The Euwallacea fornicatus species complex (Coleoptera: Curculionidae); emerging economic pests of tea in Taiwan

Abstract

The Euwallacea fornicatus species complex is native to Asia but has invaded many countries globally. This complex includes four cryptic species that infest a wide range of economic crops, including tea. One of them is Euwallacea perbrevis Schedl, which has been a major pest of tea in Sri Lanka and India for over a century. The species complex was first recorded infesting tea in Taiwan over 80 years ago but the specific identity of that first record is unknown. Furthermore, although tea is an important industry in Taiwan, this pest has attracted limited attention. Hence, we surveyed tea gardens across the island, determining infestation rates, and identifying the Euwallacea species present. We also used sticky traps to monitor the annual flight dynamics of the beetles and of a parasitoid natural enemy, an undescribed species of Eucosmophorus. Levels of infestation varied even between neighboring gardens. Highly infested tea gardens were located mainly in central Taiwan and some in eastern Taiwan. The peak flight activity of the species complex occurred between October and March, when the parasitoid was also abundant. Molecular identification of the trapped beetles identified them as E. fornicatus sensu stricto Eichhoff and E. kuroshio Gomez & Hulcr, but E. perbrevis was not detected. In contrast to the situation in Sri Lanka, where E. perbrevis attacks the highly visible terminal branches of the tea plant, in Taiwan, E. fornicatus s. s. and E. kuroshio predominantly attacked the main bole and underground parts. We propose that the ‘hidden’ nature of this attack, and the similarities of the symptoms to a common fungal disease of tea, may have led to an underestimation of the impact of the species complex on tea, not only in Taiwan but also in other tea growing countries.