Caffeine as a repellent for slugs and snails

At high concentrations this stimulant becomes a lethal neurotoxin to garden pests. Most commercial products for snail and slug control contain either metaldehyde or methiocarb as the active ingredient1, the residues of which are not permitted in food crops in the United States2. We have discovered that solutions of caffeine are effective in killing or repelling slugs and snails when applied to foliage or the growing medium of plants. Because caffeine is a natural product and is classified by the US Food and Drug Administration as a GRAS ('generally recognized as safe') compound3, it has potential as an environmentally acceptable alternative toxicant for the control of slugs and snails on food crops.