The introduction and establishment of Aphidius colemani Viereck (Hym, Aphidiinae) in Tonga
In this paper we describe the introduction and establishment of the polyphagous parasitoid Aphidius colemani into Tonga in an attempt to control the banana aphid, Pentalonia nigronervosa. P. nigronervosa is a serious pest of Musa spp. because of direct feeding damage and, more importantly, as a vector for banana bunchy top virus disease. A. colemani was introduced to Tonga from Australia, cleared through post-entry quarantine and mass reared for field release. More than 32000 parasitoids were released on Tongatapu Island, Tonga, between April 1990 and November 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 taro, Colocasia esculenta about 9 months after the cessation of releases confirming its establishment. A. gossypii is one of a number of other species present in the Tongan aphid fauna that are suitable hosts for Aphidius colemani. Experimental studies on the acceptance of alternate aphid hosts by A. colemani are presented; along with information on host suitability. These data show that P. nigronervosa is readily parasitized in the absence of ants.