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 Table of Contents
 Prevalence and seriousness, and...
 Historical aspects of control...
 The investigations in Florida
 Discussion of results in Flori...
 Summary and conclusions
 Literature cited














Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Effect of seed-potato treatment on yield and rhizoctonosis in Florida from 1924 to 1929
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 Material Information
Title: Effect of seed-potato treatment on yield and rhizoctonosis in Florida from 1924 to 1929
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 34 p. : chart ; 23 cm.
Language: English
Creator: Gratz, L. O ( Levi Otto ), b. 1894
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1930
Copyright Date: 1930
 Subjects
Subject: Seed potatoes -- Florida   ( lcsh )
Potatoes -- Diseases and pests -- Control -- Florida   ( lcsh )
Potato-rot   ( lcsh )
AGRICULTURA   ( renib )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 31-34).
Statement of Responsibility: by L.O. Gratz.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026845
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: ltuf - AEN4079
oclc - 18176299
alephbibnum - 000923528

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Table of Contents
    Front Cover
        Page 1
        Page 2
    Table of Contents
        Page 3
        Page 4
    Prevalence and seriousness, and losses in the United States
        Page 5
        Page 6
    Historical aspects of control measures
        Page 7
        Page 8
        Page 9
    The investigations in Florida
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Discussion of results in Florida
        Page 27
        Page 28
        Page 29
    Summary and conclusions
        Page 30
    Literature cited
        Page 31
        Page 32
        Page 33
        Page 34
Full Text


Bulletin 220 September, 1930
(Received for Publication Feb. 8, 1930)
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION UL1
Wilmon Newell, Director
A. Lf.! /LU ;





EFFECT OF SEED-POTATO TREATMENT

ON YIELD AND RHIZOCTONOSIS

IN FLORIDA FROM 1924 TO 1929

By L. O. GRATZ








TECHNICAL BULLETIN











Bulletins will be sent free upon application to the
Agricultural Experiment Station
GAINESVILLE, FLORIDA










BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola RAYMER F. MAGUIRE, Orlando
A. H. BLENDING, Leesburg FRANK J. WIDEMAN, West Palm Beach
W. B. DAVIS, Perry J. T. DIAMOND, Secretary, Tallahassee

STATION EXECUTIVE STAFF
JOHN J. TIGERT, M.A., LL.D., President IDA KEELING CRESAP, Librarian
WILMON NEWELL, D. Sc., Director RUBY NEWHALL, Secretary
S. T. FLEMING, A.B., Asst. Director K. H. GRAHAM, Business Manager
J. FRANCIS COOPER, M.S.A., Editor RACHEL McQUARRIE, Accountant
R. M. FULGHUM, B.S.A., Asst. Editor HENRY ZEIGLER, Farm Foreman

MAIN STATION-DEPARTMENTS AND INVESTIGATORS
AGRONOMY ECONOMICS, AGRICULUTRAL
W. E. STOKES, M.S., Agronomist C. V. NOBLE, Ph.D., Agricultural Economist
W. A. LEUKEL, Ph.D., Associate BRUCE McKINLEY, A.B., B.S.A., Associate
G. E. RITCHEY, M.S.A., Assistant* M. A. BROOKER, M.S.A., Assistant
FRED H. HULL, M.S., Assistant JOHN L. WANN, B.S.A., Assistant
J. D. WARNER, M.S., Assistant
JOHN P. CAMP, M.S.A., Assistant ECONOMICS, HOME
OUIDA DAVIS ABBOTT, Ph.D., Head
ANIMAL HUSBANDRY L. W. GADDUM, Ph.D., Biochemist
A. L. SHEALY, D.V.M., Veterinarian in C. F. AHMANN, Ph.D., Physiologist
Charge
E. F. THOMAS, D.V.M., Asst. Veterinarian ENTOMOLOGY
R. B. BECKER, Ph.D., Associate in Dairy J. R. WATSON, A.M., Entomologist
Husbandry A. N. TISSOT, M.S., Assistant
W. M. NEAL, Ph.D., Assistant in Animal H. E. BRATLEY, M.S.A., Assistant
Nutrition L. W. ZIEGLER, B.S., Assistant
C. R. DAWSON, B.S.A., Assistant Dairy
Investigations HORTICULTURE
CHEMISTRY A. F. CAMP, Ph.D., Horticulturist
M. R. ENSIGN, M.S., Assistant
R. W. RUPRECHT, Ph.D., Chemist HAROLD MOWRY, B.S.A., Associate
R. M. BARNETTE, Ph.D., Associate A. L. STAHL, Ph.D., Assistant
C. E. BELL, M.S., Assistant G. H. BLACKMON, M.S.A., Pecan Culturist
J. M. COLEMAN, B.S., Assistant C. B. VAN CLEEF, M.S.A., Greenhouse Fore-
H. W. WINSOR, B.S.A., Assistant man
H. W. JONES, B.S., Assistant
PLANT PATHOLOGY
COTTON INVESTIGATIONS W. B. TISDALE, Ph.D., Plant Pathologist
W. A. CARVER, Ph.D., Assistant G. F. WEBER, Ph.D., Associate
E. F. GROSSMAN, M.A., Assistant A. H. EDDINS, Ph.D., Assistant
PAUL W. CALHOUN, B.S., Assistant. K. W. LOUCKS, M.S., Assistant
RAYMOND CROWN, B.S.A., Field Assistant ERDMAN WEST, B.S., Mycologist

BRANCH STATION AND FIELD WORKERS
L. O. GRATZ, Ph.D., Asso. Plant Pathologist in charge, Tobacco Exp. Sta. (Quincy)
R. R. KINCAID, M.S., Assistant Plant Pathologist (Quincy)
JESSE REEVES, Farm Superintendent, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
GEO. D. RUEHLE, Ph.D., Assistant Plant Pathologist (Lake Alfred)
W. A. KUNTZ, A.M., Assistant Plant Pathologist (Lake Alfred)
B. R. FUDGE, Ph.D., Assistant Chemist (Lake Alfred)
W. L. THOMPSON, B.S., Assistant Entomologist (Lake Alfred)
R. V. ALLISON, Ph.D., Soils Specialist in charge Everglades Experiment Station (Belle Glade)
R. W. KIDDER, B.S., Foreman, Everglades Experiment Station (Belle Glade)
R. N. LOBDELL, M.S., Assistant Entomologist (Belle Glade)
F. D. STEVENS. B.S., Sugarcane Agronomist (Belle Glade)
H. H. WEDGWORTH, M.S., Associate Plant Pathologist (Belle Glade)
B. A. BOURNE, M.S., Associate Plant Physiologist (Belle Glade)
J. R. NELLER, Ph.D., Associate Biochemist (Belle Glade)
FRED YOUNT, Office Assistant (Belle Glade)
M. R. BEDSOLE, M.S.A., Assistant Chemist (Belle Glade)
A. N. BROOKS, Ph.D., Associate Plant Pathologist (Plant City)
R. E. NOLEN, M.S.A., Field Assistant in Plant Pathology (Plant City)
A. S. RHOADS, Ph.D., Associate Plant Pathologist (Cocoa)
C. M. TUCKER, Ph.D., Associate Plant Pathologist (Hastings)
H. S. WOLFE, Ph.D., Associate Horticulturist (Homestead)
L. R. TOY, B.S.A., Assistant Horticulturist (Homestead)
STACY O. HAWKINS, M.A., Field Assistant in Plant Pathology (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
FRED W. WALKER, Assistant Entomologist (Monticello)
D. A. SANDERS, D.V.M., Associate Veterinarian (West Palm Beach)
M. N. WALKER, Ph.D., Associate Plant Pathologist (Leesburg)
W. B. SHIPPY, Ph.D., Assistant Plant Pathologist (Leesburg)
C. C. GOFF, M.S., Assistant Entomologist (Leesburg)
J. W. WILSON, Ph.D., Assistant Entomologist (Pierson)
*In cooperation with U. S. Department of Agriculture.



















CONTENTS

PAGE
PREVALENCE AND SERIOUSNESS ..................................... 5
LOSSES IN THE UNITED STATES ....... ............................ 5
HISTORICAL ASPECTS OF CONTROL MEASURES ......................... 7
Early development ........................................ 7

Customary Methods of Treatment.............................. 7

Present-Day Recommendations ............................... 8

THE INVESTIGATIONS IN FLORIDA .................. ...... .......... 10

The Scope of the Work ..................................... 10

The Experiments in 1924 ...................... .............. 11

The Experiments in 1925. ................................... 13

The Experiments in 1926 ................................... 13

The Experiments in 1927.................................... 18

The Experiments in 1928 ................ .................. 23

The Experiments in 1929 ................................... 25

DISCUSSION OF RESULTS IN FLORIDA ................................. 27

CONCLUSIONS ............ ............. ............... ......... 30

SUMMARY ............. ......................................... 30

LITERATURE CITED ..................... ........... ......... ...... 31













EFFECT OF SEED-POTATO TREATMENT
ON YIELD AND RHIZOCTONOSIS

IN FLORIDA FROM 1924 TO 1929
By L. O. GRATZ

PREVALENCE AND SERIOUSNESS,
Rhizoctonosis (Corticium vagum B. & C.) of potatoes is prob-
ably observed more often than any other disease of plants. In
some sections it is considered the most serious trouble of that
particular crop. In general, its seriousness is due not to the
extremely high percentage loss in any one locality, but to its
universal existence wherever potatoes are grown.

