118 INTERNATIONAL CONGRESS OP VITICULTURE 



the New York Agricultural Experiment Station to investigate the cause of 

 the decline in the grape industry in Chautauqua County. 



The geology, physical geography and meteorology of the "grape belt" 

 are presented by Tarr,i and it is easy to see from his account why it is that 

 this "belt" is so admirably adapted to grape culture. While the meteorologi- 

 cal conditions can be described, it is really necessary to undertake infec- 

 tion work under vineyard conditions to fully appreciate the dryness of 

 the atmosphere and the fact that there is a constant air current in one 

 direction or another. One of the writers (R.) has expressed the opinions 

 that the two most destructive fungous diseases of the grape, downy mildew 

 and black rot, are held in check by an unusual combination of meteorologi- 

 cal conditions. At any rate it is a remarkable circumstance that neither 

 of these diseases has ever seriously menaced the Chautauqua belt, although 

 both have occurred in certain vineyards to a certain extent. It is noticeable 

 that the vineyards in which black rot has occurred are in small depressed 

 areas having poor air drainage, or in vineyards far up or over the ridge, 

 left by the sudden lowering of the lake level during glacial recession, and 

 that downy mildew does occur generally, although as a rule to a limited 

 extent, on such susceptible varieties as Delaware and certain of the Rogers 

 Hybrids, notably Agawam and Lindley. This freedom from disease may be 

 attributed in part to the resistance of the variety Concord which com- 

 prises perhaps 99 per cent of the total acreage, but varietal resistance can 

 be only a partial explanation for, in other sections of the State, this variety 

 may suffer severely although never so severely as the varieties just men- 

 tioned. 



So far as these diseases are concerned, therefore, there is no object 

 in applying a fungicide to the vineyards. At a conservative estimate not 

 one-tenth of the vineyardists in the Chautauqua belt own a spraying outfit 

 of any description, and scarcely half of those could be operated if there 

 were a desire to do so. The grape root-worm (Fidia viticida) exists through- 

 out the belt and the sprayers in use are employed in fighting this insect. 

 The time for effective application against this pest is near the first of July. 

 If two applications of poison are made the second treatment is rarely applied 

 later than July 15th. 



The Mildew. 



In the French vineyards, as is well known, the powdery mildew, caused 

 by Uncinula necator, is likely to be very serious at blossoming time. In 

 the Chautauqua belt, on the other hand, mildew rarely appears before the 

 middle or end of July, and sometimes even a trace of it can not be found 

 before mid-August. 



It is at about this time of year that heavy dew forms at night. Whether 

 the occurrence of dew has anything to do with the appearance of mildew 

 is not known. The method of hibernation of the fungus is not definitely 

 known although it is assumed to be by means of ascospores in perithecia. 

 The conditions for infection by ascospores and conidia have not been de- 



1 Tarr, R. S. Geological history of the Chautauqua grape belt. Cornell 

 Univ. Agr. Exp. Sta. Bui. 109:121. 



2 Reddick, Donald. The black rot disease of grapes. Cornell Univ. Agr. 

 Exp. Sta. Bui. 293:342-345. 



