The invention relate to spreading device (1) adapted to be administer onto a tree stump (T) a composition which comprises microbial propagules to control or prevent the growth of a forest pathogen. The spreading device comprises: a spreading end (3) connected to a pipe-like frame (2), and administering means (4) for administering said composition, wherein said administering means (4) comprise a pressure accumulator (42) for loading pressurized air (I). Said pressure accumulator (42) is connected to a first end of the pipe-like frame (2) via a supply pipe (413) and regulating means (41) which comprises at least one regulating valve (411) for regulating flow of the pressurized air (I) entering the frame (2) which regulating means (41) further comprises communication means (47) for providing to at least one regulating valve (411) data about starting time of pressurized air (I) delivery and data about duration of said pressurized air (I) delivery, wherein said pressure of delivered pressurized air depends on the diameter of the tree stump. The invention also relate to a method for controlling the growth of a forest pathogen.
