SB

818
C576
ENT
Issned Januarvr 27, 1912.
-U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ENTOMOLOGY—CIRCULAR No. 1438.
L. O. HOWARD, Entomologist and Chief of Bureau.
INSECT DAMAGE TO STANDING TIMBER
IN THE NATIONAL PARKS.
‘ BY
ASD. HOPKINS,
In Charge of Forest Insect Investigations.

19240°—Cir. 143—12

€

220043

BUREAU OF ENTOMOLOGY.

L. O. Howarp, Entomologist and Chief of Bureau.
C. L. Mariatt, Entomologist and Acting Chief in Absence of Chief.
R. S. Crreron, Hwrecutive Assistant.
W. F. Taster, Chief Clerk.

I. H. CHITTENDEN, in charge of truck crop and stored product insect investigations.
A. D. Hopkins, in charge of forest insect investigations.

W. D. Hunter, in charge of southern field crop insect investigations.

EK. M. WesstTer, in charge of cereal and forage insect investigations.

A. L. QUAINTANCE, in charge of deciduous fruit insect investigations.

i. F. Parciirs, in charge of bee culture.

D. M. Roaers, in charge of preventing spread of moths, field work.

Rotia P. Currier, in charge of editorial work.

Masrt Coxrcorp, in charge of library.

4

Forrest INSrect INVESTIGATIONS.
A. D. HopKins, in charge.

H. EB. Burke, entomological assistant, in charge of Forest Insect Field Station 5,
Yreka, Cal.

W. D. EDMONSTON, agent and expert, in charge of Forest Insect Ficid Station 6,
Klamath Falls, Oreg.

JOSEF BRUNNER, agent and expert, in ane of Forest Insect Fieid Station 1,
Columbia Falls, Mont.

EK. B. Mason, entomological assistant, in Seine of Forest Insect Field Station 7,
Spartanburg, S. C.

T. BH. Snyper, agent and expert, engaged in investigations of insect damage to
telegraph and telephone poles.

J. L. Wess, entomological assistant, specialist on cerambycid beetles and larve.

S. A. RoHwer, agent and expert, specialist on sawfliecs (Tenthredinoidea).

Mary FE. Faunce, Mary C. JoHNSON, MAUDE TAYLOR, ELIZABETH RITCHIE, pre-
parators.

It

CIRCULAR No. 143. Issued January 27, 1912.

United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

L. O. HOWARD, Entomologist and Chief of Bureau.

INSECT DAMAGE TO STANDING TIMBER IN THE
NATIONAL PARKS. *

By A. D. HorxKIns,
In Charge of Forest Insect Investigations.

CHARACTER OF THE DAMAGE.

The damage by insects to the living trees of the forests and orna-
mental grounds of the national parks consists of injuries to the
foliage, branches, or the entire tree which mar or destroy their
attractive, educational, and historic features and diminish or destroy
their commercial value.

Throughout the forests of the Rocky Mountains and Pacific slope,
including the national parks, a large percentage of the timber has
died during the past half century. The old standing and fallen dead
trees, the red foliage of those that died last year, and the fading
tops of those now dying bear evidence of the work of insects and
are conspicuous examples of a great waste of forest resources. In
some localities a few scattering trees die each year within a town-
ship or section; in others, clumps of trees or whole forests die during
a single year.

The conifers, which are the predominating trees of this western
part of the country, are subject to a high death rate from insect
attacks. The pines, the spruces, the Douglas fir, the balsam firs,
the hemlocks, the cedars, and the Sequoias (redwoods) have each at
least one destructive enemy.

In the fall, spring, and early summer the dying and recently dead
trees are conspicuous on account of their fading, yellowish-red, and
reddish-brown foilage, as if injured by fire. When they are in
large patches, or extend over a considerable area, their death is
often attributed by the casual observer to forest fires.

1This paper was read by the author at a conference of national park superintendents

held under the auspices of the Secretary of the Interior, September 11-12, 1911, and
is embodied in the proceedings of the meeting issued by the Interior Department.

