Preferred name: Gilpinia hercyniae
Authority: (Hartig)
Taxonomic position: Animalia: Arthropoda: Hexapoda: Insecta: Hymenoptera: Diprionidae
Other scientific names: Diprion hercyniae Hartig, Diprion polytoma Hartig, Gilpinia polytoma auctorum, Lophyrus hercyniae Hartig, Lophyrus polytomos
Common names in English: European spruce sawfly
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Notes on taxonomy and nomenclature EU Categorization: PZ Quarantine pest (Annex III)
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EPPO Code: GILPPO

The insect occurs primarily on spruce (Picea) species such as P. abies, P. glauca, P. mariana, P. pungens, P. rubens, and P. sitchensis. On rare occasions, larvae have been observed feeding on species of fir (Abies) when spruce foliage is limiting during outbreaks (Browne, 1968; Schedl, 1975).

Host list: Abies alba, Abies balsamea, Picea abies, Picea glauca, Picea jezoensis subsp. hondoensis, Picea mariana, Picea obovata, Picea omorika, Picea pungens, Picea rubens, Picea sitchensis

In addition to the published records, several additional North American field-collected specimens of G. hercyniae have been documented in university and government insect collections in both Canada and the United States, as well as verified from photographs submitted to BugGuide.net and iNaturalist.org by Dr. David R. Smith, a world sawfly expert. These locations include the Canadian province of Alberta, and the US states of Georgia, Iowa, Maryland, Michigan, Minnesota, North Carolina, Ohio, Pennsylvania, Tennessee, and West Virginia. There was also a published report of G. hercyniae from the Canadian province of British Columbia (Langor et al., 2014), but that particular specimen cannot be found for verification.

EPPO Region: Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France (mainland), Germany, Hungary, Italy (mainland), Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Romania, Russia (Central Russia, Eastern Siberia, Far East, Northern Russia, Southern Russia, Western Siberia), Slovakia, Sweden, Switzerland, United Kingdom (England, Wales)
Asia: Japan, Korea Dem. People's Republic, Korea, Republic, Mongolia, Pakistan
North America: Canada (Manitoba, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, Québec), United States of America (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Vermont, Washington, Wisconsin)

An annotated bibliography of the literature dealing with G. hercyniae up to 1979 was published by Adams and Entwistle (1981). G. hercyniae overwinters as a prepupa (eonymph 6th) in a cocoon that it spins on the forest floor under leaf litter or moss. Pupation starts in early spring with adults emerging in early summer. Depending on the length of the summer season and temperatures, there are usually one or two generations per year; however, three generations have been recorded in the southern part of the insect’s range (MacAloney, 1936; Balch, 1939; Prebble, 1941). The sex ratio is highly female biased at about 1 male to 1200 females (Balch, 1939). The species is mainly parthenogenetic, producing diploid females from unfertilized eggs (thelytoky) (Balch et al., 1941; Smith, 1941). Adults are strong flyers (Balch, 1939). Females start ovipositing soon after emergence and usually lay 30–60 eggs (Prebble, 1941; Thalenhorst, 1968). Eggs are inserted singly in old needles via a slit which is cut in the needle using the ovipositor. Eggs hatch in approximately 10 days (Balch, 1939). Larvae feed singly and mostly on 1–3-year-old foliage (Jensen 1988). New foliage may be avoided by first-generation larvae because of high levels of some secondary compounds (Jensen, 1988). Second and third generation larvae may feed on old as well as current-year needles, especially in white spruce (Picea glauca) (Balch, 1939). Larvae pass through six instars in about one month (MacAloney, 1936). The sixth instar does not feed, but instead drops to the forest floor (MacAloney, 1936; Balch, 1939). Depending on local conditions, pupation may be completed in 2-4 weeks with new adults beginning the next generation while other prepupae undergo diapause. Some individuals remain in extended diapause for as many as 6 years, although 2-3 years is more common (MacAloney, 1936; Balch, 1939).

