92 QUIKCE CULTURE. 



parts, as shown in the cut. The destruction of affected 

 leaves is recommended, especially as many of them are 

 also affected with both of these fungi together. 



5. LEAF MILDEW (Podosphcera tridactyla, Wall). 

 This disease consists of a parasitic white mildew spread- 

 ing interlacing filaments over both surfaces of the leaves, 

 but developed most perfectly on the upper side. The 

 disease appears in June, producing a multitude of color- 

 less spores, which spread the fungus rapidly to other 

 leaves and trees. Late in July it produces its fruit 



Fig. 65. LEAVES AFFECTED BY THE HENDERSONIA CTDONIA. 



as so many dust-like dots of regular form and size. 

 These round, dust-like specks are the sacks which 

 contain the resting spores, which withstand the rigors of 

 winter, and reproduce the leaf mildew the next year. It 

 is most thrifty on the leaves of a vigorous tree ; but, 

 with the favor of shade, may thrive on a weakly tree. It 

 is also found on the leaves of apple trees, and proves very 

 injurious to cherry leaves, often causing them to fall 

 prematurely. Sulphur dusted on the leaves when they 

 are wet is recommended as a remedy. 



