BIOLOGICAL AND MICROBIAL CONTROL Parasitism of Obliquebanded Leafroller (Lepidoptera:Tortricidae) in Commercially Managed Michigan Apple Orchards

The obliquebanded leafroller, Choristoneura rosaceana (Harris), is one of the major arthropodpests of apple in theUnitedStates. In 1999 and2000, a surveyof theobliquebanded leafroller parasitoid complex incommerciallymanagedappleorchards inMichiganÕs two largest fruit production regions was conducted to determine the species present and their importance to obliquebanded leafroller population management. In total, 8,961 obliquebanded leafroller larvae were collected of which 2,174 were parasitized. Parasitism increased from the overwintering generation to the summer generation for both regions and both years. In 1999, 11% of the 1,126 overwintering obliquebanded leafrollers collected were parasitized, whereas 28% of the 3,669 summer generation were parasitized. In 2000, 8% of the 489 overwintering obliquebanded leafrollers collected were parasitized, whereas 26% of the 3,677 summer generation obliquebanded leafrollers collected were parasitized. In total, 20 species of hymenopteran and dipteran parasitoids from seven families were recovered from obliquebanded leafroller larvae over the course of the study. The most abundant hymenopteran parasitoids were Bassus dimidiator Nees (Braconidae) comprising 48% of the total parasitoids, followed by Colpoclypeus florus (Walker) (Eulophidae) (8% of the total) and Macrocentrus linearis (Nees) (Braconidae) (2%of the total).Dipteranparasitoids (Tachinidae) accounted for 36%of theparasitism andwere largely comprisedofNilea erecta(Coquillett) (5%)andActia interruptaCurran(13%).These collections represent new host records for B. dimidiator, Bassus annulipes (Cresson)Hyphantrophaga blanda (Osten Sacken), andCompsilura concinnata (Meigen). The parasitoidC. florus is also reported from Michigan for the Þrst time.