A testing sequence for reducing rejection of potential biological control agents for weeds

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Abstract
Summary: Many insect agents, selected for the biological control of weeds and tested under restricted cage conditions, have been rejected as unsafe for introduction because of an apparent increase in host range compared with that observed under natural conditions. These aberrant results appear to be due to the insects' inability to follow the normal behavioural sequence based on appropriate cues which lead to correct host selection. It is suggested here that a reverse sequence of testing which progressively reduces the degree of restriction and deletes unattacked plants at each stage, until only a few remain to be tested under conditions as near natural as possible, would allow previously rejected insects to be used as biological control agents.