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Pest Status
Background
Releases and Recoveries
AgaIhis pumila (Ratz.)
(Hymenoptera:
Braconidae)
Chapter 49
Coleophora laricella (Hiibner), Larch
Casebearer (Lepidoptera: Coleophoridae)
I.S. OTVOS and F. W. QUEDNAU
The larch casebearer. Coleophora laricella (Hubner). was accidentally introduced from
Europe, probably on nursery stock. It was first recorded in North America in 1886 at
Northampton, Massachusetts (Herrick 1912), and in Ottawa in 1905 (Retcher 1906).
The casebearer spread rapidly and by 1947 infested most tamarack, Larix laricina (Du
Roi) K. Koch, in Newfoundland. the Maritimes. and Ontario. spreading west as far as
Thunder Bay (McGugan & Coppel 1962). By 1970 it was present in southeastern
Manitoba. It was first found on western larch. Larix occidentalis Nutt .• around St.
Maries, Idaho, in 1957 (Denton 1958). and in British Columbia in 1966 (Molnar et al.
1966). The larch casebearer moved rapidly along major larch stands in the valleys, and
became established throughout the range of western larch in southeastern British
Columbia in varying degrees of infestation. Successive years of severe defoliation cause
growth reduction. crown dieback. and subsequent tree mortality (McGugan & Coppel
1962. Turnock et al. 1969).
Successful control of the larch casebearer in eastern and central Canada (Webb &
Quednau 1971) by the introduction of parasitoids and by similar biological control work
in the northwestern United States (Denton 1972. Ryan & Denton 1973) led to a resumption
of the use of parasitoids in 1974 to combat the larch case bearer in British Columbia.
An intensive survey of larch casebearer parasitoids conducted in British Columbia in
1973 yielded 32 species of Hymenoptera (Miller & Finlayson 1974). In Quebec, studies
on Diadegma laricinellum (Strobl) were continued after 1968, but the project was
terminated in 1974 because of low priority.
Four species of parasitoids. Agathis pumila (Ratz.), Chrysocharis laricinellae (Ratz.).
Diadegma laricinellum (Strobl). and Dicladocerus japonicus Yshm. have been released
in southeastern British Columbia. and a few D. laricinellum were also liberated in
Quebec. The details of these releases are summarized in Table 75.
This species was first introduced into British Columbia in 1969 when parasitized larch
casebearers. collected in Montana (USA) were placed in larch casebearer infested
stands at Arrow Creek and Fruitvale. The species was recovered in 1972 at both sites.
Between 1974 and 1977 more adults of A. pumila, this time from Europe. were released
at other locations in the southeastern part of the province. In addition, larch casebearer
larvae parasitized by A. pumila in the laboratory were placed in infested larch stands.
and parasitoids from an old larch case bearer infestation in British Columbia were also
relocated.
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