CHERRY DISEASES 179 
from the hyphe and penetrate the outer cells of the leaf or 
twig. As development of the fungus proceeds, conidiophores 
grow erect and bear chains of conidia. These spores in mass 
give the powdery aspect to the lesions. At maturity the conidia 
are carried by the wind to other leaves and twigs, where new 
infections are initiated. Later in the summer perithecia begin 
to develop. These are yellowish at first, later brownish, and 
finally black. When mature, each perithecium contains a 
single ascus, which contains eight ascospores. 
Control. 
The application of some standard fungicide is an efficient 
remedy for powdery-mildew of the cherry. It is recommended 
that the orchard be sprayed with bordeaux mixture, or sulfur 
dust, making the first application as soon as the disease Appears. 
Repeat the application ten days later, if necessary. Sulfur 
dust may also be used with good success in the orchard. Sulfur 
is preferable in the nursery. Lime-sulfur 1 to 50 applied as 
directed for the orchard has proved satisfactory. Add 3 pounds 
of iron-sulfate to each 50 gallons of the spray mixture; this 
procedure increases adhesiveness and decreases the caustic 
qualities of the fungicide. Sulfur dust 90 parts, and powdered 
lead 10 parts, has proved satisfactory and effective, and may be 
substituted for lime-sulfur solution. Applications subsequent 
to the first may number two to four, depending on the severity 
of the disease. As a rule the schedule for the control of cherry 
leaf-blight keeps mildew under control (see page 175). 
REFERENCES 
Stewart, V. B. Some important leaf diseases of nursery stock. 
Powdery mildew of cherry. Cornell Univ. Agr. Exp. Sta. Bul. 
358 : 192-194. 1915. 
Galloway, B. T. The powdery mildew of the cherry. U. S. Agr. 
Comm. Rept. 1888 : 352-357. 1889. 
Hein, W. H. Two prevalent cherry diseases. Powdery mildew. 
‘Nebraska Insect Pest and Pl. Dis. Bur. Bot. Div. Cire. 2:1-2. 
1908. ; 
