Albert Francis Blakeslee.

Trees in winter; their study, planting, care and identification online

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liquid and are killed.

Preve?itive Measures — The careful selection of species for
planting is undoubtedly the best way of handling the insect prob-
lem' with respect to shade trees. Some trees are remarkably free
from insect troubles, but none are absolutely immune. The spe-
cies in the following list of commonly planted trees are arranged in
order of least susceptibly to insect attack: Ailanthus, Ginkgo,
Sweet Gum, Basswood, Tulip Tree, Carolina Poplar, Horse-chest-
nut, Sycamore, Hackberr}^, the Oaks, the Maples, the Elms, the
Locusts. The least susceptible species, of course, are not always the
most desirable for planting, for they may not possess the other
qualifications of a good shade tree.

Since a large proportion of the shade trees in use belong to sus-
ceptible species, the recommendation concerning the selection of
species applies only to new plantations. Much may be done in


the way of preventing injury by keeping trees growing vigorously.
A strong-growing tree is better able to withstand the attack of in-
sects than a decrepit one. Some insects, like the bark-beetles, cause
serious injury to weakened trees, while they seldom affect vigorous
specimens. The burning of infested branches, leaves, fruit or other
rubbish where insects are likely to hibernate will destroy many
pests and lessen the severity of the attack in succeeding seasons.

Natural Enemies of Insects — Much may be done, also, to guard
against insect depradations by protecting the natural enemies of
the insects. In sections where birds are allowed to collect and are
encouraged to nest, the excessive development of insect pests is pre-
vented. Injurious insects also have many enemies among their
own kind. It is a common occurrence to see a large caterpillar
almost completely covered with small white bodies. These are
the cocoons of a parasitic insect, the earlier stages of which have
been spent within the host insect. Caterpillars thus, affected some-
times survive, but are usually too weak to complete their develop-
ment. Insects affected in this way should not be destroyed by
man, for in doing so he also destroys many useful parasites.

Some insects are attacked also by certain fungus diseases that
exert a marked influence on keeping the pest under control. Owing
to the influence of a fungus parasite, the gypsy moth in its
native home is not a serious pest. AYhen the insect was accident-
ally imported the fungus parasite was left behind, hence the
seriousness of the j^est in this country. A representative of the
United States Department of Agriculture, a short time ago went
to Japan and brought back come cultures of the parasitic fungus.
Efforts are now being made to encourage the development of the
disease amidst the gypsy moths of Maasschusetts.

There are many other examples of insects having been imported
without their natural enemies, and among these are the most serious
pests of trees, such as the San Jose scale, the leopard moth, the
brown-tail moth, and the elm-leaf beetle. Such serious pests as
these and some fungus pests, also, have been imported on nursery
stock and might have been avoided by an adequate system of in-
spection. Some form of legislation is badly needed for the pre-
vention of infested nursery stock coming into this country.

To prescribe the proper treatment for the control of any particu-
lar pest, it is necessary to be able to identify the species causing


the trouble and to know something about its feeding habits. Many
of the failures in spraying may be attributed to the application of
the wrong remedy. Since there are many books and Experiment
Station bulletins relating to specific shade tree pests, it is necessary
here to describe only the most destructive forms. Every state has
its experiment station where insects may be sent for identification
and where advice may be obtained regarding the control of insects
and diseases and other subjects. In the descriptions that follow no
attempt is made at completeness. To call attention to the more
striking characters and habits is the object. The character of the
injury is emphasized because this is usually the most available
means of identification.


Bag ^Vorm — ■ This ins,ect gets its name from the fact that the
larva carries a sort of bag that protects its body. The forepart
of the caterpillar's body projects through the mouth of the bag.
These bags are very conspicuous on trees in winter and contain
the eggs from which the caterpillars hatch during the month of
May. Each young caterpillar immediately after hatching com-
mences to build a sack for itself, using small pieces of leaves and
fastening them together with threads of silk. The bags increase in
size as the insect develops and are from one to two inches in
length when the larva is full grown. The larva feeds on a great
variety of trees, including the evergreens. Allien the insect is ready
to pupate it attaches the bag to a branch or twig and reverses its
position in the bag. In about three weeks the mature insect
emerges in the form of an inconspicuous moth. The male moth
flies' away, but the female moth is wingless and legless and remains
in the bag until she has deposited her eggs, when she wriggles out
and dies.

The pest may be controlled by collecting the nests during the
winter or by spraying with arsenate of lead as soon as the cater-
pillars appear.

