Hylesia nigricans (Lepidoptera : Saturniidae, Hemileucinae) – a tree and public health pest native to South America, intercepted on motor vehicles imported into Australia.
David Rees, John Nielsen, Plant Biosecurity, Department of Agriculture, Fisheries and Forestry, Canberra, ACT, Australia.
Ross Rickard, Operation Science Program, Australian Quarantine Inspection Service, Department of Agriculture, Fisheries and Forestry, Sydney, NSW, Australia.
Silvia Passalacqua, Marcelo Sanchez, Coordinadora de Bioseguridad Agroambiental, Dirección Nacional de Protección Vegetal, Servicio Nacional de Sanidad y Calidad Agroalimentaria (SENASA), Buenos Aires, Argentina.
Large numbers of egg masses of the moth Hylesia nigricans (Lepidoptera: Saturniidae, Hemileucinae) were found on new motor vehicles imported from Argentina in February 2011. This moth is native to sub-tropical and temperate SE Brazil, Uruguay and NE Argentina. It has a wide host range, including many genera native to Australia and is an important public health pest due to the detachable irritant abdominal hairs on female moths. Hylesia nigricans is not known in Australia and poses a significant biosecurity and public health threat to Australia. Vehicles were found to have been contaminated while being stored at the port of Zarate, Argentina prior to shipment. Hylesia nigricans is a well known inhabitant of the area, infesting riverine forests and suburban areas. Moths are likely to have been attracted to the port facility by extensive site lighting. Proposed management measures include reducing lighting in vehicle storage areas during periods of high moth activity, converting site lighting to a type that produces little or no blue or long wavelength UV radiation (300 – 500 nm), minimising storage of vehicles at the port during the flight period and using hail netting to minimise contamination.
In February 2011, the Australian Quarantine and Inspection Service (AQIS) inspected a ship arriving at Port Kembla, New South Wales, carrying new vehicles. Included in the load were 354 new vehicles that had been loaded in Argentina, of which 229 were contaminated with egg masses of an unknown moth, together with a few dead moths. These were attached to tyres, wipers, engine compartments and plenum chambers, as well as on paintwork and in door jams of the vehicles (Figures 2-4). Two more ships arrived in the following weeks with more vehicles from Argentina, some of which were also contaminated. In total, about 800 vehicles were involved in three shipments, of which 60% were contaminated with egg masses.
An initial identification of the dead adults and egg masses (Figures 4 and5) were made by Plant Biosecurity staff as Hylesia spp. (Lepidoptera : Saturniidae, Hemileucinae), probably Hylesia nigricans (Berg). This was subsequently confirmed by taxonomists at CSIRO Australia and the University of Cordoba, Argentina and backed up later by molecular analysis by AQIS.
The genus Hylesia is indigenous to South America and about 110 species of this genus are known, which occur from Mexico south to Argentina (Lemaire 2002). Hylesia spp. are not known to occur in Australia and are not currently known to occur outside of the Americas.
Ecology and status of Hylesia nigricans
Hylesia nigricans appears to be is the most southerly distributed species of the genus. It is known to occur in south eastern Brazil (Rio Grande do Sul), Uruguay and Argentina (Specht et al. 2006) (Figure 1). In Argentina, it is known from the north east, including the city of Buenos Aires and the provinces of Buenos Aires, Entre Rios and Missiones (Salomon et al. 2005, de Roodt et al. 2000).
Hylesia nigricans feeds on a wide range of native and introduced tree species, including Acer (Aceraceae), Ilex (Aquifioliaceae), Carprinus (Betulaceae), Patagonula (Boraginaceae), Tipuana (Cesalpiniaceae), Quercus (Fagaceae), Carya (Juglandaceae), Ocotea (Lauraceae) and Acacia (Mimoseae) with leaves in the host tree (Specht et al. 2006).
In Argentina, Hylesia nigricans was first declared a ‘national pest of Agriculture’ in 1911, and it is known to produce episodic outbreaks on street trees of Platanus, Fraxinus, Acer, Quecus, Prunus and Liquidambar (Salomon et al. 2005). In addition to attacking street and fruit trees, Hylesia nigricans is known to be a public health pest, principally on account of the irritant abdominal hairs on female moths (Salomon et al. 2005). These hairs are detachable and are used by the female to cover and protect eggs when laid.
On warm summer evenings, adult Hylesia can be attracted at night to illuminated areas including campsites, picnic grounds, cafes, street lights, domestic premises, ports and other worksites operating at night (Salomon et al. 2005). As moths fly around lights and rub against surfaces the irritant abdominal hairs become liberated. They contaminate surfaces or blow about on the wind. These hairs are sharp and are, in effect, a micro-syringe containing histamine. When they come into contact with human skin or are inhaled they cause a severe allergic reaction.
