Satin moth
- French common name: Papillon satiné
- Other common names: White satin moth
- Scientific name: Leucoma salicis (L.)
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Lepidoptera
- Family: Erebidae
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Partial list of synonyms:
- Stilpnotia salicis Linnaeus
General information and importance
Satin moth is an introduced species native to Europe and Asia. When first introduced into Canada, it was generally only a pest of non-native poplar (Populus) and willow (Salix) species. Since its introduction, however, it has reached outbreak population levels on a number of native poplar species in British Columbia, Alberta, Ontario, and eastern Canada. The factors behind the change in behaviour are uncertain.
Distribution and hosts
The first records of the insect in North America are from near Boston, Massachusetts, and southwestern British Columbia, both in 1920. By 1930, it was detected in the Maritime Provinces. The insect is currently found throughout southern and central British Columbia and Alberta, southern and northwestern Ontario, southern Quebec, New Brunswick, Prince Edward Island, Nova Scotia, and the island of Newfoundland. In the United States, the insect is found in both the northeastern and northwestern portions of the country. The insect is native to Europe and Asia.
Satin moth prefers non-native poplar and willow species, and hybrid crosses with the latter species. It also feeds on all native poplars in Canada.
Specific native hosts include: trembling aspen (Populus tremuloides), eastern cottonwood (P. deltoides), black cottonwood (P. trichocarpa), balsam poplar (P. balsamifera), and largetooth aspen (P. grandidentata). Specific introduced hosts include: European white poplar (P. alba), European black poplar (P. nigra), and Lombardy poplar (Populus nigra var. italica).
Tree parts affected
Symptoms and signs
Moths are pure white with a satiny sheen. They have a wingspan of about 35 to 50 millimetres. Although the head, thorax, and abdomen of both the male and female moth are black, they are covered densely with long, satiny-white hairs making them appear white. The eyes, antennae, and legs of moths are black, but the legs appear striped because of tufts of white hair. Mature, full-grown larvae (caterpillars) are about 34 to 50 millimetres long. Eggs are laid on leaves, branches, and trunks. They are deposited in oval masses of 150 to 200 light green eggs in one or two layers. The eggs are covered with a glistening, white secretion. Feeding by newly hatched larvae results in skeletonized leaves. Caterpillars are covered in sparse yellowish-brown hair with black to bluish black heads. The backs of larvae are black with a row of large, regularly spaced white blotches down the middle and a narrow, broken line along each side. Larvae also have a transverse row of prominent reddish-brown tubercles on the top of each body segment. Each tubercle bears a tuft of yellowish-brown hairs. Larvae will often moult on the undersides of branches where their cast skins can be found. The overwintering larvae can be found in bark crevices or under loose bark. Pupae are shiny black, 15 to 20 millimetres long, and sparsely covered with yellowish hairs. The cocoon consists of loosely spun white silk. Cocoons can be found in rolled leaves, attached to twigs, or in bark crevices.
Life cycle
Satin moth has one generation per year. This insect usually overwinters as third instar larvae in sheltered places on the host’s trunk or branches where they spin silken coverings (hibernaculum). Third instar larvae emerge from overwintering sites around mid-May and begin feeding on the developing leaves of the host. Feeding continues until about mid to late June and ends with the larvae becoming mature. Pupation occurs in loosely woven cocoons within rolled leaves, or on twigs or in bark crevices. The adult moths emerge after about 10 to 14 days, typically in early to mid-July. After emergence, adult moths mate, and females lay eggs on leaves, branches, and trunks. Male moths are active fliers, and although females can fly, they rarely do so. About 14 days later, eggs hatch and larvae begin feeding on leaves, resulting in skeletonization. Larvae usually feed for about 2 weeks, and moult twice before overwintering.
Damage
The insect can cause severe defoliation to hybrid poplar and willow. However, high populations only occur for 2 or 3 years before subsiding. Thus, the impact is usually of little consequence. Outbreaks that occur in native aspen and poplar forests are a greater concern. When outbreaks persist over several consecutive years, satin moth defoliation can have a large impact on the growth of affected trees. Some tree mortality can occur when satin moth defoliation is followed by other aspen pests or abiotic factors, such as drought.
In the insect’s native range in Europe and Asia, severe outbreaks occur occasionally in Scandinavia and across the insect’s range south to the Mediterranean region. It is considered one of the more damaging pests in Europe. In China, it is considered a serious pest in poplar plantations.
