Part 11 (1/2)

The sapwood of pine, spruce, fir, cedar, cypress, and the like softwoods is especially liable to injury by ambrosia beetles, while the heartwood is sometimes ruined by a cla.s.s of round-headed borers, known as ”sawyers.” Yellow poplar, oak, chestnut, gum, hickory, and most other hardwoods are as a rule attacked by species of ambrosia beetles, sawyers, and timber worms, different from those infesting the pines, there being but very few species which attack both.

Mahogany and other rare and valuable woods imported from the tropics to this country in the form of round logs, with or without bark on, are commonly damaged more or less seriously by ambrosia beetles and timber worms.

It would appear from the writer's investigations of logs received at the mills in this country, that the princ.i.p.al damage is done during a limited period--from the time the trees are felled until they are placed in fresh or salt water for transportation to the s.h.i.+pping points. If, however, the logs are loaded on a vessel direct from the sh.o.r.e, or if not left in the water long enough to kill the insects, the latter will continue their destructive work during transportation to other countries and after they arrive, and until cold weather ensues or the logs are converted into lumber.

It was also found that a thorough soaking in sea-water, while it usually killed the insects at the time, did not prevent subsequent attacks by both foreign and native ambrosia beetles; also, that the removal of the bark from such logs previous to immersion did not render them entirely immune. Those with the bark off were attacked more than those with it on, owing to a greater amount of saline moisture retained by the bark.

How to Prevent Injury

From the foregoing it will be seen that some requisites for preventing these insect injuries to round timber are:

1. To provide for as little delay as possible between the felling of the tree and its manufacture into rough products.

This is especially necessary with trees felled from April to September, in the region north of the Gulf States, and from March to November in the latter, while the late fall and winter cutting should all be worked up by March or April.

2. If the round timber must be left in the woods or on the skidways during the danger period, every precaution should be taken to facilitate rapid drying of the inner bark, by keeping the logs off the ground in the sun, or in loose piles; or else the opposite extreme should be adopted and the logs kept in water.

3. The immediate removal of all the bark from poles, posts, and other material which will not be seriously damaged by checking or season checks.

4. To determine and utilize the proper months or seasons to girdle or fell different kinds of trees: Bald cypress in the swamps of the South are ”girdled” in order that they may die, and in a few weeks or months dry out and become light enough to float. This method has been extensively adopted in sections where it is the only practicable one by which the timber can be transported to the sawmills. It is found, however, that some of these ”girdled” trees are especially attractive to several species of ambrosia beetles (Figs. 22 and 23), round-headed borers (Fig. 24) and timber worms (Fig. 25), which cause serious injury to the sapwood or heartwood, while other trees ”girdled” at a different time or season are not injured. This suggested to the writer the importance of experiments to determine the proper time to ”girdle” trees to avoid losses, and they are now being conducted on an extensive scale by the United States Forest Service, in co-operation with prominent cypress operators in different sections of the cypress-growing region.

Saplings

Saplings, including hickory and other round hoop-poles and similiar products, are subject to serious injuries and destruction by round- and flat-headed borers (Fig. 24), and certain species of powder post borers (Figs. 26 and 27) before the bark and wood are dead or dry, and also by other powder post borers (Fig. 28) after they are dried and seasoned. The conditions favoring attack by the former cla.s.s are those resulting from leaving the poles in piles or bundles in or near the forest for a few weeks during the season of insect activity, and by the latter from leaving them stored in one place for several months.

Stave, Heading and s.h.i.+ngle Bolts

These are attacked by ambrosia beetles (Figs. 22 and 23), and the oak timber worm (Fig. 25, _a_), which, as has been frequently reported, cause serious losses. The conditions favoring attack by these insects are similiar to those mentioned under ”Round Timber.” The insects may enter the wood before the bolts are cut from the log or afterward, especially if the bolts are left in moist, shady places in the woods, in close piles during the danger period. If cut during the warm season, the bark should be removed and the bolts converted into the smallest practicable size and piled in such manner as to facilitate rapid drying.

Unseasoned Products in the Rough

Freshly sawn hardwood, placed in close piles during warm, damp weather in July and September, presents especially favorable conditions for injury by ambrosia beetles (Figs. 22, _a_, and 23, _a_). This is due to the continued moist condition of such material.

Heavy two-inch or three-inch stuff is also liable to attack even in loose piles with lumber or cross sticks. An example of the latter was found in a valuable lot of mahogany lumber of first grade, the value of which was reduced two thirds by injury from a native ambrosia beetle. Numerous complaints have been received from different sections of the country of this cla.s.s of injury to oak, poplar, gum, and other hardwoods. In all cases it is the moist condition and r.e.t.a.r.ded drying of the lumber which induces attack; therefore, any method which will provide for the rapid drying of the wood before or after piling will tend to prevent losses.

It is important that heavy lumber should, as far as possible, be cut in the winter months and piled so that it will be well dried out before the middle of March. Square timber, stave and heading bolts, with the bark on, often suffer from injuries by flat- or round-headed borers, hatching from eggs deposited in the bark of the logs before they are sawed and piled. One example of serious damage and loss was reported in which white pine staves for paint buckets and other small wooden vessels, which had been sawed from small logs, and the bark left on the edges, were attacked by a round-headed borer, the adults having deposited their eggs in the bark after the stock was sawn and piled. The character of the injury is shown in Fig. 29. Another example was reported from a manufacturer in the South, where the pieces of lumber which had strips of bark on one side were seriously damaged by the same kind of borer, the eggs having been deposited in the logs before sawing or in the bark after the lumber was piled. If the eggs are deposited in the logs, and the borers have entered the inner bark or the wood before sawing, they may continue their work regardless of methods of piling, but if such lumber is cut from new logs and placed in the pile while green, with the bark surface up, it will be much less liable to attack than if piled with the bark edges down. This liability of lumber with bark edges or sides to be attacked by insects suggests the importance of the removal of the bark, to prevent damage, or, if this is not practicable, the lumber with the bark on the sides should be piled in open, loose piles with the bark up, while that with the bark on the edges should be placed on the outer edges of the piles, exposed to the light and air.

[Ill.u.s.tration: Fig. 29. Work of Round-headed Borers, _Callidium antennatum_, in White Pine Bucket Staves from New Hamps.h.i.+re. _a_, where egg was deposited in bark; _b_, larval mine; _c_, pupal cell; _d_, exit in bark; _e_, adult.]

In the Southern States it is difficult to keep green timber in the woods or in piles for any length of time, because of the rapidity which wood-destroying fungi attack it. This is particularly true during the summer season, when the humidity is greatest. There is really no easily-applied, general specific for these summer troubles in the handling of wood, but there are some suggestions that are worth while that it may be well to mention. One of these, and the most important, is to remove all the bark from the timber that has been cut, just as soon as possible after felling. And, in this, emphasis should be laid on the ALL, as a piece of bark no larger than a man's little finger will furnish an entering place for insects, and once they get in, it is a difficult matter to get rid of them, for they seldom stop boring until they ruin the stick. And again, after the timber has been felled and the bark removed, it is well to get it to the mill pond or cut up into merchantable sizes and on to the pile as soon as possible. What is wanted is to get the timber up off the ground, to a place where it can get plenty of air, to enable the sap to dry up before it sours; and, besides, large units of wood are more likely to crack open on the ends from the heat than they would if cut up into the smaller units for merchandizing.

A moist condition of lumber and square timber, such as results from close or solid piles, with the bottom layers on the ground or on foundations of old decaying logs or near decaying stumps and logs, offers especially favorable conditions for the attack of white ants.

Seasoned Products in the Rough