214 Bulletin 253. 



and they contain great quantities of pycnospores which with another 

 rain and favorable weather produce another infection. And so it is 

 that during the entire season following every rain there is a new infection 

 which becomes evident on the berries about ten days or two weeks later. 

 If the conditions are right, the berry will be infected at any stage up to 

 the time it is ripe and ready to pick. The rot does not go from one berry 

 to another except by means of spores. 



The effect of dry weather. 



The remainder of the month of July, 1907, after the 12th, and most of 

 August was very 6xy. Very few infections took place during this period. 

 There was an enormous number of pycnospores formed in the pycnidia 

 on the rotted berries and on other parts of the vine but for want of mois- 

 ture these remained in the pycnidia, protruding slightly and forming a 

 white speck at the apex. 



With the rapid growth of the healthy berries the opening in the 

 cluster, caused by the drying up of some berries from black rot, soon fills. 

 In some cases, it is just as well that some of the berries be removed but in 

 the case of a light setting, every berry that rots represents an actual loss, 

 to say nothing of the danger of spreading the disease to other berries. 

 It very frequently happens that as much as 25% of the crop may disap- 

 pear in this way without attracting the attention of the grower. 



Preparation for winter. 



When the pycnospores are discharged from the pycnidia, the latter 

 become entirely filled with whitish cells and remain through the winter 

 in this way. In the spring these cells elongate to form the ascus, and the 

 whitish content breaks up to form the eight spores. 



Other sources of infection. 



It frequently happens that pycnospores formed on the berries in 

 the autumn have thicker walls and are not discharged from the pycnidia. 

 They lie thus through the winter and the following spring are discharged 

 and produce an infection. It also happens that the pycnospores are not 

 discharged from some of the pycnidia on the tendrils or stems. These 

 live and are capable of producing an infection. 



With the above facts in regard to the life-history of this fungus, the 

 reasons for the recommendations at the end of this bulletin will become 

 apparent. Further information in regard to any of these points will be 

 gladly furnished by addressing an inquiry to the Department of Plant 

 Pathology, New York State College of Agriculture, Ithaca, N. Y. 



