Starting an invasion: A five-year monitoring program of Halyomorpha halys (Hemiptera: Pentatomidae) in South Tyrol (Northern Italy)

Abstract

Monitoring is a fundamental step when non-native species are invading new areas. The brown marmorated stink bug Halyomorpha halys (Stål) has by now been introduced into several countries worldwide. Its highly polyphagous behavior, paired with a relatively high reproduction rate under favorable conditions, makes it an important pest of several agricultural crops. In South Tyrol (Northern Italy), one of the largest contiguous apple-growing regions in Europe, first adults had been reported in March 2016. Active monitoring techniques combined by a citizen science approach made it possible to follow up the spread and settlement of stable populations of H. halys in South Tyrol. Since its first detection, H. halys showed a rapid expansion of colonized area and an increase in population densities from year to year. Established populations coincide mostly with the main apple growing area, namely the Etsch Valley from Meran to Salurn, mainly occupying lower altitudes between 200 and 500 m a.s.l. In apple orchards, H. halys showed generally a continuous presence throughout the growing season from April to October, with population peaks in the late season. On the other hand, populations dynamics and densities of adults and nymphs differ between years and surveyed sites. The application of pheromone-baited traps is a good tool for an area-wide monitoring approach in order to get information on its spreading and to draw a general picture of the population dynamics at a larger scale. On the other hand, an area-wide approach has to be interpreted cautiously, as real population densities might be underestimated and do not depict the real situation for singular orchards.

Keywords

• brown marmorated stink bug
• pheromone traps
• citizen science
• apple orchard
• seasonality