Influence of abiotic factors on the molluscicidal activity of a bait containing limonene targeted at the pest snail Lymnaea acuminata

We assessed the lethality of a bait containing both limonene and an attractant (starch or proline) against the pest snail Lymnaea acuminata for every month of the year 2010-2011. Simultaneously, levels of temperature, pH, dissolved oxygen, carbon dioxide and electrical conductivity in test water were measured. In 24h toxicity assays, carried out in May, June and July, lethal concentration (LC50) values of 3.99, 4.47 and 4.44% were obtained for bait containing proline + limonene, and values of 5.45, 4.41 and 5.60% were obtained for bait containing starch + limonene. A significant positive rank correlation was observed between different concentrations of limonene in bait and acetylcholinesterase activity in the nervous tissue of the snail. There was maximum inhibition (57.93%) of acetylcholinesterase activity in snails fed bait containing 80% of the 24-h LC50 of limonene + proline in May. Our results indicate that snail populations can be controlled by a limonene bait formulation applied in a specific month rather than all the year round.