Because of the toxic nature of mercuric chloride, research aimed at its use 

 in eradication of a species should be performed with great caution and under strict 

 quantitative control . 



Formalin 



Stauber (1943) looking for an organic compound which could be detoxified by 

 organic matter after treatment, found that a solution of one part of formalin and 100 

 parts of sea water (approximately 1:300 formaldehyde. H^CO) killed all egg case 

 stages in three minutes. The same concentration for only one minute did not kill 

 all the embryos and some of these formed atypically for a time, but none ever 

 hatched Field experiments in which a 1:100 solution of formalin was used for five 

 minutes confirmed his laboratory data . In these studies oysters with attached egg 

 cases were dipped and then confined in cages. Some oysters were killed by this 

 treatment, particularly those whose bills were injured in any way. Stauber suggests 

 that oysters with injured bills and exposed to the chemical are so weakened that they 

 gape and then are vulnerable to the attacks of predators. He concludes that formalin 

 is not as effective a molluscacide in this case as copper sulfate, and emphasizes the 

 need for extensive field trials in the development of large scale control procedures. 



Rotenone and amox 



Newcombe and associates, Virginia Fisheries Laboratory (1941-42), per- 

 formed a number of laboratory experiments to determine the efficiency of various 

 concentrations of rotenone, C23H22O5, in killing the various developmental stages 

 of drills within the egg case . Egg cases attached to live oysters were submerged in 

 rotenone solutions and then placed in flowing York River, Virginia, water of salinity 

 18 0/00 and temperatures averaging 25" C and watched daily until disintegration or 

 hatching of the young was observed. Treatment was most effective if egg cases were 

 permitted to remain out of water in the sun for at least two hours after treatment 

 with rotenone, since increased temperature speeds the action of rotenone . It was 

 determined that fresh solutions of rotenone in concentrations of 3: 1, 000 applied to 

 the egg cases either as a spray or by dipping, effectively arrested development of 

 all stages up to those in which the shell was beginnir.g to form . No concentration 

 of rotenone used was effective in killing later prehatching stages . A similar insecti- 

 cide, amox, proved to have approximately the same effect as rotenone. Concentra- 

 tions of rotenone and amox in all experiments proved nontoxic to oysters . 



Search for new compounds 



The possibility of controlling drills on the bottom where they occur through 

 the application of chemicals has been in the minds of marine biologists for some time. 



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