- What is Pitch Canker?
- What Does Pitch Canker Look Like?
- Where is Pitch Canker Found?
- What Trees are Affected by Pitch Canker in California?
- Are All Susceptible Tree Species Affected To The Same Extent?
- What Causes Pitch Canker?
- How Does Pitch Canker Spread?
- Are There Trees That Do Not Get Pitch Canker?
- Is There a Cure For Pitch Canker?
- Will Pruning Infected Branches Slow The Decline of The Tree?
- Can I Prevent Pitch Canker From Getting Into My Trees?
- What Do I Do If I Think a Tree Has Pitch Canker?
- How Far Will Pitch Canker Spread?
- What Can I Do To Help?
- Where Can I Get More Information About Pitch Canker?
1. What is Pitch Canker?
Pitch Canker is a disease, which causes die-back of individual branches (figure 1), leading to a general decline in tree health, and, in some cases, premature death. This disease mainly affects pine trees in central coastal areas of California, but it has been found north of San Francisco in Mendocino County and as far south as San Diego County.
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TO LEFT: Fig 1. Multiple branch tip infections in Monterey pines grown on a golf course.
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2. What Does Pitch Canker Look Like?
The earliest symptoms of pitch canker are usually dead branch tips in the upper part of the tree canopy. Needles on the ends of these branches are either wilted (figure 2), red, dead or absent, and resin exudation is associated with the point of infection on the branch (figure 3). A more advanced symptom of the disease is the appearance of resinous cankers on the main stem and larger branches of the tree (figure 4). After the appearance of these stem cankers, the top of the tree may be killed by beetles, and death of the tree may result.
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ABOVE: Fig 2. Infected Monterey pine shoot. Discolored area of shoot is the lesion resulting from infection by the pathogen. Note the wilting of the tip of this shoot.
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ABOVE: Fig 3. Resin exudation from infected Monterey pine branch tip. Needles distal to the point of infection wilt and die.
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TO LEFT: Fig 4. Cankers on the main stem result in copious resin exudation.
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3. Where is Pitch Canker Found?
In the United States, prior to 1986, pitch canker was only known from the southeastern states. The disease was first recognized in California in 1986. It has also been found in various parts of the world, including Mexico, Japan and South Africa. Within California, pitch canker is limited to coastal areas, mostly from San Diego to Mendocino counties. To date there are no confirmed records of pitch canker from the Sierra Nevada or other locations east of the central valley, or farther north than Mendocino County.
4. What Trees are Affected by Pitch Canker in California?
Pitch canker affects many native pines in California, including Monterey pine, Bishop pine, knobcone pine, gray (=foothill) pine, coulter pine, Torrey pine, ponderosa pine, and shore pine. Douglas-fir, another native California conifer, is also susceptible, although less so than most pines. For ponderosa and Torrey pines, and Douglas-fir, naturally infected trees have been observed only in planted stands, and not in native forests.
5. Are All Susceptible Tree Species Affected To The Same Extent?
No. Of the native pines, Monterey and Bishop pine are the most widely affected. Knobcone pine and shore pine are also severely affected in some areas. Other native species are known to be susceptible, based on greenhouse tests, but are not common in the areas where pitch canker is found, and consequently infected trees are rarely seen. Among non-native pine species commonly found in landscape settings in California, Canary Island and Italian stone pines are relatively resistant to pitch canker. Allepo pine is intermediate in susceptibility.
6. What Causes Pitch Canker?
Pitch canker is caused by a fungus called Fusarium circinatum. Old names for this fungus include Fusarium subglutinans f. sp. pini, and Fusarium moniliforme var. subglutinans. Many other Fusarium species are commonly found in soil, some of which cause wilt diseases. Among the crops affected by Fusarium wilt disease are melons, cotton and tomatoes.
7. How Does Pitch Canker Spread?
The pathogen produces airborne spores that can be spread by wind, and carried by native insects.
Insects known to carry the pathogen include bark beetles and twig beetles, which feed under the bark of large and small diameter tree material respectively, and cone beetles, which attack cones on the host tree. Many of these insects are known to transmit the pitch canker fungus to healthy trees and are considered to be the primary means by which new infections are established. Although beetles can spread the disease to new areas, long distance spread is more likely to result from people transporting logs, nursery stock, seeds or soil, in which the pathogen is known to survive for long periods of time.
