend that paralleled their response to 2,4‐D. Adding a surfactant to the spray formulation nullified the differential responses. Implications for managing the weed and correlations with current field observations are discussed.
Weed flora of dryland crops in the Córdoba region (Spain)
Authors: HIDALGO B. , SAAVEDRA M. , GARCIA‐TORRES L.
Published: July 2006

In a study of the weed flora of dryland crops in the Córdoba region (southern Spain) in 1983 and 1984, a total of 256 species from 41 families was identified in the 201 fields surveyed. The families with the highest numbers of species were Compositae, Gramineae, Leguminosae and Cruciferae. Therophytes represented 79% of the biological spectrum, with hemicryptophytes and geophytes more especially in the spring‐sown crops. At the early and late crop growth stages about 4% and 8%, respectively, of the fields had severe or very severe infestations. The seasonality of the crop had a marked influence on the weed flora, mainly due to the relationship of its phenological cycle with well defined climatic periods and to soil management practices. Cluster analysis clearly differentiated typically autumn‐spring and spring‐summer floras as well as a set of common species.
The influence of Agral 90 surfactant on the activity of imazamethabenz in wild oats (Avena fatua L.)
Authors: SMITH A.M. , CHOW P.N.P.
Published: July 2006

The influence of the nonionic surfactant, Agral 90, on the activity of imazamethabenz in wild oats (Avena fatua L.) was investigated in glasshouse and laboratory trials. Agral 90 significantly increased the efficacy of imazamethabenz against wild oats at a range of growth stages; a significant decrease in activity of both imazamethabenz alone or with Agral 90 was observed following application to plants possessing tillers. At 0.1 kg ha−1, the growth of tillers was significantly reduced by imazamethabenz plus Agral 90. The retention of imazamethabenz on wild oat foliage was significantly increased by Agral 90 incorporation; Agral 90 also facilitated retention of imazamethabenz on the tillers. The absorption and translocation of imazamethabenz were significantly enhanced by Agral 90; greater amounts of the labelled material were found in all regions of the plant except the tillers which existed at the time of application.
Utilisation de I'isoproturon, seul et en association avec d'autres matiires en actives, en post levée à I'automne at en printemps, sur blé et orge d'hiver. II. Effets secondaires sur I'activiti de la déshydrogénase, la transformation de V azote et la décomposition des chaumes dans le sol
Authors: BERGER B. , HEITEFUSS R.
Published: July 2006

In einem zweijährigen Feldversuch auf zwei Standorten wurde der Einfluß von Isoproturon, allein und in Kombination mit Dinoseb–acetat und Bifenox, auf die Dehydrogenaseaktivität, den Stickstoffumsatz und den Strohabbau im Boden nach einer Anwendung im Nachauflauf Winter (NA–W) und Nachauflauf–Frühjahr (NA–F) zu Winterweizen und Wintergerste untersucht. Isoproturon rief vorübergehend geringe Stimulationen aber auch Hemmungen der Dehydrogenaseaktivität um maximal 40% und des Stickstoffumsatzes um 70–90% hervor. Dinoseb–acetat führte zu Reduktionen der allgemeinen Stoffwechselaktiviät um bis zu 30%. Die Ammonium– und Nitritkonzentrationen lagen zeitweise um mehr als 100%über den Kontrollwerten. Im Labor hatte Isoproturon bei den zu diesen Terminen herrschenden Temperatur– und Feuchtebedingungen nur in wenigen Fällen einen Einfluß auf die Dehydrogenaseaktivität, nach Applikation dereinfachen Aufwandmenge von Dinoseb–acetat war die Aktivität aber um bis zu 50% reduziert. Im Sandboden waren die Herbizideffekte deutlicher ausgeprägt als im Lehmboden. Ein Einfluß der Behandlungstermine auf die durch die Herbizide bedingten veränderten mikrobiellen Aktivitäten wurde nur in den Freiland–versuchen deutlich.
Enhanced degradation of some soil‐applied herbicides
Authors: WALKER A. , WELCH SARAH J.
Published: July 2006