1

2 INSECT DAMAGE IN THE NATIONAL PARKS.

EXTENT OF THE DAMAGE,

The extent of the damage to the forests by insects through the
accumulation of dead timber and the dying of matured trees over
large areas is vastly greater than the general observer would suppose.
In fact, the dead and fallen timber is so common in all forests that
it has heretofore been recognized as a natural and inevitable condi-
tion. Large areas of insect-killed timber have been charged to fire
without further thought or examination to determine the real cause.
Fallen timber has been attributed to storms, and scattering dead
trees to old age.

During the present year a reconnaissance was made of typical
sections in one of the national forests, where there was no evidence
that destructive forest fires had occurred during the past 20 years.
It was found that the standing and fallen dead yellow pine that
had died within that period amounted in board feet to nearly half as
much as that which was then living, and of the sugar pine and
Douglas fir there was one-fourth as much dead as was then living,
and every dead tree examined in the estimate showed evidence that
it had been killed by insects.

In the Black Hills National Forest of South Dakota over one-half
of the timber died within a period of about 10 years. In Oregon
and Montana nearly all of the larger pine died within a few years
on areas of a few hundred acres to 100,000 acres or more. These
together with many other examples of extensive dying of timber
have been investigated and found to be caused primarily by insects.
Investigations have also demonstrated beyond question that a vast
amount of timber is killed by insects every year within the forested
areas of the Rocky Mountain and Pacific Coast regions. Further-
more, the accumulation of this dead timber and fallen débris is a
menace to the living, because it furnishes fuel for destructive forest
fires. The losses from insect depredations are thus augmented by
fires.

The extent of damage to the forest and other trees of the national
parks has not been estimated and, with the exception of investigations
conducted in the Yosemite and Glacier Parks, we do not have much
direct information as to the damage already done. It is plain to us,
however, that the general conditions are not different from those
which prevail throughout the regions in which the parks are located
and in which the destructive species of insects are known to oceur.

The amount of damage in the parks must be considered not only
on the basis of the commercial value of the forest resources, but on
that of the esthetic and educational value of the virgin forest with its
typical examples of tree species.

The loss of a section of the forest which forms the attractive fea-
ture in the landscape, or is the only remaining example of the origi-

INSECT DAMAGE IN THE NATIONAL PARKS. 3

nal type of forest growth of that region, is far greater than that rep-
resented by the commercial value of the timber; as is also the loss of
notable veterans and giants of the different species. These old forests
and old trees are at present one of the attractive and instructive fea-
tures of the timbered areas of some of the national parks, and if they
are protected from their insect and other enemies they will be even
more attractive features in coming centuries. Under present condi-
tions, these old trees of the virgin forest are in greater danger of
being killed by insects than are the younger trees. Indeed, many of
them have been killed within recent years.

The three giant sugar pines on the trail from Wawona to Glacier
Point and the Yosemite Valley are examples. Two of them were
dead and the other was dying when I saw them in June, 1904, and
there was conclusive evidence that their death was caused by the
mountain pine beetle. The veteran sugar pine, known as “ Uncle
Tom,” was being attacked at that time ia the same species of beetle,
and I am ceed that it died the following year. The loss of tues
four giants of the species is irreparable.

The Sequoias are supposed to be immune to the attack of insects,
but they are not. They are more resistant than other species, and
that is one reason they have lived so long. However, each species
has a barkbeetle enemy which, under favorable conditions, is capable
of killing the largest and finest specimens. I saw one of the large
redwoods in the vicinity of Eureka, Cal., that had been killed by its
barkbeetle enemy, and when in the Mariposa Grove, in 1904, I dis-
covered the barkbeetle enemy of the big tree in the living bark of a
storm-broken limb.

THE PRINCIPAL DEPREDATORS.

The mere mention of the names of the thousands of species of in-
sects, each of which causes some peculiar injury during the life of the
different tree species, would occupy more space than is allotted for
this paper. Therefore we must consider the more important of those
which are directly responsible for the death of the trees.

