UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1474 
Washington, D. C. 
March, 1927 
CITRUS MELANOSE AND ITS CONTROL 
By John R. Winston, formerly Associate Pathologist, John J. Bowman and 
Walter J. Bach, Junior Pathologists, Office of Fruit Diseases, Bureau of 
Plant Industry 1 
CONTENTS 
Page 
Introduction 1 
Description of the disease 2 
Effect on leaves 2 
Effect on fruit 2 
Effect on twigs 3 
Diseases confused with melanose 3 
Ammoniation 3 
Star melanose 3 
Black melanose 3 
Rust-mite tear stain 4 
Rust-mite russet 4 
Historical review 4 
Species and varieties attacked 7 
Geographic distribution 10 
Reported occurrences 10 
Local distribution in Florida 11 
Economic importance 11 
Tree injury 13 
Fruit blemish 13 
Page 
Economic importance — Continued. 
Fruit decay 13 
The causal organism 14 
Dissemination of the causal or- 
ganism 16 
Conditions favoring infection 17 
Microscopic studies of melanose 
markings 18 
Reisolation of causal organism. _ 18 
Growth on artificial media 19 
Temperature relations 20 
Inoculation tests in groves 24 
Experiments for melanose control — 29 
Pruning for melanose control — 29 
Dusting for melanose control 32 
Spraying for melanose control— 34 
Summary 60 
Literature cited 61 
INTRODUCTION 
The purpose of this bulletin is to present the results of investiga- 
tions on citrus melanose (caused by PhoTnopsis citri Fawcett), 2 to 
stress the economic importance of the disease, and to assemble infor- 
mation on it by giying a resume of the more important published 
works on the subject. 
The studies herein recorded include: (1) The relative susceptibili- 
ties to melanose of many rutaceous plants, including citrus; (2) the 
1 The writers take pleasure in making acknowledgment to Ruth Colvin. E. Aline Fen- 
ner, Lulu O. Gaiser, and Harold H. Link, of the Office of Fruit Diseases ; to Alfred 
Warren, agricultural agent, St. Lucie County, Fla. ; and to H. E. Stevens. Fort Myers, 
Fla., formerly pathologist at the Florida experiment station, for valuable assistance 
rendered in laboratory and field work. Acknowledgment is made also of the very valuable 
cooperation by the late J. B. Magruder, Orlando. Fla., tbe owner of the grove in which 
most of the experimental spraying and dusting tests were made. 
2 After this bulletin was written the ascus stage of the melanose fungus was found 
by Frederick A. Wolf, of the Office of Fruit Diseases, and described by him as Diaporthe 
citri (Fawcett) n. n. in the Journal of Agricultural Research (25). (Italic numbers in 
parentheses in this bulletin refer to "Literature cited," p. 61.) 
24975°— 27- 
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