NOTES ON PLUM CULTURE. 
29 
the fungus matures, the spots become dark brown, shading 
to light brown at the center. The effected tissue shrivels, 
and finally drops out, leaving circular holes. Frequently 
several spots may run together so that the holesdeft in the 
leaf are irregular in form. Under conditions favorable to 
the fungus the spots become so numerous as to destroy the 
leaves attacked, and thus check the growth of the tree, and 
prevent the development of fruit. If stocks in nursery are 
attacked the bark tightens and the stocks cannot be budded. 
The injury to orchard trees by this disease is in direct pro- 
portion to the percentage of leaves destroyed, but no mat- 
ter how slight the attack it should receive attention. The 
tree is entirely dependent upon the leaves for the elabora- 
tion of its food, and any injury to them that interferes with 
the fulfillment of this important office, checks growth and 
injures vitality. 
Various remedies have been tried and of these the Bor- 
deaux mixture gives the most general satisfaction. In our 
practice with this remedy we have made two applications; 
the first as soon as the leaves are developed, and a second 
about three weeks later. In some seasons a third and pos- 
sibly a fourth application may be necessary, as the develop- 
ment and spread of the fungus is in a measure dependent 
upon weather conditions. The appearance of leaves at- 
tacked by this fungus is shown in Plate III. 
POWDERY MILDEW OF THE PLUM AND CHERRY. 
{Poclosphcera o.vyacanthce (DC.) DBy.) 
This disease has not appeared in the station orchard, 
but has been reported to us from two counties of the state 
as injurious to both plum and cherry trees. The fungus 
works entirely on the surface of the leaves, drawing its 
nourishment from the cells by means of minute suckers 
called haustoria. Badly effected leaves appear as if dusted 
with a white powder and this suggested the common name. 
Being on the surface the fungus is easily reached by any of 
the fungicides in common use. Phnely powdered sulphur, 
which has been successfully used in combatting the closely 
related Powdery Mildew of the Grape, would probably be 
equally effective in destroying this parasite. The fungus 
does not usually appear until late in summer; our specimens 
were received the last week in August. 
