Orange tortrix : parasitoid complex and thermal constants for egg hatch

Graduation date: 1983An investigation was conducted in 1980 and 1981 on the larval\ud parasitoid complex of the orange tortrix, Argyrotaenia citrana\ud (Fern.), a major contaminant in cane fruits (Rubus spp.) in the\ud Pacific Northwest. A total of 13 parasitoid species were reared from\ud 1,350 larvae predominantly collected from red raspberries in western\ud Oregon. The six most numerous were Apanteles aristoteliae Vier.,\ud Meteorus argyrotaenia Johan., Phytodietus vulgaris cress., Oncophanes\ud americanus (Weed), Enytus eureka (Ash.), and Diadegma spp. The rate\ud of parasitism averaged 20% in two commercial fields which had large\ud larval populations of A. citrana. Conversely, five fields with\ud relatively low density A. citrana populations averaged 66% apparent\ud parasitism. This suggests that parasitoids may be important in\ud maintaining orange tortrix populations at low levels. Three braconid species, A. aristoteliae Vier., M. argyrotaeniae Johan., and O.\ud americanus (Weed) were responsible for 82% of the difference in\ud apparent parasitism between the two levels of infestation noted.\ud Each of the six most abundant species reared were studied\ud relative to host sizes parasitized, alternate hosts in caneberries,\ud overwintering habits, developmental rates and adult longevity at 20°C.\ud The obliquebanded leafroller, Choristoneura rosaceana (Harris) and the\ud omnivorous leaftier, Cnephasia longana Haw, were observed to serve as\ud alternate hosts of M. argyrotaeniae and O. americanus but not A.\ud aristoteliae. All three braconids plus P. vulgaris were successfully\ud reared in the laboratory from A. citrana. Using data from constant\ud temperature rearings and the field, A. aristoteliae was indicated to\ud have 3-4 generations per year by a generic, computerized phenology\ud model (PETE). Insufficient data were obtained to validate the model\ud for predictive capabilities, however. Observations on P. vulgaris\ud indicated that photoperiod is primarily responsible for diapause\ud induction and termination in the laboratory.\ud The thermal constants 5°C and 146°C-days were derived by the\ud lowest coefficient of variation method for the prediction of orange\ud tortrix egg hatch. Total interval for mating, preoviposition, and 50%\ud oviposition by adults caged over red raspberries during summer and\ud fall averaged 3 days. Differences in adult emergence between sexes\ud for field-collected larvae and pupae were not significant. Results on\ud emergence, mating, oviposition, and thermal requirements for egg\ud development are discussed relative to pest management