The degree of handling evident in this method does not lend itself to use m 

 America . 



Magnesium chloride 



Hon (quoted by Cahn, 1950) to remove oyster drills from oyster spat 

 also recommends placing the seed oysters in a 30% solution of magnesium chlor- 

 ide (MgCl2> for one to two minutes; after shaking off the drills wash seed in normal 

 sea water He states that a combination of the brackish and fresh water treatment 

 is more effective . 



Copper sulfate 



Engle (1941) reported the effective killing of the prehatching stages of the 

 oyster drill in the laboratory in Connecticut by dipping the egg cases in a solution 

 of ore part of Q1S04 in 200 parts of sea water for one minute . Development of the 

 stages ceased shortly after exposure to the poison and all ages were destroyed. 

 The oysters were unharmed by this treatment even after exposure of 10 minutes . 

 Weaker solutions of the chemical 1:300, did not kill all the embryos, but stronger 

 solutions were as effective as 1:200, He recommended the use of a longer exposure 

 time in large scale field control operations . 



These experiments were repeated by Newcombe in Virginia (1941-42) and 

 the results generally confirmed Engle s findings, but indicated that under the 

 Virginia conditions dipping of commercial oysters bearing drill egg cases in a 

 1:500 solution of CUSO4 for one minute was adequate. 



Lindsay and McMillm (1950) report that CU&O4 has been used to destroy 

 drills on a commercial scale in Liberty Bay, west coast of the United States, on 

 the recommendation of A. J. Bajkov. The chemical was applied as crystals mixed 

 with a wetting agent and spread from the dusting hopper of an airplane . The reported 

 results of this dusting indicate that the CUSO4 was highly effective against egg case 

 stages and young drills but only moderately effective against adults, and that no 

 effects on oysters were noted. Lindsay and McMillin carried out a number of 

 experiments in the laboratory in the State of Washington in 1945 and again in 1949 

 and also found that CUSO4 has a decided toxic effect on the prehatching stages of 

 the drill even in concentrations as low as, 1:5900 to 1:400. They performed no tests 

 on young hatched drills, but write that the efficiency of CUSO4 in killing adult drills 

 was not borne out by their tests . They also emphasize the fact that CuS0 4 is 

 extremely toxic to young salmon and to minute plant and animal life, and although 

 very little quantitative information is available on its effects on marine life, it is 

 highly probable that CUSO4 could seriously reduce the quantity of microscopic food 

 in a bay where considerable quantities of this poison were used to kill oyster drills. 

 The latter point is also stressed by T. C. Nelson (pers . com.). Lindsay and 



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