Oviposition Marking Behavior of Diachasma alloeum, (Hymenoptera: Braconidae), Parasitizing Rhagoletis pomonella, (Diptera: Tephritidae)
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Diachasma alloeum (Muesebeck) (Hymenoptera: Braconidae) is a solitary larval endoparasitoid attacking Rhagoletis (Diptera: Tephritidae) species. Rhagoletis pomonella (Walsh) mark the surface of fruit after oviposition with an oviposition marking pheromone (OMP) which deters conspecific female flies. Herein we demonstrate that female D. alloeum wasps reared from either apple or hawthorn race R. pomenella larvae also deposit an OMP that reduces oviposition by conspecific female wasps. Significantly fewer wasps accepted fruit that had received prior wasp oviposition and OMP or OMP alone without oviposition compared with control fruit for a minimum of 7 days on both fruit types. Rinsing fruit with a 50% ethanol solution appeared to remove the OMP rendering fruit more acceptable for oviposition than marked fruit that was not rinsed. Wasps of each host race were able to detect and avoid the OMP of the sister race and fruit substrate type did not affect wasp response to the pheromone. The possibility of an internal marker deposited during oviposition is also discussed.