Inducción de fluorescencia en pino. Respuesta de Pinus halepensis Miller, P. nigra Arnold y P. pinaster Aiton a los herbicidas hexazinona y simazina

The first phases of the development of pines could be affected by weed competition. The use of herbicides is fundamental for weed control but herbicide treatment must be safe for pines. This work study the effect of two herbicides, hexazinone and simazine, over three pine species Pinus halepensis, P. nigra and P. pinaster by means of measures of the fast phase of the chlorophyll fluorescence induction kinetics. The study is conducted in early caulinars leaves of pine treated for 48 hours with doses of 2 and 4 ppm of each herbicide. Herbicide treatment and recovery of plants was done under hydroponics conditions in climatic chamber. P. nigra was more tolerant than P. pinaster and P. halepensis to hexazinone. There were no differences between species in simazine response. The three pine species show better recovery of photosynthetic activity in hexazinone treatments than in simazine treatments, indicating better tolerance of tree to hexazinone than to simazine.Las primeras fases del desarrollo de pinos pueden verse afectadas por la competencia de las malas hierbas, siendo la utilización de herbicidas fundamental para su control, aunque este tratamiento no debe afectar al pino. En este trabajo, se estudia el efecto de dos herbicidas simazina y hexazinona en tres especies de pino, Pinus halepensis, P. nigra y P. pinaster, mediante medidas de la fase rápida de la cinética de inducción de fluorescencia clorofílica. El estudio se lleva a cabo sobre las primeras hojas caulinares de pino, sometidos a tratamiento con dosis de 2 y 4 ppm de cada uno de los herbicidas durante 48 horas. El tratamiento y la posterior recuperación, se lleva a cabo en cultivo hidropónico en cámara climática. En los tratamientos con hexazinona, P. nigra ha resultado más tolerante que P. pinaster y P. halepensis. No se han encontrado diferencias entre especies en la respuesta a simazina. En las tres especies de pino se produce una mayor recuperación de la actividad fotosintética, lo que indica una mayor tolerancia del árbol, a hexazinona que a simazina

Study of clethodim degradation and by-product formation in chlorinated water by HPLC

Two of the most commonly used chlorinating agents for water disinfection, hypochlorite and chloramines, were employed to investigate the degradation of clethodim in conditions simulating tap water treatment. The main clethodim degradation products were identified by using liquid chromatography (LC) coupled with mass spectrometry (MS). The main degradation process was oxidation to sulfoxide and then to sulfone. Degradation half-life was calculated for both parent clethodim and the first degradation product, clethodim sulfoxide. Whereas some other different minor by-products were identified when the degradation occurs with either sodium hypochlorite or chloramines, no other chlorinated by-products were found under the conditions tested. © 2005 Friedr. Vieweg & Sohn/GWV Fachverlage GmbH

Ecological risk assessment of pesticides in the Mediterranean region. The need for crop-specific scenarios

The risk assessment procedures of pesticides in the European Union are mostly based on worst-case scenarios developed for central and northern European conditions. From the point of view of Mediterranean conditions, these assessment procedures are not always appropriate, and therefore the development of specific scenarios is required. There are differences not only in meteorological data (temperature, solar irradiation, or rainfall volume and annual distribution) between these countries, but also in farm distribution, crop characteristics, soil or sediment properties and surface or groundwater characteristics. These differences are more evident for the typical crops of the southern countries, such as olive groves, vineyards, citrus or rice fields, and in these cases more realistic estimates of exposure are required. Our proposal includes the development of new criteria to improve the ecological risk assessment process for the conditions of the Mediterranean region, and the justification of this need. Copyright (C) 2000 Elsevier Science B.V

Assessment of the effect of broad-spectrum pre-emergence herbicides in poplar nurseries

This study examines the response of three pre-emergence herbicides (tiazopir, oxifluorfen, pendimethalin) used on unsprouted cuttings of the clone 'I-214' (Populus x euramericana). The effect of the herbicide both on the poplar and on the weeds was assessed. The three herbicides performed well in the case of both the variables (selectivity and effectiveness). The development of the trees were recorded over two growing seasons, during which there was a chemical intervention in the first year, but no treatment during the second year. A second application of these herbicides does not seem to be needed from the point of view of competition between the weeds and the cultivated crop. © 2001 Elsevier Science Ltd

Control de malas hierbas en viveros de chopo mediante la aplicación de herbicidas

Se estudia la respuesta de cinco herbicidas de preemergencia (Oxadiazon, Isoxaben, Oxifluorfen, Tiazopir y Pendimetalina) sobre estaquillados de chopo sin brotar en condiciones de vivero. Para evaluar cuantitativamente la selectividad y la eficacia de los tratamientos herbicidas, se consideró la altura de los árboles, así como el peso seco de la hierba presente. Se identificaron las especies y se valoró su presencia en los tratamientos. El control de la flora adventicia fue satisfactorio en todos los viveros ensayados, con la excepción de Stellaria media (L.) Vill, cuando se aplicó Oxadiazon. No se apreciaron síntomas fitotóxicos significativos en las plantas de chopo para ninguno de los herbicidas ensayados