The little genus of Dendroctonus beetles, or tree-killing beetles, is
represented in the Rocky Mountain and Pacific Slope regions by a
few species which are more destructive to the conifers of western
North America than all other forest insects combined. They are a
constant menace to the pine, spruce, and Douglas fir of the national
parks. They are certain to be present in every park in which there
are forests of their host trees, and have doubtless caused far greater
damage than the park officials have realized.

The species, in the order of their destructiveness, are the mountain
pine beetle, the western pine beetle, the Engelmann spruce beetle, the

4 INSECT DAMAGE IN THE NATIONAL PARKS.

Jeffrey pine beetle, and the red turpentine beetle. All but the Jeffrey
pine beetle of the Sierras are common to the northern Rocky Moun-
tains and the Pacific Slope. Those common to the central and south-
ern Rocky Mountains are the Black Hills beetle, the Engelmann
spruce beetle, the Douglas fir beetle, and the red turpentine beetle.
There are three other species common to the southern Rocky Mount-
ains and northern Mexico which are of less importance in causing
the death of trees.

These insects are small, stout, black to reddish-brown beetles, rang-
ing in length from about 2 mm. to 9 mm., or 0.08 to 0.36 of an inch.
They fly in the period from April to October and attack the main
trunks of the living healthy trees by boring into the bark and ex-
cavating long winding or nearly straight egg galleries between
the bark and wood. In this manner they completely girdle and thus
cause the death of their victims. As soon as the bark begins to die the
eggs deposited by the beetles hatch and the young grubs, or larval
forms, complete the destruction of the inner bark. All of the broods
develop into the adult stage within a year and emerge from the
bark to fly in search of new victims. Each species has its peculiar
habits in the choice of host trees, methods of attack, and period of
development.

THE MOUNTAIN PINE BEETLE.

The mountain pine beetle attacks the mountain or silver pine, sugar
pine, western yellow pine, lodgepole pine, and evidently all other
pines of the northern Rocky Mountains and the Pacific slope. The
adult beetles fly in the period from July to October, inclusive. When
abundant they concentrate their attack on clumps and patches of
trees. Their long, nearly straight egg galleries and radiating larval
mines soon kill the bark on the main trunks, but the foliage of the
infested trees remains green and apparently healthy until the follow-
ing May and June. It then begins to change to a pale green and
later to yellowish and brown. By the time all of the foliage is dead,
about the Ist of July, the overwintered broods of beetles begin to
emerge. By the middle of August most of them are out of the dead
trees and have entered the living ones.

This is by far the most destructive insect enemy of the pine within
its range, and under present conditions is a constant menace to the
forests of matured or merchantable-sized timber. It can be con-
trolled by felling the infested trees and by removing the infested
bark from the main trunks without burning the bark or tops. This
work must be done during the period between the Ist of October and |
the 1st of July to destroy the broods of the beetle before they emerge.
Whenever the timber can be utilized the product will pay all ex-—
penses. If it has no commercial value it will cost on an average

INSECT DAMAGE IN THE NATIONAL PARKS. 5

50 cents a tree for the required treatment. After an outbreak is
under control the living timber can be easily protected from further
depredations by giving prompt attention to the felling and barking
of any clumps of dying trees found during May and June. Rangers
or fire patrolmen can be instructed so that they can do this and any-
thing else that is required to maintain control.

THE WESTERN PINE BEETLE.

The western pine beetle attacks the western yellow pine, the sugar
pine, and the Jeffrey pine. The beetles fly in late June to October,
inclusive, and usually attack scattering individual trees, often select-
ing the larger and older examples. The adults excavate winding
egg galleries between the inner living bark and the wood and trans-
form to the adult stage in the outer bark. The beetles begin to fly
and attack the trees in June and continue the attack until October or
November. The first generation develops and emerges in August to
November, and the second generation passes the winter in the trees
that are killed by it in the summer and fall.

