Abstract: Phasmarhabditis nematodes for the biocontrol of agricultural and horticultural pests and more particularly to the biocontrol of molluscs. The nematodes are cultured with a nematode growth-promoting and pathogenicity-inducing bacterium and applied to the molluscs. The molluscs which are biocontrolled by the disclosed method include slugs, i.e. Deroceras reticulatum. In addition to the specific biocontrol of slugs the invention is applicable to the biocontrol of other molluscs, such as snails, i.e. Monacha cantiana, which are harmful to plants in the field or greenhouse, or to those which carry parasites harmful to humans or animals.