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Background
Releases and Recoveries
Coleophora serralella (L.). 287
Just before leaf drop they crawl to branch crotches or to the base of leaf buds to
overwinter. In the following spring, after moulting, they feed on developing leaves.
When fully grown, by early summer, they pupate and adults emerge in July.
Species of alder (Alnus spp.) are the main hosts in continental Europe (Gepp 1975a),
but in the British Isles several species of birch are the most severely attacked trees
(Coshan 1974). In North America (Guevremont & Juillet 1974, Bryant & Raske 1975)
white birch is the most severely damaged species, although grey birch, Betula populi/olio
Marsh., may also sustain continuous severe damage. The casebearer may complete its
life cycle on several species of hardwood trees and shrubs, but in North America it is
known to build up high population levels only on white and grey birch (Guevremont &
Juillet 1974, Bryant & Raske 1975).
In North America, the extent of mortality of various life stages has been determined in
Quebec (Guevremont & Juillet 1974) and in Newfoundland (Raske unpublished). Life
tables for the two regions differ substantially. In Quebec, mortality of first- and secondinstar
larvae and pupal parasitism seem to be the most important mortality factors. In
Newfoundland, highly variable egg mortality, from unknown causes, seems to regulate
the population at a chronic high level. This egg mortality (Raske 1974b) has not been
reported on mainland Canada. In fall, early instar larval mortality in Newfoundland is
about 20%. Surviving larvae that overwinter suffer mortality of about 60% annually. In
spring, larval mortality among those remaining is about 80% and pupal mortality is 25%.
Total losses from parasitism of all stages is about 10%.
The parasitoid complex of this casebearer has been studied both in Europe and in
North America where biological control of this pest has been attempted. In its native
Europe, parasitoids are more important in regulating the population of the birch
casebearer (Pschom-Walcher 1969 to 1975, Gepp 1975b, 1975c, Coshan 1974) than in
North America (Guevremont & Juillet 1975, Raske 1978). However, the parasitoid
complexes on the two continents resemble one another. Many genera are native to both
regions: Scambus, ltoplectis, Gelis, Orgilus, Agathis, Habrocytus, Cirrospilus, and
Chrysocharis. The species on each continent differ, except for Habrocytus semotus
(Walker). Apanteles spp. and Campoplex spp. are dominant parasitoids of this casebearer
in Europe, but are virtually absent on it in North America. The main difference between
Quebec and Newfoundland is that Agathis cincta was common in Quebec and absent in
Newfoundland.
Most parasitoid species in North America are parasitic on many lepidopterous insects
and are best considered incidental parasitoids that have adapted to this host.
In 1968 the Canadian Forestry Service, in co-operation with the aBC, initiated a
biological control programme against the birch casebearer in Newfoundland; introductions
of European parasitoids began in 1971 and terminated in 1975 (Raske 1977). Two
species complexes of parasitoids were released: Campoplex (= Porizon) spp. (Hymenoptera:
Ichneumonidae) and Apanteles spp. (Hymenoptera: Braoonidae) (Table 76). The Campoplex
spp. consisted of C. borealis (Zett.) and an undescribed species. The Apanteles complex
included three species: predominantly A. coleophorae (Wilk.) and a few each of A.
mesoxanthus Ruschka and A. corvinus Reinh. Living individuals of neither complex