In a field experiment involving repeated herbicide application, persistence of simazine was not affected by up to three previous doses of the herbicide. With propyzamide, there was a trend to more rapid rates of degradation with increasing number of previous treatments. Persistence of linuron and alachlor was affected only slightly by prior applications. In a laboratory incubation with soil from the field that had received four doses of the appropriate herbicide over a 12–month period, there was again no effect from simazine pretreatments on rates of loss. However, propyzamide, linuron and alachlor all degraded more rapidly in the previously treated than in similar untreated soil samples. Propyzamide, linuron, alachlor and napropamide degradation rates were all enhanced by a single pretreatment of soil in laboratory incubations, whereas degradation rates of isoproturon, metazachlor, atrazine and simazine were the same in pretreated and control soil samples.
Uptake, translocation and fate of 2,4‐D and chlorsulfuron in Silene vulgaris (Moench) Garcke
Authors: WALL D. A. , HALL J. C. , MORRISON I. N.
Published: July 2006

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.
Influence of 1‐aminobenzotriazole (ABT) derivatives on the toxicity of EPTC to monocotyledonous plants
Authors: BARTA I. Cs. , DUTKA F.
Published: July 2006

The effect of l‐aminobenzotriazole (ABT) and EPTC mixtures on plant growth was investigated in greenhouse experiments by presowing application in sand. The concentration of ABT for 50% shoot growth inhibition (I50) was about 1 mM in the monoctyledons investigated. Both subtoxic and toxic doses of ABT were antagonists of EPTC in maize (Zea mays L.) However, subtoxic doses of ABT were syner‐gists of EPTC in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.). No correlation between ABT and EPTC sensitivity of monocotyledonous plants was found. Some of the C‐ and N‐substituted ABT derivatives (e.g. N‐methyl or N‐benzyl‐ABT) completely reversed the effect of toxic dose of EPTC in maize. These results are considered as indirect evidence for the hypothesis that oxidation by cytochrome P‐450 enzymes is the biochemical target of EPTC and is involved in the mode of action of EPTC safeners.
Soybean yield and yield components as influenced by canopy heights and duration of competition of velvetleaf (Abutilon theophrasti Medik.)*
Authors: BEGONIA G. B. , ALDRICH R. J. , SALISBURY C. D.
Published: July 2006

Soybean yields, pod and branch numbers were inversely related to the height of velvetleaf (Abutilon theophrasti). This effect was attributed to increasing interception of light with increasing height of A. theophrasti. Reduction; in soybean yield and yield components were greater if A. theophrasti was maintained at various heights for only 3 weeks rather than 6 weeks following soybean emergence. This effect was attributed to a longer duration of light competition by the weed. Even when the A. theophrasti canopy was kept 25% below that of soybean for 4 weeks, soybean yields, pod and branch numbers decreased when the weed was allowed to regrow during the remainder of the season, but not if the weed was removed after the initial 4‐week clipping period. No reduction in seed yields, pod and branch numbers was noted if A. theophrasti plants 25% shorter than soybeans were removed or allowed to resume growth after the initial 6 or 8 weeks of clipping. Soybean seed size was slightly affected by A. theophrasti canopy height and duration of competition.
Reduction of growth and reproduction of Cyperus esculentus by specific crops
Authors: LOTZ L.A.P. , GROENEVELD R.M.W. , HABEKOTTÉ B. , VAN OENE H.
Published: July 2006

To assess the potential contribution of growing highly competitive crops to control Cyperus esculentus in the Netherlands, the influence of silage maize, hemp, winter barley and silage winter rye on emergence, growth and reproduction of this weed was studied in two field experiments. Growth and reproduction of C. esculentus (determined both as tuber production per plant and density of the weed in the subseuent crop maize) was reduced by each crop, compared to plots in which no crop was grown. In hemp, hardly any tuber production was observed. By growing a green manure crop after harvest of the winter barley the tuber production of the weed was reduced to about 40% of that in winter barley followed by fallow. Decreasing the light regime in a greenhouse experiment in the same order as was observed in the crops winter barley, maize and hemp, caused a similar reduction of tuber production to that found in the field. Therefore, it is suggested that competition for light is the main factor explaining the observed crop effects on the population dynamics of the weed. It is concluded that growing competitive crops as hemp in rotation may effectively complement chemical control of C. esculentus.
Effects of nitrogen fertilizer and emergence date on root and shoot competition between wheat and blackgrass
Authors: EXLEY D. M. , SNAYDON R. W.
Published: July 2006

