are pushed out of the way through small ventholes about 1 millimeter in 

 diameter in the wood. A structure attacked by termites will eventually 

 fail unless the infestation is discovered early and the termites destroyed. 



Termite control can be accomplished in several ways. Separation of 

 structural wood from the ground and removal of all cellulose material from 

 the ground in the vicinity of the structure are accomplished in the design 

 and construction phases. Dry ground, good ventilation, and exposure to 

 sunlight also discourage termites from nesting. If contact with the ground 

 cannot be avoided as in the case of power poles, pressure treatment with 

 preservatives will discourage termites. Poison can be injected into the 

 wood and nesting areas where termites are established. 



e. Fungi. The decay fungi, which are of primary concern, consist of 

 microscopic threadlike strands known as hyphae; these aggregate into a mass 

 called mycelium. The mycelium under suitable conditions form fan sheets, 

 especially when developing in a very moist locality. These may give rise 

 to the fruiting body of the fungus which, in the case of the decay fungi, 

 is relatively flat. These fruiting bodies bear enormous numbers of micro- 

 scopic spores which are similar in function to the seeds of higher order 

 plants. The spores are readily distributed by water or air currents, or by 

 men and animals. Spores germinate and penetrate wood by means of hyphae. 

 The fungus may also be spread from decayed material to sound material by 

 the hyphae . 



In the United States there are many species of fungi that cause wood 

 decay. Two important species are the building poria, Poria incvassata, and 

 the tear fungus, Merulius lachrymans . The tear fungus is more common in 

 northern United States and Canada; the poria fungus prevails in the south 

 and west (Thomas, 1951). Timber destroying fungi require both moisture and 

 oxygen at a temperature of about 20 to 36 Celsius (68 to 97 Fahrenheit) 

 for optimum growth. Therefore, wood that is kept very dry will not decay 

 nor will wood that is submerged where the oxygen is excluded. Because wood 

 must be kept moist, the term "dry rot" is a misnomer for the crumbly brown 

 rot that results from the action of fungi. Figure 67 shows specimens of 

 wharf timbers heavily damaged by fungi. 



Control of fungi in wood structures can be accomplished by proper 

 design and by chemical treatment. Design criteria should anticipate meteor- 

 ogical conditions such as fog, rain, or dew which may deposit moisture on 

 wood surfaces. Wood structures should be designed to provide for drainage 

 of wood surfaces and eliminate joints and pockets where moisture can collect. 

 Where exposure to moisture is severe and cannot be eliminated by design, 

 pressure treatment with a wood preservative is required. Coal tar creosote, 

 copper napthenate, pentachlorophenol and salt preservatives such as chromated 

 zinc chloride are used separately or in combination for fungi control. 



7 . Preservative Treatment of Wood . 



a. General . To extend the life of wood for both economical and practical 

 use in the coastal zone, it must be protected from its natural enemies-- 

 fungi, bacteria, insects, and marine organisms. Effective preservative 

 treatments have been found to discourage the natural enemies and extend the 

 useful life of wood to about four to five times that of untreated wood. 



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