Abstract: Using sachets as a delivery system for the predatory mite Amblyseius swirskii into acrop is popular with growers as the inoculation of predators is slower and provides an element offlexibility over the timing of the introduction. The sachet itself is a complicated microenvironment,providing refuge and food for A. swirskii, generally in the form of a factitious hostmite, Carpoglyphus lactis, which itself is sustained by materials within the sachet. The sachetshould be able to maintain a breeding population of A. swirskii, whilst releasing predators at theappropriate rate and duration. This paper describes four field trials undertaken in differentclimates to compare the C. lactis prey mite sachet system with that of an alternative prey mite,Suidasia medanensis. It was found that C. lactis released predators more rapidly than theS. medanensis system in the first seven-days. However, the release profile of the S. medanensissachets demonstrated a more sustained presentation of A. swirskii into the crop during subsequentweeks. The implications of these different release profiles for the end-users are discussed.