Preferred name: Gonipterus scutellatus species complex
Taxonomic position: Animalia: Arthropoda: Hexapoda: Insecta: Coleoptera: Curculionidae: Gonipterinae
Common names in English: eucalyptus snout beetle, eucalyptus weevil, gum-tree weevil
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Notes on taxonomy and nomenclature EPPO Categorization: A2 list
EU Categorization: PZ Quarantine pest (Annex III)
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EPPO Code: GONPSC

Many species of Eucalyptus have been reported as hosts of Gonipterus with varying degrees of susceptibility (Mally, 1924; Tooke, 1955; Richardson & Meakins, 1986; Newete et al., 2011).  The most susceptible species are E. camaldulensis, E. globulus, E. maidenii, E. punctata, E. robusta, E. smithii, E. viminalis, E. dunnii, E. ovata, E. urophylla, and E. grandis. Host associations vary between species of Gonipterus (Garcia et al., 2019; Souza et al., 2021; Schröder et al., 2021). A recent study in Tasmania found G. platensis and G. pulverulentus have similar host associations, mainly occurring on E. ovata and small numbers of G. platensis were recorded from E. globulus and E. viminalis (Garcia et al., 2019). E. smithii, E. grandis, E. urophylla and E. viminalis were found to be amongst the most susceptible Eucalyptus species for Gonipterus sp. n. 2 in South Africa (Newete et al., 2011).

Within the EPPO region Eucalyptus spp. are economically important hosts.

Host list: Eucalyptus amplifolia, Eucalyptus amygdalina, Eucalyptus benthamii, Eucalyptus blakelyi, Eucalyptus bosistoana, Eucalyptus bridgesiana, Eucalyptus camaldulensis, Eucalyptus cinerea, Eucalyptus conspicua, Eucalyptus cornuta, Eucalyptus crenulata, Eucalyptus dalrympleana, Eucalyptus deanei, Eucalyptus dunnii, Eucalyptus exserta, Eucalyptus foecunda, Eucalyptus globulus, Eucalyptus goniocalyx, Eucalyptus grandis, Eucalyptus lehmannii, Eucalyptus longicornis, Eucalyptus longifolia, Eucalyptus loxophleba, Eucalyptus macarthurii, Eucalyptus maidenii, Eucalyptus major, Eucalyptus mannifera subsp. maculosa, Eucalyptus melanophloia, Eucalyptus melliodora, Eucalyptus microcorys, Eucalyptus microtheca, Eucalyptus morrisbyi, Eucalyptus nicholii, Eucalyptus nitens, Eucalyptus obliqua, Eucalyptus occidentalis, Eucalyptus ovata subsp. ovata, Eucalyptus ovata, Eucalyptus pauciflora, Eucalyptus platypus subsp. platypus, Eucalyptus propinqua, Eucalyptus pulchella, Eucalyptus punctata, Eucalyptus radiata, Eucalyptus redunca, Eucalyptus robusta, Eucalyptus rubida, Eucalyptus scoparia, Eucalyptus smithii, Eucalyptus tereticornis, Eucalyptus urnigera, Eucalyptus urophylla, Eucalyptus viminalis, Eucalyptus x kirtoniana

The G. scutellatus species complex originates in south-eastern Australia and has spread with its hosts to many parts of the world. The three invasive species, G. platensis, G. pulverulentus and Gonipterus sp. n. 2 differ in their native and invasive distribution ranges (Mapondera et al., 2011; Garcia et al., 2019; Schröder et al., 2021). In the EPPO region, G. platensis is present in Portugal and Spain and Gonipterus sp. n. 2 in France and Italy.

EPPO Region: France (mainland, Corse), Italy (mainland, Sicilia), Portugal (mainland, Azores), Spain (mainland, Islas Canárias)
Africa: Eswatini, Kenya, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Rwanda, Saint Helena, South Africa, Tanzania, Uganda, Zimbabwe
North America: United States of America (California, Hawaii)
South America: Argentina, Brazil (Bahia, Espirito Santo, Minas Gerais, Parana, Rio Grande do Sul, Santa Catarina, Sao Paulo), Chile, Colombia, Ecuador, Uruguay
Oceania: Australia (New South Wales, Queensland, South Australia, Tasmania, Victoria, Western Australia), New Zealand

