UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No, 756 4 
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Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
January 29, 1919 
PECAN ROSETTE IN RELATION TO SOIL DEFL 
CIENCIES. 
By S. M. McMukran, 
Assistant Pathologist, Office of Fruit-Disease Investigations. 
CONTENTS. 
Page^ 
Seriousness of the disease 1 
Previous work „ 1 
Present investigations 2 
The common factor in pecan rosette 2 
The experiments 4 
Purpose of the experiments 4 
Results of the experiments 5 
Page. 
Discussion of the experiments 6 
Lime and rosette # 7 
The root system and rosette 7 
Prevention and control 9 
The use of cover crops 9 
The use of fertilizers 10 
Importance of proper soil , 11 
SERIOUSNESS OF THE DISEASE. 
The so-called rosette is considered generally by growers to be the 
most serious trouble to which pecan trees are subject, and this opinion 
is justified by the facts. Probably 10 to 20 per cent of the pecans 
planted in orchards in the southeastern United States have shown 
this trouble in a more or less marked degree, and the resulting loss 
of tree growth and nut production undoubtedly has been great. 
In its earliest stages the disease is indicated by a few small, 
wrinkled, yellow-mottled leaves at the ends of the branches. All 
gradations of the disease are found between that shown by these 
first symptoms and the condition illustrated in figure 1, where the 
tree is dying back. The writer has never seen a tree which has died 
entirely as a direct result of rosette, but affected trees become so 
weakened that frequently they are killed by winter injury and borer 
attacks. Seriously affected trees rarely bear nuts, and they make but 
little growth. 
PREVIOUS WORK. 
Investigations conducted by the United States Department of 
Agriculture 1 between 1902 and 1913 showed that no parasitic organ- 
1 Orton, W. A., and Rand, F. V. Pecan rosette. In Jour. Agr. Research, vol. 3, no. 2, 
p. 149-174, 1916. 
89796°— Bull. 756—19 