Prevention and management
Pest management strategies for a particular pest vary depending on several factors. These include:
- the population level of the pest (i.e., how numerous the pest is on the affected host[s]);
- the expected damage or other negative consequences of the pest’s activity (either to the host, property, or the environment);
- an understanding of the pest’s life cycle, its various life stages, and the various natural or abiotic agents that affect population levels;
- how many individual host specimens are affected (an individual tree, small groups of trees, plantations, forests);
- the value of the host(s) versus the costs of pest management approaches; and
- consideration of the various silvicultural, mechanical, chemical, biological, and natural control approaches available and their various advantages and disadvantages.
Decisions about pest management strategies requires information about each of these factors for informed decision-making. These various factors should then be weighed carefully in terms of costs and benefits before action is taken.
In the first few decades after satin moth was detected in Canada, efforts were made to rear and release several European parasites to help manage the insect’s populations through biological control. These included a species of fly, Compsilura concinnata Meig. (Diptera: Tachinidae), and three species of parasitic wasps: Apanteles solitarius (Ratz.) (Hymenoptera: Braconidae), Meteorus versicolor (Wesm.) (Hymenoptera: Braconidae), and Trichomalopsis hemiptera (formerly Eupteromalus nidulans [Thom.]) (Hymenoptera: Pteromalidae). These parasites were released in Newfoundland, New Brunswick, Nova Scotia, and British Columbia. Only the three parasitic wasp species have become established in these provinces and continue to parasitize satin moth. Apanteles solitarius has also spread to Quebec with satin moth.
On smaller ornamental trees, mechanical approaches to insect control are effective for satin moth. Egg masses on leaves, branches, and the trunks can be removed using this method. In the spring, the young larvae can be removed by hand and destroyed. Pressurized water can also be used to dislodge larvae from the foliage. However, if the larvae are not prevented from climbing back up onto the tree, defoliation will likely resume.
If populations warrant control and other methods are unsuitable, insecticides can be applied during the leaf skeletonizing stage in late summer or in the spring when larvae are feeding on emerging, young leaves. Monitoring for the distinctive and conspicuous white moths flying around host trees in July will aid in both the need for and timing of insecticides. A decision on whether a pesticide application might be necessary can be based on high numbers of easily visible egg masses on trees or feeding larvae on leaves. Registered contact or stomach insecticides should be effective. Pesticides registered for use against satin moth under specific situations may change from year to year. Therefore, please search Health Canada’s Pesticide Product Information Database for currently registered pesticides and product information for use against this insect. The application of any registered product should be based on population size and applied only when necessary and against the approved life stage. It is also recommended to consult a local tree care professional. Chemical pesticides may be toxic to humans, animals, birds, fish, and other beneficial insects. Apply registered products only as necessary and according to all directions and precautions noted on the manufacturer’s label. In some jurisdictions and situations, only a licensed professional can apply pesticides. Consulting relevant local authorities to determine local regulations that are in place is recommended.
Photos
A full-grown satin moth larva (dorsal view) on balsam poplar.
Thérèse Arcand
A full-grown satin moth larva (lateral view) on balsam poplar.
Thérèse Arcand
A full-grown satin moth larva on a partially consumed trembling aspen leaf.
Thérèse Arcand
Satin moth egg mass on European white poplar.
Thérèse Arcand
Satin moth egg mass on a willow twig.
Thérèse Arcand
Newly hatched satin moth larvae on a hybrid poplar leaf. The egg mass is visible in the upper part of the photo.
Thérèse Arcand
A young satin moth larva on a willow leaf.
Thérèse Arcand
A full-grown satin moth larva on a trembling aspen leaf.
Thérèse Arcand
Adult satin moth.
Thérèse Arcand
Male and female satin moths mating on a European white poplar leaf.
Thérèse Arcand
Newly emerged satin moth adult next to its pupal case on trembling aspen.
Thérèse Arcand
Two pupae in silken cocoons on trembling aspen.
Thérèse Arcand
Satin moth pupa tied to a European white poplar leaf. Note also the cast skin from the last moult adjacent to the pupa.
Thérèse Arcand
Satin moth pupa tied on a European white poplar leaf.
Jean-Paul Laplante
Adult satin moth (lateral view) at rest on a European white poplar leaf.
Thérèse Arcand
Mature satin moth larva on defoliated European white poplar.
Paul Benoît
Satin moth larvae of various instars on a defoliated branch.
René Martineau
Satin moth pupa suspended with silk from a twig. Note also the cast skin from the last moult adjacent to the pupa.
René Martineau
Balsam poplar severely defoliated by satin moth.
Jean-Pierre Bérubé
Trembling aspen severely defoliated by satin moth.
Robert Blais
Carolina poplar crowns severely defoliated by satin moth.
