28 
NOTES ON PLUM CULTURE. 
ment between the two sets. The natural conclusion is that 
the infertility did not lie in the failure of the stigmas to re¬ 
ceive pollen, but must be looked for either in an inherent 
antipathy which the plant has for its own pollen or in some 
outside influences. One factor comes in here which makes 
the test unsatisfactory, and prevents drawing definite con¬ 
clusions as to the cause of the infertility, and that is the 
extent of the “June drop’’ from all parts of the trees. This 
was so great that even the trees that set full, matured but a 
light crop. The same influences acting upon the covered 
flowers would account, in part at least, for the results re¬ 
corded. Further discussion of the cause is reserved until 
additional observations suggested by the work this year can 
be made. 
INSECTS AND DISEASES. 
INSECTS. 
The insects commonly injurious to the plum, such ?s the 
Plum Gouger, Curculio and Plum Aphis are treated in bul¬ 
letin No. 47 by Prof. Gillette, and for information concern¬ 
ing them the reader is referred to that bulletin. 
FUNGUS DISEASES. 
There are several parasitic fungi reported from differ¬ 
ent parts of the country as injurious to the plum. At least 
four of these are present in Colorado, although only two 
have thus far worked to an injurious extent upon the culti¬ 
vated plums. The fungus at present doing greatest injury, 
and having widest distribution, is the Leaf-spot or Shot-hole 
fungus (Cylindrosporium Padi Karst ). It has been present 
in the station orchard for four seasons, but has been con¬ 
trolled by spraying so that no serious injury has resulted 
from it. 
The disease makes its appearance early in the summer 
or about the time the leaves reach full size. Small circular 
spots of a red or purplish color are first seen; these enlarge 
somewhat, becoming an eighth of an inch in diameter. As 
