The parasitoid complex affecting Choristoneura rosaceana and Pandemis limitata in organically managed apple orchards

Parasitism and density of obliquebanded leafroller, Choristoneura rosaceana (Harris), and the three-lined leafroller, Pandemis limitata (Robinson) (Lepidoptera: Tortricidae), were studied in 1998-2001 in organically managed apple orchards in the southern interior of British Columbia, Canada. The density of the overwintered generation of leafrollers in spring was significantly higher than the density of the first generation in summer. There was a significant inverse correlation between the density of leafrollers and the percent parasitism within generation and therefore parasitoids may play a role in controlling leafroller density. Parasitism of the overwintered generation (means between 5.5 and 24.7%) was significantly lower than parasitism documented in the summer generation (means up to 67.9%). The parasitoid complex recorded as emerging from these leafroller populations in 1998-1999 included 30 species, of which eight have not been previously recorded in the literature as parasitoids of either leafroller species. The most frequently occurring parasitoids included Apophua simplicipes (Cresson) and two species of Glypta (Hymenoptera: Ichneumonidae), Macrocentrus linearis (Nees), Meteorus trachynotus Viereck, Apanteles polychrosidis Viereck, Apanteles atra (Ratzeburg) and Microgaster epagoges Gahan (Hymenoptera: Braconidae), Colpoclypeus florus (Walker) and one Sympiesis species (Hymenoptera: Eulophidae). All of these more common parasitoids, except Glypta sp. 1 and M. epagoges, were recorded parasitizing leafroller hosts in both leafroller generations. The number of days to adult parasitoid emergence, when field collected parasitized hosts were held at 20degreesC, was recorded for four of the parasitoid species. Meteorus trachynotus was found to emerge early enough in spring to parasitize the few remaining overwintered early instar leafrollers. Glypta sp. 1, A. simplicipes and one Apanteles species emerged to coincide with the first generation in the summer.