THE CARE OF TREES
STUDY I. INSECTS INJURIOUS TO TREES AND HOW TO COMBAT THEM
In a general way, trees are attacked by three classes of insects, and
the remedy to be employed in each case depends upon the class to which
the insect belongs. The three classes of insects are:
1. Those that *chew* and swallow some portion of the leaf; as, for
example, the elm leaf beetle, and the tussock, gipsy, and brown-tail
moths.
2. Those that *suck* the plant juices from the leaf or bark; such as the
San José scale, oyster-shell, and scurfy scales, the cottony maple
scale, the maple phenacoccus on the sugar maples, and the various
aphides on beech, Norway maple, etc.
3. Those that *bore* inside of the wood or inner bark. The principal
members of this class are the leopard moth, the hickory-bark borer, the
sugar-maple borer, the elm borer, and the bronze-birch borer.
The chewing insects are destroyed by spraying the leaves with arsenate
of lead or Paris green. The insects feed upon the poisoned foliage and
thus are themselves poisoned.
The sucking insects are killed by a contact poison: that is, by spraying
or washing the affected parts of the tree with a solution which acts
externally on the bodies of the insects, smothering or stifling them.
The standard solutions for this purpose are kerosene emulsion, soap and
water, tobacco extract, or lime-sulfur wash.
[Illustration: FIG. 97.--A Gas-power Spraying Apparatus.]
The boring insects are eliminated by cutting out the insect with a
knife, by injecting carbon bisulphide into the burrow and clogging the
orifice immediately after injection with putty or soap, or in some cases
where the tree is hopelessly infested, by cutting down and burning the
entire tree.
[Illustration: FIG. 98.--A Barrel Hand-pump Spraying Outfit.]
For information regarding the one of these three classes to which any
particular insect belongs, and for specific instructions on the
application of a remedy, the reader is advised to write to his State
Entomologist or to the U.S. Bureau of Entomology at Washington, D.C. The
letter should state the name of the tree affected, together with the
character of the injury, and should be accompanied by a specimen of the
insect, or by a piece of the affected leaf or bark, preferably by both.
The advice received will be authentic and will be given without charge.
[Illustration: FIG. 99.--Egg-masses of the Tussock Moth.]
When to spray: _In the case of chewing insects_, the latter part of May
is the time to spray. The caterpillars hatch from their eggs, and
the elm leaf beetle leaves its winter quarters at that time. _In the
case of sucking insects_, the instructions will have to be more
specific, depending upon the particular insect in question. Some
sucking insects can best be handled in May or early June when their
young emerge, others can be effectively treated in the fall or
winter when the trees are dormant.
How to spray: Thoroughness is the essential principle in all spraying.
In the case of leaf-eating insects, this means covering every leaf
with the poison and applying it to the under side of the leaves,
where the insects generally feed. In the case of sucking insects,
thoroughness means an effort to touch every insect with the spray.
It should be borne in mind that the insect can be killed only when
hit with the chemical. The solution should be well stirred, and
should be applied by means of a nozzle that will coat every leaf
with a fine, mist-like spray. Mere drenching or too prolonged an
application will cause the solution to run off. Special precautions
should be taken with contact poisons to see that the formula is
correct. Too strong a solution will burn the foliage and tender
bark.
Spraying apparatus: There are various forms of spraying apparatus in the
market, including small knapsack pumps, barrel hand-pumps, and
gasolene and gas-power sprayers, Figs. 97 and 98. Hose and nozzles
are essential accessories. One-half inch, three-ply hose of the best
quality is necessary to stand the heavy pressure and wear. Two
50-foot lengths is the usual quantity required for use with a barrel
hand-pump. Each line of hose should be supplied with a bamboo pole
10 feet long, having a brass tube passed through it to carry the
nozzle. The Vermorel nozzle is the best type to use. The cost of a
barrel outfit, including two lines of hose, nozzles and truck,
should be from $30 to $40. Power sprayers cost from $150 to $300 or
more.
Spraying material:
_Arsenate of lead_ should be used in the proportion Of 4 pounds of the
chemical to 50 gallons of water. A brand of arsenate of lead
containing at least 14 per cent of arsenic oxide with not more than
50 per cent of water should be insisted upon. This spray may be used
successfully against caterpillars and other leaf-eating insects in
the spring or summer.
_Whale-oil soap_ should be used at the rate of 1½ pounds of the soap
to 1 gallon of hot water, if applied to the tree in winter. As a
spray in summer, use 1 pound of the soap to 5 gallons of water. This
treatment is useful for most sucking insects.
