. s. r / i Circular No. 159. !«-it-i United States Department of Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. DA1AGE TO THE WOOD OF FIRE-KILLED DOUGLAS FIB, ami METHODS OF PREVENTING LOSSES, IN WESTERN \\ A8HINGTON \M> OREGON. Bj i D Hopkins, In (hurt!- of Forest Insect Investigations. Inquiries, with specimens, relating to extensive damage to fire- killed Douglas Br in western Washington showed i!i<' importance of making available to our correspondents some information based the results of forest insed investigations Douglas-fir timber killed by fire is attacked by a class <>f wood- boring insects which extend their burrows through the sound sap- and heartwood and thus contribute to the rapid deterioration and decay of i kind of resource which otherwise would be available for utilization during the period- of from 1 to 20 years or more after death of the trees, depending on the tree- and character of product desired. This loss often amounts to from 25 to LOO per cent during the period in which the dead timber would otherwise be almost as valuable as Living timber. Whenever the dying ami dead timber is available for utilization within one to -i\ or more years, much, and sometimes practically all, of the loss due to wood-boring insects i* preventable. One class <>f wood-borers attacks the timber during the spring, Bummer, and fall months within the first week or two after the tire or after the tree- begin to die. hut rarely continue- to work m the wood for more than one year, and all of some forms of the damage, ially to the sapwood, i- caused within •">" to 60 day-, while other forms continue during the warm season <>f the first <•!• second year. depending en the date of the tire and the species of insect involved. Most of the damage is usually confined to the sapwood, hut some of it may extend into the heartwood. 1 Revised elrcuUr letter of .Tune 16 -it to Interested timber land owners. It Is here published to supplement I - tin 112 OB 1 .1 Doaglaj Fir. and r.ureau of Bntomology areolar 127, Insert Injuries to the Wood of Dying and Dead l 50687'— Clr. 1 ." — 1 2 2 DAMAGE TO WOOD OF FIRE-KILLED DOUGLAS FIR. Another class of wood-boring insect.-, represented by a number of species, attacks the trees three or four year- 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. REQUISITES FOR SUCCESS IX 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. l>\\i UJE 1 1. w OOD 01 I 11:1 KI1 i ED D01 01 \ I lit. .5 (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 m time before thej enter the \n < m •. I . Soi pecies do uot go beyond the sapwood, while others bore deep into the heartwood. (8) Certain stages and classes of bark-boring grubs hatching from deposited in the hark attack the dying and dead trees, but never enter the \\ ood. ili Certain species and classes <>l' wood-boring grubs attack the aapwood of trees dead one to (luce years :i 1 1> 1 confine their borings to the sap* ood. Certain species and classes of wood-boring grubs and other insects enter the wood of i rees dead three to twentj years or more and bore deep into the heart w I. ["IONS GOVERNING II i I WORK OF I \-l.< rS 01 rHE DIFFERENT CI \--i - i A) In classes 1 to I. inclusive, the presence of hark on the trunks of the tree- i-. 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 hark i- removed, although the wood must be in a moist condition. The hark-, however, oiler- far more favorable con- ditions for the work of this class of insects because it provide.- for a continued moist condition of the wood I '. | In class 5 the hark is not essential. Although offering favor- able condition- for the attack of some species of insects, it i- not necessary for the attack of others, especially after the sapwood begins to decay. GENES W. Ml TH0D8 OF < ONTROI* l] I ion A. To avoid damage from wood-boring insects which are dependent upon condition A. one or more of the following general methods should he adopted, SO far a- the local facilities and cost w ill permit : (a) Prompt utilization of the timber within 30 to 60 day- after it is killed by lire any time from the beginning of the growth of vegetation in the spring until it stops in the fall, which will vary with latitude ami altitude. Timber killed after the first snow or heavy fro-t should he utilized within 30 day- after plant activity -tarts in the following spring if deterioration is to be prevented. (b) Prompt removal of the hark- from the merchantable timber under the same requirements a- to periods mentioned under I Placing the unbarked h>