476
N. BALAKRISRNAN NAIR AND M. SARASWATHY
also be achieved by merely hauling the boats out of the water and exposing it to the hot rays of the sun and this very simple and effective
remedy has been recommended (Zernov, 1909 ; Orton, 1914 ; Grave,
1928 ; Erlanson, 1936).
Since exposure to fresh water is lethal for typical marine species,
mooring the vessels in regions of low salinity has also been recommended
(Weiss, 1917 ; Baughman, 1949 ; Nair, 1965). Unfortunately during
such operations, the borer can seal itself within its burrow and remain
alive for long periods of time. Therefore, the exposure to this unfavourable medium must be sufficiently long to kill the borers.
Other protective methods include introduction of poisons into the
surrounding water to create a toxic environment in the immediate
vicinity (Walker, 1924; Walker et al., 1926; Johnson, 1948); scupper
nailing (Jones, 1910; Von Schrenk, 1927; MacLean, 1941,1954; Edmondson, 1953) ; fixing shingles or glass particles over exposed wooden surfaces
(Anon, 1943) or completely sheathing them with boards (Andrews
and Graham, 1906; Atwood et al., 1924; Ohsima, 1940; Carr, 1953)
metal, concrete or any such suitable wrappings (Dudley, 1905 ; Roessler,
1906 ; Hardesty, 1908 ; Kennon, 1908 ; Davis, 1910 ; Anon, 1943b), metal
bands or pipe casings (Stempel, 1903; Kennon, 1904; Smout, 1905;
Hunt, 1906; Apfel and Earnest, 1908; Atwood et al., 1924; Upton,
1940; Adams, 1941 ; Johnson and McNeill, 1941 ; Edmondson, 1953)
or fixed or floating collars for piles (Walker et al., 1926; Johnson et al.,
1936 ; Johnson and McNeill, 1941 ; Johnson, 1948 ; Boas, 1947 ; Chellis,
1948; Allan, 1950; Anon, 1951). The discovery that a severe shocksuch
as a blow from a pile driver is detrimental to shipworms within a pile
soon found application. Thus dynamite was employed in the vicinity
of infested timbers (Neiley et al., 1927 ; Anon, 1944 ; Shackleton, 1949).
It has been claimed that a blasting schedule of 2 month intervals increased the service life of piling up to 3-4 years (Dynes, 1945). The
procedure consists of detonating from 10 to 12 charges of explosive
simultaneously in the water between pilings at low tide. Tests indicate
that 75% of teredo infestation is destroyed by this procedure. This
effective method is at present extensively used in the Canadian logging
industry (Yonge, 1951).
Electrolytic protection is yet another device (Clapp, 1926). Here
alternating rows of iron and copper nails or strands of copper and iron
wire are attached around a pile or wooden surface that needs protection. The electrolytic action taking place in the wood soaked with
sea water results in the deposition of iron oxide in the surface layers of
the wood and this apparently prevents the entrance of borers. Electrolysis of sea water and the liberation of chlorine etc., as a measure to
N. BALAKRISRNAN NAIR AND M. SARASWATHY
also be achieved by merely hauling the boats out of the water and exposing it to the hot rays of the sun and this very simple and effective
remedy has been recommended (Zernov, 1909 ; Orton, 1914 ; Grave,
1928 ; Erlanson, 1936).
Since exposure to fresh water is lethal for typical marine species,
mooring the vessels in regions of low salinity has also been recommended
(Weiss, 1917 ; Baughman, 1949 ; Nair, 1965). Unfortunately during
such operations, the borer can seal itself within its burrow and remain
alive for long periods of time. Therefore, the exposure to this unfavourable medium must be sufficiently long to kill the borers.
Other protective methods include introduction of poisons into the
surrounding water to create a toxic environment in the immediate
vicinity (Walker, 1924; Walker et al., 1926; Johnson, 1948); scupper
nailing (Jones, 1910; Von Schrenk, 1927; MacLean, 1941,1954; Edmondson, 1953) ; fixing shingles or glass particles over exposed wooden surfaces
(Anon, 1943) or completely sheathing them with boards (Andrews
and Graham, 1906; Atwood et al., 1924; Ohsima, 1940; Carr, 1953)
metal, concrete or any such suitable wrappings (Dudley, 1905 ; Roessler,
1906 ; Hardesty, 1908 ; Kennon, 1908 ; Davis, 1910 ; Anon, 1943b), metal
bands or pipe casings (Stempel, 1903; Kennon, 1904; Smout, 1905;
Hunt, 1906; Apfel and Earnest, 1908; Atwood et al., 1924; Upton,
1940; Adams, 1941 ; Johnson and McNeill, 1941 ; Edmondson, 1953)
or fixed or floating collars for piles (Walker et al., 1926; Johnson et al.,
1936 ; Johnson and McNeill, 1941 ; Johnson, 1948 ; Boas, 1947 ; Chellis,
1948; Allan, 1950; Anon, 1951). The discovery that a severe shocksuch
as a blow from a pile driver is detrimental to shipworms within a pile
soon found application. Thus dynamite was employed in the vicinity
of infested timbers (Neiley et al., 1927 ; Anon, 1944 ; Shackleton, 1949).
It has been claimed that a blasting schedule of 2 month intervals increased the service life of piling up to 3-4 years (Dynes, 1945). The
procedure consists of detonating from 10 to 12 charges of explosive
simultaneously in the water between pilings at low tide. Tests indicate
that 75% of teredo infestation is destroyed by this procedure. This
effective method is at present extensively used in the Canadian logging
industry (Yonge, 1951).
Electrolytic protection is yet another device (Clapp, 1926). Here
alternating rows of iron and copper nails or strands of copper and iron
wire are attached around a pile or wooden surface that needs protection. The electrolytic action taking place in the wood soaked with
sea water results in the deposition of iron oxide in the surface layers of
the wood and this apparently prevents the entrance of borers. Electrolysis of sea water and the liberation of chlorine etc., as a measure to