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C576
ENT No. 82. Issued January 2, 1907.

ited States Department of Agriculture,

BUREAU OF ENTOMOLOGY,
L. O. HOWARD, Entomologist and Chief of Bureau.

PINHOLE INJURY TO GIRDLED CYPRESS IN THE SOUTH ATLANTIC
AND GULF STATES.

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

Pursuant to certain complaints of serious injury by wood-boring
insects to girdled cypress timber in the South Atlantic and Gulf States,
the Bureau of Entomology began a series of experiments and investiga-
tions with special trees girdled on definite dates in every month of the
year, as well as with those girdled in regular operations at known dates
or periods, to determine whether or not there was any important rela-
tion between the month or time of year the trees were girdled and sub-
sequent injuries.

This work was personally conducted by specialists of the Bureau in
cooperation with cypress manufacturers in southeastern North Carolina,
southern South Carolina, southeastern Georgia, western Florida, and
southern Louisiana. It was begun in the spring of 1903 and continued
until December, 1904. Over 300 trees were examined, and observations
were made on practically all of the different species of insects which are
in any manner associated with injury to the wood and bark of living,
dying, and felled, as well as girdled, cypress.

RESULTS OF INVESTIGATIONS.

The principal injury to the wood of standing girdled cypress was
found to consist of pinholes in the sapwood and heartwood caused by
two classes of small wood-boring beetles, called timber beetles, ambrosia
beetles, pin borers, “pin worms,’’ etc. They bore the so-called pin-
holes in the wood as places to deposit eggs and rear their broods, and
the latter, when fully developed, leave the wood and fly to other trees
to repeat the process.

One of these classes of wood-boring beetles is represented by small,
short, cylindrical, reddish beetles one-eighth to one-tenth of an inch in
length, which are exclusively sapwood borers. As a rule they are not
common in girdled trees, but are abundant in logs from living trees.

The other class is represented by elongate, slender, reddish, cylin-
drical beetles three-eighths of an inch in length, which often extend:
their borings deep into the heartwood and are often common and quite

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injurious to both girdled and felled trees. One species of this latter class
causes more damage, perhaps, than all of the many other insects which
have been found boring in the wood of girdled trees. It is known tech-
nically as Platypus compositus Say, and may be distinguished from
other cypress pin-borers by the English name “ girdled-cypress pin-
borer,’’ or Pan American Platypus. (See fig. 1.)

The facts and evidence of immediate practical importance may be
briefly stated as follows: Trees girdled in March, April, October, and
November were not at all or but slightly damaged by the girdled-cypress
pin-borer, while those girdled in May, June, July, and September were
more or less seriously damaged. There were indications that trees
girdled in August were not damaged as badly as those girdled in July

Fria. 1.—Work of ambrosia beetles in oak: a, Monarthrum mali and work; b, Platypus compositus
and work; ¢c, bark; d, sapwood; e, heartwood; f, character of work in lumber from injured
log. (Author’s illustration.)

and September; also, that trees girdled from December to February
were not seriously affected. It was found that local factors and con-
ditions had an important bearing on whether or not injury resulted from
girdling at given dates. In some localities there was practically no
injury to trees girdled on any of the dates. In other localities some of
the trees girdled on a given date would be badly damaged while others
would show no trace of injuries. The absence of injuries in the former
localities may have been due to the presence of a limited number of the
insects, or to their being attracted to felled trees in preference to the
standing girdled ones, or to some other unknown causes. The attack
on individual trees is evidently due to individual differences in the trees
themselves, for our general observations indicate quite clearly that
certain types and varieties of trees of the same species are more resistant

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or immune to their insect enemies while others are more attractive
to them. It is well known that there is a marked difference in the
individual characteristics of cypress trees in any given locality, and
especially so in different localities, and that there is also marked differ-
ence among a large number of trees girdled on the same day or time of
year in the results obtained. Some will die quickly and dry out rapidly;
some will remain alive a much longer time, the wood remaining moist
and becoming discolored; some will yield beautifully grained lumber
of the highest grade; while others, equally as sound, will yield tough,
cross-grained, dull lumber of a low grade. These conditions are not
due entirely to the character of the work of girdling, nor to accident,
local influences of soil, ete., but largely to variations which produce
more or less distinct, good and poor natural varieties. Therefore cer-
tain trees or varieties which prove to be especially attractive to the pin-
borer, no matter when they are girdled, may be attacked and more or
less injured.

The girdled-cypress pin-borer must have moist wood in which to
excavate its burrows and develop its broods of young and will not
attack the trees after they have been dead long enough for the wood to
become dry. It evidently prefers to attack the wood of felled gum and
cypress. Our observations indicate that living trees felled in April and
August offer specially attractive conditions for infestation by this species,
and that it will often begin to enter the wood within a few days after
the trees are felled. This suggests the utilization of felled trees as traps
to attract it away from the girdled ones and at the same time facilitate
the destruction of the broods by placing the logs of the trap trees in
water after they have become thoroughly infested and before the broods
of adults begin to emerge and fly.

To accomplish this the trap trees felled in April must be burned or
placed in water during the following June and those felled in August
treated in the same manner in October.

RECOMMENDATIONS.

General recommendations for the prevention of insect injury to girdled
cypress may be briefly stated as follows:

First.—Conduct the principal girdling operations in March, April,
October, and November, or either in the former or latter months as may
seem best from the local conditions and relative value of the product in
each locality. October-girdled trees should be felled and floated or
worked up within one year to avoid injury by another class of wood
borers which attack trees after they have been dead one or more years.

Second.—In localities where it is known that the insect is abundant
and injurious, felled trap trees may be provided in March and April,
and July and August, say, one otherwise worthless gum or cypress trap
tree for each fifty to seventy trees to be girdled in the same locality.

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Third.—lIf it is desirable to girdle trees at other times during the
summer and to utilize trap trees, these latter should be provided a week
or more ahead of the girdling, and located on the banks of streams,
ponds, or pools, where, at the proper time, they can be readily rolled
into the water.

Fourth.—Trap trees should never be provided unless it is quite cer-
tain that they will be placed in the water or otherwise destroyed within
two or three months after they are felled and infested by the insects,
otherwise they may contribute to a greater multiplication of the insects
and increased danger of serious injury to the girdled trees.

The adoption and carrying out of these recommendations should be
governed in each locality by the personal observations and experience
of the operators, based on a study of the conditions resulting from trees
girdled at different positively known dates or times of year, and also on
a study of the evidences of infestation by the pin-borer in the girdled
trees and in the logs, stumps, slash, etc., of cypress, gum, and other
trees. These evidences of infestation consist of the greater or less quan-
tities of fine, whitish boring-dust on the bark and around the base of the
trees and stumps, under the logs, etc., the work of the girdled-cypress
pin-borer and its class being distinguished from that of the sapwood
borers by the prevalence of short cylindrical sections of adhering dust
expelled from the holes.

For more detailed information on the habits of wood-boring insects
and the character of injuries caused by them in standing and felled
trees, lumber, etc., the reader is referred to the Yearbook of the United
States Department of Agriculture for 1904, pages 381 to 398.

Approved :
JAMES WILSON,
Secretary of Agriculture.

WASHINGTON, D. C., December 19, 1906.

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