Bulletin 229, Diseases of Citrus in Florida


or other injuries, apparently even more readily than the Pho-
mopsis decay. As the entire fruit is involved, it becomes dark
olive green to blackish brown, this color starting around the
stem end and then spreading over the entire surface. An un-
usual form of Diplodia stem-end rot was observed in oranges
that were artificially colored during the fall of 1928. This start-


Fig. 56.--Sectional view of grapefruit illustrated in Fig. 55, showing how
 Phomopsis stem-end rot has progressed more rapidly down the core
 and has spread through the lower end.
ed as soft, watery spots near the button, the spots in more ad-
vanced stages being grouped into a ring, or suggested ring, of
soft, watery decaying tissue about an inch in diameter, leaving
the buttons supported on an island of temporarily sound rind.
 CAUSE OF STEM-END ROT
 Stem-end rot of Florida citrus fruits may be caused by either
of two fungi. The more common cause is Phomopsis citri Faw-
cett, which also causes melanose. The less common cause is
Diplodia natalensis Evans, or a species closely related. Both of
these stem-end rot fungi flourish and develop spores abundantly


'AL