LOSSES IN THE UNITED STATES
A comprehensive idea of the injury to potatoes by rhizoctonosis
and of the wide distribution of this pathogene may be obtained
by a study of Table I and Fig. 1. These show the losses in bushels
and percent for every state, and the average losses in the United
States for the 10-year period 1918-1927, as estimated by the col-
laborators with the Plant Disease Survey of the Bureau of Plant
Industry, United States Department of Agriculture.













^^ }CENT




Fig. 1.-Average percentage losses caused by rhizoctonosis (Corticium vagum
B. & C.) in the different states of the United States for the 10-year
period from 1918 to 1927.








6 Florida Agricultural Experiment Station

TABLE I.-THE PERCENTAGE AND BUSHEL LOSSES IN YIELDS OF POTATOES CAUSED BY
RHIZOCTONIA (Corticium vagum B. & C.) IN THE DIFFERENT STATES OF THE UNITED
STATES, AS REPORTED IN THE PLANT DISEASE REPORTER, AND THE CONTROL
MEASURES RECOMMENDED.

Classification Years Average Losses Treatment Most Recent
State according to DatLiterature Cited
production available percent bushels
Kan..... MiLS...... 9 9.2 519,222 HgC12 or CH2O... (23) (47) (91)
Ore..... MiLS..... 9 8.4 506,888 HgCl2 .......... (50) (L)4
Mo.... LD........ 3 7.0 567,333 HgCl2 or CH2O. .. (62) (65) (66)
Ariz.... SE....... 8 6.9 27,250 Acid HgCl2....... (11) (83) (L)
Wash.... MiLS..... 10 6.0 609,500 HgCl. .......... (19-21) (56)
Ky..... LD........ 8 5.5 480,250 HgC2. .......... (28)
Iowa.... LD........ 7 5.3 480,714 CH2 ............ (5) (31) (51-54) (64)
Cal..... MiLS...... 7 4.9 661,571 HgCl .......... (55) (74)
Id...... MiLS...... 9 4.3 638,444 CH20 ........... (37) (68) (70)
Mich.... MiLS...... 10 4.1 1,855,100 HgC12........... (41) (57) (58) (59) (60)
S. C.... SE........ 6 4.0 119,833 HlgC2 or OrgHg. (L)
Wyo.... MiLS...... 29 3.5 154,000 HgC14........... (45)
N.Y.... MajLS... 10 3.3 1,758,700 HgC2 (coldor hot). (6)(7)(12-14)(16)(36)(84)
N.C.... SE ....... 8 3.3 219,875 HgC2 or CHO... (25)
Pa...... MajLS.... 7 3.1 1,274,555 HgCl. .......... (49)
Neb.... MiLS..... 4 3.0 279,500 HgCl2 .......... (32)
Nev.... MiLS..... 3 3.0 32,333 HgCl2 .......... (40) (L)
N.J.... MaLS..... 8 3.0 1,365,500 OrgHg........... (46) (47) (48)
N.D.... MajLS.... 10 3.0 333,300 HgC12 .......... (8) (9)
Minn... MajLS.... 10 2.8 1,102,900 HgC ........... (22) (43) (76)
Utah.... MiLS..... 7 2.7 107,000 HgCl2.......... (71) (82)
Md..... LD....... 10 2.7 151,900 HgC12 or OrgHg. (2) (L)
Ohio.... LD........ 5 2.4 376,000 HgCI. .......... (27) (85)
Del..... LD........ 2 2.2 ? OrgHg........... (L)
S.D..... MiLS...... 8 2.2 181,875 HgCI1 or CH20... (1) (3)
Va...... SE........ 9 2.0 342,000 HgC2. .......... (L)
Wis..... MajLS.... 10 1.6 535,300 CH2O........... (15)(47)(75)(86-89)
Colo.... MiLS..... 3 1.5 175,666 HgCI2.......... (77)
Ga...... SE........ 4 1.5 38,250 HgC12.......... (92)
Me..... MajLS.... 3 1.3 528,666 HgCl2 .......... (78) (79)
Mont... MiLS..... 5 1.3 74,200 No information .. (L)
N. H.... LD....... 3 1.3 63,600 HgCls. ......... (39)
Vt...... LD........ 5 1.3 65,600 HgCl2 .......... (30) (L)
Mass.... LD........ 5 1.0 40,400 HgC2 ........... (26)
La...... SE........ 3 1.0 ? CH20 ........... (L)
Tex..... SE ..... 5 1.0 31,400 CH2.O........... (L)
Conn... LD....... 5 0.5 12,400 HgCl ........... (69)
Fla..... SE........ 6 tr........
Ind..... LD........ 4 0.4 27,000 HgC1.......... (42)
Ill...... LD........ 3 tr. ............ HggCl ......... (24) (L)
Miss.... SE........ 4 tr. .......... No information... (L)
Tenn.... SE........ 1 tr. ........... HgCl. .......... (L)
W Va... LD........ 8 tr. .......... HgC2 .......... (29)
Ala..... SE ........ 0 0 .......... HgC12 ........... (L)
Ark..... SE....... 0 0 .......... No information... (L)
Okla.... SE ........ 0 0 .......... HgCl ........... (67)
N. Mex. SE........ 0 0 .......... HgCls or OrgHg .. (L)
R.I.... LD........ 0 0 .......... No information... (L)
U. S.... ........... 10 2.4 11,898,200

'MiLS-Minor Late Surplus. 2HgCl2-Cold corrosive sublimate.
MajLS-Major Late Surplus. CHO20-Hot formaldehyde.
LD-Late Deficient. Acid HgC12-Acidulated cold corrosive sublimate.
SE-Southern Early. OrgHg-Organic mercury compounds.
sObservations over too short a period of years to render data valuable.
4L-Personal letter to writer.







Bulletin 220, Effect of Seed Potato Treatment 7

Obviously, the largest total losses occur in the major and minor
late surplus potato-producing states (Table I), because of the
comparatively large acreage planted there every year. Figure 1,
which gives a graphic representation of the percentage losses in
the different states, indicates that while the disease is least severe
in the southern states it is not always, as is frequently stated, the
most severe in the northern states.


HISTORICAL ASPECTS OF CONTROL MEASURES
EARLY DEVELOPMENT
Treatment of potatoes in the United States actually started in
1891 when Bolley, in North Dakota, conducted his experiments
on the prevention of potato scab(10)1. In 1897 Arthur conducted
similar experiments in Indiana (4). Jones introduced the formal-
dehyde gas method for scab control in 1900(38). In 1902 Rolfs,
in Colorado, observed high percentages of the plants in certain
potato fields manifesting symptoms of rhizoctonosis and recom-
mended treatment either with formaldehyde or corrosive subli-
mate(73). Later he recommended the latter in particular as a
specific control measure(72). About this time Selby in Ohio(80,
81), and in 1912 Giissow in Canada(35) conducted similar experi-
ments, and it was not very long until experimental work was con-
ducted in many parts of the country to determine the relative
merits of the two treatments for controlling both scab and rhizoc-
tonosis. These numerous investigations resulted in a rather com-
mon opinion that corrosive sublimate controlled rhizoctonosis
better than formaldehyde.

CUSTOMARY METHODS OF TREATMENT
The accepted standard method of treatment until somewhat
recently was to soak the tubers in a 1:1,000 solution (4 oz. to 30
gallons water) of corrosive sublimate, or in a 1:240 solution (1
pt. to 30 gallons water) of commercial formaldehyde at ordinary
temperatures. These methods are cumbersome and slow, and
Melhus and Gilman (52, 53, 31), using formaldehyde, offered some
modifications by increasing the strength to 1:120 and the tem-
perature to 50 C. (122 F.), and decreasing the time to 2 minutes.
In New York state the use of hot rather than cold corrosive subli-
1Figures in parentheses (italic) refer to "Literature Cited" in the back of
this bulletin.






