Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Stowaways in horticultural plants imported from the Netherlands, Germany and Denmark.

Abstract

A steadily increasing import of horticultural plants to Norway for outdoor use facilitates the entry of organisms as stowaways on these plant commodities. Samples were taken from consignments of newly imported horticultural plants, mainly Thuja sp. and Taxus sp., from the Netherlands, Germany and Denmark. Three sampling methods were used: shaking the plants, sampling soil and debris from the bottom of the container, and visual inspections of the plants. Insects and spiders were prioritized in the collection process, but also species of Diplopoda, Isopoda, Gastropoda and Oligochaeta were represented in the material collected. The sampling resulted in 157 identified species and 1194 specimens. The three methods used resulted in 85, 93 and 5 species, respectively. 16 of the species found (14 insects, one spider and one diplopode) were at the time of discovery new to the Norwegian fauna, including the invasive alien ladybird Harmonia axyridis Pallas, 1773. Their biology, more recent observations and potential for establishment in Norway are discussed. At least 10 of the species are likely to establish in the country. The result of our investigations reveals that the WTO-SPS-Agreement and subsequent control measures are neither sufficient to protect an area against non-quarantine species nor to protect biodiversity.