Branko Šikoparija

Common ragweed: a threat to environmental health in Europe.

Common or short ragweed (Ambrosia artemisiifolia L.) is an annual herb belonging to the Asteraceae family that was described by Carl Linnaeus in the 18th century. It is a noxious invasive species that is an important weed in agriculture and a source of highly allergenic pollen. The importance placed on A. artemisiifolia is reflected by the number of international projects that have now been launched by the European Commission and the increasing number of publications being produced on this topic. This review paper examines existing knowledge about ragweed ecology, distribution and flowering phenology and the environmental health risk that this noxious plant poses in Europe. The paper also examines control measures used in the fight against it and state of the art methods for modelling atmospheric concentrations of this important aeroallergen. Common ragweed is an environmental health threat, not only in its native North America but also in many parts of the world where it has been introduced. In Europe, where the plant has now become naturalised and frequently forms part of the flora, the threat posed by ragweed has been identified and steps are being taken to reduce further geographical expansion and limit increases in population densities of the plant in order to protect the allergic population. This is particularly important when one considers possible range shifts, changes in flowering phenology and increases in the amount of pollen and allergenic potency that could be brought about by changes in climate.

The Onset, Course and Intensity of the Pollen Season

The onset, duration and intensity of the period when pollen is present in the air varies from year to year. Amongst other things, there is an effect upon the quality of life of allergy sufferers. The production and emission of pollens are governed by interacting environmental factors. Any change in these factors may affect the phenology and intensity of the season. Readiness to flower in a plant, and the amount of pollen produced, is the result of conditions during an often long period foregoing flowering. When a plant is ready to flower, temporary ambient circumstances e.g., irradiation and humidity, determine the timing of the actual pollen release. In order to understand variation between years and to be able to safely predict future situations, not least due to the ongoing climate change, it is necessary to know the determinants of all related processes and differences between and within species, here reviewed.

Monitoring, Modelling and Forecasting of the Pollen Season

The section about monitoring covers the development of phenological networks, remote sensing of the season cycle of the vegetation, the emergence of the science of aerobiology and, more specifically, aeropalynology, pollen sampling instruments, pollen counting techniques, applications of aeropalynology in agriculture and the European Pollen Information System. Three data sources are directly related with aeropalynology: phenological observations, pollen counts and remote sensing of the vegetation activity. The main future challenge is the assimilation of these data streams into numerical pollen forecast systems. Over the last decades consistent monitoring efforts of various national networks have created a wealth of pollen concentration time series. These constitute a nearly untouched treasure, which is still to be exploited to investigate questions concerning pollen emission, transport and deposition. New monitoring methods allow measuring the allergen content in pollen. Results from research on the allergen content in pollen are expected to increase the quality of the operational pollen forecasts.

Modelling the introduction and spread of non-native species: international trade and climate change drive ragweed invasion

Biological invasions are a major driver of global change, for which models can attribute causes, assess impacts and guide management. However, invasion models typically focus on spread from known introduction points or non-native distributions and ignore the transport processes by which species arrive. Here, we developed a simulation model to understand and describe plant invasion at a continental scale, integrating repeated transport through trade pathways, unintentional release events and the population dynamics and local anthropogenic dispersal that drive subsequent spread. We used the model to simulate the invasion of Europe by common ragweed (Ambrosia artemisiifolia), a globally invasive plant that causes serious harm as an aeroallergen and crop weed. Simulations starting in 1950 accurately reproduced ragweeds current distribution, including the presence of records in climatically unsuitable areas as a result of repeated introduction. Furthermore, the model outputs were strongly correlated with spatial and temporal patterns of ragweed pollen concentrations, which are fully independent of the calibration data. The model suggests that recent trends for warmer summers and increased volumes of international trade have accelerated the ragweed invasion. For the latter, long distance dispersal because of trade within the invaded continent is highlighted as a key invasion process, in addition to import from the native range. Biosecurity simulations, whereby transport through trade pathways is halted, showed that effective control is only achieved by early action targeting all relevant pathways. We conclude that invasion models would benefit from integrating introduction processes (transport and release) with spread dynamics, to better represent propagule pressure from native sources as well as mechanisms for long-distance dispersal within invaded continents. Ultimately, such integration may facilitate better prediction of spatial and temporal variation in invasion risk and provide useful guidance for management strategies to reduce the impacts of invasion.

Ragweed (Ambrosia) Pollen Source Inventory for Austria

UNLABELLED This study improves the spatial coverage of top-down Ambrosia pollen source inventories for Europe by expanding the methodology to Austria, a country that is challenging in terms of topography and the distribution of ragweed plants. The inventory combines annual ragweed pollen counts from 19 pollen-monitoring stations in Austria (2004-2013), 657 geographical observations of Ambrosia plants, a Digital Elevation Model (DEM), local knowledge of ragweed ecology and CORINE land cover information from the source area. The highest mean annual ragweed pollen concentrations were generally recorded in the East of Austria where the highest densities of possible growth habitats for Ambrosia were situated. Approximately 99% of all observations of Ambrosia populations were below 745m. The European infection level varies from 0.1% at Freistadt in Northern Austria to 12.8% at Rosalia in Eastern Austria. More top-down Ambrosia pollen source inventories are required for other parts of Europe. CAPSULE ABSTRACT A method for constructing top-down pollen source inventories for invasive ragweed plants in Austria, a country that is challenging in terms of topography and ragweed distribution.

