Colonisation of Aphytis melinus DeBach (Hymenoptera, Aphelinidae) in Aonidiella aurantii (Mask.) (Hemiptera, Coccidae) on citrus in South Australia

Abstract

AbstractAphytis melinus DeBach was introduced to South Australia, reared in the laboratory, and then released against Aonidiella aurantii (Mask.) on citrus. In tests in nine citrus orchards, 100 adults of Aphytis melinus ensured colonisation during summer and early autumn, 1000 during late autumn, but even that number was insufficient during winter. Colonisation was equally successful whether Aonidiella aurantii was very abundant or very rare. The most efficient method for colonisation was therefore to release 100 adult parasites during summer and early autumn into small populations of A. aurantii. The parasite had dispersed at least three trees from each summer release site after five months, but much less following autumn releases. Ten months after summer release into nine trees of a total of 3330 adults, Aphytis melinus was recovered from 286 out of 354 (80%) trees in one orchard. In a further experiment, numbers of Aonidiella aurantii were reduced from 300–1000 per 150 leaves on five trees to less than 10 per 150 leaves 18 months after the release of Aphytis melinus, whereas on a control tree they increased from 550 to 1450 per 150 leaves over nine of those months.