8 Florida Agricultural Experiment Station

mate has been reported as giving promising results (12, 16, 84).
The use of acidulated corrosive sublimate is being reported occa-
sionally and appears promising(43, 18, 17, 11). In 1924 the use
of organic mercury compounds was begun in an experimental way
in this country(48). These materials have been developed to such
an extent that, at present, they need to be considered as possible
specifics for the control of tuber-borne rhizoctonia and scab,
although they have not yet proved generally satisfactory.

PRESENT-DAY RECOMMENDATIONS
The investigational work on seed treatment of potatoes was
given a new impetus throughout the country during the last few
years, possibly because of the appearance of the new proprietary
organic mercury compounds. It is not within the scope of this
paper to give a complete summary of all seed treatment literature,
but a review of the very recent publications and recommendations
demonstrates that, even though the experimental results are con-
flicting at times, corrosive sublimate is still considered the most
efficient method in most of the states for the control of rhizocto-
nosis (Table I). Schultz and his associates(79, 78), working in
northern Maine, found that seed treatment with either corrosive
sublimate, formaldehyde, or organic mercury compounds im-
proved the stand, reduced seed-piece decay, increased the vigor of
the plants, inhibited the formation of stem lesions and tuber-
borne sclerotia, and increased the yield. Furthermore, they ascer-
tained that rhizoctonosis was better controlled, and in general,
larger increases in yield resulted where the tubers were treated
with corrosive sublimate according to the old standard formula.
Clayton(13), on Long Island, found that the organic mercury
compounds were less effective in controlling rhizoctonosis than
corrosive sublimate, and that both treatments were unprofitable
to the growers in that section. White(91), in Kansas, found hot
formaldehyde and corrosive sublimate equally efficient, while
Moore, Wheeler, and Kotila(41, 57, 58, 59), in Michigan, demon-
strated "the old methods (corrosive sublimate) satisfactory".
Similar conclusions could be cited from Connecticut, Washington,
Ohio, Wyoming and many other states (Table I). Orton and
Miles(60, 61), in summarizing the results of various investigators
in different parts of the United States, concluded that corrosive
sublimate was the most efficient treatment in controlling rhizocto-
nosis. As indicated in Table I, the various treatments are recom-








Bulletin 220, Effect of Seed Potato Treatment 9

mended by different numbers of states in the United States as
follows:
Organic mercury compounds............................. 2
Organic mercury compounds or corrosive sublimate-cold... 3
Corrosive sublimate-cold, acidulated .................... 1
Corrosive sublimate-cold or hot........................ 1
Corrosive sublimate- cold .............................. 27
Corrosive sublimate-cold, or formaldehyde-hot ......... 4
Formaldehyde- hot .................................... 5
No information available ............................... 4
47*
*Florida not included.

JAN. AP 26 AP.R r
15 +1 F l 2 /1.y *
FORIOA GROWING 5EASvN-


700 CL
S-FLORI/A








S,/ \



50/




0
45 IMAINE GROWING .54Soiv -
1S 25 + 1I 24 + 4 24. 3 Is z3 i .
1AY JUNE J/ty Atv. brp:
/ Z 3 4 3s 7 i V 10 I z 3 13 is 16 iis i
WEKS AFTER PLANTING

Fig. 2.-Daily average mean temperatures during the periods 1917-1926 and
1916-1926* for the potato-growing seasons at Federal Point, Florida,
and Aroostook Farm, Presque Isle, Maine, respectively.
*Data for 1918 missing.








10 Florida Agricultural Experiment Station

THE INVESTIGATIONS IN FLORIDA
THE SCOPE OF THE WORK
Since only a trace of rhizoctonosis is usually observed on pota-
toes in Florida, seed treatment investigations appear unwarranted.
However, with the knowledge that (1) recommendations in one
section frequently do not apply in another section; (2) many con-
flicting results are obtained in different or the same localities
where the old standard formulas are used; (3) new materials have
been introduced which should be quicker and more efficient; (4)
on all shipments of seed stock into Florida a small to medium num-
ber of sclerotia are usually found since all seed stock is imported
from northern states, chiefly Maine, where the fungus is uniformly
distributed; (5) the crop is planted in the winter months when the
temperatures during the early part of the growing season are
somewhat similar to those during the corresponding period in the
northern potato sections (Fig. 2)1; (6) no experimental evidence
is on record for this territory; (7) and a low percentage increase
in yield is usually very profitable to the Florida growers as they
harvest for the early market, it was considered desirable to con-
duct such seed treatment experiments. These were continued
from 1924 to 1929, inclusive.
Maine certified Spaulding Rose No. 4 potatoes were used
throughout and, unless otherwise stated, tubers were selected and
treated on which were found numerous sclerotia of rhizoctonia.
In some instances clean, or sclerotia-free, tubers from the same
source were also treated and planted for comparison with the
other treated lots. The tubers were cut into 11/2 ounce seed pieces
which were planted at 12-inch distances in ridged rows 42 inches
apart, a small furrow having been opened immediately before, and
covered to a depth of 3 inches immediately after planting. Com-
mercial potato fertilizer was applied with a distributor, at the rate
of a ton per acre, and mixed into the soil about three to four weeks
before planting, which is the standard Florida practice. The plots
were located on typical Florida potato soil, Bladen fine sand, in
different sections of the potato belt. The tubers were treated
according to the formula recorded in the tables, and were planted
within 24 hours, except where treated with corrosive sublimate.
With this treatment whole tubers were steeped about 2 weeks
before planting, and stored, under a shelter which afforded suffi-
'See also "Literature Cited," No. 34.







Bulletin 220, Effect of Seed Potato Treatment 11

cient ventilation, with the other tubers which were to be treated
later.
Observations, unless otherwise stated, were made on stand,
seed-piece decay, relative vigor, stem lesions, tuber infection, and
yield. The observations on stem lesions and seed-piece decay were
made when the plants were about 2 to 4 inches above the surface
of the ground. Very slight stem lesions, and slight decay of the
seed pieces were included with the more severe symptoms in the
percentages given in the different tables. When harvested the
tubers were graded according to the standards of the United States
Department of Agriculture, and the yields were calculated for the
particular grades as indicated in the tables. The percentage differ-
ences in yield were obtained by comparing the yield of each treated
lot with that of the corresponding untreated diseased sample. In
1926, 1927 and 1928 the significance of the differences was deter-
mined by using Love's modification of Student's Method (44). In
1929 the formulas

PE m = .6745 x standard deviation
Number of items
PEd Va2 + b2
were used, where a = the probable error of the mean of the treated
lot and b = the probable error of the mean of the untreated lot
with which the treated sample is compared. Odds listed by Pearl
and Miner were used for the 1929 data(63), and only those in-
creases with odds of over 22:1 are considered significant.

THE EXPERIMENTS IN 19241
Corrosive sublimate in a 1:1,000 solution (4 oz. to 30 gallons
water) was the only material used in the preliminary trials of
this season. Tubers, on about half of which were found a small
number of sclerotia, were taken from the bag without any par-
ticular sorting and treated for 11/2 hours at ordinary temperatures.
Two weeks later they were cut and planted in two plots and com-
pared directly in adjoining rows 125 feet long with a similar
sample which had not been treated. Only a slight trace of stem
lesions and no typical so-called "rhizoctonia hills"2 were observed
during the season. No sclerotia (black scurf) were seen on the
tubers at digging time. Table II shows the yields which were
1See also "Literature Cited," No. 33.
"2Plants manifesting typical symptoms of the disease such as aerial tubers,
etc.










TABLE II.-EFFECT OF CORROSIVE SUBLIMATE SEED TREATMENT ON YIELD OF POTATOES AT HASTINGS, t
FLORIDA, IN 1924.

Calculated Yield Increase by Treating
Plot Treatment Barrels per Acre Barrels Percent
Market- Market- Market- %3
Primes Seconds able Primes Seconds able Primes Seconds able o

1 Corrosive sublimate....... 37.8 11.1 48.9 .... .... .... ...
Untreated............... 28.6 8.7 37.3 9.2 2.4 11.6 32.3 27.6 31.1

2 Corrosive sublimate....... 15.1 15.1 30.2 .... ...... ....
Untreated............... 19.0 14.3 33.3 -3.9 0.8 -3.1 -20.5 5.6 -9.3 2


TABLE III.-EFFECT OF CORROSIVE SUBLIMATE SEED TREATMENT ON YIELD OF POTATOES AT HASTINGS,
FLORIDA, IN 1925.

Calculated Yield Increase by Treating
Plot Treatment Barrels per Acre Barrels Percent
Plot Treatment
Market- Market- Market-
Primes Seconds able Primes Seconds able Primes Seconds able

1 Corrosive sublimate.......... ... *60.6 .... ... ....
Untreated....... ........ .... *53.0 .... .... *7.6 .... .... *14.3

2 Corrosive sublimate ....... ... ... *58.1 .... .... .... ..
Untreated............... ... .... *5.5 .... .... *3.6 .... .... *6.6

3 Corrosive sublimate....... 62.5 10.4 72.9 ... ... ....
Untreated ............... 59.0 12.1 71.1 3.5 -1.7 1.8 5.9 -14.0 2.5

*Not graded, but field barrels only.







