Rusty tussock moth
- French common name: Chenille à houppes rousses
- Other common names: European tussock moth, common vapourer, antique tussock moth
- Scientific name: Orgyia antiqua (L.)
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Lepidoptera
- Family: Erebidae
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Partial list of synonyms:
- Bombyx antiqua L.
- Notolophus antiqua L.
- Orgyia badia Henry Edwards
- Phalaena antiqua L.
General information and importance
Rusty tussock moth is native to Europe but is now established throughout the northern hemisphere. It has been recorded in many parts of Canada since the late 19th century. In the United Kingdom, it is called the vapourer moth because female moths attract males from considerable distances by releasing a pheromone (a vapour trail).
Rusty tussock moth is a generalist defoliator feeding on more than 50 species of coniferous and hardwood tree species. Its broad diet and wide distribution, as well as conspicuous appearance, make the rusty tussock moth a notable insect in a variety of urban and rural habitats with diverse plants. It has been more commonly reported in moist, maritime climates than in drier continental areas. Occasionally, rusty tussock moth becomes common enough to damage fruit trees and bushes, but this damage is usually isolated and short-lived.
The rusty tussock moth is sometimes confused with two native forest insects: Douglas-fir tussock moth or white-marked tussock moth. These three species are closely related and share many characteristics including a spectacularly coloured, hairy caterpillar stage and a flightless female moth. Male rusty tussock moths are strong fliers and are attracted to the same pheromone lure used to trap Douglas-fir tussock moth.
Distribution and hosts
The rusty tussock moth is introduced to North America and now established across Canada and south to the mid-Atlantic states and northern California in coastal, montane and mixed temperate forests. Rusty tussock moth feeds on most common hardwood and coniferous tree species including alder (Alnus), birch (Betula), willow (Salix), oak (Quercus), poplar (Populus), Sitka spruce (Picea sitchensis), and Douglas-fir (Pseudotsuga), as well as associated understory plants such as blueberry (Vaccinium). Its broad host range allows it to thrive in heathlands and feed on ornamental urban plants.
Tree parts affected
Damage occurs on the foliage of many coniferous and broadleaf trees and shrubs. At high densities, soft bark of twigs may also be damaged.
Symptoms and signs
The large larvae of rusty tussock reach 30 millimetres in length and are striking in appearance with four dense, white to yellowish tufts of hairs on the middle of their backs and long white hairs radiating from orange tubercles on the rest of the body. Two long, black pencil-shaped tufts project forward over their black heads and another long tuft projects backwards from the rear of the abdomen. They pupate within a loose silken cocoon. Female adult moths appear wingless but have reduced, vestigial wings. Males have rusty, red-orange wings with a white spot at the middle back of the forewing and a wingspan of 30 millimetres. Males also have large, plumose antennae. Eggs are laid in a loose cluster. Unlike many other tussock moths, these eggs are not protected by hairs or secretions.
Damage appears in early summer as holes and ragged-edged leaves on broadleaf plants and clipped needles on coniferous plants. Damage is usually more prevalent at the top of the tree and at branch tips.
Life cycle
The rusty tussock moth has one generation per year in Canada, although at least a partial second generation has been reported in other areas. It overwinters as an egg. Larvae emerge in late spring and disperse to nearby plants, often ballooning on silk threads throughout the habitat. Once settled, they feed throughout the summer months. They pupate in a silken cocoon at the end of the feeding period in late July to early August. Adults emerge within two weeks. The flightless female attracts male moths with a pheromone. Mated female moths lay hundreds of eggs in a loose cluster.
Damage
Rusty tussock moth rarely causes significant damage to plants. Nonetheless, it can feed on many different plants and live in open, cultivated habitats so that occasional damage to fruit, amenity, or nursery trees may occur. When populations do become high, they are localized and short-lived. Damaged plants usually recover.
As with other tussock moths, some people have allergic reactions to the urticating hairs of the larvae (tussockosis).
Prevention and management
Pest management strategies for a particular pest vary depending on several factors. These include:
- the population level of the pest (how numerous the pest is on the affected host[s]);
- the expected damage or other negative consequences of the pest’s activity and population level (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 require 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 against any particular pest.
The sporadic and short-term nature of infestations makes it difficult to forecast damage and effective intervention. Fortunately, the low level of damage sustained during infestations normally does not require action. Pheromone traps may be used to monitor population levels, followed by searches for eggs to attain more precise information on location and density of populations. Mass trapping with pheromone traps has been considered.
Pheromones and insecticides are defined as pest control products and are regulated in Canada. Products registered for use against rusty tussock moth under specific situations may change from year to year. Therefore, please search Health Canada’s Pesticide Product Information Database for currently registered products 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. Pesticides may be toxic to humans, animals, birds, fish, and other beneficial insects. Apply registered products only as necessary and follow 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
Larvae
Connecticut Agricultural Experiment Station Archives, Connecticut Agricultural Experiment Station, www.forestryimages.org
Larvae
Jerald E. Dewey, USDA Forest Service, www.forestryimages.org
Male
USDA Forest Service Archives, USDA Forest Service, www.forestryimages.org
Larvae
USDA Forest Service Archives, USDA Forest Service, www.forestryimages.org
Selected references
Geistlinger, N.J. 1964. Rusty tussock moth in interior British Columbia, 1963. Department of Forestry, Forest Entomology and Pathology Branch. Ottawa, Ontario. Bi-Monthly Progress Report 20(5): 4.
Grant, G.G.; Frech, D. 1980. Disruption of pheromone communication of the rusty tussock moth, Orgyia antiqua (Lepidoptera: Lymantriidae), with (Z)-6-heneicosen-11-one. The Canadian Entomologist 112(2): 221–222. https://doi.org/10.4039/Ent112221-2
Hardy, G.A. 1945. Notes on the life history of the vapourer moth (Notolophus antiqua badia) on Vancouver Island (Lepidoptera, Liparidae). Journal of the Entomological Society of British Columbia 42: 3–6. https://journal.entsocbc.ca/index.php/journal/article/view/747/755 [Accessed April 2024]
Pacific Northwest Moths. 2022. Orgyia antiqua, (Linnaeus, 1758). http://pnwmoths.biol.wwu.edu/browse/family-erebidae/subfamily-lymantriinae/tribe-orgyiini/orgyia/orgyia-antiqua/ [Accessed January 2024]
University of California Agriculture and Natural Resources. 2018. Tussock moths—Orygia spp. http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/westtussmth.html [Accessed January 2024]
Van Hezewijk, B.; MacLean, J.; McMahon, R. 2018. Identifying larval stages of Orgyia antiqua (Lepidoptera: Erebidae) from British Columbia, Canada. Journal of the Entomological Society of British Columbia 115: 104–109. https://journal.entsocbc.ca/index.php/journal/article/view/1004 [Accessed January 2024]