Signs and Symptoms

Larval feeding occurs first on older needles, usually starting at the tip. Larval fecal pellets (frass) often accumulate on foliage and on the forest floor beneath infested trees. The individual fecal pellets of older larvae are about 2 x 1 mm in size, green at first but turning reddish brown with age (Morris, 1942). Larval life stages of G. hercyniae are found most often during the summer months, especially fourth and fifth instars that have a brownish head capsule, green body, and five white longitudinal stripes (Wilson, 1977).

Morphology

Eggs

The eggs are pale green, elongate oval, and about 1.9 mm long and 0.5 mm wide (Billany, 1978). Eggs are inserted near the center of a needle, one egg per needle. Females oviposit throughout the crown, selecting mostly 1-year-old needles for oviposition (Balch, 1939; Billany et al., 1978). There is a distinct bulge in the needle where the egg is inserted.

Larva

There are six larval instars: the first five instars actively feed whereas the sixth is nonfeeding and spins a cocoon. Larval length increases from about 3 mm in first instars to about 15-20 mm in fifth and sixth instars (Lorenz & Kraus, 1957; Wong & Szlabey, 1986). First to third instar larvae are green and lack longitudinal stripes. Fourth and fifth instars have five white longitudinal stripes along their abdomen. The sixth instar lacks stripes. Abdominal prolegs are found on segments 2-8 and 10. The three pairs of thoracic legs are brown to black. Spiracles are light brown. The head capsule is mainly black in first instars, brownish in second to fifth instars, and green in sixth instars. Head capsules have a dark triangular patch (Wong & Szlabey, 1986). Keys to larvae of Gilpinia species are available for Europe (Benes & Kristek, 1979) and North America (Wong & Szlabey, 1986)

Pupa

The cocoon is spun in the leaf litter layer by the 6^th instar larva. The cocoon is finely textured, reddish brown, cylindrical with rounded ends, 8-9 mm long and 4 mm wide (Billany, 1978).

Adult

Reeks (1941) separated G. hercyniae from G. polytoma based on morphological differences of the genitalia. Additional characters of the head and antenna were used by Goulet (1981) to separate these two species. Adult G. hercyniae females are stout-bodied, 6.0-9.5 mm long, with serrate antennae. Head and body are black with many yellow markings and bands as described in Reeks (1941), Benson (1951), and Billany (1978). Adult males are 4.0-8.5 mm long, with pectinate antennae, and are mostly black on the upper thorax and abdomen with yellow lateral markings as described in Reeks (1941) and Benson (1951).

Detection and inspection methods

Larvae and adults of G. hercyniae are the life stages which are most likely to be found in the field. However, at low populations, detection is difficult because larvae feed singly on older needles and adult females often oviposit in the upper crown. Larvae can be collected by beating the branches over a sheet or tray (Martineau, 1943; Thalenhorst, 1960; Neilson & Morris, 1964). Techniques such as collecting frass as it falls to the ground from infested trees or collecting sawfly cocoons on the forest floor have been used to monitor G. hercyniae population fluctuations (Martineau, 1943; Prebble, 1943; Morris, 1949). During outbreaks, the degree of defoliation can be estimated at the tree and stand level (Martineau, 1943).

G. hercyniae adults are strong fliers and can be carried several kilometers by air currents (Balch, 1939). Given that females are parthenogenetic, a single female can initiate a new population. All immature life stages of G. hercyniae can be transported to new areas by artificial means. For example, eggs and larvae can be transported on live plants or branch cuttings. For potted nursery stock infested with G. hercyniae, mature larvae could drop into the soil in the container and pupate. Although less likely, mature larvae could drop onto vehicles and other equipment and spin cocoons, and then be transported to new areas.

