Soil dissipation of the herbicide isoxaben after use in cereals

The soil dissipation of the herbicide isoxaben was studied in field trials in Belgium in winter cereals treated with green manure, cow manure or pig slurry before sowing. Wheat was sown and the soil sprayed with 125 g isoxaben ha^?1 in October. Soil samples were analysed by GLC. Isoxaben dissipated with first-order kinetics over the first 6 months with half-lives of 2.9, 4.0, 4.8 and 6.6 months in unamended plots, and plots treated with green manure, cow manure and pig slurry respectively. The organic fertilizer treatments thus increased the isoxaben soil persistence. After 6 months, the organic fertilizer effect was less pronounced, leading to isoxaben soil concen-trations in all treatments becoming similarly low. Isoxaben at 75 gha^?1 applied to winter wheat or barley in the spring gave dissipation half lives of 2.1 and 2.4 months, leading to isoxaben soil residues at the beginning of August of 15–21 p.p.b., similar to levels resulting from the autumn appli-cation. The isoxaben soil residues remaining after harvest would be too low to damage a rotational crop. The rates of isoxaben soil dissipation were greater in the spring and summer seasons than during the winter. The dissipation rates of autumn-applied isoxaben were also studied in spring-sown sugar beet and the effects on a variety of springsown rotational crops were investigated. Dissipation dans le sol de I'herbicide isoxaben en culture de céréales La dissipation dans le sol de I'herbicide isoxaben a étéétudiée dans des essais de plein champ, en Belgique, en culture de céréales d'hiver ayant eu avant le semis un engrais vert, un apport de fumier de vache ou de lisier de pore. Le blé a été semé et le sol traité avec 125 g d'isoxaben ha^?1en octobre. Les échantillons ont été analysés par GLC. L'isoxaben s'est dégradé pendant les pre-miers mois avec des demi-vies respectives de 2,9, 4,4,8 et 6,6 mois dans les parcelles sans amende-ments, les parcelles avec engrais vert, fumier et lisier. Les amendements organiques ont augmenté la persistance de l'isoxaben dans le sol. Après 6 mois, l'effet des amendements organiques a été moins prononcé, aboutissant à des concentrations d'isoxaben basses et voisines pour tous les traitements. L'isoxaben a 75 g ha^?1 appliquéà du blé d'hiver et de l'orge au prin-temps a donné des demi-vies de 2,1 et 2,4 mois, aboutissant à des résidus d'isoxaben dans le sol début août de 15–21 ppb, comparables aux taux resultant d'une application automnale. Les résidus d'isoxaben dans le sol restant après la moisson seraient trop faibles pour endommager une culture suivante. Le taux de dégradation dans le sol de l'isoxaben a été plus é1evé au prin-temps et en été qu'en hiver. Le taux de dégrada-tion de l'isoxaben appliqué en automne a étéégalement étudié sur des betteraves semées au printemps et les ef fets sur plusieurs cultures dans le cadre de la rotation ont étéétudiés. Rückstandssituation von Isoxaben im Boden nach Applikation in Getreide Die Rückstandssituation des Herbizids Isoxaben im Boden wurde in Freilandstudien in Wintergetreide nach Gründüngung, Ausbringung von Stallmist bzw. Schweinegülle untersucht. Das Herbizid wurde im Oktober im Nachsaatverfahren mit 125 g Isoxaben ha^?1 angewandt, und die Bodenproben wurden gaschromatographisch analysiert. Das Herbizid wurde über die ersten 6 Monate nach einer Kinetik 1. Ordnung mit “Halbwertszeiten” von 2,9 Monaten im Ausgangsboden, 4,0 Monaten nach der Gründung und 4,8 bzw. 6,6 Monaten in der Stallmist-bzw. Gülle- Variante abgebaut. Durch die organischen Düngungen wurde also die Persistenz des Herbizids im Boden erhöht. Nach 6 Monaten lieβ die Wirkung der Dünger nach, so daβ vergleichbar niedrige Rückstände gefunden wurden. Bei der Nachauflaufbehandlung von Winterweizen und -gerste im Frühjahr mit 75 g Isoxaben ha^?1 lagen die Werte für einen 50% igen Rückgang der Ausgangskonzentration bei 2,1 bzw. 2,4 Monaten, und es ergaben sich Anfang August vergleichbar hohe Werte von 15 bis 21 ppb wie bei den Herbstbehandlungen. Diese Rückstände würden zu keinen Schäden an Nachbaukulturen führen. Die Verlustraten waren prozentual über Winter geringer als im Frühjahr. Sie wurden auch in Zuckerrüben untersucht, desgleichen ihre Wirkung auf verschiedene im Frühjahr angebaute Nachbaukulturen.     