Brown-tail Moth — This pest was introduced into ^lassachusetts
about twenty years ago and is now spreading rapidly throughout
the neighboring states and Canada. It feeds on a great variety
of plants and is especially destructive on the Maples, Elms, and
Oaks. The adult moth is snowy-white and is distinguished readily



by the conspicuous brown ending of the body. The female lays
her eggs in July and in the form of an oblong cluster on the under
side of the leaves. The eggs hatch in early August, and the young

Fig. 76. Adult female (nat-
ural size.)

Fig. 77. Egg-mass
on a leaf. (Natural

Fig. 78. The Brown-tail Moth. Winter nests. (Natural size.)



caterpillars commence feeding on the upper surface of the leaves.
A little later, using leaves and silken threads, they build large nests
at the ends of the branches, and as cold weather approaches the
undeveloped caterpillars enter these nests where they spend the win-
ter. From two to three hundred enter the same nest. They come
out in April, feed upon the buds and leaves, finish their growth and
about the end of June become pupae. They remain in this con-
dition for about two weeks, when the adult moths appear. The cat-
erpillars when they appear are about one and a half inches in
length and are abundantly clothed with hairs which often become
broken and fill the atmosphere with fragments. These hairs com-
ing into contact with the human skin cause a serious irritation.

This pest may be controlled by collecting and destroying the
winter nests, and this is probably the most satisfactory method.
Long-handled "toppers" (fig. 49) may be used for this purpose.
Spraying early in May with arsenate of lead, 10 pounds to 100
gallons of water, may also be depended upon to keep the insect
under control.

Canker Worms — These are the familiar measuring worms or
loopers. They are often observed hanging from a tree by a slender

Fig. 79. Adult Female Canker-
Worm depositing her eggs.

thread. There are two closely related species, the fall canker worm
and the spring canker worm. They feed upon many kinds of trees,
but seem to prefer the Apple, Pear, Chestnut, Elm, Hickory, Box


Elder and Maple. The eggs are deposited either in late fall or
early spring, and hatch about Ma}^ first. Usually the young cat-
erpillars completely devour the tissue of the leaves, leaving noth-
ing but the veins. About the first of June they become full grown
and are almost an inch in length. They let themselves down by
means of a silken thread and go into the ground where they remain
in the pupal state until fall. The adults of the fall species
emerge in Xovember and the wingless females may be seen crawling
up the trunks of trees to deposit their eggs on the branches. The
adults of the spring species emerge in March or April.

Since the females cannot fly, they must crawl up the trees to lay
their eggs, and this suggests the method of control. The pest may
be kept completely under control by banding the trees. (See fig.
75). Spraying with arsenate of lead (ten pounds to 100
gallons of Avater) will destroy all insects that hatch from the eggs
already on the trees.

Elm-Leaf Beetle — This is another imported insect and is one
of the worst pests of the Elms. Fortunately its ravages are restrict-
ed to the Elms. Tiie adult beetles are a fourth of an inch in length
and are yellowish, grayish, or dull olive-green in color with an in-
distinct dark line along each side of their back. They usually
spend the winter in the attics of houses or other sheltered places.
They appear early in May and commence feeding on the newly-
formed leaves, making characteristic round holes. During the
latter part of May or early in June the beetles deposit the familiar
orange-colored eggs on the under side of the leaves. These hatch
in about a week and the young grubs commence feeding on the un-
der side of the leaf. The grubs mature in about three weeks and
descend to the base of the tree, where they change to pupae. A sec-
ond brood sometimes occurs.

Spraying the newly-formed foliage in May with arsenate of lead
will usually be sufficient to control the pest, but occasionally a sec-
ond application as soon as the grubs appear, will be necessary.
The pupae around the base of the tree may be killed by spraying
with strong kerosene emulsion.

Gypsy Moth — This destructive insect was imported accidentally
about forty years ago. Its larva feeds on almost any kind of veg-
egation, including all kinds of shade trees and ornamental shrubs.
The eggs are laid usually on the trunks and branches of





trees, but sometimes on fences and buildings, in July or August.
The}' are arranged in oval masses and are covered with short hairs.
The whole mass presents a creamy or yellowish apj^earance. They
remain in this condition until the following May, when the young
caterpillars appear and begin feeding upon the expanding foliage.

Larva Papae " Adults

Fig. 80. The Elm-Leaf Beetle in its various stages.

Fig. 81. Holes
made by the adult
Elm-Leaf Beetles.

