Larch Casebearer
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Hagle, S.K; S. Tunnock; K.E. Gibson; and C.J. Gilligan. 1987. Field Guide to Diseases and Insect Pests of Idaho and Montana Forests. U.S. Department of Agriculture, Forest Service. State and Private Forestry, Northern Region. Missoula, Montana. Reprint 1990. Publication Number R1-89-54.
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Contents |
Hosts
Western larch.
Distribution
Wherever larch is found in Idaho and Montana.
Damage
Spring larvae can completely defoliate trees. Defoliated trees can put out another flush of needles, but these may be destroyed by summer larvae. Continued heavy defoliation causes growth loss, branch dieback, and gradual tree death.
Identification
The tips of mined needles in the spring are straw colored, have a hole in them, and curl over or look wilted (fig. 118). Cases, made from hollowed needle segment, containing larvae may be found on needles or twigs from end of August through following June (fig. 120). Cases are straw-colored and rectangular, becoming light gray and cigar-shaped during pupation. They are less than one-fourth inch long. In June, when defoliated trees are disturbed, clouds of small, silvery moths will arise. Eggs are laid singly on needles from late May to early July. Hatching larvae bore into and mine needles.
Similar damages
Larch casebearer damage is most often confused with that of larch needle cast or larch needle blight. Larch sawfly damage is similar from a distance but chewed needles distinguish this damage. Look for distinctive "cases" to identify casebearer.
References
- Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv.,Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.
- Furniss, R. L., and V. M. Carolin. 1977. Western For. Insects. USDA Forest Serv., Misc. pub. 1339, 654 p., illus.
- Tunnock, S., and R. B. Ryan. 1985. Larch casebearer in western larch USDA For. Serv., For. Ins. & Dis. Leaflet 96, 7 p., illus.