Seed dispersal, distribution and recruitment of seedlings of Sorghum halepense (L.) Pers.

Patteras of seed dispersal and seedling recruit ment of Sorghum halepense (L.) Pers. were compared in abandoned and cultivated fields in Argentina. In both the abandoned and cultivated plots, the greatest concentration of seed fell below, or only a short distance, from the parent plants. A maize combine harvester greatly increased the distance of dispersal of a small part of the seed population. The availability of seed for dispersal, the direction and velocity of wind and the combine harvester were important factors determining the temporal and spatial patterns of seed distribution. The ratio of recruited seedlings to seeds shed was only 1% under the parent plant, but increased to about 100% at a distance of 1.25 m. Soil tilling, which is required for seedling recruitment, and seed density were important factors in determining seedling density as the distance from the parent plants increased. The rate of seedling recruitment was higher in areas where most of the seeds were dispersed late in the season than in those where dispersal occurred early. Dispersion des graines, distribution et reprise des plantules de Sorghum halepense (L.) Pers. Les schémas de dispersion des graines et de reprise des plantules de Sorghum halepense (L.) Pers. ont été comparés dans des champs abandonnés et d'autres cultivés en Argentine. Tant dans les parcelles abandonnées que cultivées, la plus grande concentration de graines tombe sous ou seulement à une faible distance des plantes parentes. Une moisonneuse à maïí a grandement augmenté la distance de dispersion d'une petite partie de la population grainière. La disponibilité des graines pour la dispersion, la direction et la vitesse du vent, et la moissonneuse ont été d'importants facteurs de détermination pour les schémas de distribution spatiale et temporaire. Le ratio de reprise de plantule était seulement de 1% sous les plantes parentes mais augmentait jusqu'à près de 100%à une distance de 1, 25 m. Le travail du sol, qui est nécessaire pour la reprise des plantules, et la densité grainière étaient d'importants facteurs dans la détermination de la densité des plantules quand la distance des plantes parentes augmente. Le taux de reprise des plantules était plus élevé dans les zones où la majorité des graines était dispersée tard en saison que dans celles où la dispersion avait eu lieu tôt. Ausbreitung der Samen sowie Verbreitung und Entwicklung der Keimpflanzen von Sorghum halepense (L.) Pers. Ausbreitung der Samen und Entwicklung der Keimpflanzen von Sorghum halepense (L.) Pers. wurden in Argentinien auf brachliegenden und kultivierten Feldern untersucht. In beiden Situationen fanden sich die größten Samendichten unter oder nahe der Mutterpflanzen. Mit einem Mais-Mähdrescher wurde ein kleiner Teil der Samenpopulation erheblich ausgebreitet. Die Verfügbarkeit von Samen für die Ausbreitung, die Windrichtung und-geschwindigkeit und der Mähdrusch waren wichtige Faktoren für das zeitliche und räumliche Verbreitungsmuster, Unter den Mutterpflanzen keimten die Samen nur zu 1%, aber 1,25 m entfemt zu fast 100%. Bodenbearbeitung und Samendichte bestimmten die Keimpflanzendichte mit zunehmender Entfernung von der Mutterpflanze erheblich. Die Entwichlungsrate spät ansgebreiteter Samen war höher als die früh ausgebreiteter.     

Formation and persistence of metabolites of imazamethabenz-methyl in a sandy loam soil

