Monday, August 20, 2012

More on cankers

Scleroderris canker

Scleroderris canker caused by the fungus, Gremmeniella abietina.

Scleroderris canker has killed many trees in conifer plantations and forest nurseries in the northern areas of the Lake States. The fungus can be transported on nursery stock to field locations where new pockets of infection develop. Two strains of the fungus are known in North America. The North American strain, present in scattered locations in the northern Lake States and Northeastern States, attacks young trees but does little damage to trees taller than 7 feet (see below, left photo). The European strain has been found in several New England States where it has killed many trees of all ages in red pine plantations (see below right photo). The European strain is an extremely serious hazard to pine forests. Because of this potential hazard, forest managers in the Lake States need to know how to avoid major losses from this disease.
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In the North American strain, primary infection is by windblown spores (ascospores). These are disseminated during moist weather from April to October; the major spore discharge and infection are in June and July. The spores infect through buds or needles, and infected branch tips usually die by the following summer. A characteristic symptom during May and June is an orange discoloration at the base of otherwise green needles (see right). The fungus may grow down the branch and into the main stem of the tree where a canker commonly forms (see below). The stem of a young seedling is quickly girdled, and the tree is killed.
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A few months after an infected branch dies, fruiting bodies (pycnidia) appear near the base of dead needle fasicles. Asexual spores (conidia) ooze out of these pycnidia during wet weather from April to October. These spores are transported by rain splash and wind to nearby branches, spreading the infection in individual trees and onto adjacent trees. Fruiting bodies (apothecia) appear in early summer on branches that have been dead for 1 to 2 years (see below). The apothecia are also commonly found at the base of dead needle fasicles and are often found in association with the pycnidial stage.
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In the European strain, the windblown ascospore stage is rarely found and the infection period of the conidial spore stage is longer than in the North American strain, making it more difficult to control.
Management Guidelines
The best way to prevent the introduction of the dangerous European strain into the Lake States is to make sure that infected nursery stock, Christmas trees, or other infected material is not introduced.

In the Field
  • Pick red pine planting sites where Scleroderris canker is not present.
  • If the planting site is in a Scleroderris canker hazard area, select a species for planting that is immune or has a low susceptibility. Hard pines are highly susceptible, but spruces, cedars, firs, and larches are more resistant to infection.
  • Avoid geographic depressions, such as frost pockets, where the disease is most damaging.
  • Select planting stock from a nursery outside of the range of Scleroderris canker or from a nursery that has an effective fungicide control program.
  • Do not plant infected seedlings.
  • In high-value stands, prune lower branches on infected and healthy trees.
  • Do not ship infected red pine Christmas trees into areas where Scieroderris canker is not present.
  • Abide by all quarantine laws designed to prevent the introduction of the European strain into areas where it is not present.
Lots to consider here.  Hope this helps you keep your trees free from disease.  If it seems like too much to monitor call us or your local tree service with a plant health care division.  The Trees "R" Us, Inc. plant health care is a tree, plant and shrub maintenance program that will allow you to have more time to devote to your family rather than your lawn and garden.  We fertilize, protect and care for your plants giving you timely advice and proper maintenance.  Check out our plant health care program on our website at

At Trees "R" Us, Inc. we take pride in not only our professional tree care services, but also educating our customers. It is through education that we really save trees and help the environment. We hope you found this post informative and educational.

Trees "R" Us, Inc. is a professional tree service for the Chicago's North Shore, North and Northwest suburbs. Tree trimming, tree removal, stump grinding, fertilizations, tree disease treatments and prevention as well as plant health care are just a few of our high quality, professional services. Contact us today for a free analysis or quote at or at 847-913-9069.

Thanks for reading,

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