Bulletin 220, Effect of Seed Potato Treatment 13

obtained. The results obtained were inconclusive, as in one plot
the treated samples outyielded the untreated in prime tubers by
almost one-third, and in the other plot the treated stock yielded
about one-fifth less. This difference in behavior was not explained
but a larger number of replications would have given more de-
pendable results.
THE EXPERIMENTS IN 19251
A small sample of tubers with a slight sprinkling of rhizoctonia
sclerotia was treated with the standard corrosive sublimate solu-
tion as in 1924 and compared directly in 125 foot rows, in 3 plots,
with untreated stock of the same source, as in the previous season.
No disease was observed on the stems, plants or tubers. Table III
indicates that very small and rather consistent increases in yield
were obtained by treating the seed pieces.
On the farm of one grower 14.5 percent of 400 stems from
untreated seed potatoes showed stem lesions as compared with
0.285 percent of 700 stems from seed potatoes treated with cor-
rosive sublimate which were examined when the plants were about
three inches high. This is the highest percentage of stem lesions
which the writer has ever observed in the Hastings section. Late
in the season this particular field was again examined and 5.8
percent of the plants in the untreated portion of the field mani-
fested typical rhizoctonosis symptoms, particularly aerial tubers,
while the plants in the treated section of the field showed no
symptoms of the disease. No comparable yield data were obtained.

THE EXPERIMENTS IN 1926
The experimental work in 1926 was conducted on a more exten-
sive scale than during the previous two years. All of the seed
tubers were carefully selected from shipments in which 80 percent
of the tubers were spotted with sclerotia (black scurf). All of
the tubers on which no sclerotia were seen after they had been
wetted with water to make the sclerotia more distinct, were
picked out and considered "clean controls," and those which were
not sclerotia-free were used for the various treatments. The
experimental plots were planted in two different sections and at
different times, the first in Federal Point, which is considered the
earliest section in the potato area, and the other in the later Elkton
section. In the former, planting usually starts December 20, and
in the latter about a month'later. In all of these trial plots the
'See also "Literature Cited," No. 33.








14 Florida Agricultural Experiment Station

various treatments were repeated several times as indicated below.
The individual rows were 55 hills long (1 hill per foot) and 42
inches apart. At digging time, as the stands were virtually per-
fect, enough hills were discarded at each end of the row to leave
50 hills for comparison.
In the Federal Point plots no clean checks were planted, but only
those tubers were used which were sprinkled with sclerotia. The
differently treated samples were planted according to Fig. 3, where
each figure corresponds to the treatment as indicated in Tables IV
and V.
1 3 1 4 5 1 2 1
1 1 4 5 1 2 3 1
1 4 5 1 2 3 1 1
1 5 1 2 3 1 4 1
1 1 2 3 1 4 5 1
1 2 3 1 4 5 1 1
Fig. 3.-The planting plan for the seed-potato treatment plots in Federal
Point, Florida, in 1926.

The stems from 75 hills in each lot under comparison were ex-
amined for rhizoctonosis when the plants were about three inches
above the surface of the ground, and only occasional, very slight
lesions were observed in any lot. No seed-piece decay inspection
was made at this time, but most of the seed pieces were intact
at digging. All of the plants were small and the yields were poor.
This was probably due to the wet, cold weather in the early part
of the growing season. No differences were observed in germina-
tion, size, stand, or plant vigor between the plants of the different
treatments. At harvest all of the tubers in each grade were
weighed and counted in order to have a double check on the effi-
ciency of the treatment. However, these 4nd later experiments
confirm Gilman and Melhus' statement that "In potato seed treat-
ment experiments the efficiency of the treatment can be measured
with approximately the same accuracy either by weight or count
of the percentage of diseased progeny resulting from that treat-
ment"(31). Tables IV and V show the yields in weight and num-
ber of tubers respectively. All of the treated lots were outyielded
by the untreated sample both in weight and in number of tubers
except where whole tubers were treated with Bayer compounds.
Semesan caused decided decreases where both whole and cut tubers
were treated,







TABLE IV.-EFFECT OF DIFFERENT SEED TREATMENTS ON SEED-PIECE DECAY, STEM LESIONS AND YIELD OF POTATOES AT FEDERAL
POINT, FLORIDA, IN 1926.
Calculated Yieldst Increase by Treating
Percent Barrels per Acre Barrels Percent
Treatment
Tubers Seed- Stem Market- Market- Market-
When Piece Lesions Primes Seconds able Primes Seconds able Primes Seconds able
Treated Decay ZS

(1) Diseased-untreated... 2.7 14.3 21.2 17.8 39.0 .. .. .. .....
(2) Bayer compound*.... C** 4.0 12.0 19.5 15.5 35.0 -1.7 -2.3 -4.0 -8.0 -12.9 -10.2
(3) Bayer compound*.... W 2.0 11.7 23.7 17.1 40.8 2.5 -.7 1.8 11.8 -3.9 4.6
(4) Semesan compound*. C 9.0 5.0 17.5 11.9 29.4 -3.7 -5.9 -9.6 -17.5 -33.1 -24.1
(5) Semesan compound*... W 7.0 4.7 14.7 13.1 27.8 -6.5 -4.7 -11.2 -30.6 -26.4 -28.7
*Used as a 0.25 percent solution for 30 minutes.
**C = tubers treated after cutting; W = whole tubers treated.
tAverages of 6 replications for each lot.

TABLE V.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE NUMBER OF POTATOES PRODUCED AT FEDERAL POINT,
FLORIDA, IN 1926.

Con n Number of Tubers Increase by Treating
Treatment Noof of Tubers per 50 Hills Tubers I Percent
Repli- When Market- Market- Market-
cations Treated Primes Seconds able Primes Seconds able Primes Seconds able
(1) Diseased-untreated... 6 ......... 81.5 124.3 205.8 .... ... .. ...
(2) Bayer Compound*.... 6 Cut...... 75.7 110.2 185.9 -5.8 -14.1 -19.9 -7.1 -11.3 -9.2
(3) Bayer compound...... 6 Whole... 85.4 115.8 201.2 3.9 -8.5 -4.6 4.8 -6.8 -2.2
(4) Semesan compound.... 6 Cut...... 63.6 78.5 142.1 -17.9 -45.8 -63.7 -22.0 -36.8 -31.4
(5) Semesan compound.... 6 Whole.... 54.0 86.8 140.8 -27.5 -37.5 -65.0 -33.7 -30.2 -31.6

*Treatment as shown in Table IV.
cT








16 Florida Agricultural Experiment Station

One part of the trial plots in the Elkton section consisted of
liquid treatments and the other of dust treatments. Figure 4
shows the planting arrangement for the former, where each
numeral corresponds to the treatment as given in A, Table VI.
The general arrangement for the dust treatment part was similar
to that given in Fig. 4, although the total number of treatments
was less than where the liquid treatments were compared. (B,
Table VI.)
1 2 3 4 1 2. 5 6
10 1 2 7 8 1 2 9
5 6 1 2 3 4 1 2
2 9 10 1 2 7 8 1
1 2 5 6 1 2 3 4
8 1 2 9 10 1 2 7
3 4 1 2 5 6 1 2
2 7 8 1 2 9 10 1
1 2 3 4 1 2 5 6
10 1 2 7 8 1 2 9
5 6 1 2 3 4 1 2
2 9 10 1 2 7 8 1
1 2 5 6 1 2 3 4
8 1 2 9 10 1 2 7
Fig. 4.-The planting plan for the seed-potato treatment plots in Elkton,
Florida, in 1926.
The stems of 75 hills in each treatment were examined as before.
In the liquid treatment section of the plot (Table VI-A) the dis-
eased untreated lots showed 11.8 percent, and the lots treated with
Bayer compound showed 11.4 percent of the plants with stem
lesions. Where corrosive sublimate, uspulun, and semesan were
used alone not over 3 percent of the plants showed stem injury,
but where corrosive sublimate and uspulun were used in combi-
nation 7 percent of the plants showed such lesions. This indicates
the probability of soil infection. In the other section of the plot
(Table VI-B) where dust treatments were compared with clean
untreated samples, and with samples treated with corrosive sub-
limate, the following percentages of stem lesions were observed:
Dupont's Dust Disinfectant No. 12, 0; Dupont's Dust Disinfectant
No. 37, 0; semesan dust, 10; clean treated (corrosive sublimate),
7; clean untreated, 6.
The seed pieces in the controls and in the treated lots were
practically all sound at digging as was true in the Federal Point
trials. Vine growth was good, germination was regular, and no
differences in relative vigor were observed between the treated
and untreated rows. No "rhizoctonia hills" or sclerotia on the
tubers were observed at digging time. The yields obtained are
shown in Tables VI and VII, by both weight and number of tubers,
for both the liquid and dust treatments and the corresponding






TABLE VI.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE YIELD OF POTATOES AT ELKTON, FLORIDA, IN 1926.

