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HISPID BEETLE

Promecotheca cumingi Baly -- Coleoptera, Hispidae

(Contacts)

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In a separate project the coconut leaf-mining beetle was accidentally introduced into Sri Lanka where it was discovered in 1970 beginning to develop into a devastating pest of coconuts (Simmonds 1976). In March, 1971, the Commonwealth Institute of Biological Control was asked to advise on the possibilities of biological control, and in view of the very successful control of P. reichei Baly in Fiji in 1937 (Taylor 1937), it was suggested that Pediobius parvulus (Férrière) and Dimmockia javan Férrière be tried. In Fiji both of these parasitoids had been introduced, but Pediobius only was extremely successful (by 1971, 35 years later, the former pest was difficult to find in Fiji and naturally its parasite also. Dimmockia javan following introduction died out. In Sri Lanka there was no reason to believe that the same pattern would not occur, but both Pediobius and Dimmockia were liberated in large numbers. It soon became apparent, however, that in Sri Lanka Dimmockia was to become the dominant parasitoid, with Pediobius apparently becoming established but extremely rare. Successful biological control of Promecotheca was obtained from this effort (Fernando 1972).

Simmonds (1976) suggests that in this example there was a complete reversal of roles played by the two parasitoids in controlling Promecotheca in Sri Lanka and Fiji, although the ultimate practical result was the same. Had detailed ecological investigation preceded parasitoid introduction it is possible that a consideration of details of climatic preferences, host-preferences, life-cycle, etc. of both hosts and parasitoids might have indicated the usefulness in Sri Lanka of Dimmockia rather than Pediobius. But, this is by no means certain. What is certain is that such a detailed study would have deferred the ultimate successful biological control of Promecotheca by more than a year at least, during which time the increase of the pest and subsequent losses from chemical control, etc. would have been considerable, and it would have taken a longer time, with consequent increases losses, to effect biological control and complete recovery of the palms (Simmonds 1976). Although it might be argued that the introduction of natural enemies in this manner is scientifically unacceptable, it must be born in mind that the ultimate unpredictability of the result of such introductions should be left to the natural enemies themselves to determine which is more suited to a new environment (Simmonds 1976).

REFERENCES: [Additional references may be found at: MELVYL Library ]

Fernando, H. E. 1972. The coconut leaf beetle Promecotheca cumingi and its control. Coconut Planters Rev. 6: 152-56.

Simmonds, F. J. 1972. Approaches to biological control problems. Entomophaga 17: 251-.

Taylor, T. H. C. 1973. The biological control of an insect in Fiji. An account of the coconut leaf-mining beetle and its parasite complex. Imperial Inst. Ent., London. 239 p.

Simmonds, F. J. 1976. Some recent puzzles in biological control. Entomophaga 21: 327-32.