The species belonging to the G. scutellatus species complex is of little economic importance in their native range in Australia but are significant pests of Eucalyptus in the invasive range. Eggs are attached to leaves in clusters of four to sixteen eggs and covered with a frass excrement to form a capsule. Females mate several times and continue to oviposit throughout a lifetime of about 60 - 91 days. A female produces between 20 and 33 egg capsules in her lifetime.   Incubation is temperature dependent and can take one to two weeks to complete. There are four larval stages which are covered in sticky slime that keeps them adhered to the leaves. Larval development takes 4-6 weeks to complete. Adults and larvae feed on leaves. The mature larvae drop to the ground where pupation occurs in cells about 5 cm deep in the soil. Pupation takes 30-40 days to complete. The sex ratio is about 1:1 and females can mate with several males. In the laboratory, adults mated 4-9 days after emergence, and began to lay eggs after a further 13-21 days. Development is temperature dependent and the beetles take 2-3 months to complete the entire life cycle. There are about four generations annually in Mauritius, continuing throughout the year. In South Africa there are 2 to 2.5 generations and overwintering occur in the adult and pupal stage. In Italy two generations are recorded and between 1 and 3 generations occur in Spain.

For further information on the biology of G. scutellatus species complex see Mally (1924), Moutia & Vinson (1945), Tooke (1955), Leyva (1969 & 1970), Arzone & Meotto (1978), Santolamazza-Carbone & Rivera 1998, Santolamazza-Carbone et al. 2006.

Symptoms

The adult beetles feed on the edges of the leaves resulting in a characteristically scalloped appearance. The larvae feed on the epidermis and mesophyll of the young leaves causing tracks the width of the larvae in the leaves and mature larvae will consume entire leaves. Feeding damage results in defoliation of the tree crown, dieback of shoot tips and development of tufts of epicormics. Successive defoliations produce stunting and a stag-headed appearance. Trees may split and die. Adults tend to feed on the leaves and soft bark of young shoots while larval damage occurs on the leaves alone (Moutia & Vinson, 1945; Kevan, 1964; Leyva, 1969; 1970).

Morphology

Eggs

Eggs capsules are grey to brown containing clusters of yellow eggs. An egg capsule contain four to sixteen eggs, attached to the leaves on both surfaces (Mally, 1924; Tooke, 1955). The egg capsules vary in size and measure 1 - 3 mm in length, 1 – 1.5 mm in width and 1 - 2 mm in height (Tooke, 1955).

Larva

The head of the larvae is black and the body is yellowish-green with black shield like spots on each segment and dark lateral stripes. Larvae are covered in a sticky slime (Tooke, 1955. EFSA, 2018).

Adult

A 7.5 - 9.4 mm grey-brown weevil, with a black x-shaped marking on the elytra and a white scutellar stripe, often extending to the head (Tooke, 1955; EFSA, 2018). These markings may fade with the age of the beetle and vary between species.

Detection and inspection methods

Visual inspection of leaf material for the presence of feeding damage, egg capsules or larvae. 

Identification up to genus level can be done using morphological characteristics. The morphology of the male genitalia and DNA barcoding techniques are used for species identification (Mapondera et al., 2012).

The main pathways of entry are natural spread by flight, trade in Eucalyptus timber and trade of plants for planting and cut branches for floral arrangements and hitchhiking (EFSA, 2018).   Adults, larvae and eggs may be carried on planting material. Larvae and pupae could be present in accompanying soil. Hitchhiking on apple consignments imported into South Africa from Australia has been suggested as a pathway for movement (EFSA, 2018, citing Mally, 1924; Clark, 1931; Tooke, 1955). In Australia and New Zealand, infestations of apple orchards by adults necessitates the need for control measures before the commodity is exported (EFSA, 2018).

Economic impact

In its introduced range, this pest has become an important defoliator of Eucalyptus causing significant reduction in wood production and tree death (Tooke, 1955; Williams et al., 1951). Damage to Eucalyptus plantations have been significantly reduced due to the introduction of the biological control agent Anaphes nitens (Tooke, 1955; Hanks et al., 2000). Despite the initial success of the biological control program for this pest it remains an important economic pest with outbreaks sporadically observed in many Eucalyptus producing countries (Tooke, 1955; Loch et al., 2006; Reis et al., 2012). Defoliation of the upper crown reduces stem growth and can result in merchantable wood loss of up to 86 % over a ten-year growing period (Reis et al., 2012).  The eucalyptus snout beetle continues to spread and has recently invaded Colombia (Rodas, 2018) and Rwanda (Schröder et al., 2021).