_Lime-sulfur wash_ is an excellent material to use against sucking
insects, such as the San José scale and other armored scales. The
application of a lime-sulfur wash when put on during the dormant
season is not likely to harm a tree and has such an excellent
cleansing effect that the benefits to be derived in this direction
alone are often sufficient to meet the cost of the treatment.
Lime-sulfur wash consists of a mixture, boiled one hour, of 40
pounds of lime and 80 pounds of sulfur, in 50 gallons of water. It
may be had in prepared form and should then be used at the rate of 1
gallon to about 9 gallons of water in winter or early spring before
the buds open. At other times of the year and for the softer-bodied
insects a more diluted mixture, possibly 1 part to 30 or 40 parts of
water, should be used, varying with each case separately.
_Kerosene emulsion_ consists of one-half pound of hard soap, 1 gallon
of boiling water, and 2 gallons of kerosene. It may be obtained in
prepared form and is then to be used at the rate of one part of the
solution to nine parts of water when applied in winter or to the
bark only in summer. Use 2 gallons of the solution to a 40-gallon
barrel of water when applying it to the leaves in the summer.
Kerosene emulsion is useful as a treatment for scale insects.
_Tobacco water_ should be prepared by steeping one-half pound of
tobacco stems or leaves in a gallon of boiling water and later
diluting the product with 5 to 10 gallons of water. It is
particularly useful for plant lice in the summer.
The life history of an insect: In a general way, all insects have four
stages of transformation before a new generation is produced. It is
important to consider the nature of these four stages in order that
the habits of any particular insect and the remedies applicable in
combating it may be understood.
All insects develop from _eggs_, Fig. 99. The eggs then hatch into
caterpillars or grubs, which is the _larva_ stage, in which most
insects do the greatest damage to trees. The caterpillars or grubs
grow and develop rapidly, and hence their feeding is most ravenous.
Following the larva stage comes the third or _pupa_ stage, which is
the dormant stage of the insect. In this stage the insect curls
itself up under the protection of a silken cocoon like the tussock
moth, or of a curled leaf like the brown-tail moth, or it may be
entirely unsheltered like the pupa of the elm leaf beetle. After the
pupa stage comes the _adult insect_, which may be a moth or a
beetle.
A study of the four stages of any particular insect is known as a
study of its _life history_. The important facts to know about the
life history of an insect are the stage in which it does most of its
feeding, and the period of the year in which this occurs. It is also
important to know how the insect spends the winter in order to
decide upon a winter treatment.
IMPORTANT INSECTS
THE ELM LEAF BEETLE
Life history: The elm leaf beetle, Fig. 100, is annually causing the
defoliation of thousands of elm trees throughout the United States.
Several successive defoliations are liable to kill a tree. The
insects pass the winter in the beetle form, hiding themselves in
attics and wherever else they can secure shelter. In the middle of
May when the buds of the elm trees unfold, the beetles emerge from
their winter quarters, mate, and commence eating the leaves, thus
producing little holes through them. While this feeding is going on,
the females deposit little, bright yellow eggs on the under side of
the leaves, which soon hatch into small larvae or grubs. The grubs
then eat away the soft portion of the leaf, causing it to look like
lacework. The grubs become full grown in twenty days, crawl down to
the base of the tree, and there transform into naked, orange-colored
pupae. This occurs in the early part of August. After remaining in
the pupa stage about a week, they change into beetles again, which
either begin feeding or go to winter quarters.
Remedies: There are three ways of combating this insect: First, by
_spraying the foliage_ with arsenate of lead in the latter part of
May while the beetles are feeding, and repeating the spraying in
June when the larvae emerge. The spraying method is the one most to
be relied on in fighting this insect. A second, though less
important remedy, consists in _destroying the pupae_ when they
gather in large quantities at the base of the tree. This may be
accomplished by gathering them bodily and destroying them, or by
pouring hot water or a solution of kerosene over them. In large
trees it may be necessary to climb to the crotches of the main limbs
to get some of them. The third remedy lies in gathering and
_destroying the adult beetles_ when found in their winter quarters.
The application of bands of burlap or "tanglefoot," or of other
substances often seen on the trunks of elm trees is useless, since
these bands only prevent the larvae from crawling down from the
leaves to the base and serve to prevent nothing from crawling up.
Scraping the trunks of elm trees is also a waste of effort.
[Illustration: FIG. 100.--The Elm Leaf Beetle. (After Dr. E.P. Felt.)
1. Egg cluster, enlarged. 1a. Single egg, greatly enlarged. 2. Young
larva, enlarged. 3. Full grown larva, much enlarged. 4. Pupa, enlarged.
