CITRUS SCAB! TTS CAUSE AND CONTROL. 
27 
To determine whether or not Cladosporium citri Massee usually 
found in older scab scars was responsible for the disease, a set of tests 
parallel with those in Tables 6 and 7 was run. The organisms used 
in this test were isolated from scab lesions from time to time, grown 
and applied in a manner similar to that employed in the preceding 
inoculation tests. The data from these tests, as indicated in Table 9 
resulted from inoculations on fruit and leaves of the Satsuma orange 
and grapefruit. 
Table 9. — Results of inoculations of Cladosporium citri on leaves and fruits of grapefruit 
and Satsuma orange. 
Date 
Part. 
Size (in 
six- 
teenths 
of an 
inch). 
Total 
inocu- 
lations. 
Dropped. 
Re- 
main- 
ing. 
Total 
posi- 
tive. 
Total 
nega- 
tive. 
Per- 
cent- 
age 
posi- 
tive. 
Degree of 
infection. 
Grapefruit: 
Oct. 24, 1917 
Apr. 5, 1918 
May 1, 1918 
Leaves 
...do.. 
...do.. 
0) 
0) 
(M 
4 to 8 
6 to 8 
5 
StolO 
8 to 24 
12 
12 to 16 
16 to 20 
4 to 8 
8 
12 
37 
50 
51 
50 
40 
48 
46 
50 
40 
50 
42 
52 
50 
51 
13 
26 
29 
23 
12 
12 
10 
12 
L6 
9 
I 
23 
19 
24 
24 
22 
27 
28 
36 
36 
38 
24 
41 
35 
32 
27 
32 

1 
2 
2 
2 
3 
5 
5 
1 


3 
3 

24 
23 
20 
25 
26 
33 
31 
33 
23 
41 
35 
29 
24 
32 

4 
9 
7.4 
7 
8.3 
14 
13 
4 


9.3 
11 

Slight. 
Do. 
May 2, 1917 
Apr. 10, 1918 
Apr.22, 1920 
Mav 9, 1917 
May 16, 1917 
Apr. 19, 1919 
May 8, 1920. . . 
Fruit . 
...do.. 
...do.. 
...do.. 
...do.. 
...do., 
.do 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Apr. 30, 1919 
.. .do. . 
Satsuma orange: 
Mav 24, 1917.. 
. .do 
Do. 
June 17, 1920 
June 28, 1920 
...do.. 
...do.. 
Do. 
1 Expanding. 
It is evident from Table 9 that the Cladosporium found in citrus- 
scab lesions is not responsible for the disease. The checks in the 
main show a slightly higher percentage of scab than do the inocula- 
tions with Cladosporium organism but not higher than the checks 
shown in Table 6 for the series of inoculations with the citrus-scab 
organism. 
SPRAYING EXPERIMENTS. 
Until recently very little spraying was done in Florida, even on 
an experimental basis. Growers generally were not inclined to use 
copper sprays, because such fungicides, while effective against scab, 
also kill off the entomogenous fungi, resulting in a greatly increased 
number of insect pests. Unless extra applications of insecticides 
are made following applications of Bordeaux mixture, the damage 
resulting from serious scale infection is likely to more than offset the 
benefits derived from scab control. On the other hand, growers who 
used lime-sulphur solution claim this material is only partially effec- 
tive against scab but even then is more desirable for citrus orchard 
use than Bordeaux mixture. 
Similar results were obtained in experimental spraying by Steven- 
son in Porto Rico (25, 26) and Grossenbacher (7), as well as by 
Florida fruit growers who applied the two materials for test purposes. 
