2 BULLETIN 1231, U. S. DEPARTMENT OF AGRICULTURE. 



forest products could be found by American manufacturers in South 

 America and in other tropical countries, provided a satisfactory 

 " white-ant-proof " product could be furnished. After a preliminary 

 survey of the extent of the damage throughout the country, a series 

 of experiments were planned, which are outlined herein. 



The following pages are a progress report on the results of these 

 experiments conducted at Falls Church, Va., from 1912 to 1922, sup- 

 plemented by data obtained by inspections of treated timbers made 

 by the writer from 1909 to 1922, in service tests of telephone and 

 telegraph companies, in cooperation with the United States Forest 

 Service. 



DESCRIPTION OF EXPERIMENTS. 



On August 14, 1912, experiments were begun by the Forest Insect 

 Investigations of the Bureau of Entomology in testing wood pre- 

 servatives and insecticides to render wood or products of wood re- 

 sistant to attack by wood-boring insects, especially by termites. 

 Several objects were in view in these experiments. 



Tests of the relative effectiveness of preservatives for timber to 

 be set in or in contact with the ground were to be made. Preserva- 

 tives, to be practicable for such use, should not only be insecticides 

 but also disinfectants or fungicides. They should preferably be of 

 low solubility in water and low volatility so that their poisonous 

 effect will not be quickly destroyed by leaching (in wet situations) 

 or by evaporation. Preservatives with heavy, nonvolatile, insoluble 

 oils as constituents were known to be most effective. These require- 

 ments barred many chemicals that are otherwise very effective 

 insecticides. 



It was also desirable to determine the relative lengths of periods 

 of effective service that could be expected of the superficial methods 

 of treatment, such as brushing or dipping, compared with the more 

 permanent methods of impregnation. In commercial enterprises, 

 the type of treatment must necessarily be determined by cost and 

 length of service. 



When brush treatments are used, only high-grade antiseptic pre- 

 servatives such as coal-tar creosote oils or carbolineums should be 

 employed, since the cost of application of brush treatments is often 

 high. The cost of any treatment should necessarily be more than 

 offset by the longer service assured by the application. The several 

 methods of application or impregnation of the preservative should 

 be determined by the length of service required and the consequent 

 expenditure warranted. 



It was especially important to discover the most suitable preserva- 

 tives for finished forest products, such as those used in interior finish, 

 furniture, cabinet woods, etc., in order that American manufacturers 

 might compete with foreigners for trade with the Tropics in " white- 

 ant-proof " products. Such preservatives should not stain the wood, 

 should not have a disagreeable odor, and should not " sweat " out in 

 hot climates. It should be possible to paint or varnish over wood 

 treated by them. 



The proportions of poisonous chemicals necessary to add in the 

 manufacture of wood-pulp products to prevent attack by termites 

 were to be determined. 