Fig. 82. Elm-Leaf Beetle Larvae work-
ing on the under side of a leaf. (Natural



The caterpillars when mature are somewhat over two inches in
length, and are covered with long hairs. In color they are dark
brown with a pair of blue spots on each of the first five segments and
a pair of red spots on each of the remaining six segments. In early
July they change to pupae, and in late July develop into adult

Fig-. S3. A Gypsy Moth eg-g-mass,
natural size, after the larvae have
emerged through the small holes.

moths. The moths measure about five inches across the expanded
wings. The male is smaller than the female and is brown in color.
The female is almost white with dark markings. They are heavy-
bodied insects and, for this reason, do not fly long distances.

One of the most effective means of controlling the pest is by de-
stroying the egg masses during the fall and winter. A sponge sat-
urated with creosote and attached to the end of a long pole is used
for this purpose. A little lamp-black is added to the creosote to
color the egg masses. In Massachusetts, the following creosote
mixture is used: Creosote oil 50 parts, carbolic acid 20 parts, tur-



Fig-. 84. Full-grown Gypsy Moth Larvae.

yrJP: V •*:■' '■'"'■. ^ ■,'..^^3MjSMm$^-v ■''^: - ;:^^

Fig. 85. Adult female Gypsy Moths depositing- egg-masses at
the foot of an Oak Tree.


pentine 20 parts, coal tar 10 parts. With tall trees it is usually
necessary to get up among the branches.

Since the caterpillars feed mostly at night and congregate on
the trunk of the tree during the day, it is possible to trap many of
them under burlap bands. A simple band may be made up by
tying a piece of cheap burlap, eight inches in width^ around the
trunk and turning the upper edge down over the string. The bands
should be examined every afternoon and the trapped insects
brushed off into a pail of kerosene and water.

When infested trees have been sprayed with arsenate of lead (12
pounds to 100 gallons of water) soon after the leaves appear, and
while the insects are small, good results have followed. The full-
grown caterpillars are more resistant to arsenical poisons and may
feed upon the sprayed foliage for a long while before they get
enough to kill them.

Slugs — The larvae of certain insects known as saw-flies, are
slimy-looking creatures and are called slugs. One species is quite
troublesome on the Pear, another on the Willow, and the most de-
structive of all on the Larch. The slugs vary in size according to
the species; the species affecting the Willow being over an inch in
length, while that on the Pear is less than a half inch. The slugs
appear in the spring and lavishly feed upon the developing foliage.
They are readily controlled by spraying with arsenate of lead at ord-
inary strength.

Another insect belonging to this class is known as the Maple leaf-
stem borer. It has entirely different habits from those just de-
scribed. The adult lays its eggs in the leaf-stalk at the base of
the blade of the leaf. The young larva tunnels inside the stem,
eating out the tissue. The affected blades break off and fall to the
ground about June first. The stems containing the insects remain
attached to the ground where they pupate and emerge the following
spring as adult saw-flies.

The insect attacks the Sugar, Norway and Sycamore Maples. It
is not widely distributed and seldom causes serious injury. Spray-
ing the ground well with kerosene emulsion about June 15th when
the larvae are going into the soil, has been suggested.

Spiney Elm Caterpillar — This is the name applied to the
larva of the common "mourning cloak" butterfly. Besides the
Elm, it feeds on the Poplar and Willow. In some seasons it be-


comes a serious pest, but on Elms is controlled readily at the same
time that trees are sprayed for the leaf-beetle. The eggs are laid
early in May and are in cylindrical clusters around the twigs. They
hatch in about two weeks and the caterpillars arrange themselves
in rows facing the edge of the leaf. They completely skeletonize
the leaf, leaving only the veins, and later in the season, only the
mid-rib. When the caterpillars reach maturity, about the first of
July, they are nearly two inches in length, black with white and red
dots, and covered with black branched spines. About this time
they enter the pupal state which lasts about two weeks, when the
adults appear. The butterflies soon commence depositing eggs
which, when hatched, form the second brood of caterpillars.

It is seldom necessary to spray especially for this pest. If found
on young trees they may be jarred off or the affected twigs may be
cut off and the insects destroyed.

The Tent CaterpiUar and Fall Weh-worm — It is a common
occurrence to find unsightly looking webs in trees. These are
caused by tent caterpillars or fall web-worms. The larvae feed
on the foliage, but their chief injury is in giving the tree an
unsightly appearance. A species closely related to the ordinary
tent caterpillar that is commonly found on Apple Trees, is called
the forest tent caterpillar. This insect does not build a tent, but
spins a silky Aveb along the branches and the caterpillars congre-
gate in clusters in much the same way as the other species.

