Marine borer

Marine borers inhabit saline or brackish waters where they cause serious destmction to untreated wood. The moUusks include the Teredo and Bankia borers among the cmstaceans, the Limnoria borers are the most widespread and destmctive. Preservatives or borer-resistant woods deter marine borers (see Coatmgs, marine). 

The best protection for wood against the attack of decay fungi, insects, or marine borers is obtained by applying preservatives under pressure before installation (61,62). Both oil-type preservatives, such as creosote or petroleum solutions of pentachlorophenol, and waterborne preservatives, such as copper-chrome arsenate and ammoniacal-copper arsenate, are used when wood is to be in direct contact with the ground or in the marine environments. 

Most wood species are subject to some form of biological attack, a hazard not encountered by most other constructional materials. Fungal decay and attack by termites and other insect borers and marine borers are the main problems. The heartwood of many timber species and the sapwood of most species can be impregnated with wood preservatives to prevent these problems. 

Marine Borers and Methods of Preserving Timber against their Attack, Tech. Note 59, B.R.E., H.M.S.O., London (1975)... 

Wooden racks used in sea-water tests are likely to be subject to severe damage by marine borers. The wood used, therefore, must be treated with an effective preservative, for example creosote applied under pressure, if the test is to extend for several years. Organic copper compound preservatives may suffice for shorter tests, for example 2 or 3 years. Since the leaching of such preservatives may have some effects on corrosion, metal racks fitted with porcelain or plastics insulators have an advantage over wooden racks. 

The situation with some forms of biological deterioration is somewhat different. Where the agent is macrobiological, as in the case of rodents, insects, and marine borers, the attack is physical in nature, such as by gnawing or boring. The attack is not at the atomic or molecular level. Any breaking of molecular bonds such as in polymer chain shortening is thus accidental. The attack may be said to be at the material s structural level, not the polymer molecule level. 

Marine applications, high performance fibers in, 13 395 Marine biofouling, 7 151-152 Marine borers, effect on wood, 26 353 Marine coatings, 7 144 7 192-206 10 442-444... 

Johnson and Rowell (1988) found that some protection against marine borers was obtained by acetylating wood, but this was lower than that obtained with CCA or creosote treatment. Larsson Brelid etal. (2000) also found that acetylation provided only slight protection against attack in a marine environment. However, Westin etal. (2004b) exposed five acetylated pine samples (21 % WPG) at a marine test site, and found that four of these were free from attack after 4 years exposure. Untreated pine sapwood samples had failed after 1 year due to heavy attack by Teredo navalis. 

Johnson, B.R. and Rowell, R.M. (1988). Resistance of chemically modified wood to marine borers. Material und Organismen, 23(2), 147-156. 

Methyl, 2-hydroxymethyl-, and 2-formylanthraquinones in the heart wood of teak (Tectona grandis, Verbenaceae) are effective in inhibiting termite activity (105). Several naphthoquinone derivatives including lapachol are thought to impart marine borer resistance to woods, e.q. that of Tabebuia quayacan (Bignoniaceae) (108). 

WOOD PRESERVATIVE. A material applied to wood to prevent its destruction by fungi, wood-boring insects, marine borers and fire. A common characteristic of these materials is toxicity to those organisms that attack wood, or in the case of fire retardants the ability to control combustion in terms defined by the Underwriters Laboratory. In addition, a satisfactory wood preservative must aiso (a) be capable of penetrating wood, (bi remain in the wood for extended periods withonl losing its effectiveness due to chemical breakdown, (c) be harmless to humans and animals, (d) be noncorrosive and. (e) be available in quantity at a reasonable cost, Foi certain uses, the preservative may be required to be colorless, odorless, nonswellmg and paintable. 

Of the large number of toxic chemicals that are oil-soluble, only three are recognized by the American Wood Preservers Association and only one of these is a commercially important wood preservative, pentachlorophenol (CgCFOH). Although penta is effective against fungi and insects, it will not protect against marine borers, and hence cannot be used as a wood preservative for salt water installations. 

In preliminary tests, alkylene oxide-treated southern pine (28) was found to be resistant to termite attack and attack from the marine borers, Teredo (shipworm) and Limnoria. 

Compreg is highly resistant to decay and attack by termites and marine borers (52). Its electrical and acid resistances are also real high. 

As indicated above, the new applications of organolead have been fostered largely through the interest of ILZRO. The most promising new applications are in the fields of marine antifouling paints, marine borer repellants for wood, antiwear additives for lubricants, polyurethan foam catalysts, and molluscicides for bilharzia control in tropical areas. 

Wood, as a natural plant tissue, is subject to attack by fungi, insects, and marine borers. Some species of wood are more resistant to decay than others (e.g., the heartwood of cedars, cypress, and redwood) because of the presence of natural toxic substances among the extractable components. Most woods, however, are rapidly attacked when used in contact with soil or water, or when exposed to high relative humidities without adequate air circulation. Wood for such service conditions requires chemical treatment with toxic chemicals, collectively termed wood preservatives. The service life of wood may be increased 5- to 15-fold, depending upon the conditions of preservative treatment and the nature of the service. 

Unmodified control specimens are destroyed by marine borer attack in less than 1 year in a marine environment. Epoxide-modified specimens have been tested for over 5 years with very little marine borer attack 114). The mechanism of effectiveness of modified wood in resisting attack by marine organisms is unknown. As with the... 

Table III lists representative wood-decomposing insects and marine borers and summarizes some features of their action on wood. Figure 2 shows the extensive damage caused by some of these wood-decomposing animals. Only a few detailed studies of the chemistry and biochemistry of wood degradation by the insects and marine borers have been made. Because the animals derive nourishment from the structural polymers of wood, the subject is of practical significance and deserves more research attention.

Table HI. Decomposition of Wood by Some Insects and Marine Borers...

---