Summary: Résumé: Zusammenfassung

Competition between wheat and blackgrass (Alopecurus myosuroides Huds.) was studied in two experiments, where the effects of root competition and shoot competition were separated using an additive design. The effects of the following factors on root and shoot competition were investigated: weed density, N fertilizer, crop sowing date (October and November) and weed emergence date (October to April). Root competition generally affected the growth of both wheat and blackgrass more than did shoot competition, although shoot competition affected the survival of blackgrass more than did root competition. N fertilizer partially alleviated the effects of root competition, but did not affect shoot competition. Later sowing of either wheat or blackgrass, relative to the other, reduced the competitive ability of the later‐sown species, particularly under conditions of root competition.

Effets de la fertilisation azotée et de la date de levée sur la compétition racinaire et foliaire entre le ble et le vulpin

La compétition entre du blé de printemps et du vulpin (Alopecurus myosuroïdes) a étéétudiée dans deux essais, ou les effets de la competition racinaire et de la compétition aérienne ont été séparés en utilisant un systéme additif. Les effets des facteurs suivant ont étéétudiées pour les deux sortes de compétition: densité d'adventices, fertilisation azotée, date de semis (octobre et novembre) et date de levée de l'adventice (octobre—avril). La compétition racinaire a affecté généralement la croissance du blé et du vulpin de façon plus conséquente que la compétition aérienne, bien que la compétition aérienne affectât plus la survie du vulpin que la compétition racinaire. La fertilisation azotée a partiellement réduit les effets de la compétition racinaire, mais n'a pas affecté la compétition aérienne. Le semis plus tardif, soit du blé, soit du vulpin, par rapport à l'autre, a réduit la competitivite de l'espéce semée le plus tardivement, spécialement sous les conditions de competition racinaire.

Einfluß von Stickstoffdüngung und Keimperiode auf die Wurzel‐ und Sproβkonkurrenz zwischen Weizen und Acker‐Fuchsschwanz

Die Konkurrenz zwischen Sommerweizen und Acker‐Fuchsschwanz (Alopecurus myosuroides Huds.) wurde in 2 Versuchen untersucht, in denen mit einer additiven Versuchsanordnung die Wirkung der Wurzel‐ und der Sproßkonkurrenz unter den Faktoren Unkrautdichte, N‐ Düngung, Saatzeit (Oktober und November) und Keimperiode des Unkrauts (Oktober bis April) getrennt erfaßt wurde. Die Wurzelkonkurrenz beeinflußte das Wachstum sowohl des Weizens als auch des Acker‐Fuchs schwanzes mehr als die Sproßkonkurrenz, während auf die Weiterentwicklung des Acker‐Fuchsschwanzes die Sproßkonkurrenz mehr als die Wurzelkonkurrenz wirkte. Eine spätere Aussaat entweder des Weizens oder des Unkrauts verminderte die Konkurrenzkraft der später ausgesäten Art, besonders hinsichtlich der Wurzelkonkurrenz.
Response of weeds to the method of fertilizer application on low‐fertility acid soils in Suriname
Authors: EVERAARTS A. P.
Published: July 2006

Summary: Résumé: Zusammenfassung

The effect of broadcast or band‐placed application of fertilizer on the growth of weeds was studied at two locations on low‐fertility acid soils in Suriname. Band placement of fertilizers considerably reduced weed growth compared to fertilizer‐applied broadcast. With band‐placed fertilizer the increased weed growth due to fertilizer application was concentrated on the fertilized bands. Weed growth was also stimulated in planter wheel‐tracks. The spatial distribution of the weed growth is discussed in relation to the crops groundnut, sorghum and soybean, grown at the same location.

Réponse des adventices au mode d'application des engrais sur des sols acides de faible fertilité au Surinam

L'effet d'application d'engrais sur le rang ou en plein sur la croissance des mauvaises herbes a étéétudiée en deux lieux du Surinam sur sols acides pauvres. Le traitement sur le rang des engrais a considérablement réduit la croissance des adventices comparéà l'application en plein. Avec l'application de l'engrais en ligne l'augmentation de croissance due à la fertilisation était concentrée sur les bandes fertilisées. La croissance des adventices étaient également stimulée dans les traces de roues de tracteurs. La distribution spatiale de la croissance des adventices est discutée en relations avec la distribution spatiale de la croissance des adventices trouvé chez le sorgho, le soja, l'arachide cultivés dans les mêmes lieux.