The best method of controlling these pests is to cut off and
burn the webs with the insects. Spraying with arsenate of lead
will kill the young caterpillars, but does not get rid of the unsightly

Tussock Moth — The handsome larvae of this insect is a common
shade tree pest in towns and cities. It feeds on the foliage of
almost all ornamental trees except the evergreens. The insect
passes the winter in the egg stage. The young caterpillars appear
in May and commence to feed on the under side of the leaves,
eating the green portion and leaving the framework. When they
become larger they eat holes through the leaf and when full
grown they eat the entire leaf except the mid-rib.

The full grown larva is very striking in appearance, of yellow
color beneath, with gray strij)es along the sides, and a black stripe
between two yellow ones along the back. Along the sides are a


number of tubercles, each bearing white hairs. Four large tufts
of hair are borne along the back and following these are two

Fig-. 86. Tent Caterpillars resting on the outside of their nest,




bright red tubercles. The head is bright red and is supplied
with two tufts of long black hairs. A single long tuft is borne
on the posterior extremity.

About the first of July the larva spins a silken cocoon, gray in
color and attached to the rough bark of the tree. It remains
in this condition about two weeks when the adult moth emerges.
The female moth which is without wings, about a half inch in

Fig-. 87. White-marked Tussock Moth Larvae on under
side of leaf. (Natural size.)

length, and gray in color, soon commences to deposit her eggs.
The eggs are laid on the outside of the abandoned pupal case or
cocoon. These soon hatch forming the second brood which goes
through the same transformations.


The best way of controlling this pest is in the destruction of
the egg-masses during the winter. This nia}^ be done either by
scraping them off and burning them or by treating them with
creosote in the same way as described for gypsy moth eggs. The
pest may be controlled also by spraying in June with arsenate
of lead at the rate of six pounds to one hundred gallons of water.
By destroying the first brood in June there should be no trouble
from the second brood later in the season.


A2)'lus or Plant Lice — There are many species of aphis affecting
shade trees. As a rule different species attack different kinds of
trees. They are very much alike except in color. The green,
brown, black, and woolly forms are the most common. The insects
pass the winter in the egg stage and often in early spring the
newly hatched lice may be seen in large clusters on the swollen
buds and newly formed leaves. A little later the leaves curl up
and the insects remain inside sucking the juice from the tissue
of the leaf. The insects multiply very rapidly and often cause
much injury to ornamental trees. They secrete a sort of honey-
dew that collects on the foliage and often drops to the ground.
A fungus often develops on this sweet secretion giving it a black,
unsightly appearance.

This pest seldom becomes so serious as to require treatment,
but may be controlled, if remedial measures are necessary, by
spraying with kerosene emulsion as soon as the young lice appear
and before the leaves begin to curl. Fine tobacco powder blown on
the trees after the leaves have curled will be found helpful in
controlling the pest. The use of whale-oil soap, at the rate of
one pound to five gallons of water, is recommended Avhere only a
small amount of spray material is required. It costs a little
more than kerosene emulsion, but is more conveniently prepared.

The Spruce Gall Louse is different from the other species of
this class in that it builds galls on the growing twigs. In some
sections it has become a serious pest of the N'orway Spruce. The
Black, White, and Blue Spruces are also subject to attack. The
eggs are laid about May first, the young lice appearing about a
week later and settling at the base of the new shoots. By some
peculiar form of irritation produced by the insects, a gall-like
swelling is produced. Concealed within these galls the insects



feed upon the juices of the plant. There are two broods in a
season and infested trees soon present an unsightly appearance.

Spraying with kerosene emulsion late in April to kill the adult
insects, is usually recommended. Some claim that spraying with
whale-oil soap, one pound to two gallons of water, gives better


The work of the Spruce Gall-louse.

results. AVhatever is used it should be applied before the galls
are formed. On small trees the pest may be kept under control
by cutting out and burning the galls as soon as they are formed
and while the insects are within.

Scale Insects — The most destructive forms of scale insects are
the cottony maple scale, the woolly maple scale, the San Jose
scale, the oyster-sliell scale, the scurfy scale, and the tulip scale.
They are all small and some of them are so inconspicuous as to
go unnoticed until much damage has been done. The young
insects, as a rule, are active only during the first few days of
their life, after which they settle down, project their beak into the
bark, leaf, or fruit and remain there for the rest of their lives.



As a class, they secrete a waxy or scaly covering to their body
and for this reason are called scale insects. The 'scaly covering
of the San Jose species is circular in outline, either black or
gray in color, and about half the size of the head of a pin. That of
the oyster shell species is elongated, pointed at one end, either

Fig. 89. The San Jose Scale.





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Online LibraryAlbert Francis BlakesleeTrees in winter; their study, planting, care and identification → online text (page 12 of 31)