Economic impact

Currently, G. hercyniae is of little significance throughout its native range of Eurasia as well as in its introduced range of North America. Historically, outbreaks have occurred in Canada (Balch, 1939; Neilson & Morris, 1964), the United States (MacAloney, 1936: Baldwin, 1939; Dowden, 1939; Reeks and Barter, 1951), and Wales (UK) (Billany & Brown, 1977; Bevan, 1987) following the introduction of G. hercyniae without its natural enemies. During these outbreaks, usually after consecutive years of defoliation, spruce trees of various species have shown reduced growth rates, crown dieback, and at times widespread tree mortality (Balch, 1939; Martineau, 1943; Reeks & Barter, 1951; Billany, 1978; Williams et al., 2003).

Control

Control measures have not been necessary for G. hercyniae in its native range due to the presence of natural enemies. In its introduced range, large-scale biological control programs were successful in controlling G. hercyniae. The first outbreaks of G. hercyniae in North America occurred in Eastern Canada and the adjacent United States in the early 1930s. Given low parasitism rates in the infested areas by native natural enemies (Balch, 1939), about 25 different parasitoids were selected, primarily from Europe, reared, and released during the 1930s and early 1940s in both countries, totaling over a billion individuals released (Dowden, 1962; MacQuarrie et al., 2016). Several of these parasitoids became established, with some effective at high sawfly densities and others at low sawfly densities (Reeks, 1953; MacQuarrie et al., 2016). During the 1930s, a viral disease of G. hercyniae larvae was first noted in 1936 in laboratory colonies in Canada and then in field populations in 1938 (Balch and Bird, 1944). The virus was apparently introduced to Canada on parasitoid shipments from Europe. Over the next few years, this nuclear polyhedrosis virus was largely responsible for the collapse of G. hercyniae populations in North America (Bird & Elgee, 1957; Neilson & Morris, 1964; Magasi & Syme, 1981; van Frankenhuyzen et al., 2016). Similarly, in Wales, the same virus entered the country and controlled populations of G. hercyniae, especially where the sawfly was found at high levels. The virus is dispersed by birds after eating infected larvae (Entwistle et al., 1977), and by adult sawflies (Buse, 1977). Currently, the virus and parasitoids have kept G. hercyniae populations at low levels in North America and Wales (Magasi & Syme, 1981; Entwistle et al., 1983).

Phytosanitary risk

G. hercyniae is an EU listed Protected Zone Quarantine Pest (Annex III) for Greece, Ireland and the United Kingdom (Northern Ireland). It is widely distributed throughout the range of Picea in the EPPO region (where it is not a serious pest) but can cause severe defoliation and tree mortality when it moves to areas where it has no natural enemies. Currently, its population levels are well controlled by natural enemies, both within and outside of its natural range.

Plants for planting of Picea entering a protected zone (as detailed above) should be accompanied with an official statement that the plants have been produced in nurseries and that the place of production is free from G. hercyniae.

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Balch RE (1939) The outbreak of the European spruce sawfly in Canada and some important features of its bionomics. Journal of Economic Entomology 32, 412-418.

Balch RE & Birds FT (1944) A disease of the European spruce sawfly, Gilpinia hercyniae (Htg.), and its place in natural control. Scientific Agriculture 25, 65-80.

Balch RE, Reeks WA & Smith SG (1941) Separation of the European spruce sawfly in America from Gilpinia polytoma (Htg.) (Diprionidae, Hymenoptera) and evidence of its introduction. The Canadian Entomologist 73, 198-203.

Baldwin HI (1939) The European spruce sawfly in New Hampshire 1938. Journal of Forestry 37: 876-878.

Benes K & Kristek J (1979) Present state of taxonomy of European species of the families Pamphiliidae, Diprionidae, and Tenthredinidae (Hymenoptera, Symphyta) feeding on spruce. Acta Universitatis Agriculturae Brno, C (Facultas Silviculturae) 48, 77-118.

Benson RB (1939) On the genera of the Diprionidae (Hymenoptera Symphyta). Bulletin of Entomological Research 30, 339-342.

