2 BULLETIN 368, U. S. DEPARTMENT OF AGRICULTURE. 
A microscopic examination of the blighting- blossoms showed them to be infected 
with the ordinary brown-rot fungus, which for the present may be designated by the 
name Sclerotinia cinerea. The specimens showed that the conidial or “ Monilia’’ form 
of the fungus had attacked the bloom in various stages, killing some of the buds before 
they had opened, often penetrating the entire flower and extending down the pedicels. 
Some of the blossoms had set their fruit, and the young prune had started to develop 
before the flower was completely killed. In some cases the young fruits were pene- 
trated; in others they were not yet occupied by the fungus, which had partly killed 
the flower and spread down the pedicel. The conidial form of the fungus was fruiting 
abundantly over most of the surface of the diseased organs. 
An extended correspondence was carried on with the growers during the spring and 
summer of 1914, in which it was developed that the prunes in that section had been 
dropping quite badly for several years from causes unknown to the orchardists; that 
rather cool, rainy weather occurred during blossoming time in 1914—not severe, heavy 
rains, but continuous damp weather. The prunes “made a good setting, but imme- 
diately seemed to stop their growth, and the ‘husk’ gradually dried and adhered to © 
the prune, finally all falling off.’’ Naturally, the possibility of control of the fungous 
trouble by early spraying was suggested in the correspondence. 
- Notwithstanding this very definite evidence that the specimens of prune blossoms 
received were killed by the brown-rot fungus, it was suggested as not safe to at once 
conclude that the whole trouble of nonsetting of prunes was due to this fungus, since 
the same rainy weather which would favor the brown-rot fungus would also interfere 
with the pollination and fertilization of the fruit. Nutrition factors and general tem- 
perature conditions would also be concerned in the problem of prune dropping. It 
seemed hardly probable that the brown-rot fungus could be charged with all the diffi- 
culties, including those of the Sacramento and Santa Clara Valleys in California. 
Subsequently, from specimens of partly ripe cherries received from Mr. A. W. 
Moody, of Vancouver, Wash., with a letter dated July 11, 1914, a serious trouble with 
the ripening cherries was also identified as caused by the brown-rot fungus. 
The brown-rot fungus is well known to be widely distributed on the Pacific coastin ~ 
the more humid sections near the ocean. It has been studied and figured by the 
pathologists of California and Oregon, but always on the ripening fruit. The writer 
saw it on ripe prunes at Vancouver, Wash., in September, 1907, in the district from 
which these specimens came. The blossom-blight phase of this disease appears not 
to have attracted attention as a disease of prunes and other stone fruits on the Pacific 
coast. 
BLOSSOM INFECTION OF PRUNES. 
Blossom infection of brown-rot on cherries in New York was 
reported by Arthur? as early as 1885, and a blossom blight of peaches 
in Delaware was described by Smith? a few years later. 
In the summer of 1913 the junior writer obtained information in 
regard to a peculiar and severe early drop of prunes in Clarke County, 
Wash., the effects reported being very similar to those of the Monilia 
blossom blight of the peach as he had observed it in the East. The 
following summer he made a visit to the section mentioned to study 
the prune situation. The data collected showed that the prune 
orchards had again suffered from a severe blossom blight and that the 
1 Arthur, J. C. Rotting of cherries and plums, In N. Y. State Agr. Exp. Sta.,4th Ann. Rpt., 1885, 
p. 280-285. 1886. 
aSmith, Erwin F. Peach rot and peach blight. In Jour. Mycol., vol. 5, no. 3, p. 123-134. 1889. 
Peach blight. Jn Jour. Mycol. v.7,no. 1, p. 36-38, 2 pl. 1891. 
