The Black Rot of the Grape and Its Control. 



397 



for incubation of the fungus before characteristic spots appear. Stages 

 in the rotting of berries, froin the appearance of a spot, through the 

 bird's eye and brown rot stage to the final shriveling and blackening 

 of the berry, are shown in Fig. loo.^ 



During the early part of the season of 1907 we were able to check 

 up the correlation between rainfall and the subsequent sudden appear- 

 ance of Black Rot all over the vineyard, and also found that after July 

 12th during a period of comparative drought no new Rot appeared, 

 although spores were present in very great abundance and capable 

 of germination by actual test. 



In spite of the exceptionally dry season of 1907, Black Rot was very 

 destructive in an unsprayed vineyard of 200 acres only 2 miles from 

 the site of our operations. Our experimental work for 1908 was there- 

 fore moved to this vineyard. One of the writers was constantly on the 



Fig. 100. — Successive stages of Black Rot lesions on berries. A berry passes 

 through these stages in three or four days 



ground after June ist. Besides continuing studies on the life history 

 of the fungus, careful watch was kept on local weather conditions, for 

 we were firmly convinced that in order to be effective, spray must be 

 applied to the actively growing parts before the rains came. It seemed 

 apparent from earlier observations, as well as the experience of other 

 investigators, that spray mixture properly made and properly applied, 

 if given an hour or more to "set," will prevent the entrance of fungi 

 even after a continued rain of 24 hours or more. If then from a study 

 of the available weather data and of local conditions we could predict 

 with some degree of certainty the storm periods and make a thorough 

 application of spray one to three days before these came, we should be 

 able to prevent the Rot entirely. 



How well we succeeded in our predictions maybe seen by a comparison 

 of the dates on which we sprayed and the meteorological data on another 

 page. It will be noticed that the spraying of June nth followed the 

 rains of June 9th. In this connection it should be stated that all things 

 were in readiness to begin spraying on the morning of June 9th and 

 by 4 p. m. (the time of beginning of precipitation) the whole plat would 



^ Bulletin 253 " The Black Rot of the Grape and Its Control," containing a more 

 detailed account of the fungus and illustrations of the fruiting parts, is still avail- 

 able and may be obtained by applying to the College of Agriculture, Ithaca, N. Y. 



