THE GRAPE PHYLLOXERA EN CALIFORNIA. 15 



At this time the phylloxera was known to exist more or less 

 throughout the valley, and had been identified in different vineyards, 



but as yet its injury had not reached the advanced stage of noticeable 

 characteristic phylloxera spot.-, was therefore little in evidence, and 



was not considered a prominent factor in connection with the de- 

 struction of the vineyards. 



The following facts were brought out during the writers" investi- 

 gations and have a direct bearing upon existing conditions in the 

 Santa Clara Valley at that time : 



Extensive areas of a vineyard may be infested by phylloxera be- 

 fore characteristic spots are noticeable: a lighter crop and a slight 

 decline in vigor of growth are for some time the only apparent signs 

 of injury. 



Infested vines change suddenly for the worse, becoming rapidly 

 stunted in growth, or even dying, when influenced by unusual con- 

 ditions either from lack or excess of moisture. 



Injured roots, functioning poorly under normal conditions of 

 moisture, reproduce with difficulty fibrous roots, or feeders, to replace 

 those which have been destroyed by the insect, and when subjected to 

 drought they starve the vine. 



Excessive moisture, instead of benefiting injured roots, causes them 

 to rot and hastens the death of the vine. 



For these reasons it is believed that the phylloxera was responsible 

 for a far greater share of the destruction of the Santa Clara Valley 

 vineyards than has been ascribed to it. 



While Santa Clara and the southern counties have lost in acreage, 

 a larger gain has been made at about the same period and later 

 in other counties, especially those of Sutter. San Joaquin, and 

 Fresno. Many vines throughout the State have been killed by 

 phylloxera and not replanted: more have been grubbed out and 

 replanted, sometimes more than once, and it is estimated that the 

 loss in these respects has been very considerable. 



Mr. George C. Husmann. pomologist in charge of viticultural 

 investigations. Bureau of Plant Industry. United States Department 

 of Agriculture, estimates the loss at 75,000 acres: Prof. F. T. Bioletti. 

 of the viticultural department of the University of California, makes 

 a similar estimate: and Charles C. TVetrnore. for many years identi- 

 fied with the board of State viticultural commissioners, considers 

 this estimate conservative. 



VIXEYARD DESTRUCTION. 



PROGRESS OF THE DESTRUCTION OF A YLSTFERA YTXE. 



According to conditions there is a great variation in the number 

 of months or years that elapse between its original infestation by 



