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Biological assessment of Macrocentrus linearis and Apanteles polychrosidis (Hymenoptera: Braconidae) as parasitoids of the obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

Abstract The biologies of two endoparasitoids of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) from organically managed apple orchards in the southern interior of British Columbia, Canada were studied in the laboratory. Macrocentrus linearis (Nees) (Hymenoptera: Braconidae) oviposited into first through fourth instar obliquebanded leafrollers. A sympatric leafroller species found in this area of British Columbia, the three-lined leafroller, Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) was not accepted as an alternate host species by M. linearis. When provided with honey-water and held under fall and summer orchard temperatures, M. linearis females survived significantly longer under fall than summer temperatures ( =28.3±2.4 and 20.2±2.5 days, respectively) but parasitized a similar number of obliquebanded leafroller larvae ( =12.2±5.0 and 24.4±9.2 larvae, respectively). A mean of 20.6±4.9 larvae emerged per parasitized obliquebanded leafroller in the host's fifth or sixth instar. Obliquebanded leafroller larvae parasitized by M. linearis consumed significantly more diet than unparasitized hosts from fifth instar to pupation, suggesting that M. linearis may not reduce host feeding damage to fruit except through the ultimate reduction of host populations. Apanteles polychrosidis Viereck (Hymenoptera: Braconidae) parasitized the first through third instars of both the obliquebanded and three-lined leafrollers. When provided with honey-water and held at temperatures typical of either fall or summer in orchards, A. polychrosidis females survived significantly longer ( =46.6±3.1 and 26.4±2.5 days, respectively) and parasitized significantly more obliquebanded leafrollers under fall than summer temperatures ( =61.5±7.2 and 18.4±5.3 total larvae, respectively). A single A. polychrosidis larva emerges from a third or fourth instar leafroller host. Consequently, parasitized obliquebanded leafroller larvae consumed significantly less diet than unparasitized larvae from fourth instar to pupation. Attributes of both parasitoids are compared with those of another common obliquebanded leafroller parasitoid, Apophua simplicipes (Cresson) (Hymenoptera: Ichneumonidae).