Egg parasitoids and predators of the douglas-fir tussock moth, Orgyia pseudotsugata (Lepidoptera : Lymantriidae), in British Columbia
| dc.contributor.author | Young, David Steven | en_US |
| dc.date.accessioned | 2024-08-15T20:19:53Z | |
| dc.date.available | 2024-08-15T20:19:53Z | |
| dc.date.copyright | 1995 | en_US |
| dc.date.issued | 1995 | |
| dc.degree.department | Department of Biology | en_US |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | Field collected egg masses of the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), were reared to identify the species of egg parasitoids occurring in British Columbia, investigate the seasonal oviposition activity of the parasitoids, and determine the proportion of egg mortality caused by each species. Telenomus californicus Ashmead was the dominant species in all of the study areas which included the Kamloops, Ashcroft, Vernon, and Hedley areas. Telenomus dalmani (Ratzeburg) was also reared but contibuted very little to the overall egg parasitism. The combined parasitism by these species was generally very low and ranged from Oto 20.9% of eggs collected in the fall and from 0.05 to 17.7% of eggs collected in the spring. Evidence suggests, however, that parasitism by Telenomus spp. may reach from ca. 52% to greater than 90%. Parasitism by these species of the egg masses collected in the spring was over twice as high as that for eggs collected in the fall at the same six sites. The highest levels of parasitism generally occurred at younger infestations where egg masses were relatively scarce but the relationship between percent parasitism to the estimated age of infestations was not significant. All of the infestations occurred within either the Ponderosa Pine (PP) or interior Douglas-fir (IDF) biogeoclimatic zones, but no relationship could be established between these zones and the observed levels of parasitism. Members of the Trichogramma minutum complex were only responsible for parasitizing O to 7% of the eggs at sites and the overall parasitism by all others species was less than 1 %. A key for identifying common egg parasitoids of Douglas-fir tussock moth in B.C. was created. Naturally-occurring and artificially-stocked egg masses were used to quantify the mortality due to predation on overwintering egg masses in the Kamloops and Ashcroft areas. In the Ashcroft area, 1.9% of artificially-stocked egg masses was completely removed and 2.3% of the naturally-occurring egg masses was missing. In the Kamloops area 15.0% of the artificially-stocked egg masses was completely removed and 12.5% of the naturally-occurring egg masses was missing. The infestations at the study sites in the Kamloops area were smaller and had much lower densities of Douglas-fir tussock moth than those in the Ashcroft area. An investigation of predation on naturally-occurring egg masses within the crown of Douglas-fir indicated that the level of predation among the lower, middle and upper crown level was not significantly different. However, evidence also indicates that avian predators will feed more in the crown level which contains the largest number of egg masses. The mountain chickadee, Parus gambeli Ridgeway, red-breasted nuthatch, Sitta canadensis L., and dark-eyed junco, Junco hyemalis L. are implicated as the primary predators. | en |
| dc.format.extent | 123 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/20241 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Egg parasitoids and predators of the douglas-fir tussock moth, Orgyia pseudotsugata (Lepidoptera : Lymantriidae), in British Columbia | en_US |
| dc.type | Thesis | en_US |
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