For general invasive earthworm information there's a great website:
http://www.dnr.state.mn.us/invasives/terrestrialanimals/earthworms/index.html
And the best titled review article ever:
Pandora's Box Contained Bait: The Global Problem of Introduced
Earthworms
http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.39.110707.173426
Annual Review of Ecology, Evolution, and Systematics
Vol. 39: 593-613 (Volume publication date December 2008)
If I remember correctly, it is important to draw a distinction between
forest-dwelling worms (bad) and open-habitat worms (benign or native)
The article abstract:
Introduced exotic earthworms now occur in every biogeographic region
in all but the driest or coldest habitat types on Earth. The global
distribution of a few species (e.g., Pontoscolex corethrurus) was
noted by early naturalists, but now approximately 120 such peregrine
species are recognized to be widespread from regional to global
scales, mainly via human activities. Species adapted to human
transport and to colonization of disturbed habitats are most
widespread and are the principal invasive species. We identify a
number of endogenous and exogenous factors that may contribute to the
successful establishment and spread of peregrine species.
Quantification of these factors may help to determine why certain
species become invasive while others do not. Recent advances in theory
and modeling of biological invasions and in molecular techniques
should prove fruitful in improving our understanding of invasive
earthworms, as well as in predicting their impacts on ecosystems.
