Environmental Entomology (1990) 19, 362-669

Bruce A. Barrett and Jay F. Brunner (1990)
Temporal distribution of Phyllonorycter elmaella (Lepidoptera: Gracillariidae) and its major parasitoid, Pnigalio flavipes (Hymenoptera: Eulophidae), in Washington apple orchards
Environmental Entomology 19 (2), 362-669
Abstract: The seasonal occurrence of Phyllonorycter elmaella Doganlar and Mutuura, a tentiform leaf miner, and its parasitoid, Pnigalio flavipes (Ashmead), in insecticide-free blocks located in commercial apple orchards was determined. P. elmaella had three complete generations each year; population densities increased in each generation. P. elmaella sap feeders (first to third instars) were "abnormally" abundant in the blocks at the end of each season, possibly because of a delay in their development. P. flavipes had at least the same number of generations as P. elmaella. Parasitoid activity decreased as the season progressed. Phenology data showed adult P. flavipes emerged almost concurrently with adult P. elmaella during the spring and summer generations, 2-3 wk before tissue feeders (fourth and fifth instars), were present in the orchard. This emergence pattern may be caused by a reproductive advantage for female P. flavipes to feed on sap feeders before oviposition. The number of individuals of P. elmaella that are able to overwinter successfully, rather than the seasonal levels of parasitism, seems to determine the leafminer's year-to-year population dynamics. However, parasitoid activity reduced the leafminer's intraseasonal population increase and kept its densities below treatment threshold levels in all orchard blocks examined.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Bruce A. Barrett, Jay F. Brunner

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
population dynamics/epizootiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phyllonorycter elmaella	Apple (Malus)	U.S.A. (NW)
Pnigalio minio (parasitoid)	Phyllonorycter elmaella	Apple (Malus)	U.S.A. (NW)