Two Lepidopterous leafminers have been observed on sweet potato at Koronivia, Fiji. The Gracillariid Acrocercops prosacta Meyr. is the more abundant species in most areas but populations of a Lyonetiid, Bedellia ipomoeae Bradley, reach damaging levels in fields sprayed with dieldrin for control of weevils (Cylas formicarius elegantulus (Summers) and Euscepes postfasciatus (Fairm.)). Such treatment is shown to reduce parasitisation of B. ipomoeae by a species of Apanteles near A. tapatapaoanus Fullaway and of A. prosacta, by another Braconid, a species of Mesocoelus near M. acrocercopsis Mues. However, outbreaks of B. ipomoeae could not be attributed to such reduction. Elimination of ant predation by the dieldrin sprays was more likely to have initiated the outbreaks.

Sprays containing malathion, diazinon, or dieldrin killed larvae, but not pupae, of B. ipomoeae. Outbreaks of B. ipomoeae can probably be prevented by relying on cultural methods to control weevils or by intensifying insecticide applications to control both B. ipomoeae and the weevils.