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Larch Casebearer

Coleophora laricella[3]

The larch casebearer is a European moth whose tiny caterpillars mine larch needles and carry cases made from hollowed-out needles.[1][2]

Group
Insect
Order
Lepidoptera
Family
Coleophoridae
Sources
3 cited
Updated
2026-10-17
Larch casebearer moth, a tiny narrow-winged moth with long antennae
Larch casebearer moth, a tiny narrow-winged moth with long antennae. (c) Donald Hobern, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Where it lives
  3. Biology
  4. Damage and signs
  5. Health risk
  6. Control
  7. Related profiles
  8. Common questions
  9. Sources

How to identify it

  • Larvae live in cigar-shaped cases the color of a dead needle, made from a mined needle lined with silk; grown larvae are about 6 mm long.[1][2]
  • Adults are small silvery-gray moths with a wingspan of about 8 mm.[1]
  • Damaged needles look bleached or scorched and then turn brown; heavily fed trees look bronzed or burnt reddish-brown by early summer.[1][2]

Where it lives

Introduced from Europe and found near Northampton, Massachusetts, in the late 1800s; it spread through eastern larch forests and was found on western larch in Idaho in 1957.[1][2]

Biology and life cycle

There is one generation a year. Moths lay single eggs on needles in midsummer, and the hatching larvae mine into the needles for several weeks.[1][2]

In fall the larvae build their cases and overwinter attached near buds, then resume feeding in spring 2 to 3 weeks after budbreak and pupate inside their cases.[1][2]

Adults emerge and fly from late June to early July.[1][2]

Damage and signs

  • All North American larches and European larch can be damaged; feeding is heaviest on the new needles in spring.[1][2]
  • Larch can grow new needles, but repeated heavy defoliation slows growth and causes dieback and death; UMass warns of losses after two or more years, while the Forest Service says at least 5 years of severe defoliation are typically needed.[1][2]

Health risk

None to people or pets.[1][2]

Control

Biological control

Parasitoid wasps imported from Europe, mainly Agathis pumila, brought outbreaks under control by the late 1940s in the East and the 1970s in the West, though outbreaks have returned since 2000; birds, spiders and ants also eat it.[1][2]

Pesticides

Because larch tolerates defoliation, sprays are rarely needed; for high-value trees the Forest Service times them shortly after budbreak and advises consulting tree care professionals.[2]

Common questions

Why do my larch needles look bleached in spring?
Larch casebearer feeding is a likely cause; look closely for tiny cigar-shaped cases on the needles.[1][2]
Will larch casebearer kill my larch?
Usually not; larch grows new needles, and trees die mainly after several years of severe defoliation.[1][2]

Sources

  1. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Coleophora laricella (Larch Casebearer).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/coleophora-laricella (accessed 2026-10-16)
  2. USDA Forest Service (Forest Insect & Disease Leaflets), “Larch Casebearer (FIDL 96, FS-1179, revised Aug. 2021).” www.fs.usda.gov/foresthealth/docs/fidls/FIDL-96-LarchCasebearer.pdf (accessed 2026-10-16)
  3. iNaturalist, “Coleophora laricella taxon page (order and family).” www.inaturalist.org/taxa/217344 (accessed 2026-10-06)

Updated 2026-10-17. Built from sourced records. Spot an error? Tell us.