Calculated Yields Increase by Treating
Barrels per Acre
Treatments No. of Stem Bre r Primes Seconds Marketable
Repli- Lesions Primes Seconds Market-
cations able Barrels Percent Barrels Percent Barrels Percent
A-LIQUID TREATMENTS:
(2) Clean-corrosive sublimate......... 25 1.8 71.6 15.2 86.8 4.4 6.5 -0.7 -4.4 3.7 4.4 t
(1) Diseased- untreated .............. 25 *11.8 67.2 15.9 83.1 .... .... .... .... odds 7.14:1
(3) Clean-untreated ................. 7 2.9 63.7 18.0 81.7 -1.4 -2.2 0.6 3.4 -0.8 -1.0
(1) Diseased-untreated .............. 7 .... 65.1 17.4 82.5 .... .... ..... .... odds 1.46:1
(4) Bag run**-corrosive sublimate..... 7 0.0 70.7 9.0 79.7 -0.3 -0.4 -6.6 -4.2 -6.9 -8.0
(1) Diseased-untreated................ 7 .... 71.0 15.6 86.6 .... ... .... .... odds 1.46:1
(5) Uspulun-0.25% sol. 30 minutes.... 7 2.9 69.8 14.5 84.3 4.7 7.2 -2.9 -16.7 1.8 I 2.2
(1) Diseased- untreated ............... 7 .... 65.1 17.4 82.5 .... .... .... .... odds 2.54:1
(6) Semesan-0.25% sol. 30 minutes.... 7 2.9 71.9 12.4 84.3 6.8 10.4 -5.0 -28.7 1.8 2.2
(1) Diseased-untreated............... 7 .... 65.1 17.4 82.5 .... .... .... .... odds 1.75:1
(7) Bayer comp.-0.25% sol. 30min.... 7 11.4 74.2 13.8 88.0 3.4 4.8 -2.0 -12.6 1.4 1.6
(1) Diseased- untreated............... 7 .... 70.8 15.8 86.6 .... ... ... .... odds 1.46:1
(8) Cor. sub. and usp. (as above)....... 7 7.1 69.4 12.4 81.8 4.3 6.6 -5.0 -28.7 -0.7 -0.9
(1) Diseased-untreated............... 7 .... 65.1 17.4 82.5 .... .... .... .... odds 1.46:1
(9) Cor. sub. and Semesan (as above)... 7 0.0 62.6 11.7 74.3 -8.3 -11.7 -2.6 -18.2 -0.9 -1.1
(1) Diseased- untreated ............... 7 .... 70.9 14.3 85.2 .... .... ... .... odds 1.46:1
(10) Cor. sub. and Bay. comp. (as above) 7 2.9 76.0 13.1 89.1 6.3 9.0 -5.1 -28.0 1.2 | 1.4
(1) Diseased- untreated............... 7 .... 69.7 18.2 87.9 .... .... .... .... odds 1.46:1
B-DusT TREATMENTS: o
(2) Clean corrosive sublimate .......... 4 7.0 72.0 15.1 87.1 -1.4 -1.9 -3.1 -17.0 -4.5 -4.9
(1) Diseased-untreated ............... 4 .... 73.4 18.2 91.6 ... .... .... .... odds 1.88:1
(3) Clean-untreated. ............... 4 6.0 57.0 17.8 74.8 -15.8 -21.7 0.3 1.7 -15.5 1 -17.1
(1) Diseased-untreated .............. 4 .... 72.8 17.5 90.3 .... .... .... .. odds 108:1
(4) Bag run**-corrosive sublimate..... 4 0.0 78.6 11.7 90.3 4.3 5.8 -6.1 -34.2 -1.8 -2.0
(1) Diseased-untreated................ 4 .... 74.3 17.8 92.1 .... .... .... .... odds 1.29:1 -
(5) Semesan dust 3 oz. per bushel...... 4 10.0 83.5 12.3 95.8 12.1 16.9 -6.2 -33.5 5.9 1 6.6
(1) Diseased-untreated .............. 4 .... 71.4 18.5 89.9 .... .... .... .... odds 6.70:1
(6) Duponts dust disinfectant No. 12 ... 4 0.0 75.8 13.0 88.8 1.6 2.2 -4.3 -24.9 -2.7 1 -2.9
(1) Diseased- untreated............... 4 .... 74.2 17.3 91.5 .... .... .... .. odds 1.66:1
(7) Duponts dust disinfectant No. 37... 4 0.0 74.8 14.2 89.0 0.2 0.3 -4.0 -22.0 -3.8 -4.1
(1) Diseased-untreated ............... 4 .... 74.6 18.2 92.8 .... .... .... .... odds 1.46:1
*The general average of all untreated rows. tOnly whole tubers were treated in these trials.
**A medium number of small sclerotia on 80% of the tubers.








18 Florida Agricultural Experiment Station

control plots with which each treatment was directly paired. It
may be observed in these tables that frequent decreases as well as
occasional small increases in yield occurred in the various treated
lots, but neither are significant.
In addition to the above trials 20 165-pound bags of potatoes
were treated with corrosive sublimate according to the standard
formula and planted in alternate rows throughout the field in a
cooperative project between a grower and the writer. Eighty
percent of this lot showed a medium amount of sclerotia. When
the plants were about 3 inches high 1,300 stems in each of the
portions of the field planted with treated and untreated seed stock
were examined and the former showed 2.6 percent, and the latter
5.7 percent stem lesions. No differences in stand, which was
perfect, or relative vigor could be observed. Ten representative
50-foot sample plots were dug in the treated portions and compared
with 10 similar plots in the untreated parts of the field. The yields
obtained are as follows:
Barrels per acre.
Treated. Untreated.
Prim es ...................................... 93.0 93.7
Seconds ..................................... 15.2 13.9
M arketable .................................. 108.2 107.6

THE EXPERIMENTS IN 1927
Semesan bel and dipdust were the only two treatments used in
comparison with the standard corrosive sublimate formula in 1927.
As in 1926 the plots were planted at different places and times in
order to obtain information under different environmental con-
ditions.
The earliest plot, where semesan bel and corrosive sublimate
were the only treatments used, was planted December 5 in a
rather moist portion of a Federal Point field. This particular spot
was selected because rhizoctonosis attacks the stems more seri-
ously there than elsewhere in the potato area. Perfect stands
resulted in this plot in all treatments. When the plants were about
5 inches tall about one-third of them were frozen to the ground,
and all were again frozen January 11. The plot was undisturbed
until time for harvest and observations were then made. It was
discovered that the untreated rows had an average stand of 72
percent, while the rows treated with semesan bel and corrosive
sublimate each had 52 percent stand. The average percentages
of sound seed pieces were 51.9, 26.2, and 23.8 percent for the un-
treated, corrosive sublimate and semesan bel treated lots respec-









TABLE VII.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE NUMBER OF POTATOES PRODUCED AT ELKTON, FLORIDA, IN 1926.
(All tubers were whole when treated.)
No. of Tubers Increase by Treating

Treatments No. of _per 50 Hills Tubers Percent
Repli- Market- Market- Market-
cations Primes Seconds able Primes Seconds able Primes Seconds able

A-LIQUID TREATMENTS:
(2) Clean-corrosive sublimate ............ 25 232.0 117.0 349.0 ... ... ... ...
(1) Diseased-untreated ................. 25 219.5 122.0 341.5 12.5 -5.0 7.5 5.69 -4.1 2.20
(3) Clean-untreated.................... 7 214.0 134.0 348.0 .... .. ... .. ..
(1) Diseased-untreated.................. 7 223.6 126.0 349.6 -9.6 8.0 -1.6 -4.29 6.34 -0.46

(4) Bag run-cor. sublimate.............. 7 212.5 110.5 323.0 .. ... .... .... ... ...
(1) Diseased-untreated .................. 7 221.3 119.0 340.3 -8.8 -8.5 -17.3 -3.97 -7.14 -5.09

(5) Uspulun--0.25 % sol. 30 minutes...... 7 223.0 109.5 332.5 .... .... .... ... ..
(1) Diseased-untreated.................. 7 223.6 126.0 349.6 -0.6 -16.5 -17.1 -0.27 -13.1 -4.89
(6) Semesan-0.25% sol. 30minutes....... 7 231.0 96.0 327.0 ... ... ... ...
(1) Diseased-untreated.................. 7 209.0 111.0 320.0 22.0 -15.0 7.0 10.5 -13.5 2.19 P

