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 (MüllerSchärer 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). European COST Action FA1203 (SMARTER, http://ragweed.eu) ‘‘Task Force Ophraella’’ is continuing to monitor the dynamics of O. communa and A. artemisiifolia in Northern Italy. Atmospheric concentrations ofAmbrosia pollen are also routinelymonitored in the Milan region by sites belonging to the Italian Monitoring Network in Aerobiology (R.I.M.A. ) of the Italian Aerobiology Association (A.I.A.) using volumetric spore traps of the Hirst design (Hirst 1952) and following the standard methods of A.I.A.-R.I.M.A. (2009).Ambrosia pollen data recorded at Legnanowere used for the analysis, as this is the closest pollen-monitoring station to Malpensa airport where the meteorological data were collected (Fig. 1). M. Bonini (&) G. Cislaghi P. Colombo C. Testoni Department of Medical Prevention, Public Health, Local Health Authority of Milan 1, Parabiago, MI, Italy e-mail: [email protected]