Group Title: Press bulletin
Title: Smoky fungus of oranges
Full Citation
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 Material Information
Title: Smoky fungus of oranges
Alternate Title: Press bulletin 123 ; Florida Agricultural Experiment Station
Physical Description: 1 leaf : ; 21 cm.
Language: English
Creator: Fawcett, H. S ( Howard Samuel ), b. 1877
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville, Fla.
Publication Date: September 19, 1909
Subject: Oranges -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by H.S. Fawcett.
General Note: Caption title.
General Note: "September 18, 1909."
 Record Information
Bibliographic ID: UF00090484
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 82470156

Full Text

Florlda AgrIcullural Experimncn Sltallo

Soon after oranges attain their normal color in the fall, a faint smokiness
is often noticed on fruit that is otherwise bright and smooth. This smoky ap-
pearance may be mistaken for an accumulation of dust particles; but, on ex-
amination under a lens, it is found to be due to a network of dark-colored
fungus threads. This fungus was noticed by H. H. Hume, under the name of
Leptothyrium pomi. Although the smoky fungus appears to do no injury to the
orange itself, yet it impairs its bright color, and thereby lessens its market
value. This smoky appearance should not be confused with the more conspic-
uous black covering due to the sooty mold of whitefly-infested trees. The
smoky fungus occurs in blotches or patches of various sizes, and in some cases
covers the entire fruit. The fungus threads appear to be entirely superficial,
and apparently do not even injure the epidermis of the fruit. This is shown
by the fact that the bright color of the orange can be restored by rubbing or
This smokiness, though not a serious trouble, can readily be prevented, if
perfectly bright fruit is desired. While conducting a series of spraying ex-
periments for another trouble last year, it was noticed that the oranges were
freed from smoky fungus. It was found that the smoky fungus could easily
be controlled by spraying with Bordeaux mixture during October.
It is a well-established fact that to spray an orange tree thoroughly within
and without with Bordeaux mixture, is almost sure to invite an increase of
scale insects on twigs, leaves, and fruit. The reason for this is that Bor-
deaux mixture kills the fungi that are parasites of the scale insects, and so
allows these scales to multiply very rapidly. It was found that by spraying
only once, about October, the smokiness was avoided, and there was not
enough time for the scale insects to increase sufficiently to injure the appear-
ance of the fruit before the shipping season. In spraying for this purpose,
care should be taken to apply the spray, as far as can be done, only to the
fruit. It should be kept as much as possible from the limbs or trunks. On
the large limbs and trunks there will be left a sufficient amount of the scale
fungi to spread out on the rest of the tree and keep down the scales. For
preventing smokiness therefore, spray the fruit in October with Bordeaux
mixture, or with ammoniacal solution of copper carbonate. Bulletin 76 of the
Florida Experiment Station contains directions for the preparation of these

State papers please copy.


September 18, 1909

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