5. Overwintered beetle, enlarged. 6. Fresh, brightly colored beetle,
enlarged. 7. Under surface of leaf showing larvae feeding. 8. Leaf eaten
by larvae. 9. Leaf showing holes eaten by beetles.]
THE TUSSOCK MOTH
Life history: This insect appears in the form of a red-headed,
yellow-colored caterpillar during the latter part of May, and in
June and July. The caterpillars surround themselves with silken
cocoons and change into pupae. The mature moths emerge from the
cocoons after a period of about two weeks, and the females, which
are wingless, soon deposit their eggs on the bark of trees, on
twigs, fences, and other neighboring objects. These eggs form white
clusters of nearly 350 individual eggs each, and are very
conspicuous all winter, see Fig. 101.
Remedies: There are two ways of combating this insect: (1) By spraying
with arsenate of lead for the caterpillars during the latter part of
May and early June. (2) By removing and destroying the egg masses in
the fall or winter.
[Illustration: FIG. 101.--The Tussock Moth. (After Dr. E.P. Felt.)
1. Caterpillar. 2. Male moth. 3. Female moth laying eggs. 4 Cocoons. 5.
Cast skins of caterpillar. 6. Work of young caterpillar. 7. Male pupa. 8
and 9. Girdled branches.]
THE GIPSY MOTH
Life history: This insect, imported from Europe to this country in 1868,
has ever since proved a serious enemy of most shade, forest, and
fruit trees in the New England States. It even feeds on
evergreens, killing the trees by a single defoliation.
The insect appears in the caterpillar stage from April to July. It
feeds at night and rests by day. The mature caterpillar, which is
dark in color, may be recognized by rows of blue and red spots along
its back. After July, egg masses are deposited by the female moths
on the bark of trees, and on leaves, fences, and other neighboring
objects. Here they remain over the winter until they hatch in the
spring. The flat egg masses are round or oval in shape, and are
yellowish-brown in color. See Fig. 102.
Remedies: Spray for the caterpillars in June with arsenate of lead and
apply creosote to the egg masses whenever found.
THE BROWN-TAIL MOTH
Life history: This insect was introduced here from Europe in 1890 and
has since done serious damage to shade, forest, and fruit trees, and
to shrubs in the New England States.
It appears in the caterpillar stage in the early spring and
continues to feed on the leaves and buds until the last of June.
Then the caterpillars pupate, the moths come out, and in July and
August the egg clusters appear. These hatch into caterpillars which
form nests for themselves by drawing the leaves together. Here they
remain protected until the spring. See Fig. 103.
Remedies: Collect the winter nests from October to April and burn them.
Also spray the trees for caterpillars in early May and especially in
August with arsenate of lead.
[Illustration: FIG. 102.--The Gipsy Moth. (After F.W. Rane Mass. State
Forester.)]
[Illustration: FIG. 103.--The Brown-tail Moth. (After F.W. Rane, Mass.
State Forester.)]
[Illustration: FIG. 104.--Larva of the Leopard Moth.]
THE FALL WEBWORM
The caterpillars of this insect congregate in colonies and surround
themselves with a web which often reaches the size of a foot or more in
diameter. These webs are common on trees in July and August. Cutting off
the webs or burning them on the twigs is the most practical remedy.
[Illustration: FIG. 105.--Branch Showing Work of the Leopard Moth Larva.]
THE LEOPARD MOTH
Life history: This insect does its serious damage in the grub form. The
grubs which are whitish in color with brown heads, and which vary in
size from 3/8 of an inch to 3 inches in length (Fig. 104), may be
found boring in the wood of the branches and trunk of the tree all
winter. Fig. 105. The leopard moth requires two years to complete
its round of life. The mature moths are marked with dark spots
resembling a leopard's skin, hence the name. Fig. 106. It is one of
the commonest and most destructive insects in the East and is
responsible for the recent death of thousands of the famous elm
trees in New Haven and Boston. Fig. 107.
[Illustration: FIG. 106.--The Leopard Moth.]
Remedies: Trees likely to be infested with this insect should be
examined three or four times a year for wilted twigs, dead branches,
and strings of expelled frass; all of which may indicate the
presence of this borer. Badly infested branches should be cut off
and burned. Trees so badly infested that treatment becomes too
complicated should be cut down and destroyed. Where the insects are
few and can be readily reached, an injection of carbon bisulphide
into the burrow, the orifice of which is then immediately closed
with soap or putty, will often destroy the insects within.
[Illustration: FIG. 107.--Elm Tree Attacked by the Leopard Moth.]
