/O6

S87* NORTH FLORIDA EXPERIMENT STATION
QUINCY, -FLORIDA

August 14, 1956 1.

o^ FE> L 11 957
NFES Mimeo Rpt. 57-2 6

BLUE MOLD CONTROL IN CIGAR-WRAPPER TOBACCO PLANT BEDS
by Randall R. Kincaid
Plant Pathologist
Blue mold in beds in the Georgia and Florida shade area is not generally
as severe as it is in Georgia and Florida flue-cured tobacco. The disease appears
later, and shade varieties are mostly less susceptible than flue-cured varieties.

Control has been quite satisfactory by dusting with 15% ferbam, which has
a high margin of safety to the tender seedlings, and more recently with zineb, which'
has an adequate margin of safety. Rates of application are low compared with those
of other areas.

The annual fungicide testing program at the North Florida Experiment
Station uses plant bed plots 3 x 5 feet, in triplicate randomized blocks. Plots
are separated by boards 1 x 6 inches, 5 feet long. Nearly half of the bed is in
checks and other untreated areas, which provides abundant opportunity for infection
of treated plots.

A plot is covered during dusting with a cage made of laths and muslin.
Weighed amounts of dust are applied with a Lowell 415 plunger duster. Dusts are
applied three times a week, at rates ranging from 15 pounds per acre at each
application when the plants are small, to 35 pounds per acre when the plants are
large enough for transplanting. Treatment is started when the leaves are about
the size of a dime.

Blue mold became more severe than usual in the 1956 test area, affording
comparisons between treatments more reliable than usual. The 1956 tests included
three fungicides, each from two different sources, two different diluents, and
various concentrations. Results are given in Table 1.

The standard treatment, Dithane Z-78 diluted to 6.5% zineb with tobacco
diluent gave poor control. Parzate (6.5% zineb), Dithane M-22 (3.5% and 7.0% maneb
and Manzate (7.0% maneb) in tobacco diluent gave much better control.

Pyrophyllite as a diluent gave better control than tobacco diluent.

Streptomycin (Cyanamid) 0.5% in pyrophyllite gave good control, better
than streptomycin (Merck).

There was no evidence of burning or crimping of leaves by any of the
treatments. However, maneb 7% gave somewhat lower yields than maneb 3.5% from the
same source; differences were almost significant at the 5% level.

Maneb 3.5% appears promising for blue mold control, but further tests
with concentrations and diluents will be conducted before maneb is recommended to
growers.

RPK
8/14/56
300 cc









NORTHI FLORIDA EXPERIVEIT 3TATIOI;
QUIJCY, FLORIDA

Table 1: Results of blue mold control tests at North Florida Experiment Station, 1956.


Treat-
ment
No.


Fungicide

Dithane Z-78
Dithane Z-78 (Std.)


7 Parzate

3 Dithane
4 Dithane
5 Dithane
6 Dithane
8 Manzate

9 Strep.
10 Strep.
11 Strep.


Strep.
Strep.
Strep.


M-22
M-22
M-22
M-22


sulph.
sulph.
3ulph.

sulph.
sulph.
3ulph.


Active
ingred-
ient

6.5
6.5
6.5


1.75
1.75
3.5
7.0
7.0


(Merck)
(Merck)
(Merck)

(Cyan.)
(Cyan.
(Cyan.)


0.5
0.5
1.0

0.5
0.5
1.0


Check No treatment


Diluent


SDisease index,
March April
20 23 26 28 31 3


Pyro.
T. D.
T. D.

Pyro.
T. D.
T. D.
T. D.
T. D.

Pyro.
T. D.
T. D.

Pyro.
T. D.
T. D.


10 14 78 100 100 68


Cumulative yield of
seedlings per sq. yd.
March April
28-29 3 6 Stand

88 214 275 355
124 254 299 398
143 259 324 405


129
122
141
92
80

114
2
18

89
20
90


245
237
287
224
232


325
315
347
282
311


241 271
108 186
111 195

229 303
130 184
216 277


0 97 176


L. S. D., 5%
1%


95
129


391
445
453
357
388

428
317
330

411
373
429

332

113
153


8/14/56
RBK
300 cc


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ft
2
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