Out of Place: This Summer’s Pine Decline and Mortality

Here in the Northeast, we are quite accustomed to the sight of bare trees. In experiencing all seasons, we begin each year in a cold place of woodland dormancy - where the trees have long been without their leaves and we see the familiar silhouettes of forking branches and stems. Spring comes, bringing with it a flush of new, green leaves, and soon the days become long, hot, and beautifully shaded by full, bright canopies. This is the season of life, growth, and newness before autumn returns, the leaves are shed again, and the forest is quiet and bare once more. But have you noticed something out of place this summer? Stems lacking life among the youthful canopy? Across the region, during this season of rejuvenation, woodlands have been touched by pine decline and mortality.

Eastern white pine (Pinus strobus) is an important component of forests of the Northeast, providing for animal habitat, forest structure, and comprising a fair portion of our forest canopies. It is easy to identify from its bundles, or fascicles, of five long, fine needles and its unique shape, with branches that swoop upwards. In recent years, eastern white pine has been experiencing dramatic health decline, with increasing cases of twig and canopy dieback, premature browning and shedding of needles, and even death. This sort of impact to white pine health is commonly related to fungi that develop and thrive in incredibly moist conditions. Needlecast fungi, such as brown spot needlecast (Lecanosticta acicola) and grey needlecast (Lophophacidium dooksii), commonly develop and infect trees during late spring and early summer months. However, symptoms, or visible indications of infection, do not appear until spring or summer of the following year, when the fungi form structures on the needles that contain thousands of spores (the reproductive unit of fungi that serve a similar purpose as seeds in plants) and look like black, orange-red, or tan spots and lines. Eventually, needles will turn completely brown and fall from the tree. Eastern white pines are also sensitive to Procera root rot (Verticicladiella procera), a fungus that infects the roots or lower stem of a tree, and can lead to stunted growth, needle and twig dieback, and eventually, death. It may seem like eastern white pine has had a challenging hand dealt to it in the form of excessive moisture culturing fungi, but wait, there is indeed more.

Though not as prevalent here as in the western United States, white pine blister rust (Cronartium ribicola) can pose one of the greatest health challenges a white pine could face. This pathogen's spores are carried on the wind from their alternate hosts, currants and gooseberries (Ribies spp.), to the white pines, where the fungus will enter through pores (stomata) on the needles. After entering the needles, the pathogen will then move into the branches and stem of the tree, growing for two to three years before orangish-red "blisters" (cankers) appear on the bark. While mature trees that are infected are more resilient, young pines can be severely impacted and can deteriorate rapidly. It can be a heavy and hard life for eastern white pines in today's forests, but you, as a steward of forest health, alongside a natural resources professional, can take good management measures to ensure that your pines remain healthy and happy (see the resources below).

In experiencing decline and mortality, eastern white pines are not alone. Austrian pine (P. nigra), Scots pine (P. sylvestris), and pitch pine (P. resinosa) have also been impacted by fungal diseases. These pines, which each have 2-3 needles per fascicle, are susceptible to infection by Diplodia tip blight (Diplodia pinea). Diplodia infects new needles as they grow, causing browning, decreased needle growth, and eventually, whole branches may be killed while holding on to their dead needles. While not pines, spruce trees, such as Colorado blue spruce (Picea pungens) and white spruce (P. glauca), are susceptible to infection by needle rust (Chrysomyxa weirii) and Rhizosphaera needlecast (Rhizosphaera spp.), which turn needles red or lavender, respectively, and can leave large areas in the tree bare after needles are shed. Unlike the hardwoods that lose their leaves every year, evergreens do not come back from complete needle loss. For this reason, we now see the stems of dead and dying evergreens across the forest landscape that will remain there until they are removed or have collapsed. However, don't fret if you notice your larch trees turning yellow and shedding their needles. Larches are the only trees within the Pine family (Pinaceae) in Pennsylvania that are not evergreen and lose their needles annually.

Are the pines or spruces in your forest showing some signs of decreased health or decline? Are you feeling unsure of what you may be seeing or what to do next? Before lamenting their loss or heading out with a saw, be sure to know the facts about what is affecting your trees so that you may take the best steps possible to ensure continued health and vitality in your forest. Consider contacting a natural resources professional to discuss your concerns and possible treatment actions. The Bureau of Forestry, your consulting forester, or Penn State Extension may be able to help. You can even send a sample of your tree to the Penn State Plant Disease Clinic for diagnosis, free of charge. Of course, it is always important to be well informed about what is happening in our forests, so become acquainted with the resources provided below to know more about pines and other evergreens, their diseases, and potential prevention measures and treatments.

As much as we may wish to revel in the sunshine of summer for just a while longer, fall will soon be upon us. We will watch as the deciduous leaves change color and senesce, but among them, here and there, will stand perished pines, touched by the presence of fungi, reminding us of the impact of changing precipitation patterns and decreased vigor in our forests. But don't forget to take heart in this beautiful act of nature, for when one tree dies and leaves the canopy, there is space for new life and new growth that we will witness when spring comes again.

Resources:
Identifying Pines and Other Trees Common in PA
Common Diseases of Pines
Common Diseases of Spruce
Needlecast Diseases
Forest Insects and Diseases
Pennsylvania County Extension Offices
Penn State Plant Disease Clinic