Platypus quercivorus
(oak ambrosia beetle)

Pictures

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Identity

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Preferred Scientific Name

• Platypus quercivorus (Murayama, 1925)

Preferred Common Name

• oak ambrosia beetle

Other Scientific Names

• Crossotarsus quercivorus Murayama, 1925
• Crossotarsus sexfenestratus Beeson, 1937

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Arthropoda
•             Subphylum: Uniramia
•                 Class: Insecta
•                     Order: Coleoptera
•                         Family: Platypodidae
•                             Genus: Platypus
•                                 Species: Platypus quercivorus

Notes on Taxonomy and Nomenclature

Top of page P. quercivorus was first described from specimens collected in Taiwan (Formosa) by Murayama in 1925 and placed in the genus Crossotarsus. In 1937, Beeson described this species as Crossotarsus sexfenestratus from material collected in India. It was assigned to the genus Platypus by Schedl in 1972 (Beaver and Hsien-Tzung Shih, 2003).

Description

Top of page Eggs

The eggs are elongated and cylindrical.

Larvae

The larvae are variable in size and range from 2-6 mm long when mature. They are legless and creamy-white, with an amber to light-brown head capsule. The last abdominal segment ends in a flat to slightly concave declivity.

Pupae

The pupae are creamy-white and have partially developed wings and appendages.

Adults

The adults of the genus Platypus are reddish-brown to dark-brown with a cylindrical, elongated body that averages 5 mm long. These insects have a concave elytral declivity armed with spines. The front (prothoracic) legs are adapted for excavation.

Distribution

Top of page P. quercivorus is widely distributed in Asia, including temperate, subtropical and tropical ecosystems in India, Indonesia (Java), Japan, Papua New Guinea and Taiwan (Beaver and Hsien-Tzung Shih, 2003). In Japan, this insect is found from the island of Ishigaki Shima to Honshu (Hamaguchi and Goto, 2003).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

Top of page The adults are capable of sustained flight for at least 1 km and may also be dispersed on air currents. All life stages are subjected to human-assisted dispersal. The use of oak crating, pallets or dunnage in international trade could result in the inter-continental spread of all the life stages of P. quercivorus. The localized spread of newly established infestations could be facilitated via the transport of logs and firewood.

Habitat

Top of page P. quercivorus can be found in temperate, subtropical and tropical forests. It is presently a pest of mixed oak forests in parts of Japan.

Hosts/Species Affected

Top of page P. quercivorus has a wide host range. It attacks many species of the family Fagaceae but it is also known to attack trees from other families including Aquifoliaceae, Lauraceae, Rosaceae and Cupressaceae (Wood and Bright, 1992).

Host Plants and Other Plants Affected

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Growth Stages

Top of page Vegetative growing stage

Symptoms

Top of page The external symptoms of infestation include copious amounts of white, splinter-like boring dust near the base of infested oaks, and late summer wilting of the foliage of attacked trees. Examination of the wood will reveal a brown discoloration in the sapwood surrounding the galleries of P. quercivorus. Fungal hyphae can be found in the vessels near the beetle galleries (Kuroda and Yamada, 1996).

List of Symptoms/Signs

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Biology and Ecology

Top of page The genus Platypus is exceptionally large within the Platypodidae, with several hundred recognized species. These are distributed throughout the world's temperate and tropical forests, and attack both broadleaf and coniferous trees (Bright and Skidmore, 2002). Eight species are known to occur in North America (Furniss and Carolin, 1977; Drooz, 1985; Cibrián Tovar et al., 1995). These include Platypus flavicornis [Myoplatypus flavicornis], which invades the basal portions of pines in large numbers in south-eastern USA following attacks by bark beetles, and Platypus parallelus [Euplatypus parallelus], a tropical species present in southern USA and Mexico, which is regarded as the most destructive ambrosia beetle in the world (Drooz, 1985).

