Lethal and antifeedant effects of Bordeaux mixture on the marsh slug (Deroceras laeve)

The marsh slug, Deroceras laeve (Müller), is a generalist pest of agricultural crops. Slugs are mainly managed with synthetic pesticides that can also have high toxicity toward vertebrates and nontarget arthropods. Besides, they are not labeled for use in organic crop systems. Bordeaux mixture (BM) is an alternative product often used in organic crops for controlling plant diseases. The molluscicidal activity of BM has been reported; however, to our knowledge, no study has determined its efficacy to control D. laeve. This study aimed to determine the lethal (concentration- and time-mortality curves, and foliar persistence) and antifeedant (reduction in leaf consumption) effects of BM-treated cabbage leaves on D. laeve. The LC₅₀ of BM was 28.15%, and the LT₅₀ was 8.83 h. The BM LC₂₅ reduced D. laeve leaf consumption by 3.31-fold. Furthermore, high control effectiveness (mortality > 90%) was attained until the 7^th day after spraying. These findings reveal that BM reduces damage by killing D. laeve in a fast faction and by reducing foliar consumption. Therefore, BM can be an alternative to D. laeve management in both conventional and organic systems.