Larch casebearer, Coleophora laricella
     

Fig. 27   Mined needles and cigar-shaped case of mature larch casebearer larvae.	Fig. 28  Straw-coloured foliage of larch attacked by larch casebearer	Fig. 29   Defoliation of new foliage by larch casebearer larva.	Fig. 30  Rectangular case of immature larch casebearer

Distribution:  Southeastern B.C. form the Okanagan Valley east to the Crwosnest Pass and north to Vernon. Defoliation is more common at lower elevations.

Tree Species Attacked: All ages of western larch are attacked.

Insect Description & Damage Symptoms: Mature larvae are 0.5 cm long and are dark reddish-brown with a black head. Young larvae mine a single needle and fabricate a hollow shelter, called a "case", from a section of the needle. This case is straw-coloured and rectangular, becoming grey and cigar-shaped prior to pupation. Larvae move about and feed on needles while enclosed in the case. By fall, the larvae fasten the case to twigs or a needle fascicle to overwinter. Foliage damage is most visible in May when late-instar larvae are feeding on new foliage. The larvae pupates in late May or early June, still staying within the case.

The new foliage of lightly attacked larch turns light green to straw-coloured and will curl at the end. A severe attack will produce reddish needles, which create a scorched appearance. Defoliation is usually lightest in the lower crown and increases with height. Late-instar larvae feeding in the spring are responsible for the majority of damage. In severe attacks, foliage may be consumed as fast as it is produced. Trees often flush again in June if defoliated in May.

Damage: Larch are relatively resistant to the effects of defoliation. However, after five years of severe defoliation, annual terminal and radial growth may be seriously affected.

Similar Damage: Larch casebearer damage is often confused with larch needle cast or larch needle blight. Larch sawfly and bud moth damage is similar from a distance, but chewed needles distinguish this damage. Look for the distinctive cases to identify the larch casebearer.

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Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated March 04, 2002