GRAPE DISEASES 231 



In the United States it may be found in all grape-growing regions 

 except in the state of California, where the conditions are highly 

 unfavorable to it. In that state it is almost unknown, but its 

 place is taken by the powdery-mildew fungus. 



Wherever found, this disease is of great importance because 

 of the injury it produces to all of the parts above ground. 

 There may result serious loss by the reduction in the amount of 

 fruit ; and the leaves may be spotted to such an extent that they 

 die. The very general range of the trouble makes it a constant 

 foe, especially wherever susceptible varieties occur. All au- 

 thorities are agreed that black-rot is the most serious fungous 

 disease with which grape-growers generally have to contend. 

 The amount of loss occurring each year varies with the season, 

 there being an abundance of it in wet seasons and much less in 

 dry ones. The disease is more troublesome in warm, humid 

 regions than cool, dry ones. In North Carolina the heavy losses 

 come within a week after blossoming-time, while in New York 

 the greatest injury is incurred when the berry is one-half to 

 two-thirds grown. In many sections of the country the de- 

 structive nature of this disease has been responsible for the 

 abandonment of grape-growing. In 1906 Michigan vine- 

 yardists lost 30 to 40 per cent of their crops on account of black- 

 rot ; in Ohio in 1905 the loss is put at 30 per cent of the crop, 

 meaning a loss of $28,500. The losses in many regions are 

 practically total; this has been true in several states. A 

 case is on record for 1906 where a large vineyard of 200 acres 

 in New York did not yield enough grapes to pay for operating- 

 expenses ; the reduced yield here was due to the action of the 

 black-rot pathogene. 



As a rule all the green parts of the vine may be affected with 

 black-rot. The old portions and the fruit of rotundifolia 

 varieties, like the Scuppernong, in southern United States are 

 rarely attacked. 



