UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 531 
>#• _ .. - ... .... -9 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
J\J9"^3L 
Washington, D. C. 
PROFESSIONAL PAPER 
May 28, 1917 
RHIZOPUS ROT OF STRAWBERRIES IN TRANSIT. 
By Nell E. Stevens, Pathologist, and R. B. Wilcox, Scientific Assistant, 
Fruit-Disease Investigations. 
CONTENTS. 
Page. 
Introduction 1 
Causes of decay in transit 2 
Conditions of transportation 2 
Condition of fruit 2 
Fungi 4 
Rhizopus nigricans 4 
Physiology of Rhizopus nigricans 7 
Character of the rot produced 7 
Humidity relations 7 
Temperature relations 7 
Host relations 9 
Occurrence on other plants 9 
Page. 
Present shipping practices 11 
Sources of infection by Rhizopus nigricans. . 13 
Infection in the field 13 
Unsanitary conditions usually prevailing 
in the packing house 14 
The bruising of berries in packing 14 
Direct sources of infection 15 
Washing berries 15 
Drying berries after washing 16 
Summary 19 
Literature cited 21 
INTRODUCTION. 
The increased production of strawberries in the Southern States 
has resulted in large shipments to northern markets. These ship- 
ments have been attended by great losses, due to the decay of the 
fruit in transit and on the market. In the hope of obtaining infor- 
mation which will assist in reducing this large annual loss, Dr. C. L. 
Shear and the writers began, in 1915, a study of the organisms and 
conditions causing decay of strawberries after picking. 
This study has included field observations in the principal straw- 
berry-growing regions of Florida, Louisiana, North Carolina, Vir- 
ginia, Maryland, and Delaware ; observations in the markets of Bos- 
ton, New York, Philadelphia, and Chicago; laboratory studies of 
the organisms causing strawberry rot; and experimental shipments 
from points in Florida and Louisiana. 1 These shipments were 
1 Through the cooperation of Mr. George M. Darrow," of the Office of Horticultural and 
Pomological Investigations of the Bureau of Plant Industry, the writers have received 
strawberries from points in Alabama, Louisiana, Texas, and other States at times when 
it was impossible for them to visit these regions. The writers are also indebted to 
numerous fruit growers and shippers, especially in the central Florida region, for 
assistance. 
Note. — This paper is of interest to botanists, pathologists, and strawberry growers and shippers, 
especially in the Southern States. 
80315°— Bull. 531—17 
