Trachymela sloanei (Coleoptera: Chrysomelidae): addition to the EPPO Alert List
Why: Trachymela sloanei (Coleoptera: Chrysomelidae - Australian tortoise beetle) is a eucalyptus leaf feeder originating from Australia, which has been introduced into other parts of the world during the last decades. Outside its native range, T. sloanei was first detected in New Zealand (1976) and later in California (1998), where it rapidly spread to areas where eucalyptus are grown. Since the 2010s, its spread seems to have accelerated and new records of T. sloanei have made in several countries on different continents: Spain (2014), China (2018), Chile (2020), Portugal (2022), Taiwan (2023) and Greece (2023). Considering its rapid spread and invasive behaviour, the EPPO Secretariat considered that T. sloanei could usefully be added to the EPPO Alert List.
Where:
EPPO region: Greece, Portugal, Spain.
Asia: China (Fujian, Guangdong, Hong Kong), Taiwan.
North America: USA (Arizona, California, Hawaii).
South America: Chile.
Oceania: Australia (New South Wales, Queensland, South Australia, Victoria, Western Australia), New Zealand.
In the EPPO region, the first specimens of T. sloanei were collected in 2014 in Spain, in Jerez de la Frontera (province of Cádiz, Andalucía). Further studies (field surveys and consultation of citizen science platforms) conducted in the Iberian Peninsula detected the insect in other locations in Andalucía, Extremadura (Cáceres) and Madrid, as well as in Southern Portugal. T. sloanei was mainly found in eucalyptus plantations and isolated trees in the natural environment, but also in ornamental trees in urban environments. On Internet fora and citizen science platforms, there are indications that T. sloanei has recently been observed in other areas in Spain, in Comunidad Valenciana and Canary Islands. Finally, the most recent record was made in Greece in 2023, where insect specimens were collected from the city of Piraeus (Attica) on E. camaldulensis trees in a park.
On which plants: T. sloanei feeds on numerous species of eucalyptus (e.g. Corymbia citriodora, C. ficifolia, C. maculata, E. camaldulensis, E. crenulata, E. globulus, E. grandis, E. propinqua, E. robusta), with a preference for Eucalyptus camaldulensis.
Damage: Adults and larvae feed on eucalyptus leaves and young stems, usually at night. Signs of infestations are irregular notches and semicircular holes along leaf edges, leaving the midvein. Heavy infestations can lead to defoliation, but no tree mortality has been reported in the invaded range.
Adults (6-7 mm long) have a hemispherical brown body with black spots and red wings. The presence of a row of fine hairs on the outer margin in the distal half of the mid- and hind- tibia is a distinctive characteristic for this species. Female lay 5 to 40 eggs (or more) on leaves or under loose bark. Larvae are dark green to reddish brown and develop through 4 stages before pupation takes place beneath loose bark or in the soil/litter around the base of host trees. The insect has several generations per year. In California, development time from egg to adult could be as short as 5 weeks under warm weather conditions.
Pictures can be viewed on the Internet:
Dissemination: Adults can fly, but data is generally lacking about their flight capacity. However, this insect seems to be able to spread rather rapidly. Although the introduction pathways from one continent to the other have not been identified, human activities (e.g. travel, trade) are probably playing an important role.
Pathways: Plants for planting, cut foliage of Corymbia and Eucalyptus species from countries where T. sloanei occurs.
Possible risks: Eucalyptus are grown in the EPPO region for forestry, amenity, paper industry and ornamental purposes, in particular around the Mediterranean Basin. T. sloanei is difficult to observe in the field or on consignments as all its life stages are cryptic. Beetles and larvae typically remain hidden on or in the bark of eucalyptus trees during the day. Little information is available about control measures, but natural enemies could probably play an important role in limiting pest populations. In New Zealand, following its introduction extensive defoliation and tree damage were observed before its populations were brought under control by natural enemies. Both adults and larvae are voracious leaf feeders and defoliation exerts significant tree stress, but its impact on tree growth and the resulting economic impact on eucalyptus production remain to be clarified. Finally, it can be noted that T. sloanei is another addition to an already long list of alien pests of eucalyptus recently introduced into the EPPO region (e.g. Blastopsylla occidentalis, Ctenarytaina eucalypti, C. spatulata, Glycaspis brimblecombei, Leptocybe invasa, Ophelimus maskelli, Thaumastocoris peregrinus).
