BROWN-ROT OF PRUNES AND CHERRIES. 3 
conditions were such as to indicate that the brown-rot organism was 
“an important factor in the case. 
In the spring of 1915 the prune orchards in the vicinity of Van- 
- couver, Wash., were kept under close observation, and a record was 
made of orchard and weather conditions. March 28 and 30 were fair 
days, but with these exceptions it rained almost continuously from 
March 24 to April 8. The trees were in full bloom on March 28, and 
on April 5 the blossoms were falling. On the latter date there was no 
evidence of typical blossom blight as it usually occurs in eastern sec- 
tions, but many of the calyx cups were turning brown on the under 
side where drops of water had hung, and the margins of the sepals were 
often similarly affected. On April 8 some of the young fruit was turn- 
ing yellow and dropping, apparently from lack of fertilization of the 
blossoms. At this time the browning of the calyxes had become much 
more serious, involving in some cases more than three-fourths of the 
crop of the unsprayed trees. It was much more abundant on the 
lower than on the upper branches and seemed to be as common on 
the fertilized as on the unfertilized fruit. In some cases the brown- 
ing spread down the pedicel, the fruit often turning back on its stem; 
in others it involved most of the calyx, the young fruit separating 
readily from it. (PI. I, figs. 4, 5, and 6.) The latter condition was 
more common on the fertilized blossoms. When placed in a moist 
chamber, the affected fruit developed an abundant growth of Monilia, 
the conidial stage of Sclerotinia cinerea (Bon.) Wor.! 
On April 12 a heavy drop was taking place, both of the unfertilized 
and the fertilized but infected fruit. At this time the fertilized fruit 
could be readily distinguished from the apparently unfertilized by 
its enlarged ovary, its lengthened pedicel, and its darker green color. 
The brovwn-rot fungus produces two distinct types of spores—one, 
the Monilia or summer form, which gives the characteristic mouse- 
colored appearance to the rotting fruit; the other, the mature or 
perfect stage, in which the spores are borne on the upper surface of 
cup-shaped fruiting bodies, known as apothecia, that develop from 
the mummied prunes. 
On April 2 apothecia were evident under the trees on the diseased 
prunes of previous seasons. By April 8 they had developed in large 
numbers, 30 to 40 clusters often being found on the ground under one 
tree. (PI. I, fig. 3.) On the latter date many of the apothecia had 
shed their spores, and by April 12 they were disappearing. Most of 
the apothecia came from prunes near the surface of the soil, and while 
some had unusually long stalks none could be found coming from a 
greater depth than 3 or 4 inches. | 
_1Matheny, W. A. A comparison of the American brown-rot fungus with Sclerotinia fructigena and 
S. cinerea of Europe. In Bot. Gaz., v.56, n0. 5, p. 418-432, 6 fig. 1913. 
