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1 December 2016 Distribution, Host Records, and Symbiotic Fungi of Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) in China
You Li, Xinyao Gu, Matthew T. Kasson, Craig C. Bateman, Jianjun Guo, YinTse Huang, Qiao Li, Robert J. Rabaglia, Jiri Hulcr
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Euwallacea fornicatus (Eichhoff) (Coleoptera: Curculionidae) is an emerging invasive tree pest, but its native distribution remains incompletely known because minimal records have been published from China. We report the distribution of E. fornicatus in China from records in the National Zoological Museum of China and from our own samples, including the first family-level host records in the Actinidiaceae, Oleaceae, and Pinaceae. We also report a parasitoid of E. fornicatus from Guizhou, China, and two fungi associated with E. fornicatus: a putatively new Fusarium sp. belonging to the monophyletic Ambrosial Fusarium Clade and an anamorphic hypocrelean fungus, Sarocladium strictum.

Euwallacea (Coleoptera: Curculionidae) is a genus of mostly Asian ambrosia beetles (Storer et al. 2015). The genus includes over 50 recognized species and is increasingly important due to several globally invasive pest species (Mendel et al. 2012; Eskalen et al. 2013; Li et al. 2014). Currently, the most damaging are several populations within the species complex called Euwallacea fornicatus (Eichhoff), associated with fungal mutualists in the Ambrosia Fusarium Clade and the fungal genus Raffaelea (Freeman et al. 2013; Kasson et al. 2013). This beetle-fungus complex is able to injure or kill trees by mass accumulation, in which each beetle inoculates the mildly pathogenic symbiont (Smith & Hulcr 2015). Euwallacea fornicatus has a vast distribution throughout Asia and Oceania, and has recently been introduced and established in Mesoamerica and several locations in the United States (Rabaglia et al. 2006; Kirkendall & Ødegaard 2007). This species (or complex of species) has a broader host range than previously thought (Browne 1961; Danthanarayana 1968), and has much wider distribution (James 2007; CABI 2015).

Little is known regarding the distribution of this increasingly important pest in China (Li et al. 2014, 2015). Even the Catalog of Scolytidae and Platypodidae (Wood & Bright 1992), an essential reference for scolytine biogeography, contains few records of this species from China. Browne (1961) and Danthanarayana (1968) comprehensively recorded its host range in Sri Lanka, India, and Southeast Asia, but neither included any records from China. Consequently, any research on the biogeographic, ecological, and climate-related aspects of this beetle is currently likely to suffer a significant gap in the baseline data.

Here we present previously unpublished host records of E. fornicatus deposited in the National Zoological Museum of China (NZMC), Institute of Zoology, Chinese Academy of Sciences, Beijing, and from extensive field investigation in China from 2013 to 2015. Chinese host tree names were associated with scientific names according to Iconographia Cormophytorum Sinicorum Tomus website ( The collection at the NZMC in Beijing contains 193 specimens of E. fornicatus collected from 1960 to 1999. Huifen Yin and Fusheng Huang identified the specimens.

The collection data show that this beetle in mainly distributed in the humid and subtropical southern China, but it also occurs in distinctly temperate and dry habitats (Fig. 1). Seven tree species are recorded for the first time as host plants of E. fornicatus (Table 1). Three of them belong to plant families from which the beetle has not been recorded before, namely, Actinidiaceae, Oleaceae, and Pinaceae. One of the authors (Y. L.) observed a complete family (eggs, larvae, pupae, and adults) on a weakened Pinus massoniana (Pinaceae) in Oct 2015. To our knowledge, this is the first record of E. fornicatus from a conifer. Although a single record from a particular host plant is not necessarily indicative of a stable host association, E. fornicatus is known to have broad host tree specificity, and it suggests that the fungal mutualist is viable in conifers.

