INSECT ENEMIES OF EASTERN FORESTS 43 
Many different kinds of wood-preservative chemicals can be used, 
but the most satisfactory of those tested are chromated zine chloride, 
zine chloride, and copper sulfate, used at concentrations of 14 to 34 
pound per cubic foot of sapwood to be treated. For details of this 
method of treating green timber see Craighead and St. George (19). 
Chemical Sprays 
Although prevention of insect attack is far more desirable than 
treatment later, material already infested can be treated with any of 
several chemicals to kill the insects and thus prevent complete 
loosening of the bark or annoyance caused by rasping noises and the 
exudation of sawdust. Effective chemical sprays are (1) 5 percent of 
pentachlorophenol in fuel oil, and (2) crude orthodichlorobenzene. 
The latter can be apphed full strength or diluted up to 5 parts of 
fuel oil, and the bark or wood should be saturated with the chemical. 
Liberal applications are recommended. One gallon of the chemical 
should be sufficient to treat 5 logs, 10 feet long, and 5 inches in 
diameter, or approximately 65 square feet of bark surface. These 
chemicals may be obtained from a number of large manufacturing 
concerns, and they are frequently stocked by chemical supply houses. 
Care should be taken in handling these sprays as they are 
extremely irritating to the eyes. 
Frequently rustic cabins are constructed of peeled logs. This pro- 
cedure, of course, prevents practically all insect attack, the most objec- 
tionable feature of which is the checking of the wood. 
PROTECTING WOOD IN CONTACT WITH THE GROUND 
All kinds of wood in contact with the ground, as poles, posts, mine 
props, and cross ties are subject to attack by termites, carpenter ants, 
and wood-boring beetles. The use of a good wood preservative will 
greatly increase the life of most woods; and nondurable woods, if 
properly treated, can be made to last as long as the most durable species. 
Coal-tar creosote applied by an approved, standard pressure process 1s 
the most satisfactory all-round preservative. Methods of using creo- 
sote were described by Hunt (248) and by Hunt and Garratt (249). 
Other wood preservatives are 5 percent of pentachlorophenol and 
copper naphthenate having a 2-percent metallic content. These are 
sold on the market under various trade names. Wood preservatives 
are of value only in proportion to the amount of effective ingredients 
they contain. Both chromated zinc chloride and zinc chloride are 
useful preservatives where the wood is not subject to much dampness 
or leaching, or where it can be protected by an adequate covering of 
paint or varnish. 
Materials in use, as poles or posts of considerable importance, can 
be made to last longer, even after they have been infested by wood 
borers, carpenter ants, or termites, by poisoning the soil about them 
with such chemicals as orthodichlorobenzene, a mixture composed of 
1 part of coal-tar creosote (grade 1 oil) to 2 parts of a light petroleum 
oil or kerosene, or a 5-percent solution of pentachlorophenol. A 
5-gallon treatment will protect a pole 15 inches in diameter for about 
5 years. In heavy soils the necessary procedure consists of digging a 
trench to a depth of 30 inches, if the pole is set deeply, and then 
wetting the soil evenly with the preservative as it is being replaced. 
