2 DEPARTMENT CIRCULAR 409, U. S. DEPT. OF AGRICULTURE 
keeping the fruit surface from remaining moist for any prolonged 
period, and by lowering the temperature during shipping and stor- 
age to retard the development of the rot, or by treating during 
packing with a protective antiseptic wash, such as a solution of 
borax. 
The more common cause of stem-end rot is the Phomopsis stage 
of Diaporthe citri Wolf, which also produces the melanose blemish 
of the young fruit. The less common cause of stem-end rot is per- 
haps two or more species or strains of Diplodia which have been 
included rather indiscriminately under the name Diplodia natalensis. 
Both Phomopsis and Diplodia infest dead twigs in citrus trees and 
produce spores abundantly in these twigs. The spores seem to infect 
first some portion of the stem button while the fruit is on the tree, 
and advance into the fruit proper usually after picking. Both 
types of stem-end rot develop independently of injuries, are more 
serious in marketing than in the groves, and are very irregular in 
the time required for rot to develop after picking. ‘They can be 
more or less effectively reduced by pruning out deadwood to reduce 
the source of infection, by spraying with an effective fungicide, by 
proper removal of the stem buttons immediately after picking (to 
prevent infection), by lowering the temperature during shipping 
and storage (to retard development of the rot), by treating the 
fruit with a solution of borax during packing, and by speeding up 
the marketing to insure consumption before development of con- 
siderable rot. 
Blue-mold rot, because of its comparatively rapid development, 
is often apparent while the fruit is being packed or when it arrives 
at destination. The two stem-end rots may not develop until the 
fruit has passed through the intermediate channels of trade and 
reached the retailer or the consumer. The relative possible amounts 
of these three rots in carefully handled seedling oranges held at 70° 
F. may be judged from the experimental data hereinafter reported. 
(See fig. 3.) The high temperatures prevailing in early fall and 
late spring favor stem-end rot, especially the Diplodia type. Most 
of the Florida citrus fruit is shipped between Thanksgiving and 
Easter, when temperature conditions are more favorable for blue- 
mold and the Phomopsis form of stem-end rot. 
A minor proportion of rot may be produced by miscellaneous 
fungi belonging to such genera as Colletotrichum, Gloeosporium, 
Alternaria, Fusarium, Rhizopus, Aspergillus, and Oospora. Most 
of these attack fruit that is reaching a condition of advanced decline 
or has been subjected to unusual conditions. Under ordinary condi- 
tions they are seldom of any great economic importance. 
Most of the control measures for the major rots of Florida citrus 
fruits are applied after the removal from the tree. As a rule the 
grower of the fruit does not directly attend to the picking, packing, 
and shipping, but leaves these operations to the commercial packing 
houses. His responsibility for producing fruit of good keeping 
quality is restricted largely to the adoption of proper cultural and 
fertilizing practices for the production of good fruit and to the 
practice, when practicable, of two of the special control measures 
mentioned above, namely, the pruning out of deadwood and the 
spraying with an effective fungicide. 
