White Pine Decline

Karen Rane, Plant Disease Diagnostician, Botany & Plant Pathology, Purdue University

Decline is an all-too-common ailment of Eastern white pines (Pinus strobus) in Indiana. Affected trees will first appear off-color (either pale green or yellow-green when compared to healthy white pine trees), with shorter needles and short annual twig growth. Later, the bark of the branches may appear wrinkled, and the foliage becomes brown. Symptoms of decline commonly develop after a tree has been in a site for 8 to 20 years.

The problem is related to root stress. White pines grow best in slightly acidic, well-drained soils high in organic matter. The alkaline, heavy clay soils found throughout much of Indiana are not favorable for optimum white pine growth. Drought, excessive moisture and soil compaction are additional stress factors that can contribute to decline. Declining pines attract insect borers, which will damage the inner bark tissues, accelerating the tree's demise. In some instances, opportunistic fungal pathogens, such as Leptographium procerum, may infect the roots or lower trunk of declining trees as well.

Unfortunately, once the foliar symptoms develop, the roots of the tree have already been damaged and there is little that can be done to reverse the decline process. Dead trees should be removed, since these are attractive to insect borers that may invade adjacent trees. The best management practice to reduce decline in white pine is to plant this species in a site that is optimum for its growth. For more information on this problem, check out BP-34, Decline of White Pine in Indiana.