Florida Agricultural Experiment Station


In such a case a grader naturally is going to let the fruit go to
market, and the disease will become apparent later. When the
black rot has attained an advanced stage of development a promi-
nent greenish-brown to blackish spot makes its appearance at the
stylar end. At this time the core is black and the adjoining
fruit cells are beginning to break down. The pulp and juice in
close proximity to the blackened central portion of the fruit
has an unpleasant bitter taste, while the balance of the fruit is
affected but slightly.
 CAUSE OF BLACK ROT
 Black rot is caused by a fungus known as Alternaria citri Ellis
 & Pierce, the spores of which are believed to lodge in the natural
 openings of the fruit, which may be either the navel or a small
 imperfection at the stylar end in the case of other oranges. In-
 fection apparently does not take place until after the oranges
 have grown to sufficient size to distend the navel or other natural
 opening. There seems to be a direct relation between the oc-
 currence of black rot and moisture, as the disease is most prev-
 alent after periods of humid or rainy weather.

 CONTROL OF BLACK ROT
 As a rule, black rot of oranges is not of sufficient importance
 to justify special control measures. If the variety showing in-
 fection is mature the crop should be picked as soon as possible,
 for the longer the fruit remains on the trees the greater may be
 the decay. Spraying has not proved effective for the control of
 black rot in California, even where carried out at frequent in-
 tervals beginning with the blooming period.
 In the packinghouse, all oranges showing the slightest evi-
dence of black rot should be culled out, since infected fruits break
down in transit and on the market. While black rot, in itself, is
a slow decay, it usually opens the way for green and blue mold
to develop.
 STYLAR-END ROT OF TAHITI LIMES
 Cause unknown
 Tahiti limes, and sometimes also lemons, frequently develop
a firm, light-colored collapse of the rind at the stylar, or so-called
"blossom", end of the fruit. This type of rot is of frequent oc-
currence in Florida and has also been reported from Cuba and