The banana aphid, Pentalonia nigronervosa, is a small, soft-bodied pest which occurs throughout the Pacific and, because it carries bunchy-top virus, is responsible for serious crop losses. Bunchy-top virus creates a virtual 'bonsai' banana, stunting the tree's growth and deforming its leaves. CSIRO researchers are working on introducing a parasitic wasp, Aphidius colemani, as a biological control agent for the banana aphid. Trials with the wasp are being carried out in Tonga.