Invasion of Popillia japonica in urban forest habitats of Northern Italy

The Japanese beetle Popillia japonica Newman (Coleoptera: Scarabaeidae) is a highly polyphagous pest originated from north-eastern Asia and introduced and established in Northern Italy, between Lombardy and Piedmont regions, since 2014. The infested area increased over time at a constant rate, and it covers now more than 15,000 km2. The reason for this rapid expansion is linked to various drivers, among which the high suitability of the region. The beetle requires broadleaved tree species for maturation feeding and roots of various plants for larval development. The proximity of those resources does maximise the performance and facilitate the spread. Indeed, urban forested areas and irrigated hay meadows are widely represented in the infested area. They represent key habitats for the development and spread of the species, providing high-quality nutritional resources for both larvae and adults. The high suitability of the territory for the beetle has hindered the success of all control actions officially implemented by the plant health authorities, and P. japonica in Italy is now considered not eradicable. Therefore, a systems approach strategy aimed at controlling the pest is required for preventing the establishment of the species in new areas and for reducing pest population pressure. An outline of the systems approach developed for P. japonica is presented.