The fate of imazamethabenz-methyl was studied in a sandy loam soil after application in spring to winter wheat (Triticum aestivum L.). Imazamethabenz-methyl and its metabolite 2 (2-(4, 5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-1H-imidazol-2-yl)-4-methylbenzoic acid, in mixture with the 5-methylbenzoic acid isomer) were further transformed into the metabolites 3 (2-(4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-¹H-imidazol-2-yl)-l,4-benzenedicarboxylic acid, in mixture with the 1,5-benzenedicarboxylic acid isomer), and 4 (1,2,4-benzenetricarboxylic acid, in mixture with the 1,2,5-isomer). Meta-bolites 3 and 4 reached maximum concentration levels in the 0–13 cm layer corresponding to 14–17% and 9–14% of the imazamethabenz-methyl dose, respectively. These maxima were reached between 105 and 177 days after application. Imazamethabenz-methyl metabolism was slower in plots treated with organic fertilizers than in untreated plots. After 196 days the concentrations of all metabolites in the 0–13 cm layer had declined to, at most, 0.01 mg kg^?1. There was no carry-over of residues that could be phytotoxic to the next crop. Formation et persistance dés metabolites de l'imazaméthabenz-méthyl dans un sol sablolimoneux La métabolisation de l'imazaméthabenz-méthyl a étéétudiée dans un sol sablo-limoneux après application sur une culture de froment d'hiver (Triticum aestivum L.) L'imazaméthabenz-méthyl et son métabolite 2 (2-(4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-^?1H-imidazol-2-yl)-4-methylbenzoïque acide, en mélange avec 1'isomère 5-methylbenzoïque acide) sont trans-formés ultérieurement en métabolites 3 ((2-(4,5-dihydro-4-methyl-4- (l-methylethyl)-S- oxo -^?1H-imidazol-2-yl)-l,4-benzenedicarboxylique acide, en mélange avec l'isomère 1,5-benzenedicar-boxylique acide) et 4 (1,2,4-benzenetricarboxy-lique acide, en mélange avec le 1,2,5- isomère). Les concentrations dans la couche de sol de 0–13 cm de profondeur des métabolites 3 et 4 at-teignent des maximums qui correspondent re-spectivement à 1,4–17% et 9–14% de la dose initiate en imazamethabenz-methyl. Ces concentrations maximales sont atteintes entre les 105 et 177 jours qui suivent 1'application. La métabolisation de rimazaméthabenz-méthyl est plus lente dans les parcelles trailées par des fetilisants organiques, que dans les parcelles non traitées par ces fertilisants. Après 196 jours, les concentrations de tous les métabolites dans la couche de sol de 0–13 cm ont diminué jusqu' à 0.01 mg kg^?1 ou moins. Dans ces conditions, en fin de culture il n'est pas resté dans le sol de résidus qui auraient pu être phytotoxiques à la culture suivante. Bildung und Persistenz von Metaboliten des Imazamethabenz-methyl in einen sandigen Lehmboden Nach der Applikation von Imazamethabenz-methyl in Winterweizen (Triticum aestivum L.) wurde sein Abbau untersucht. Das Herbizid und seine Metaboliten 2, die isomeren 2-(4, 5-Dihydro-4-methyl-4 (1-methylethyl)-5-oxo-¹ Himidazol-2-yl)-und -5-methylbenzoesäure, wurden weiter zu den Metaboliten 3, die isomeren-1,4-und-l,5-benzendicaboxylsäure, und 4, die isomeren 1,2,4- und 1,2,5-benzentricarboxylsäure, transformiert. Die Metaboliten 3 und 4 hatten ihre höchste Konzentration in 0 bis 13 cm Bodentiefe und entsprachen 14 bis 17 % bzw. 9 bis 14 % der Imazamethabenzmethyl-Dosis. Diese Maxima wurden zwischen 105 und 177 d nach der Applikation erreicht. In organisch gedüngten Parzellen war der Abbau langsamer als in ungedüngten. Nach 196 d war die Konzentration aller Metaboliten in 0 bis 13 cm Bodentiefe auf höchstens 0,01 mg kg¹ zurückgegangen, so daß für die Folgekultur keine phytotoxischen Rückstände mehr vorlagen.     

Current status of biological control of paddy weeds in Vietnam

Rice is a staple food in Vietnam and accounts for > 7.7 × 10⁶ cultivated ha, which provide 35.5 × 10⁶ t of rice, of which 4.2 × 10⁶ t were exported in 2004. The enlargement of the cropping area and the enhancement of rice yield have rapidly increased the amount of agrochemicals, including herbicides, in crop production in Vietnam. From 1990–2003, the percentage of herbicides in total pesticides has increased ≈ 10-fold to 30.2%. In addition, the improper use of herbicides caused environmental hazards, unsafe agricultural products, and human health problems. Biological management integrated with traditional weed control techniques might help to reduce the dependence on synthetic herbicides and build eco-friendly, sustainable agricultural production in Vietnam. This paper reviews the efforts in establishing a strategy for biological management of weeds that was conducted in recent years by Vietnamese weed scientists. This has included cropping system management, water and soil management, integrated pest management, and utilization of plant allelopathy as major components of the strategy. Many plants with strong allelopathic potential can be a source for biological weed suppression and soil fertility improvement. The utilization of allelopathic properties in rice might also help to provide new rice cultivars with weed-suppressing characteristics.     