Sources
Bain J (2009) New records. Forest Health News no. 194. https://www.scionresearch.com/__data/assets/pdf_file/0009/3897/fhnewsNo194-April09.pdf
Gastouniotis G, Kakiopoulos G, Gastouniotis P (2023) First records of Trachymela sloanei (Blackburn, 1896) (Coleoptera, Chrysomelidae) in Greece. Parnassiana Archives 11, 77-79. https://doi.org/10.1111/jen.13086
INTERNET
- Atlas of Living Australia. Trachymela sloanei (Blackburn, 1896). https://bie.ala.org.au/species/https://biodiversity.org.au/afd/taxa/152eaba4-489e-4155-ab31-687b49116d6a
- Los Angeles County Agricultural Commissioner’s Office. Australian tortoise beetle (Trachymela sloanei) by N. von Ellenrieder (dated September 2023). https://www.sandiegocounty.gov/content/dam/sdc/common_components/images/awm/Docs/ipd_austtortbeetle.pdf
- TaiCOL (online database) Catalogue of Life in Taiwan. Trachymela sloanei. https://taicol.tw/en-us/taxon/t0099217#taxon-status
- University of California Agriculture and Natural Resources. U. IPM. Eucalyptus tortoise beetles. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74104.html
Matsunaga JN, Howarth FG, Kumashiro BR (2019) New state records and additions to the alien terrestrial arthropod fauna in the Hawaiian Islands. Proceedings of the Hawaiian Entomological Society 51(1), 1-71. https://scholarspace.manoa.hawaii.edu/server/api/core/bitstreams/f57fe030-c574-4cb9-91d3-548c993b5b3d/content
Millar JG, Paine TD, Bethke JA, Garrison RW, Campbell KA, Dreistadt SH (2009) Eucalyptus tortoise beetles. Pest Notes Publication 74104. University of California Agriculture and Natural Resources, 5 pp. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74104.html
Millar JG, Paine TD, Hoddle M (2000) Biological control of a newly introduced pest, the eucalyptus tortoise beetle, Trachymela sloanei. Slosson Report 1999-2000 (University of California), 1-7. https://slosson.ucdavis.edu/newsletters/Millar_200029040.pdf
Pérez-Gómez Á, Robla J, Barreda JM, Rodríguez G, Amarillo JM (2022) Updating new invasions: The Australian tortoise beetle Trachymela sloanei (Blackburn, 1897) (Coleoptera: Chrysomelidae) in the Iberian Peninsula. Journal of Applied Entomology 146, 1217–1223.
Riley EG, Clark CM, Gilbert AJ (2001) New records, nomenclatural changes, and taxonomic notes for select North American leaf beetles (Coleoptera: Chrysomelidae). Insecta Mundi, 176. http://digitalcommons.unl.edu/insectamundi/176
Sánchez I, Amarillo JM, Molina D (2015) [First records of Trachymela sloanei (Blackburn, 1897) (Coleoptera, Chrysomelidae) in Europe]. Revista gaditana de Entomología 6(1), 127-130 (in Spanish).
Villablanca J, Villablanca-Miranda V (2022) First record of Trachymela sloanei (Blackburn, 1897) (Coleoptera: Chrysomelidae) in Chile. Revista Chilena de Entomología 48(3), 525-529. https://www.biotaxa.org/rce/article/view/76385
Zhang M, Chen X, Ruan Y, Jiang S, Yang J, Jiang M, Ruan X, Li Y (2020) First report of the invasive Australian tortoise beetle Trachymela sloanei (Coleoptera: Chrysomelidae: Chrysomelinae) in Asia. Journal of Asia-Pacific Entomology 23, 442-444.