Benson RB (1951) Hymenoptera: Symphyta. Handbooks for the identification of British insects No. VI. 2(a). Royal Entomological Society, London, UK.

Bevan D (1987) Forest insects: a guide to insects feeding on trees in Britain. Forestry Commission Handbook, UK, No. 1. 153 pp.

Billany DJ (1978) Gilpinia hercyniae a pest of spruce. Forestry Commission Forest Record No. 117. HMSO, London, UK. 11 pp.

Billany DJ & Brown RM (1977) The geographical distribution of Gilpinia hercyniae Hymenoptera: Diprionidae in the United Kingdom. Forestry 50, 155-160.

Billany DJ, Borden JH & Brown RM (1978) Distribution of Gilpinia hercyniae (Hymenoptera Diprionidae) eggs within Sitka spruce trees. Forestry 51, 67-72.

Billany DJ, Carter CI, Winter TG & Fielding NJ (1983) The effects of climate and parasites on Gilpinia hercyniae (Hartig) (Hym: Diprionidae) in Britain. Entomologist's Monthly Magazine 119, 117-120.

Bird F & Elgee D (1957) A virus disease and introduced parasites as factors controlling the European spruce sawfly, Diprion hercyniae (Htg.), in central New Brunswick. The Canadian Entomologist 89, 371-378. 

Browne FG (1968) Pests and diseases of forest plantation trees: an annotated list of the principal species occurring in the British Commonwealth. Oxford, UK: Clarendon Press.

Buse A (1977) The importance of birds in the dispersal of nuclear polyhydrosis virus of European spruce sawfly Gilpinia hercyniae in mid Wales. Entomologia Experimentalis et Applicata 22, 191-199.

Dowden PB (1939) Present status of the European spruce sawfly, Diprion polytomum (Htg). in the United States. Journal of Economic Entomology 32, 619-624.

Dowden PB (1962) Parasites and predators of forest insects liberated in the United States through 1960. US Department of Agriculture, Forest Service, Agriculture Handbook, No. 226. US Government Printing Office, Washington, DC. 70 pp.

Entwistle PF, Adams PHW & Evans HF (1977) Epizootiology of a nuclear polyhydrosis virus in European spruce sawfly Gilpinia hercyniae; birds as dispersal agents of the virus during winter. Journal of Invertebrate Pathology 30, 15-19.

Entwistle PF, Adams PHW, Evans HF, & Rivers CF (1983) Epizootiology of a nuclear polyhedrosis virus (Baculoviridae) in European spruce sawfly (Gilpinia hercyniae): spread of disease from small epicentres in comparison with spread of baculovirus diseases in other hosts. Journal of Applied Ecology 20, 473-487.

Goulet H (1981) New external distinguishing characters for the sawflies Gilpinia hercyniae and G. polytoma. Canadian Entomologist 113, 769-771.

Holuša J & Roller L (2004) Notes to distribution and seasonal activity of spruce diprionids (Hymenoptera: Diprionidae) in the eastern part of the Czech Republic. Journal of Forest Science 50, 579-585.

Jensen TS (1988) Variability of Norway spruce (Picea abies L.) needles; performance of spruce sawflies (Gilpinia hercyniae Htg.). Oecologia (Berlin) 77, 313-320.

Langor DW, Cameron EK, MacQuarrie CJ, McBeath A, McClay A, Peter B, Pybus M, Ramsfield T, Ryall K, Scarr T & Yemshanov D (2014) Non-native species in Canada’s boreal zone: diversity, impacts, and risk. Environmental Reviews 22, 372-420. Lorenz H & Kraus M (1957) Die Larvalsystematik der Blattwespen (Tenthredinoidea und Megalodontoidea). Abhandlungen zur Larvalsystematik der Insecten. Vol. 1. Akademie-Verlag, Berlin, Germany. 339 pp.

