Black army cutworm, Actebia fennica
   

Fig. 38   Black army cutworm larva. Note fine double lines along the abdomen.	Fig. 39  Conifer seedling defoliated by black army cutworm.	Fig. 40   Black army cutworm feeding on herbaceous vegetation.	Fig. 41  Current growth of spruce seedling after severe defoliation by black army cutworm the previous year.

Distribution:  Damaging populations have occurred in the central and southeastern interior.

Tree Species Attacked: All conifer seedlings are attacked, most commonly white spruce and lodgepole pine.

Insect Description & Damage Symptoms: Larvae are velvety black on the upper surface, with two pairs of fine, white, double lines running the full length of each side of the body. The underside is grey. The larvae range from about 0.5 cm long during the overwintering stage, to about 4.0 cm when mature in June. Larvae feed during the day in early spring, but switch to night feeding in late spring. Mature larvae pupate in the litter layer in late June. Although larvae prefer to feed on herbaceous plants and shrubs, such as fireweed, they will defoliate coniferous seedlings in the absence of preferred hosts. First evidence of cutworm feeding is "shot holes" in leaves of herbaceous vegetation. Attacked coniferous seedlings may be partially or completely defoliated, buds may be damaged, and succulent young stems may be clipped off. At the beginning of an outbreak, larval feeding is usually clumped in distinct patches measuring a few hundred metres across, usually located on the upper portion of south-facing slopes. Little or no sign of feeding can be seen between patches. Patches enlarge and coalesce as the larvae migrate and consume new plants. Larvae are not normally observed during the day, but can be found buried within the litter or hidden within stalks or unopened leaves of certain plants, such as Indian hellbore. If palatable food becomes scarce or the soil becomes too wet, larvae can be observed on the surface searching for food. 

Damage: Adult moths are attracted to recently burned areas to lay their eggs. Sites burned in early summer the previous year, or in late summer to fall two years previously, are the most attractive. If preferred vegetation is scarce when larvae emerge in the spring, the potential for damage to planted coniferous stock is very high, especially if the cutworm population is high. Severe defoliation may result in seedling mortality or deformity. Although attacks can be devastating locally, this insect seldom causes significant damage for more than one season.

Similar Damage: Death or deformity of seedlings from factors such as frost, incorrect planting, voles, or rhizina root disease, may be confused with black army cutworm, once the needles have fallen off. Evidence of partially chewed needles and the larvae themselves will distinguish the black army cutworm.

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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