Feeding deterrent effect of carvone, a compound from caraway seeds, on the slug Arion lusitanicus

The feeding deterrent effect of can,,one on the slug Arion lusitanicus was investigated. Carvone, a natural compound from caraway seeds, was incorporated into mulch to reduce its inherent volatility. In a laboratory choice experiment, boxes were filled on one side with carvone-treated mulch and on the other side with untreated mulch. At carvone concentrations ranging from 0.03-0.75 ml litre(-1) mulch, slugs ate significantly more lettuce on the untreated side. In a laboratory based no-choice experiment, carvone concentrations of 0.25 and 0.75 ml litre(-1) mulch significantly reduced slug feeding in comparison with the untreated control. Moreover at the highest concentration of carvone (0.75 ml litre(-1) mulch) 50% mortality was recorded over a period of 5 days, indicating a clear molluscicidal effect. Due to its volatility carvone did not decrease plant defoliation by A. lusitanicus when applied directly onto lettuce, Subsequent field evaluation showed 0.75 ml litre(-1) mulch to partially reduce slug feeding damage. However, this effect was not sufficient to significantly increase lettuce yield. The incorporation of a higher carvone concentration into mulch is still to be tested to confirm whether carvone-treated mulch can be recommended as an effective alternative approach to chemical slug control.