Control

The biological control agent A. nitens has been released globally as a control measure against the eucalyptus snout beetle. Successful control with A. nitens is claimed in France and Italy (Cadahia, 1986). In addition to A. nitens, A. tasmaniae was released in Chile and A. inexpectatus in Portugal and Spain (Mayorga, 2013; Valente et al., 2017).

Chemical treatment is not recommended because of low efficacy, adverse environmental effects and increased production cost (EFSA, 2018).

Phytosanitary risk

The G. scutellatus species complex is considered a phytosanitary risk to the EPPO region due to its polyphagous feeding habits and economic damage associated with feeding.   Severe defoliation of hosts can reduce the volume of wood that can be sold.  In the EPPO region, countries such as Spain have large productive Eucalyptus plantations.  E. globulus is the dominant species in northern and north-western Spain.

In the EPPO region, the G. scutellatus species complex poses a threat to Eucalyptus plantations.

Phytosanitary measures are in place for the trade of plants. Countries importing propagating material and cut branches of Eucalyptus have to ensure the consignment is free from soil and has been subjected to a treatment against G. scutellatus species complex, or that it comes from an area where G. scutellatus species complex does not occur. Countries may require a phytosanitary certificate for cut branches of Eucalyptus.

Arzone A & Meotto F (1978) [Biological findings on Gonipterus scutellatus Gyll. (Col. Curculionidae) infesting eucalyptus trees on the Ligurian riviera]. Redia 41, 205-222.

Cadahia D (1986) The importance of insect pests in the Mediterranean region. EPPO Bulletin 16, 265-283.

Clark AF (1931) The parasite control of Gonipterus scutellatus Gyll. New Zealand Journal of Science and Technology 13, 22–28

Garcia A, Allen GR, Oberprieler RG, Ramos AP, Valente C, Reis A, Franco JC & Branco M (2019) Biological control of Gonipterus: Uncovering the associations between eucalypts, weevils and parasitoids in their native range. Forest Ecology and Management 443, 106-116.

Griffith AL (1959) A list of Eucalyptus species known to be attacked by the snout beetle Gonipterus scutellatus. Empire Forestry Review 38, 200-201.

Hanks LM, Millar JG, Paine TD & Campbell CD (2000) Classical biological control of the Australian weevil Gonipterus scutellatus (Coleoptera:Curculionidae) in California. Environmental Entomology 29, 369-375.

EFSA Panel on Plant Health (PLH), Jeger M, Bragard C, Caffier D, Candresse T, Chatzivassiliou E, Dehnen-Schmutz K, Gilioli G, Miret J, Anton J, MacLeod A, Navarro MN, Niere B, Parnell S, Potting R, Rafoss T, Rossi V, Urek G, Van Bruggen A, Van der Werf W, West J, Winter S, Santolamazza-Carbone S, Kertesz V, Aukhojee M & Grégoire J-C (2018) Scientific opinion on the pest categorisation of the Gonipterus scutellatus species complex. EFSA Journal 16, 1-34. https://doi.org/10.2903/j.efsa.2018.5107

Kevan DK (1964) The eucalyptus weevil in East Africa. East African Agricultural and Forestry Journal 12, 40-44.

Leyva E (1969) [Present situation of the pests on Eucalyptus sp. world-wide]. Boletín del Servicio de Plagas Forestales No. 24, 119-128.

Leyva E (1970) [Present situation of the pests on Eucalyptus sp. world-wide]. Boletín del Servicio de Plagas Forestales No. 25, 67-80.

Loch AD (2006) Phenology of Eucalyptus weevil, Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), and chrysomelid beetles in Eucalyptus globulus plantations in south-western Australia. Agricultural and Forest Entomology 8, 155–165.

Mapondera TS, Burgess T, Matsuki M & Oberprieler RG (2012) Identification and molecular phylogenetics of the cryptic species of the Gonipterus scutellatus complex (Coleoptera: Curculionidae: Gonipterini). Austral Entomology 51, 175-188.

Mally CW (1924) The eucalyptus snout beetle (Gonipterus scutellatus Gyll.). Journal Department of Agriculture for South Africa 9, 415-442.

Mayorga SEI (2013) Anaphes tasmaniae, parasitoid of Gonipterus platensis (Coleoptera: Curculionidae) introduced in Chile. ISBCA, Chile.

Moutia LA & Vinson J (1945) Le charançon de l'Eucalyptus, Gonipterus scutellatus Gyll. Revue Agricole et Sucrière de Maurice 24, 25-30.

