Caffeine for Slugs

In the May-June,2004 TNG, Flora, the magazine's resident horticulturist, reported on the success of a 2% caffeine solution in dealing with slugs in the garden. Readers, however, were puzzled. Exactly how does one arrive at a 2% caffeine solution? This is Flora's response.

A cup of instant coffee contains about 0.05% caffeine, and brewed coffee has even more. So a good strong pot of brewed coffee or an instant pot with double the usual spoonfuls would probably be usefully effective since a 1% solution showed excellent results. A good cup of expresso would almost guarantee success. As one experimenter said, "Research ....has shown that the stimulant is LETHAL to the pests and REPELS THEM AT CONCENTRATIONS LOWER THAN THOSE FOUND IN A CUP OF WATERY AMERICAN COFFEE." SO if you are determined to KILL them, make a strong solution; if REPELLING is enough, just dump your left over morning coffee on the soil around the infested area.

Caffeine for Slugs

Information from National Garden Club Site