The foliage of the infested trees begins to fade and turn yellow in
a few weeks after the trees are attacked by this beetle. The summer
broods of the first generation leave the trees by the time the foliage
is reddish brown, but the overwintered broods do not emerge until the
following May and June, in some cases several months after the
foliage is brown.

This species is next in importance to the mountain pine beetle
as a destructive enemy of the pine, and the two species often combine
in their attack. In this combined attack the western pine beetle is
a secondary enemy of the trees because it follows the attack of the
other species. When it is the primary enemy it is responsible for
the death of a few scattering trees each year throughout the forest,
which results in. the accumulation of dead timber. * In the aggre-
gate, this accumulative loss is very extensive, involving, as it does, the
largest and best trees.

The insect can be controlled and the living timber protected from
its ravages by felling the infested trees during the period between the
1st of October and the ist of June and removing the bark from the
main trunks and burning it. It is necessary to burn the bark because
the broods of this species transform in the outer bark. They are not
destroyed by simply exposing the inner bark, as is the case with the
mountain pine beetle.

THE JEFFREY PINE BEETLE.

The characteristic habits of the Jeffrey pine beetle are similar to
those of the mountain pine beetle, and therefore it requires the same
treatment.

6 INSECT DAMAGE IN THE NATIONAL PARKS.
THE DOUGLAS FIR BEETLE,

The Douglas fir beetle attacks the Douglas fir, the big-cone spruce,
and the western larch. The beetles fly in April and May and enter
the living bark on healthy trees and on trees that have been injured
by fire and those that have been recently felled. In habits of attack
and general characteristics the Douglas fir beetle is similar to the
mountain pine beetle, except that the former begins to fly earlier
in the season and the foliage of the trees infested begins to die in
the fall. It is very destructive to the Douglas fir throughout the
Rocky Mountain region from British Columbia to Mexico, but is
much less so on the Pacific slope, especially toward the coast. It
can be controlled by felling the infested trees during the period
between the 1st of September and the 1st to middle of the following
April and removing the infested bark from the trunks without
burning.

THE RED TURPENTINE BEETLE.

The red turpentine beetle is the largest species of the genus Den-
droctonus. It begins to fly in April and is active until October and
November. It attacks the pine and rarely the spruce. As a rule it
confines its operation to the base or basal portion of the trunks.
While its normal habit is to breed in the bark of stumps and logs of
newly felled trees, it often infests the bark on healthy trees. It
rarely kills a tree, but is the cause of a large percentage of the basal
wounds known as “cat faces” and fire wounds, so commonly met
with in the pine. This is a far more difficult species to control than
the others because it breeds in the stumps of felled trees and the base
of those killed by the other species or by fire. Valuable individual
trees can be protected by cutting the beetles out of the bark as soon as
their presence is indicated by masses of exuding resin mixed with
reddish boring’ dust.

Wherever there are continued lumbering operations the red turpen-
tine beetle confines its attack to the stumps, but in the national parks
and private grounds where a limited amount of timber is cut, or
where the ravages of the mountain pine and western pine beetles
have been contntier it is likely to cause more or less extensive dam-
age to the living timber for a year or two aiter.

In combating) the other beetles in the national parks, care should
be taken to remove the bark from the stumps whenever they are
found to be infested with this pest.

THE ENGELMANN SPRUCE BEETLE.

The Engelmann spruce beetle attacks the Engelmann spruce, blue
spruce, and any other species of spruce found within its range, but

INSECT DAMAGE IN THE NATIONAL PARKS. 7

does not attack the pine, Douglas fir, or balsam fir. It flies in the
period from June to August and attacks the bark of the main trunks
of the older or matured trees. Its habits are similar to those of the
mountain pine beetle, except that it flies earlier in the spring. When
ihe trees begin to die the needles fade to a pale green and fall before
they change to yellow or brown, but the bare twigs present a grayish-
brown appearance. The infested trees are easily located in the fall
and early spring by the fallen needles and the bare twigs of the tops.

