THE GRAPE PHYLLOXERA IN CALIFORNIA. 109 



below occurred. The soil of the fourth pot was watered sparingly, 

 and few cracks were formed. July IT, 12 wanderers were shaken onto 

 the soil. No infestation of the root below occurred. Only one out 

 of the four experiments resulted positively, and in that one the 

 soil was very well cracked, affording access to the root. 



Inoculation of the wanderers on living vines was attempted 

 through the following experiments : Five lots of four vinif era vines 

 each were planted, two on light sandy loam and three on heavy clay 

 loam. The vines were all young rooted vines, and they were planted 

 roughly in the form of squares during the month of June. In the 

 center in each one of four of the groups a phylloxerated vine (potted) 

 was put in the ground at varying distances from the four surrounding 

 vines. In one group the four outside vines were distanced, respec- 

 tively, 14 inches, 2 feet, 3 feet, 3^ feet from the central vine. In a sec- 

 ond group they were distanced, respectively, 2, 3, 4, and 6 feet from the 

 central vine. In the third group they were distanced, respectively, 

 2, 4, 6, and 8 feet from the central vine. In the fourth group they 

 were distanced, respectively, 2, 3, 4, and 6 feet from the central vine. 

 In the fifth group the four vines were potted, and in place of an 

 infested central vine, infested roots were buried 1, 2, 3, and 4 feet, 

 respectively, from the outside vines. In this last case the vines were 

 potted to prevent possibility of underground inoculation. The four 

 central vines remained infested throughout the summer, but it was 

 not disclosed that they, or the buried roots, produced any wandering 

 larvae above the surface. The surface of the soil in the area used 

 for these experiments was kept well cracked. In no instance did the 

 20 outside vines become infested. 



In 1915, field experiments were conducted in a vineyard which 

 had several large phylloxera " spots " both on light and heavy soils. 

 The light soil might be described as a silt loam with a clay admix- 

 ture, and the heavy soil was black, sticky clay. In spring a number 

 of sound rooted vinifera vines 1 year old were procured and planted 

 in 5-gallon kerosene cans from which one side had been cut. Differ- 

 ent types of soil were used in these cans. The vines thus planted 

 were kept apart until July, when they were carried out to the vine- 

 yard selected and planted level with the soil at varying distances 

 from vineyard vines from which wandering larvae were known to 

 be issuing. To insure cracking of the soil, water was applied to 

 the soil surface and also to the soil between the cans and the near-by 

 vine. Wandering larvae were observed in this vineyard from the 

 middle of July to August 20. In September, after the wandering 

 of the larvae had ceased, the cans were dug up. Table XXXV gives 

 the results of this experiment. 