Our data suggest that in its native habitat, E. fornicatus is capable of colonizing still-living tissues of angiosperm hosts. This may help explain the beetle's unique semiochemical ecology (Kendra et al. 2011). However, most of our data do not suggest that the beetle is an aggressive colonizer of living and healthy trees, because nearly all individuals in our collection were collected from weak, diseased, or dead host plants. We were not able to corroborate the supposed aggressive attacks on Litchi chinensis (Sapindaceae) in the south of China reported previously (Wang & Yuan 2003) even after our visit to the sites from which the event was recorded. We only found this beetle mass attacking relatively healthy Acer buergerianum (Sapindaceae) and Platanus orientalis (Platanaceae) in an urban area of Kunming City. The NZMC collection labels do not contain information on whether the trees were killed by the beetle.

In Guiyang, Guizhou (26.3857°N, 106.6731°E) on a log of black locust Robinia pseudoacacia (Fabaceae), we found more than 10 dead individuals of E. fornicatus bearing distinct signs of having been parasitized by an unknown natural enemy. The parasitoid consumed the abdomen of E. fornicatus and bored an exit hole through the elytral declivity (Fig. 2). Unfortunately, the parasitoid was not collected. This symptom is known from other Scolytinae beetles parasitized by Hymenoptera (Nierhaus-Wunderwald 1993), and this observation suggests that a search for natural enemies as a part of biocontrol efforts may be fruitful.

Fig. 1.

The distribution of Euwallacea fornicatus in the south of China.


Additionally, two fungi isolated from E. fornicatus and its gallery in Guizhou were identified. The first fungus was morphologically similar to a recently described Paracremonium pembeum, a known mycangial commensal of the polyphagous shot hole borer (E. fornicatus species complex) in California and Vietnam (Lynch et al. 2016). About 15,000 colony forming units (CFUs) of it were isolated from the oral mycangia of one individual. Cultures were slimy to moderately floccose, and pale pink to salmonaceous in color. The conidia were generated in simple verticillate phialides. The fungus was identified by amplifying the ribosomal DNA (rDNA) internal transcribed spacer (ITS) and querying the GeneBank database of the National Center for Biotechnology Information. Three representative ITS rDNA sequences (Hulcr12051 and LL84) were 100% identical to the hypocrealean fungus Sarocladium strictum and an uncultured Acremonium (GenBank accessions KM249080 and HG936339, respectively). Sarocladium has previously been reported to be associated with bark and ambrosia beetles throughout the northern temperate region (Hutchison 1999; Jankowiak et al. 2007; Jankowiak & Kolařík 2010), as well as from mites Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) in Taiwan (Hsieh et al. 1980). Acremonium sp. had been isolated from E. fornicatus (Freeman et al. 2016).

The second fungus was consistent with the known nutritional mutualist of Euwallacea, a representative of the Ambrosial Fusarium Clade (AFC, Kasson et al. 2013). It produced abundant aerial mycelia and clavate macroconidia forming in sporodochia; 8,000 CFUs were isolated from the oral mycangia of one individual. Portions of the translation elongation factor 1-α (EF1-α) and the second largest subunit of RNA polymerase 2 (RPB2) were used to confirm placement among known AFC members (Kasson et al. 2013). Initial GenBank BLAST searches revealed isolate 12049A, 12049B, and LL74 RPB2 sequences were 99 to 100% identical to Fusarium euwallaceae strains NRRL 62626 and FD31 ACVI (GenBank accessions KU171702 and JX892009, respectively). A BLAST search of EF1 sequences revealed that strains Hulcr12049 and LL74 had 99% similarity to Fusarium sp. AF-12, AF-5, and AF-4 and Fusarium ambrosium (GenBank accessions KM406629, KC691542, KC691537, and KC691528, respectively). Conclusively, our sequencing results indicate that the Fusarium sp. associated with E. fornicatus in China is a member of the monophyletic AFC. However, sequencing of additional loci is needed to confirm whether or not these strains represent a novel species.

