26 



disease so destructive in any vineyard in New England. In New 

 York state and the Lake Shoie regions, vineyards are often as seriously 

 injured as this one by this scourge. 



Mr. Andrews asks me to account for this result, notwithstanding 

 the fact that fungicides were used, and while I cannot so confidently 

 explain the cause as I might, had I been on the ground and made 

 more minute observation when this disease first began to appear, I 

 will point out some of the sources of error in the time of applica- 

 tion of the fungicides, and the conditions which favored the develop- 

 ment of this destructive disease. 



In the first place we must understand that this and most other 

 parasitic fungi grow only under conditions of moisture and liigh 

 temperature, and that tlie spores are destroyinl oithj by coming in 

 contact with the soluble co|)per solutions. Now, if at any time 

 during the early siiminer, such conditions of tcmperalure and moist- 

 ure should occur after a rain that had removed the little soluble 

 fungicide there may be in the Bordeaux mixture, the spores of the 

 disease would grow rapidly and it would take but a few days to 

 destroy all the fruit in a large vineyard. 



Such conditions did occur between the first spraying of the vines. 

 May 5th to 7Lh and June 17th. In that time there were 12 days when 

 it was cloudy or rainy and high temperature prevailed for several days 

 at a time at different intervals. 



From May 9th to 11th the temperature ranged between 79°and 85° 

 during the day time and 46° to 56° in the night. From May 20th 

 to 23d it was 70° to 75° in the day time and 57° to 58° at night. 

 From May 31st to June 4th it was 79° to 80" daring the day, and 52° 

 to 60° at night. From June 13th to 16th it ranged between 87° and 

 91^^ in the day time and between 57° and 66° at night. 



If, during any of these intervals and especially the last, there was 

 dew or moisture in small drops on the foliage, the spores would grow 

 very rapidly, for the interval between the times of application of the 

 fungicides was nearly six weeks, and even light rains in that time 

 would have removed all the fungicides. 



Then another precaution should have been taken, that of spraying 

 the vines and trellises and perhaps the ground under them, with 

 strong solutions of sulphate of copper or sulphate of iron before the 

 leaves unfolded, to destroy all spores that might have survived the 

 winter in these places. 



The 50 plum trees, mentioned in Mr. Andrews' report, produced an 



