Using nematodes
These biological controls are very effective in controlling some of the worst garden pests, such as slugs, vine weevil, ants and leatherjackets. They are perfectly safe to handle and have no detrimental impact on other species or on soil chemistry.
Nematodes are microscopic worm-like creatures that occur naturally in the soil and rely on soft-bodied prey to survive. They are specific to the pest so you can’t use a nematode for slug control on vine weevil for example. The formulations are supplied chilled, in powder form, and watered into the soil or pot where a pest issue has built up. They work best soaked into well-drained soil or compost where they can swim to their hosts. It’s gruesome, but nematodes enter the grub, breed and then feed on the decomposing bodies.
Mail-order suppliers are best as they are dispatched to you when soil temperatures are right for success. Some formulations that last a bit longer are now available in garden centres.