THE HICKORY BARK BORER
Life history: This insect is a small brown or black beetle in its mature
form and a small legless white grub in its winter stage. The beetles
appear from June to August. In July they deposit their eggs in the
outer sapwood, immediately under the bark of the trunk and larger
branches. The eggs soon hatch and the grubs feed on the living
tissue of the tree, forming numerous galleries. The grubs pass the
winter in a nearly full-grown condition, transform to pupae in May,
and emerge as beetles in June.
Remedies: The presence of the insect can be detected by the small holes
in the bark of the trees and the fine sawdust which is ejected from
these holes, when the insects are active. It is important to
emphasize the advisability of detecting the fine sawdust because
that is the best indication of the actual operations of the hickory
bark borer. These holes, however, will not be noticeable until the
insect has completed its transformation. In summer, the infested
trees show wilted leaves and many dead twigs. Holes in the base of
the petioles of these leaves are also signs of the working of the
insect. Since the insect works underneath the bark, it is
inaccessible for treatment and all infested trees should be cut down
and burned, or the bark removed and the insects destroyed. This
should be done before the beetles emerge from the tree in June.
PLANT LICE OR APHIDES
These often appear on the under side of the leaves of the beech, Norway
maple, tulip tree, etc. They excrete a sweet, sticky liquid called
"honey-dew," and cause the leaves to curl or drop. Spraying with
whale-oil soap solution formed by adding one pound of the soap to five
gallons of water is the remedy.
STUDY II. TREE DISEASES
Because trees have wants analogous to those of human beings, they also
have diseases similar to those which afflict human beings. In many cases
these diseases act like cancerous growths upon the human body; in some
instances the ailment may be a general failing due to improper feeding,
and in other cases it may be due to interference with the life processes
of the tree.
How to tell an ailing tree: Whatever the cause, an ailing tree will
manifest its ailment by one or more symptoms.
A change of color in the leaves at a time when they should be
perfectly green indicates that the tree is not growing under normal
conditions, possibly because of an insufficiency of moisture or
light or an overdose of foreign gases or salts. Withering of the
leaves is another sign of irregularity in water supply. Dead tops
point to some difficulty in the soil conditions or to some disease
of the roots or branches. Spotted leaves and mushroom-like growths
or brackets protruding from the bark as in Fig. 108, are sure signs
of disease.
In attempting to find out whether a tree is healthy or not, one
would therefore do well to consider whether the conditions under
which it is growing are normal or not; whether the tree is suitable
for the location; whether the soil is too dry or too wet; whether
the roots are deprived of their necessary water and air by an
impenetrable cover of concrete or soil; whether the soil is well
drained and free from foreign gases and salts; whether the tree is
receiving plenty of light or is too much exposed; and whether it is
free from insects and fungi.
If, after a thorough examination, it is found that the ailment has
gone too far, it may not be wise to try to save the tree. A timely
removal of a tree badly infested with insects or fungi may often be
the best procedure and may save many neighboring trees from
contagious infection. For this, however, no rules can be laid down
and much will depend on the local conditions and the judgment and
knowledge of the person concerned.
[Illustration: FIG. 108.--A Bracket Fungus (_Elfvingia megaloma_) on a
Tulip Tree.]
Fungi as factors of disease: The trees, the shrubs and the flowers with
which we are familiar are rooted in the ground and derive their food
both from the soil and from the air. There is, however, another
group of plants,--_the fungi_,--the roots of which grow in trees and
other plants and which obtain their food entirely from the trees or
plants upon which they grow. The fungi cannot manufacture their own
food as other plants do and consequently absorb the food of their
host, eventually reducing it to dust. The fungi are thus
disease-producing factors and the source of most of the diseases of
trees.
When we can see fungi growing on a tree we may safely assume that
they are already in an advanced state of development. We generally
discover their presence when their fruiting bodies appear on the
surface of the tree as shown in Fig 109. These fruiting bodies are
the familiar mushrooms, puffballs, toadstools or shelf-like brackets
that one often sees on trees. In some cases they spread over the
surface of the wood in thin patches. They vary in size from large
bodies to mere pustules barely visible to the naked eye. Their
variation in color is also significant, ranging from colorless to
black and red but never green. They often emulate the color of the
bark, Fig. 110.
Radiating from these fruiting bodies into the tissues of the tree
are a large number of minute fibers, comprising the _mycelium_ of
the fungus. These fibers penetrate the body of the tree in all
directions and absorb its food. The mycelium is the most important
part of the fungous growth. If the fruiting body is removed, another
soon takes its place, but if the entire mycelium is cut out, the
fungus will never come back. The fruiting body of the fungus bears
the seed or _spores_. These spores are carried by the wind or
insects to other trees where they take root in some wound or crevice
of the bark and start a new infestation.
