FURTHER STUDIES ON THE RELATIVE SUSCEPTIBILITY 
TO CITRUS CANKER OF DIFFERENT SPECIES AND 
HYBRIDS OF THE GENUS CITRUS, INCLUDING THE 
WILD RELATIVES 1 
By George L. Peltier, formerly Plant Pathologist, Alabama Agricultural Experi¬ 
ment Station, and Agent, Bureau of Plant Industry, United States Department of 
Agriculture, and William J. Frederich, formerly Assistant Pathologist, Bureau 
of Plant Industry, United States Department of Agriculture 
INTRODUCTION 
The object of this paper is to present in a summarized form the results of the 
writer’s investigations, expending from 1917 to 1921, on the relative susceptibility 
of citrus canker of a large number of different species, hybrids, and relatives of the 
genus Citrus. During the progress of this investigation two detailed reports 2 , 3 
have appeared. Since the last report was issued, new plants have been added 
to the experiments, further numbers successfully infected and in some cases 
continued observations have modified previous conclusions. 
The reader is referred to the reports already published for the description of 
the plants used, the location of the experiments, experimental methods em¬ 
ployed and the detailed observations made. The complete data on each plant 
included in the experiments during the course of the investigation are on file 
in the Office of Crop Physiology and Breeding Investigations, Bureau of Plant 
Industry, United States Department of Agriculture, Washington, D. C. 
SUSCEPTIBILITY OF THE WILD RELATIVES OF THE GENUS 
CITRUS 
Repeated attempts to infect Melia azedarach L., in the field were unsuccessful. 
Likewise, under greenhouse conditions, negative results w'ere obtained with 
Xanthoxylum bungei Planch., Xanthoxylum sp., Toddalia asiatica (L.) Kurz 
and Glycosmis pentaphylla Correa. A few small infections on leaves were ob¬ 
tained under greenhouse conditions with Claucena lansium (Lour.) Skeels, and 
Chalcas exotica (L.) Millsp. However, these results could not be duplicated 
in the field. Casimiroa edulis Lav. & Lex., was the only plant of this group 
that w r as successfully infected at w r ounds on the leaves, in the field and green¬ 
house. 
1 Received for publication Feb. 16, 1924. Published with the approval of the Director of the Alabama 
Agricultural Experiment Station. The paper is based on cooperative investigations between the Office of 
Crop Physiology and Breeding Investigations, Bureau of Plant Industry, U. S. Department of Agricul¬ 
ture and the Department of Plant Pathology, Alabama Agricultural Experiment Station. 
3 Peltier, G. L. susceptibility and resistance to citrus-canker of the wild relatives, 
citrus fruits, and hybrids of the genus citrus. [Preliminary paper.] Jour. Agr. Research 14: 337- 
358, illus. 1918. 
3 -and Frederich, W. J. relative susceptibility to citrus-canker of different species and 
hybrids of the genus citrus, including the wild relatives. Jour. Agr. Research 19: 339-362, illus. 
1920. 
Journal of Agricultural Research, 
Washington, D. C. 
(227) 
Vol. XXVIII, No. 3 
Apr. 19. 1924 
Key No. Ala.—9 
