Pine pitch canker
| Fusarium circinatum | |
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| Pitch canker affecting western white pine | |
| Scientific classification | |
| Kingdom: | Fungi |
| Phylum: | Ascomycota |
| Class: | Sordariomycetes |
| Subclass: | Hypocreomycetidae |
| Order: | Hypocreales |
| Family: | Nectriaceae |
| Genus: | Fusarium |
| Species: | F. circinatum |
| Binomial name | |
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Fusarium circinatum Nirenberg & O'Donnell |
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| Synonyms | |
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Fusarium circinatum is a fungal plant pathogen that causes the serious disease pitch canker on pine trees. Like other Fusarium species in the phylum Ascomycota, it is the asexual reproductive state of the fungus and has a teleomorph, Gibberella circinata.
This fungus is believed to have originated in Mexico. It spread to the eastern United States in 1946 and by 1986 had reached the western United States. It was first recorded in Japan in the 1980s, in South Africa in 1990, in Chile and Spain in the mid 1990s and in Italy in 2007.
In California this canker has been recorded on nine different species of pine (Pinus) and on Douglas fir (Pseudotsuga menziesii). In Europe and Asia it has been recorded on over 30 other Pinus species. Monterey pine (Pinus radiata) seems to be the most susceptible species, and in California 85% of the native Monterey pine forests were initially thought to be threatened by the disease. Because of the activation of systemic acquired resistance in native Monterey pine trees, however, the impacts of the disease in California have been mitigated.
F. circinatum infects the twigs and branches of pine trees, causing a bark canker. Most infection is by macroconidia or microconidia. The macroconidia are 3-septate, with slightly curved walls and the microconidia are single-celled, ovoid, and borne in false heads on aerial polyphialides. The aerial mycelium is white or pale violet colour and slightly twisted below the proliferation of microconidiophores. In culture, perithecia are readily produced. They are dark purple or black and ovoid. Cylindrical asci are released by oozing. There are eight ascospores which are 1-septate and ellipsoidal to fusiform. Because peritheca have not been observed in the field, it is not thought that ascospores are an important route for infection.
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Wikipedia