Preferred name: Choristoneura fumiferana
Authority: (Clemens)
Taxonomic position: Animalia: Arthropoda: Hexapoda: Insecta: Lepidoptera: Tortricidae
Other scientific names: Archips fumiferana (Clemens), Cacoecia fumiferana (Clemens), Harmologa fumiferana (Clemens), Tortrix fumiferana Clemens
Common names in English: spruce budworm
view more common names online...
Notes on taxonomy and nomenclature EPPO Categorization: A1 list
EU Categorization: A1 Quarantine pest (Annex II A)
view more categorizations online...
EPPO Code: CHONFU

In North America C. fumiferana is a major defoliator of coniferous trees. This pest primarily occurs on Picea and Abies, but has also been recorded on Pseudotsuga, Pinus and occasionally on Tsuga and Larix (Brown et al., 2008). Stand-level defoliation is well described on Abies balsamea, white spruce (Picea glauca) and P. rubens in Eastern North America and A. lasiocarpa, Picea engelmannii, P. glauca and Pseudotsuga menziesii in the West.

Several primary host plants of C. fumiferana are widely grown in European forests and plantations (e.g. Pseudotsuga menziesii, and for Northern Europe Abies lasiocarpa, Picea engelmannii and P. glauca). In addition, growth and development of spruce budworm on Norway spruce (Picea abies) in North American plantations was equivalent to that on white spruce (Berthiaume et al., 2020), highlighting the risks posed to this Norway spruce.

Host list: Abies balsamea, Abies grandis, Abies lasiocarpa, Abies, Juniperus, Larix laricina, Larix, Picea abies, Picea engelmannii, Picea glauca, Picea mariana, Picea rubens, Picea sitchensis, Picea, Pinus contorta, Pinus, Pseudotsuga menziesii, Tsuga heterophylla, Tsuga

C. fumiferana is found throughout coniferous forests in Eastern North America and its distribution extends west through the boreal forest, and as far north as Alaska, Yukon, and the Northwest Territories. Host plant availability and seasonal temperatures determine northern and southern limits of the pest (Régnière et al. 2012, Gray 2008; Marshall & Sinclair 2015; Butterson et al., 2021). Climate change is expected to alter these range limits (Régnière et al., 2012, Candau & Fleming, 2011; Pureswaran et al., 2015), changing the defoliation risk in northern forests that have not historically experienced C. fumiferana outbreaks (Bognounou et al., 2017).

North America: Canada (Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland, Northwest Territories, Nova Scotia, Ontario, Prince Edward Island, Québec, Saskatchewan, Yukon Territory), United States of America (Alaska, Arizona, Idaho, Iowa, Maine, Michigan, Minnesota, Montana, New Hampshire, New York, North Dakota, Ohio, Oregon, Pennsylvania, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin)

C. fumiferana is typically univoltine, with a single generation per year. Adults appear in July or August and mate soon after eclosion. Females lay egg masses on the undersides of needles on their host trees, with up to 20 eggs per mass (Nealis, 2016). Eggs hatch in 8-12 days, and the larvae forgo feeding to seek overwintering locations in bark crevices, under bark scales, lichen mats, or old staminate flower scars (Nealis and Régnière, 2016).  Larvae spin silken structures (=hibernacula) in these sites, molt, and enter diapause (Marshall and Roe, 2020). Larvae remain in diapause until late winter and then enter a period of quiescence and resume development in the spring (Han and Bauce, 1996; Marshall and Roe, 2020). 

Spring temperatures cue larval emergence, and this occurs prior to budburst in its host plants (Nealis and Régnière, 2016; Régnière and Nealis, 2018). Larvae disperse to branch tips to initially mine old needles, unopened buds, or feed upon the early-opening staminate flowers in advance of host budburst. Once vegetative buds begin opening, larvae move to these new buds and begin feeding within a protective silken cover. Larvae typically have six instars and pupate in their feeding webs or within nearby branches. While one generation per year is typical for Choristoneura species, C. fumiferana can have a life cycle which takes two-years to complete or one year (if diapause does not occur) (Harvey 1957, 1961).

For more information on the biology of C. fumiferana refer also to Furniss and Carolin (2002).

Symptoms

In low to moderate population densities, defoliation is restricted to new buds and foliage, especially in the upper crown. Partially consumed needles on the webbed branch tips turn bright reddish-brown by midsummer. At high population densities, host plants can experience severe defoliation, growth reductions and mortality, particularly over successive years (MacLean and Ostaff, 1989). 

