JOMAl OF ACRlOimm RESEARCH 



Vol. XIX Washington, D. C, June i, 1920 No. 5 



BEHAVIOR OF THE CITRUS-CANKER ORGANISM 

 IN THE SOIL^ 



By H. Atherton Lee ' '^<^ 



Pathologist, Fruit — Disease Investigations, Bureau of Plant Industry, ^»L 



United States Department of Agriculture ^ii^ 



INTRODUCTION 



It is a commonly accepted idea among fruit growers and horticultur- 

 ists that the citrus-canker organism, Pseudomonas citri Hasse, lives and 

 multiplies in the soil. There has been considerable field evidence to 

 support this view. Frequently after an infected tree has been cut or 

 burned down, young shoots have come up from the roots and have been 

 found to be cankered. Thus Wolf ^ writes — 



That it [P. citri^ remains alive in the soil is indicated by the appearance of diseased 

 sprouts from the roots of diseased trees which are btimed. 



Stevens ^ in 191 5 reported the successful cultivation of P. citri in 

 sterilized soil, and this has been accepted by a number of horticulturists 

 as sufficient evidence to conclude that the canker organism is a soil 

 inhabitant. 



The presence or absence of the canker organism in the soil is an im- 

 portant question, and the use of many of the eradication and quarantine 

 methods depends upon a knowledge of the behavior of the canker organ- 

 ism in the soil. The question resolves itself into three points : (i) whether 



• The investigations reported in this paper were carried on at the Lamao Agricultural Experiment 

 Station of the Philippine Bureau of Agriculture. The writer is greatly indebted to Col. Adrian Hernandez, 

 Director, and Mr. S. Apostol, Chief, Plant Industry Division of the Philippine Bureau of Agriculture, for 

 the facilities afforded at Lamao and for much other assistance. Thanks are also due Mr. Francisco 

 Galang, Superintendent of the Station at Lamao, for helpfulness at all times. 



Deep appreciation is here expressed to Mr. E. D. Merrill, botanist, of the Philippine Bureau of Science, 

 for the use of the very extensive laboratory facilities in Manila and for many other kindnesses. The photo- 

 graphs reproduced here were taken by the photographer of the Philippine Bureau of Science from the 

 material of the writer. 



'Wolf, Frederick A. otrus canker. In Jour. Agr. Research, v. 6, no. 2, p. 69-100, 8 fig., pi. 9-11. 

 1916. Literature cited, p. 98-99. 



' Stevens, H. E. citrus c.\NKER-m. Fla. Aj:r. Exp. Sta. Bui. 128, 20 p., 6 f?g. 19:-. 



Journal of Agricultural Research, Vol. XIX, No. 5 



Washington, D. C. June i, 1920 



ug Key No. G-192 



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