Wirkung der Düngungsmethode auf die Verunkrautung ertragarmer, saurer Böden in Surinam

An 2 Ortem mit ertragarmen, sauren Böden in Surinam wurde die Wirkung der Düngungs‐methode auf das Wachstum von Unkräutern untersucht. Banddüngung reduzierte das Unkrautwachstum im Vergleich zur breitwürfigen Düngung erheblich. Ein gefördertes Unkrautwachstum zeigte sich nur auf dem Döngungsband und auch auf den Fahrspuren. Die unterschiedliche Verunkrautung in Erdnuß, Sorghum und Sojabohne wird diskutiert.
Effects of herbicide mixtures and additives on Rhododendron ponticum
Authors: LAWRIE J. , CLAY V.
Published: July 2006

Summary: Résumé: Zusammenfassung

The possibility of increasing the activity of glyphosate, imazapyr, sulfonylurea herbicides and triclopyr against Rhododendron ponticum L. was investigated using container‐grown plants. Glyphosate, imazapyr and triclopyr alone and metsulfuron‐methyl with added surfactant were all phytotoxic, imazapyr and triclopyr being the most effective at the doses used. Thifensulfuron‐methyl and tribenuron‐methyl with ‘Mixture B’ were ineffective. The surfactants ‘Mixture B’ and ‘Silwet L77’ consistently increased the activity of imazapyr and metsulfuron‐methyl. Mixtures of the herbicides did not lead to synergistic activity, and mixing imazapyr and triclopyr depressed the activity of each component. There was some enhancement of activity on R. ponticum when imazapyr and metsulfuron‐methyl were applied sequentially, 48 h apart.

Effets de mélanges d'herbicides et d'adjuvants au Rhododendron ponticum

La possibilité d'accroître l'activité du glyphosate, de l'imazapyr, des sulfonylurées et du triclopyr contre Rhododendron ponticum a étéétudiée en utilisant des plantes cultivées en containers. Le glyphosate, l'imazapyr et le triclopyr seuls et le metsulfuron‐methyl additionné d'un surfactant ont tous été phytotoxiques: l'imazapyr et le triclopyr étant les plus efficaces aux doses utilisées. Le thifensulfuron‐méthyl et le tribenuron‐methyl avec ‘Mixture B’ ont été inefficaces. Les surfactants ‘Mixture B’ et‘Silwet L 77’ ont considérablement augmenté l'activité de l'imazapyr et metsulfuron‐methyl. Les mélanges des herbicides n'a pas abouti à une activité synergistique et les mélanges avec l'imazapyr et le triclopyr ont diminué l'activité de chaque composé. Il y a eu un certain renforcement de l'activité sur R. ponticum quand l'imazapyr et le métsulfuron‐méthyl étaient appliqués de façon séquentielle, à 48 heures d'intervalle.

Wirkung von Herbizidmischungen und Additiven auf Rhododendron ponticum

An Container‐Pflanzen von Rhododendron ponticum L. wurden versucht, die Wirksamkeit von Glyphosat, Imazapyr und Sulfonylharn‐stoff‐Herbiziden zu verstärken. Glyphosat, Imazapyr und Triclopyr allein und Metsulfuron‐methyl nach Zugabe von Netzmitteln waren phytotoxisch, besonders Imazapyr und Triclopyr. Thifensulfuronmethyl und Tribenuron‐methyl waren mit dem Netzmittel ‘Mixture B’ wirkungslos. Die Netzmittel ‘Mixture B’ und ‘Silwet L77’ erhöhten die Wirksamkeit von Imazapyr und Metsulfuron‐methyl durchweg. Mischungen der Herbizide ließen keinen Synergismus erkennen, und die Mischung von Imazapyr mit Triclopyr verringerte die Wirksamkeit der Einzelkomponenten. Die Wirkung auf R. ponticum ließ sich erhöhen, wenn Imazapyr und Metsulfuron‐methyl 48 h nacheinander angewandt wurden.