:''In North America, "winter moth" usually denotes the invasive species ''Operophtera brumata'', but may also mean refer to a native species, '' Erannis tiliaria'' (linden looper) or '' Operophtera bruceata'' (bruce spanworm).'' The winter moth (''Operophtera brumata'') is a

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

of the family

Geometridae The geometer moths are moths belonging to the family Geometridae of the insect order Lepidoptera, the moths and butterflies. Their scientific name derives from the Ancient Greek ''geo'' γεω (derivative form of or "the earth"), and ''metro ...

. It is an abundant species of Europe and the Near East and a famous study organism for evaluating insect population dynamics. It is one of very few lepidopterans of temperate regions in which adults are active in late fall and early winter. The adults use

endothermy An endotherm (from Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions inste ...

for movement in these cold temperatures. The female of this species is virtually wingless and cannot fly, but the male is fully winged and flies strongly. After the initial frosts of late fall, the females emerge from their pupa, walk to and up trees, there emitting pheromones in the evening to attract males. Fertilized, she ascends to lay, on average, around 100 eggs. Typically, the larger the female moth is the more eggs she lays. Winter moths are considered an invasive species in North America.

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

, Canada, experienced the first confirmed infestations in the 1930s. It was later accidentally introduced to Oregon in the 1950s and the Vancouver area of British Columbia around 1970. Defoliation by the moth was first noted in eastern states of the United States in the late 1990s, and is now well established in

Massachusetts Massachusetts (Massachusett: ''Muhsachuweesut Massachusett_writing_systems.html" ;"title="nowiki/> məhswatʃəwiːsət.html" ;"title="Massachusett writing systems">məhswatʃəwiːsət">Massachusett writing systems">məhswatʃəwiːsət'' En ...

Rhode Island Rhode Island (, like ''road'') is a state in the New England region of the Northeastern United States. It is the smallest U.S. state by area and the seventh-least populous, with slightly fewer than 1.1 million residents as of 2020, but it ...

New Hampshire New Hampshire is a state in the New England region of the northeastern United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec to the nor ...

and

Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and ...

. Winter moth is confirmed present in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, Washington and

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

. In Massachusetts, the moths have attracted the attention of several media outlets due to the severity of the infestation. Efforts at

biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

are underway.Winter Moth in Massachusetts: History and Biological Control
University of Massachusetts Extension, The Center for Agriculture, Food and the Environment (2017). Accessed Dec 6, 2017.

Description

The forewing ground colour of the winged males varies from grey-yellow to beige-brown or occasionally slightly reddish-tinted. The patterns are often band-shaped dark brownish, often indistinct. The fringe is yellowish. The hindwings are pale grey or yellow grey. The antennae are short and finely hairy. The female appears completely wingless, but in fact female winter moths have greatly reduced wings. The flightless female has a brownish-grey body with rudimentary wing stubs that are brown to grey and have dark bands. Body length for both sexes approximately 1.0 centimeters.Winter Moth Identification & Management
UMass Extension The Center for Agriculture, Food and the Environment (2017) Accessed December 7, 2017. Larvae at hatching are 1/10 inch (2.5 mm) in length and will grow to 3/4 inch (20 mm) over a six-week period.The Relationship Between the Winter Moth (''Operophtera brumata'') and Its Host Plants
O'Donnell KM. University of Maine (2015) In North America, winter moth can be confused with the related native species Bruce spanworm (''Operophtera bruceata''). In fact, the two species hybridize.

Distribution

Native to Northern and Central Europe: In the South, its range extends to Northern

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

; in the East to the

Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia (country), Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range ...

and

Asia Minor Anatolia, tr, Anadolu Yarımadası), and the Anatolian plateau, also known as Asia Minor, is a large peninsula in Western Asia and the westernmost protrusion of the Asian continent. It constitutes the major part of modern-day Turkey. The re ...

; in the North to the Baltic. The genetic populations of winter moth in Europe are a result of recolonization following the last glacial period. As an invasive species, this moth is found in Nova Scotia, coastal New England (Massachusetts, Maine, Rhode Island, Connecticut, and New York) and also the Pacific northwest (mainly Vancouver Island). In New England, expansion inland and north appears to be curtailed by cold winter temperatures, so for example, coastal Maine but not inland. Locally milder winters, as part of global climate change, may be allowing expansion of afflicted territory. A study conducted in Massachusetts documented that winter moth defoliation reduced the annual trunk diameter growth rate of oak trees by an average of 47% while not significantly impacting growth rates of the less defoliated maple trees.

