ae a er re we, 
2), BULLETIN No. 756 (¥ 
Contribution from the Bureau of Plant Industry q 
WM. A. TAYLOR, Chief Sere. 
Washington, D.C. Vv January 29, 1919 
PECAN ROSETTE IN RELATION TO SOIL DEFI- 
CIENCIES. 
By S. M. McMurran, 
Assistant Pathologist, Office of Fruwit-Disease Investigations. 
CONTENTS.’ 
Page. Page 
Seriousness of the disease.............-....-- 1 | Discussion of the experiments.............-- 6 
MSTOWAGES WOLKE reer. wis a 2 i=(s.2- 22. Soe noe Us|; Limeandrosettesseern see kere see eee elses 7 
Present MVeSbigations = =.=. 22522. -52.-c26--55 2 | Theroot system and rosette. .....-....--.--- 7 
The common factor in pecan rosette......-.. 2 | Prevention and control....-.-....- peooenecce 9 
PIER BETINOM GS se joey wis = Soe os haces 4 | The use of cover crops..--.-..-..-..-.------- 9 
Purpose of the experiments..............-.-- 4 | The use offertilizers.....................- Re 10 
Results of the experiments.................- 5 | 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* between 1902 and 1913 showed that no parasitic organ- 
7 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 