[Illustration: FIG. 109.--The Fruiting Body of a Fungus.]
The infestation will be favored in its growth if the spore can find
plenty of food, water, warmth and darkness. As these conditions
generally exist in wounds and cavities of trees, it is wise to keep
all wounds well covered with coal tar and to so drain the cavities
that moisture cannot lodge in them. This subject will be gone into
more fully in the following two studies on "Pruning Trees" and "Tree
Repair."
[Illustration: FIG. 110.--The Birch-fungus rot. (_Polyponis betulinus_
Fr.) Note the similarity in the color of the fruiting body and bark of
the tree.]
While the majority of the fungi grow on the trunks and limbs of
trees, some attack the leaves, some the twigs and others the roots.
Some fungi grow on living wood some on dead wood and some on both.
Those that attack the living trees are the most dangerous from the
standpoint of disease.
The chestnut disease: The disease which is threatening the destruction
of all the chestnut trees in America is a fungus which has, within
recent years, assumed such vast proportions that it deserves special
comment. The fungus is known as _Diaporthe parasitica_ (Murrill),
and was first observed in the vicinity of New York in 1905. At that
time only a few trees were known to have been killed by this
disease, but now the disease has advanced over the whole chestnut
area in the United States, reaching as far south as Virginia and as
far west as Buffalo. Fig. 111 shows the result of the chestnut
disease.
The fungus attacks the cambium tissue underneath the bark. It enters
through a wound in the bark and sends its fungous threads from the
point of infection all around the trunk until the latter is girdled
and killed. This may all happen within one season. It is not until
the tree has practically been destroyed that the disease makes its
appearance on the surface of the bark in the form of brown patches
studded with little pustules that carry the spores. When once
girdled, the tree is killed above the point of infection and
everything above dies, while some of the twigs below may live until
they are attacked individually by the disease or until the trunk
below their origin is infected.
All species of chestnut trees are subject to the disease. The
Japanese and Spanish varieties appear to be highly resistant, but
are not immune. Other species of trees besides chestnuts are not
subject to the disease.
[Illustration: FIG. 111.--Chestnut Trees Killed by the Chestnut
Disease.]
There is no remedy or preventive for this disease. From the nature
of its attack, which is on the inner layer of the tree, it is
evident that all applications of fungicides, which must necessarily
be applied to the outside of the tree, will not reach the disease.
Injections are impossible and other suggested remedies, such as
boring holes in the wood for the purpose of inserting chemicals, are
futile.
The wood of the chestnut tree, within three or four years after its
death, is still sound and may be used for telephone and telegraph
poles, posts, railroad ties, lumber and firewood.
Spraying for fungous diseases: Where a fungous disease is attacking the
leaves, fruit, or twigs, spraying with Bordeaux mixture may prove
effective. The application of Bordeaux mixture is deterrent rather
than remedial, and should therefore be made immediately before the
disease appears. The nature of the disease and the time of treatment
can be determined without cost, by submitting specimens of affected
portions of the plant for analysis and advice to the State
Agricultural Experiment Station or to the United States Department
of Agriculture.
Bordeaux mixture, the standard fungicide material, consists of a
solution of 6 pounds of copper sulphate (blue vitriol) with 4 pounds
of slaked lime in 50 gallons of water. It may be purchased in
prepared form in the open market, and when properly made, has a
brilliant sky-blue color. Spraying with Bordeaux mixture should be
done in the fall, early spring, or early summer, but never during
the period when the trees are in bloom.
STUDY III. PRUNING TREES
FUNDAMENTAL PRINCIPLES
Trees are very much like human beings in their requirements, mode of
life and diseases, and the general principles applicable to the care of
one are equally important to the intelligent treatment of the other. The
removal of limbs from trees, as well as from human beings, must be done
sparingly and judiciously. Wounds, in both trees and human beings, must
be disinfected and dressed to keep out all fungus or disease germs.
Fungous growths of trees are similar to human cancers, both in the
manner of their development and the surgical treatment which they
require. Improper pruning will invite fungi and insects to the tree,
hence the importance of a knowledge of fundamental principles in this
branch of tree care.
[Illustration: FIG. 112.--A Tree Pruned Improperly and too Severely.]
Time: Too much pruning at one time should never be practiced (Fig. 112),
and no branch should be removed from a tree without good reason for
so doing. Dead and broken branches should be removed as soon as
observed, regardless of any special pruning season, because they are
dangerous, unsightly and carry insects and disease into the heart of
the tree. But all other pruning, whether it be for the purpose of
perfecting the form in shade trees, or for increasing the production
of fruit in orchard trees, should be confined to certain seasons.