(7) Bayer comp. 0.25% sol. 30 minutes.... 7 241.5 108.5 350.0 ...
(1) Diseased-untreated.................. 7 217.5 121.0 338.5 24.0 -12.5 11.5 11.0 -10.3 3.4
(8) Cor. sub. and usp. (as above).......... 7 223.5 96.5 320.0 ... .. . .... ... .
(1) Diseased-untreated .................. 7 218.0 107.0 325.0 5.5 -10.5 -5.0 2.52 -9.81 -1.53
(9) Cor. sub. and Semesan (as above) ...... 7 227.5 96.0 323.5 .... .... .... .... .... ...
(1) Diseased-untreated.................. 7 214.0 134.0 348.0 13.5 -38.0 -24.5 6.30 -28.3 -7.04

(10) Cor. sub. and Bay. comp. (as above). ... 7 235.5 104.5 340.0 .... .... .....
(1) Diseased-untreated .................. 7 217.5 132.0 349.5 18.0 -27.5 -9.5 8.27 -20.8 -2.71













TABLE VII.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE NUMBER OF POTATOES PRODUCED AT ELKTON, FLORIDA, IN 1926.
(Continued.)
(All tubers were whole when treated.)

No. of Tubers Increase by Treating
per 50 Hills
Treatments No. per 50 Hills Tubers I Percent _
Treatments No. of _________ _________
Repli- Market- Market- Market-
cations Primes Seconds able Primes Seconds able Primes Seconds able
B-DusT TREATMENTS: c
(2) Clean-corrosive sublimate ............ 4 225.9 113.9 339.8 .... .. .... .... .... ...
(1) Diseased-untreated ................. 4 229.5 144.5 374.0 -3.6 -20.6 -34.2 -1.57 -14.2 -9.14

(3) Clean-untreated.................... 4 177.1 128.0 305.1 ... .... .... .... .... ....
(1) Diseased-untreated ................. 4 224.0 138.0 362.0 -46.9 -10.0 -56.9 -20.9 -7.24 -15.7

(4) Bag run-cor. sublimate .............. 4 245.5 90.9 336.4 .... .. .. ...
(1) Diseased-untreated ................. 4 229.0 142.5 371.5 16.5 -51.6 -35.1 7.20 -36.2 -9.44

(5) Semesan Bel. dust .................. 4 260.6 96.9 357.5 ... ...
(1) Diseased-untreated ................. 4 221.0 131.7 352.7 39.6 -34.8 4.8 17.9 -26.4 1.36

(6) Duponts dust disinfectant No. 12 .... 4 243.5 107.3 350.8 .... .... ... .... .... ....
(1) Diseased-untreated.................. 4 230.0 137.5 367.5 13.5 -30.2 -16.7 5.86 -22.0 -4.54

(7) Duponts dust disinfectant No. 37...... 4 232.0 103.8 335.8 .... ... ... ....
(1) Diseased-untreated .................. 4 229.5 144.5 374.0 2.5 -40.7 -38.2 1.09 -28.2 -10.2








Bulletin 220, Effect of Seed Potato Treatment 21

tively. Yield data, shown in Tables VIII and IX, were obtained
and calculated on a basis of 50 hills for both the number and weight
of the tubers. These calculations indicate that although decreases
in yield occurred in both treated samples, they were about 3 times
as great by weight in prime tubers where semesan bel was used
as in the sample treated with corrosive sublimate. It is to be
emphasized that these results, obtained under extreme conditions,
and here reported are given only because of their interest with
reference to the conflicting factors involved. They refer to the
trials of one year only and it is not known what the possibilities
are of duplicating them.
Tables X and XI show the results of another plot in the Federal
Point section planted later than the one discussed above. In this
plot corrosive sublimate, two strengths of dipdust, and semesan
bel were paired in 3 direct comparisons with untreated controls.
All of the tubers treated were unsorted "bag run" stock, on about
half of which was found a medium number of small sclerotia. No
disease was observed in any part of these plots, and the seed pieces
were sound at digging time. The yield, both in weight (Table X)
and number of tubers (Table XI), indicate fairly significant in-
creases for primes and marketable tubers where corrosive subli-
mate was used; insignificant decreases, for dipdust 1:16 and
semesan bel, and significant decreases for dipdust 1:24. There
might have been less inconsistency in the results if more than 3
replications had been planted per treatment, but viewing these
results in the light of previous and later experiments this seems
rather questionable.
The plot in the Hastings sections consisted of six direct com-
parisons with the untreated controls. The treatments used were
dipdust 1:20, dip; dipdust (Bayer special) 181, 1:40 dip; and
semesan bel 1:20 dip. Each lot was planted in alternate rows 50
feet long. This experiment was conducted exactly as a commercial
grower would conduct it. The different unsorted, "bag run" lots,
showing only a trace of sclerotia were treated a half day after
cutting and immediately before planting with an automatic picker
planter. Observations were made as before. No rhizoctonosis
symptoms were observed at any time and the stands were as
perfect as they could be with this type of planting. There was no
difference in rate of germination or relative vigor of the plants.
At digging, representative sample plots 50 feet long were dug by
hand, graded and weighed. Treatments with dipdust, Bayer
special 181, and semesan bel produced significant increases in yield










to

TABLE VIII.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE YIELD OF POTATOES IN A BADLY FROZEN PLOT AT FEDERAL
POINT, FLORIDA, IN 1927.

CalculatedPounds Increase by Treating
SNo. of Tubers per 50 Hills Pounds Percent I Calculated Odds XJ
Treatments Repli- When ---
cations Treated Primes Seconds Primes Seconds Primes Seconds Primes Seconds
*Diseased-untreated... .................. 6 22.2 8.78 .... ... ... ... .. ....
Corrosive sublimate....................... 6 Whole 20.3 6.97 -1.9 -1.81 -8.6 -20.6 5.36:1 10.2:1

Diseased-untreated...................... 6 22.2 8.78 .... ... .. ....
SemesanBel. 1:10dip ..................... 6 Cut 16.7 5.88 -5.5 -2.90 -24.8 -33.0 18.9:1 199:1


*The untreated lots were taken directly from the bag without sorting and on about half of the tubers could be found a
small number of small sclerotia.

TABLE IX.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE NUMBER OF POTATOES PRODUCED IN A BADLY FROZEN PLOT AT
FEDERAL POINT, FLORIDA, IN 1927.

Calculated Increase by Treating
No. of Tubers No. of Tubers
Tubers Percent Calculated Odds
Treatments Repli- When per 50 Hills Tubers percent Calculated Odds
cations Treated Primes Seconds Primes Seconds Primes Seconds Primes Seconds
Diseased-untreated....................... 6 115.6 105.6 .... .... .... .... .... ....
Corrosive sublimate....................... 6 Whole 108.8 78.7 -6.8 -26.9 -5.9 -25.5 3.24:1 38.7:1 .

Diseased-untreated ....................... 6 115.6 105.6 .... .... ..
Semesan Bel. 1-10 dip....................... 6 Cut 85.5 66.8 -30.1 -38.8 -26.0 -36.8 29.1:1 1,666:1








Bulletin 220, Effect of Seed Potato Treatment 23

of prime tubers over the untreated lots of 23.8, 10.3 and 16.1 per-
cent respectively, as shown in Table XII. Increases, the first for
this entire series of experiments as consistent as these, are con-
sidered ideal from the viewpoint of the advocate of seed potato
treatment with organic mercury compounds. However, since no
disease was observed it would have been interesting to have the
comparisons of an untreated control with a sample dipped in
water only.
THE EXPERIMENTS IN 1928
Experimental plots, consisting of rows 50 feet long, were con-
ducted in the Federal Point, Hastings, and Elkton sections as in
1927. The tubers used were taken directly from a commercial
shipment, unsorted, and they showed only mild symptoms of
rhizoctonosis. Plot No. 1, planted December 15, consisted of 10
direct comparisons each of Bayer special 181, 1:40 dip; dipdust,
1:20 dip; and untreated controls.
The percentage stands, seed-piece decay, and relative vigor, for
this plot are as follows:
Bayer Special
181 Dipdust Untreated
Stand .......................... 83 86 97
Decaying in seed piece ........... 18 21 0
Relative vigor ................... 85 85 100

This is the first injury which the writer has observed from the
use of organic mercury compounds, although several instances had
been reported in 1927 from other sections of the state where the
manufacturers and guarantors of semesan bel paid for large losses
because of complete seed-piece decay following planting with seed
stock given this treatment.
In plot No. 2 at Hastings, 7 direct comparisons were made with
semesan bel, 1:20 dip; dipdust, 1:20 dip; "samenkraft" 1:25 soak
45 minutes; corrosive sublimate, and untreated controls. In plot
No. 3 at Elkton, 8 comparisons similar to those in plot No. 2 were
made, with the exception of corrosive sublimate which was not
used. Samenkraft was a secret preparation manufactured at
Green Cove Springs, Florida, and tooted as a "powerful pest de-
stroyer and plant stimulant". It was somewhat quickly accepted
by a number of planters but proved to have no special value. It
was manufactured one year only.
Careful observations throughout the season revealed practically
perfect stands, and no differences in relative vigor of the plants
in the differently treated samples. There was no seed-piece decay,





TABLE X.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE YIELD OF POTATOES AT FEDERAL POINT, FLORIDA, IN 1927.

