Hygromiid snails (Monacha spp.) is a mollusk pest.
Monacha is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Hygromiidae, the hairy snails and their allies. In general, temperate terrestrial snails can damage horticultural and agricultural crops through feeding and lowering crop yield and quality. These pests can also damage native plants through feeding activities. Temperate terrestrial snails can transmit pathogens and displace native snail species. Species in the Hygromiidae family are considered serious pests of fodder crops in Europe. Monacha species exhibit a massing behavior when populations reach high levels that can disrupt agricultural operations.