Common ragweed (Ambrosia artemisiifolia L.) is one of the annual plants that were described recently as invasive weeds in Europe. This species is described as an invasive plant that produces seeds ...that are highly variable. Its production of variably sized seeds is regarded as promoting its spread in different environments. Experiments were carried out to determine the influence of the seed weight and temperature on germination and the influence of the seed weight and burial depth on seedling emergence. The seeds were divided into a number of classes of weight and the seed weight effect on germination was evaluated by Petri dish assays. In another experiment, the seeds were buried at different depths in a clay soil/sand mix to estimate the burial effect on germination and seedling emergence. The germination level of A. artemisiifolia was high overall, between 76.8% and 94.2%. The seed germination was modified by temperature but it was not influenced by the seed weight. The amounts of germination and seedling emergence were greater for the seeds on the soil surface and decreased with an increasing burial depth, from 2 to 8 cm. No germination or emergence was observed for the seeds that were buried at 10 and 12 cm. The lightest seeds were more sensitive to burial. A greater level of seedling emergence for those seeds that were placed near the soil surface could explain the success of this species in open habitats, where the probability of deeper burial is low. After high seed production, the management of A. artemisiifolia in fields could be partly achieved through soil tillage, burying seeds below 10 cm, and not carrying out deep soil tillage the following year.
L'utilisation d'un capteur de pollens, modèle Cour, a permis aux auteurs l'étude de la précocité des principaux critères du modèle prédictif de pollinisation de l’ambroisie à feuilles d’armoises à ...partir des données des comptes polliniques de Lyon-Bron de 1982 à 2001. Ce modèle prédictif de pollinisation a été défini en 1989 et mis en application pour une communication publique depuis 1994. Une avancée des dates des paramètres étudiés de pollinisation est mise en évidence : cette précocité est importante, puisqu’en 20 ans, elle enregistre une avancée moyenne de 6 à 16 jours (soit une moyenne de 11 jours) et des valeurs extrêmes de l’ordre du mois, selon le critère étudié. Les droites de tendance tracent une prévision pour l’année 2002. Le réchauffement climatique est discuté. Sur le plan allergologique, les fortes variations inter-annuelles observées, doivent être intégrées dans le traitement de la pollinose due à cette plante et confirment l’intérêt du modèle prédictif de pollinisation de l’ambroisie de l’AFEDA. Ces variations montrent la nécessité de poursuivre, chaque année, d’une part la mesure, d’autre part la diffusion publique en temps réel, des comptes polliniques dont la connaissance permet d’améliorer la qualité de soin des allergiques. Le tracé de la droite de tendance est un facteur supplémentaire d’amélioration de ces soins. Il devra être reconduit d’année en année.
We used data obtained in the Lyon-Bron region from 1982 to 2001 with the Cour pollen trap, a particularly sensitive measuring device, to study the main parameters that are used to forecast the onset of pollination of common ragweed. This predictive model had been defined in 1989 and the results have been published in the media since 1994. Analysis of the data showed that the onset of pollination was advancing over the past 20 years. The advance of the date of pollination is significant, registering an average of 11 days (range 6 to 16 days), with an advance of as much as a month in some years, depending on the criteria used. The regression line provides a forecast for 2002. We discuss the possibility that pollen counts taken over a long period might be used to measure climatic warming? From the point of view of the allergist, the wide year-to-year variations observed should be taken into account in the treatment of patients with ragweed allergy, confirming the potentially useful aspect of the predictive model produced by the AFEDA. These results indicate that there is every interest in continuing to determine pollen counts annually and to make the results public in real time, which could lead to an improvement in the care of the allergic patient. The regression line of the annual pollen counts is an additional factor to be considered, and it should be updated each year.
A study of the effects of crop rotation and weed management on weed seedbanks was conducted near Woodslee, Ontario, Canada. Ten different crop rotations involving corn, soybean, and cereals were ...maintained over a thirteen year period. Three levels of weed management (Untreated, cultivated, and herbicide) were established in each rotation. In the thirteenth year: weed seedling emergence was monitored in the field; soil samples from each treatment were taken in the spring and placed in a greenhouse for promotion of weed seed germination, in order to estimate the seedbank. Regression analysis was performed to determine the correlation between seedling emergence in the field plots with seedling emergence from soil samples taken from the field plots. Results of this study showed that (1) the continuous corn rotation had a larger weed seedbank than continuous soybean and continuous cereal rotations; (2) weed management practices (herbicides and cultivation) further reduce weed populations; and (3) greenhouse emergence studies can be used as predictors of future weed flushes in the field.
Na temelju ciljanih faunističkih istraživanja prikazane su 34 nove pojave ambrozije zlatice (Ophraella communa, LeSage) u deset županija kontinentalne Hrvatske. Od sredine srpnja do kraja rujna 2022. ...vizualno su pregledane 34 lokacije na kojima se ambrozija (Ambrosia artemisiifolia L.) redovito pojavljuje. Na svim lokacijama pregledanim u srpnju i kolovozu pronađeni su svi razvojni stadiji kukca, dok su na svim lokacijama pregledanim u rujnu pronađene samo odrasle jedinke. Na 12 lokacija oštećenje ambrozije uzrokovano ishranom ambrozijinom zlaticom procijenjena je na manje od 10%. Na 10 lokaliteta oštećenje uzrokovano ishranom se kretalo od 10 do 50%, a na sedam lokaliteta od 50 do 80%. U Hrvatskoj je, na pet praćenih lokaliteta u četiri županije, zabilježena prva masovna pojava ambrozijine zlatice i potpuno uništenje biljaka ambrozije. Visoka razina oštećenja lišća ukazuje na to da je vrsta već neko vrijeme prisutna na promatranom području. Ambrozijina zlatica se ubrzano širi na velikim površinama i sposobna je vrlo učinkovito suzbiti invazivnu biljnu vrstu ambrozije. Budući rad trebao bi biti usmjeren na praćenje širenja, uspostavljanja populacije i utjecaja ove vrste u Hrvatskoj te njezino uključivanje u biološke mjere suzbijanja ambrozije.
The aim of the paper is to present the preliminary results obtained through a composite data processing system using multiple correspondence analysis in order to perform data fusion and deduce rules ...of spatial organisation. After describing a case study on the cartography of Ambrosia artemisiifolia (common ragweed), currently investigated on the Urban Community of Montreal (Canada) territory, the authors present an overview of the methods implemented for the digitalisation and interpolation of data and discuss methodological problems raised in the course of the study. Finally, avenues for future research conclude the paper.