Life cycle

Winter moth larvae ( caterpillars) emerge in early spring from egg masses laid near leaf buds after a series of days in which the daytime high temperatures reach into the 50s Fahrenheit. Recently hatched larvae feed on expanding leaf buds, often after having burrowed inside the bud, and later on foliage, for approximately six weeks. In addition to feeding on the tree where they hatched, young larvae will also product silk strands to 'balloon' (be wind-blown) to other trees. By mid-May the larvae, green in color and about an inch long, descend to the ground. Very little mortality due to disease has been noted in winter moth larvae in North America. Pupation occurs in the soil in late May. Adults emerge from the soil in mid-late November. The female winter moths are flightless but release a sex pheromone to attract males. After mating, the female lays between 150-350 tiny eggs in bark crevices, on branches, in lichen, and under bark scales. With such a long pupal period, winter moth is vulnerable to numerous pupal predators and parasitoids. Research conducted in the Netherlands indicated that as climate warming is causing spring temperatures to become warmer sooner, some of the winter moth eggs were hatching before tree leaf buds - first food for the caterpillars - had begun to open. Early hatchlings starved. Late hatchlings survived. Because hatch timing is genetically controlled, the moths are evolving to resynchronize with bud opening by delaying the response to the temperature trigger by 5 to 10 days.Winter Moth Proves Able To Adjust To Climate Change.
Netherlands Institute of Ecology (2007). The larvae, like the adults, can withstand below freezing temperatures at night. Larval dispersal is the dominant source of density-dependent larval mortality and likely regulates high density population dynamics of winter moth in New England. Larvae prefer Oak and

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

, but also feed on

Maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http ...

Birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains ...

Hornbeam Hornbeams are hardwood trees in the flowering plant genus ''Carpinus'' in the birch family Betulaceae. The 30–40 species occur across much of the temperate regions of the Northern Hemisphere. Origin of names The common English name ''hornbeam ...

, Chestnut, Hazel, Quince, Beech,

Larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains fur ...

, Poplar, Cherry,

Pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the family Rosaceae, bearing the po ...

Rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

, Raspberry, Blueberry,

Willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

Elm Elms are deciduous and semi-deciduous trees comprising the flowering plant genus ''Ulmus'' in the plant family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North ...

, and other leafy trees and shrubs.

Invasive Impact

The winter moth is native to Europe, but invaded the northeast of the United States in the late 1990s. As of 2007, winter moths have spread to coastal Maine, eastern Massachusetts, Rhode Island, southeastern Connecticut, and eastern Long Island. The moths feed on a wide range of

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, ...

leaves, and some conifers. This has caused defoliation of the trees across the states in which the moths live. Between 2003 and 2015 winter moths caused defoliation of forests and shade trees from between 2,266 and 36,360 ha/yr in Massachusetts alone.Elkinton, J. S., Boettner, G. H., and Broadley, H. J.. 2021. Successful biological control of winter moth, ''Operophtera brumata'', in the northeastern United States. ''Ecological Applications'' 31( 5):e02326. 10.1002/eap.2326

Biological control

In Europe, where winter moths are native, two

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

species, a

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

('' Agrypon flaveolatum'') and a fly ('' Cyzenis albicans'') prey on winter moth caterpillars. The wasps insert eggs into the larvae. The flies lay eggs on leaves, which the larvae ingest when eating the leaves. As a

, the wasp was introduced in Canada but is not being pursued in the United States because there is not sufficient evidence that the wasp would not lay eggs in larvae of other moth species. Introduction of ''C. albicans'', which is species-specific to preying on winter moths, has proven successful in strongly reducing, although not entirely eliminating, winter moth infestation in Nova Scotia, Canada. Test introductions were begun in eastern Massachusetts in 2005. This proved successful, so more fly releases have taken place at sites from southeast

Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its capita ...

to coastal

. As moth densities can reach ten million larvae per acre, several years are needed before parasitism by the flies reaches 20-50%. Once this is achieved the winter moth density declines and leaf defoliation is reduced to levels not as harmful to the trees. The delay in establishment is likely the result of heavy mortality from predators and hyperparasitoids on the pupating ''C. albicans''. Management of winter moth in Massachusetts using biological control with ''C. albicans'' is showing positive results. There are different ways to successfully control the winter moth population depending on the time of year. During the late fall and early winter, a dormant oil stray can be used to suffocate the eggs. When the eggs are newly hatched in late March and early April Bt ('' Bacillus thuringiensis'') is a safe and effective way to control caterpillars. As the caterpillars get bigger, spinosad is also effective.

References

External links

UKmoths
Winter Moth ''Operophtera brumata'' (Linnaeus, 1758) *
Lepiforum.de
''many excellent photos'' {{taxonbar, from=Q164002 Operophtera Agricultural pest insects Insect pests of temperate forests Moths described in 1758 Moths of Europe Moths of Iceland Moths of North America Moths of Asia Taxa named by Carl Linnaeus