Keeping your garden slug free Control with Parasitic Nematodes (Phasmarhabditis sp.): Microscopic transparent worms which feed & multiply inside the slug, not visible with a hand lens. Dilute with water before use. Must be applied to moist compost/soil anytime between May & September. One infected the slug stops feeding. The Nematodes will provide protection from slugs for Approx. 6 weeks. Arguably a gardeners number one pest! Use our biological control method to keep your garden slug free.