Molluscicidal and insecticidal potential of monoterpenes on the white garden snail, Theba pisana (Muller) and the cotton leafworm, Spodoptera littoralis (Boisduval)

Abstract

The present article reports the fumigant and contact toxicities of eleven monoterpenes against adults of Theba pisana and third instar larvae of Spodoptera littoralis. The majority of the tested compounds were found to be toxic to both pests with variable degrees of potency. Among the tested monoterpenes, (L)-fenchone showed the highest fumigant toxicity against T. pisana and S. littoralis with LC₅₀ values of 2.51 and 2.27 mg/l, respectively. Myrcene and 1-8-cineole exhibited strong fumigant toxicity against T. pisana, while cuminaldehyde, geraniol and (−)-menthol were not active. On the other hand, 1-8-cineole and (+)-camphor revealed potent fumigant toxicity against S. littoralis. In the contact assay, the tested monoterpenes were more toxic against T. pisana than S. littoralis. Cuminaldehyde (LD₅₀=28.37 μg/snail) was significantly the most effective compound against T. pisana, followed by geraniol and (−)-limonene. Interestingly, eight of the tested monoterpenes were more toxic to adults of T. pisana than methiocarb. The results of the present study suggested that cuminaldehyde, geraniol, (−)-limonene and (+)-camphor could be used as alternative control agents for T. pisana. In addition, (L)-fenchone and 1-8-cineole could be useful as fumigants for control T. pisana and S. littoralis.