THE GRAPE PHYLLOXERA IN CALIFORNIA. 121 



danger of phylloxera infestation following the planting of a cutting 

 from such wood. This danger does not exist in California, provided 

 the cuttings are not " heeled in " before transportation, because the 

 winter egg does not persist successfully. If the cuttings are " heeled 

 in" before transportation in an infested district, the possibility of 

 their becoming phylloxerated exists. Similarly, the possible danger 

 from gallicoles remaining upon the foliage of canes late into au- 

 tumn is nullified, because the gall-inhabiting forms do not normally 

 occur in California. 



The greatest danger of phylloxeration resides in the planting out 

 of infested rooted vines. This is a very abundant means of distrib- 

 uting phylloxera. Even if only one or two out of a thousand vines 

 are infested at planting, a " spot " or " spots " will form within a 

 few years, and the whole acreage eventually will become infested. 

 While the vines remain small, diffusion is slow because the roots of 

 one vine are separated from those of its neighbors, and underground 

 diffusion thus is rare if not impossible. Also, the relatively small 

 number of roots, coupled with the relatively small number of phyl- 

 loxeraB able to flourish thereon, prevents many opportunities for 

 aerial diffusion by wanderers. If the majority of the vines planted 

 out contain phylloxera?, however, the vineyard's complete phyllox- 

 eration is not long removed. In a phylloxerated district the employ- 

 ment of resistant roots obviates the necessity of treating the vines 

 before planting out in the vineyard, yet danger exists in cases where 

 grafted vines are planted too deeply and the stouter vinifera scion 

 is enabled to send out its own roots, in many instances crowding out 

 the roots of the resistant stock. The scion's roots, being nonresist- 

 ant, decay when phylloxerated just as though no resistant stock had 

 been employed, and the expense and trouble of the grafting process 

 are wasted. Even though phylloxera? live on resistant stock roots 

 in grafted vineyards without necessarily injuring the crop or vines, 

 there still remains the possibility that infestation will arise from 

 these grafted vines and that nongrafted vineyards near by will be- 

 come inoculated. Such a possibility is accentuated the greater the 

 proximity of two such vine areas, and especially if the nonresistant 

 area is to leeward of the grafted area or if water flows from the 

 grafted to the nonresistant vineyard. It is advisable, therefore, to 

 disinfect even resistant roots when these are to be planted in a region 

 free from phylloxera. 



PHYLLOXERATED LAND. 



Experiments with potted vines have given proof that phylloxera? 

 may live at least 10 months on buried severed pieces of roots, and 

 also that such pieces may remain sound for 18 months and at the 

 termination afford acceptable food for the insect. It is evident, there- 



