It is now globally recognised that the Pitch Canker Fungus, Fusarium circinatum, may be regarded as one of the most serious threats to the softwood industry.
In response to this growing threat, the Pine Fusarium Working Group (PFWG) was formed in South Africa in 2000, consisting predominantly of nurserymen and researchers from the various South African forestry companies and organisations, aimed at ensuring the viability of all commercially grown pine species in South Africa with respect to Fusarium circinatum.
In South Africa, Fusarium circinatum has characteristically been a nursery pathogen, attacking primarily Pinus patula and Pinus radiata seedlings and cuttings. Fusarium-related field mortality soon after out-planting has been observed and is of concern for many South African forestry companies. With recent, isolated outbreaks of pitch canker in mature stands of P. patula, P. greggii and P. radiata, the management and monitoring of this fungal pathogen has become critical.
Fusarium circinatum is an Ascomycete fungus closely related to mango and maize pathogens, and forms part of the Fusarium subglutinans complex found specific to Pinus spp, causing the Pitch canker disease of mature pine in USA.
It is believed that the fungus originated in Mexico where it spread to the South-East USA (1946), Western USA (1985), Japan (1989), South Africa (1990) and more recently to Chile (2001), Spain (2003), Italy (2005 ) and Portugal (2007). While it has been predominantly observed in the field elsewhere, it was first reported in conifer nurseries in South Africa and Chile. In the USA, the pathogen has reached epic proportions, severely affecting mature stands.
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Fusarium circinatum is now found in all South African pine-growing nurseries.
Symptoms in the nursery appear approximately four months after sowing and plant death occurs within a month.
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In mature stands in the USA, the pathogen is spread predominantly by insect vectors. In South Africa, field infections have occurred as isolated incidents, closely associated with various stress factors and in geographically isolated areas.
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In South Africa, in 2000, the Pine Fusarium Working Group (PFWG) was formed consisting mainly of Nurserymen and Researchers from various South African Forestry companies and research organisations.
The Aim:
To ensure the viability of all commercially grown pine species in South Africa with respect to Fusarium circinatum.
Strategic Initiatives
- To ensure the long-term availability of commercial Pinus species, for future afforestation
- To build a knowledge base regarding Fusarium circinatum and distribute this information to pine growers in South Africa
- To develop practical guidelines and protocols for the successful establishment of commercial pine species in South Africa
- To work with the Seedling Growers Association of South Africa in promoting a standard of nursery hygiene through annual nursery certification audits. (For more information visit www.sgasa.co.za)
- To facilitate and conduct research to support operational initiatives designed to manage the pathogen, and reduce the impact and risk to to South African commercial pine plantations.
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The Pine Fusarium Working Group has a number of short-term initiatives underway to manage F. circinatum in the nursery and at planting, and in the field in mature stands.
Managing Fusarium in the Nursery and at Planting
Current management strategies in the Nursery include maintaining strict hygiene, combined with the responsible use of fungicides and controlling plant movement.
Managing Fusarium in the Field (Pitch canker outbreaks in mature pine)
It has been reported that most of the commercial pine species are affected by the pathogen, with Pinus radiata being one of the most susceptible. Pinus patula is regarded as moderately susceptible with Pinus elliottii and Pinus tecunumanii showing reasonable tolerance. Pinus oocarpa and Pinus jaliscana have been shwon to be the most tolerant species.
Long-term initiatives include selection and breeding, for tolerance to the pathogen. In South Africa, this is through the hybridisation of P. patula with the more tolerant species such as P. tecunumanii and P. oocarpa, by indentification and propagation of tolerant families of P. patula, or by a combination of these two strategies.
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Monitoring
Monitoring is critical to facilitate the early detection and subsequent intervention for future pitch canker outbreaks in South Africa, while also providing information on the spread and intensity of the pathogen across the country.
Awareness
Awareness initiatives are aimed at informing al relevant stakeholders of knowledge and information on managaing Fusarium circinatum, as well as how to identify possible outbreaks.
In partnership with the Southern African Institute of Forestry (SAIF) the PFWG has produced a set of cards aimed at assisting with the identification of symptoms assocated both with Fusarium circinatum in the nursery (insert link) and Pitch Canker in mature pine in the field (insert link).
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