Members of the genus Platypus are ambrosia beetles and breed in the wood of host trees. White splinters are produced during gallery construction as opposed to fine sawdust, which is produced by other ambrosia beetles. Also, unlike other ambrosia beetles, the galleries of Platypus spp. often penetrate into the heartwood. The larvae and adults feed on ambrosia fungi, which are stored and disseminated by the adult female. The fungal associates of several species of Platypus are members of the genus Raffaelea. In western North America, the ambrosia fungus associated with Platypus wilsoni is Raffaelea canadensis (Furniss and Carolin, 1977). In Argentina, Raffaelea santoroi is associated with Platypus mutatus (Giménez and Etiennot, 2003). In Europe, Raffaelea ambrosiae is associated with the oak ambrosia beetle, Platypus cylindrus (Babuder and Pohleven, 1995).

Adult ambrosia beetles vector their associated ambrosia fungi via structures known as mycangia, which store fungal spores. In the family Platypodidae, if mycangia are present, they are simple; usually small pits or notches in the integument. These structures are often present only on the females although the males typically initiate the attacks. For example, in the case of Platypus hintzi the mycangia consist of a pair of small hollows on the pronotum. In contrast, P. wilsoni has numerous small punctures on the pronotum (Cook, 1977). Ito et al. (2004) suggested that P. quercivorus has mycangia similar to P. hintzi.

Male P. quercivorus initiate the attacks on the boles of host trees and excavate galleries for mating from June to October (Soné et al., 2000). Apparently the first entry holes bored by male beetles trigger a mass attack (Kobayashi and Ueda, 2003). The attacks generally occur near ground level (Hijii et al., 1991). A single female joins the male and constructs the oviposition gallery after mating. This is kept clean by the male who expels the residues to the outside of the tree. During gallery construction, the females inoculate the gallery surface with spores of the ambrosia fungus, which the larvae feed on. The adult females begin to deposit eggs at the terminal parts of the tunnels, 2 to 3 weeks after gallery construction begins. The eggs are deposited in individual niches. An average of 50 to 60 larvae develop in a single gallery system but the number of larvae can be as high as 161. The larvae feed on the ambrosia fungus that develops on the walls of the galleries. Pupation occurs in the larval galleries. The majority of new adults leave their maternal galleries in September and October but some adults remain in the galleries until the spring and then die. In other cases the larvae reach the fifth-instar by late November and overwinter in pupal chambers. Pupation begins in the following May and the adults emerge in June and July. They emerge through entry holes made by the parents (Soné et al., 1998).

In Japan, Quercus mongolica and Quercus serrata that are mass-attacked by P. quercivorus, are usually killed later in the summer. Two fungi have been recovered from trees attacked by this insect and described as new species. Ophiostoma longicollum was described from Q. mongolica infested by P. quercivorus in 1998 (Masuya et al., 1998). The fungus, Raffaelea quercivora was isolated from discoloured sapwood, necrotic inner bark, the body surfaces of beetles, female beetle's mycangia and beetle galleries of symptomatic trees in 2002. Inoculation tests indicated that R. quercivora is the causal agent of Japanese oak disease and P. quercivorus is its vector. This is the first known occurrence of mass-mortality of trees in the family Fagaceae, caused by a species of Platypus and an associated ambrosia fungus of the genus Raffaelea (Ito et al., unda).

Notes on Natural Enemies

Top of page No natural enemies have been reported.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Leaves
Roots
Seedlings/Micropropagated plants
True seeds (inc. grain)
Wood

Wood Packaging

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Impact

Top of page Direct damage caused by P. quercivorus is associated with galleries constructed in the wood of host trees during breeding attacks. This can result in the loss of structural integrity in the wood and loss of lumber quality.