Calculated Yields** Increase by Treating
Barrels per Acre Barrels Percent Calculated Odds
TreatmentsMarket- Market- Market- Market-
Primes Seconds able Primes Seconds able Primes Seconds able Primes Seconds able
Diseased-untreated............ 38.6 13.2 51.8 .... .. .
Corrosive sublimate............. 46.9 14.0 60.9 8.3 0.8 9.1 21.5 6.3 17.6 13.5:1 2.85:1 23.1:1

Diseased-untreated............ 48.3 13.4 61.7 .. ....... .... .... .... .... .... .
Dipdust, 1-24 dip................ 38.4 16.5 54.9 -9.9 3.1 -.8 -20.5 23.1 -11.0 293.0:1 31.2:1 37.9:1

Diseased- untreated............ 40.3 15.0 55.3 .... . .... .... .... .... .... .... .
Dipdust, 1-16 dip............... 34.1 12.9 47.0 -6.2 -2.1 -8.3 -15.4 -14.0 -15.0 3.99:1 25.9:1 7.1:1

Diseased-untreated............ 50.2 12.6 62.8 .. .... . .... .... ....
Semesan Bel. 1-10 dip........... 42.2 13.8 56.0 -8.0 1.2 -6.8 -15.9 9.5 -10.8 7.13:1 2.62:1 6.6:1 .
*All of the tubers for the different lots were taken directly from the bags without sorting and on about half of the tubers were
found a medium number of small sclerotia; all lots were treated after cutting except where corrosive sublimate was the treat-
ment used.
"**Each yield represents the average of 3 replications.

TABLE XI.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE NUMBER OF POTATOES PRODUCED AT FEDERAL POINT, FLORIDA, IN 1927.

Calculated Increase by Treating
No. of Tubers Stand No. of Tubers _
Treatments* Repli- When Percent per 50 Hills Tubers Percent Calculated Odds
cations Treated Primes Seconds Primes Seconds Primes Seconds Primes Seconds -

Diseased-untreated............. 3 99.2 113.8 94.7 .... .... .. .. ....
Corrosive sublimate .............. 3 W 97.2 147.4 98.7 33.6 4.0 29.5 4.2 29.0:1 2.39:1

Diseased-untreated.............. 3 92.0 152.7 96.2 .... .... ... .... .... ....
Dipdust, 1-24 dip................. 3 C 95.2 117.2 114.5 -35.5 18.3 -23.3 19.0 9,999.0:1 51.1:1

Diseased-untreated.............. 3 96.6 130.2 104.4 ... ... ..
Dipdust, 1-16 dip ............... 3 C 88.6 109.7 94.9 -20.5 -9.5 -15.7 -9.1 3.69:1 6.69:1

Diseased-untreated .............. 3 97.2 156.5 86.4 ... ... ..
Semesan Bel. 1-10 din............. 3 C 99.2 134.8 94.0 -21.7 7.6 -13.9 8.8 9.16:1 2.85:1
*No scab or appreciable amount of rhizoctonia, either in the form of stem lesions, "rhizoctonia hills", or sclerotia on the
tubers were observed in the plot, and practically all of the seed pieces were sound at digging time.







Bulletin 220, Effect of Seed Potato Treatment 25

nor were there any symptoms of rhizoctonosis in either the treated
or untreated lots. Table XIII, which shows the results for the
three plots conducted in 1928, indicates that significant injury
resulted in the early planted plots from both Bayer special 181,
and dipdust, and that the latter and semesan bel likewise caused
slight injury in the Hastings plot which was planted later. Very
slight and insignificant increases are noticed for all of the other
treatments in the 3 plots.

THE EXPERIMENTS IN 1929
The treated and untreated lots were planted according to the
plan shown in Fig. 5. This scheme provides for excellent distri-
1 2 3 4 5 6 7
2 4 1 6 3 7 5
3 1 5 2 7 4 6
4 6 2 7 1 5 3
5 3 7 1 6 2 4
6 7 4 5 2 3 1
7 5 6 3 4 1 2
Fig. 5.-The planting plan for the seed-potato treatment plots in Hastings
and La Crosse, Florida, in 1929.

bution of the different lots, eliminates the necessity of having as
many untreated controls as were used before, and provides for
satisfactory biometrical measurements with fewer plants per
replication. The seed stock was carefully selected and sorted, after
being wetted to make the sclerotia more distinct, into two lots
where the tubers were either all sclerotia-free, or all with sclerotia,
and treated according to the usual procedure and as indicated in
Table XIV. Two separate experiments were planted, one in the
Hastings area and the other at La Crosse, 45 miles west, in a field
where 75 percent of the plants manifested severe rhizoctonosis
injury in 1928. The highest percentage of stem lesions were found
in the diseased controls, followed by the dipdust and formaldehyde
treated lots at La Crosse, and in the diseased untreated, diseased
corrosive sublimate treated, and the clean untreated lots in the
Hastings trials. The only appreciable amounts of seed-piece decay
in both experiments occurred where dipdust was used.
The material, K-I-X, a DuBay product, used only in a very
preliminary way, was applied directly to the soil at the rate of 50

















TABLE XII.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE YIELD OF POTATOES AT HASTINGS, FLORIDA, IN 1927. .
Calculated Yields** Increase by Treating
Barrels per Acre Barrels Percent Calculated Odds
Treatments* Market- Market- Market- Market- 3
Primes Seconds able Primes Seconds able Primes Seconds able Primes Seconds able c
Diseased-untreated....... . 55 15.9 71.4 ... .. .... .... .... .... .... ..
Dipdust, 1-20 dip............... 68.7 15.6 84.3 13.2 -0.3 12.9 23.8 -1.9 18.0 109.0:1 1.4:1 44.9:1
Diseased-untreated.......... 64.2 16.4 80.6 .... ... ... ... ..
Dipdust, 181, 1-40 dip. ......... 70.8 14.0 84.8 6.6 -2.4 4.2 10.3 -14.6 5.2 98.0:1 34.0:1 58.5:1
Diseased-untreated ........... 62.1 18.8 80.9 ... ... .. ....
Semesan Bel. 1-10 dip .......... 72.1 13.8 85.9 10.0 -5.0 5.0 16.1 -26.6 6.2 138.0:1 302.0:1 10.2:1

*All of the tubers for the different lots were taken directly from the bags, and none showed more than a trace of rhizoctonia
sclerotia; all lots were treated after cutting except where corrosive sublimate was the treatment used.
**Each yield represents the average of 6 replications.







Bulletin 220, Effect of Seed Potato Treatment 27

pounds per acre. It was first thoroughly mixed with fine sand,
then scattered in uniform amounts in the furrow and covered to
a depth of about 1/3 inch. The seed pieces were planted immedi-
ately on top of this, but not in contact with the disinfectant, and
covered as usual. The injury, which was extremely severe, took
the form of retardation of germination and growth. Frequently
the sprouts were extremely short and thick, and in many instances
germination was totally inhibited. It is probable that if the ma-
terial had been thoroughly mixed and applied with the fertilizer
the injury might have been less severe, but regardless of the man-
ner of application it is apparently exceedingly dangerous and re-
quires thorough experimentation and modification.
In these plots no sclerotia were observed on the tubers at digging
time. In the Hastings plot the diseased untreated sample con-
sistently outyielded those of all the other treatments, while in the
La Crosse experiment the diseased controls were outyielded,
though not significantly, by hot formaldehyde, and by the clean
and diseased corrosive sublimate treated lots.

DISCUSSION OF RESULTS IN FLORIDA
The treatment of seed potatoes as reported herein yielded results
which are rather consistent with the amount of rhizoctonosis
usually prevalent in this section, and with results obtained in some
other sections. Corrosive sublimate is usually considered favorable
only for the control of this particular disease and scab and not
for stimulating plant growth. With the insignificant amount of
rhizoctonosis injury in most of the plots, outstanding results could
hardly be expected. Significant increases were demonstrated but
once, and these in the very early planted section in the absence of
disease.
Clayton(13), Schultz et al.(79), and others occasionally report
increases in yield by the use of organic mercury compounds, even
where disease is not effectively controlled. Reasoning from their
conclusions one could expect good increases in yield from the use
of these materials especially where disease was a negligible factor.
In the Florida experiments, however, with all of the different
forms of these materials used, and throughout the large number
of replications, the differences were usually not significant. Sev-
eral times the yields were significantly less, and in but one or two
instances were they significantly more than those from the un-
treated controls.












