Background on Eastern White Pine Trees
The Eastern white pine tree was designated as the official state tree of Maine in 1945, which has been coined as the “The Pine Tree State” and appears on Maine’s state flag and seal. In 1955, the state of Michigan also chose the Eastern white pine to be their official state tree as a symbol of their logging history. The Eastern white pine is considered to be one of the largest conifer trees in the north eastern United States. Since 2009, the Eastern white pine has been experiencing dieback and general decline, which is a great concern regarding one of the most economically valuable and ecologically important forest trees in the northeast. Recently, the University of Massachusetts Amherst (UMass Amherst) posted information that begins to explain the reason for these symptoms of decline. According Dr. Nick Brazee, a plant pathologist at the UMass Amherst, it is a combination of climate change, several fungal pathogens, and a particular species of insects that are responsible for the decline in the Eastern white pines.
White Pine Needle Drop (WPND)
Disease is primarily responsible for the symptoms of declining pines, namely premature needle drop, yellowing of needles, resinosis, dieback of canopy, and branch and tree death. WPND is caused by several fungal pathogens. Once you see the needles begin to become discolored (yellow/brown), it is usually the cause of the root pathogens due to it affecting the entirety of the tree. At the same time, the environment for spore activity and germination has been fueled by the increase in temperatures and precipitation in the northeast region of the United States.
Caliciopsis Canker & Bast Scale
Another fungus and insect complex that is also partially responsible for the dieback of Eastern white pines are the caliciopsis canker and white pine bast scale. Bast scale is tiny, black, oval-shaped scales that lack both eyes and legs. Bast scale use a long stylet to drain sap from outer layers of phloem (tissue) of twigs and branches. White pine bast scales live under lichens, which are slow growing plants that form crusty leaf-like growth on rocks and trees. These have been found on white pine branches.
Recently, the white pine bast scale has been identified as a catalyst for the development of caliciopsis canker in white pine trees. Although the bast scale causes almost no damage to the tree, the feeding areas that they produce are extremely conducive to the development of caliciopsis cankers in trees. The primary problem with an outbreak of caliciopsis cankers is that they cause dead areas in the tree’s tissue and as more cankers develop, the affected branches will eventually be unable to disperse the water into the foliage and in which case, the tree will die. Root rot diseases can also affect the dieback of white pines, and will be addressed in a future post.
Ways to Manage White Pine Needle Drop
In conclusion, tree thinning, or selective removal of branches, of existing white pines aids in the reduction of WPND by increasing radial growth, promoting crown vigor, and an overall general reduction in WPND. Many arborists have also found that fertilizing the tree with nitrogen can help to restore vigor, especially to trees highly stressed from WPND. Fungicide applications are often impractical for large trees or multiple trees, but focused applications on specimen or very young white pines can be helpful to control WPND. It has become clear that the issues affecting white pines are not going away any time soon, but can be controlled using an experienced, dedicated team of arborists.
If you have any questions, or you are interested in any of our tree services, please contact us at 877-308-8733, or request a free consultation. We look forward to hearing from you!
Bob Lees, MCLP
Photo of Caliciopsis Canker Courtesy of Jen Weimer