NOTES OX RECENT RESEARCH. 



251 



through a radius of from 12 to 20 inches, though it may penetrate 

 much farther than that. The general rule is to make three injections 

 per square metre (li square yards nearly) in light soils, and four injections 

 in heavy soils. The arrangement of the holes must necessarily vary 

 more or less, according to the system of planting. They should be at 

 regular intervals, however, so as to cover the ground evenly, and never 

 nearer than a foot to the base of the vine. It must be remembered that 

 to be effective all the ground must be treated, and not merely those places 

 where the presence of the enemy is proven by its injuries. 



Repeated Treatment. — On account of the liability of injuring the vines 

 it has been found best to make the treatment in two small applications, 

 separated by an interval of from six to ten days. This decreases the 

 density of the vapour, but continues its action for a much longer time. 

 It removes the danger of injuring the vines, and gives even better results 

 upon the insects than would be obtained by one large dose. The total 

 amount of carbon bisulphide to be used should be divided into as many 

 equal parts as there are injections to be made. The holes for the second 

 treatment should be intermediate between those of the first. 



Depth of the Holes. — The depth of the holes depends somewhat upon 

 the depth and permeability of the soil, the average depth being about a 

 foot. A depth of 16 inches is desirable upon d£ep or very permeable soil. 



Season of Application. — Treatment may be applied at any season of 

 the year ; but as it is followed by a slight check in growth it should not 

 be applied either at the flowering or fruiting season, as the check would 

 injure the crop most at those seasons. The injury to the vines results 

 from the killing of the tender fibrous feeding roots. It would therefore 

 be better to apply the treatment before these roots have started much — 

 that is, early in spring — or after they have become hardened — that is, 

 after fruitage in the fall. The condition of the soil usually favours the 

 spring treatment, and the condition of the insect is said to make it more 

 susceptible at that time. Spring, therefore, appears to be the most favour- 

 able season. 



Amount to use per Acre. — Two entirely different objects may be had in 

 treatment. First, to stamp out entirely and surely all traces of the pest 

 upon its first appearance in a vineyard, or when desiring to reset, regard- 

 less of the life of the vines ; second, to control the pest in such a way as to 

 prevent its multiplication while continuing the culture of the vineyard. 

 The first is called the extinction treatment ; the second, cultural treat- 

 ment. The method of application is the same in each case, but the 

 amount of the dose differs. To secure extinction it is usual to apply 

 about 300 grams (10 oz. nearly) per vine, using 150 grams in each of 

 two applications ten or twelve days apart. This is said to kill ninety-nine 

 out of every hundred vines. In cultural treatment the amount of the 

 liquid to be used varies according to the conditions previously described, 

 from 140 to 265 lb. per acre. 



Instruments for Application. — One of the principal difficulties in the 

 first use of carbon bisulphide was to force the vapours to the desired 

 depth. When first used below the surface it was poured into holes 

 formed by driving an iron bar with a maul. The demand for a more 

 convenient, accurate, and rapid working instrument was soon met by the 



