Invasive alien species in Switzerland - Schweizer ...

4 > Insects – Insecta 81
as ornamentals. However, other southern European species may have entered Switzerland
independently. In particular, four true bugs, the lygaeids Arocatus longiceps,
Orsillus depressus and Oxycarenus lavaterae, and the mirid Deraeocoris flavilinea are
clearly expanding their range from southern to Central Europe (e.g. Adlbauer and
Rabitsch, 2000; Rabitsch, 2002). Whether the spread is purely natural or not remains
unclear.
Most of the known exotic Hemiptera included in the list are recognized as pests, feeding
on crops, ornamentals and forest trees in Switzerland. It is likely that many other
exotic Hemiptera remain undetected because they feed on non-commercial plants.
Among aphids, one of the best-known cases of exotic pests in Europe is the grape
phylloxera, Viteus vitifoliae which invaded Europe from North America in the 19 th
century, causing serious damage to vineyards and endangering the European wine
industry. The problem was solved by grafting European cultivars on less susceptible
American rootstocks; however, the level of damage has increased again in recent years,
including in Switzerland. Other aphid species, such as Myzus persicae, Macrosiphum
euphorbiae and Aphis gossypii, attack a wide range of vegetable crops, both indoors
and outdoors. They are also vectors of serious viral diseases. The Russian wheat aphid,
Diuraphis noxia (Kurdjumov), a serious pest of cereals, has not yet been reported from
Switzerland, but has already invaded France, Italy and Austria (CABI, 2001; Lethmayer
and Rabitsch, 2002). Orchard trees in Switzerland, in particular apple trees, can
be severely damaged by the North American woolly aphid Eriosoma lanigerum and the
Asian Aphis spiraecola. In forestry, the most serious exotic aphid is certainly the
woolly aphid Dreyfusia nordmannianae, a pest of firs (Abies) of Caucasian origin, but
other species such as Gilletteella cooleyi on Pseudotsuga and Elatobium abietinum on
Picea, both from North America, may cause some concern to foresters.
Only two exotic whitefly species (Aleyrodidae) are known to occur in Switzerland,
Bemisia tabaci and Trialeurodes vaporarium, but these are among the main pests of
vegetables in greenhouses. Control is achieved using aphelinid parasitoids in the
genera Encarsia and Eretmocerus.
A number of exotic scale insects are also known as pests in Switzerland, particularly on
orchard and ornamental trees. The San José scale, Quadraspidiotus perniciosus, is an
Asian species that has invaded nearly all continents, including Europe, where it is still
expanding its range. It is already distributed in most parts of Switzerland, where it
causes serious damage to orchards, particularly apple, peach and plum (see Fact Sheet).
Another congeneric species, Q. pyri, also attacks fruit trees, but its origin remains
uncertain, and it may be indigenous. In recent years, serious damage by scale insects
has been observed on urban trees. The diaspidid Pseudaulacaspis pentagona, an insect
of Asian origin and known to be polyphagous attacking mainly mulberry and peach
trees, has caused severe damage to ornamental trees such as Sophora, Aesculus and
Catalpa in Swiss cities (Mani et al., 1997). Similarly, the coccid Pulvinaria regalis
(see Fact Sheet) is a polyphagous exotic species of uncertain origin that has recently
caused heavy damage to Tilia and Aesculus in Zürich (Hippe and Frey, 1999).