Browsing by Subject "Distribution"

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Bromus-Arten in Winterweizen: Verbreitung, Bedeutung und Populationsdynamik
(2005) Moray, Ralph; Hurle, Karl
The increase of reduced tillage in agriculture and winter cereal dominated crop rotations has lead to a rise of annual and perennial grass weeds in the last decades. One of these are Bromus species that occur worldwide in cereal growing areas. In Germany they also attract more and more interest because of their increasing distribution. Therefore an inves-tigation was conducted to assess the current situation of Bromus species in Germany, competition, population biology and control. Additionally, control strategies were designed on the basis of analyses of population-dynamical parameters. A survey carried out in Germany, showed that Bromus sterilis and B. secalinus were found to be the dominant species. The problems that were predominantly mentioned were yield loss and difficulties at harvest which mostly appear in winter wheat. Their occurrence is closely connected with reduced tillage, early seeding and winter cereal dominated crop rotations whereas Bromus densities can be reduced effectively with a mouldboard plough or the increase of spring crops in crop rotation. In dicot. crops the chemical control was regarded as very good, whereas in cereals between good to sufficient. All of the survey participants expected a further distribution of Bromus species on arable land. Field trials were conducted on three locations over a period of three years to investigate the competition of B. sterilis, B. secalinus, B. tectorum and B. japonicus in winter wheat. Weed density and seeding date of winter wheat were considered for the species competition studies. The trials showed that distinct yield losses could be recorded in winter wheat depending on the different Bromus species. Thresholds where calculated based on the relationship between weed density and yield loss. The thresholds for the Bromus species in winter wheat were below the values given in literature for other grass weeds in winter cereals. This highlights the strong competitiveness of the species. Additionally the results showed that with late seeding the weed density decreases distinctively and thereby the yield loss can be reduced by half. Greenhouse trials on the efficiency of the three in Germany registered herbicides for the control of Bromus species showed, that a sufficient control of B. sterilis and B. secalinus could not always be achieved with the recommended dose. The simulation of the population dynamics showed clearly that with reduced tillage and direct seeding in a winter wheat monoculture without control measures a very fast increase of densities within two growing seasons up to a density-dependent level where high yield losses can be expected. In contrast mouldboard ploughing can control the species to 100 % as a depth of seeds of 10 cm already reduces emergence by half and seeds in the trials showed to have longevity in soil of no longer that 12 months. Moreover, it was demonstrated that the soil cultivation has a higher influence on the development of the weed population than the different seeding dates of winter wheat. The simulation under the influ-ence of herbicide application suggested, that it is possible to practice a winter cereal dominated crop rotation without yield losses. From the results of the investigations it can be concluded that Bromus as a problem in win-ter cereal dominated crop rotation in our latitudes will increase. In fact the control with available herbicides is not always sufficient, but for economical reasons integrated control strategies can not always be considered although quite a good control is given. Therefore one can presume that in future the control of Bromus in winter cereals still will be based on the use of herbicides and that these weed species will be as common in win-ter cereals as it became Alopecurus myosuroides and Apera spica-venti.
Echinococcus multilocularis and other zoonotic helminths in red foxes (Vulpes vulpes) from a southern German hotspot for human alveolar echinococcosis
(2023) Schneider, Carina; Kratzer, Wolfgang; Binzberger, Andreas; Schlingeloff, Patrycja; Baumann, Sven; Romig, Thomas; Schmidberger, Julian
Background: We describe the spatial distribution of Echinococcus multilocularis in its main definitive host, the red fox, and the distribution of human cases of alveolar echinococcosis (AE) within a highly endemic focus in southern Germany (13.7–19.9/100,000 in 1992–2018). Human cases were unequally distributed within the endemicity focus. The purpose of the study was to test whether this is reflected in the small-scale distribution of E. multilocularis in foxes. Methods: Three areas with contrasting numbers of human cases were selected within the counties of Ravensburg and Alb-Donau, Baden-Württemberg, Germany. From 2018 to 2020, a total of 240 fox carcasses were obtained from traditional hunters in these areas. Carcasses were necropsied and examined for the presence of intestinal helminths. The statistical analysis was performed with SAS version 9.4, and the geo-mapping with QGIS version 3.16.0 Hannover. Results: The prevalence of E. multilocularis in foxes was 44/106 (41.5%) in area I (commune Leutkirch and environs), 30/59 (50.8%) in area II (commune Isny and environs), and 31/75 (41.3%) in area III (commune Ehingen and environs). From 1992 to 2018, a total of nine human cases of alveolar echinococcosis were recorded in area I, five cases were recorded in study area III, and no cases were recorded in area II. No statistically significant differences between the areas were observed ( P > 0.05) for intestinal infections with E. multilocularis , and no apparent spatial correlation with the small-scale distribution of human cases was found. Concerning other zoonotic helminths, Toxocara spp. were equally common, with prevalence of 38.7%, 47.4% and 48.0%, respectively, while the frequency of Alaria alata varied among the study areas (0.0–9.4%), probably reflecting the specific habitat requirements for the establishment of its complex life cycle. Conclusions: Echinococcus multilocularis is highly prevalent in foxes in all the studied areas. The varying number of human AE cases within these areas should therefore be caused by factors other than the intensity of parasite transmission in foxes.