Evaluación al sistema de inventario implementado para el control de café orgánico en el

A huge variety of alien species have been introduced over the years into the Maltese Islands. The ways in which these species have gained access is equally diverse and are summarised in Table 3.1.7.

Table 3.1.7

The modes of introduction of alien species into the Maltese Islands that are known or are suspected to have operated, with examples to illustrate the variety of species that have gained access.

Mode of introduction Examples

Deliberate introduction for agriculture and aquaculture

In the mid-1970s spat of the oysters Ostrea edulis and Crassostrea gigas was imported from Anglesey, Wales. Crassostrea gigas is still occasionally met with in the wild along the Maltese coast

Deliberate importation for commercial purposes:

?? Ornamental plants

?? The aquarium trade

Castor oil tree Ricinus communis, is an important escaped ornamental in the Maltese Islands Tree House-Leek, Aeonium arboreum, and Brazilian Pepper, Schinus terebinthifolius, are both naturalised alien species which have

established important self-sustainable populations in the Maltese countrys ide.

The natural range of the freshwater snail Helisoma

duryi is the southern parts of the United States of

America. It was introduced into the Maltese Islands as an aquarium snail and is now found in private and public garden ponds. In 1986, a large population of this species was discovered at Wied

il-Luq, Buskett, but this population disappeared in 1988.

Deliberate importation for scientific purposes The Cape sorrel Oxalis pes-caprae, now the commonest plant in the Maltese Islands, was introduced in the beginning of the 19th Century at the Argotti botanical gardens.

There is circumstantial evidence to suggest that the Narrow-Leaved Aster, Aster squamatus was originally introduced in the Argotti Botanical Gardens from where it escaped.

Deliberate introduction for biological control programmes

The ladybird Rodolia cardinalis, a common species in the Maltese Islands, is a native of Australia and was imported into Europe for biological control of scale insects. It was introduced into Malta from Portici (Naples) in 1911 to control infested gardens at St.Julians In the past ten years a number of exotic insects introduced for biological control, including:

?? Dacnusa sibirica and Diglyphus isaea for the

control of leaf miners

?? Encarsia formosa, Eretmocerus californicus

and Macrolophus caliginosus and for the control of the sweet potato whitefly Bemisia

tabaci,

?? Cales noacki for the control of the citrus

whitefly Aleurothrixus floccosus;

?? Orius laevigatus, Orius insidiosus, Amblyseius cucumeris for the control of thrips

?? Aphidius colemani and Aphidoletes aphidimyza

for the control of aphids in greenhouses

?? Phytoseiulus persimilis for the control of red

spider mite

Accidental importation with other species ?? The cottony cushion scale insect Icerya

purchasi, a pest of citrus and other fruit trees

reached Malta from Sicily in 1907 with imported ornamental plants .

?? The citrus whitefly Aleurothrixus floccosus was introduced around 1985.

?? The sweet potato whitefly Bemisia tabaci was introduced around 1993.

Accidental importation with food or other natural products:

? Weeds imported with birdseed and crop seeds

Birdseed (e.g. canary grass, Phalaris canariensis) itself often escapes and naturalises, but it also often includes contaminant species, for example,

Centaurea diluta, which has become naturalised in

disturbed areas at least since the 1960s. A type of cockspur, Echinochloa frumentacea, also occurs occasionally in the wild, as result of it being present as a contaminant in seed mixtures. An exotic species of leech (possibly Limnatis

? Accidental importation with domestic animals

?? Accidental importation with ornamental plants

?? Accidental importation with wood products

nilotica) used to occur in public animal drinking

troughs at Birkirkara in the 1930s. This originated from the inside of the mouth and nasal passages of cattle imported from North Africa.

Examples include: The gallant soldier Galinsoga

parviflora, the liverwort Marchantia polymorpha

and the mushroom Leucocoprinus birnbaumii, as well as the giant terrestrial flatworm Bipalium

kewense. Most of these can only survive in a

greenhouse, however, Galinsoga parviflora seems to be a good candidate for naturalisation on disturbed ground.

At least four species of cerambycid beetles have been imp orted into the Maltese Islands with wood products: Rosalia alpina, a European species imported with ash logs; Morimus asper, a common Italian species whose larvae feed on poplar and elm, imported into the Maltese Islands with firewood at Marsa; Cordylomera spinicornis, a West African species, collected from Santa Venera from imported logs.

Accidental introduction due to shipping:

?? Fouling species (sessile or vagile)

?? Species which are taken on board with ballast water

In 1977 two marine bryozoans not previously recorded from the Mediterranean were discovered fouling the cages of an oyster farm at Rinella:

Celleporaria pilaefera, an Indo-West Pacific

species, and Celleporaria aperta, which has a world -wide warm-water distribution.

An adult specimen of the Indian Ocean sea urchin

Prionocidaris baculosa was collected from the

ballast tank of a ship undergoing repairs in the Malta Dockyards in 1976.

Accidental importation with cargo The Algerian whip snake Coluber algirus and the cat snake Telescopus fallax may have been introduced into Malta with shipments of firewood during the first World War and became established in the vicinity of the then fuel-yard at Floriana. The snake Natrix natrix was collected from Floriana after an Italian circus left from the area. Discarding into the environment of deliberately

imported species.

Examples include: algae (and accompanying micro -biota) used as packing material; mosses imported for use as ‘vegetation’ on Christmas cribs; species used as live bait for fishing; live food for captive animals.

Pruned ornamental plants are often discarded in the wild. As a result, species like Aptenia

cordifolia, Carpobrotus edulis and various Pelargonium, may be found in the wild. The

A number of birds have been released on Comino by an inhabitant, including: Bobwhite, Colinus

virginianus (essentially a Central American bird);

the Chukar Partridge, Alectoris chukar (an Asian species extending to the Balkan peninsula and adjacent Mediterranean islands of the Aegean, Crete and Cyprus); and the Pheasant, Phasianus

colchicus (essentailly an Asian species).

The deliberate planting of potentially invasive non-native species in the Maltese countryside, e.g. deliberate planting of the Mediterranean Oriental Plane (Platanus orientalis) at Wied il-Hmar [l/o Gnejna]; that of the Arizona Cypress (Cupressus

arizonica) at Wied Ghollieqa; that of Bryophyllum

sp. (a succulent potentially highly invasive due to the high production of plantlets by v egetative propagation) at Il-Maghluq ta’ Marsaxlokk. Escape from captivity, for example from

menageries or aquaria

The chameleon Chamaeleo chamaeleon was originally introduced as a pet escaped from St.Julians

Expansion of the range of Lessepsian immigrants The Red Sea sea-grass Halophila stipulacea entered the Mediterranean after the opening of the Suez Canal in 1869 and spread westwards, partially aided by shipping, reaching the Maltese Islands around 1970.

Other Red Sea immigrants now found in the Maltese Islands include: the alga Caulerpa

racemosa; the opistobranch mollusc Bursatella leachi; the Shrimp Cad (a fish) Alepes djedaba;

the Blunt Jaw Barracuda (fish) Sphyraena

chrysotaenia, and probably other species.