Circular

SB
818

C3578

ENT

Issued March 7, 1911.

U. S2 DEPARTMENT, OF AGKICUL TURE,

BUREAU OF ENTOMOLOGY—CIRCULAR No. 134.
L. O. HOWARD, Entomologist and Chief of Bureau.

DAMAGE TO TELEPHONE AND TELEGRAPH
POLES BY WOOD-BORING INSECTS.

BY

T. E. SNYDER,
Agent and Expert.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1911

216854

BUREAU OF ENTOMOLOGY.

L. O. Howarp, Entomologist and Chief of Bureau.
C. L. Maruarr, Entomologist and Acting Chief in Absence of Chief.
R. S. Curtron, Executive Assistant.
W. F. Taster, Chief Clerk.

F. H. CurrrenveEn, 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.

F. M. WesstTER, in charge of cereal and forage insect investigations.

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

E. F. Puiuies, in charge of bee culture.

D. M. RoceErs, in charge of preventing spread of moths, field work.
Rota P. Currie, in charge of editorial work.

MABEL CotcorD, librarian.

Forest Insect INVESTIGATIONS.
A. D. Hopkins, in charge.

H. E. Burke, J. L. Wess, Joser Brunner, S. A. Ronwer, T. E. Snyper, W. D.
Epmonsrton, W. B. TurNER, agents and experts.

Mary E. Faunce, preparator.

Witu1amM Mrppieton, Mary C. JoHNSON, s/udent assistants.

II

CIRCULAR No. 134. Issued March 7, 1911.
United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

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

DAMAGE TO TELEPHONE AND TELEGRAPH POLES BY
WOOD-BORING INSECTS.'

By T. E. SnypvEr,
Agent and Expert.

It has recently been determined through special investigations con-
ducted by the Bureau of Entomology, in cooperation with telephone
and telegraph companies, that serious and extensive damage is being
done in certain localities to standing poles by wood-boring insects.
The object of this circular is to give information on the principal as
well as other types of insect injury to poles, so that line inspectors
may distinguish the various types and determine and report on the
character and extent of the damage.

CHARACTER OF THE INJURY.

The principal injury to the poles consists in large mines in the wood
near the line of contact with the ground, necessitating the frequent
resetting or even the replacement of the damaged poles. These
irregular mines (fig. 1) run both transversely and longitudinally
throughout the heartwood, and are sometimes 7 inches long, but
vary in length. This injury is usually in the outer layers of the
wood for a distance of from 2 to 3 feet below and sometimes from 1
to 2 feet above the line of contact of the pole with the surface of the
ground. The greatest damage is to that area just below and just
above the surface of the ground; here the conditions of air and
moisture are most favorable. The mines, often very close together,
completely honeycomb the wood in a zone from 3 to 4 inches in from
the exterior of the poles (fig. 3); this so weakens the poles that they
break off close to the surface of the ground. The basal 2 feet is

1 Revised extracts from Bulletin 94, Part I, Bureau of Entomology, U. S. Department of Agriculture,
1910.

77538°—Cir. 134—11 |

INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES

2

Sl 9 pase SR cr

Gallery of the
fibers; work near

?

pole: a

untreated chestnut

k of the pole borer (Parandra brunnca Fab.) in an

1.—Wor
, Showing

Te

Fi

ood
Natural size.

Ww

ike

xcelsior-li

b, Mines of the pole borer near surface of

pupal chamber with the entrance plugged with e

round.

pole borer

(Author’s

round.

o
t=)

&

, below

base of pole
illustration.)

INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. 3

usually sound. Even if the damage is not serious enough to cause
the poles to break off under strain, they are likely to go down during
any storm, and thus put the wire service out of commission; such
damaged poles are a serious menace along the right of way of rail-
roads. Poles that appear sound on the exterior may have the
entire basal interior riddled, and the damage is not noticed until the
poles break off. If merely isolated poles are injured so as to cause
them to break off, they simply lean over, but if several adjacent poles
are affected, especially where there is any unusual strain, that por-
tion of the line is very likely to go down.

THE PRINCIPAL INJURIOUS SPECIES.

The principal injurious species is the chestnut telephone-pole
borer, or pole borer,! which is an elongate, creamy-white, wrinkled,

Fic. 2.—1, The pole borer: Male and female beetles. 2, The pole borer: Young
larvee. 1, Slightly enlarged; 2, twice natural size. (Author’s illustration.)

round-headed grub or larva (fig. 2,2). It hatches from an egg depos-
ited by an elongate, mahogany - brown, shiny, flattened, winged
beetle, from two-fifths to four-fifths of an inch in length (fig. 2, 7).
It appears that the eggs are deposited from August to October in
the outer layers of the wood of the pole near the surface of the
ground. The young borers, upon hatching, excavate shallow gal-
leries in the sapwood, then enter the heartwood, the mines being
gradually enlarged as they develop. As they proceed they closely
pack the fine boring dust behind them. This peculiar semidigested
boring dust, which is characteristic of their work, is reddish to dun-

1 Parandra brunnea Fab. Since the publication of Bulletin 94, Part I, of this Bureau, this borer, first
found to be injurious to chestnut telephone poles, has been found injurious to arborvitz poles, and as it
also injures telegraph poles, the name “ pole borer’’ is more appropriate and comprehensive.

