" ......Or, if you want to be more natural in the control of the slugs,
douse them and the soil with quintuple strength coffee....."

I think it needs to be more like 10 times the normal strength, needs to
be around 3% Caffeine. and then it's contact not residual.

EXPERIMENT 1 RESULTS: Few slugs exited the soil over a period of
seven days following spraying with a caffeine concentration of 0% or
0.1%, but more than 70% of the slugs exited the soil within one day
following spraying with a caffeine concentration of 0.5% or 1%, and 100%
of the slugs exited the soil within two days (86% within one hour)
following spraying with a caffeine solution of 2%. Mortality rose to
around 90% two days following spraying with 2% caffeine.
EXPERIMENT 2 RESULTS: Leaf consumption was reduced by 39% with 2%
caffeine and by 29% with 0.5% caffeine in the no-choice trials. Leaf
consumption relative to that of leaves dipped in distilled water was
reduced by 64% with 2% caffeine and by 23% with 0.5% caffeine in the
choice trials.
EXPERIMENT 3 RESULTS: Heartbeat rates of snails treated with 0.1%,
0.5%, or 2% caffeine were significantly reduced relative to the
heartbeat rates of untreated snails. More than 90% of the snails treated
with 2% caffeine died within two days; all snails treated with 0.5% or
2% caffeine died within four days. No untreated snails or snails treated
with 0.01% caffeine died within four days.
EXPERIMENT 4 RESULTS: Spraying with 1% caffeine resulted in 55-65%
snail mortality, while spraying with 2% caffeine gave approximately 95%
mortality. Drenching with 2% resulted in significantly higher mortality
than drenching with metaldehyde.
Some foliar phytotoxicity symptoms have been reported due to 2%
caffeine applications, especially if the leaves were not rinsed off
within a week. Severe damage to cabbage and lettuce leaves resulted from
dips in 2% caffeine after the leaves had been harvested, but foliar
sprays of 2% caffeine did not damage the foliage of growing lettuce
plants.
Currently, the U.S. Food & Drug Administration considers caffeine to
be a GRAS (generally recognized as safe) chemical; it is allowed in soft
drinks at a concentration of 0.02%. However, pure caffeine is quite
toxic to humans, and its legal use as a pesticide in the U.S. has been
approved by the Environmental Protection Agency only in Hawaii (to
control frogs, NOT molluscs), where pure caffeine powder is considered a
³restricted use² pesticide and must be applied only by Certified
Applicators. As we noted in February 2003, instant coffee (as drunk)
typically contains approximately 0.05%, and brewed coffee has a bit
more. It would take a REALLY STRONG BREW of coffee to approach the
percentages of caffeine found by the Hawaiian researchers to be highly
effective against molluscs.


--
David Hill
Abacus Nurseries
www.abacus-nurseries.co.uk