Pitch canker disease: Fusarium circinatum (F. subglutinans f.sp. pini)
Pitch canker disease is caused by a fungus previously called Fusarium subglutinans f.sp. pini. But recent taxonomic studies have described it as Fusarium circinatum, teleomorph: Gibberella circinata (Nirenberg ; O'Donnell, 1998).
Pitch canker disease was first reported in North Carolina (US) in 1946. It was then introduced into California in 1986 where it has caused serious problems in natural stands of Pinus (mainly Monterey pine, Pinus radiata) and also in plantations of Christmas trees. It is present in many states in USA (Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Texas, Virginia). This fungus has also been reported in Haiti (1959), Mexico (1989), Japan (1990) and South Africa (1994, see EPPO RS 96/070). Considering the incidence and spread of pitch canker in Mexico, it has been suggested that Mexico could be a possible centre of origin of Fusarium circinatum.
In California, Pinus radiata is the most widely affected species. In south Africa, it causes a serious root disease on P. patula seedlings in forest nurseries. Many other pine species can be attacked (e.g. P. canariensis, P. elliottii, P. echinata, P. halepensis, P. rigida, P. palustris, P. ponderosa, P. pungens, P. strobus, P. taeda), as well as Douglas fir (Pseudotsuga menziesii). P. brutia and P. thunbergiana are reported to be resistant.
Symptoms are characterized by resinous exudation on the surface of shoots, branches, exposed roots and boles. Needles turn yellow to red and fall. The top of the tree and ultimately the entire tree may die.
The pathogen is associated with numerous insects. The following vector species have been identified: Ips paraconfusus, I. mexicanus, Conophthorus radiata, Ernobius punctulatus. Species like Pityophthorus nitidulus, P. setosus, P. carmeli, Ips plastographus are suspected to be vectors, as fungus spores are often found associated with them. Seed transmission has now been demonstrated in Pinus radiata (Storer et al., 1998), and it is stressed that it clearly represents a mechanism by which pitch canker can be transmitted over long distances and introduced into new areas.
So far, no effective control measures (fungicides or biological control agents) are available. In California, several measures are taken to prevent any further spread of the disease (disinfection of pruning tools, restrictions on the movement of wood (logs, chips, waste wood, firewood, logs) and on the movement of trees such as Monterey pine Christmas trees). It is reported that the fungus can survive in cut wood up to a year, and up to 8 weeks in the soil.
The use of resistant trees may be possible in the future, as recent experiments (Gordon, et al., 1998) have shown that resistance could be observed in some Monterey pines.
Gordon, T.R.; Wikler, K.R.; Clark, L.; Okamoto, D.; Storer, A.J.; Bonello, P. (1998) Resistance to pitch canker disease, caused by Fusarium subglutinans f.sp. pini, in Monterey pine (Pinus radiata).
Plant Pathology, 47(6), 706-711.
Nirenberg, H.; O'Donnell, K. (1998) New Fusarium species and combinations within the Gibberella fujikuroi species complex.
Mycologia, 90(3), 434-458.
Storer, A.J.; Gordon, T.R.; Clark, L. (1998) Association of the pitch canker fungus, Fusarium subglutinans f.sp. pini, with Monterey pine seeds and seedlings in California.
Plant Pathology, 47(5), 649-656.
http://frap.cdf.ca.gov/pitch-canker/position_paper.html (Position paper. Transport, disposal and use of woody material infested with the pine pitch canker fungus)
http://frap.cdf.ca.gov/pitch-canker/pitchan.html (Pitch canker in California)
http://frap.cdf.ca.gov/pitch-canker/treenotes.html (Current status of pitch canker in California)
http://frap.cdf.ca.gov/pitch-canker/grinch_fungus.html ('Grinch' fungus threatens Christmas trees)
http://frap.cdf.ca.gov/pitch-canker/cal_ag.html (Pitch canker kills pines, spreads to new species and regions)
http://18.104.22.168/people/usps/mppdd/Forest/pitchc.htm (Pitch canker - by G.M. Blakeslee, University of Florida)
http://www.up.ac.za/academic/fabi/tpcp/diagnostics/pitchcanker.htm (South African Data Sheet on pitch canker)