Tree Health Problems Related to Environmental Stress
Many health problems for trees are related to environmental stress.
Hot/cold temperatures, drying winds, poor soil-root relationships and man
can cause direct damage to leaves, bark and roots, which predisposes the
tree to secondary insect and disease attacks. Maintaining your trees in
good vigor through proper maintenance will prevent many problems,
including those listed below.
DROUGHT
Prolonged periods of time without moisture, accompanied by drying
winds, create a physiological imbalance in trees. Moisture is lost through
transpiration faster than the roots can supply it to the leaves, resulting
in the drying out and death of living tissue in leaves and areas of
succulent growth. This is indicated through uniform yellowing or browning
of the leaf edge. Extended periods of drought may result in the premature
loss of leaves.
When trees enter the winter under drought conditions or with low food
reserves, they are especially susceptible to injury. Winter injury occurs
most often when the frozen soil prevents water uptake by tree roots. In
areas where it is very cold and windy, the tree has to compensate for loss
of water from the area of the tree above the ground. Drought damage and
winter injury can be reduced by regular watering during prolonged dry
periods, mulching, and protection from prevailing winds.
SUN SCALD
Sun scald is a common problem occurring when the tree is young and the
bark is thin and smooth. On winter days, the bark on the south or
southwest side of the tree is warmed to above freezing by the sun’s rays.
When the temperature drops below freezing at night, the warmed tissue is
killed. This results in the formation of a long, narrow canker (or dead
spot) on the tree, providing the perfect site for a secondary attack by
insects or disease. To reflect the sun’s rays, paint the trunks of young
trees with white latex paint or use our white plastic tree guards.
COLD
Very cold, subzero temperatures can single-handedly kill dormant trees.
While cold weather damage cannot be avoided, the best way to minimize it
is to have well-established, healthy trees before the onset of the first
winter. A sudden sharp drop in temperature can cause differential
contraction between the outer wood and interior of softwood and/or
hardwood trees. This results in the formation of a long vertical crack in
the trunk known as a "frost crack."
SOIL-ROOT PROBLEMS
Trees that have the following symptoms are often in poor health due to
root problems:
- Poor vigor
- Off-colored, sparse or prematurely shed foliage
- Extremely slow growth
- Slow decline in vigor and eventual death over three to 10 years
The slow decline in the health of a tree occurs because it doesn’t have
the root surface area to intake the moisture and nutrients needed to meet
the tree’s growth requirements. The tree slowly starves to death due to
its inadequate root system. Restriction of root growth may be caused
by improper planting techniques; poor soil texture such as heavy day;
girdling roots; or planting done in hard, compacted soils.
SOIL PH PROBLEMS
In areas where the PH of a soil exceeds 6.5 (alkali soils), iron is
tied up in the soil and unavailable to the trees. Lack of this essential
tree nutrient results in partial or complete yellowing of the leaves
(chlorosis). In severe cases, it causes browning and/or shedding of
leaves.
Resolving iron deficiency problems can be accomplished by:
- applying a fertilizer with high sulfur-iron concentrations
- injecting trees with a solution of iron salts or
- spraying tree foliage with a solution of ferrous sulphate
HERBICIDE INJURY
Herbicide applications can drift in the air and translocate through the
soil, injuring nearby trees. Leaves damaged by herbicides will
characteristically cut upward. They may also have distorted growth, turn
brown on the margins and drop from their branches. If exposure is severe,
whole branch shoots will drop, twist and become deformed. Herbicide damage
in trees is typically associated with the use of chemicals for weed
control. Although these trees can survive such damage, the typically lose
all foliage and growth may be stunted. If you notice damage, the best
solution is to cut the tree down to 4 inches above the ground. It will
generally reshoot again, provided the damage is noticed soon enough.
Repeated exposure will kill the tree.
Remember that the roots may extend out into the soil two to three times
the height of the tree. This means that although there may not be a tree
close to where the herbicide was used, tree roots probably exist.
MECHANICAL INJURY
Mechanical injuries are wounds to the cambium, bark or roots of the
trees. These wounds expose healthy living tissue to infection by disease
organisms or attack by insects. The majority of mechanical injuries are
caused by man. The careless use of lawn mowers and weed whips around a
tree’s base destroys the inner bark and girdles of the tree. It not only
weakens it, but also makes it more susceptible to attack by insects and
disease.
Insect and disease problems in trees are often influenced by
environmental stress. Under normal conditions, trees can resist insect
attacks and disease infection. The effects of drought, soil-root problems
or mechanical injury may weaken your trees and predispose them to attack
or infection. In many cases, the primary health problem for trees is some
type of environmental stress, while insects and disease are secondary
problems. Many of these problems can be avoided by keeping your trees in
the best possible health and growing vigorously.
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