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LARCH CASEBEARER Coleophora laricella (Hübner) --
Coleophoridae (Contacts) ----- CLICK on Photo to enlarge &
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The casebearer has one generation per year. The adults begin appearing in late May and
lay eggs on either side of the needles.
The larvae hatch and burrow directly down into the needles. In the late summer the larvae emerge from
the mined needles and form overwintering cases. They feed for a while and then move to branches and twigs to
pass the winter. In the early spring
the larvae with their cases move and begin feeding on the young buds and
foliage. Pupation occurs within the
enlarge case, which is commonly attached to a branch on a leaf whorl. The larval feeding, when extensive, causes
a loss of growth that is its greatest impact on larch (Ryan et al. 1987). A biological
control program began in 1928 in western Canada with a request to the Farnham
House Laboratory of CIBC for information on the parasitoid complex of the
casebearer in Europe (McGugan & Coppel 1962). Importation and field releases of 5 species of parasitoids
occurred in eastern Canada between 1931 and 1939 as follows: 1,037 Agathis
pumila (Ratz.)--Braconidae,
29,664 Chrysocharis laricinellae
(Ratz.)--Eulophidae, 506 Cirrospilus
pictus (Nees)--Eulophidae,
3,283 Dicladocerus westwoodii Steph.--Eulophidae,
and 97 Diadegma laricinellum
(Strobl)--Ichneumonidae (Clausen 1978).
All species were subsequently recovered at release sites in Ontario
but only two became well established and spread rapidly, A. pumila
and C. laricinellae.
Between 1942 and 1947 large scale redistribution releases were made at
a number of sites in eastern Canada.
The parasitoids were obtained at established colony sites at Millbridge,
Ontario (Clausen 1978). By 1948
populations of the casebearer were low on the original release sites. The parasitoids followed the spread of the
casebearer to the west assisted by occasional releases (Ryan et al. 1987). This is definitely an example of a
successful biological control program (Webb & Quednau 1971). A separate,
extensive parasitoid importation program was also conducted between 1932 and
1936 in the eastern United States in New England and New York (Clausen
1978). Four of the same parasitoids
as released in Canada were used in the U.S. (Clausen 1978) as follows: 8,141 A.
pumila, 24,671 C. laricinellae, 231 D.
westwoodii, and 3,580 D. laricinellum (Strobl).
Although there is little information, the results were apparently the
same in the eastern United States with the establishment of A. pumila and C.
laricinellae followed by
high parasitization rates particularly by A.
pumila (Dowden 1962). Releases of the two established
parasitoids were also made in 1937, 1950 and 1952 in Michigan and Wisconsin. In the western
United States, the first releases of A.
pumila were made in 1960
with 2,360 adult parasitoids that were collected in Rhode Island (Clausen
1978). These were released at 5
locations in Idaho. Recoveries were
made at 3 sites in 1962. Between 1964
and 1969 field rearing of A.
pumila in whole tree cloth
cages permitted the release of this parasitoid at 400 sites in Idaho,
Montana, Washington and British Columbia (Ryan et al. 1987). The parasitoid became established and
built up at some sites but at other sites it either didn't become established
or it didn't build up. In addition,
significant defoliation still occurred throughout much of the area by 1970
and the program was rated as a failure (Turnock et al. 1976, Ryan et al.
1987). Between 1971 and
1983 a new strategy was used as C.
laricinellae and five other
species of parasitoids from Europe and Japan were released over a period of
several years. C. laricinellae
became widely established but the other species don't appear to be very
important for control of the casebearer though isolated recoveries have been
made (Ryan et al. 1987). In an effort
to properly evaluate the effect of the parasitoids, the larch casebearer was
sampled at sites in Oregon where the casebearer had recently invaded. The populations were followed to the point
of severe defoliation from 1972 to 1978 and then parasitoids were released
between 1979 and 1985 (Ryan 1983, 1986; Ryan et al. 1987). The first parasitoid to be released was C. laricinellae followed by A. pumila. Parasitoids increased and the casebearer
steadily declined and this trend has continued in all plots through 1987 (R.
B. Ryan, personal communication).
Although the prospects are good for a complete success, Ryan et al. (1987)
feel it is too soon to make the claim. In British Columbia
the larch casebearer biological control program was reviewed in 1974 due to
the successes in eastern Canada (Otvos & Quednau 1981). Four parasitoids have been released: A.
pumila, C. larcinellae,
Diadegma laricinellum, and Dicladocerus japonicus Yshm. The story is much the same as with the
other release programs--A. pumila and C. laricinellae
have become well established and the other two have not been recovered. It is too early to evaluate the effects of
the two parasitoids but C. laricinellae is fairly common
in British Columbia and may be responsible for the reduction of larch
casebearer and less tree mortality (Otvos & Quednau 1981). The larch
casebearer is a successful biological control program in eastern Canada and
may shortly be successful in the northwestern United States. It is an example of a classic introduction
program with the subsequent redistribution of the parasitoids from areas of
establishment to new areas. It is
interesting because the two parasitoids complement one another in their
action against the casebearer. Agathis is extrinsically
superior at low host densities and Chrysocharis
is effective at high host densities.