We thank Jian Yao and Menglei Zhang (Institute of Zoology, Chinese Academy of Sciences) for facilitating access to the collection records. Additional thanks to Yingchao Ji (Beijing Forestry University, China) for improving the distribution map, Guangyu Liu and Wei Mo (Guizhou University, China) for assisting with beetle collections, Angie Macias and Matt Berger (West Virginia University) for help with DNA sequencing and molecular identification, and Paloma C. de Grammont and Claudia Paez for translating the summary. The authors Y. L. and J. H. were supported by the USDA-FS-FHP Coop agreement 12-CA-11420004-042, USDA Farm Bill agreement 12- 8130-0377-CA, and the National Science Foundation DEB 1256968. This material was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture's Animal and Plant Health Inspection Service (APHIS). It may not necessarily express APHIS views.

Table 1.

Host trees of Euwallacea fornicatus specimens in the National Zoological Museum of China (NZMC) and our new field collection from 2013 to 2015.


Fig. 2.

The elytral declivity of Euwallacea fornicatus after being parasitized by an unknown natural enemy.


References Cited


Browne FG. 1961. The Biology of Malayan Scolytidae and Platypodidae. Malayan Forest Records, Volume 22. Government Press, Malaya. Google Scholar


CABI (Centre for Agriculture and Biosciences International). 2015. Euwallacea fornicatus (Eichhoff, 1868). Invasive Species Compendium, (last accessed 30 Mar 2016). Google Scholar


Danthanarayana W. 1968. The distribution and host-range of the shot hole borer (Xyleborus fornicatus Eichh.) of tea. Tea Quarterly 39: 61–69. Google Scholar


Eskalen A, Stouthamer R, Lynch SC, Rugman-Jones PF, Twizeyimana M, Gonzalez A, Thibault T. 2013. Host range of Fusarium dieback and its ambrosia beetle (Coleoptera: Scolytinae) vector in southern California. Plant Disease 97: 938–951. Google Scholar


Freeman S, Sharon M, Maymon M, Mendel Z, Protasov A, Aoki T, Eskalen A, O'Donnell K. 2013. Fusarium euwallaceae sp. nov.-a symbiotic fungus of Euwallacea sp., an invasive ambrosia beetle in Israel and California. Mycologia 105: 1595–1606. Google Scholar


Freeman S, Sharon M, Dori-Bachash M, Maymon M, Belausov E, Maoz Y, Margalit O, Protasov A, Mendel Z. 2016. Symbiotic association of three fungal species throughout the life cycle of the ambrosia beetle Euwallacea nr. fornicatus. Symbiosis 68: 115–128. Google Scholar


Hsieh SPY, Shue MF, Liang WJ. 1980. Etiological studies on the sterility of rice plant. II. Transmission and survival of Acrocylindrium oryzae Sawada, the fungus associated with sterile rice plant. Plant Protection Bulletin 22: 41–46. Google Scholar


Hutchison LJ. 1999. Wood-inhabiting microfungi isolated from Populus tremuloides from Alberta and northeastern British Columbia. Canadian Journal of Botany 77: 898–905. Google Scholar


James SP. 2007. Studies on certain plant volatiles attracting the shot hole borer, Euwallacea fornicatus (Eichhoff) (Scolytidae: Coleoptera) infesting tea. Ph.D. thesis, Bharathiar University, Tamil Nadu, India. Google Scholar


Jankowiak R, Kolařík M. 2010. Fungi associated with the fir bark beetle Cryphalus piceae in Poland. Forest Pathology 40: 133–144. Google Scholar


Jankowiak R, Rossa R, Mista K. 2007. Survey of fungal species vectored by Ips cembrae to European larch trees in Raciborskie forests (Poland). Czech Mycology 59: 227–239. Google Scholar


Kasson MT, O'Donnell K, Rooney AP, Sink S, Ploetz RC, Ploetz JN, Konkol JL, Carrillo D, Freeman S, Mendel Z, Smith JA, Black AW, Hulcr J, Bateman C, Stefkova K, Campbell PR, Geering ADW, Dann EK, Eskalen A, Mohotti K, Short DPG, Aoki T, Fenstermacher KA, Davis DD, Geiser DM. 2013. An inordinate fondness for Fusarium: phylogenetic diversity of fusaria cultivated by ambrosia beetles in the genus Euwallacea on avocado and other plant hosts. Fungal Genetics and Biology 56: 147–157. Google Scholar


