SB

Be No. 32, THIRD REVISE. Issued December 10, 1907.
C Me ee .
ENT nited States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

THE LARGER APPLE-TREE BORERS.

By F. H. CurrrenpeEn,

In Charge of Breeding Experiments.

Among the most troublesome of the insect pests with which the
fruit growers of the United States have to deal are two species of bor-
ing beetles known, from the appearance of their larve, as the round-
headed and flat-headed apple-tree borers. The first of these belongs
to the family Cerambycide and the other to the Buprestidae. In ad-
dition, there is another species called, after the adult form, the spotted
apple-tree borer and to distinguish it from the round-headed borer,
which it closely resembles. The two species first mentioned are
common and injurious throughout a wide extent of country—the
former to seed fruit trees, the latter also to stone fruit as well as to a
great variety of forest and ornamental trees. The third is a com-
paratively rare insect and rather exceptionally injurious so far as

known.
THE ROUND-HEADED APPLE-TREE BORER.

(Saperda candida Fab.)

Fia. 1.—Saperda candida: a, larva, from side; b, from above; c, female beetle; d, pupa—all
enlarged one-third (original).

INTRODUCTORY REMARKS AND DESCRIPTION.

The round-headed apple-tree borer is, next after the codling moth,
the worst enemy to apple culture in America.
The first intimation that the grower may have of the presence of
this borer in his trees, unless he be forewarned, is in their retarded
13806—No. 32—07

2

growth and the sawdust-like castings, consisting of excrementitious
matter and gnawings of woody fiber, which the larve extrude from
the openings into their burrows. This manifestation is usually
accompanied by more or less evident discoloration of the bark and,
in early spring particularly, by shght exudation of sap.

The parent of this borer is a beautiful beetle, measuring from three-
fourths to nearly an inch in length, the male being perceptibly nar-
rower than the female. The antenne are long, stout, and many-
jointed, being somewhat shorter than the body of the insect itself.
These organs and the legs are gray, the undersurface of the body and
the head are silvery white, and the upper surface is light yellowish
brown with two longitudinal white stripes extending through the
thorax and elytra or wing-covers to the tip, as is shown in the accom-
panying figure 1, c.

The larva, when mature, measures from three-fourths to a little
over an inch in length (22-26™"). It is legless, fleshy, and some-
what grub-like in appearance, cylindrical in form, and light yellow
in color. The head is darker, particularly about the mandibles,
which are nearly black. The first thoracic segment is large-and broad
and bears on its summit numerous small tubercles, placed closely to-
gether. The remaining joints of the body are narrower, the constric-
tions between them being deep and conspicuous. The first seven
abdominal segments bear on the upper surface of each a peculiar
elevated process, as shown at figure 1, b.

The pupa, illustrated at d, is nearly as long as the adult insect,
which it resembles in a superficial manner, the head being bent down
toward the breast, and the legs and long antennz folded upon the
ventral surface. Its color is similar to that of the larva.

Saperda candida was given its specific name by Fabricius in the year
1787, and was again described as new by Thomas Say, in 1824, under
the name of S. biwittata, the latter remarking at the time that it
injured apple trees by boring into the wood.

DISTRIBUTION.

This species is native to this country and is present in injurious
numbers in practically every State of the apple-growing region east of
the Rocky Mountains. It inhabits, like so many other injurious in-
sects, the upper austral and transition life zones, comprising the better
agricultural portion of all except the extreme southern States. It has
been reported to occur in one locality, Agricultural College, Miss.,
which lies in what is considered the lower austral zone. As with
many other noxious species, too, it is in the older States, particularly
of New England and New York, where orchards have been long estab-
lished, that injuries are most pronounced. Until recently this species

[Cir. 32]

3

was not known as especially injurious about the District of Columbia,
but at the present time it has become very abundant and destructive,
whole orchards both of young and mature trees having succumbed to
its ravages.

Its known distribution includes Canada, all of the New England
States, New York, New Jersey, Pennsylvania, Delaware, Maryland,
Virginia, West Virginia, District of Columbia, Ohio, Illinois, Michigan,
Towa, Missouri, Kansas, and restricted localities in Texas, Alabama,
and Mississippl.