Quednau (1970) hypothesized that Agathis
can only give partial control on its own and that success is only possible
through cooperative interaction with Chrysocharis. Ryan (1985) hypothesized that Agathis may not be detected in
successive samples since parasitized larvae commonly descend to understory
vegetation. Samples could be biased toward
Chrysocharis due to the
absence of Agathis in the
foliate that is sampled. There has
been no success in establishing other parasitoid species. This program also is an example of one
where there was a rigorous attempt to evaluate efficacy of the parasitoids
(Ryan 1986, Ryan et al. 1987). For further details
on biological control effort and biologies of host and natural enemies,
please also see the following (Herrick 1912, Thorpe 1933, Graham 1944, 1949,
1958; Turnbull & Chant 1961, Dowden 1962). REFERENCES: [Additional references may be found at: MELVYL
Library ] Clausen, C. P. 1978. Coleophoridae. In: C. P. Clausen (ed.), Introduced parasites and
predators of arthropod pests and weeds:
a world review. U. S. Dept.
Agric. Handbook No. 480. 545 p. Denton, R. E. 1958. The larch casebearer in Idaho--a new
defoliator for western forests. USDA,
Forest Service, Intermountain Forest and Range Experiment Station, Res. Note
51: 6 p. Dowden, P. B. 1962. Parasites and predators of forest insects
liberated in the United States through 1960.
U. S. Dept. Agric. Agric. Handb. 226.
70 p. Graham, A. R. 1944. The establishment of some imported parasites
of the larch casebearer, Haplotilia
laricella Hbn. in
Ontario. Ent. Soc. Ontario 74th Ann.
Rept. 1943: 48-52. Graham, A. R. 1949. Developments in the control of the larch
casebearer, Coleophora laricella (Hbn.). Ent. Soc. Ontario 79th Ann. Rept.
1948: 45-50. Graham, A. R. 1958. Effectiveness of two introduced parasites
of the larch casebearer, Coleophora
laricella (Hbn.)
(Lepidoptera: Coleophoridae) in Ontario.
Ent. Soc. Ontario 88th Ann. Rept. 1957: 37-41. Herrick, G. W. 1912. The larch case-bearer. New York Agric. Expt. Sta. Bull.
322: 29-54. Jagsch, A.
1973. Populationdynamik und
Parasitenkomplex der Larchenminiermotte, Coleophora
laricella Hbn., in
naturlichen Verbreitungsgebiet der Europaischen Larche, Larix decidua
Mill. Zeit. ang. Ent. 73: 1-42. McGugan, B. M. & H. C. Coppel. 1962. A review of the
biological control attempts against insects and weeds in Canada. II.
Biological control of forest insects, 1910-1958. Commonwealth Inst. Biol. Control Tech.
Comm. No. 2: 35-216. Otvos, I. S. & F. W. Quednau. 1981. Chapter 49. Coleophorea
laricella (Hübner), larch
casebearer (Lepidoptera: Coleophoridae), p. 281-84. In: J. S. Kelleher & M. A. Hulme (eds.),
Biological Control Programmes Against Insects and Weeds in Canada, 1969-1980. Commonwealth Agricultural Bureau, London,
England. 410 p. Ryan, R. B. 1983. Population density and dynamics of larch
casebearer (Lepidoptera: Coleophoridae) in the Blue Mountains of Oregon and
Washington before the build-up of exotic parasites. Canad. Ent. 115:
1095-1102. Ryan, R. B. 1985. A hypothesis for decreasing parasitization
of larch casebearer (Lepidoptera: Coleophoridae) on larch foliage by Agathis pumila. Canad.
Ent. 117: 1573-74. Ryan, R. B. 1986. Analysis of life tables for the larch
casebearer (Lepidoptera: Coleophoreidae) in Oregon. Canad. Ent. 118:
1255-63. Ryan, R. B. 1987. Classical biological control: an overview. J. Forestry 85(7):
29-31. Ryan, R. B., S. Tunnock & F. W. Ebel. 1987.
The larch casebearer in North America. J. Forestry 83(7):
33-39. Thorpe, W. H. 1933. Notes on the natural control of Coleophora laricella, the larch case-bearer. Bull. Ent. Res. 24: 271-91. Turnbull, A. L. & D. A. Chant. 1961. The practice and
theory of biological control of insects in Canada. Canad. J. Zool. 39:
697-753. Turnock, W. J., K. L. Taylor, D. Schroder & D. L.
Dahlsten. 1976. Biological control of pests of coniferous
forests, p. 289-311. In: C. B. Huffaker & P. S. Messenger (eds.), Theory and
Practice of Biological Control.
Academic Press, New York. 788 p. Webb, F. E., & F. W. Quednau. 1971. Chapter 38. Coleophora
laricella (Hübner), larch
casebearer (Lepidoptera: Coleophoridae), p. 131-36. In: Biological Control Programmes Against
Insects and Weeds in Canada, 1959-1968.
CAB, Commonwealth Inst. of Biol. Control, Tech. Comm. No. 4. 266 p. |
