632 
Journal of Agricultural Research 
Vol. XXX, No. 7 
lent, were punctured, dipped in a strong 
suspension of lime wither-tip spores, 
wrapped in wet cotton swabs, and re¬ 
placed in the inoculation case for four 
days. Final observations were made 
eight days after removal from the inocu¬ 
lation case. Included in this test were 
West Indian lime, Kusaie lime, Sweet 
lime, Ponderosa lemon, seedling Cali¬ 
fornia lemon, Gold Medal grapefruit, Sil¬ 
ver Cluster grapefruit, Pineapple orange, 
seedling round orange, Mandarin 
orange, Dancy tangerine, Sour orange, 
Cuban tangelo, and Mohawk orangelo. 
The West Indian lime plants had all 
of the young shoots destroyed by 
wither tip during the first part of the 
experiment and no new growth was 
made. None of the other varieties was 
affected by the wither-tip disease during 
the progress of this very severe test. 
In another somewhat similar test an 
inoculation chamber was used at an 
average temperature of 80° F. with the 
air practically saturated. Three plants 
of each variety were selected, all having 
very tender shoots with leaves just 
beginning to expand. These were 
punctured, and the inoculum, a heavy 
suspension of spores from lime lesions, 
was applied with cotton swabs. Fur¬ 
ther applications of spore suspensions 
were made with an atomizer on the 
second and the fifth day. On the sixth 
day the plants were removed from the 
inoculation chamber. 
The West Indian lime plants devel¬ 
oped 100 per cent infection. No in¬ 
fection developed on other varieties in 
the test, namely, Sweet lime, Rangpur 
lime, Kenedy lemon, Ponderosa lemon, 
seedling California lemon, Dancy 
tangerine, Mandarin orange, Pineapple 
orange, seedling Florida orange, Sour 
orange, Silver Cluster grapefruit, Gold 
Medal grapefruit. 
Tests were undertaken to determine 
the susceptibility of a large number of 
plants grown under greenhouse condi¬ 
tions. Most of these were 1 to 3.years 
old, well branched, and furnishing 
flushes of growth that seemed normal. 
The inoculum was usually a freshly 
made spore suspension from an actively 
sporulating wither-tip lesion on the 
West Indian lime, but in some cases 
the spores were from pure cultures of 
G. limetticolum. Very young shoots 
were selected that had leaves young 
enough to develop infection if the plant 
was susceptible. In some tests the 
leaves were punctured some 50 times 
each. The spore suspension was ap¬ 
plied on wet cotton, the shoot wrapped 
in paraffin paper, and the plant placed 
in a large glass-enclosed inoculation 
chamber over wet sand. Observations 
were made after 7 to 10 days. Control 
tests were carried on with each series to 
show the pathogenicity of the inoculum 
on West Indian lime. The results of 
these tests are summarized in Table II. 
Table II.— Greenhouse tests by artificial inoculation for susceptibility to Gloeo- 
sporium limetticolum 
Varieties tested 
Unpunctured 
Punctured 
Number of tests j 
Total shoots 
Per cent positive 
Per cent doubtful 
Per cent negative 
Number of tests 
Total shoots 
Per cent positive 
i 
Per cent doubtful 
Per cent negative 
LIMES 
West Indian_ 
23 
74 
57 
11 
32 
39 
109 
93 
4 
3 
Dominican Thornless- 
3 
12 
100 
0 
0 
5 
19 
100 
0 
0 
Persian_ 
4 
13 
0 
5 
95 
11 
28 
0 
18 
82 
Kusaie_ 
4 
24 
0 
0 
100 
13 
70 
0 
0 
100 
Sour Lime No. 7338 «_ 
2 
6 
0 
0 
100 
8 
19 
0 
0 
100 
Sweet_ 
3 
19 
0 
0 
100 
4 
26 
0 
4 
96 
Rangpur_ 
9 
41 
0 
2 
98 
19 
80 
0 
4 
96 
LIME HYBRIDS 
Limequat_ 
7 
11 
0 
9 
91 
8 
18 
0 
11 
89 
Faustrime. - 
19 
118 
0 
0 
100 
42 
302 
0 
9 
91 
CITRONS 
Citrus medica (Susceptible 
strains)__.. 
14 
31 
0 
13 
87 
34 
87 
23 
21 
56 
Citrus medica (other strains).. 
17 
35 
0 
0 
100 
38 
84 
0 
20 
80 
Sour Citron No. 7425 0 _ 
5 
9 
0 
22 
78 
6 
25 
0 
8 
92 
Etrog Citron__ 
3 
10 
0 
0 
100 
9 
20 
0 
5 
95 
a Serial numbers of the Office of Crop Physiology and Breeding Investigations Bureau of Plant Industry, 
U. S. Department of Agriculture. The writer acknowledges his indebtedness to this office for a large num¬ 
ber of the unusual varieties included in the present investigation. 