Is the Recent Decrease in Airborne Ambrosia Pollen in the Milan Area Due to the Accidental Introduction of the Ragweed Leaf Beetle Ophraella Communa

This study aims to determine whether a significant decrease in airborne concentrations of Ambrosia pollen witnessed in the north-west of the Province of Milan in Northern Italy could be explained by environmental factors such as meteorology, or whether there is evidence to support the hypothesis that the decrease was related to the presence of large numbers of the oligophagous Ophraella communa leaf beetles that are used as a biological control agent against Ambrosia in other parts of the world. Airborne concentrations of Ambrosia, Cannabaceae and Urticaceae pollen data (2000–2013) were examined for trends over time and correlated with meteorological data. The amount of Ambrosia pollen recorded annually during the main flowering period of Ambrosia (August–September) was entered into linear regression models with meteorological data in order to determine whether the amount of airborne Ambrosia pollen recorded in 2013 was lower than would normally be expected based on the prevailing weather conditions. There were a number of significant correlations between concentrations of airborne Ambrosia, Cannabaceae and Urticaceae pollen, as well as between airborne pollen concentrations and daily and monthly meteorological data. The linear regression models greatly overestimated the amount of airborne Ambrosia pollen in 2013. The results of the regression analysis support the hypothesis that the observed decrease in airborne Ambrosia pollen may indeed be related to the presence of large numbers of O. communa in the Milan area, as the drastic decrease in airborne Ambrosia pollen in 2013 cannot be explained by meteorology alone.

Risk of exposure to airborne Ambrosia pollen from local and distant sources in Europe – an example from Denmark

BACKGROUND Ambrosia artemisiifolia L. is a noxious invasive alien species in Europe. It is an important aeroallergen and millions of people are exposed to its pollen. OBJECTIVE The main aim of this study is to show that atmospheric concentrations of Ambrosia pollen recorded in Denmark can be derived from local or more distant sources. METHODS This was achieved by using a combination of pollen measurements, air mass trajectory calculations using the HYPLIT model and mapping all known Ambrosia locations in Denmark and relating them to land cover types. RESULTS The annual pollen index recorded in Copenhagen during a 15-year period varied from a few pollen grains to more than 100. Since 2005, small quantities of Ambrosia pollen has been observed in the air every year. We have demonstrated, through a combination of Lagrangian back-trajectory calculations and atmospheric pollen measurements, that pollen arrived in Denmark via long-distance transport from centres of Ambrosia infection, such as the Pannonian Plain and Ukraine. Combining observations with results from a local scale dispersion model show that it is possible that Ambrosia pollen could be derived from local sources identified within Denmark. CONCLUSIONS The high allergenic capacity of Ambrosia pollen means that only small amounts of pollen are relevant for allergy sufferers, and just a few plants will be sufficient to produce enough pollen to affect pollen allergy sufferers within a short distance from the source. It is necessary to adopt control measures to restrict Ambrosia numbers. Recommendations for the removal of all Ambrosia plants can effectively reduce the amount of local pollen, as long as the population of Ambrosia plants is small.

A follow-up study examining airborne Ambrosia pollen in the Milan area in 2014 in relation to the accidental introduction of the ragweed leaf beetle Ophraella communa

The North American invasive alien Ambrosia artemisiifolia L. (common or short ragweed) is considered to be an important weed in agriculture and source of highly allergenic pollen (Smith et al. 2013; Essl et al. 2015 references therein) in many parts of the world, including Europe. The oligophagous leaf beetle Ophraella communa LeSage 1986 (Coleoptera: Chrysomelidae) preferably feeds from A. artemisiifolia, and is successfully used as a biological agent to control this weed in China (Zhou et al. 2014). It can prevent plants from producing seeds and pollen when it kills them before flowering. In 2013, this beetle was found to have accidentally established in Southern Switzerland and Northern Italy, with high incidence and densities in the Milan area Muller Scharer et al. 2014). The map showing the presence of the beetle has now been updated for 2014 (Fig. 1). We have previously shown, using linear regression models, that the exceptionally low amounts of airborne Ambrosia pollen observed in the Milan area in 2013 could not be explained by meteorology in that year. We therefore suggested that the decrease might be related to the presence of large numbers of O. communa (Bonini et al. 2015)

Mesoscale atmospheric transport of ragweed pollen allergens from infected to uninfected areas

Allergenic ragweed (Ambrosia spp.) pollen grains, after being released from anthers, can be dispersed by air masses far from their source. However, the action of air temperature, humidity and solar radiation on pollen grains in the atmosphere could impact on the ability of long distance transported (LDT) pollen to maintain allergenic potency. Here, we report that the major allergen of Ambrosia artemisiifolia pollen (Amb a 1) collected in ambient air during episodes of LDT still have immunoreactive properties. The amount of Amb a 1 found in LDT ragweed pollen grains was not constant and varied between episodes. In addition to allergens in pollen sized particles, we detected reactive Amb a 1 in subpollen sized respirable particles. These findings suggest that ragweed pollen grains have the potential to cause allergic reactions, not only in the heavily infested areas but, due to LDT episodes, also in the regions unaffected by ragweed populations.

ENVIRONMENTAL EFFECTS ON SUPEROXIDE DISMUTASE AND CATALASE ACTIVITY AND EXPRESSION IN HONEY BEE

Understanding the cellular stress response in honey bees will significantly contribute to their conservation. The aim of this study was to analyze the response of the antioxidative enzymes superoxide dismutase and catalase in honey bees related to the presence of toxic metals in different habitats. Three locations were selected: (i) Tunovo on the mountain Golija, as control area, without industry and large human impact, (ii) Belgrade as urban area, and (iii) Zajača, as mining and industrial zone. Our results showed that the concentrations of lead (Pb) in whole body of bees vary according to habitat, but there was very significant increase of Pb in bees from investigated industrial area. Bees from urban and industrial area had increased expression of both Sod1 and Cat genes, suggesting adaptation to increased oxidative stress. However, in spite increased gene expression, the enzyme activity of catalase was lower in bees from industrial area suggesting inhibitory effect of Pb on catalase.