Practitioners of classical weed biological control have a long-standing tradition of being concerned about the safety of organisms being considered for release. For decades, possible damage to non-target hosts has been predicted through host range evaluations, usually under laboratory conditions. However, even a highly specific agent can disrupt ecosystem pathways in unpredictable ways, especially if it becomes abundant on its target, but fails to reduce the target's populations. I argue that we should strive to release agents that are not only narrowly host specific, but that will also prove effective in controlling the target weed. Although predicting impact prior to release, especially under laboratory conditions, is challenging, I present an example using a tephritid, Parafreutreta regalis Munroe. This gregarious gall-former from South Africa is being evaluated for possible release in California to control Cape ivy, Delairea odorata Lemaire, a South African vine that has invaded many natural areas in coastal California and upland Hawaii.
Species 1: Diptera Tephritidae Parafreutreta regalis (Cape ivy gall fly)
Species 2: Asterales Asteraceae Delairea odorata (Cape ivy, German ivy)
Species 3: Asterales Asteraceae Senecio mikanioides (German ivy)
Keywords: pre-release impact assessment, biocontrol agent efficacy
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