Other species of Hylesia, for example Hylesia metabus that occurs in coastal areas of Venezuela and neighbouring countries and Hylesia alinda that occurs in the state of Quintana Roo in SE Mexico, are also public health pests.
The origin of egg masses of Hylesia nigricans found on imported vehicles
In June 2011, a visit was made by staff of Servico Nacional de Sanidad y Calidiad Agroalimentaria (SENASA) and AQIS/Biosecurity Australia to the port of Zarate, Argentina from where vehicles found contaminated with egg masses had been dispatched. The port is a modern purpose built facility that mainly handles new motor vehicles but also has a container port. It is about 90km northwest of Buenos Aires on the bank of the Rio Paraná. The facility is in a semi rural area about one kilometre from the outskirts of the city of Zarate.
Examination was made of the parking lots and related infrastructure that were used to hold and accumulate vehicles prior to shipping to Australia. At the time of the visit, it was expected that any H. nigricans present would be in the egg stage and that evidence of eggs laid during the previous summer may be present at the site.
Several egg masses of H. nigricans were found on the external structure of a building used for vehicle preparation that was surrounded by parking lots (Figure 9). Numerous egg masses were found on a mobile light unit used to illuminate a car storage area (Figures 10 and 11). Egg masses were found on the inside surfaces of its wheels and under mud guards. Numerous weathered egg masses were found on fence posts and fencing nearby (Figure 12). A dead male H. nigricans was found on the grass below (Figure 13). Egg masses were also seen attached to electrical service boxes on floodlights 10 m above ground (Figure 14).
Egg masses laid on exposed man-made surfaces mostly appeared to have been laid ‘in distress’, as indicated by their irregular shape and size.
Trees were examined that were growing along the riverside close to the port (Figure 15). Many viable egg masses were on found on trunks and branches of willows (probably Salix humboltiana) growing there. Egg masses on trees were carefully laid as neat mounds fully covered with protective abdominal hairs (Figures 16 and 17).
From the quantity of egg masses found during the site inspection, it is clear that large numbers of moths had been attracted to the site, presumably by the extensive site lighting. The port complex is, in effect, an isolated ‘light island’ surrounded by suitable habitat, such as riverbanks, suburban sub-divisions, farmland and plantations. The port is at high risk of being swamped on warm nights by large numbers of flying insects attracted to the lights.
Hylesia nigricans appear to be strong fliers. Egg masses were found in places at least 500 m from the nearest tree. Viable egg masses were found on willows on the site. Examination of geo-tagged photos via Google Earth indicates that similar willows line the complex of delta waterways leading into the Rio Paraná to the north of the port site. It was noted that local print media in Zarate reported that the moth was a significant problem for local residents during summer (Anon 2010).
Potential risk to Australia from Hylesia nigricans
The arrival of viable egg masses in Australia attached to vehicles loaded in Argentina and transported under commercial conditions demonstrates that H. nigricans can be moved from South America to Australia.
Northeast Argentina and south eastern Australia are roughly on the same latitude in the same hemisphere and share simular climates. Eggs transhipped to southern Australia from warm temperate South America do not face a seasonal shock in terms of climatic conditions or day length that they would likely face had they been transported to the northern hemisphere. Most species of deciduous trees attacked by H. nigricans, for example, poplars, oaks, plane and apples, are widely grown in southern Australia as crop, amenity, shade and street trees. Others, such as willows, are widespread environmental weeds in Australia. Hylesia nigricans is known to attack Eucalyptus spp., a keystone genera of the natural environment of Australia.
It is also possible that eggs of H. nigricans could be transported on objects other than motor vehicles, such as shipping containers. Motor vehicles are a particular risk, given that after importation, they are distributed and used widely in the general environment. In contrast, shipping containers have a more limited pattern of distribution and use and are likely to be re-exported. Motor vehicles are more complex structures than shipping containers and there are many places where a moth could conceal an egg mass, as has been demonstrated. When eggs hatch in the spring, it is likely that larvae will be close to suitable hosts, such as the trees that commonly line suburban streets in southern Australia.
In its natural range, H. nigricans is known for episodic outbreaks (de Roodt et al. 2000, Salomon et al. 2005). With the same host species available and a similar climate but no co-adapted enemies, H. nigricans could become a significant pest of crop and amenity trees and natural forests in coastal/humid temperate and sub tropical Australia. If it were to do so, it would likely become a significant public health pest that disrupts evening outdoor recreational and work related activities at the height of summer.
While adult moths come readily to light, their indistinct appearance and the presence of other non target species may not alert untrained persons to their importance. Sex pheromones, when used in a suitable trap, could act as a specific means to monitor the presence of this species. However, such pheromones do not appear to have been identified and synthesised and do not appear to be commercially available.
