Group Title: Circular ;
Title: Important Irish potato diseases and how to control them /
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 Material Information
Title: Important Irish potato diseases and how to control them /
Series Title: Circular ;
Physical Description: 4 p. : ill. ; 23 cm.
Language: English
Creator: Sherbakoff, C. D ( Constantine Demetry ), b. 1878
Florida Cooperative Extension Service
Publisher: University of Florida, Division of Agricultural Extension
Place of Publication: Gainesville, Fla
Gainesville, Fla
Publication Date: 1919
Copyright Date: 1919
Subject: Potatoes -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by C.D. Sherbakoff.
General Note: Caption title.
General Note: "December, 1919."
General Note: "Florida Coopertive Extension"--P. 2.
 Record Information
Bibliographic ID: UF00102032
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 226314764

Full Text

rcular 11 December, 1919

P. H. ROLFS, Director

SCAB is a fungus disease which produces shallow pits and
orky spots on the surface of the tubers (see fig. 1). Use seed
ree from visible scab and disinfected by either of the following
1. Soak the seed for two
ours in cold formaldehyde,
ne pint to 30 gallons of water.
2. Soak the seed for four
minutes in hot formaldehyde,
wo pints to 30 gallons of
after. The temperature of the
solution during the treatment
should be 122 degrees F.
3. Soak the seed for 30 min-
tes in 1 to 1000 solution of
corrosive sublimate. Fig. 1.-Potato tuber affected with
When a "sweet" soil becomes Common Scab
contaminated with scab, seed
treatment alone will not help much unless the soil is rendered
more acid by use of acid fertilizers or by a sufficient application
of sulphur. The latter, however, should not be over 600 pounds
per acre and should be applied together with an equal amount of
air-slacked lime.
WART is a slime-mold disease. It is reputed to be the most
destructive disease of potatoes. It converts the tubers into
large, spongy warts unfit for any use. So far, the disease in
the United States has been found only in a small area of Penn-
sylvania. In case any suspected specimen is found, send it. im-
mediately to the Experiment Station, Gainesville.

2 Florida Cooperative Extension

BLACK-LEG is a bacterial disease. It causes a black rot
the potato stem; young tubers also become infected and ro
Usually, not many plants are affected. Use sound tubers f
seed, and disinfect them as for scab.
these are different descriptive names for various injuries cause
by Rhizoctonia fungus. The trouble is often responsible for
poor stand of the plants. The fungus forms small brown incrust
tions on the tubers, but spoils only the looks of the product. Ho
ever, such tubers should not be used for seed. In any case th
seed should be disinfected with either hot formal
dehyde or with corrosive sublimate as recom
mended for scab.
FUSARIAL WILT shows itself by a gradual
wilting of the plant, starting with the lower leave
which soon turn yellow. The wilt is especially
prominent during dry weather. When cut across
stems and tubers affected with wilt show dar
discolorations of woody elements but no exuda
tion of dirty-white bacteria as is the case wit
bacterial blight. To control this disease use onl
healthy seed (tubers which do not show any dis
coloration). When the disease becomes introduce
into a field, plant the land to some other crop
for at least two seasons.
SCLEROTIAL BLIGHT affects the plants near
or at the base of the stem, where it produces dry
rot of the latter (see fig. 2). The affected plants
show wilting of the tops but no inside discolor-
ation, as is the case with bacterial blight or fusa-
rial wilt. Near the diseased stems, and sometimes
on them, one may often observe numerous yellow-
ish to dark brown, mustard seed-like bodies which
"'are dormant growths of the fungus causing this
disease. To control the trouble, practice clean
cultivation. Avoid piling up fresh decaying vege-
Fig. 2. Potato
stems affected table matter. When necessary, wet the soil
with Sclerotial around plant stems with a solution of copper
blight, carbonate.
EARLY BLIGHT is a fungus disease of especial importance
in south Florida and in the extreme northwestern part of the
state. It produces numerous dead spots on the leaves, and often

Circular 11, Irish Potato Diseases 3

uses a considerable reduction of the yield. The spots are brown
d with somewhat distinct zonations (see fig. 3). To control
is disease spray the plants with 5-5-50 Bordeaux mixture.
egin to spray when the
plants are about 6 inches
igh and repeat the treat-
ent about every ten days.
n some soils, particularly
n soils only recently put in
cultivation and with an acid
action, the disease often
roves to be very destruc-
ive, especially during pro-
onged hot weather. Affected
lants show sudden wilting
nd soon die (see fig. 4).
en stems or tubers of af-
ected plants are cut across Fig. 3.-Potato leaf affected with Early
hey show a ring of discol- blight
red woody tissues from which a dirty-white, pus-like exudation
ay be seen (see fig. 5). Diseased tubers often show an abnormal
development of lenticeles and "leaky" eyes with some soil sticking
o them. Such tubers will rot in a short time and should never
be shipped. Proper crop rota-
a tion is, so far, the only known
"" remedy. Besides potatoes, the
disease also affects tomatoes,
eggplants, castor beans, some of
the garden beans, and several
other plants.
LATE BLIGHT is carried in
the seed from season to season.
In Florida, the spring crop alone
seems to be subject to this
trouble. If the season is fairly
rainy the disease is sure to be-
Fig. 4.-Potato plant on the left come of considerable import-
is affected with Bacterial blight ance. It produces large dead
leaf spots (see fig. 6), which on the lower side show a character-
istic downy growth of the fungus causing this disease. It leads
also to stem decay. Once started, if the weather is continuously

Florida Cooperative Extension

Fig. 5.-Potato tubers affected with Bacterial blight

rainy, all the plants in the entire field will be killed in a few day
The tubers may also become infected and then they will be unfi
for shipment. The great shortage of the yield in the spring o
1919 was largely due to this disease. Spraying with 4-4-50 o
5-5-50 Bordeaux mixture is the only effective remedy. Spray a
for Early Blight.
MOSAIC: The cause of th
S' disease is not well known. It i
manifested by mottled color an
wrinkled appearance of the
leaves. It is carried entirely ir
the seed, and therefore, only see
properly certified to be fre(
from this disease should be used.
While the trouble does not kill
the plants, the yield is consider-
ably reduced.
LEAF ROLL: Leaves of af-
fected plants roll up and inward
along the main vein, and the
whole plant will become more or
less noticeably dwarfed. Such
plants usually do not produce
any yield of tubers and thus are
a total loss to the grower. The
cause of the disease is not well
known. Only seed properly cer-
Fig. 6.-Potato leaf affected with tified to be free from this dis-
Late blight
ease should be used.
GENERAL RECOMMENDATIONS: Use only healthy seed,
free from Mosaic, Leaf-Roll, and other diseases; disinfect the
seed before planting; spray the plants with Bordeaux mixture.

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