THE PHYLLOXERA, OE GRAPE LOUSE OF THE VINE. 131 



used. In every case the object is to attack the insect at the roots, and 

 to obtain as complete an insecticide effect as possible. For this it is 

 indispensable that the whole mass of the soil should be impregnated, as 

 completely, uniformly, and rapidly as possible, by the vapours of the 

 sulphide, sufficient to render the atmosphere underground unrespirable by 

 the insect. The dose is the same for killing one or thousands of 

 phylloxera, so that the viticulturist must not make the doses any 

 different for a field in which he supposes that there only exist very few 

 insects than for one which is entirely invaded. The diminution of 

 doses can only have the effect of employing uselessly a product which 

 can only have a sufficient insecticide energy if used in proper quantities. 



" The minimum of sulphide to employ is 20 grammes per square metre, 

 or 200 kilogrammes per hectare (i.e., \oz. to lOf square feet, or, say, 

 175/fo. per acre). Less than this quantity, even under the most 

 favorable conditions of the soil, will not insure proper treatment. It 

 is even desirable in soils of an average depth, to increase the dose to 

 240 or to 250 kilogrammes. This is the dose, in fact, which answers 

 best in the majority of vineyards ; and for deep soils one ought not to 

 hesitate to increase the dose even to 300 kilogrammes, say 6 cwt., 

 per hectare (2 acres). The reason will be easily understood for this 

 augmentation, since the object is to impregnate a greater depth of soil 

 occupied by the roots and by the parasites. 



"In the determination of the proper dose of sulphide of carbon, 

 account must be taken not only of the depth of the soil, but also of the 

 permeability both of it and of the- subsoil in which the roots penetrate. 

 Light and permeable soils contain more air than others, so that in order 

 to impregnate them completely with toxical vapours a higher dose of in- 

 secticide is necessary. On the other hand, some subsoils are more 

 favorable to a uniform distribution of these vapours. When the soil 

 is at once permeable and deep, and the subsoil is one in which the roots 

 penetrate easily, the maximum doses of sulphide ought to be applied. 

 Vines submitted to too feeble a treatment remain each year under the 

 influence of the parasite, which is not sufficiently attacked. 



" 2. Distribution of Sulphide of Carbon. Sulphide is applied by 

 divers instruments by Pal-injectors or by traction injectors. The 

 Pal-injectors distribute the sulphide by small doses, injected in holes 

 which are regularly made in the soil; the traction injectors distribute 

 the insecticide in furrows traced by the ploughshare. 



" The soil of a vineyard is occupied entirely by roots, which cross each 

 other and form a continuous network, even where the vines are planted 

 in lines, leaving between them large spaces reserved for other cultiva- 

 tion. It is therefore necessary to inject the sulphide uniformly through- 

 out the soil; and the doses must be calculated proportionately to the 

 whole surface of the vineyard, whatever may be the method of planta- 

 tion, and whatever may be the age of the vines. 



" When, as is most often done, the treatment is by the Pal-injector, 

 the disposition of the holes of injection should vary with the different 

 modes of plantation, because the lines of vines serve as an indication 



K2 



