Graduate Thesis Or Dissertation
 

Distribution, phenology, and parasitism of the winter moth, (Operophtera brumata L.), in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/j6731603b

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  • An exotic pest of deciduous plants, Operophtera brumata (L.), was discovered in Portland, Oregon in 1978. O. brumata, the winter moth, is native to northern Africa and temperate Eurasia. Its range extends from Scandanavia, Britain, and France to Japan. It is also now well established on the North American continent in Nova Scotia and on Vancouver Island, British Columbia. Surveys for distribution, host range, and levels of parasitism were conducted in the Willamette Valley of Oregon from 1978 to 1980. The seasonal occurrence of all life stages was also monitored. In particular, an investigation to determine the time of larval eclosion was conducted in the field and laboratory. The information obtained from these studies helped to optimize the time of release of two exotic parasitoids, Cyzenis albicans (Fallen) and Agrypon flaveolatum (Gravenhorst), for biological control of the winter moth. O. brumata is distributed throughout the northern Willamette Valley and has been detected as far south as Salem. Distribution was determined by the presence of adults in the winter and larvae in the spring on a variety of host plants. Highest numbers of larvae (5+ larvae/ten leaf clusters) were found on Corylus spp. (commercial and native filbert), Prunus cerasifera J.F. Ehrh. (flowering plum), and Malus sylvestris Mill, (crabapple). The widely distributed native oak, Quercus garryana Dougl., was not heavily infested. The seasonal occurrence of each life stage was monitored in 1979 and 1980. Peak emergence of adult females occurred between 15 November and 5 December in 1979 and 1980. Males were observed in flight early in November of both years. Larvae generally eclose in mid-March and pupate by mid-May. However, there were significant differences in the timing of instar development between years. The occurrence of first instar larvae (50 percent of the accumulated total) differed by 21 days on a calendar time scale. The occurrence of fifty percent of fifth instar larvae differed by 8 days between years. These differences can be attributed to environmental conditions. Laboratory and field work was conducted each winter from 1981 to 1984 to determine the timing of larval eclosion. The developmental threshold temperature for larval eclosion was determined to be 4C. Chilling eggs below the developmental threshold temperature affected the subsequent number of thermal units required for eclosion. Chilling accelerated the rate of diapause development and shortened the hatching period. The state of diapause is terminated in mid-January when temperatures above the lower developmental threshold become more frequent. Surveys for larval parasitism in 1980 and 1981 resulted in the recovery of six species of indigenous parasitoids. However, rates of larval parasitism were low, averaging only 4.5% and 12.2% in both years, respectively. Two exotic parasitoids, C. albicans and A. flaveolatum, were introduced into areas of known winter moth infestations in 1981 and 1982. C. albicans has been recovered by trapping adults or rearing flies from field collected hosts from four release sites, but no A. flaveolatum have been recovered.
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