This species occurs from British Columbia to Mexico and at
times is very destructive to the Engelmann spruce forests. It can
be controlled by felling the infested trees and removing the bark
from the main trunks during the period beginning with the Ist of
October and ending by the middle to last of May.

THE BLACK HILLS BEETLE.

The Black Hills beetle is by far the most destructive insect enemy
of the pine of the central and southern Rocky Mountains and the
Black Hills of South Dakota. Its habits are similar to those of the
mountain pine beetle, and the same methods are adopted for its.
control.

FAVORABLE CONDITIONS FOR THE BEETLES.

There are certain conditions in the administered as well as in the
natural forests which contribute to the multiplication and destructive
work of these Dendroctonus beetles. One of the most favorable con-
ditions is an extensive forest of matured and old trees of pine or
spruce, because in the beginning of an invasion such trees are more
often the first to be attacked and killed. Trees in such a forest
injured by lightning or storms often form centers of infestation in
which the beetles increase to sufficient numbers to enable them to
kill a few trees, and then the invasion is started, year after year
increasing in force until a large percentage or all of the old timber is
killed. The beetles then attack the young trees and often waste their
energies on saplings, in which the broods fail to develop.

Drought.—\t is a common belief that severe droughts weaken the
trees and thus contribute to favorable conditions for the attack of the
beetles. We have made a very thorough investigation of this sub-
ject and are led to conclude that exceptionally dry seasons are more
unfavorable for the development of the beetles than are moderately
humid ones, and that, therefore, droughts do not contribute to their
multiplication.

Forest fires —F¥orest fires contribute, to a limited extent, to the
multiplication of certain species which breed in fire-scorched trees,
but as a rule forest fires kill more beetles than they protect.

8 INSECT DAMAGE IN THE NATIONAL PARKS.

Commercial cutting—Commercial cutting of timber may contrib-
ute to the multiplication of certain species which breed in the stumps
and tops, but if the cutting is continuous the insects confine their
attack to the cut-over areas and do not invade the living timber.
Sporadic summer cutting, however, is dangerous. The odor of the
cut wood attracts the flying beetles to the locality. This contributes
to their concentration, and when the cutting is stopped they invade
the living timber.

Secondary enemies——The secondary enemies of the trees consist of
numerous species which attack the bark and wood as soon as the
trees become weakened and are dying from other causes. The Den-
droctonus beetles are the primary enemies or leaders in the attack.
The secondary enemies are, to a certain extent, their allies, and
when very abundant may contribute to favorable conditions for
rapid advance in the destructive movement, but more often they
are dependents and scavengers, merely utilizing the dead and waste
material. With rare exceptions these secondary enemies are not
capable of killing trees on their own account.

UNFAVORABLE CONDITIONS FOR THE BEETLES.

The unfavorable conditions for the destructive work of these
Dendroctonus beetles are to be found in administered forests where
the ripe or matured timber is utilized and where the young timber
is protected by the prompt disposal, during the fall, winter, and
spring months, of any clumps of dying trees.

In other words, systematic forest management based on a knowl-
edge of the principles of silviculture and forest entomology will
soon present conditions so unfavorable for the Dendroctonus beetles
that, they can no longer exist as agents of destruction and waste.

The natural enemies of the beetles serve as a repelling force against
the progressive development of an invasion. Indeed, they are among
the principal factors which have prevented the extermination of
certain of the more important forest-tree species. These natural
enemies consist of parasites and predatory insects, which feed on
all stages of the barkbeetles, and birds, which feed on the adults
and young of the barkbeetles. Were it not for the fact that birds
also feed on the predatory and parasitic insect enemies of the bark-
beetles, and that such birds are limited in numbers, they might render
the great service that is so commonly credited to them.

Insect diseases in the form of epidemics sometimes serve to bring
an invasion under complete control, and unfavorable climatic con-
ditions have been known to exterminate a species of Dendroctonus
beetles within an area of thousands of square miles.

