BULLETIN 197. GRAPE CULTURE IN CALIFORNIA. 121 



Delaying the Spread of Phylloxera. When the Phylloxera has 

 entered the vineyard it can not be found until it has increased suffi- 

 ciently to kill or seriously weaken a vine. By this time it has usually 

 spread to at least several neighboring vines. It is usually hopeless to 

 attempt to eradicate it in this case without digging up and destroying 

 a very large number of vines, and even in this case there is no assurance 

 that other infected spots do not exist. Something, and in some cases, 

 much, however, can be done to delay its spread, and the main part of 

 a vineyard may often be preserved for many years by proper measures. 



The first thing to be done when infection is first discovered is to 

 dig up all the dead and weakened vines and a block surrounding them, 

 including at least three rows of apparently healthy vines on all sides. 



These vines should be all burned on the spot or piled up in the center 

 of the infested block, sprayed with coal oil, and left for several months 

 until the dry summer air has certainly killed all the insects on their 

 roots. A more effective method is to treat the infested area with 

 enough bisulfid of carbon to kill both the vines and the Phylloxera. 

 This is done by making holes with a crowbar 12 inches deep every 

 18 inches over the whole area. Into each hole is poured 1% ounces 

 of bisulfid and the hole closed immediately with the foot. This treat- 

 ment is best applied in April or May, after the vines have started and 

 before the ground becomes too dry. If any vines survive this treatment, 

 a new dose of 1 ounce to the 18 inches should be applied three weeks 

 later. 



However carefully either of these methods is carried out it affords 

 only temporary relief. In Switzerland, Algeria, and Germany, where 

 such methods have been applied with the utmost strictness and under 

 military supervision, the spread of the pest has been checked but not 

 stopped. 



In any case, plows or cultivators should not pass through affected 

 spots in the healthy parts of the vineyard. Cultivation is one of the 

 most effective means of carrying the root insects from one part of the 

 vineyard to another. 



Every effort should be made to discourage the introduction of 

 cuttings, and especially of roots, from infested to uninfested districts. 

 Wherever possible it is best to obtain planting stock in the immediate 

 neighborhood. 



Reestablishment of the Vineyard. When a vineyard becomes thor- 

 oughly infested, that is, when it contains several scattered, diseased 

 spots, or when 10% to 15% of the vines are known to be attacked, it 

 is useless to attempt to delay the pest by these means. The only 



