106 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



18 to 24 inches apart all over the vineyard, care being taken not to 

 put any nearer than one foot from a vine. The holes are made from 

 12 to 15 inches deep, and are closed immediately after pouring in the 

 liquid by pressing the soil with the foot. The holes may be made with 

 an iron rod or dibble; but, where the method is employed on a large 

 scale, special injectors are used, which much facilitate the work. The 

 injections are best made when the soil is fairly firm, and when it is 

 neither very wet nor very dry. This method succeeds only in rich, 

 deep, loose soils, and can not be used successfully in soil containing 

 much clay, or on dry, rocky hillsides or when the soil is saturated 

 with moisture. It is most effective in sandy soils, where the nature 

 of the soil is itself unfavorable to the insect. It is least success- 

 ful in warmer locations, where the insect is most prolific and most 

 harmful, and is used chiefly in the cooler locations where the 

 phylloxera does least damage. Vines which are much weakened by the 

 attacks of the insects can not be successfully treated, and all treated 

 vines require fertilization and most thorough cultivation. The annual 

 cost for material alone would be from $15 to $25 per acre; at the present 

 market price of carbon bisulfid. 



Submersion Method. 



Submersion is a cheaper and more effective method of controlling 

 the phylloxera, but is necessarily applicable to but few locations, and 

 even where most successful is gradually giving way to the more satis- 

 factory use of resistant vines. Its chief use is to preserve vineyards 

 which are already in bearing, and it may be of use temporarily in some 

 locations in California. In submersion the vineyard must be continu- 

 ously covered with at least six inches of water, as the object is to drown 

 the insects, that is, to kill them by depriving them of air. If the sur- 

 face becomes exposed even for a brief period, air will be absorbed and 

 the insects given a new lease of life. In very porous soils submersion 

 is impracticable on account of the large amount of water required, and 

 ineffective for the reason that the rapid passage of the water carries 

 sufficient air into the soil to keep the insects alive. Submersion is 

 most effective in destroying the insects when they are in their most 

 active condition, that is, in summer. At this time, unfortunately, the 

 vine is also most sensitive to injury. The most favorable time, then, 

 for submersion is as soon as the vines have ceased active growth and 

 before the phylloxera have entered their hibernating or dormant con- 

 dition. This in most parts of California will be some time in Novem- 

 ber. At this period the flooding need last but a week or ten days; a 

 month later, two or three weeks; while during the remainder of the 

 winter little good results unless the submersion is prolonged for thirty- 