Shade and ornamental trees can best be pruned in the fall, while the
leaves are still on the tree and while the tree itself is in
practically a dormant state.
Proper cutting: All pruning should be commenced at the top of the tree
and finished at the bottom. A shortened branch (excepting in poplars
and willows, which should be cut in closely) should terminate in
small twigs which may draw the sap to the freshly cut wound; where a
branch is removed entirely, the cut should be made-close and even
with the trunk, as in Fig. 113. Wherever there is a stub left after
cutting off a branch, the growing tissue of the tree cannot cover it
and the stub eventually decays, falls out and leaves a hole (see
Fig. 114), which serves to carry disease and insects to the heart of
the tree. This idea of close cutting cannot be over-emphasized.
Where large branches have to be removed, the splitting and ripping
of the bark along the trunk is prevented by making one cut beneath
the branch, about a foot or two away from the trunk, and then
another above, close to the trunk.
[Illustration: FIG. 113.--Branches Properly Cut Close to the Trunk.]
Too severe pruning: In pruning trees, many people have a tendency to cut
them back so severely as to remove everything but the bare trunk and
a few of the main branches. This process is known as "heading
back." It is a method, however, which should not be resorted to
except in trees that are very old and failing, and even there only
with certain species, like the silver maple, sycamore, linden and
elm. Trees like the sugar maple will not stand this treatment at
all. The willow is a tree that will stand the process very readily
and the Carolina poplar must be cut back every few years, in order
to keep its crown from becoming too tall, scraggy and unsafe.
[Illustration: FIG. 114.--A Limb Improperly Cut. Note how the stub is
decaying and the resulting cavity is becoming diseased.]
Covering wounds: The importance of immediately covering all wounds with
coal tar cannot be overstated. If the wound is not tarred, the
exposed wood cracks, as in Fig. 115, providing suitable quarters for
disease germs that will eventually destroy the body of the tree.
Coal tar is by far preferable to paint and other substances for
covering the wound. The tar penetrates the exposed wood, producing
an antiseptic as well as a protective effect. Paint only forms a
covering, which may peel off in course of time and which will later
protrude from the cut, thus forming, between the paint and the wood,
a suitable breeding place for the development of destructive fungi
or disease. The application of tin covers, burlap, or other bandages
to the wound is equally futile and in most cases even injurious.
[Illustration: FIG. 115.--Result of a Wound not Covered with Coal Tar.
The exposed wood cracked and decay set in.]
SPECIAL CONSIDERATIONS
Pruning shade trees: Here, the object is to produce a symmetrical crown
and to have the lowest branches raised from the ground sufficiently
high to enable pedestrians to pass under with raised umbrellas. Such
pruning should, therefore, necessarily be light and confined to the
low limbs and dead branches.
Pruning lawn trees: Here the charm of the tree lies in the low reach of
the branches and the compactness of the crown. The pruning should,
therefore, be limited to the removal of dead and diseased branches
only.
Pruning forest trees: Forest trees have a greater commercial value when
their straight trunks are free from branches. In the forest, nature
generally accomplishes this result and artificial pruning seldom has
to be resorted to. Trees in the forest grow so closely together that
they shut out the sunlight from their lower limbs, thus causing the
latter to die and fall off. This is known as natural pruning. In
some European forests, nature is assisted in its pruning by workmen,
who saw off the side branches before they fall of their own accord;
but in this country such practice would be considered too expensive,
hence it is seldom adopted.
TOOLS USED IN PRUNING
Good tools are essential for quick and effective work in pruning. Two or
three good saws, a pair of pole-shears, a pole-saw, a 16-foot single
ladder, a 40-foot extension ladder of light spruce or pine with hickory
rungs, a good pruning knife, plenty of coal tar, a fire-can to heat the
tar, a pole-brush, a small hand brush and plenty of good rope comprise
the principal equipment of the pruner.
SUGGESTIONS FOR THE SAFETY OF TREE CLIMBERS
1. Before climbing a tree, judge its general condition. The trunk of a
tree that shows age, disease, or wood-destroying insects generally has
its branches in an equally unhealthy condition.
2. The different kinds of wood naturally differ in their strength and
elasticity. The soft and brash woods need greater precautions than the
strong and pliable ones. The wood of all the poplars, the ailanthus, the
silver maple and the chestnut, catalpa and willow is either too soft or
too brittle to be depended upon without special care. The elm, hickory
and oak have strong, flexible woods and are, therefore, safer than
others. The red oak is weaker than the other oaks. The sycamore and
beech have a tough, cross-grained wood which is fairly strong. The
linden has a soft wood, while the ash and gum, though strong and
flexible, are apt to split.
