Introduction
Bark splitting can occur in response to various
environmental factors at different times of the year.
Splits can occur on the trunk of the tree as well as on
branches. Trees which are most susceptible to this type
of injury are those which are thin-barked, such as
certain fruit trees. Newly-planted trees or young trees
are more prone to bark-splitting. Bark splits are not
likely to be fatal to trees, although they will, in some
cases, allow entry of disease organisms which can cause
decay. Through proper treatment to encourage the natural
callusing process, a tree should be able to close most
splits.
There is no single reason for bark splitting on trees.
During late winter and early spring, severe cold followed
by rapid thawing can result in splits referred to as
"frost cracks". These frost cracks can actually
start from a wound inflicted earlier in the tree's
development. Sometimes the crack may remain in the
internal wood, but frosts can cause the crack to expand
and split the bark. Excessively late growth in the fall
stimulated by warm temperatures, high humidity, and high
nitrogen levels can increase susceptibility of trees to
frost cracking.
Fluctuating growth conditions may also cause splitting of
bark. Dry weather (which slows growth) followed by wet or
ideal growth conditions may cause an excessive or
vigorous amount of growth leading to splits in the bark.
Symptoms
Figure 1: Bark Split on
Kwanzan Cherry |
Figure 2: Bark Tracing to remove split |
Sunscald, especially in
winter months, can cause bark injury to thin-barked or
young trees. Although an exact split may not be seen
immediately, the outer layer of bark will peel away from
the affected area in the summer following the winter
damage. Sunscald injuries to tree limbs can be minimized
by avoiding heavy pruning of trees which have dense
canopies. Gradual thinning of limbs over a period of
years is preferable, particularly on thin-barked trees.
Newly planted trees may be protected from sunscald by
wrapping main trunks with tree wrap.
As mentioned before, certain trees are more susceptible to splits
than others. The trees on which we receive the most inquiries concerning
splits are Kwanzan cherry (Fig. 1), maple, and fruit
trees. Any newly-planted tree, especially of a thin-barked species,
is a candidate for bark-splitting if it is not cared for properly.
Be particularly careful to avoid fertilizing the trees late in the
growing season, as this may promote new growth and predispose the
tissue to winter injuries (including bark splitting). Autumn fertilization
following leaf drop and dormancy should not lead to this problem.
Management Strategies
When a split occurs on a tree, what should you do? In recent years,
quite a bit of research has been done on closure of tree wounds. These
investigations have indicated that tree wound paints are of little
value in helping a tree to callus over. For this reason, do not paint
or try to seal a split with paint or tar. Tracing the bark around
the split can be very helpful in aiding wound healing (Fig.
2). With a sharp knife, starting from one end of
the split, trace around one side of the wound, about 1/2 to 1 inch
back from the split bark. Stop at the other end and do the same procedure
on the opposite side of the split. Knives should be sterilized between
cuts by dipping them for several minutes in a 1:10 bleach:water solution
or a 70% alcohol solution to avoid contaminating the cuts. Carefully
remove the bark from inside the traced area. You should now have a
bare area resembling the diagram in Fig.
2. Remember to leave
this untreated. A tree growing with good vigor usually calluses over
quickest. Encourage vigor in the tree with yearly spring fertilizer
applications -- and be sure to provide adequate irrigation in hot,
dry weather. Bark splits will often close over completely leaving
a slight ridge in the trunk where callus tissue has been produced.
Last updated, KLS, 8/99
This publication contains pesticide recommendations. Changes in pesticide
regulations occur constantly, some materials mentioned may no longer
be available, and some uses may no longer be legal. All pesticides
distributed, sold, and/or applied in New York State must be registered
with the New York State Department of Environmental Conservation (DEC).
Questions concerning the legality and/or registration status for pesticide
use in New York State should be directed to the appropriate Cornell
Cooperative Extension Specialist or your regional DEC office. READ
THE LABEL BEFORE APPLYING ANY PESTICIDE. __________________________________________________________________________________
The Plant Disease Diagnostic Clinic
at Cornell University is located at 334 Plant Science Building,
Ithaca, NY, 14853. Phone: 607-255-7850, Fax: 607-255-4471,
Email: kls13@cornell.edu
or slj2@cornell.edu
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