Pitch canker, caused by the fungus Fusarium circinatum (teleomorph = Gibberella circinata), is a disease affecting many pine species and Douglas-fir. The most common symptom of pitch canker is dieback of branch tips, which results from girdling lesions.
Severely affected trees also develop resinous cankers on large branches and the main stem, leading to extensive canopy dieback and death of the entire tree in some cases. Pitch canker was first described in the southeastern U.S., as a disease of planted pines but the disease now has a worldwide distribution. In 1986, pitch canker was discovered in California, where it affects trees both in landscapes and native forests (1). Pinus radiata (Monterey pine), is the most widely affected species but P. muricata (bishop pine) and P. attenuata (knobcone pine) are also susceptible and have sustained significant damage in some areas. Most native California pines are susceptible to pitch canker but not all to the same degree. Even within susceptible species, some individuals will be resistant to the disease (2).
Studies conducted under controlled conditions showed that prior exposure to F. circinatum enhances resistance to subsequent challenge with the pathogen, relative to native trees. This phenomenon is known as systemic induced resistance (SIR) (3). Our studies of the pitch canker-Monterey pine pathosystem demonstrated that SIR is operative in native and planted stands of Pinus radiata, where it has contributed to a significant decline in the incidence and severity of disease (4). This appears to be the first documentation that SIR, which has been well studied under controlled conditions, actually occurs in nature.
1. Gordon T.R., Storer A.J., and Wood D.L. 2001. The pitch canker epidemic in California. Plant Disease 85: 1128-1139.
2. Gordon T.R., Wikler K.R., Clark S.L., Okamoto D., Storer A.J. and Bonello P. 1998. Resistance to pitch canker disease, caused by Fusarium subglutinans f. sp. pini, in Monterey pine (Pinus radiata). Plant Pathology 47:706-711.
3. Bonello P., Gordon T.R., and Storer A.J. 2001. Systemic induced resistance in Monterey pine. Forest Pathology 31:1-8.
4. Gordon T.R., Kirkpatrick S.C., Aegerter B.J., Fisher A.J., Storer A.J. and Wood D.L. 2011. Evidence for the occurrence of induced resistance to pitch canker, caused by Gibberella circinata (anamorph Fusarium circinatum), in populations of Pinus radiata. Forest Pathology 41:227–232.
5. Swett C.L. and Gordon T.R. 2012. First Report of Grass Species (Poaceae) as Naturally Occurring Hosts of the Pine Pathogen Gibberella circinata. Plant Disease 96:908.
6. Slinski, S.L., Zakharov, F., Gordon, T.R. 2015. The effect of resin and monoterpenes on spore germination and growth inFusarium circinatum. Phytopathology 105: 119-125.
7. Swett, C.L., Gordon, T.R. 2015. Endophytic association of the pine pathogen Fusarium circinatum with corn (Zea mays). Fungal Ecology 13: 120-129.