On Thu, 24 Apr 2003 09:09:55 +0100, "david"
wrote:

Excuse me for top posting David, but yours is a very long message
and I doubt the thread will get complicated from here on.

Whatever the strength with regards % of caffeine wise, I reckon on
a jar of strong Nescafe instant in about a litre of water. To some
people I know this is not far short of quintuple strength! Not really
- OK!

It seems to have worked for my Crambe (eaten alive last year) and
one or two select others however this is not a good guide as the very
dry weather so far this year has kept the molluscans numbers down
anyway.

Whatever. You were assiduous in your kindness by pointing out that
"five teaspoons of instant coffee in a mug concentration" is hardly
adequate. I would be hopeless at writing cookery books!

Respect

Hussein

" ......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.

Grow a little garden

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