Kendra PE, Montgomery WS, Niogret J, Peña JE, Capinera JL, Brar G, Epsky ND, Heath RR. 2011. Attraction of the redbay ambrosia beetle, Xyleborus glabratus, to avocado, lychee, and essential oil lures. Journal of Chemical Ecology 37: 932–942. Google Scholar


Kirkendall LR, Ødegaard F. 2007. Ongoing invasions of old-growth tropical forests: establishment of three incestuous beetle species in southern Central America (Curculionidae: Scolytinae). Zootaxa 1588: 53–62. Google Scholar


Li Q, Zhang GH, Guo HW, He GL, Liu B. 2014. Euwallacea fornicatus, an important pest insect attacking Acer buergerianum. Forest Pest and Disease 33: 25–27. (In Chinese) Google Scholar


Li Q, Guo HW, Zhao Y, Zhang G, He GL, Liu B. 2015. Damage caused by Euwallacea fornicatus (Coleoptera: Scolytidae) and its control techniques in Kunming. Plant Protection 41: 193–196. (In Chinese) Google Scholar


Lynch SC, Twizeyimana M, Mayorquin JS, Wang DH, Na F, Kayim M, Kasson MT, Thu PQ, Bateman C, Rugman-Jones P, Hulcr J, Stouthamer R, Eskalen A. 2016. Identification, pathogenicity and abundance of Paracremonium pembeum sp. nov. and Graphium euwallaceae sp. nov.-two newly discovered mycangial associates of the polyphagous shot hole borer (Euwallacea sp.) in California. Mycologia 108: 313–329. Google Scholar


Mendel Z, Protasov A, Sharon M, Zveibil A, Yehuda SB, O'Donnell K, Rabaglia RJ, Wysoki M, Freeman S. 2012. An Asian ambrosia beetle Euwallacea fornicatus and its novel symbiotic fungus Fusarium sp. pose a serious threat to the Israeli avocado industry. Phytoparasitica 40: 235–238. Google Scholar


Nierhaus-Wunderwald D. 1993. Die natürlichen Gegenspieler der Borkenkäfer. Wald und Holz 1: 8–14. Google Scholar


Rabaglia RJ, Dole SA, Cognato AI. 2006. Review of American Xyleborina (Coleoptera: Curculionidae: Scolytinae) occurring north of Mexico, with an illustrated key. Annals of the Entomological Society of America 99: 1034–1056. Google Scholar


Smith S, Hulcr J. 2015. Scolytus and other economically important bark and ambrosia beetles, pp. 495-531 In Vega FE, Hofstetter RW [eds.], Bark Beetles. Academic Press, San Diego, California. Google Scholar


Storer CG, Breinholt JW, Hulcr J. 2015. Wallacellus is Euwallacea: molecular phylogenetics settles generic relationships (Coleoptera: Curculionidae: Scolytinae: Xyleborini). Zootaxa 3974: 391–400. Google Scholar


Wang WR, Yuan ZY. 2003. A new pest of litchi, Xyleborus fornicatus and its control. South China Fruits 32(5): 34–35. (In Chinese) Google Scholar


Wood SL, Bright DE. 1992. A Catalog of Scolytidae and Platypodidae (Coleoptera), Part 2. Taxonomic Index. Great Basin Naturalist Memoirs, 1553 pp. Google Scholar
You Li, Xinyao Gu, Matthew T. Kasson, Craig C. Bateman, Jianjun Guo, YinTse Huang, Qiao Li, Robert J. Rabaglia, and Jiri Hulcr "Distribution, Host Records, and Symbiotic Fungi of Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) in China," Florida Entomologist 99(4), 801-804, (1 December 2016).
Published: 1 December 2016

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