108 BULLETIN 903, U. S. DEPARTMENT OE AGRICULTURE. 



testation was caused by two wanderers from an adjoining cage. It 

 was judged that this infestation must have occurred about June 20, 

 when many eggs were hatching in the adjoining cages and manj^ 

 rootlets decaying, thus compelling the newly hatched larvse to seek 

 food elsewhere. 



INOCULATIONS WITH WANDERERS. 



On July 31, 1913, 30 wandering larvae were taken from jars in 

 the cellar and placed on pieces of sound severed roots in a petri dish. 

 On August 13, 25 half-grown phylloxera? found roaming around in 

 jars were added. All the latter deserted the roots and died, but of 

 the former, three matured August 25 to September 18. A later in- 

 oculation (Sept. 25) with 40 young wanderers resulted in none of 

 these remaining. Another similar experiment was tried on Septem- 

 ber 29, with 40 young wanderers, but it also failed. Thus out of 

 135 individual wanderers only three matured. 



In 1914 this experiment was repeated, and two pieces of sound 

 severed roots were inoculated in a petri dish, one with 8, the 

 other with 40 wanderers. In this case a layer of moist sand was 

 placed below the roots, whereas in 1913, only filter paper had been 

 used. Of the smaller lot 1 and of the larger lot 20 matured. Thus 

 On August 28, 15 wanderers from jars in the cellar were placed on 

 the living root of a Tokay, and 3 of these hibernated and developed 

 the following spring. 



In the autumn of 1913 an attempt was made to inoculate the roots 

 of sound potted vines by means of wandering larvse placed upon 

 the surface of the soil in the pots. For this purpose, 35 wanderers 

 were placed on the soil of each of four potted vines (Resistant 

 hybrid, Sept. 18; Agawam, Sept. 23; Burger, Sept. 26; Thompson's 

 Seedless, Oct. 6). In no case did the wanderers succeed in inoculat- 

 ing the roots. The soil, however, contained extremely few cracks. 



The following year this phase was pursued further. Sound pieces 

 of roots were planted 4 inches below the surface in four 9-inch pots. 

 On July 8, 30 wanderers were placed on the soil surface of the first 

 pot, the soil being cracked from having been watered the previous 

 day. The root below was never infested. The soil of the second 

 pot was watered to cause it to crack extensively. After it became 

 well cracked about 25 wanderers were shaken on it, July 8. An ex- 

 amination of the root, August 25, showed it to be infested with a 

 thriving colony of phylloxera?. In the third pot the soil was not 

 watered; consequently there was no cracking. On July 12, 50 wan- 

 derers were shaken out on the surface. No infestation of the root 



