MARINE BORERS

Evening Star, Issue 18051, 19 August 1922, Page 11

MARINE BORERS

The American Wood Preservers’ Association has taken np the subject of marine borers with vigor, moved to this end by tbo very serious loss duo to the action of these posts on tbo harbors of the Pacific Coast. This association has issued a report which shows that a very 'thorough and systematic investigation will be pursued 1 throughout the whole length of the coastline of the United States. It appears that in past years, sinoo 1870, the attacks in San Francisco Bay have been sporadic and varying in virulence, but in the earlier period little attention was paid to the pest, as it was believed that the quantity of fresh water discharged into the bay from the combined flow of the Sacramento and San Joaquin Rivers would reduce the salinity of the water to such an extant that it would prove an unfavorable habitat for teredo and limnoria. This expectation, apparently, was not well founded, and with time the depredators have increased. It may be suggested that the enormous quantity of water drawn from tho upper reaches and tributaries of these rivers for tho purposes of irrigation has diminished tho supply of fresh water, and has allowed the salinity at tho outfall to increase to such an extent that the breeding of tho teredo has been encouraged. Moreover, in recent years the rainfall has been below the normal, and it is in those years that the ravages have been greatest. In 1917 damage to timber piling becamo evident, and two years later waterfront structures in tbo bay erected cm piles began to fall, and in some cases whole docks were affected. Loss and insecurity becamo so great that the Wood Preserving Association appointed a committee to study the problem ; but this committee did not -begin active work till July, 1920. Previous to this date the United States Forest Service and other agencies had made local investigations concerning the activities of marine borers and the methods of their clue control. These scattered associations have now concentrated their efforts in a sysematic programme, which, has for its object the investigation of the entire problem, including the hydrographic, the biological, and the engineering phases. Tbo biological work carried out under the superintendence of Dr C. A. Kofoicl shows that invasions of borers are induced- by the shipping traffic, and that preventive measures absolute necessity. The port of San Francisco has become the resort of the most widely-known and most destructive representatives of the groups to which they belong. To these importations, however, California contributes on its own account, a pest of special virulence. The xylotrya is, however, no mean second in the competition, . and, though it adopts unusual habits of boring, thoy°ean prove very effectual Some of tho piles in the' dolphin or the Alameda Mole, driven in February, 1919, were so weakened at the mud lino by the tunnelling of xylotrya that they had to Ire removed in November, 1920. Teredo navalis can accomplish 4in penetration in as many months, and is a foe to be respected. Among the crustacean borers is the limnoria lignonnn, a species which acquired considerable notoriety, and whoso ravages are very destructive, since they often complete tho work of the teredo. —‘ jEnniueoring.’ •