376 MANUAL OF FRUIT DISEASES 
and to a superabundance of moisture in the atmosphere at the 
time the fruit was forming. The real cause of plum-pockets was 
discovered in 1861. 
The parasite spends the winter as mycelium in the smaller 
branches, as evidenced by the fact that it is found there before 
diseased fruit appears. Moreover, the annual recurrence of the 
disease strengthens this opinion. From the affected branches 
the mycelium grows out into the young ovaries of the fruit, 
stimulating them to form a remarkable hypertrophy. After 
the mycelium develops to a considerable degree internally, the 
threads pass towards the surface. Some of the hyphe push up 
between the epidermal cells and spread out between these and 
the cuticle. Here they form a net-work of short cells, which 
soon grow erect on the surface of the fruit and become asci 
with ascospores. The ascospores are discharged through the 
apex of the ascus, but their further history is unknown. Condi- 
tions favorable to plum-pockets are similar to those favoring 
peach leaf-curl, namely cool, wet weather in the early season of 
the year. ; 
Control. 
Satisfactory control measures have not been established for 
all sections of the country. It is advised that severe pruning 
to remove diseased twigs be practiced. It has been found in 
Montana that trees sprayed with lime-sulfur showed very few 
diseased plums, whereas more than half of the fruit on un- 
sprayed trees was destroyed. These results were obtained in 
1915 by making two applications as follows: (1) just before 
the flower-buds open, and (2) just after the petals fall. This 
treatment is advised for other regions where the disease is 
troublesome. 
REFERENCES 
Galloway, B.T. Plum pockets. U.S. Agr. Comm. Rept. 1888 : 366- 
369. 1889. 
Hesler, Lex R. Diseases of the plum. Plum pockets. Jn The Fruit 
