Anoth web site;
http://www.bbc.co.uk/nature/animals/...feature4.shtml

comments that
The worm [nematode] forms a self-perpetuating population in summer
but can be killed by drought and is wiped out by British winters,
and so colonies have to be re-established each year at expense.

but also has an interesting suggestion that;
Biological control experts at Ohio State University in the United
States recommended a more economical method of application,
concentrating localised doses in slug shelters baited with bran,
designed to attract slugs into a killing zone rather than
spreading the parasite thinly over a large area.

elsewhere in the same article there is a comment about slugs foraging
over a range of 12 - 45 square meters. So on one hand you can bait
selected points and attract slugs into there from 2 - 4 meters around
it or on the other hand any treated area less than 2-4 meters from an
untreated area will just be recolonised.

JB

On 22 Feb 2005 04:23:45 -0800, "Kieran23"
wrote:

JB,

that link was interesting. My interpretation was that a nematode
programme one year may do enough damage to the slug population that
year to limit egg-laying in subsequent years.

I've yet to find out what percentage of the nematode population
survives over winter, so the effect could be more profound, and the
cost/benefit case for one summer of applications made stronger.