Submitted to: Annals of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2002
Publication Date: 1/20/2003
Citation: Hollingsworth, R.G., Armstrong, J.W., Campbell, E. 2003. Caffeine as a novel toxicant for slugs and snails. Annals of Applied Biology. 142:91-97.
Interpretive Summary: In this study, caffeine was found to act as both a repellent and toxicant against slugs and snails. Slugs and snails were killed when drenched with a 2% solution of caffeine, while lower concentrations caused slugs to exit treated soil. Caffeine solutions as low as 0.01% applied to cabbage significantly reduced slug feeding. Due to concerns about chemical residues, available molluscicides generally cannot be applied directly to food crops for control of slug and snail pests. Caffeine is a natural product which is approved as a food additive. Therefore, caffeine may prove useful for protecting food crops from slugs and snails.
Technical Abstract: In this study, caffeine was found to act as a repellent and toxicant against slugs and snails. To find out if caffeine could be used to remove or kill slugs infesting potted plants, we treated soil containing large slugs with various caffeine solutions. After 3.5 h, only 25% of the slugs treated with 2% caffeine remained in the soil. After 48 h, all slugs had left the soil, and 92% had died. We also tested the effect of caffeine on slugs in choice and no-choice feeding tests. In no-choice tests, the amount of feeding on 'Napa' cabbage leaves relative to the control was 91, 81, 71, and 61% for caffeine dip treatments of 0.01, 0.1, 0.5, and 2%, respectively. In choice tests, the relative amount of feeding on treated leaves averaged 111, 38, 23, and 36% for caffeine solutions of 0.01, 0.1, 0.5, and 2.0%, respectively, while total cabbage consumption for these same treatments averaged 76, 76, 86, and 72%. Caffeine was also tested against a snail pest that feeds on orchid roots. Exposure of snails to 0.01% caffeine in Petri dishes increased heart rate, while higher concentrations decreased heart rate and caused snails to die within 2-4 days. A 2% caffeine drench applied to the media of potted orchids killed 95% of snails and provided better control than a commercial liquid metaldehyde product. Caffeine is a natural product approved as a food additive. Therefore, caffeine may prove useful for protecting food crops from slugs and snails.