Then I moved to a condominium and started growing under lights in my basement. I assumed that I still had lots of the little beasties, so when I read in Nature Magazine that caffeine is a repellant for them I decided to look into it. I contacted one of the authors (he grew orchids) who assured me that he had used it on many genera and had never seen a problem. The article cites a 2% caffeine solution. The author told me that a 1% solution seems to be good, too, but that 0.1% does no good, and that 0.5% is probably marginal at best (I am quoting this from memory).
Strong coffee contains only about 150 mg in eight ounces (ca 0.064%). Red Bull, the strongest of the new wave (at the time, 2003) of caffeinated drinks had only 80 mg in 8.2 ounces (0.033%). Clearly none of these would do.
I found a product called Amphetrazine: tablets containing 200 mg each. I bought (on the net) a bottle of 100, 20 grams of caffeine total. This is enough to make 2 liters of a 1% caffeine solution. Caffeine is reasonably soluble in water, but makes up only a third of the weight of a tablet. The rest is filler and a blue dye. So harking back to my long career as a chemist I extracted the caffeine with water and got almost two liters of a blue solution (probably a dye added by the manufacturer). BTW, I used protective measures: gloves, respirator, etc.; concentrated solutions of caffeine can be toxic.
Up to this point I had assumed that I had a decent population of bush snails as well as a few slugs, to experiment on but I wanted to get a base point so I could measure the decrease in the population. On thirty potato slices there was only one slug and only 3 bush snails. This would never do! I needed lots of them if I were going to be able to measure the effectiveness of the caffeine, so I decided to wait; surely the population would grow. Now they seem to have vanished entirely! When this thread was re-opened I decided to scout again. No slugs or bush snails on 40 potato slices!!! I still have a bottle of unused caffeine solution.
Why is this? Maybe it's because I diligently wash the roots of all my plants when I re-pot. Or maybe the combination of Enstar II and Mavrik Aquaflow, the only insecticide I use (and not very often) has an effect on slugs and snails, or maybe the floor being concrete instead of gravel has something to do with it.
Or maybe I am living a good life, or it's because I am a few miles closer to the ocean, or the magnetic declination is different. One thing is certain: I will continue to wash the roots thoroughly when I re-pot.
martin
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