132 DESTRUCTIVE INSECTS OF VICTORIA : 



for the distribution of the holes. They are placed at equal distances 

 one from the other, in regular alternation as on a chessboard, so as to 

 produce a uniform impregnation of the soil. The number of holes of 

 injection must never be less than two per square metre (lOf square 

 feet). With less holes in that surface, the diffusion of the insecticide 

 vapours cannot be insured, even in very permeable soils. In general, 

 an augmentation of the number of holes, and a proportionate reduction 

 in each, favours a good saturation of the soil. When the soil is not 

 deep it is indispensable to augment the number of holes, to compensate 

 the waste of vapours towards the atmosphere. The same argument is 

 necessary for soils that are only slightly permeable. In general an 

 average of three holes per square metre represents the most convenient 

 disposition ; but in the case of compact soils there should be four holes 

 to the same surface. The depth of the holes of injection ought to be 

 twenty-five to thirty centimetres (10 inches to 12 inches). The holes 

 must be carefully covered over. 



" The dose for each hole ought to vary according to the number of 

 the holes and according to the quantity of sulphide which is to be dis- 

 tributed per hectare (about 2 J-ac.). Suppose, for example, that 240 kilo- 

 grammes (500 Ibs.) are to be employed per hectare, and that three 

 holes are to be made per square metre ; then the injector must be regu- 

 lated so as to give a dose of eight grammes (J oz.) at each stroke of 

 the piston. It is always necessary to verify during the work whether 

 the action of the injector is quite regular, and to take care that the 

 apparatus is in a condition to ensure accurate action. 



(t The principles which regulate the application of sulphide of carbon 

 by traction injectors are the same. In that case the distribution of the 

 insecticide takes place by the regular displacement of the furrows 

 traced along the vines. These lines of distribution ought not to be 

 distant more than one metre from each other. 



" With this mode of application of the sulphide it would not be 

 possible to attain, without injuring the roots, a depth of from twenty- 

 five to thirty centimetres (10 to 12 inches), at which depth the sulphide 

 is to be deposited. It is not possible to descend with traction injectors 

 below fifteen to eighteen centimetres ; it is therefore necessary to 

 compensate the more rapid waste of vapours by an augmentation of 

 the dose to about 25 to 30 per cent, over the quantities above indicated. 

 This waste is, of course, diminished by taking care to make the return 

 of the soil over the lines of injection as complete as possible. It may be 

 taken for granted that any want of success in the regeneration or the 

 maintenance of a vineyard will follow whenever traction injectors have 

 been employed without taking these precautions. 



" 3. Conditions of the Soil Favorable to Treatment. The treat- 

 ment ought never to be applied after ploughing or digging, because 

 when the soil is lifted the vapours of the sulphide escape towards the 

 atmosphere without producing their proper effect ; and for the same 

 reason it is necessary to wait about fifteen days after treatment before 

 any cultivation of the land. 