COMPUTED TOMOGRAPHY OF CHOLESTERINIC GRANLOMAS IN THE CHOROID PLEXUS OF HORSES

Cholesterinic granulomas are tumor-like masses in the choroid plexuses of horses. This report describes the computed tomographic findings in four horses with cholesterinic granulomas, including the clinical and the pathologic features. All four horses had bilateral cholesterinic granulomas in the lateral ventricles. Computed tomographic images clearly delineated the masses, the opacity of the granulomas, and the enhancement pattern after intravenous bolus injection of contrast medium; these factors varied considerably. Additional CT findings were symmetric or asymmetric widening of the lateral ventricles.     

Verification of immunofluorescence colony-staining of Erwinia carotovora subsp. atroseptica by reisolation and immunodiffusion or PCR

In this study, the reliability and efficiency of three procedures for verification of IFC-positive colonies of Erwinia carotovora subsp. atroseptica were compared: (1) PCR amplification, (2) reisolation on a non-selective medium (trypticase soy agar) followed by direct immunodiffusion (TSA-DID), developed for isolation of target and cross-reacting bacteria, and (3) reisolation on a selective medium (crystal-violet pectate) and characterization of selected isolates with Ouchterlony double diffusion (DLCVP-ODD), developed for isolation of pectinolytic Erwinia spp. The reliability of a PCR amplification procedure for characterization of E.c. atroseptica was evaluated. Specific amplification products could be produced from DNA of all 187 European strains of the bacterium, while no amplification products were obtained from DNA of four distinctive serological groups of bacteria cross-reacting with antibodies against E.c. atroseptica , nor from DNA of randomly selected saprophytic bacteria isolated from potato peel extracts. All 60 immunofluorescent-positive target colonies from a potato peel extract with added E.c. atroseptica tested were positive by PCR compared with 68 and 72% successful determinations by TSA-DID and DLCVP-ODD, respectively. PCR enabled verification of fluorescent colonies from IFC preparations of naturally infected seed lots with an efficiency of 93%, compared with 48 and 71% successful determinations by TSA-DID and DLCVP-ODD, respectively. It is concluded that PCR is useful for routine confirmation of the identity of fluorescent colonies in IFC.     

Mandibular Osteodistraction for Correction of Deep Bite Class II Malocclusion in a Horse

Objective— To describe a technique for, and outcome after, mandibular osteodistraction in the horse.
Study Design— Clinical report.
Animals— Warmblood horse.
Methods— A half ring external fixator was applied on both sides of an osteotomy site performed on the mandible of a colt. A bite plate was placed on the upper incisors creating occlusion between lower and upper jaw. After a 5-day latency period, distraction was applied (1 mm/day) until the overjet was judged normal.
Results— Mandibular elongation and correction of brachygnathia was obtained without major complications. Six months after the procedure the overjet reduction was considered stable.
Conclusions— Mandibular osteodistraction can be considered for treatment of severe brachygnathia in yearlings.
Clinical Relevance— Distraction osteogenesis has the advantage of progressive elongation of the mandible, allowing concurrent bone remodeling and soft tissue adaptation. Severe mandibular incisor malocclusion in horses outside the maximal growth phase can be corrected using this technique.     

Effect of stale seedbed preparations and subsequent weed control in lettuce (cv. Iceboll) on weed densities

The effects of stale seedbed preparations and several weed control methods on the emergence of weeds in lettuce were studied. The specific goal was to evaluate the use of a stale seedbed in combination with chemical or mechanical weed control methods in the field. Depending on location and year, stale seedbed preparations followed by weed control prior to planting reduced the amount of weeds during crop growth by 43–83%. Control of the emerged seedlings after a stale seedbed preparation was more effective with glyphosate than with a rotary harrow. Covering the rotary harrow during control to prevent light reaching the soil improved its effect on the weed density during crop growth in two of 3 years. Radiation with far red light (FR) did not reduce the number of emerging weeds in this study. Mechanical control by finger weeder, torsion weeder and hoe was applied without stale seedbed preparations. These measures reduced the weed densities by 88–99%, compared with the untreated control and were more effective than chemical weed control with carbetamide and chlorpropham. The results show that the stale seedbed technique in combination with mechanical control of emerging weeds can reduce the weed population during crop growth as effectively as chemical control. The technique may therefore help reduce the use of herbicides in lettuce crops in the future.