First detection of the Japanese Beetle on Azores (Terceira Island)

The Japanese beetle, Popillia japonica Newman, was introduced on Terceira Island (Azores) early in the 1970s. The combination of mild temperatures, high relative humidity, and a lot of rain created the perfect conditions for the establishment and rapid spread of the beetle, which, despite initial control efforts, quickly spread to the island's interior agricultural regions and posed a threat to the local plants and horticultural lands.

Since 1974 adult populations have been monitored using pheromone and floral lure traps distributed across the entire 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, 15 years after the discovery of the first insects on the island, the pest had taken over all the available space. Currently, eight of the nine islands of the Archipelago are infested.

A contingency plan was drawn up with a view to establishing 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 the legislation of the European Union (EU), paying particular attention to the categorization of this insect as a priority pest.

P. japonica completes its life cycle on Terceira Island in a single year, with individuals starting to emerge from the ground at the end of May and reaching their peak densities in early August. With the last beetles being 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 begin pupating at the beginning of May. The pupal stage lasts for less than a month, and after late July, no pupae were seen. Adults eat the foliage, floral parts, and occasionally the fruits of various agricultural plants and ornamentals, while the grubs live off the roots of the pastures that make up most of the island. Eighteen local plant species in 8 families (Fagaceae, Platanaceae, Poaceae, Polypodiaceae, Rosaceae, Salicaceae, Ulmaceae, and Vitaceae) may suffer extensive damage from adult beetles.

References:
Martins, A. & N. Simões. 1985. Population Dynamics of the Japanese beetle (Coleoptera, Scarabaeidae) in Terceira Island – Azores. Arquipélago, Sér. C. N. 6, 57-62.
Simões, N. & A. Martins. 1985. Life Cycle of Popillia japonica Newman (Coleoptera, Scarabaeidae) in Terceira Island – Azores. Arquipélago, Sér. C. N. 6: 173-179.
Martins, A., Paiva, M. R., & Simões, N. (1988). Japanese Beetle: Monitoring in the Azores with Semiochemicals. Ecological Bulletins, 39, 101–103.
Martins, A., (1996). The Japanese beetle on Terceira Island (Açores) and the influence of soil physical factors on the efficacy of the fungus Metarhizium anisopliae (Metsch.) sorokin on the larval control of the insect. PhD thesis, University of Azores.