1,2-Dehydro-pyrrolizidine alkaloids (PA) and their N-oxides (PANO) exhibit acute and chronic toxic effects on the liver and other organs and therefore are a hazard for animal and human health. In certain regions of Germany, an increasing spread of Senecio spp. (ragwort) on grassland and farmland areas has been observed during the last years leading to a PA/PANO-contamination of feed and food of animal and plant origin. This project was carried out to elucidate whether the process of grass pellet production applying hot air drying influences the content of PA and PANO. Samples of hay (n = 22) and grass pellets (n = 28) originated from naturally infested grassland (around 10% and 30% dominance of Senecio aquaticus) and from a trial plot with around 50% dominance. Grass pellets were prepared from grass originating from exactly the same plots as the hay samples. The samples were analysed by liquid chromatography-tandem mass spectrometry for PA/PANO typically produced by this weed. The results of the study revealed that PA/PANO levels (predominantly sum of senecionine, seneciphylline, erucifoline and their N-oxides) in hay ranged between 2.1 and 12.6 mg kg dry matter in samples with 10% and 30% dominance of S. aquaticus, respectively. Samples from the trial plot (50% dominance) had levels of up to 52.9 mg kg. Notably, the hot air drying process during the production of grass pellets did not lead to a reduction of PA/PANO levels. Instead, the levels in grass pellets with 10% and 30% S. aquaticus ranged from 3.1 to 55.1 mg kg. Grass pellets from the trial plot contained up to 96.8 mg kg. In conclusion, hot air drying and grass pellet production did not affect PA/PANO contents in plant material and therefore, heat-dried products cannot be regarded as safe in view of the toxic potential of 1,2-dehydro-pyrrolizidine alkaloids.
ZusammenfassungNach einer zwanzigjährigen schadensschwellenorientierten Herbizidbehandlung mit einer verringerten Behandlungsintensität erhöhte sich der Unkrautbesatz gegenüber einer regelmäßig optimalen Behandlung tendenziell. Dieser erhöhte Unkrautbesatz wurde in weiteren acht Versuchsjahren mit gezielt ausgewählten Herbizidkombinationen, Aufwandmengen und Behandlungsfolgen bearbeitet. Erst nach sechs Jahren stellte sich wieder ein gleichwertiger Unkrautbesatz ein. Die Unkrautflora des Dauerversuchsstandorts reagierte relativ träge auf eine moderat reduzierte Behandlungsintensität als auch auf einen gezielten Herbizideinsatz zur Verringerung der Besatzdichte. Auf die Produktionspraxis übertragen kann anhand dieser Daten von einer erst mittelfristigen Reaktion der standortspezifischen Unkrautflora auf eine reduzierte Behandlungsintensität ausgegangen werden. Allerdings würde auch die Rückregulierung von erhöhten Unkrautbesatzdichten nur mit einem über einen Zeitraum von ≥ 5 Jahren erhöhtem Herbizideinsatz möglich sein. Hiernach scheinen pauschale Vorgaben hinsichtlich der standortspezifischen Herbizidbehandlungsintensität nicht zielführend in Bezug auf die nachhaltige Förderung des Standortertragspotentials zu stehen.Schlüsselwörter Unkraut · Unkrautspektrum · Unkrautbesatz · Fruchtfolge · Dauerversuch · Herbizid · Behandlungsintensität · Behandlungsindex Adaptation of weed spectrum to a different intensity of herbicide treatment Abstract After 20 years of weed control according to an threshold model with reduced herbicide doses the weed K. Gehring (u) · S. Thyssen · T. Festner Bayerische Landesanstalt für Landwirtschaft,
In the northern forelands of the Alps, farmers report an increase of Jacobaea aquatica in production grasslands. Due to its toxicity, the species affects grassland productivity and makes costly control measures necessary. We are investigating the extent to which management practices or climatic factors are responsible for the increase of the species, and how the situation will change as a result of climate change. We tested for effects of management intensity, fertilization, agri-environmental measures and injuries to soil and sward and modeled the species' risk of occurrence under rcp4.5 and rcp8.5 scenarios. Main determinants of the occurrence of the species are soil type and summer rainfall. A high risk is associated with wet soils and more than 400 mm rain between June and August. An influence of the management related factors could not be detected. Under the climate scenarios, the overall occurrence risk decreases, and shifts to the wetter alpine regions. The reported increase is rather a shift in the occurrence of the species due to the altered precipitation situation. Under future climatic conditions, the species will decline and retreat to higher regions in the Alps. This will decrease the risk of forage contamination in lower production grassland.
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