Description
ORIGIN AND SPREAD. Popillia japonica is native to Japan and eastern Russia. In the early 20th century, it was accidentally introduced into North America (United States and Canada) and in the 1970s on the island of Terceira in the Azores archipelago (Portugal). In the summer of 2014, P. japonica was reported for the first time in continental Europe and in particular in Italy between Piedmont and Lombardy in a large area of the Ticino Park. Since 2017, the insect has also been present in Switzerland.
HOST PLANTS. Popillia japonica in the adult stage can feed on more than 300 species of herbaceous, shrub and tree plants. The most important ones present in the region are: Vitis sp., Corylus sp., Rubus sp., Prunus sp., Malus sp., Pyrus sp., Morus sp., Actinidia sp., Zea mays, Glycine max, Rosa sp., Tilia sp., Betula sp., Crataegus sp., Hibiscus sp., Wisteria sp, Parthenocissus sp., Oenothera sp., Reynoutria japonica, Urtica sp., Convolvulus sp., Rumex spp., Hypericum perforatum, Artemisia sp., Salix sp., Alnus sp., Ulmus sp., Carpinus sp., Lythrum salicaria.
BIOLOGY. Popillia japonica is a scarab beetle that only performs one generation per year in the latitudes affected by the infestation. The literature shows that adults emerge from the ground from June onwards with the greatest number of insects in flight in mid-July. The flight of the adults is also conditioned by weather conditions, preferring sunny days with little wind and temperatures between 21°C and 35°C.
As soon as they emerge from the ground, the adults move to host plants for feeding and mating, preferring sunny exposures. Males appear a few days before females. The females lay eggs in small groups and then re-emerge for a new feeding phase before laying more eggs and proceed in this manner for their entire life span (approx. 30-45 days), laying a total of 40-60 eggs each.
Laying takes place in clusters of eggs inside small tunnels 5-10 cm deep, usually in wet meadows with grasses and only occasionally in other crops such as maize and soya.
During the winter months the population, mainly composed of III-aged larvae, stays in the soil at a depth of between 10 and 25 cm. In the spring the larvae move back to the more superficial layers of the soil where they resume their trophic activity at the expense of plant roots. In late spring, once they have completed their development and reached a length of around 32 mm, the third instar larvae pupate in earthy cells, from which the adults will flicker in early summer.
adults.
Description of the adults. The body of the adult individual is oval in shape and ranges in size from 8 to 11 mm in length and 5 to 7 mm in width. The colour is typically metallic green with copper-coloured elytra. The female is generally larger than the male. In both sexes, there are five tufts of white hairs on each side of the abdomen and two further tufts in the tergal part of the last abdominal segment, which makes it easy to distinguish it from other species of scarab beetles.
Description of larvae. Larval development takes place through 3 stages from about 1.5 mm in length, as soon as it hatches from the egg, to 25-32 mm when it reaches maturity. The body is yellowish in colour with the head and hind end darker. At rest it is characterised by the typical 'C' shape common in scarabaeids, from which it can be distinguished by two rows of V-shaped bristles on the last abdominal segment. Microscopic observation is required for recognition.
DIFFUSION ROUTES. Taking into account the biology, settlement potential and adaptability of the insect, it is considered that the risk of spread may affect a large part of the regional territory and have a negative impact on various areas, including the agricultural sector, the nursery sector, as well as on urban greenery, natural areas and regional forests.
REFERENCE LEGISLATION. Regulation (EU) 2016/ 2031; Implementing Regulation (EU) 2019/2072; Legislative Decree no. 19/2021; Commission Implementing Regulation (EU) 2023/1584 of 1 August 2023 on measures to prevent the establishment and spread of Popillia japonica Newman and measures for the eradication and containment of the harmful organism in question within certain demarcated areas in the territory of the Union; Order no. 9 of 20 January 2025 'Definition of areas free from the harmful organism Popillia japonica in the territory of the Italian Republic'; Ministerial Decree of 3 April 2024 'Adoption of the National Emergency Plan for Popillia japonica'; Order No. 5 of 28 September 2023 'Order of the National Plant Health Service aimed at the adoption of emergency phytosanitary measures to combat Popillia japonica Newman in Friuli-Venezia Giulia'.