FOOD PLANTS AND NATURE OF INFESTATION.

This borer is practically limited in its food to the apple and kindred
woody plants. It is most injurious to quince and apple, and some-
what less so to pear. It infests also crab apple and thorns of different
species, mountain ash, chokeberry, and juneberry—in short, practi-
cally all except one or two kinds of trees and shrubs belonging to
genera included in the family Pomacez. The wild plants are its natu-
ral food, but certain varieties, at least, although often inhabited by
this inseet, are for some reason not so susceptible to its injury as are
our cultivated trees. This species inhabits more particularly the base
of the trunk of trees, often being found below the surface of the earth,
especially in young nursery stock. It is to such trees that it is most
injurious, for it soon works around the trunk, separating the wood
from the bark, interfering with the flow of sap, and producing the
effect of girdling, a result which is very apt to be produced even when
no more than two or three larve occur on the same tree. Very fre-
quently four or five larve dwell together in a single small tree and in
a short time injure it quite beyond recovery. In old trees larvee occur
somewhat higher up the trunk, in exceptional cases at a distance of
several feet from the base or even, still more rarely, in the lower limbs.
As arule, however, they are seldom found except within a foot or two
of the base. Trees of all sizes are frequently killed or weakened to
such an extent that they are unable to mature a full crop of fruit.

The experience of many years shows that injury follows where
grasses, weeds, or other rank vegetable growth are permitted to accu-
mulate about the trunks of the trees, since the beetle, like all nocturnal
insects, naturally seeks concealment, and the conditions thus afforded
are most favorable for its attack on cultivated plants.

*LIFE HISTORY.

The beetles make their first appearance of the season late in May or
in June, according to locality. During the night they come forth from
the trunks of the trees in which they have bred, and at this time may
be seen in flight. During the day they hide away in some secluded

[Cir. 32]

4

place, under leaves or in similar situations, on the trees which they
inhabit.

Soon after their first appearance the sexes mate and eggs are de-
posited. The female first makes an incision in the bark—probably by
means of her mandibles—causing it to split shghtly; then, turning
head upward, she places an egg under the bark nearly a quarter of an
inch from the incision, accompanying the deposition by the extrusion
of ‘a gummy fluid which covers and secures it to its place and usually
fills up the aperture. In young trees with tender bark the egg is
usually thoroughly hidden, while in older trees it is sometimes so
shallowly imbedded as to be readily seen.”

“The egg is pale rust-brown in color, one-eighth of an inch long,
one-third as wide at the middle, flattened so as to have a depth of
about one-third the width.” 7 Its shell is fairly tough and resistant,
not sculptured, and sufficiently plastic, when laid, to receive impres-
sions from the woody fibers between which it is forced. Oviposition
has been observed from June to September in a single locality (Law-
rence, Kansas), but June is the month in which most of the eggs are
laid. Fitch and others observed the beetles in the trees, neap Albany,
_N. Y., as early as April.

_ Regarding the duration of the egg stage, Mr. E. W. Junkins ® states
that a young borer larva was observed July 7 from eggs that were
deposited June 15. This would give a period of twenty-two days, but
we have no further data bearing on this point.

The larve, soon after hatching, tunnel under the bark and feed on
the sap-wood, gradually working their way upward and afterwards
downward, usually remaining within a short distance of, or below the
surface of, the ground, particularly in young trees. By the beginning
of the second year the larve, according to observations conducted by
the writer, attain an average length of about five-eighths of an inch.
The larval growth will naturally vary according to temperature, mois-
ture, quantity of food available for consumption, and other condi-
tions. With the approach of cold weather the larve cease feeding,
but with the beginning of warm spring weather—in the District of
Columbia as early as the latter days of March—they again commence
forcing their excrement and castings, consisting of gnawed particles
of wood, out through holes which they make in their burrows. By
the end of the second year the larve have increased considerably in
size and have now penetrated deeper into the solid heart-wood, their
burrows being closely packed behind them with castings. The third
year the larve gnaw outward to the bark, form a pupal cell composed

@ Above quotations from account by Riley in New York Weekly Tribune, Feb. 20,
1878; Kans. Hort. Rept. for 1879, pp. 196-201.
b New England Homestead, Jan. 3, 1885.

