<p>A system for establishing a pest barrier (10) across a space (11) bounded by two sides (13). The system comprises a body (25) adapted for insertion into the space (11) to be confined between the two sides (13) for establishing a physical barrier therebetween. The body (25) incorporates a chemical or other treatment for deterring target pests, thereby also establishing a chemical barrier. The body (25) typically comprises a membrane (27) impregnated with the chemical compound. The membrane (27) may be wound into a roll (29) which is inserted into the space (11). With such a construction, the roll (29) may be resiliently compressible laterally for insertion into the space (11). Alternatively, the roll (29) may be allowed to unwind after insertion into the space (11) to an extent that it is confined between the two sides (13) within the space (11).</p>