Since the early 1980s, extensive mortality of oak forests has been reported from western Japan (Kaneko, 1995). This condition, referred to as Japanese oak disease, is now attributed to the fungus Raffaelea quercivora, an anamorphic Ascomycete, which is a fungal associate of P. quercivorus (Ito et al., unda). The mortality of oak trees, at a rate of more than 200,000 per year, has been observed in the western coastal areas of Honshu, Japan (EPPO, 2003). The deciduous species of oaks, Quercus serrata and Quercus mongolica are susceptible to the disease. Other trees of the family Fagaceae that are present in the area, e.g. Quercus acutissima, Quercus acuta, Quercus phillyraeoides and Castanopsis sieboldii, are apparently not affected by the fungus (Ito et al., unda). To date, the most severe tree mortality has occurred on the west coast of Honshu (Hamaguchi and Goto, 2003).

It has been postulated that oaks, which are resistant or tolerant to Raffaelea quercivora, co-evolved under a stable relationship between the tree, fungus and beetle during a long evolutionary process. Q. mongolica may not have been part of this co-evolution. This hypothesis is supported by the fact that P. quercivorus has the least preference for Q. mongolica but exhibits the highest reproductive success in this species. Therefore, P. quercivorus could spread more rapidly in stands with a high composition of Q. mongolica. The present oak dieback epidemic in Japan may have resulted from the warmer climate that began in the late 1980s. This facilitated the encounter of P. quercivorus and Q. mongolica, by allowing the beetle to extend its range to more northerly latitudes and higher altitudes (Kamata et al., 2002).

Environmental Impact

Top of page P. quercivorus, in combination with its associated ambrosia fungus, Raffaelea quercivora is capable of causing extensive tree mortality in oak forests dominated by Quercus mongolica and Quercus serrata. This could result in major environmental impacts such as the loss of biodiversity, changes in the species composition of forests, reduced acorn crops and the resultant adverse impacts on wildlife species that depend on these crops for food.

Detection and Inspection

Top of page Lumber, crating, pallets and dunnage made from oak should be inspected for ambrosia beetle galleries and an associated brown discoloration caused by Raffaelea quercivora. Infestations in standing trees can be detected by the presence of white boring dust near the root collar and late summer tree mortality.

Similarities to Other Species/Conditions

Top of page Most species of Platypus are similar in appearance. Species identification of ambrosia beetles (families Platypodidae and Scolytidae) must be carried out on the adults. A taxonomist, with expertise in the family Platypodidae, should identify specimens suspected of being exotic species of Platypus.

Prevention and Control

Top of page The management of Platypus spp. beetles includes the application of contact insecticide sprays to the bark of high value trees to prevent attack. Systemic insecticides can be applied to the soil or bark of infested trees. Attacks in harvested logs can be prevented by the timely removal of them from forested areas and rapid processing or debarking at the sawmill (Cibrián Tovar et al., 1995).

Pest management methods that are designed to reduce the rate of oak mortality caused by the combination of P. quercivorus and Raffaelea quercivora are being developed in Japan. Recent studies indicated that both P. quercivorus and its associated fungus can be controlled by the injection of NCS [metam-ammonium] (N-methyldithiocarbamate) into holes bored in the stems of host trees (Weng PuJin et al., 2000).

References

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Babuder G; Pohleven F, 1995. Fungal succession in the tunnels of ambrosia beetles in oak wood (Quercus sp.). Zbornik Gozdarstva in Lesarstva, Ljubljana, No. 47:241-254; 18 ref.

Beaver RA; Hsien-Tzung Shih, 2003. Checklist of Platypodidae (Coleoptera: Curculionoidea) from Taiwan. Plant Protection Bulletin 45:75-90.

Bright DE; Skidmore RE, 2002. A catalogue of Scolytidae and Platypodidae (Coleoptera), Supplement 2 (1995-1999). Ottawa, Canada: NRC Research Press, 523 pp.

Cibrián Tovar D; Méndez Montiel JT; Campos Bolaños R; Yates III HO; Flores Lara JE, 1995. Forest Insects of Mexico. Chapingo, México: Universidad Autonoma Chapingo. Subsecretaria Forestal y de Fauna Silvestre de la Secretaria de Agricultura y Recursos Hidraulicos, México. United States Department of Agriculture, Forest Service, USA. Natural Resources Canada, Canada. North American Forestry Commission, FAO, Publication 6.