3. Look out for a limb that shows fungous growths. Every fungus sends
fibers into the main body of the limb which draw out its sap. The
interior of the branch then loses its strength and becomes like a
powder. Outside appearances sometimes do not show the interior
condition, but one should regard a fungus as a danger sign.
4. When a limb is full of holes or knots, it generally indicates that
borers have been working all kinds of galleries through it, making it
unsafe. The silver maple and sycamore maple are especially subject to
borers which, in many cases, work on the under side of the branch so
that the man in the tree looking down cannot see its dangerous
condition.
5. A dead limb with the bark falling off indicates that it died at least
three months before and is, therefore, less safe than one with its bark
tightly adhering to it.
6. Branches are more apt to snap on a frosty day when they are covered
with an icy coating than on a warm summer day.
7. Always use the pole-saw and pole-shears on the tips of long branches,
and use the pole-hook in removing dead branches of the ailanthus and
other brittle trees where it would be too dangerous to reach them
otherwise.
8. Be sure of the strength of a branch before tying an extension ladder
to it.
STUDY IV. TREE REPAIR
Where trees have been properly cared for from their early start, wounds
and cavities and their subsequent elaborate treatment have no place. But
where trees have been neglected or improperly cared for, wounds and
cavities are bound to occur and early treatment becomes a necessity.
There are two kinds of wounds on trees: (1) surface wounds, which do not
extend beyond the inner bark, and (2) deep wounds or cavities, which may
range from a small hole in a crotch to the hollow of an entire trunk.
Surface wounds: Surface wounds (Fig. 116) are due to bruised bark, and a
tree thus injured can no longer produce the proper amount of foliage
or remain healthy very long. The reason for this becomes very
apparent when one looks into the nature of the living or active
tissue of a tree and notes how this tissue becomes affected by such
injuries.
[Illustration: FIG. 116.--A Surface Wound Properly Freed from Decayed
Wood and Covered with Coal Tar.]
This living or active tissue is known as the "cambium layer," and is
a thin tissue situated immediately under the bark. It must
completely envelop the stem, root and branches of the trees. The
outer bark is a protective covering to this living layer, while the
entire interior wood tissue chiefly serves as a skeleton or support
for the tree. The cambium layer is the real, active part of the
tree. It is the part which transmits the sap from the base of the
tree to its crown; it is the part which causes the tree to grow by
the formation of new cells, piled up in the form of rings around the
heart of the tree; and it is also the part which prevents the
entrance of insects and disease to the inner wood. From this it is
quite evident that any injury to the bark, and consequently to this
cambium layer alongside of it, will not only cut off a portion of
the sap supply and hinder the growth of the tree to an extent
proportional to the size of the wound, but will also expose the
inner wood to the action of decay. The wound may, at first, appear
insignificant, but, if neglected, it will soon commence to decay
and thus to carry disease and insects into the tree. The tree then
becomes hollow and dangerous and its life is doomed.
Injury to the cambium layer, resulting in surface wounds, may be due
to the improper cutting of a branch, to the bite of a horse, to the
cut of a knife or the careless wielding of an axe, to the boring of
an insect, or to the decay of a fungous disease. (See Fig. 117.)
Whatever the cause, _the remedy lies in cleaning out all decayed
wood, removing the loose bark and covering the exposed wood with
coal tar_.
In cutting off the loose bark, the edges should be made smooth
before the coal tar is applied. Loose bark, put back against a tree,
will never grow and will only tend to harbor insects and disease.
Bandages, too, are hurtful because, underneath the bandage, disease
will develop more rapidly than where the wound is exposed to the sun
and wind. The application of tin or manure to wounds is often
indulged in and is equally injurious to the tree. The secret of all
wound treatment is to keep the wound _smooth, clean_ to the live
tissue, _and well covered_ with coal tar.
The chisel or gouge is the best tool to employ in this work. A sharp
hawk-billed knife will be useful in cutting off the loose bark. Coal
tar is the best material for covering wounds because it has both an
antiseptic and a protective effect on the wood tissue. Paint, which
is very often used as a substitute for coal tar, is not as
effective, because the paint is apt to peel in time, thus allowing
moisture and disease to enter the crevice between the paint and the
wood.
[Illustration: FIG. 117.--A Neglected Surface Wound. Note the rough
surface of the wound, the want of a coal tar covering and the fungous
growth that followed.]
Cavities: Deep wounds and cavities are generally the result of stubs
that have been permitted to rot and fall out. Surface wounds allowed
to decay will deepen in course of time and produce cavities.
Cavities in trees are especially susceptible to the attack of
disease because, in a cavity, there is bound to exist an
accumulation of moisture. With this, there is also considerable
darkness and protection from wind and cold, and these are all ideal
conditions for the development of disease.
