THE RAISIN INDUSTRY. 97 



mature, and in bad cases no part of the canes mature, but at the 

 advent of the rain turn black and die. Late in the fall the tips of the 

 green canes turn black, dry up and snap off like glass when touched. 

 The pith turns in the older canes dark brown, dries up prematurely and 

 dies, while in very young canes the pith remains watery like a semi- 

 transparent jelly. 



Many vines have no mature wood when the leaves have fallen in the 

 autumn, while others again have some. While the spotted leaves may 

 appear all over the vineyard, the diseased canes appear on vines in 

 spots, these spots in the vineyard growing larger year after year. 

 A dead vine may be seen in the midst of healthy ones, while a healthy 

 vine, on the other hand, may remain in the midst of dead ones. It takes 

 generally several years to kill the vines, and some varieties are hardier 

 than others. Some Muscats .may succumb in one year, while some 

 will last for three years or more. The roots remain alive and healthy 

 longer than any other part, and, when the top of the vine has already 

 died, it is common to see the root send up a healthy sucker, which, 

 however, in its turn, will become diseased -and die. It is likely that 

 the vines in some districts will suffer more than in others, and in places 

 the vines may not become seriously injured by the disease. 



The berries on badly diseased vines do not develop, but shrivel up 

 or remain sour, and in some cases dry up entirely. In others, again, 

 they acquire a mawkish taste, lose flavor and sweetness, and make 

 only inferior or bad raisins. These many different characteristics of 

 the plague depend evidently on the stage of infection. They do not 

 follow each other in any certain succession, nor do they all appear on 

 the same vine. Some vines show one face of the disease, other vines 

 show another, and the observer must have been previously acquainted 

 with the disease before he can readily recognize it. 



Nature and Cause. The cause of the vine plague is not known. 

 No deadly fungus has so far been found on the vine, nor has any other 

 deadly parasite been found on the diseased vines. In California the vine 

 plague has been studied by N. B. Pierce, of the Agricultural Depart- 

 ment at Washington. He suggested once that the disease was of 

 bacterial nature, but has not proved his theory, his investigations not 

 yet being finished. Mr. K. Dowlen has also been investigating this 

 disease, and at one time thought it caused by a fungus, which, how- 

 ever, was proved later by Dr. H. W. Harkness to belong to the non- 

 injurious kind. No insects of any kind prey on the vines in sufficient 

 numbers to cause the serious symptoms of the vine plague.* Whatever 

 may be the true cause of the vine plague, certain it is that it resembles 

 in its advent and spreading such diseases in men as cholera, yellow 

 fever or the Oriental plague. The vine plague appears to be especially 

 promoted by warm, moist air and rain, but it is not confined to damp 

 places, nor has it as yet been ascertained in what relation it stands to 

 locality and climate. 



*The most interesting and correct account of the vine plague yet published is 

 found in an essay on "The Mysterious Vine Disease," by Newton B. Pierce, read 

 before the State Horticultural Convention, at Los Angeles, March, 1890, and pub- 

 lished in CALIFORNIA A JOURNAL OF RURAL INDUSTRY, May 10, 1890 ; Vol. 3, 

 No. 1 8. 