Suggested management measures
The port, with its associated lighting infrastructure, is surrounded by unlit or poorly lit river and semi rural areas. The facility is in effect a ‘light island’ and as a consequence is subject to inundation by flying insects including H. nigricans. The risk of vehicles becoming contaminated with egg masses of H. nigricans is restricted to the short period when moths are active and attracted to lights at the port. This is likely to occur between late December and early March.
Management measures should seek initially to reduce the attraction of the site to moths. During periods of high moth activity, lighting in vehicle storage areas could be reduced to the minimum required for security and safe work. It may be possible to convert site lighting to a type that produces little or no blue or long wavelength UV radiation (300-500 nm) that is highly attractive to flying insects. For example, sodium based lights produce a mostly yellow light that is relatively unattractive to insects.
Netting (roughly 1cm square mesh) is used in some areas to protect parked vehicles from hail damage. This material is likely to hinder the passage of moths. Additional protection is likely to be achieved if sides, front and back of the netted areas are also screened, especially those areas that face light sources. Production for export to sensitive markets could be scheduled to minimise vehicles being stored and handled at the port during the ‘flight period’.
Commercial pressure washing and application of pesticide to contaminated vehicles has been demonstrated by AQIS to be ineffective in removing or killing the egg masses, given the difficulty in gaining access to all location where egg masses can be concealed. Treatment with fumigants is problematic as available gases, methyl bromide and phosphine, can cause damage to vehicles.
Currently, vehicles found to be contaminated with egg masses of moths on arrival in Australia are heat treated to ensure that all parts of the vehicle reach 60oC for a minimum of 10 minutes. This treatment is based on advice provided by Biosecurity New Zealand, Ministry of Agriculture and Forestry, New Zealand, to control eggs masses of Gypsy moths (Lymantria spp. Lepidoptera - Lymantriidae). Tests should be undertaken to confirm that this regime is effective for egg masses of H. nigricans.
Sex pheromones for Hylesia spp. need to be identified, with a view to be able to produce lures for monitoring this species. Currently, no specific trap is available for these moths.
In many ways, the situation with Hylesia nigricans is analogous to that of the much better known Asian Gypsy moths (Lymantria spp.). In both cases, they are polyphagous moths that feed on a large number of tree species and lay over-wintering egg masses on a variety of surfaces, including man-made objects that are moved and traded between continents. Hylesia nigricans has significant potential as a pest in new areas, especially other temperate areas in the southern hemisphere.
The authors would like to acknowledge the assistance of Ing. Agr. Diego Quiroga, National Director, Plant Protection, SENASA, Ing. Agr. Pablo Cortese, Surveillance and Monitoring Director, SENASA. Linguistic support was provided by Monica Amadeo.
We wish to acknowledge the advice and assistance of: Dr Eduardo Botto, Instituto Nacional Tecnologia Agropecuaria, Castelar, Buenos Aires; Dr Oscar Salomon, Centro Nacional de Diagnóstico e Investigación en Endemo Epidemias, Ministry of Health, Buenos Aires; and Gerado Liljesthrom, Matria Babriela Luna, Fernanda Cingolani and Norma Sanchez, Centro de Estudios Parasitologicos y Vectores / Consejo Nacional de Investigaciones Científicas y Técnicas, La Plata, Argentina.
Anon (2010) Preocupación por la invasión de las Mariposas Negras, El Diario de Zarate, Zarate, Argentina, 19 Jan 2010, www.eldebate.com.ar.
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Figure 1 Estimated geographical distribution of Hylesia nigricans
Figure 2 Egg masses of Hylesia nigricans on tyre of an imported vehicle on arrival in Australia
Figure 3 Egg masses of Hylesia nigricans found in door jams and handles of imported vehicle
Figure 4 Viable egg mass of Hylesia nigricans collected on protective packaging from an imported vehicle on arrival in Australia
Figure 5 Dead adults of Hylesia nigricans found in imported vehicles on arrival in Australia
Figure 6 Port of Zarate – aerial view
Figure 7 General view of vehicle holding facilities at Zarate – note floodlights
Figure 8 Car storage yard with hail netting – mesh about 1 cm square
Figure 9 Egg masses of Hylesia nigricans attached to metal support of building in car holding yard
Figure 10 Inspecting a mobile flood light unit in a vehicle holding yard
Figure 11 Egg masses of Hylesia nigricans attached to inner surface of wheels of the mobile lighting unit
Figure 12 Fence post close to site of mobile flood light unit with many weathered Hylesia nigricans egg masses
Figure 13 Dead male adult Hylesia nigricans found at base of fence post above
Figure 14 Egg masses of Hylesia nigricans on floodlights at Zarate
Figure 15 View of quayside on Rio Parana at Zarate – note trees (mostly Salix) along riverbank
Figure 16 Egg masses of Hylesia nigricans on willow on bank of Rio Parana at Zarate
Figure 17 Egg masses of Hylesia nigricans on willow on bank of Rio Parana at Zarate