[Cir. 32]

5

partly of their castings and, with their heads pointing toward the bark,
transform to pupe. With the approach of May and June they cut
their way out by means of their powerful mandibles and issue through
a round hole as mature beetles. A larva was observed by the writer
at the Department of Agriculture that pupated May 11, and appeared
as adult May 30, thus giving nineteen days for the pupal period, the
weather being seasonable.

NATURAL ENEMIES.

Concealed as this insect is during its three years of existence in its
preparatory stages, it is nevertheless a prey to natural enemies which
seek and devour it in its haunts under the bark. Of this number are
woodpeckers and hymenopterous insect parasites. Of the latter only
a single species is known to the writer, Cenocelius populator Say.*

METHODS OF CONTROL.

After borers have once entered a tree there is no better remedy
known than to cut them out with a knife or other sharp instrument.
In the treatment of this insect an ounce of prevention is worth several
pounds of cure. Cutting the borers out, unless practiced with the
greatest care, is apt to result in injury, and it is far better to prevent
the parent insects from depositing their eggs upon the tree. This is
not difficult of accomplishment, as oviposition is practically confined
to two months in any single locality, usually June and July. The best
preventives are impenetrable substances placed about the trunk and
various washes of a repellent nature.

Cutting out by hand.—Little has been gained in the line of direct
remedies for this borer until recent years. The early writers had noth-
ing better to advise than cutting out the larve, either with a knife or
gouge, or killing them by inserting a wire into their burrows. These
remedies were in use early in the present century and are still the ones
most often practiced. It isno uncommon thing to find four or more
larvee in a single small trunk, and the cutting out of all of them, if not .
practiced with the greatest caution, is apt to result in the girdling of
the tree, if, indeed, this has not already been accomplished by the com-
bined attack of the borers themselves. It would seem superfluous to
add that it is best to cut the borers out as soon as detected. Their
presence may be known bya little experience, some persons being so
expert in detecting their exact location as to be able to kill them with
a knife thrust or by the puncture of an aw] or other sharp instrument.
The fruit grower should institute a practice of inspection so that the
borers may be removed as often as found.

[Cir. 32]

r

6

To assist a tree in recuperating after it has been girdled, a bridge or
two should be made by splitting a piece of apple twig (say of an inch
or two in thickness), cutting it diagonally on the inside, and applying
to the surface at the base of the tree. It should then be tied on and
grafting wax applied to each end, after which a fertilizer should be
applied and the whole banked over with earth. It is also well to keep
the tree watered for a few weeks after treatment.

Mechanical preventives.—This is one of the borers that can readily
be controlled by different sorts of mechanical barriers placed about the
base of the tree. For this a few thicknesses of newspaper wrapped.
rather loosely about the trunk and extending about two feet from the
base are all that is necessary. This covering should be tied, by pref-
erence with cord, which will readily yield or break with the natural
expansion of the tree in its growth, and also be tightly fastened at top
and bottom and hilled up with earth so that the beetles can not obtain
access to the tree from below. From the top of this covering upward
it is best to use some deterrent alkaline or carbolated wash. Instead
of newspapers, Wire gauze or mosquito netting may be used, and
should be put in place so as to loosely encircle the tree, that the beetles
may be debarred from depositing their eggs between its meshes and
that the growth of the tree may not be hindered. Both devices have
been successfully employed for a long period of years, and there is
abundant testimony to their value. If the netting or paper be put in
place early in May, it will not only prevent the beetles from oviposit-
ing during the next two months, but will also keep the insects which
might be present in the trunk from issuing, and they will die in their
burrows without being able to lay fertilized eggs. The paper wrap-
ping must be removed each season, but the wire netting will last for
several years. It is safe to remove either, ordinarily, after the first of
September.

