Invasive alien species in Switzerland - Schweizer ...

An inventory of alien species and their threat to biodiversity and economy in Switzerland FOEN 2006 72
vilinea). Some species undoubtedly migrated unaided from southern Europe to
Switzerland, possibly because of global warming. This is, for example, the case for
the dragonflies Sympetrum meridionale (Selys) and Crocothemis erythraea (Brullé).
Likewise, many Lepidoptera species (e.g. Helicoverpa armigera (Hübner) and
Mythimna unipuncta (Haworth), which used to be observed only occasionally in
summer in southern Switzerland, are now overwintering in the country more frequently.
Eastern European insect species are also increasingly observed in Switzerland.
For most of them, it is not clear whether their introduction into Switzerland
was natural or by human-mediated transport, and whether they are firmly established
or not. In general, species whose establishment in Switzerland seems to be the result
of a natural process were not included in our list. However, this phenomenon would
merit further studies.
> High numbers of tropical or subtropical insects are found in Switzerland in houses,
greenhouses and other confined environments. Many of them are important pests of
greenhouse crops (e.g. several thrips and whiteflies) or stored products (e.g. various
beetle and moth species). However, it is not always easy to determine whether these
insects are firmly established, or regularly introduced from abroad with new plant
material. Furthermore, some species that were thought to be confined to greenhouses
are now found outdoors in natural environments. Examples include, among others,
the scale insects Icerya purchasi, Coccus hesperidum and Dynaspidiotus britannicus
(Kozar et al., 1994).
> Today, many insects, particularly those feeding on stored products and crops and
occurring as ectoparasites of vertebrates are considered to be of cosmopolitan distribution
and, therefore, it is often difficult to assess their exotic status and some will
finally be concluded to be cryptogenic species. Only insects that are suspected to be
exotic, for any reason (e.g. because they feed only on an exotic plant, or because the
genus is considered exotic) are included in the list.
Invasive alien insects are serious threats to agriculture, economies, the environment
and human and animal health worldwide. In some regions, such as North America,
South Africa and many oceanic islands, exotic insect pests are considered to be as
important as native pests, if not more so. Traditionally, problems have been less severe
in Central Europe. Only a few exotic insects are known to cause serious damage in
Switzerland, usually as stored product pests or on agricultural crops. However, in
recent years several pests of economic importance have invaded Europe, stimulating
more interest in the issue of exotic insects. For example, the western corn rootworm,
Diabrotica virgifera ssp. virgifera is seriously threatening European maize production,
and the horse chestnut leaf miner, Cameraria ohridella, is causing much public concern
because of its spectacular damage to urban trees in Central Europe.
Worldwide, environmental impacts have been studied less for alien insects than for
other groups of invasive organisms such as plants or mammals. However, many insects
are known to cause serious environmental damage in invaded habitats. Here again,
most of these cases are from outside Europe. For example, the hemlock woolly adelgid,
Adelges tsugae Annand, is threatening unique forest ecosystems in North America
(Jenkins et al., 1999); the scale insect Orthezia insignis Browne was in the process of
pushing the endemic gumwood tree Commidendrum robustum DC. in Saint Helena to