Great ramshorn snail

Systematic position: The Great ramshorn snail (Planorbarius corneus) belongs to the phylum Mollusca, class Gastropoda, family Planorbidae. It is a large, freshwater pulmonate snail commonly found in stagnant or slow-moving water bodies with dense aquatic vegetation.

Crops damaged: This pest is a significant threat to aquatic plant nurseries, decorative ponds, and hydroponic systems. It feeds voraciously on the soft tissues of various hydrophyte species, including water lilies (Nymphaea), elodea, and vallisneria, particularly targeting tender young shoots and submerged foliage.

Biology and life cycle: As a hermaphrodite, the Great ramshorn snail exhibits a high reproductive potential. Females lay numerous eggs encased in protective gelatinous masses directly onto the leaves of aquatic plants. The development of juveniles is rapid and highly dependent on water temperature. Their ability to utilize atmospheric air allows them to thrive in environments with low dissolved oxygen levels.

Damage and harmfulness: The snail uses its radula to scrape away plant epidermis, which results in irregular holes or complete skeletonization of the leaf blades. Significant damage often leads to the decline or death of the host plant. Furthermore, these snails can act as intermediate hosts for various trematodes, posing an additional risk to aquatic environments and cultivated fish populations.

Control measures: Managing Planorbarius corneus requires an integrated pest management approach:

• Manual removal of adult snails and regular inspection of plants to destroy egg clutches before they hatch.
• Introduction of natural predators, such as malacophagous fish (e.g., black carp), to keep population densities low.
• Use of baited traps filled with lettuce or vegetable scraps, which can be removed periodically to reduce snail numbers.
• Application of molluscicides, which should be done cautiously to avoid disrupting the ecological balance of the water body.