Protective washes.—Any one of several washes in general use against
boring insects may be used as a deterrent. A good alkaline wash is
prepared of soft soap reduced to the consistency of thick paint by the
addition of caustic potash or washing soda in solution. A good fish-
oil, or whale-oil, soap, or common soft soap, is often used, and in some
cases any one of these is sufficient to deter the insects from depositing
their eges. The alkaline wash may be carbolated, if desired, by the
addition of crude carbolic acid, at the rate of 1 pint to every 10 gal-
lons of the wash. Such a wash not only affords protection against
this and. other borers, but against scale and fungous diseases at these
points, and is, moreover, of positive benefit to the tree. Caustic pot-
ash fish-oil soaps are among the best for insecticides.

Whatever wash is used should be applied thoroughly, and in locali-
ties where apple-tree borers are unusually troublesome the larger

(Cir. 32]

7

branches should also be covered as far as possible. The wash may be
best applied with a whitewash brush and should be renewed at inter-
vals of from two to four weeks, as found necessary, the first applica-
tion being made before the appearance of the insects in May or June
and again during July.

It is well to scrape old trees to remove dead bark scales, care being
taken not to cause any abrasion. Scraping is best done some time
before the application of the wash so that the wounds that might be
made may have opportunity to heal before the appearance of the
beetles.

The beetles are shy, and so seldom seen that it is doubtful if any
method of destroying them is feasible. They are attracted to lights at
night to some extent, and some meet their end-in this way.

Kerosene as a remedy.—A great variety of substances has been
recommended to kill the borers in the trees, but up to the present time
only a few have given satisfaction. For the benefit of those who
have not had experience with this borer it may be necessary to state
that it is of no avail whatever to inject kerosene or any other insecti-
cide into the round holes made by the beetles in their escape from
the trees. A correspondent of this Bureau, Mr. T. B. Ashton, who
has had many years’ experience with this borer, states that there is
no better way of effectually putting a stop to the depredations of this
and similar borers than in the use of kerosene applied freely wherever
the castings of the larvee are to be seen protruding through the bark.
The kerosene is absorbed by the castings and, carried by capillary
attraction, permeates the entire burrow. It thus comes in contact
with the larva, which soon succumbs. The amount of kerosene
necessary is so small that it does not endanger the health of the tree.

Clean cultural methods.— Finally, clean culture, the best preventive
for insect injury of whatever kind, should not be neglected. The
nursery should not be started in new localities where crabapples,
thorns, juneberry, and other wild food plants of this species grow in
great profusion, nor in the vicinity of neglected orchards, nor should
rank growths of weeds, grasses, bushes, and briars be permitted to
accumulate about the trunks of the trees. When a tree is seen to
be injured beyond recovery it should be taken out and destroyed by
burning before the following spring, so that the larvae: which it con-
tains may not have an opportunity to develop and infest healthy
growth.

THE SPOTTED APPLE-TREE BORER.

(Saperda cretata Newm.)

A related insect very similar to the preceding, both in appearance
and in habits, is the spotted apple-tree borer. The beetle is of
nearly the same size and form, differing superficially by having two

[Cir. 32]

8

white spots on each elytron (fig. 2) instead of the longitudinal white
lines which distinguish the latter (fig. 1, ¢). The larva and pupa are
so similar that no description need be made of them. Although
the species has a fairly wide distribution, corre-
sponding somewhat closely to that of the com-
mon species, specific injury by it has only been
noted in two States, namely, in Michigan by
Prof, A. J. Cook and in Iowa by Prof. H. Osborn.
\ In the former State this borer is reported. as
‘quite as common and destructive as Saperda
candida. Its occurrence is recorded, also, in
Trae 2 sa erddicretqias tte: Canada, Massachusetts, New York, Pennsylvania,

male beetle—enlarged one- Wisconsin, and Ohio, and there are specimens in

eee the National Museum from northern Illinois and
Texas. Apple and wild crab are the only plants which it has been
observed to injure, but its occurrence has been noted on juneberry
and thorn. According to Osborn the ‘“‘eggs are evidently laid in
pairs, half an inch or more apart, along the branch, the larve of each
pair upon hatching working in opposite directions around the branch,
at first just beneath the bark, afterwards (probably after the first
year) entering the hard wood.”

The remedies for this species are the same as for the preceding
with the extra precaution that the larger branches, also, be protected
by the wash applied.

