348 



MANUAL OF FRUIT DISEASES 



been the subject of horticultural writings and discussions for 

 many years. Very recently it was found on pears in Australia. 

 As already indicated, the disease is found more commonly 

 in nurseries than in orchards, yet the latter are not exempt 

 from attacks of the leaf-blight pathogene. In the nursery 

 the trouble affects the leaves and twigs of seedlings ; in the 

 orchard, the fruits (Fig. 98), in addition, are susceptible. It 



appears that all varieties show 

 the disease, yet the Kieffer and 

 Angouleme are more resistant 

 than the Seckel, Wilder Early and 

 Sheldon. It has also been ob- 

 served that the Flemish, Lawrence, 

 Bosc and Clapp Favorite are 

 resistant. 

 Symptoms. 



The disease makes its appear- 

 ance early in the spring soon 

 after the leaves develop. There 

 develops a small circular, carmine- 

 red spot, first on the upper, and 

 then penetrating to the lower, sur- 

 face. The color soon changes from 

 red to dark-brown, with a slightly 

 elevated, minute black spot in the 

 center. If the lesions are numer- 

 ous, they may merge, and thus the tissue between them turns 

 brown. Affected young leaves shrivel; older ones change 

 only in color. Badly diseased leaves turn yellow and fall 

 prematurely. 



The fruit shows the same carmine-red spot which afterward 

 assumes a darker color (Fig. 98). The skin is roughened, and 

 the growth of the epidermis is hindered, causing a deep crack 

 in the flesh. 



FIG. 98. Leaf-blight lesions 

 on pear-fruit. 



