PEAR DISEASES 349 
The twigs, petioles and leaf-scales also exhibit signs of the 
disease similar to those on the foliage. The lesions on the 
twigs, however, are more elongated and become depressed, 
and finally girdling results. 
Cause. 
The leaf-blight disease is caused by afungus, Fabrea maculata. 
Throughout the summer its conidia, developed upon the leaves, 
fruits and twigs, are scattered to other leaves, where infec- 
tion results. It may be that certain of these conidia pass the 
winter on diseased twigs, producing infections the following 
spring. The chief method of hibernation, however, is by means 
of apothecial bodies in fallen leaves. Infected leaves, either 
at maturity or prematurity, fall to the ground in the late 
summer or autumn, carrying the fungus with them. Further 
activities on the part of the pathogene in these old leaves 
result in the formation of apothecia. In the spring, ascospores 
are discharged from these fruiting structures, and are carried 
to the susceptible parts. About one week later, the effects 
of the work of the parasite within the tissues are visible to the 
naked eye; and within a month, or less, after the ascospores 
are discharged, a new crop of spores, conidia, is developed. 
These conidia are borne in acervuli which are to be found in 
the center of each spot. Conidia from this source may infect 
the quince; likewise, the conidia from the quince may infect 
the pear. This is an adaptation on the part of the fungus 
which renders its control more difficult. Furthermore, these 
conidia may infect the hawthorn, apple and other closely 
related plants, thus adding complications to the application of 
remedial measures. All these plants, the quince, the apple and 
others, must be regarded as a source of trouble to the pears. 
Control. 
For the orchard trees and pear stocks, spraying is profitable 
and effective. Lime-sulfur 1 to 50 may be used with safety 
and with success. It is recommended that iron-sulfate be 
