354 
Journal of Agricultural Research 
Vol. XIV, No. 9 
Table I. —Relative susceptibility of different varieties of Citrus fruits to Citrus-canker, 
arranged according to dates of articles from which the table is compiled a 
[xxx, very susceptible; xx, susceptible; x, some resistance; o, decidedly resistant; oo, immune] 
Species. 
Stevens 
Wolf 
Stirling 
Stevens 
Edgerton 
Beattie 
Massey 
Stevens 
(18) 
0 *) 
(23) 
(iq) 
( 4 ) 
(1) 
(14) 
Cm) 
Grapefruit. 
xxx 
xxxC 1 ) 
xxx 
xxx 
XXX 
TVT 
xxx 
Orange: 
Sweet. 
00 
X 
xx( 6 ) 
xx 
XX 
Navel. 
xx( 5 ) 
xx( 7 ) 
XX 
x 
Satsuma....._ 
x 
XX 
XX 
XX 
0 
Mandarin. 
xx( 9 ) 
Tangerine. 
oo( 8 ) 
XX 
.Ring. 
XX( 1 °) 
XXX ( 2 ) 
xxC 11 ) 
Trifoliate. 
XX 
XX 
xxx 
xxx 
xxx 
Lemon. 
XX 
Lime. 
XX <«, 4 ) 
00 
xx 
Kumquat. 
00 
00 
0 
Species. 
Berger 
(2) 
Swingle 
(24) 
Stevens 
(20) 
Stevens 
(21) 
Rorer 
U 7 ) 
Keller- 
man 
(«> 
Wolf 
(30 ) 
Dory- 
land (3) 
Grapefruit. 
xxx( 1 ) 
xxx & 
XXX 
xxx( 1 ) 
xxx 
xxx 
XX 
Orange: 
Sweet. 
XX ( 6 ) 
xx( 4 ) 
XX 
x 
xx( s ) 
xxx 
XX 
XX 
Naval. 
x 
xx( 4 ) 
Satsuma. 
xx ( 6 ; 
x 
x( e ) 
xxx 
X 
Mandarin. 
xx( 8 ) 
x 
x( 7 ) 
x 
Tangerine. 
xx( 7 ) 
X 
X 
0 
King... 
xx( 9 ) 
x 
x( 8 ) 
XXX ( 2 ) 
0 
Trifoliate. 
XX ( 2 ) 
xxx 
xxx 
Lemon. 
xx( io ) 
XX ( 3 ) 
00 
XX 
x( 9 ) 
X 
Lime. 
x 
xx( 8 ) 
xxx 
X 
Kumquat. 
XX 
00 
X 
Jehle. 
Species. 
Edgerton 
Wolf 
Mackie 
Newell 
Wester 
Fed. 
0 ) 
( 3 ‘) 
(13) 
(15) 
(26-29) 
Hort.Bd. 
(6) 
( 7 -q) 
(25) 
Grapefruit. 
xxx 
XXX 
xxx 
xxxO) 
xxx( 7 ) 
xxx( 7 ) 
(0 
(d) 
Orange: 
Sweet. 
xxx 
X 
x( 8 ) 
xx( 4 ) 
x( 6 ) 
x( 8 ) 
x( 7 ) 
x( 7 ) 
X 
x( 7 ) 
Navel. 
xxx 
x 
Satsuma. 
XX 
0 
X 
Mandarin. 
XX 
x 
x 
Tangerine. 
XX 
x 
XX 
x( 8 ) 
x( e ) 
x( 9 ) 
XX ( 4 ) 
King. 
X 
x( 9 ) 
x(«) 
Trifoliate. 
xxx 
xxx 
XXX ( 2 ) 
x( 10 } 
xx( 3 ) 
0 
XX ( 4 ) 
Lemon.... 
X 
xxx 
XXX ( 2 ) 
XX ( 2 ) 
Lime. 
X 
0 
xx( 3 ) 
0 (H) 
xx( 3 l 
. 
Kumquat. 
o(tf) 
Miscellaneous e . 
i 
a Numbers in parentheses within columns indicate the relative order of susceptibility. 
Stevens (20 ); Inoculations on sweet orange, trifoliate, rough lemon, and grapefruit show about 
same degree of susceptibility to infection where growth and moisture conditions are the same. 
c Wester (26-20): Mr. P. J. Wester has reported observations on the occurrence of canker under natural 
conditions at Lamao Experiment Station, near Manila, P. I. The collection of Citrus plants there includes 
about 1,000 separate numbers and embraces practically all the species of citrus being grown commercially 
in the United States, as well as many native and Asiatic forms, not commonly grown in this country. In 
addition to the recognized varieties (and some natural hybrids) observations were made on a large number 
of hybrids of the tangelo type furnished by the United States Department of Agriculture in connection with 
Crop Physiology and Breeding Investigations. The notes as to canker susceptibility showed in some cases 
results varying with the season of the year when observations were made and doubtless chance infection 
would have an influence as well. These observations are too detailed to report in this brief summary, and 
later examinations would probably make some changes necessary. It is significant, however, to note‘that 
there is a wide range of susceptibility under conditions favorable to the unrestricted spread of canker, some 
of the mandarin types of oranges being practically immune, while some of the tangelos showed marked 
resistance. Grapefruit and oranges of American origin are generally quite susceptible, while certain of the 
pomelos of Asiatic origin are reported as distinctly resistant. 
<2 Federal Horticultural Board (25): Canker found on specimen of grapefruit and other Citrus species 
from Java and on five specimens from Japan. 
* Miscellaneous varieties: Sour orange and tangelo are somewhat susceptible according to Jehle (6-9) and 
Newell (is). Mandarin limes are very resistant though not immune according to Jehle (7-10) and Newell 
(is). C. pseudolimonum , C, X. aromatica, C, longispina, C. L. davaoensis, and C. webberii are especially 
subject, C. n. papillaris , C. mitts and C. w. montana are practically immune according to Doryland (5). 
C. micrantha is quite susceptible according to Mackie (13). 
4 
