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CIRCULAR No. 159. Issued July 27, 1912.
United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

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

DAMAGE TO THE WOOD OF FIRE-KILLED DOUGLAS FIR,
AND METHODS OF PREVENTING LOSSES, IN WESTERN
WASHINGTON AND OREGON.

By AY D. Hopkins,
In Charge of Forest Insect Investigations.

Inquiries, with specimens, relating to extensive damage to fire-
killed Douglas fir in western Washington showed the importance
of making available to our correspondents some information based
on the results of forest insect investigations.

Douglas-fir timber killed by fire is attacked by a class of wood-
boring insects which extend their burrows through the sound sap-
wood and heartwood and thus contribute to the rapid deterioration
and decay of a kind of resource which otherwise would be available
for utilization during the periods of from 1 to 20 years or more after
death of the trees, depending on the trees and character of product
desired. This loss often amounts to from 25 to 100 per cent during
the period in which the dead timber would otherwise be almost as
valuable as living timber.

Whenever the dying and dead timber is available for utilization
within one to six or more years, much, and sometimes practically all,
of the loss due to wood-boring insects is preventable.

One class of wood-borers attacks the timber during the spring,
summer, and fall months within the first week or two after the fire
or after.the trees begin to die, but rarely continues to work in the
wood for more than one year, and all of some forms of the damage,
especially to the sapwood, is caused within 30 to 60 days, while other
forms continue during the warm season of the first or second year,
depending on the date of the fire and the species of insect involved.
Most of the damage is usually confined to the sapwood, but some of
it may extend into the heartwood.

1 Revised circular letter of June 16, 1909, sent to interested timber-land owners. It is

here published to supplement Forest Service Bulletin 112 on Fire-Killed Douglas Fir,
and Bureau of Entomology Circular 127, Insect Injuries to the Wood of Dying and
——

Dead Trees.
“22168

50687°—Cir. 159—12

2 DAMAGE TO WOOD OF FIRE-KILLED DOUGLAS FIR.

Another class of wood-boring insects, represented by a number of
species, attacks the trees three or four years after they die; these bore
deep into the heartwood, thus causing serious damage. Insects of
this class will continue to attack the trees year after year as long as
they find sound wood in which to excavate their burrows. There-
fore the damage increases year by year until the wood is rendered
entirely worthless by the borings and by the subsequent decay which
necessarily follows.

It is a fact, however, that there is often a great difference in the
relative damage to individual trees which have died from injuries
caused by the same fire. Some trees will be ruined in a few years,
while others will be but slightly damaged and remain sound for 10,
20, or even, in exceptional cases, 50 years.

The date or period of the fire or fires is an important factor in rela-
tion to subsequent injury by insects. It is well known that timber
killed by fire at some seasons of the year will remain sound much
longer than that killed at other seasons.

The character of the primary injury and the date or season of the
subsequent death of the individual trees is also important. Some of
the trees will die immediately after the fire, while others will die at
intervals for a year or more. Those dying at different times and
seasons will show very different conditions as to subsequent damage
by wood-boring insects. Then, again, different ages and types of
trees of the same species will show very different rates of damage, as
will also different species of trees,

It is somewhat different in the case of timber killed by bark-
beetles or defoliating insects, because in such cases the timber usually
dies within definite periods and is therefore subject to attack by
special kinds of wood-boring insects.

REQUISIFES FOR SUCCESS IN PREVENTING LOSSES.

In regard to methods of preventing losses from damage by wood-
boring insects to fire-killed timber there are a few fundamental
requisites for success which should be carefully considered before
action is taken, Among these are the recognition of the different
classes of injury and of the importance of expert advice on some
of the essential details in any plans for extensive operations to pre-
vent losses.

CLASSES OF INSECTS AND INJURY.

Some of the important classes of insects and injury are as follows:

(1) Certain pinhole borers (ambrosia beetles) attack the sapwood
as soon as the trees begin to die, but the damage by this class of
borers is usually limited to the first season.

DAMAGE TO WOOD OF FIRE-KILLED DOUGLAS FIR. 3

(2) Certain species and classes of bark and wood boring grubs
hatch from eggs deposited in the bark of the trees and burrow under
the bark for a time before they enter the wood. Some species do not
go beyond the sapwood, while others bore deep into the heartwood.

(3) Certain stages and classes of bark-boring grubs hatching from
eggs deposited in the bark attack the dying and dead trees, but never
enter the wood.

(4) Certain species and classes of wood-boring grubs attack the
sapwood of trees dead one to three years and confine their borings
to the sapwood.

(5) Certain species and classes of wood-boring grubs and other
insects enter the wood of trees dead three to twenty years or more and
bore deep into the heartwood.

CONDITIONS GOVERNING THE WORK OF INSECTS OF THE DIFFERENT CLASSES,

(A) In classes 1 to 4, inclusive, the presence of bark on the trunks
of the trees is, with a few exceptions, necessary as a receptacle for
the eggs and as the first food of the young grubs. The exceptions are
the pinhole borers or ambrosia beetles, which will sometimes attack
the wood when the bark is removed, although the wood must be in a
moist condition. The bark, however, offers far more favorable con-
ditions for the work of this class of insects because it provides for a
continued moist condition of the wood.

(B) In class 5 the bark is not essential. Although offering favor-
able conditions for the attack of some species of insects, it is not
necessary for the attack of others, especially after the sapwood begins
to decay.

GENERAL METHODS OF CONTROL.
ConpDITION A.

To avoid damage from wood-boring insects which are dependent
upon condition A, one or more of the following general methods
should be adopted, so far as the local facilities and cost will permit:

(a) Prompt utilization of the timber within 30 to 60 days after
it is killed by fire any time from the beginning of the growth of
vegetation in the spring until it stops in the fall, which will vary
with latitude and altitude. Timber killed after the first snow or
heavy frost should be utilized within 30 days after plant activity
starts in the following spring if deterioration is to be prevented.

(6) Prompt removal of the bark from the merchantable timber
under the same requirements as to periods mentioned under (a).

(ce) Placing the unbarked logs in water under the same require-
ments as to periods mentioned under (a).

4 DAMAGE TO WOOD OF FIRE-KILLED DOUGLAS FIR.

In addition to the general requirements of the principal methcds
(a, 6, and c), each of classes 1, 2, 3, and 4, and each of the many
species of each class require some different or specific detail in the
method to insure the best success. Therefore when it is desired to
avoid a special class of injury expert advice should be secured.

CoNDITION B.

Under condition B the opportunities are much less favorable fdr
the prevention of further losses. After the timber has been dead
three to twenty years or more, one or more of the following methods
should be considered and adopted whenever practicable.

MERCHANTABLE TIMBER DEAD THREE TO FIVE YEARS.

(7) Timber dead three to five years should be cut and converted
into lumber with as little delay as possible, or i

(e) Cut into logs and placed in water, to remain there until it
can be converted into lumber or other products.

MERCHANTABLE TIMBER DEAD SIX TO TEN YEARS OR LONGER.

(7) Thoroughly inspect individual trees to locate and mark those
that are yet available for utilization, and make estimates on which
to base conclusions as to whether or not it can be profitably logged
for direct utilization or storage in water.

Approved:

JAMES WILSON,
Sener awoaore A
Des

W ASHINGTON 16, 1912.

INSTITUTION L

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