Success in biological control is dependant upon the accumulated achievements or outcomes during a project. Some stages are not critical and the failure to undertake a preferred aspect might not jeopardise the success of the project. For example, a successful agent may be found although the whole of the native range of the weed was not explored. Other stages are critical. For example, establishment of an agent is a necessary precursor to damaging the weed. While there are outcomes in a project over which the research has little influence, such as, the level of host selection of an agent, there are others over which the researcher has great influence, such as, methods of foreign exploration, rearing techniques, selection of release sites for establishment, etc. It is most important that the researcher takes great care over the areas of the project that he/she can influence.

Projects, beginning with exploration for new agents, are undertaken by organisations in a few countries (eg. South Africa, Australia, USA). Other countries utilise information and agents already known. In these latter instances, the first steps in the projects involve obtaining a colony of the desired agent, rearing it, sometimes undertaking tests to confirm host specificity, mass-rearing and release. Suggestions about how to gain the best overall result through careful management during these steps are discussed on the following pages.

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