122 



useful only against pests such a< caterpillars, grubs, and slugs; that take 

 in solid food. Mr. Maskell puts the matter concisely. He says : 

 1 Whatever damage is done by (scale insects) is effected by the sucking 

 of the juices of the plant through the rostrum (beak) of the insect. 

 It follows from this that applications of any fluid to the tree externally, 

 with the object of poisoning the insects in their feeding, would be use- 

 less, as their food is dra^ n from beneath the surface.'* 



There are many substances fatal to insect life, but perfectly harm" 

 less to the higher animals, that may be safely used. A list of th e 

 principal insecticides, with directions for their preparation and applica- 

 tion, is appended. (See next Bulletin.) 



The most suitable season for spraying is when the young larvae are 

 hatchiu .: They are then in the most unprotected condition. In tem- 

 perate climates this season varies with different >pecies, 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 thorough. 

 The -uccess of the treatment depends upon rhe actual coutact 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 upward> against the backs of the leaves, or downwards on 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: — 

 1. 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 large apparatus is required, a barrel pump may be used. In this form 

 the pumping apparatus is fixed in a barrel *o which handles are attached, 

 -o 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 mount- 

 ed 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 inaccessi- 

 ble to the wheeled vehicle. Where the lay of land is suitable, and large 

 trees have to be treated, a more powerful apparatus may be mounted on 



* New Zealand Scale Insects p. 26. 



