Did biological control cause extinction of the coconut moth, Levuana iridescens, in Fiji?

Abstract

In 1925, J.D. Tothill and two colleagues set out to manage Levuana iridescens, the coconut moth of Fiji, using biological control. By 1930, they had succeeded so completely that this pest of the copra crop had been reduced to almost undetectable levels by the tachinid fly, Bessa remota, introduced from Malaya, and they had summarized their campaign in a thoroughly documented and well-illustrated monograph. The example of the coconut moth is presented in the modern literature as the first and best documented extinction of a species due to scientific biological control. The program has been severely criticized because the moth was unique, beautiful, and considered endemic to Fiji. Thus, this program is also portrayed as an example of the highly controversial practice of neoclassical biological control. However, a careful reexamination of this event discloses that the moth was likely not native to Fiji, appeared to be spreading through the Fijian Archipelago, and might have spread to other island groups in the South Pacific. Also, L. iridescens is probably not extinct. Collateral damage, that is, non-target impacts, did occur as native zygaenid moths have been attacked by the tachinid, and they may be extinct. The reasons for the control campaign of L. iridescens were not primarily economic. Tothill and colleagues were trying to protect copra so that ethnic Fijian culture, so dependent on the coconut palm threatened by L. iridescens, could be sustained. Hence, this control program represents a difficult clash of values: preservation of insect biodiversity versus preservation of indigenous Pacific Islander cultures. A strategy to search for L. iridescens populations is proposed and development of biological control of B. remota, using hyperparasitoids, is possible, but would require careful evaluation since it might release L. iridescens from suppression, have non-target impacts on native tachinids, and lack an economic motivation.