Ecological studies of Scaptomyza flava (Fallen, 1823) (Diptera: Drosophilidae) and its parasitoids
2012
Martin, N. A.
Populations of the leafminer, Scaptomyza flava , were monitored fortnightly in turnip plantings at Pukekohe, south Auckland, for more than 2 years. The fly, and its main parasitoid, Asobara sp. (nr. persimilis) (Hymenoptera: Braconidae), were present throughout the year, with populations peaking in midsummer on spring plantings. A replicated field trial, comparing four planting dates, suggests that new leaves on young plants and on flowering stems were favoured for oviposition by the leafminer. In another experiment, young leaves of flowering Gypsophila sp. were more suitable for oviposition and larval survival than leaves of younger non-flowering plants. Measurements of the mandible and associated skeleton confirmed the existence of three leafminer larval instars. The parasitoid has a partial winter diapause. In midsummer, it achieved over 80% parasitism. A survey found Asobara parasitism of S. flava was restricted to a small area of south Auckland. These data, together with its monophagy in New Zealand and molecular analysis, indicate that it is either a species close to A. persimilis or a distinct population of that species.
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