THE FLAT-HEADED APPLE-TREE BORER.
(Chrysobothris femorata Fab.)
GENERAL APPEARANCE AND NATURE OF INJURY.

A much less dangerous, though more abundant, insect than any of
the preceding, is the flat-headed apple-tree borer. . It belongs to the
short-horned wood-borers or metal-
lic beetles of the family Buprestide,
and differs remarkably from the pre-
ceding in all its stages as well as in
its habits and life history.

The adult insect (represented at
b, fig. 3) measures from a little less
to a little more than a half inch in
length. It is flattened above and
bears some resemblance to a snap-
ping beetle, but, unlike the Elateri-

: ; ‘ ; = Fig. 3.—Chrysobothris femorata: a, larva; b,
dee, is not provided with jumping _ beetle; ¢, head of male; d, pupa—twice nat-

: < al size (original).
organs. The antenne are short and =" *”° omsinal)

serrate, the eyes large and conspicuous, and the forelegs are armed in
front with a conspicuous tooth. The upper surface of the body is
[Cir. 32]

9

dark metallic brown, and fresh specimens are coated here and there
with a powdery gray substance, which is easily rubbed off. The wing-
covers are ornamented as shown in the illustration, and underneath,
as may be seen when the insect is in flight, the body is a bright metallic
greenish blue. The under surface is coppery bronze. The males are
smaller and may be further distinguished from the females by their
green heads, as well as by other characters (see fig. 3, ¢).

Unlike the round-headed borer the present species is diurnal in
habit, being most active in the heat of the day and commonly found
on prostrate trees and logs, or on injured trunks, basking in the sun-
light. The beetles are active creatures, running rapidly and flying
readily.

This borer attacks diseased or dying trees by preference, inhabits
all parts of a tree from the base of the trunk to the limbs, and is not
restricted to fruit trees, but attacks a variety of deciduous trees, also.

In all these respects it differs from the round-headed borer, but
agrees with the latter in that it is injurious chiefly to young trees, its
injuries being practically confined to newly transplanted nursery stock
and to trees which have been weakened through any cause, such as
careless pruning, or insufficient nourishment due to poor soil or
drought. There is a difference of opinion as to the nature of damage,
some writers taking the stand that healthy trees are not injured at all.
It is a well-known fact that many forms of boring insects prefer injured
plants, but when these are wanting do not hesitate to attack perfectly
sound growth, and records show conclusively that the present species
is included in this category. The general opinion is that trees suffer-
ing from “‘sun scald” are most subject to attack, and the opinion has
been expressed that injury known under this name is in reality due to
the work of this borer. The beetle is essentially a sun-loving species
and deposits its eggs almost exclusively on the southern or south-
western side of standing trees or on recently felled logs that are exposed
to direct sunlight. Observation leads us to have doubts as to the
ability of the young larve to withstand the strong flowing sap of vig-
orous trees.

Infestation may be detected by the discoloration of the bark.

A list of the recorded food plants of this borer includes, among
orchard trees, apple, pear, and peach; and of shade and forest trees,
mountain ash, oak, maple, box-elder, hickory, chestnut, sycamore,
horse-chestnut, linden, and willow. To this list should be added plum

Nore.—A third species of Saperda, fayi Bland, has similar habits and is likely to
attack apple and similar cultivated pomaceous trees, but is thus far known only on
thorn. A full account of this species was published by the late Dr. Hamilton (Can.
Ent., Vol. XX, pp. 6-8).

(Cir. 32]

10

and cultivated redbud (Cercis chinensis),* from which the species has
been reared by the writer, and currant.?

Cherry, beech, and white birch are probable food plants, although
the beetle has not been reared from them, and elm, tulip, and cotton-
wood have been mentioned as such, but on what authority is not clear.
Oak is without doubt the favorite natural host tree.

The larva differs greatly from that of the round-headed borer. Its
name, flat-headed borer, is derived from the peculiar flat expansion of
the second thoracic segment—which is close to the head. In color it
is light yellow and in length measures nearly twice that of the mature
insect. It habitually rests in a curved position, more bent usually
than shown in the illustration (fig. 3,a@).. The pupa (d) shows the form
of the future beetle and is of the same yellow color as the larva.

