Late this summer, the top vertical stem of our white pine turned brown and died. The balance of the tree remained healthy. In the fall, the brown began moving down the tree. This tree is about 7 years old and sits at the edge of our woods. It has eastern exposure with acidic soil. I am not sure if the sprinkler system hits it. When we first saw the top stem turning brown, we watered the tree several times with a Miracid. Earlier in the summer, we lost a white pine that started with these same symptoms. Is there anything we can do to save this tree?
Seeking the services of a certified arborist will be your best defense against losing your tree because it is exhibiting symptoms that can be caused by more than one problem. An insect, the white pine weevil, bores into the terminal shoot causing death of that branch. The weevil rarely kills the whole tree, but places it in a weakened state where the attack of other insects, diseases, or environmental problems can cause gradual death.
Eastern white pine (Pinus strobus) is a fast-growing tree. Unfortunately, as they mature, many develop problems. The symptoms reported are a general off-color, yellowing or browning of the needles, stunted growth, stunted needles, or total browning of the tree followed by death. The cause for the decline is most often due to environmental stresses rather than a particular pest. The stress opens the door to secondary attacks by diseases and insects, which then accelerate the decline of the tree. Stress is the primary problem because it weakens the tree’s natural resistance.
Location of a white pine tree is very important for proper health and vigor. White pines require well-drained, deep, fertile, acidic soil with a moderate amount of moisture. They do not tolerate poorly-drained soil, high pH, compacted soil, a thin topsoil layer, buried debris or drought. Any other conditions that restrict root growth are also detrimental to white pine trees. Root diseases and cankers are the most common fungal pathogens that attack the Eastern white pine. Root disease symptoms are characterized by overall poor growth, the tree becomes off-color, wilts and dies.
Insects often act as vectors (transporters of the pathogen) for diseases. They breed in the dead trees and stumps. Then the new generations move to the surrounding stressed trees, bringing the disease with them. Other attackers of stressed white pine include the pinewood nematode, which feeds on vascular tissue in the branches and trunks of all pines and some other conifers. An insect called the pine sawyer beetle acts as a vector for the nematode, introducing it to healthy trees. Damage from the pinewood nematode is seen as sudden wilting and death.
When Eastern white pine trees decline they should be removed quickly so they do not act as breeding places for insects that spread diseases to surrounding trees. Replace dead trees with other evergreens that can better tolerate the existing site conditions.