PPDL Picture of the Week
August 31, 2020
White Pine Decline
Karen Rane and Tom Creswell, Plant Disease Diagnosticians
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.
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.