654 Agricultural Gazette of N.^AW [86^.2, 1920. 



The Control of Cattle Tick/ 



Experiments with Arsenical Dipping Fluie>s. 



L. COHEN, F.C.S. 



DuRixG the period of thirteen years that has elapsed since the cattle tick 

 {Margaropus Australis or Boophilus Australis) first made its presence felt in 

 the 8tate of New South Wales, the treatment of infested or suspected stock 

 with arsenical solutions, together with a system of quarantine, has been the 

 method adopted by the (lovernment with a view to the eradication of the pest. 



Since the general introduction of arsenical dipping fluids in various parts 

 of the world, it has been observed that the original arsenious oxide in many 

 baths tends to become converted by oxidation into arsenic oxide. This more 

 highly oxidised form of arsenic was understood to have considerably less 

 effect on the tick than in its original condition^ but the experiments on the 

 subject caunot be said to have established anything very definite in regard to 

 the relative tick killing power of the several forms. 



The principal obstacle in the way of experiments on ticks in New South 

 Wales is the scarcity of tick-infested cattle, but an opportunity arose in the 

 latter part of lyi'ii of operating on a Queensland herd, the property of Mr. 

 T. Campbell, of Murwillumbah, who was at that time a member of the New 

 South Wales Tick Advisory Board. By the courtesy of this gentleman we 

 were enabled to carry out expei'iments on his property, " Helen's Vale," 

 Oxenford, South Queensland, in 1916 and 1917, and again in 1920. 



The conclusions to be drawn fi'om the results of this series of experiments 

 are : — 



1. The IDepartmental dipping formula contains more arsenic than is 

 required to produce the best results. 



2. The Departmental mixture at full arsenical strength has intrinsically 

 no deleterious eti'ect upon cattle, including dairy cows in full milk. 



3. Arsenate up to 0"3 per cent, b}' itself, or up to 0'2 per cent, combined 

 with 0"1 per cent, of arsenite, has no noticeabl}' injurious effect on cattle. 



4. Enmlsion is not essential to a dip fluid, provided the utmost care is 

 taken to ensure the thorough wetting of every portion of the skin of the 

 beast. As, however, this is impracticable in routine eradication work, the 

 employment of emulsion is desirable for all ordinary purposes. 



5. iJuring the second moult, ticks are able to resist successfully the action 

 of arsenical fluids at all commonly employed concentrations. 



6. Even at less than half " standard " arsenical strength, the only surviving 

 ticks appear t<j be those undergoing the second metamorphosis ac the time of 

 treatment. 



7. Arsenate possesses appreciable tick-killing power, probably about one- 

 third that of arsenite. 



8. Arsenical fluids appear to act more rapidly in summer than in winter. 



9. In continuous di})ping for eradication purposes, treatment in weaker 

 solutions at shorter intervals appears to offer l)righter prospects of success 

 than the present method. 



10. Cattle leaving quarantine might advantageously receive two dippings 

 with a four-day interval in a 5 lb. solution, instead of with a five to ten-day 

 interval in an 8 lb. solution. 



* Summary of a report made available by Mr. S. T. I). Symons, Chief Inspector of Stock. 