4 INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES.

nish yellow in color and has a claylike consistency. The burrows
eventually end in a broad chamber, the entrance to which is plugged
with excelsiorlike fibers of wood. Here is formed the resting stage,
or pupa, which transforms to the adult beetle. Often all stages, from
very young grubs only about one-fourth inch long to full-grown
grubs over 1 inch long, pup, and adults in all stages to maturity
are present in the same pole. Adults have been found flying from
July to September.

The insect attacks poles that are perfectly sound, but will work
where the wood is decayed; it will not, however, work in wood that
is ‘‘sobby”’ (wet rot), or in very ‘‘doty”’ (punky) wood. It has not
yet been determined just how soon the borers enter the poles after
they have been set in the ground. However, peles that had been

Fia. 3—Damage to an untreated chestnut telegraph pole near surface of ground
by the pole borer. (Author’s illustration.)

standing only four or five years contained larve and adults oftaie
borer in the heartwood, and poles that had been set in the ground
for only two years contained young larve in the outer layers of the
wood.

The presence of the borers in injurious numbers can be deter-
mined only by removing the earth from about the base of the pole;
the large holes made when the adults come out are found near the
line of contact with the soil. Often large, coarse borings of wood
fiber project from these exit holes. Sometimes the old dead parent
adults are found on the exterior of the poles underground. During
August the young adults may be found in shallow depressions on the
exterior of poles below the ground surface.

INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES. 5

INJURY BY OTHER INSECTS.

It is not to be concluded that injury by the pole borer is the only
type of insect damage to poles. Indeed, a very common injury is by
white ants, or termites. In lines from 10 to 12 years old serious
damage by these insects occurred in as high as 15 per cent of the
poles, and their work is often present, at least superficially, in as
high as 75 per cent of the poles under all conditions of site. The
damage, however, is usually to the outer layers of the wood, where it
is moist or there is incipient decay, and is more superficial and local-
ized than that of the pole borer. Nevertheless, the sound heartwood
of poles is often completely honeycombed, especially at the base. The
work of white ants is found both in sound wood, ‘‘doty”’ wood, and
‘“sobby’’ wood. Sometimes a large channel runs up through the core
of the heart and the sides are plastered with clay, forming a hollow
tube with several longitudinal interior galleries. Their work often
extends from 2 to 4 feet above the surface of the ground. They
leave the outer shell of the wood intact and work up through the
longitudinal weathering checks, covering the exterior of the pole with
earth to exclude the light. White ants will damage poles that have
been set in the ground only two years. Evidently they enter the
pole from below the surface of the ground.

Injury by a giant round-headed borer is sometimes found in chest-
nut poles. The large mines of this borer are found in the sound
and decayed wood of poles. Often where there is rot present the
heartwood near the surface of the ground is completely honey-
combed by this borer.

Longitudinal weathering checks in chestnut poles are often widened,
and other defects enlarged by large, black carpenter ants and other
smaller black ants, which thus hasten decay.

KNOWN EXTENT OF THE DAMAGE.

The pole borer has seriously damaged as high as 10 to 15 per cent
of the chestnut poles which have been set in the ground for from 10
to 12 years in lines in North Carolina, Virginia, West Virginia, Mary-
land, and the District of Columbia. It has only recently been deter-
mined that it has also seriously damaged a considerable proportion
of the arborvite! telephone poles in part of a line in Illinois. It is
evident, then, that this insect is an important factor in decreasing the
normal length of service of chestnut and arborvitz poles.

POSSIBILITIES OF PREVENTING DAMAGE TO POLES.

Methods of treating poles superficially by brushing with various
preservatives have proved to be temporarily efficient in keeping
out wood-boring insects, if the work is thoroughly done and not

1 Thuja occidentalis.

6 INSECT DAMAGE TO TELEPHONE AND TELEGRAPH POLES.

only the butt, but also the basal area, is treated. If the pole is not
thoroughly brushed, the pole borer and other insects enter through the
untreated or imperfectly treated portions, especially through weath-
ering checks and knots. Where the base is left untreated, insects,
especially white ants or termites, enter the pole from below ground
and, avoiding the treated portions, come right up through the pole.

Impregnating the poles with creosote by some standard process
(either by the open-tank or by a cylinder-pressure process) will keep
out wood-boring insects. In the open-tank method only the area most
subject to the attacks of wood-boring insects (i. e., the basal 8 feet)
is treated, while by the cylinder-pressure processes the entire pole is
impregnated.

Therefore, to effectually protect poles from the depredations of
wood-boring insects it is recommended-that they be impregnated with
creosote by either the ‘‘open-tank’’ process or by a cylinder-pressure
process.

Approved:

JAMES WILSON,
Secretary of Agriculture.

WasuHinerTon, D. C., January 24, 1911.

O NIAN INSTITUTION LIBRARIES

ANNUM
3 90

88 01272 8044

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