MacAloney HJ (1936) The European spruce sawfly in the USA. Journal of Forestry 34, 125-129.

MacQuarrie CJ, Lyons DB, Seehausen ML & Smith SM (2016) A history of biological control in Canadian forests, 1882–2014. The Canadian Entomologist 148(S1), S239-S269.

Magasi LP & Syme PD (1981) Gilpinia hercyniae (Hartig), European spruce sawfly (Hymenoptera: Diprionidae). Pp 295-298 In: Biological control programmes against insects and weeds in Canada 1969-1980 (Ed. by Kelleher JS, Hulme MA). Commonwealth Agricultural Bureaux, Slough, UK.

Martineau R (1943) Population studies of the European spruce sawfly (Gilpinia hercyniae Htg.) in Quebec. The Forestry Chronicle 19, 87-107.

Morris RF (1942) The use of frass in the identification of forest insect damage. The Canadian Entomologist 74, 164-167.

Morris RF (1949) Frass drop measurement in studies of the European spruce sawfly. University of Michigan, School of Forestry and Conservation Bulletin No. 12. 58 pp. 

Neilson MM & Morris RF (1964) The regulation of European spruce sawfly numbers in the Maritime Provinces of Canada from 1937 to 19631. The Canadian Entomologist 96, 773-784.

Prebble ML (1941) The diapause and related phenomena in Gilpinia polytoma (Hartig): iv. Influence of food and diapause upon reproductive capacity. Canadian Journal of Research D 19, 417–436.

Prebble ML (1943) Sampling methods in population studies of the European spruce sawfly, Gilpinia hercyniae (Hartig), in Eastern Canada. Transactions of the Royal Society of Canada V, 93-126.

Reeks WA (1941) On the taxonomic status of Gilpinia polytoma (Htg.) and G. hercyniae (Htg.) (Hym., Diprionidae). The Canadian Entomologist 73, 177-188.

Reeks WA (1953) The establishment of introduced parasites of the European spruce sawfly (Diprion hercyniae (Htg.) (Hymenoptera: Diprionidae) in the Maritime Provinces. Canadian Journal of Agricultural Science 33, 405-429.

Reeks WA & Barter GW (1951) Growth reduction and mortality of spruce caused by the European spruce sawfly, Gilpinia hercyniae (Htg.) (Hymenoptera: Diprionidae). Forestry Chronicle 27, 140-156.

Smith SG (1941) A new form of spruce sawfly identified by means of its cytology and parthenogenesis. Scientific Agriculture 21, 245-305.

Smith DR (1974) Conifer sawflies, Diprionidae: Key to North American genera, checklist of world species, and new species from Mexico (Hymenoptera). Proceedings of the Entomological Society of Washington, 76, 409-418.

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Thalenhorst W (1968) Zur Kenntnis der Fichtenblattwespen VIII. Eizahl und Eiablage. Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz 75, 338-350.

van Frankenhuyzen K, Lucarotti C & Lavallée R (2016) Canadian contributions to forest insect pathology and to the use of pathogens in forest pest management. The Canadian Entomologist 148(S1), S210-S238.

Williams DT, Straw NA & Day KR (2003) Defoliation of Sitka spruce by the European spruce sawfly, Gilpinia hercyniae (Hartig): a retrospective analysis using the needle trace method. Agricultural and Forest Entomology 5, 235-245.

Wilson LF (1977) A guide to insect injury of conifers in the Lake States. US Department of Agriculture, Forest Service, Agriculture Handbook, No. 501. US Government Printing Office, Washington, DC. 218 pp.

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This datasheet was extensively revised in 2023 by Robert A. Haack, USDA Forest Service, Northern Research Station. His valuable contribution is gratefully acknowledged.

EPPO (2024) Gilpinia hercyniae. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2024-12-22)

This datasheet was first published in 1997 in the second edition of 'Quarantine Pests for Europe' and revised in 2023. 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).