28 
Colorado 1i1xi*ekjment Station 
and sevei'ity of this disease in the state are not known. It is, however, 
one of the most serious diseases of the apple in the eastern states 
and will very probably become of greater importance in Colorado. 
Bitter rot attacks the fruit and twigs but is not known to occur 
on the leaves. It begins on the fruit as small light brown spots 
which rapidly enlarge finally involving the entire fruit. Small 
black spots soon appear on the surface of the larger spots. These 
are the fruiting bodies (pycnidia) of the fungus and soon break 
through the epidermis and free their spores in small pink masses. 
These spores are scattered about by Avind and rain, causing secondary 
Bitter rot of apple. (After Carman.) 
infection. Cankers are developed on the tAvigs, small limbs and fruit 
spurs. Large branches are seldom affected. The dead bark is 
cracked and roughened. 
The lime sulfur spray is not effective for bitter rot. All in- 
fected tAvigs vshould be carefully cut out and Bordeaux (4-4-50) 
should be applied just before the buds open and again tAvo or three 
weeks later." 
Powdery Mildew (Podosphaera leucotricha) (12) — Nursery stock 
where ever apples are grown suffer more or less from powdery mil- 
dew. Both leaves and twigs are affected but the fruit is seldom 
injured. 
A white or grayish powder is produced on the leaves ; more often on 
