2 BULLETIIS" 368, U. S. DEPABTMENT OP AGEICULTUEE. 



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 prime 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. 

 ivloody, 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 coast in 

 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 ch.erries 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 stud}?- 

 the prune situation. The data collected showed that the prune 

 orchards had again suffered from a severe blossom blight and that the 



' Arthur, J. C. Rotting of chemes and plums. Jn N. Y. State Agr. Exp. Sta., 4th Ann. Rpt., 1885, 

 \,. 2S0-285. 18S6. 

 i Smith, Erwin F. Peach rot and peach blight. In Jour. Mycol. , vol. 5, no. 3 , p. 123-134. 1889. 

 Peach blight, /w Jour. Mycol. v. 7, no. 1, p. 36-38, 2 pi. 1891. 