TABLE XIII.-EFFECT OF DIFFERENT SEED TREATMENTS ON THE YIELD OF POTATOES IN THE HASTINGS, FLORIDA, POTATO SECTION IN 1928.

Calculated Yields Increase by Treating
Date No. of Barrels per Acre Barrels | Percent | Calculated Odds
No. Plan ting Repli- Market- Market- MI arket- Market-
cations Primes Seconds able Primes Seconds able Primes Seconds able Primes Seconds able

Bayersp. No. 181,1-40, dip 10 36.7 9.2 45.9. .
1 Dec.15 Diseased-untreated ..... 10 40.3 11.3 51.6 -3.6 -2.1 -5.7 -8.9 -18.6 -11.01 6.67:1 61.1:1 22.5:1

Dipdust, 1-20, dip........ 10 35.5 9.9 45.4 .... .... .
Diseased-untreated ..... 10 41.7 11.1 52.8 -6.2 -1.2 -7.4 -14.9 -10.8 -14.0 11:1 4:1 8:1

Semesan Bel. 1-20, dip... 7 63.9 17.7 81.6 .... .... ..
Diseased-untreated ..... 7 65.4 15.2 80.6 -1.5 2.5 1.0 -2.3 16.5 1.2 2:1 23:1 1:1
2 Jan. 8 Dipdust, 1-20, dip ....... 7 72.0 16.4 88.4
Diseased-untreated.... 7 72.0 22.7 94.7 0.0 -6.3 -6.3 0.0 27.7 -6.7 0 104:1 32:1

Samenkraft, soak........ 7 71.0 17.4 88.4. ...
Diseased-untreated..... 7 70.1 18.0 88.1 0.9 -0.6 0.3 1.3 -3.3 0.34 23:1 3:1 4:1

Corrosive sublimate...... 7 74.3 17.8 92.1 .. .... .... .
Diseased--untreated..... 7 71.3 17.1 88.4 3.0 0.7 3.7 4.2 4.1 4.2 3:1 1:11 4:1

Semesan Bel. 1-20, dip. .. 8 95.3 13.1 108.4
3 Jan. 22 Diseased-untreated..... 8 92.5 12.8 105.3 2.8 0.3 3.1 3.0 2.3 2.9 2:1 0

Dipdust, 1-20, dip. ....... 8 94.2 13.3 107.5 ..
Diseased-untreated..... 8 92.5 12.8 105.3 1.7 0.5 2.2 1.8 3.9 2.1 0 0 1:1

Samenkraft, soak....... 8 91.0 15.5 106.5
Diseased--untreated ..... 8 92.5 12.8 105.3 -1.5 2.7 1.2 -1.6 21.1 1.1 0 9,999:1 0








TABLE XIV.-EFFECT OF DIFFERENT SEED TREATMENTS ON YIELD OF POTATOES IN FLORIDA IN 1929.
Percent Marketable Tubers Primes Only
Tubers* Percent Relative Seed- Percent Yield: Increase by Treating Yield Increase by Treating
Treatments When Stand Vigor Piece Stem per Acre per Acre
Treated Decay Lesions
Treated Decay esions Barrels Barrels Percent Oddst Barrels Barrels Percent Oddst

(PLOT 1) HASTINGS
Clean-not treated ...................... 100 95.4 0.0 5.0 65.12.11 -3.73.11 -5.44.5 139:149.5+2.35 -4.6+3.63 -8.5+6.7 1.63:1
Clean-corrosive sublimate......... W 100 97.4 0.0 3.3 67.22.43 -1.63.33 -2.34.8 0 52.82.23 -1.33.56 -2.46.6
Diseased-corrosive sublimate ..... W 100 98.8 1.6 5.0 65.72.48 -3.13.37 -4.54.9 1:151.6+2.76 -2.5+3.91 -4.6+7.2 ....
Formaldehyde, 1-120,1250F.-3 min. W 100 97.8 0.0 1.6 68.72.61 -0.13.47 -0.1+5.0 0 53.0+2.57 -1.13.78 -2.07.0 ....
Dipdust, 1-20 dip ................ C 73.3 79.2 83.3 1.6 40.72.14-28.1+3.13-40.84.5 **M:1 32.12.20-22.0+3.54-40.16.519,230:1
K-I-X, at 50 pounds per acre............. 24.1 64.8 0.0 0.0 11.7+1.21-57.12.58-83.03.8 M:l 9.41.01-44.72.95-82.85.4 M:l
Diseased- untreated................. .... 100 98.8 0.0 26.6 68.8+2.28 ......... ...... .... ....54.1+2.77 ......... ........ ....

(PLOT 2) LA CROSSE
Clean-not treated. ...................... 99.2 96.2 0.0 2.0 79.23.20 -1.9+4.33 -2.35.3 0 64.73.23 -1.5+4.60 -2.36.9 ..
Clean-corrosive sublimate......... W 97.2 97.2 0.0 2.0 83.13.07 2.04.24 2.55.2 0 70.23.52 4.04.80 6.0+7.3 1:1
Diseased-corrosive sublimate ..... W 99.0 98.0 0.0 2.0 82.7+5.24 1.66.00 2.07.4 0 67.85.63 1.66.51 2.4+9.8
Formaldehyde, 1-120,1250F.-3 min. W 99.0 97.8 0.0 9.0 85.84.93 4.75.73 5.87.1 1:169.1+5.19 2.9+6.13 4.4+9.3 .
Dipdust, 1-20, dip................ C 97.0 97.2 10.0 11.0 81.03.90 -0.14.87 -0.1- 6.0 0 64.64.48 -1.6+5.55 -2.48.4 ..
K-I-X, at 50 pounds per acre............. 32.6 56.0 2.0 trace 20.4+1.49 -60.73.28-74.84.0 M:1 17.0+1.26-49.23.50-74.35.3 M:l
Diseased- not treated ............ ........ 98.2 97.5 0.0 18.0 81.12.92 ......... 66.2+3.27 ......... ......... ....

*W = whole tubers treated; C = tubers treated after cutting. **Million or more to one.
tData calculated according to formula: PEm = .6745 x Standard deviation. $Average of 10 replications.
VNo. of items. PEd = V a2 + b2 where a = PE of mean of treated lot and
Odds as listed in: Pearl, Raymond and John Rice Miner:-A table for b = PE of untreated diseased control.
estimating the probable significance of statistical constants. Maine Agr.
Exp. Sta. Bul. 226: 85-88, 1914.







30 Florida Agricultural Experiment Station

CONCLUSIONS
The numerous decreases, and the few significant increases in
yield which resulted from the treatments throughout this series
of experiments indicate that treatment with corrosive sublimate
in the Hastings potato belt is unwarranted. Two well replicated
trials in 1929 gave similar indications for hot formaldehyde.
No yield increases, and positive indications of definite injury
in these experiments, accentuated by some losses suffered by
commercial growers elsewhere within the state from the use of
organic mercury compounds, emphasize the inadvisability of treat-
ing seed potatoes in Florida on a commercial scale with these newer
compounds, until their safety and advantages have been demon-
strated.
The addition of materials to the soil for the control of rhizocto-
nosis of potatoes in the Hastings potato belt, disastrous in the
trials of one year, has not been investigated sufficiently to warrant
conclusions.
SUMMARY
Grouping and tabulation of the average percentage losses over
a 10-year period in yields of potatoes because of rhizoctonosis
(Corticium vagum B. & C.) indicate that this disease is not neces-
sarily most severe in the northern-most states, although the south-
ern states suffer very little injury.
A summary of the most recent publications reveals that although
great efforts have been put forth to improve seed treatment
methods, either by decreasing the time of treatment, and increas-
ing the temperature, or by the use of new materials, 27 states still
adhere to the use of cold corrosive sublimate, 5 advocate the use
of hot formaldehyde only, 4 consider these two materials equally
efficient, only 2 definitely recommend the use of organic com-
pounds, 3 suggest either the new compounds or the old standard
formula, and 2 suggest the modification of the latter either by
adding an acid or by increasing the temperature, while 4 have no
recommendations to offer.
Seed potato treatment experiments in the Florida potato belt,
conducted for over a half decade, indicate that such treatments on
a commercial scale with either corrosive sublimate, hot formalde-
hyde, or organic mercury compounds are not justified.









Bulletin 220, Effect of Seed Potato Treatment 31

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