Newete SW, Oberprieler RG & Byrne MJ (2011) The host range of the eucalyptus weevil, Gonipterus “scutellatus” Gyllenhal (Coleoptera: Curculionidae), in South Africa. Annals of Forest Science 68, 1005–1013.

Recalde A (1956) [The eucalyptus snout beetle (Gonipterus gibberus)]. Cultivador Moderno 39, 166.

Reis AR, Ferreira L, Tomé M, Araujo C & Branco M (2012) Efficiency of biological control of Gonipterus platensis (Coleoptera: Curculionidae) by Anaphes nitens (Hymenoptera: Mymaridae) in cold areas of the Iberian Peninsula: Implications for defoliation and wood production in Eucalyptus globulus. Forest Ecology and Management 270, 216-222.

Richardson KF & Meakins RH (1986) Inter- and intra-specific variation in the susceptibility of eucalypts to the snout beetle Gonipterus scutellatus Gyll. (Coleoptera: Curculionidae). South African Forestry Journal 139, 21-31.

Rodas C (2018) Important insect pest and diseases affecting plantation forestry in Colombia. In: IUFRO working party meeting 7.02.13, Improving forest health on commercial plantations: book of abstracts, Punta del Este, 21–23 March 2018. [accessed on 2 October 2018].

Santolamazza-Carbone S, Cordero-Rivera A (1998) Sperm competition, cryptic female choice and prolonged mating in the Eucalyptus Snout-Beetle, Gonipterus scutellatus (Coleoptera: Curculionidae). Etologia 6, 33-40.

Santolamazza-Carbone S, Rodriguez-Illamola A & Cordero Rivera A (2006) Thermal requirements and phenology of the Eucalyptus snout beetle Gonipterus scutellatus Gyllenhal. Journal of Applied Entomology 130, 368-376.

Schröder ML, Slippers B, Wingfield MJ & Hurley BP (2020) Invasion history and management of Eucalyptus snout beetles in the Gonipterus scutellatus species complex. Journal of Pest Science 93, 11-25.

Schröder ML, Nahrung HF, Souza NM, Lawson S, Slippers B, Wingfield MJ & Hurley  BP (2021) Distribution of Gonipterus species and their egg parasitoids in Australia: Implications for biological control. Forests 12(8), 969. https://doi.org/10.3390/f12080969 

Souza NM, Lawson SA, Nahrung HF (2021) Gonipterus (Coleoptera: Curculionidae) in subtropical Australia: Host associations and natural enemies. Austral Entomology 60(3), 588-597.

Tooke FGC (1955) The eucalyptus snout beetle Gonipterus scutellatus Gyll. A study of its ecology and control by biological means. Entomology Memoir, Department of Agriculture South Africa 3, 1-282.

Valente C, Gonçalves CI, Reis A & Branco M (2017) Pre-selection and biological potential of the egg parasitoid Anaphes inexpectatus for the control of the Eucalyptus snout beetle, Gonipterus platensis. Journal of Pest Science 90, 911–923.

Williams JR, Moutia LA & Hermelin PR (1951) The biological control of Gonipterus scutellatus Gyll. (Col. Curculionidae) in Mauritius. Bulletin of Entomological Research 42, 23-28.

This datasheet was extensively revised in 2021 by Michelle Schröder, Department Zoology and Entomology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria. Her valuable contribution is gratefully acknowledged.

EPPO (2024) Gonipterus scutellatus species complex. EPPO datasheets on pests recommended for regulation. https://gd.eppo.int (accessed 2024-11-21)

This datasheet was first published in the EPPO Bulletin in 1980, revised in the two editions of 'Quarantine Pests for Europe' in 1992 and 1997, revised again in 2005, as well as in 2021. 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.

EPPO (2005) Data sheets on quarantine pests - Gonipterus gibberus and Gonipterus scutellatus. EPPO Bulletin 35(3), 368-370. https://doi.org/10.1111/j.1365-2338.2005.00855.x

EPPO (1980) Data sheets on quarantine organisms. Gonipterus gibberus Boisd and Gonipterus scutellatus Gyll. Coleoptera: Curculionidae. EPPO Bulletin 10(1), 4 pp. https://doi.org/10.1111/j.1365-2338.1980.tb02696.x

CABI/EPPO (1992/1997) Quarantine Pests for Europe (1^st and 2^nd edition). CABI, Wallingford (GB).