Approach to Blue Stain Fungi on ISPM 15-Certified Wood Packaging in Australia

2012 IFQRG-10-11

Approach to blue stain fungi on ISPM 15-certified wood packaging in Australia

Christopher HowardGrains and Forestry Branch, Department of Agriculture, Fisheries and Forestry, Canberra, Australia.

Leisa PorterPlant Quarantine Operations, Department of Agriculture, Fisheries and Forestry, Canberra, Australia.

Vanessa Brake, Jennifer Morrison, Bernd Sunderhauf

Quarantine and Export Operations, Department of Agriculture, Fisheries and Forestry, Brisbane, Australia.

Abstract

Actioning of ISPM 15-certified wood packaging that presented with active blue stain fungi was ceased by the Department of Agriculture, Fisheries and Forestry in June 2012. This was because only a small proportion of wood packaging was being inspected, blue stain fungi may be present in wood packaging without blue stain symptoms and the quarantine pest status of blue stain fungi entering Australia is not known. Based on discussions with experts on blue stain fungi at IFQRG9 in Canberra, Australia, there is little evidence to support a pathway for exotic blue stain fungi species to move or be transferred off ISPM 15-treated wood packaging and establish in the environment.

Background

Blue staining of wood is commonly caused by fungal infection of the sapwood of trees following wounding by bark beetle vectors (Jacobs & Wingfield 2001; Schmidt 2006). While staining does not affect the integrity of the timber, the commercial value of the timber is reduced due to the discolouration. Blue stain fungi have been commonly described in the genera Ceratocystis, Ophiostoma and Leptographium. Most blue stain fungi do not cause disease in their hosts but some species within these genera are important plant pathogens and have caused widespread damage in forests and natural ecosystems and amenity settings. For example, since the introduction of the causal agent of Dutch elm disease, O. ulmi, to the USA in 1930, approximately 56% of the forest and amenity trees were killed or destroyed in a 46 year period (Huntley 1982; Hubbes 1999). In addition, following a second outbreak of Dutch elm disease in the UK in the 1960s caused by O. novo-ulmi, approximately two thirds of the UK elm population was lost within a decade (Brasier 1996).

Several species within these genera have been associated with blue staining in Australian hardwood speciesand some exotic softwood species that are used in the Australian forestry industry (Aghayeva et al. 2004; Heath et al. 2009; Roux & Wingfield 2009; Romon et al. 2007; Zhou et al. 2004). However, the knowledge of the species of blue stain fungi currently present in Australia is limited. Some targeted studies in Australia using artificial wounding to simulate thinning operations and surveys of wounds created by birds, wood-boring insects or harvesting operations have obtained new records of blue stain fungi-related organisms from hardwood plantations and natural forests (Kile et al. 1996; van Wyk et al. 2007; Kamgan Nkuekam et al. 2011a; Kamgan Nkuekam et al. 2011b). Currently, rapid identification of blue stain fungi species is difficult due to the time required to isolate and culture the fungi and the high-level of morphological taxonomic skills required to make the identification. Molecular-based approaches to species identification of active blue stain fungi exist (Khadempour et al. 2010; Roe et al. 2010), but these promising methods still rely on a time consuming isolation and culture phase.

Biosecurity concerns in Australia

In Australia, the main biosecurity concern with blue stain fungi has been with wood packaging (Zahid et al. 2008). The United Nations Food and Agriculture Organization develops the International Standards for Phytosanitary Measures (ISPM) to facilitate international trade and address quarantine risk. The standard for ‘Regulation of Wood Packaging Material in International Trade’, ISPM 15, specifies methyl bromide fumigation or heat treatment to address the risk of insect pests and pine wilt nematode in wood packaging at the time of manufacture. The ISPM 15 treatments were not developed to address fungal risks. Some fungi, including those related to species that cause blue staining, can survive the ISPM 15 heat treatment (Ramsfield et al. 2010). In fact, the currently accepted ISPM 15 heat treatment (minimum core temperature of 56o for 30 min) produces conditions in the timber conducive to the growth and survival of blue stain fungi (Lambertz & Welling 2010). These studies suggest that blue stain fungi are often present in wood and develop under suitable conditions of temperature and moisture while the wood packaging is in service.

Up to June 2012, Australia actioned ISPM 15-certified wood packaging found during inspection with active blue stain fungi, due to quarantine concerns over exotic blue stain fungi. However, only about 5% of wood packaging was being inspected, with the remainder being cleared on documents.

Review of quarantine status of blue stain fungi in Australia

The quarantine risk of blue stain fungi on ISPM treated wood packaging was discussed at the IFQRG Meeting in Canberra in 2011. It was noted that blue stain fungal taxa tended to be saprotrophic and widespread internationally. There was also agreement that blue stain fungi could only be transferred to other timber if beetles were present, as sticky spores prevent aerial dispersal and their dispersal via water is limited.

It is not known whether the active blue stain fungi that were being actioned on ISPM 15-certified wood packaging are already present in Australia. In order to determine the quarantine risk, baseline data is required on the blue stain fungi present on ISPM 15-certified wood packaging entering Australia. In addition, comprehensive information on the blue stain fungi present in both native and plantation timber ecosystems in Australia is needed to understand what species are exotic and present a quarantine risk.

As discussed at IFQRG9 in 2011, it is uncertain if there is a pathway for exotic species of blue stain fungi to move or be transferred off the ISPM 15 wood packaging and establish in the environment. As ISPM 15 treatments are designed to kill insects, it is unlikely that the exotic bark beetles vectors of blue stain fungi would be present on wood packaging after an ISPM 15 treatment. However, Australia does have native species of bark beetle (Neumann 1979) that are associated with blue stain fungi-related organisms in Australia (van Wyk et al. 2007; Kamgan Nkuekam et al. 2011a). As some insect vectors are attracted to the volatiles produced by relatives of blue stain fungi (Kile 1993), it is not known whether Australian native or established exotic bark beetles could be attracted to the volatiles produced by active blue stain fungi on wood packaging.

Recently, work commenced on identifying the species of blue stain fungi present on ISPM 15-certified wood packaging entering Australia. A diagnostic workshop on the Ophiostomatoid fungi was held for Department of Agriculture, Fisheries and Forestry Biosecurity officers in Brisbane, Australia, in October 2011. Twenty three isolates of blue stain fungi from imported wood, including 20 from wood packing, were identified using two sets of PCR sequencing primers. All isolates were identified as Ophiostoma species and included tentative identifications of Ophiostoma piceae, O. floccosum, O. quercus and O. piliferum. This workshop was a good beginning, but a concerted national approach is required before the risks, or otherwise, to Australia from exotic blue stain fungi can be determined.

New policy for active blue stain fungi on ISPM 15-certified wood packaging

Actioning of ISPM 15-certified wood packaging that presented with active blue stain fungi was ceased by the Department of Agriculture, Fisheries and Forestry in June 2012. This was because only a small proportion of wood packaging was being inspected, blue stain fungi may be present in wood packaging without blue stain symptoms, the quarantine pest status of blue stain fungi entering Australia is not known and uncertainty surrounds whether there is a pathway for exotic blue stain fungi species to move or be transferred off ISPM 15-treated wood packaging and establish in the environment. As a World Trade Organisation member, Australia is obliged to produce a technical justification for any measure for wood packaging in addition to those in ISPM 15. Until then, the actioning of ISPM 15-certified wood packaging based on the presence of active blue stain fungi has ceased.

References

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