This species inhabits practically the entire United States and the
southern portion of Canada, being, like the preceding, a native of
North America and injurious year after year.

NATURAL HISTORY AND HABITS.

The beetles make their appearance about the same time as the
round-headed borer in regions infested by both species—after the
middle of May in the principal apple-growing regions of the Northern
States—and continue through the month of July and, it is said, even
into September, the female depositing her eggs in cracks and grooves
or under bark scales upon the trunks or branches of trees destined to
be the future food of the larve. Most frequently several eggs are
found together. These are yellow in color, irregularly ribbed, and
about one-fiftieth of an inch in length.© The larva differs from the
round-headed borer in that only a single year is required for its devel-
opment, pupation occurring in the spring shortly before the appear-
ance of the beetles. It differs, also, in its manner of work, living for
the most part just beneath the bark, where it excavates broad, flat,
and very irregular channels. Sometimes, however, it enters more
deeply into the sap-wood. Like many other borers, it will often girdle
a small tree, a single individual being capable of killing a small tree in
this manner. As it approaches maturity it generally eats deeper into
the solid heart-wood, but in spring, just before transformation, it
works back again into the bark and there constructs its pupal chamber.
It is said to remain in the pupa state about three weeks,” whereupon
the beetle cuts its way out, leaving in the bark an elliptical exit hole
which distinguishes its work from that of the round-headed borers,
which make round holes in their exit. These holes correspond to a
cross-section of the beetle making them. In the North the winter

@ Formerly C. japonica.
6 ¥. H. Hillman, Nevada Exper. Station, Bul. 36, p. 18.

eC. V. Riley, Proc. Ent. Soc. Wash., Vol. III, p. 92.
[Cir. 32]

iil

months are passed as larvee, but farther south, in the District of
Columbia, according to recent observation, pupation may take place
as early as November of the first year.?

NATURAL ENEMIES.

Among natural enemies, woodpeckers and ants are effective destroy-
ers of this species, since they devour larve and pupex under the bark.
A number of parasitic insects, also, prey upon it and: assist greatly in
restricting its abundance.?

REMEDIES.

The remedies advised for the round-headed borer are also of value
and are generally employed against the present species. It is neces-
sary, however, that deterrent coverings and washes should be applied
farther up the trunk and to as many branches as can be conveniently
reached. As this, however, necessitates additional labor and extra
expense, other preventive measures are also recommended.

Trap wood for the beetles.—For this purpose any sort of tree known
to be freely attacked by this borer, e. g., oak, maple, or any fruit
tree, may be used. If a few limbs or trunks of newly felled trees be
placed at intervals of, say, 30 or 40 feet, on the outskirts of orchards,
where they are freely exposed to the sun, the beetles will be attracted
for the deposition of their eggs, and all that will then be necessary
will be to destroy the trap wood by burning before April or May of
the following year. This plan has not been practically tested, but
the writer has no doubt that it would prove useful in securing im-
munity from this pest in the orchard, provided that no diseased fruit
trees be left for food.

Careful cultural methods.—Careful, clean methods of orchard man-
agement are essential as a measure of protection, and involve the
cutting out of dead, dying, and injured deciduous forest and shade
as well as orchara trees known to be chosen as food by this species,
Care should be exercised in transplanting, and especially in pruning;
and fertilizers should be used in order that the trees may be thrifty
and better able to withstand attack. Proper regard for these meas-
ures should give practical exemption from injury.

Approved:
JAMES WILSON,
Secretary of Agriculture.
Wasuineton, D. C., April 8, 1905.

aC. V. Riley, Proc. Ent. Soc. Wash., Vol. III, p. 92.
© The list includes the Braconids, Bracon charus Riley and B. pectinator Say, Spathius
pallidus Ashm., and the Ichneumonids, Labena apicalis Cr., and L. grallator Say, and
one or more species of Chalcididz, noticed by Fitch as occurring in New York and by
Riley in Missouri.
Norre.—First issue, July 1, 1898; revise, August 30, 1902.
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