Group Title: Press bulletin
Title: Roselle mildew
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Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00090406/00001
 Material Information
Title: Roselle mildew
Series Title: Press bulletin
Physical Description: Book
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
Publication Date: 1907
 Subjects
Subject: Roselle -- Diseases and pests -- Florida   ( lcsh )
Microsphaera -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by H.S. Fawcett.
General Note: Caption title.
General Note: "October 20, 1907."
 Record Information
Bibliographic ID: UF00090406
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 - 78196966

Full Text



PRESS BULLETIN No. 69.


Florida Agricultural Experiment Station.



ROSELLE MILDEW.

BY H. S. FAWCETT.

Roselle or Jamaica Sorrel (Hibiscus Sabdariffa) was severely at-
tacked last year by Mildew. It was noticed about the first of November.
Those who have planted roselle this year should keep on the lookout
for it. The mildew is characterized as follows: The leaves, petioles,
stems and sometimes the entire plant assume a white powdery appear-
ance as if they had been lightly dusted over with flour or lime. The ap-
pearance comes on quite suddenly. It usually follows the cool, moist
nights that are likely to occur about this time of the year. The vitality
of the plant is probably weakened by the drop in temperature, and this
renders it more susceptible to the attack of the mildew. Leaves at-
tacked by the mildew soon begin to look unhealthy, and turn slightly
yellow.
CAUSE OF THE MILDEW.'
This disease is caused by a white mould-like fungus, known scien-
tifically as a species of Microsphaera. By means of a hand lens one can
observe a network of very minute white mycelial threads on which there
are borne upright chains of small spherical spores. These spores may
be carried by the wind or insects from one plant to another, and in this
way spread the disease rapidly to great distances in a short time.
In the course of several weeks if the fungus is not killed, the powdery
appearance disappears, and on the threads are seen minute black
specks. These contain the spores that are able, like seeds, to live
through the winter months and reproduce the mildew the following year.
TREATMENT.
The treatment recommended for this disease is to spray the plants
as soon as the white appearance is noticed with potassium sulphide
(liver of sulphur), using one ounce to two gallons of water. Dissolve


October 20, 1907.






the potassium sulphide in water just before using, and in case any of ihe
solution is to be kept for later spraying, put it in a tightly corked glass
bottle. As an additional preventive for the following year all deddl
plants should be burned up after the fruit is picked, in order to kill the~
resistant spores that would otherwise live over winter on the dead leaves
and stems and infest the next year's crop.

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