Determination of chlorotoluron, isoproturon and metoxuron in soil by GLC-NPD and confirmation using GLC-MS

The analysis of several phenyl urea herbicides in soil by GLC-NPD, directly or after alkylation, and the confirmation of residues by GLC-ITD is reported. Soil was extracted with methanol, the organic solvent evaporated, the residue dissolved in hexane and then analyzed by gas chromatography on a 3% OV-17 glass packed column. An aliquot of the extract was ethylated overnight with EtI, NaH and Me2SO as solvent. The mixture was hydrolyzed, the ethylated compounds extracted with hexane and determinated by GLC-NPD on a BP-5 fused silica capillary column. Values obtained with the direct GLC analysis were reproducible and similar to those obtained after ethylation. Recovery of each herbicide was higher than 80% and the limit of detection was 0.01 ppm. These compounds were also analyzed by GLC-ITD. The sensitivity in the SIM mode was near 0.1 ng and the residues can be confirmed with this technique down to 0.01 ppm. © 1991 Springer-Verlag

Hexazinone and simazine dissipation in forestry field nurseries

8 pages, 4 tables, 6 figures, 30 references.Hexazinone and simazine field dissipation was studied in two different soils from Spain (Toledo and Burgos), devoted to forest nurseries for Pinus nigra. Laboratory experiments (adsorption–desorption isotherms, leaching experiment and degradation study) were carried out to determine possible mechanisms of dissipation. Higher adsorption was observed for hexazinone in Toledo (KfT=0.69) compare to in Burgos soil (KfB=0.20) probably due to the higher organic matter (OM) content of Toledo soil. No differences in adsorption were obtained for simazine in both soils (KfT=1.27; KfB=1.34). In every case, adsorption was higher for simazine than for hexazinone, in both soils. The total recovery of hexazinone in the leachates from handpacked soil columns was higher in Burgos (100%) than in Toledo (80%), because of the larger adsorption of hexazinone in this last soil. No differences in simazine leaching between both soils were found, although the total amount of pesticide recovered in leachates (40% in the two soils) was lower for simazine than for hexazinone. Finally, lower degradation was found in Burgos (t1/2=91 d) vs Toledo (t1/2=47 d), directly related with the high OM content of Toledo. No half-life was calculated for simazine in Toledo because no changes in herbicide soil content were observed during the period of time studied. In the case of Burgos, the half-life for simazine was 50 days. The field residues study showed larger persistence of simazine than hexazinone mainly due to the higher adsorption and lower mobility of simazine in the two soils. The lower persistence of hexazinone in Toledo soil than in Burgos soil is related to the larger rainfall occurred in this soil besides the higher degradation of this herbicide observed in Toledo soil. The much lower temperature in Burgos than in Toledo soil during winter contribute to the higher persistence of the two herbicides in Burgos soil.Ministry of Science and Technology and INIA FO96-016-C02-2Thanks are due to the Ministry of Science and Technology and INIA for financial help through the project FO96-016-C02-2.Peer reviewe

Detection of phytotoxic soil residues of hexazinone and simazine by a biological test using Lepidium sativum L. var. Cresson

Current plant bioassays included in the guidelines for testing pesticides do not include the measurement of reproduction endpoints. A bioassay, based on reduction of flowering of cress was developed to detect soil residues of hexazinone and simazine at levels of 0.02 and 0.10 ppm, respectively. The endpoint used in the described bioassay is the percentage of plant viability that implies that the tested plants have reached the flowering stage. It was found that sensitivity of cress is lower in soils containing higher organic matter

Residue determination of captan and folpet in vegetable samples by gas chromatography/negative chemical ionization-mass spectrometry

A gas chromatography/negative chemical ionization-mass spectrometry (GC/NCI-MS) method has been developed for the simultaneous determination of the fungicides captan and folpet in khaki (persimmon; flesh and peel) and cauliflower. Samples were extracted with acetone in the presence of 0.1 M zinc acetate solution in order to avoid degradation of fungicides and were purified using solid-phase extraction with divinylbenzene polymeric cartridges. Purified extracts were evaporated and dissolved in hexane prior to injection into the GC/NCI-MS system. Isotope-labeled captan and folpet were used as surrogate/internal standards, and quantification was performed using matrix-matched calibration. The method showed linear response in the concentration range tested (50-2500 ng/mL). The method was fully validated with untreated blank samples of khaki (flesh and peel) and cauliflower spiked at 0.05 and 0.5 mg/kg. Satisfactory recoveries between 82 and 106% and relative standard deviations lower than 11% in all cases (n = 5) were obtained. The limit of detection for both compounds were estimated to be 0.01 mg/kg. The developed method has been applied to treated and untreated samples collected from residue trials