Cedar Planks—specifically the oil and wood from the Eastern Red Cedar (Juniperus virginiana) that the Cedar Planks are made of—are proven to have moth-repelling qualities that repel clothes moths. They do not, however, kill them. Cedar's effectiveness against moths stems from the compounds within the wood, giving off a strong scent that deters moths and other insects. The main action of Cedar Planks in moth prevention is to mask the scent of keratin, a moth's natural target.
Cedar is valued not only for its moth-repelling properties but also as a natural, safer alternative to chemical moth repellents like mothballs, which can pose health risks to humans and pets.