Remedial Measures and Insecticides. xxi 



The most suitable season for spraying is when the young larvae 

 are hatching. They are then in the most unprotected condition. 

 In temperate climates this season varies with different species, and 

 should be made the subject of careful observation. In tropical 

 countries many species, and those naturally the most pernicious, 

 appear to produce a constant succession of broods throughout the 

 year. 



To produce any permanent result, spraying must be very tho- 

 rough. The success of the treatment depends upon the actual 

 contact of the liquid with the individual insects. Even when the 

 work is done by a trained man, it is practically impossible to 

 secure the destruction of every individual. The difficulty is greatly 

 increased when the work has to be intrusted to natives. In 

 conducting the operation, the position of the insects upon the 

 branches and foliage must be carefully noted, and the nozzle of 

 the machine manipulated accordingly, so as to throw the spray 

 upwards against the backs of the leaves, or downwards on to the 

 upper surface, or horizontally against the stems and branches. 



A few words may be said as to the apparatus for spraying. 

 This is not the place to advertise any particular make of machine ; 

 but some general principles may be given to help the would-be 

 purchaser in his choice. 



Points to be considered in the selection of a machine should 

 be:— 



I. Adaptability to Transport. — For ordinary use, where small 

 trees only have to be treated, there is no form so convenient as 

 the knapsack pump. This consists of a metal vessel that rests 

 upon the back, and is supported by straps passing over the 

 shoulders of the operator. The handle of the pump (in the best 

 patterns) comes forward under the left arm, and is worked by the 

 left hand, leaving the right hand free to direct the nozzle which is 

 attached by a flexible rubber tube. The vessel usually contains 

 the pump cylinder, and space for about four gallons of liquid. 

 Where a larger apparatus is required, a barrel pump may be used. 

 In this form the pumping apparatus is fixed in a barrel to which 

 handles are attached, so that the whole apparatus can be carried 

 from place to place by two men. Where the land is flat the barrel, 

 or a metal tank, may be mounted on wheels for transport ; but it 

 should be designed so that the vessel may be dismounted and 

 carried by hand to such places as are inaccessible to the wheeled 

 vehicle. Where the lay of land is suitable, and large trees have 



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