CITKtrS MELANOSE AND ITS CONTBOL. 
33 
Table 6. — Results of experimental dusting of orange trees for melanose control 
in Florida in 1922, 1923, and 1924 
Num- 
ber of 
appli- 
cation 
< 
Date applied 
Melanose infection 
Material used 
Absent 
Very 
slight 
Slight 
Me- 
dium 
Severe 
Very 
severe 
Copper -lime dust, 
15-85. 
Bordeaux dust 12 per 
2 
2 
1 

2 
2 
3 
4 
2 
3 
1 

1 
2 
3 
2 
1 
1 
1 

Apr. 29, May 22, 
1922. 
do.. 
Per cent 


62 

Per cent 
8 
6 
24 
2 
Per cent 
17 
16 
12 
17 
Per cent 
19 
54 
2 
25 
Per cent 
23 
15 

33 
Per cent 
28 
9 
cent copper. 
3-4-50 Bordeaux - oil 
May 1, 1922 

emulsion spray. 
Average of unsprayed 
plots. 
No treatment. 
May 4 and 11, 1923.. 
do 
May 4, 11, 21, 1923.. 
May 4, 11, 21, 28, 
1923. 
May 4 and 11, 1923.. 
May 4, 11,28, 1923.. 
May 4, 1923 
23 
Dusting sulphur 
Coarse flour sulphur. . . 
Copper-lime dust 
Do ..... 






33 

1 
1 
23 
47 
44 
65 
48 
13 
53 
39 
48 
46 
34 
28 
15 
41 
35 
45 
15 
7 
20 
5 
3 
35 
11 
12 
7 

1 
1 
1 
8 

3 
1 

Do 
1 
Do 
1 
3-4-50 Bordeaux - oil 

emulsion spray. 
Average of unsprayed 
plots. 
No treatment 
Apr. 29, 1924 
Apr. 29, May 6, 1924. 
Apr. 29, May 6, 13, 
1924. 
May 6 and 13, 1924.. 
May 6, 1924 
3 
Copper -lime dust, 
20-80. 
Do 






70 
1 


4 
6 
7 
5 
15 
10 
6 
16 
12 
26 
32 
17 
11 
23 
36 
41 
37 
45 
34 
26 
4 
36 
40 
34 
35 
17 
18 
35 

20 
18 
9 
Do 
12 
Do „ 
6 
Do 
9 
Do 
May 13, 1924 
May 7, 1924... 
17 
3-3-50 Bordeaux - oil 

emulsion spray. 
Average of unsprayed 
plots. 
No treatment 
10 
The data show that the copper-lime dust, the Bordeaux dust, and 
sulphur dust did not give any appreciable control of the disease in 
1922, whereas Bordeaux sprays applied at about the same time in the 
same grove gave good control. In 1923 two applications of sulphur 
dusts failed to reduce melanose, but several applications of copper- 
lime dust did apparently reduce somewhat the severity of the out- 
break. Single applications of Bordeaux-oil emulsion spray made in 
late April or early May gave a much better control of the disease than 
did as many as four dustings. 
The results obtained from dusting experiments in 1924 were cer- 
tainly no more favorable than in any of the preceding years. 
Growers generally, so far as the writers' observations go, have 
obtained somewhat similar results with dusts for melanose control. 
In one or two instances from fair to good control appears to have 
resulted from dusting, but in thcgreat majority of cases the disease 
has not been materially reduced. In the few cases where good results 
seemed to have been obtained from a reasonable number of applications 
of copper-lime dust no undusted trees were left as checks, and it is 
questionable whether the relative absence of the disease was due to the 
fungicidal effects of the dust or to a failure of the disease to develop 
even on undusted parts. Further, insect pests and mites usually do 
not become appreciably more plentiful on dusted plots during sum- 
24975°— 27 3 
