New York Agricultural Experiment Station. 345 



open in the spring, followed by the three sprayings that are usu- 

 ally given the trees for apple scab. Great pains should be taken 

 to see that the limbs are thoroughly protected with the mixture as 

 well as the foliage and fruit. The approximate dates of spraying 

 may be given as follows: 1. About the time the leaf-buds begin 

 to open. 2. About a week before the blossom-buds open. 3. As 

 soon as all of the blossoms have fallen. 4. Ten days or two weeks 

 after ¥o. 3. 



INVESTIGATIONS IN 1899. 



It was originally planned that this season's work should be a 

 verification of the j^revious year's results, namely, the identifica- 

 tion of the canker fungus and the determination of its relation to 

 what was thought to be the same species that occurs on pear and 

 quince trees and on the fruit of all three species of trees. But the 

 work broadened as Sphaeropses were found on a variety of hosts 

 representing seven orders of plants. 



Since a knowledge of the host plants of any plant disease is of 

 great practical value in order that it may be successfully com- 

 bated, an attempt was made to determine the relation of the 

 species of Sphaeropsis, represented by tlie different hosts, to the 

 canker fungus. 



In the spring of 1898 specimens of blighted apple-tree twigs 

 were received from Odessa, N. Y. It was not determined at the 

 time what was the cause of the blight, but a subsequent examina- 

 tion revealed the presence of numerous pycnidia containing 

 mature spores of a Sphaeropsis. On visiting the orchard late in 

 the fall, it was found that the twig blight had been quite notice- 

 able in 1897, but there was none to be found on the current sea- 

 son's growth. In all cases noticed, when once attacked, the entire 

 growth of the season had been killed and in a few instances the 

 disease had extended into the previous season's growth. There 

 were a few miniature canker spots on the smaller limbs but none 

 were noticed on the larger branches and the trees were in fairly 

 vigorous condition. 