Morphology

Eggs

The light-green eggs are oval and laid in overlapping shingles along the underside of needles. Egg masses typically contain 20 eggs (Nealis and Régnière, 2004). 

Larva

Newly hatched larvae are 1-2 mm in length, pale yellow with a dark head capsule. As they feed and moult, larvae become dark-brown with a black head and light dots along their back. 

Pupae

Pupae are dark green and brown, and the sexes can be discriminated by their abdominal morphology (Jennings and Houseweart, 1978). Larvae will pupate in branches near their final feeding structures. 

Adult

Adults are predominantly grey with mottled dark-brown markings; their wingspan is approximately 20 mm.  A rare brown female morph has also been described (Stehr, 1955).

Detection and inspection methods

Visual detection

Eggs are laid on the underside of needles and can be difficult to detect visually. 

Second instar larvae form silken overwintering structures within crevices within branches and the trunk of host plants. While difficult to observe, this stage can be effectively extracted from foliage using a 2% sodium hydroxide wash and counted following separation from plant material with hexane flotation and filtration (Allen et al., 1984). 

Developing larvae of C. fumiferana are found on buds and foliage of coniferous host trees, however they will vacate feeding structures on silken threads when disturbed. Larvae can be identified using available keys and morphological descriptions (Harvey and Stehr, 1967; Lindquist, 1982).

Pheromone traps

Pheromone chemistry is well described for male spruce budworm (Silk et al., 1980) and is commercially available. Pheromone trapping is an important management tool to monitor populations within North America (e.g. Carleton et al., 2020). 

Molecular detection

Molecular identification of specimens from all life stages can be performed using Sanger Sequencing of mitochondrial genes (Lumley and Sperling, 2011). Separation of C. fumiferana is predominantly successful, however some complexity arises where C. fumiferana populations are genetically very close to other members of the budworm complex (see notes on taxonomy and nomenclature). The EPPO-Q-bank database (https://qbank.eppo.int/arthropods/) notes issues in separating C. fumiferana from related North American species. The non-European Choristoneura, as a group, can be reliably detected with the standard DNA barcoding region of mitochondrial DNA. Extensive molecular resources are available for C. fumiferana and related North American species on Genbank and the DNA Barcoding of Life database (www.boldsystems.org).

Extensive dispersal occurs during population outbreaks of C. fumiferana. Adults are strong fliers and can fly 20 km (Greenbank et al., 1980), with mated females showing greater dispersal capacity than virgin females (Elliott and Evenden, 2009). When combined with strong winds, C. fumiferana can disperse over 450 km (Anderson & Sturtevant, 2011). Wind dispersal also occurs in first instar larvae in late summer and second instar larvae during spring emergence, aided by their habit of ballooning on silken threads (Nealis, 2016). 

However, international movement is most likely to occur with diapausing second instar larvae that occur on plants or cut foliage of hosts.

Economic impact

C. fumiferana is one of the most widely distributed forest insects in North America and is a highly destructive pest of spruce-fir forests in the USA and Canada. This species undergoes regionally synchronized population outbreaks (Boulanger et al., 2012) that cause widespread defoliation and tree loss. Outbreaks persist for 10 years or more and recur about every 30 to 40 years (Jardon et al., 2003). At the peak of an outbreak, spruce budworm repeatedly defoliates Abies and Picea, leading to growth reduction and mortality, which negatively impacts the forest industry and forest-dependent communities. During the last major outbreak in the 1970s, spruce budworm damaged more than 50 million hectares of forest.

Control

Spruce budworm populations have been typically managed using approaches aimed at protecting high-value stands (= foliage protection). Foliage protection can be achieved via aerial spraying of Bacillus thuringiensis var. kurstaki (Btk) and tebufenozide, which are ingested control products that target larval Lepidoptera (Fleming and Van Frankenhuyzen, 1992; Cadogan et al., 1998). Recently, proactive ‘early intervention’ strategies are being tested as a means of stopping spruce budworm populations from reaching epidemic levels by focusing aerial spraying on expanding population hotspots (Johns et al., 2019). 

Mating disruption using sex pheromones has been explored extensively for this species (Rhainds et al., 2012). The success of this tool may be limited to low-density populations at the start of an outbreak (Rhainds et al., 2012), however the impact of disruption can be reduced by adult dispersal into the forest stands that are being treated using mating disruption (Régnière et al., 2019).

