2 BULLETIN 1252, U. S. DEPARTMENT OF AGRICULTURE. 
April and May, and less than 5 inches in the four months beginning 
with June and ending with September. The average monthly rain- 
fall for July and August is less than three-fourths of an inch. 
Showery weather often prevails during the blooming season for 
prunes and cherries, but this is soon followed by relatively dry 
weather that usually continues through the cherry-picking period 
and sometimes well into the prune harvest. The weather conditions 
are thus rather unfavorable for the development of brown-rot, but 
they are not extreme enough to eliminate the disease. In most years 
brown-rot attracts but little attention, but occasionally it breaks into 
a serious epidemic that causes the loss of a large percentage of the 
crop. The destructive phases of the disease have taken two forms— 
one an infection of the blossoms and the other a rotting of the fruit 
as it approaches maturity. 
BLOSSOM INFECTION. 
Blossom infection usually makes its first appearance as a browning 
or blackening of the under calyx lobes where drops of water have 
hung. In some cases it spreads down the pedicel, the fruit often 
turning back on its stem, while in others it confines itself largely to 
the petals and calyx, causing the young fruit to separate readily from 
its stem. The browned and blackened parts usually persist for a 
considerable time, furnishing a ready means of distinguishing the 
diseased blossoms from those that are yellowing from starvation or 
a lack of pollination. (PI. I, figs. 1, 2,46; Pl. II, A.) 
During the five years from 1915 to 1919, inclusive, when orchards 
were under close observation by the writers, blossom infection always 
occurred on both prunes and cherries. In each of these years counts 
of the infected and healthy blossoms were made on representative 
trees. The results are shown in Table 1. It will be seen that in 
some years the prune orchards were practically free from biossom 
infection, while in others from one-third to one-half of the young 
prunes were destroyed by brown-rot. The infection on the sweet 
cherries was even more serious than on the prunes. This subject 
will be given further consideration under headings relating to plow- 
ing, cultivation, and spraying. 
TABLE 1.—Count of blossoms infected with brown-rot on representative prune 
and cherry trees. 
Percent- Percent- 
Year. Variety and location. age Year. |' Variety and location. age 
affected. affected. 
1915 | Italian Prune, Felida, Wash..... 40 |} 1916 | Black Republican cherry, Salem, 
1916 |..... GO; df. -b pets. ca SE EELELLEE -) Trace.) Oregziirsii. £110 es 26 
Mis hy i eats See ee eae Pe 35 Napoleon cherry, Salem, Oreg.... 4 
Italian Prune, Springbrook, 1917 | Black Republican cherry, Salem, 
Oe a ds cacteenn bine’ ae. 64 One? oj daacpusp ee ts ca eee 65 
Ttalian Prune, Dundee, Oreg.... 52 Napoleon cherry, Salem, Oreg. . .. 51 
1918 | Italian Prune, Felida, Wash... Trace.} 1918 | Black Republican cherry, Salem, 
1919 | Italian Prune, Salem, Oreg...... 12 OTOP 9. aya'h<aqckc nae eee 17 
1915 | Black Republican cherry, Salem, Napoleon cherry, Salem, Oreg. ... a 
Ty AB BA Re ae 85 | 1919 oo (Oe Pere | Oe ee 
1 Less than 1 per cent. 
; 
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