-^ 
LIBR.AR 
RECEIV 
UNITED STATES DEPARTMENT OF AGRICULTI 
DEPARTMENT BULLETIN No. 1484 
Washington, D. C. 
June, 1927 
FACTORS INFLUENCING THE SEVERITY OF THE CRAZY-TOP DISORDER 
OF COTTON 
By C. J. King, Associate Agronomist, and H. F. Loomis, Assistant Agronomist, 
Office of Cotton, Rubber, and Other Tropical Plants, Bureau of Plant Industry 
CONTENTS 
Page 
History and distribution .. . 1 
Relation of stress conditions 3 
Persistence of the disease in certain soil areas. 4 
Spot occurrence of the disorder.. 5 
Relation of soil permeability to character and 
incidence of the disorder 7 
Slope of land and distribution of soil moisture. 8 
Root development of aberrant plants 10 
Page 
Relation of crop sequence to prevalence and 
severity of the disorder 12 
Recovery of deranged plants... 17 
Inoculation experiments 18 
Practicability of prevention or control 18 
Summary ._ 19 
Literature cited 20 
HISTORY AND DISTRIBUTION 
An abnormal type of growth or a disorder of cotton plants began 
to receive notice in the Salt River Valley of Arizona in 1919. A small 
spot of affected plants in a field of Pima cotton near Scottsdale, 
Ariz., attracted the attention of one of the writers, the Maricopa 
County agricultural agent, and a party of two or three cotton growers 
while on a cotton-inspection trip in August of that year. The owner 
of the field reported that he had observed a few abnormal plants in 
the same spot in 1918. So far as is known, this was the first appearance 
of the disorder in Arizona. During the season of 1919 a special survey 
of the cotton acreage in the Salt River Valley was made by one of 
the writers in connection with root-rot investigations, but no evidence 
of the new disease was noted in any other field. Little attention was 
given to the disease until 1922, when it was observed in several new 
districts and its damaging effects were noticed by the growers. In 
making inquiries of growers as to whether or not the new disorder 
had appeared in their fields, the county agricultural agent and the 
writers made use of the term "crazy-top" to describe the character- 
istic features of the affected plants, which usually develop the great- 
est abnormalities of branching and fruiting in the upper parts. 
This term has been adopted generally by the growers for designating 
the disease. 
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