Spruce budworm populations also have a large range of natural enemies (Fernández-Triana and Huber, 2010) which are considered to be an important source of mortality during development (Royama et al., 2017). Inundative releases of Trichogramma minutum successfully reduce regional larval populations (Smith et al., 1990). The relative role of natural enemies (parasitoids and diseases) and bottom-up effects of host plant and weather on population dynamics is not clear and all likely combine to generate the irruptive, cyclical population behaviour observed in C. fumiferana (Royama et al., 2017).  

Silvicultural methods such as thinning can increase stand resistance to spruce budworm outbreaks (Bauce and Fuentealba, 2013). 

Phytosanitary risk

C. fumiferana has been added to the EPPO A1 List, but is not regarded as a quarantine pest by any other regional plant protection organization. Of the North American Choristoneura species, spruce budworm presents the greatest risk to European forests as it attacks a large number of conifer species and high population densities can lead to tree mortality.

Requiring that plants for planting or cut branches of hosts (including Christmas trees) originate from a pest free area is an appropriate phytosanitary measure (EPPO, 2018). Other risk management options may be relevant, as recommended for similar Lepidoptera, but whether they are appropriate and feasible for the specific host and commodity should be determined (EPPO, 2021). Such measures include growing the plants under complete physical isolation (EPPO, 2016, 2021, 2022). Measures should be combined with requirements to avoid infestation of the consignments during storage and transport (EPPO, 2022). It is noted that plants for planting of some host species from North America are currently prohibited in the EU (EU, 2022).

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EPPO (2021) EPPO Technical Document No. 1082. Pest risk analysis for Orgyia leucostigma. EPPO, Paris. Available at https://gd.eppo.int/taxon/HEMELE/documents

EPPO (2022) EPPO Standards. PM 8/13(1) Acer. Commodity-specific phytosanitary measures. EPPO Bulletin 52(1), 100-110.

EU (2022) Commission Implementing Regulation (EU) 2019/2072 of 28 November 2019 establishing uniform conditions for the implementation of Regulation (EU) 2016/2031 of the European Parliament and the Council, as regards protective measures against pests of plants, and repealing Commission Regulation (EC) No 690/2008 and amending Commission Implementing Regulation (EU) 2018/2019. Consolidated version 32019R2072, 14/07/2022. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32019R2072

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Freeman TN (1967) On coniferophagous species of Choristoneura (Lepidoptera: Tortricidae) in North America: I. Some new forms of Choristoneura allied to C. fumiferana. The Canadian Entomologist 99, 449-455. https://doi.org/10.4039/Ent99449-5

Furniss RL & Carolin VM (2002) Western forest insects, pp. 168-173. Miscellaneous Publication No. 1339. Forest Service, USDA, Washington, USA.

Gray DR (2008) The relationship between climate and outbreak characteristics of the spruce budworm in eastern Canada. Climatic Change 87, 361-383. https://doi.org/10.1007/s10584-007-9317-5

Han E-N & Bauce E (1996) Diapause development of spruce budworm larvae, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), at temperatures favouring post-diapause development. The Canadian Entomologist 128, 167-169.

Harvey GT (1957) The occurrence and nature of diapause-free development in the spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae). Canadian Journal of Zoology 35, 549-572.

Harvey GT (1961) Second diapause in spruce budworm from eastern Canada. The Canadian Entomologist 93, 594-602. https://doi.org/10.4039/Ent93594-7

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CABI and EFSA resources used when preparing this datasheet

CABI Datasheet on Choristoneura fumiferana:  https://www.cabi.org/isc/datasheet/13074

EFSA Pest survey card on non-European Choristoneura: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2019.5671

This datasheet was extensively revised in 2022 by Amanda Roe, Research Scientist with the Canadian Forest Service, Natural Resources Canada. Her valuable contribution is gratefully acknowledged.

EPPO (2024) Choristoneura fumiferana. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2024-04-19)

This datasheet was first published in 1997 in the second edition of 'Quarantine Pests for Europe',  and revised in 2022. It is now maintained in an electronic format in the EPPO Global Database. The sections on 'Identity', ‘Hosts’, and 'Geographical distribution' are automatically updated from the database. For other sections, the date of last revision is indicated on the right.

CABI/EPPO (1997) Quarantine Pests for Europe (2^nd edition). CABI, Wallingford (GB).