THE INTRODUCTION AND ESTABLISHMENT OF APHIDIUS-COLEMANI VIERECK (HYM,APHIDIINAE) IN TONGA

In this paper we describe the introduction and establishment of the po lyphagous parasitoid Aphidius colemani into Tonga in an attempt to con trol the banana aphid, Pentalonia nigronervosa. P. nigronervosa is a s erious pest of Musa spp. because of direct feeding damage and, more im portantly as a vector for banana bunchy top virus disease. A. colemani was introduced to Tonga from Australia, cleared through post-entry qu arantine and mass reared for field release. More than 32 000 parasitoi ds were released on Tongatapu Island, Tonga, between April 1990 and No vember 1991. Results of surveys conducted during the project have not provided evidence for the parasitoid attacking P. nigronervosa in the field. However, A. colemani was recovered from Aphis gossypii on tare, Colocasia esculenta about 9 months after the cessation of releases co nfirming its establishment. A. gossypii is one of a number of other sp ecies present in the Tongan aphid fauna that are suitable hosts for Ap hidius colemani. Experimental studies on the acceptance of alternate a phid hosts by A. colemani are presented; along with information on hos t suitability. These data show that P. nigronervosa is readily parasit ized in the absence of ants.