434 



dated so that the oldest or longest 

 seasoned wood can be used first. The 

 drier the wood, the more appetizing it 

 is to the powder-post beetles. 



Further protection can be gained by 

 periodic inspections of the stock so that 

 infested material can be removed for 

 burning or treatment. This is a live- 

 worm defect, and the insects will con- 

 tinue to bore until the product is 

 destroyed or they are controlled. 



SOME WOODS have chemicals in their 

 cells that protect them from insects, 

 and heartwood is more resistant than 

 sapwood. So, because insects are ready 

 to pounce even after the wood is safely 

 through storage and has been put to 

 use, it is sensible to select carefully the 

 species and grades that fit exactly the 

 purpose at hand. 



Whenever possible, one should use 

 the heartwood of the more naturally 

 durable or insect-resistant and rot-re- 

 sistant woods instead of the perishable 

 woods. Resistant woods like founda- 

 tion-grade redwood, the southern tide- 

 water red cypress, and the mahogany 

 contain alcohols, alkaloids, gums, res- 

 ins, or bitter essences that makes them 

 distasteful to boring insects. Some kinds 

 of wood that are not subject to attack 

 by certain wood borers but are adapted 

 for the same use should be substituted 

 for susceptible kinds. For example, yel- 

 low pine or Douglas-fir can be used 

 instead of oak for storage pallets to 

 prevent losses by Lyctus powder-post 

 beetles. 



The relative termite resistance of 

 certain native and exotic particularly 

 tropical American untreated timbers 

 has been determined by long-time serv- 

 ice tests conducted in the United States 

 and in the Canal Zone. 



Among those commercially available 

 in the United States are close-grained 

 heartwood foundation-grade Califor- 

 nia redwood, southern tidewater red 

 cypress, and very pitchy southern long- 

 leaf pine. The information from the 

 long-time service tests also permits the 

 recommendation of naturally resistant 

 woods for use in building or bridge 



Yearbook of Agriculture 1949 



construction where chemically impreg- 

 nated timber is not locally available, 

 especially in the various tropical re- 

 gions of the world. Greenheart, man- 

 barklak, and guayacan of the Americas, 

 teak and sal of India, molave and ipil 

 of the Philippines, and cypress-pine, 

 brush-box, and turpentine wood of 

 New South Wales are a few of the 

 woods found to be termite-resistant. 



TERMITE-PROOF FOUNDATIONS can 

 be constructed on the basis of field 

 research on the habits of termites and 

 their control. The research, including 

 studies of proper drainage of building 

 sites, grading necessary to secure suffi- 

 cient clearance between construction 

 timbers and the earth in which ter- 

 mites live, the role of wood debris in 

 the soil, soil moisture, temperature and 

 humidity in the building of earthlike 

 shelter tubes by termites over founda- 

 tions, and measurements and exact 

 location of ventilation openings, has 

 led to safe construction. 



Sound foundations can be con- 

 structed by the use of proper grades 

 of mortar for masonry units and im- 

 penetrable coal-tar pitches for sealing 

 expansion joints and vertical piping 

 that project through concrete. 



Porches, steps, and the like that have 

 an earthen fill can be sealed off or 

 separated from the main structure. On 

 the basis of tests of mortars, expansion- 

 joint seals, and barriers, specifications 

 for termite-proof foundations have 

 been written for various government 

 agencies charged with housing con- 

 struction. The measures recommended 

 will protect structures from attack by 

 termites for a slight additional cost. Ad- 

 vice given on the job to Federal housing 

 officials proved particularly useful be- 

 fore and during the Second World War 

 and resulted in more durable buildings 

 than those erected at the time of the 

 First World War. 



NEW BUILDING MATERIALS Were 



tested for the Housing and Home Fi- 

 nance Agency in an effort to speed 

 postwar construction. Many proved to 



