This document specifies a horizontal method for the enumeration of yeasts and moulds present in plant biostimulants intended for use in agriculture, by means of the colony count technique after aerobic incubation at 25 °C ± 2,5 °C. This document allows the enumeration of yeasts and moulds, in technical and formulated plant biostimulant, both in liquid and solid state. The method is applicable to microbial plant biostimulant except those composed of fungi or yeast to verify that the concentration of yeast and moulds does not exceed the respective limits described in the EU Fertilisers Regulation [1]. If necessary, yeast and mould enumerated can be identified using suitable identification tests.