Satin Moth, Leucoma salicis
 

Fig. 331   Adult satin moth and larva.	Fig. 332  Satin moth larva.	Fig. 333  Severe defoliation caused by satin moth.
Fig. 334  Satin moth egg mass. Note white secretion was removed to expose the eggs.	Fig. 335  Satin moth larva and feeding damage.

Distribution:  The satin moth was introduced into North America from Europe.  It was first detected in B.C. in 1920, and is now found on Vancouver Island, in the Fraser Valley, and throughout the southern and central interior of B.C. (Vancouver, Kamloops, Nelson, Cariboo, and Prince George Forest Regions).

TREE SPECIES ATTACKED: Black cottonwood, hybrid poplars, and trembling aspen are attacked. The satin moth also feeds on willow.

WHAT TO LOOK FOR: Caterpillars with characteristic yellowish blotches and lines, and rows of tufted brownish setae; cast skins on the underside of branches, rolled leaves containing pupae, and silk webbing on stems and branches.

INSECT DESCRIPTION & DAMAGE SYMPTOMS: Larvae are 3.5 to 4.5 cm long when fully grown, and are pale to medium grey-brown, with a darker head and back. They have one row of large, oblong, double, shiny yellowish blotches along the middle of the dorsal surface and two subdorsal, broken, yellowish lines. They also have two lateral and two subdorsal rows of tufted brownish setae. Adults are large silvery white moths with a dark body showing through the hairs. They have a wingspan of 3.0 to 5.0 cm. Overwintered larvae emerge and begin feeding in late April. Damage is most conspicuous in June when late instar larvae consume whole new leaves, except the petioles and major veins. Larvae molt on the underside of branches, and cast skins are conspicuous there. Pupae are found in loosely woven silken cocoons in rolled leaves, on twigs, or in bark crevices. Adults emerge in July, and flat light green eggs are laid in masses with a whitish secretion from early July to late August on leaves, twigs, branches, and trunks of host trees, or indiscriminately on other objects. Larvae emerge in about two weeks. First and second instar larvae skeletonize foliage for about two weeks in late summer, and in severe infestations, leaves turn brown and drop. 

DAMAGE: Satin moth infestations often occur together with infestations of other defoliators, such as tent caterpillars (Malacosoma spp.). Satin moths can completely defoliate trees, and repeated severe defoliation can result in reduced radial growth, top-kill and tree mortality.

SIMILAR DAMAGE: Damage is similar to that caused by other skeletonizing moth or sawfly larvae. Rolled leaves containing pupae and silk webbing on stems and branches are characteristic of the satin moth.

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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