Larch casebearer is a moth that feeds on larch species (Larix) and was probably introduced in Massachusetts on nursery stock from Europe in 1886 (Tunnock & Ryan, 1983; Otvos & Quedau, 1984). The pest spread throughout the range of tamarack (L. laricina), reaching the Great Lakes region in the 1950s and southeastern Manitoba by 1970 (Otvos & Quednau, 1984). An infestation was found on western larch (L. occidentalis) in Idaho in 1957 (Denton, 1979). In western forests, the insect spread rapidly and was soon considered to be the western larch's most serious pest (Denton, 1979). The insect feeds on the internal tissue of tree needles, causing defoliation. Repeated defoliations can kill the tree or stunt it by reducing potential growth by as much as 97% (Tunnock et al., 1969). The larch casebearer favors younger trees growing in the open or along forest edges (Tunnock & Ryan, 1983).
Control of this pest has relied upon environmental factors and parasitoids, both naturally occurring and introduced. Prolonged cold, wet springs with frosts will cause insect mortality. There is an abundance of natural predators and parasitoids of the larch casebearer, but they are not efficient enough to stop outbreaks. Fortunately, a combination of naturally occurring predators and parasitoids and introduced parasitoids has been successful in eastern and central Canada and the northwestern U.S. (Otvos & Quednau, 1984; Graham, 1949; Ryan et al., 1987). Two introduced European parasitoids, Agathis pumila and Chrysocharis laricinellae, have been able to aid in keeping the pest under control in western forests where it causes the most serious damage (Tunnock & Ryan, 1995; Ryan, 1997).
Denton, R. E. 1979. Larch casebearer in western larch forest. United States Department of Agriculture, For. Serv. Gen. Tech. Rep. INT-55. 62 pages.
Graham, A. R. 1949. Developments in the control of the larch casebearer, Coleophora laricella (Hbn.). In 79th Ann. Rep. Entomological Soc. Ontario (1948). pp. 45-50.
Otvos, I. S. and F. W. Quednau. 1984. Coleophora laricella (Hubner), Larch Casebearer (Lepidoptera: Coleophoridae). In J. S. Kelleher and M. A. Hulme (eds.). Biological Control Programmes against Insects and Weeds in Canada 1969-1980, Commonwealth Agricultural Bureaux, England, 1984.
Ryan, R. B., S. Tunnock, and F. W. Ebel. 1987. The larch casebearer in North American. J. For. 85: 33-39.
Ryan, R. B. 1997. Before and after evaluation of biological control of the larch casebearer (Lepidoptera: Coleophoridae) in the Blue Mountains of Oregon and Washington, 1912-1995. Environ. Entomol. 26: 703-715.
Tunnock, S., R. E. Denton, C. E. Carlson and W. W. Janssen. 1969. Larch casebearer and other factors involved with deterioration of western larch stands in northern Idaho. United States Department of Agriculture, Forest Serv. Res. Pap. INT-68. 10 pp.
Tunnock, S. and R. B. Ryan. 1983. "Larch Casebearer in the Western Larch." United States Department of Agriculture, Forest Service. Forest Insect and Disease Leaflet 96, Revised September 1983.
Tunnock, S. and R. B. Ryan. 1995. Larch casebearer in western larch. USDA Forest Service, Forest Insect & Disease Leaflet no. 96. 2 pp.