REPORT OP COMMITTEE ox PUBLICATION 119 



termined by the writers nor apparently by anyone else. It is not even 

 known how long a time is required for conidia to germinate under field 

 conditions, nor what degree of moisture is most favorable for their germi- 

 nation. The mildews are sometimes regarded as dry weather diseases, 

 although the experience of Blodgett : i in hop yards seems definitely to corre- 

 late infection of the hop mildew fungus with periods of rainfall. Admittedly 

 there are here some interesting points in the life-cycle of the Uncinula which 

 need investigation. The first spots of mildew appear promiscuously on the 

 green parts. Secondary infections occur in rapid succession and in a sur- 

 prisingly short time leaves can be found that are entirely overrun with the 

 fungus. Berries here and there begin to show the dwarfing effect of mildew. 

 But the point where the fungus seems to spread most rapidly is on the 

 peduncles and pedicles. By harvest time, in early October, the peduncles 

 are dwarfed and withered, the berries of some of the clusters frequently 

 have a grayish, powdery appearance and the foliage may appear almost 

 white from the abundance of conidia. By this time perithecia are exceedingly 

 abundant on the peduncles and on the older spots on the leaves. 



A canvas of fifty men, average or better than average vineyardists, 

 made in 1914 elicted the fact that mildew is not regarded by growers as of 

 any particular consequence, and that in their opinion the amount of damage 

 is negligible or very slight. Unfortunately the grower rarely if ever sees his 

 baskets of fruit after they have been subjected to shipment and carting. 

 In all probability he would disclaim his package and charge fraud if he 

 were to see his fruit as it is offered for sale two weeks later by the retail 

 grocer. In cases of severe infestation the peduncles are commonly withered 

 and black and as high as 50 per cent of the berries may have shelled. The 

 percentage of shelling from healthy clusters treated similarly is relatively 

 small. 



So far as basket grapes are concerned, therefore, the mildew disease 

 does not appeal to the average grower as a disease worth fighting. The 

 springing up of unfermented grape juice and grape product factories, how- 

 ever, lately has brought a stimulus for the production of a better quality of 

 fruit. This stimulus is largely from the very high standard of quality de- 

 manded by some of the largest consumers. 



Control. 



Since the margin of profit on grapes is not very great, all of the above 

 factors enter into consideration in planning a system of mildew control that 

 will be accepted and put into practice by grape growers. That the mildew 

 is relatively easy to control is attested by the fact that the disease is usually 

 dismissed by compilers of information with the statement that treatments 

 for black rot and downy mildew will serve to hold this disease in check. That 

 the disease commonly is not controlled is attested by the conditions in the 

 largest grape section east of the Rocky Mountains as presented above and 

 by the examination of a few packages of Concord grapes on any of the 

 large markets. 



3 Blodgett, F. M. Further studies on the spread and control of hop 

 mildew. New York (Geneva) Agr. Exp. Sta. Bui. 395.41-43. 