Therefore, although under natural conditions successive genera-
tions of the older trees are killed by their insect enemies, these in

INSECT DAMAGE IN THE NATIONAL PARKS. 9

turn are checked or repelled by natural means, so that generations
of younger trees take the place of their ancestors, and the forest as
such is perpetuated.

Natural control the most expensive.—In the national parks, na-
tional forests, and private forests where the resources have a commer-
cial value this natural control of the insect depredators on the
timber is the most expensive and wasteful. Our friends, the enemies
of the beetles, can not be depended upon to operate for the best
interests of the Federal or private owner. They can, however, be
made to render efficient service as the allies of the owner in an aggres-
sive warfare by him against the invaders. In this capacity they are
indispensable in the defense against renewed attacks and in the main-
tenance of conditions which will insure the future protection of the
living timber.

GENERAL METHODS OF CONTROL.

It is through a knowledge of the habits and seasonal history of the
various species of depredating insects, and the various complex fac-
tors operating for and against them, that forest entomologists are
enabled to advise methods of procedure in practical control opera-
tions either to reduce or eliminate the favorable conditions for the
multiplication of the beetles or to promote and utilize the factors
that are unfavorable for their existence.

It is also through a knowledge of the characteristic evidences of
their presence in the living and dying trees that we are enabled to
give instructions to an experienced timber-cruiser, forest ranger, or
fire patrolman which will enable him readily to detect an infestation
and report upon its character and extent.

Experiments with and demonstrations of methods of control have
furnished up-to-date information on the essential requirements in
conducting active control operations, which enables us to advise the
most economical and effectual method to be adopted for each species
of beetle, each species of tree, and each locality where an infestation
prevails.

Therefore, if the symptoms are accurately described and informa-
tion is furnished as to the local facilities for utilizing the infested
timber or for treatment at direct expense, specific recommendations
for successful control can be made without an examination by an
expert.

The presence in any national park of quantities of dying pine,
spruce, or Douglas fir that has not been caused by recent fires is
evidence of the presence and destructive work of one or more species
of the Dendroctonus beetles. An examination of the bark of the
main trunks of some of the dying trees will usually furnish conclusive
evidence, for if the trees are infested the characteristic work in the

10 INSECT DAMAGE IN THE NATIONAL PARKS.

park, as illustrated in the bulletins of the Bureau of Entomology, will
be easily recognized.

The next thing to do is to determine the extent of the infestation,
the kind of trees involved, and the facilities for disposing of the
timber by sale, free use, or direct expense. Then the superintendent
should report the facts to an expert and ask for advice and recom-
mendations. If he will then proceed without delay to dispose of the
infestation according to instructions given him, success in checking
or completely controlling the pest is almost certain to follow.

If, upon locating an infested area, it is found to extend beyond the
park boundary into adjacent privately owned timber or the national
forests, cooperation or at least concerted action is required, because
an important center of infestation is a menace to the living timber
within a radius of 10 to 20 miles.

If the timber of a national park is healthy and centers of infesta-
tion are found in adjacent forests within a radius of 10 to 20 miles,
the park superintendent should notify the owners. If, for any
reason, the owners can not dispose of the infestation the park officials
should help do it just as they would help im fighting a fire that
was threatening the park. In like manner the Federal and private
owners of healthy timber adjacent to a park should help dispose of
any extensive infestation in the park, because it may be more of a
common menace than a forest fire.

If this policy of cooperation for the general good is adopted and
the essential requirements for successful control are strictly adhered to
for a few years by the officials of the national parks, the national
forests, and the principal private owners, the damage to living
timber in the parks and on adjacent lands will be reduced to a mini-
mum, and ultimately thousands of dollars in commercial and esthetic
values will be saved for every dollar of public or private money
expended.

HIS PUBLICATION may be pro-
cured from the Superintendent of
Documents, Government Printing Office
Washington, D. C., at 5 cents per copy

Price furnished on application for lots of 100 or more

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