The successful application of a remedy, in all cavity treatment,
hinges on this principal condition--_that all traces of disease
shall be entirely eliminated before treatment is commenced_.
Fungous diseases attacking a cavity produce a mass of fibers, known
as the "mycelium," that penetrate the body of the tree or limb on
which the cavity is located. In eliminating disease from a cavity,
it is, therefore, essential to go _beyond_ the mere decaying surface
and to cut out all fungous fibers that radiate into the interior of
the tree. Where these fibers have penetrated so deeply that it
becomes impossible to remove every one of them, the tree or limb
thus affected had better be cut down. (Fig. 118.) The presence of
the mycelium in wood tissue can readily be told by the discolored
and disintegrated appearance of the wood.
The filling in a cavity, moreover, should serve to prevent the
accumulation of water and, where a cavity is perpendicular and so
located that the water can be drained off without the filling, the
latter should be avoided and the cavity should merely be cleaned out
and tarred. (Fig. 116.) Where the disease can be entirely
eliminated, where the cavity is not too large, and where a filling
will serve the practical purpose of preventing the accumulation of
moisture, the work of filling should be resorted to.
[Illustration: FIG. 118.--A Cavity Filled in a Tree that Should Have
Been Cut Down. Note how the entire interior is decayed and how the tree
fell apart soon after treatment.]
Filling should be done in the following manner: First, the interior
should be thoroughly freed from diseased wood and insects. The
chisel, gouge, mall and knife are the tools, and it is better to
cut deep and remove every trace of decayed wood than it is to leave
a smaller hole in an unhealthy state. The inner surface of the
cavity should then be covered with a coat of white lead paint, which
acts as a disinfectant and helps to hold the filling. Corrosive
sublimate or Bordeaux mixture may be used as a substitute for the
white lead paint. A coat of coal tar over the paint is the next
step. The cavity is then solidly packed with bricks, stones and
mortar as in Fig. 119, and finished with a layer of cement at the
mouth of the orifice. This surface layer of cement should not be
brought out to the same plane with the outer bark of the tree, but
should rather recede a little beyond the growing tissue (cambium
layer) which is situated immediately below the bark, Fig. 120. In
this way the growing tissue will be enabled to roll over the cement
and to cover the whole cavity if it be a small one, or else to grow
out sufficiently to overlap the filling and hold it as a frame holds
a picture. The cement is used in mixture with sand in the proportion
of one-third of cement to two-thirds of sand. When dry, the outer
layer of cement should be covered with coal tar to prevent cracking.
[Illustration: FIG. 119.--A Cavity in the Process of being Filled.]
[Illustration: FIG. 120--The Same Cavity Properly Filled.]
Trees that tend to split: Certain species of trees, like the linden and
elm, often tend to split, generally in the crotch of several limbs
and sometimes in a fissure along the trunk of the tree. Midwinter is
the period when this usually occurs and timely action will save the
tree. The remedy lies in fastening together the various parts of the
tree by means of bolts or chains.
A very injurious method of accomplishing this end is frequently
resorted to, where each of the branches is bound by an iron band and
the bands are then joined by a bar. The branches eventually outgrow
the diameter of the bands, causing the latter to cut through the
bark of the limbs and to destroy them.
Another method of bracing limbs together consists in running a
single bolt through them and fastening each end of the bolt with a
washer and nut. This method is preferable to the first because it
allows for the growth of the limbs in thickness.
[Illustration: FIG. 121.--Diagram Showing the Triple-bar Method of
Fastening Limbs.]
A still better method, however, consists in using a bar composed of
three parts as shown in Fig. 121. Each of the two branches has a
short bolt passed through it horizontally, and the two short bolts
are then connected by a third bar. This arrangement will shift all
the pressure caused by the swaying of the limbs to the middle
connecting-bar. In case of a windstorm, the middle bar will be the
one to bend, while the bolts which pass through the limbs will
remain intact. The outer ends of the short bolts should have their
washers and nuts slightly embedded in the wood of the tree, so that
the living tissue of the tree may eventually grow over them in such
a way as to hold the bars firmly in place and to exclude moisture
and disease. The washers and nuts on the inner side of the limbs
should also be embedded.
A chain is sometimes advantageously substituted for the middle
section of the bar and, in some cases, where more than two branches
have to be joined together, a ring might take the place of the
middle bar or chain.
Bolts on a tree detract considerably from its natural beauty and
should, therefore, be used only where they are absolutely necessary
for the safety of the tree. They should be placed as high up in the
tree as possible without weakening the limbs.