DOI: 10.15468/gk6p48
title: Monitoring populations of Popillia japonica (Newman, 1838) over 16 years in the Azorean Islands

description: The Japanese beetle Popillia japonica was introduced on Terceira Island (Azores) early in the 1970s. Mild temperatures, high relative humidity, and heavy rain created the perfect conditions for the beetle's establishment and rapid spread. Despite initial control efforts, the beetle quickly spread to the island's interior agricultural regions and threatened the local plants and horticultural lands.
Since 1974, adult populations have been monitored in Terceira Island using pheromone and floral lure traps distributed across the island. The data revealed a distribution pattern across three circular zones with decreasing population densities and a movement of the infestation's central core to the island's interior to more conducive zones for the beetle's development. In 1989, 16 years after the first insects were discovered on the island, the pest had taken over all the available space. 
A contingency plan was drawn up to establish protective measures to prevent the spread of the Popillia japonica to Madeira and Portugal mainland in 1985 (Decreto Legislativo Regional 11/85/A, de 23 de Agosto). Later, it was actualized to comply with legislation of the European Union (EU), paying particular attention to categorizing this insect as a priority pest.
Although these preventive measures were applied, the pest spread to other islands over the years; currently, eight of the nine islands of the Archipelago are infested. Although preventive measures have been applied, the pest has spread to other islands over the years, and currently, eight of the nine islands of the Archipelago are infested. In 1996, the Japanese beetle was detected in Faial; in 2003, on the island of São Miguel; in 2006, in the island of Pico; in 2007, on Flores and São Jorge islands; in 2013, in Corvo; and 2017, in Graciosa. Only Santa Maria has not recorded the pest's presence.
The Japanese beetle completes its life cycle in a year, with individuals starting to emerge from the ground at the end of May and reaching their peak densities in early August. The last beetles were seen as late as the end of October. The first and second larval instars typically have a brief lifespan, and by early October, most of the population has reached the third instar. The third instar grubs stop feeding and pupate at the beginning of May. The pupal stage lasts less than a month, and no pupae were seen after late July. Adults eat the foliage, floral parts, and occasionally, the fruits of various agricultural plants and ornamentals. At the same time, the grubs live off the roots of the pastures that make up most of the island. It is important to clarify that the adult beetle pest can damage around 414 host plants belonging to 94 families, which may cause elevated crop damage, which makes this a priority pest to maintain under control. 
The data presented here is related to the Popillia japonica captured in the Azores from 2008 to 2023, which resulted from the work of the operational services on each island of the Secretaria Regional da Agricultura e Alimentação. It is a compilation of the officials’ records from the local authorities who contributed to this data from their fieldwork monitoring of Popillia japonica during these 16 years