Pierre Therrien
Aerial view of trembling aspen severely defoliated by satin moth.
Jacques Morissette
Selected references
Avtzis, N.D. 1990. Development of Leucoma salicis (L.) (Lepidoptera: Lymantriidae) on Populus alba (L.) and poplar clone “I-214”. Entomologia Hellenica 8: 25‒27. https://doi.org/10.12681/eh.13977
Brown, F.G. 1968. Pests and diseases of forest plantation trees: an annotated list of the principal species occurring in the British Commonwealth. Clarendon Press, Oxford University Press. London, Great Britain. 1330 p.
Condrashoff, S.F. 1957. Advance of the satin moth, Stilpnotia salicis (L.), into the interior of British Columbia. Entomological Society of British Columbia 53: 26–27.
Forbes, R.S.; Ross, D.A. 1971. Stilpnotia salicis (L.), satin moth (Lepidoptera: Liparidae). Chapter 47. Pages 205–212 in Biological control programmes against insects and weeds in Canada 1959-1968. Commonwealth Agricultural Bureaux. Farnham Royal, England. Technical Communication No. 4.
Humphreys, N. 1996. Satin moth in British Columbia. Natural Resources Canada, Canadian Forest Service, Pacific Region, Pacific Forestry Centre. Victoria, British Columbia. Forest Pest Leaflet 38. https://ostrnrcan-dostrncan.canada.ca/entities/publication/a43b1c98-ba90-4f3a-9cb3-69a7874ef42f?fromSearchPage=true
Langor, D.W. 1995. Satin moth. Natural Resources Canada, Canadian Forest Service, Northwest Region, Northern Forestry Centre. Edmonton, Alberta. Forestry Leaflet 35. https://ostrnrcan-dostrncan.canada.ca/entities/publication/bd1c3a04-2c01-4c3d-9158-b9197c1052dd?fromSearchPage=true
Lejeune, R.R.; Silver, G.T. 1961. Parasites and hyperparasites of the satin month, Stilpnotia salicis Linnaeus, (Lymantriidae) in British Columbia. The Canadian Entomologist 93(6): 456–467. https://doi.org/10.4039/Ent93456-6
MacQuarrie, C.J.K.; Lyons, D.B.; Seehausen, M.L.; Smith, S.S. 2016. A history of biological control in Canadian forests, 1882–2014. The Canadian Entomologist 148(Supplement S1): S239–S269. https://doi.org/10.4039/tce.2015.66
Magasi, L.P.; Van Sickle, G.A. 1984. Leucoma salicis L., satin moth (Lepidoptera: Lymantriidae). Chapter 53. Pages 299–302 in J.S. Kelleher and M.A. Hulme, editors. Biological control programmes against insects and weeds in Canada 1969-1980. Commonwealth Agricultural Bureaux. Farnham Royal, United Kingdom. Page Bros. (Norwich) Ltd.
Reeks, W.A.; Smith, C.C. 1956. The satin moth, Stilpnotia salicis (L.), in the Maritime Provinces and observations on its control by parasites and spraying. The Canadian Entomologist 88(10): 565–579. https://doi.org/10.4039/Ent88565-10
Sun, Y.-X.; Wang, L.; Wei, G.-Q.; Qian, C.; Dai, L.-S.; Sun, Y.; Abbas, M.N.; Zhu, B.-J.; Liu, C.-L. 2016. Characterization of the complete mitochondrial genome of Leucoma salicis (Lepidoptera: Lymantriidae) and comparison with other Lepidopteran insects. Scientific Reports 6:39153. https://doi.org/10.1038/srep39153
USDA Forest Service. 1985. Insects of eastern forests. United States Department of Agriculture, Forest Service. Washington D.C. Miscellaneous Publication No. 1426. 608 p.
Wagner, T.L.; Leonard, D.E. 1979. Aspects of mating, oviposition, and flight in the satin moth, Leucoma salicis (Lepidoptera: Lymantriidae). The Canadian Entomologist 111(7): 833–840. https://doi.org/10.4039/Ent111833-7
Wagner, T.L.; Leonard, D.E. 1979. The effects of parental and progeny diet on development, weight gain, and survival of pre-diapause larvae of the satin moth, Leucoma salicis (Lepidoptera: Lymantriidae). The Canadian Entomologist 111(6): 721–729. https://doi.org/10.4039/Ent111721-6
Wagner, T.L.; Leonard, D.E. 1980. Mortality factors of satin moth, Leucoma salicis [Lep.: Lymantriidae], in aspen forests in Maine. Entomophaga 25: 7–16. https://doi.org/10.1007/BF02377517