Association of the Opiine Parasitoid Diachasmimorpha tryoni (Hymenoptera: Braconidae) with the Lantana Gall Fly (Diptera: Tephritidae) on Kauai

Abstract

Parasitization of the lantana gall fly, Eutreta xanthochaeta Aldrich, by an introduced larval fruit fly parasitoid, Diachasmimorpha tryoni (Cameron), was assessed by measuring total host and parasitoid recruitment in patches of lantana plants growing in 3 distinct ecological habitats on the island of Kauai. Over a 17-wk period, means of 87, 261, and 276 E. xanthochaeta galls were recruited per 10-m2 patches of lantana growing in a lowland pasture (elevation approximately 124 m), a midelevation sugarcane field (elevation approximately 500 m), and an upland forest (elevation approximately 1000 m), respectively. From 42 to 72% of all newly developed galls recruited were lost before reaching maturity from predation (presumably by birds and rodents), damage by the lantana tortricid moth, Crocidosema lantana Busck, or natural abortion inside the gall. Between 28 and 58% of newly recruited galls matured successfully. Percentage parasitism of E. xanthochaeta by D. tryoni varied significantly with ecological habitat: 4.1, 1.2, and 28% of mature E. xanthochaeta galls were parasitized by D. tryoni in the lowland pasture, the midelevation sugarcane field, and the upland forest, respectively. Percentage parasitism did not vary significantly with the number of galls recruited in each patch. Parasitoids emerging from field-collected E. xanthochaeta were significantly larger and had significantly more female-biased sex ratios (1.7:1) than those emerging from their normal rearing hosts, Ceratitis capitata (Wiedemann). Still, D. tryoni may not play a major role in regulating populations of E. xanthochaeta because it lacked a spatial density-dependent response to gall fly populations. Further studies are needed to determine how ecological habitat characteristics influence patterns of exploitation of E. xanthochaeta by D. tryoni.