29 



hand who will undertake fumigation as a private enterprise, pro- 

 viding, of course, in either case, that the treatment can thus be econo- 

 mically secured. There is nothing difficult about the work, nor is 

 previous experience or knowledge of chemicals necessary ; but as in 

 almost any work however simple, experience and knowledge are 

 valuable, and especially so as serious consequences may follow negli- 

 gence or carelessness. 



POINTS TO REMEMBER. 



Fumigation with hyrdrocyanic acid gas is by far the 

 most successful remedy known for scale insects of citrus 

 trees, and it is believed that such fumigation may be 

 economically employed on nearly all farms in Cape 

 Colony where citrus trees are grown. 



The covers for the trees must be free of holes and be 

 of cloth which has been made air-tight. 



The hydrocyanic acid gas is generated by the action of 

 sulphuric acid on potassium cyanide in the presence of 

 water. 



The trees are not materially injured if the proper 

 amounts of the chemicals are used, and if the opera- 

 tions are carried on in the absence of sun-light. 



The gas is deadly poisonous to man, and extreme 

 care should be taken to avoid breathing it as it rises 

 from the generating vessel; mixed with air, it is not so 

 poisonous. Potassium cyanide is as poisonous as the 

 gas. Sulphuric acid " burns " almost everything with 

 which it is brought in contact. 



The chemicals should always be kept under lock and 

 key, and the containing vessels plainly labelled with the 

 name and the warning "DEADLY POISON." 



When feasible it is urged that the farmers of a 

 neighbourhood combine and engage a trustworthy man 

 to attend to the work ; but when co-operation is 

 impracticable, it is recommended that the farmer fumi- 

 gate his own trees. 



The operations are very simple and can be safely 

 carried on by any careful man. 



