Spread of common ragweed (Ambrosia artemisiifolia L.) on the Žitný Ostrov (Slovakia) and Szigetköz (Hungary) in 2015

Common ragweed, Ambrosia artemisiifolia (Asteraceae) is an annual, monoecious herb, native to North America. All aspects of its biology and ecology were described in detail by Essl et al, (2015). The species has been introduced and naturalized in many countries worldwide [35]. Ragweed is described as one of the most important invasive weed in Europe [19], [33] it is still expanding and modelling predict even the potential spread northward and uphill [11], [14]. The most important areas with ragweed occurrence within Europe are Pannonian Plain in Central Europe (especially Hungary and some parts of Slovakia, Serbia, Croatia, Slovenia, and Romania), Rhone-Alpes region in France, Ukraine, southern European Russia and Po River valley in Italy [9], [36], [38], [40], [43]. The cardinal negative effect of any invasion to native species is strong competition [32] and threat to biodiversity [42]. Ragweed acts as a strong competitor especially in the arable land [1] and colonies and dominates at disturbed habitats, where is no competition from native plants [47]. Common ragweed is a dominant weed in arable fields and in heavily infested regions of Europe causes substantial crop-yield losses. In Hungary, 700000 ha of farmland was heavily infested (extent of infestation 10 %<) in 2003 [4]. The most frequently infested crops within Central Europe are spring-sown crops like sunflower, corn, soybean and stubble fields [2], [21], [22], [51]. For example, A. artemisiifolia decreased grain yield of corn by 19.5% and above ground corn biomass by 18.5% at density of 5 ragweed plants per m2 in Slovakia [53], sunflower yield in Hungary was decreased by 27% at density of two ragweed plants per m2 [24] up to 33% at the density of 10 ragweed plants per m2 [17]. The highly allergenic pollen of A. artemisiifolia means also considerable threat to public health, especially human respiratory system [39], [55]. The principal regions with Ambrosia occurrence in Slovakia are Žitný ostrov at the southwestern part of the country and south of Eastern Slovakia [56]. Common ragweed was first recorded within the scope of Europe in France in the 18th century [26] , while in Slovakia as late as 1949 [50]. This plant has no special demands for soil, however prefers moderately basic sandy and clays soils [45]. Ambrosia grows in dry fields and pastures, vineyards, waste grounds, along rivers, canals, bird feeding places, roads and railways. Heavy infestation occurs around agricultural and industrial objects and forms dense populations especially in agricultural land within lowlands [19], [20], [22], [25], [28], [29], [48],. On the other hand, while ragweed grows abundantly in certain habitats, other habitats are hardly populated [7]. In general many segetal plants in Central Europe are threatened by extinction [57] and increasing spread of common ragweed pose the threat e.g. to stubble-field weed community [23]. Many studies pointed out changes in segetal vegetation, disappearance of some species [12], [27], [44] and inappropriateness of habitats for natural enemies, birds and mammals [10]. 

 The present study offers insight into the pattern of A. artemisiifolia occurrence within the farming landscape of Žitný ostrov (Slovakia) and Szigetköz (Hungary). Geospatial analysis was used to create 2D map in ArcGIS environment, which helps to understand the abundance and distribution of ragweed in these territories. We wanted to know particularly what is the spatial spread of A. artemisiifolia throughout the most intensive managed agricultural lands and which are the most important accompanying plant species of ragweed in the field.