8. Are There Trees That Do Not Get Pitch Canker?
Yes. It has been shown that some Monterey pine trees are resistant to pitch canker. In addition, some trees in long term survey areas have only exhibited a very limited amount of damage caused by the fungus. These trees are not expected to die from the disease unless new strains of the fungus are introduced into the state and are able to overcome the natural levels of resistance which already exist.
9. Is There a Cure For Pitch Canker?
Because the fungus is inside the host tree, host trees are often large, and many insects are involved in the dissemination of the fungus, there are no practical direct methods of control of pitch canker. However, actions can be taken to slow the spread of the disease. These techniques reduce the number of insects emerging from plant material and carrying the pitch canker pathogen. These include debarking recently killed trees and branches, and timely chipping and removal of diseased or insect infested tree material from nearby susceptible trees.
10. Will Pruning Infected Branches Slow The Decline of The Tree?
In most areas where pitch canker occurs, infected branch tips are so numerous that it is not practical to remove them all. Even where this is possible, repeated pruning will be necessary, as new infections are likely to occur. In cases where the incidence of pitch canker is isolated, the timely removal of diseased branch tips may be effective in slowing the spread of the disease. It should be noted however that the benefits of this practice have not been demonstrated in full scale field studies.
11. Can I Prevent Pitch Canker From Getting Into My Trees?
There is currently no proven method for preventing pitch canker from infecting trees in areas where the fungus is established.
12. What Do I Do If I Think a Tree Has Pitch Canker?
If other trees in the area have pitch canker, there is little that can be done for individual trees. However, tree removal should only be considered if a tree becomes hazardous or unacceptably unsightly. Confirmation of the disease in trees requires isolation of the fungus, and details about this information can be obtained from your county agriculture commissioner’s office, or U.C. Cooperative Extension.
13. How Far Will Pitch Canker Spread?
Given the geographic range of susceptible host tree species, the potential for spread is great, and includes the northern coast of California and the Sierra Nevada. Work is underway to determine if climatic conditions, differences in host susceptibility or insect vectoring potential will limit disease spread.
14. What Can I Do To Help?
The biggest concern about pitch canker at the current time is the potential for the disease to spread into the forests of the Sierra Nevada. To help reduce the risk of this occurring, no Monterey pine or other pine material should be transported from West of Interstate 5 to East of Interstate 5. Any firewood, cones, logs, and chipped pine material should be utilized in the local area where it originated. These types of material may carry the fungus, its insect vectors, or both, and increase the risk of spread of the disease if transported outside of the local area.
15. Where Can I Get More Information About Pitch Canker?
A variety of information sources are available including printed documents, and information on the internet. Documents and links relating to pitch canker can be found at:
http://www.cnr.berkeley.edu/forestry/pitch.html
In addition, there is a growing source of information about the disease in the scientific literature. Some recent publications are listed below:
Gordon, Thomas R., Dorothy Okamoto, Andrew J. Storer, and David L. Wood. 1998. Susceptibility of five landscape pines to pitch canker disease, caused by Fusarium subglutinans f. sp. pini. Hortscience 33: 868-871.
Gordon, Thomas R., Karen R. Wikler, Andrew J. Storer, and David L. Wood. 1997. Pitch canker and its potential impacts on Monterey pine forests in California. Fremontia 25(2): 5-9.
Storer, Andrew J., Paul L. Dallara, David L. Wood and Thomas R. Gordon. 1995. Pitch Canker Disease of Pines. Calif. Dept. Forestry and Fire Protection, California Forestry Note. #220, 18p. http://frap.cdf.ca.gov/pitch_canker/pitchcan.html
Storer, Andrew J., Thomas R. Gordon, David L. Wood and Pierluigi Bonello. 1997. Current and future impacts of pitch canker disease of pines. Journal of Forestry 10(12): 21-26.
Information provided by University of California Cooperative Extension
Last updated August 2000
Andrew J. Storer
Assistant Research Entomologist
Division of Insect Biology
Department of Environmental Science, Policy and Management
University of California, Berkeley
contact:
storer@nature.berkeley.edu
David L. Wood
Professor of the Graduate School
Division of Insect Biology
Department of Environmental Science, Policy and Management
University of California, Berkeley.
Thomas R. Gordon
Professor of Plant Pathology
Department of Plant Pathology
University of California, Davis.