Cook R, 1977. The biology of symbiotic fungi. London, UK: John Wiley and Sons.

Drooz AT, 1985. Insects of eastern forests. USDA Forest Service, Miscellaneous Publication 1339.

EPPO, 2003. Raffaelea quercivora (a lethal disease of oak in Japan). www.eppo.org/QUARANTINE/Alert_List/ Fungi/raffaelea.html.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm

Furniss RL; Carolin VM, 1977. Western Forest Insects. Washington DC, USA: US Department of Agriculture Forest Service, Miscellaneous Publication No. 1339.

Giménez RA; Etiennot RE, 2003. Host range of Platypus mutatus (Chapois, 1865) (Coleoptera: Platypodidae). Entomotropica, 18(2):89-94.

Hamaguchi K; Goto H, 2003. Molecular phylogenic relationships among populations of the ambrosia beetle, Platypus quercivorus, the vector insect of Japanese oak disease. Display Presentation D0321, Entomological Society of America, National Meeting, Cincinnati, Ohio, 28 October 2003.

Hijii N; Kajimura H; Urano T; Kinuura H; Itami H, 1991. The mass mortality of oak trees induced by Platypus quercivorus (Murayama) and Platypus calamus Blandford (Coleoptera: Platypodidae). The density and spatial distribution of attack by the beetles. Journal of the Japanese Forestry Society, 73(6):471-476

Ito S; Murata M; Kubono T; Yamada T, unda. Pathogenicity of Raffaelea quercivora associated with mass mortality of facaceous trees in Japan. Poster presentation, MIE University, Kamihamcho, Japan. On line: http://www.forestresearch.co.nz/PDF/11.20Itoetal.pdf.

Kamata N; Esaki K; Kato K; Igeta Y; Wada K, 2002. Potential impact of global warming on deciduous oak dieback caused by ambrosia fungus Raffaelea sp. carried by ambrosia beetle Platypus quercivorus (Coleoptera: Platypodidae) in Japan. Bulletin of Entomological Research, 92(2):119-126; 49 ref.

Kaneko S, 1995. Mass death of oaks in Japan. Paper presented at the IUFRO XX World Congress, 6-12 August 1995, Tampere, Finland.

Kobayashi M; Ueda A, 2003. Observation of mass attack and artificial reproduction in Platypus quercivorus (Murayama) (Coleoptera: Platypodidae). Japanese Journal of Applied Entomology and Zoology, 47(2):53-60.

Kuroda K; Yamada T, 1996. Discoloration of sapwood and blockage of xylem sap ascent in the trunks of wilting Quercus spp. following attack by Platypus quercivorus. Journal of the Japanese Forestry Society, 78(1):84-88; [With English figures and tables]; 17 ref.

Masuya H; Kaneko S; Yamaoka Y, 1998. A new Ophiostoma species isolated from Japanese oak infested by Platypus quercivorus. Mycoscience, 39(3):347-350; 14 ref.

Soné K; Mori T; Ide M, 1998. Life history of the oak borer, Platypus quercivorus (Murayama) (Coleoptera: Platypodidae). Applied Entomology and Zoology, 33(1):67-75; 17 ref.

Soné K; Uto K; Fukuyama S; Nagano T, 2000. Effects of attack time on the development and reproduction of the oak borer, Platypus quercivorus (Murayama). Japanese Journal of Applied Entomology and Zoology, 44(3):189-196; 13 ref.

Weng PuJin; Luo WenJian; Wang YuanPing, 2000. Studies on causes of death of oak in Japan and its prevention and cure. Journal of Zhejiang Forestry Science and Technology, 20(6):46-49, 53; 9 ref.

Wood SL, Bright Jr. DE, 1992. A catalog of Scolytidae and Platypodidae (Coleoptera), Part 2: Taxonomic Index. Provo, Utah, USA: Bringham Young University, Great Basin Naturalist Memoir No. 13.

Distribution Maps

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