Dust treatments for vegetable seed

Material Information

Dust treatments for vegetable seed
Series Title:
Bulletin University of Florida. Agricultural Experiment Station
Tisdale, W. B ( William Burleigh ), 1890-
Brooks, A. N ( Albert Nelson )
Townsend, G. R ( George Richard ), 1905-
Place of Publication:
Gainesville Fla
University of Florida Agricultural Experiment Station
Publication Date:
Physical Description:
32 p. : ; 23 cm.


Subjects / Keywords:
Vegetables -- Diseases and pests -- Control -- Florida ( lcsh )
Vegetables -- Seeds ( lcsh )
Vegetables -- Fumigation -- Florida ( lcsh )
non-fiction ( marcgt )


General Note:
Cover title.
Bulletin (University of Florida. Agricultural Experiment Station)
Statement of Responsibility:
W.B. Tisdale, A.N. Brooks and G.R. Townsend.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
027119020 ( ALEPH )
18237097 ( OCLC )
AEN5871 ( NOTIS )


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Full Text

August, 1945





Fig. 1.-Treated seed yield better stands of plants. Lettuce seed treated
with arasan (1), fermate (2), spergon (3), or in sterilized soil (4) all gave
better stands than nontreated seed (5) or seed treated with cuprocide (6).

Single copies free to Florida residents upon request to

Bulletin 413


N. B. Jordan, Acting Chairman, Quincy
Thos. W. Bryant, Lakeland
M. L. Mershon, Miami
J. Henson Markham, Jacksonville
J. Thos. Gurney, Orlando
J. T. Diamond, Secretary, Tallahassee


John J. Tigert, M.A., LL.D., President of the
H. Harold Hume, D.Se., Provost for Agricul-
Harold Mowry, M.S.A., Director
L. 0. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.'
J. Francis Cooper, M.S.A., Editors
Clyde Beale, A.B.J., Associate Editor3
Jefferson Thomas, Assistant Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, LL.D., Business Managers
Claranelle Alderman, Accountants



W. E. Stokes, M.S., Agronomist'
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Agronomist2
G. B. Killinger, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
Roy E. Blaser, M.S., Associate
H. C. Harris, Ph.D., Associate
R. W. Bledsoe, Ph.D., Agronomist
Fred A. Clark, B.S., Assistant

A. L. Shealy, D.V.M., An. Industrialist1
R. B. Becker, Ph.D., Dairy Husbandman3
E. L. Fouts, Ph.D., Dairy Technologists
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarians
L. E. Swanson, D.V.M., Parasitologist'
N. R. Mehrhof, M.Agr., Poultry Husb.3
G. K. Davis, Ph.D., Animal Nutritionist
T. R. Freeman, Ph.D., Asso. in Dairy Mfg.
R. S. Glasscock, Ph.D., An. Husbandman
D. J. Smith, B.S.A., Asst. An. Husb.'
P. T. Dix Arnold. M.S.A., Asst. Dairy Husb.8
C. L. Comar, Ph.D., Asso. Biochemist
L. E. Mull, M.S., Asst. in Dairy Tech.'
J. E. Pace, B.S., Asst. An. Husbandman '
S. P. Marshall, M.S., Asst. in An. Nutrition4
Ruth Taylor, A.B., Asst. Biochem.
Katherine Boney, B.S., Asst. Chem.
Peggy R. Lockwood, B.S., Asst. in Dairy Mfs.


C. V. Noble, Ph.D., Agr. Economist'
Zach Savage, M.S.A., Associates
A. H. Spurlock, M.S.A., Associate
Max E. Brunk, M.S., Associate


Ouida D. Abbott, Ph.D., Home Econ.'
R. B. French, Ph.D., Biochemist


J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D., Associate3
H. E. Bratley, M.S.A., Assistant


G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Asso. Horticulturist
F. S. Jamison, Ph.D., Truck Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.
J. Carlton Cain, B.S.A., Asst. Hort.'
Victor F. Nettles, M.S.A., Asst. Hort.4
Byron E. Janes, Ph.D., Asst. Hort.
F. S. Lagasse, Ph.D., Asso. Hort.2


W. B. Tisdale, Ph.D., Plant Pathologist'
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist


F. B. Smith, Ph.D., Microbiologist'1
Gaylord M. Volk, M.S., Chemist5
J. R. Henderson, M.S.A., Soil Technologist
J. R. Neller, Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
L. H. Rogers, Ph.D., Associate Biochemist4
R. A. Carrigan, B.S., Asso. Biochemist
G. T. Sims, M.S.A., Associate Chemist
T. C. Erwin, Assistant Chemist
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Microbiologists
R. E. Caldwell, M.S.A., Asst. Soil Surveyor'
Olaf C. Olson, B.S., Asst. Soil Surveyor4

1 Head of Department.
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4 In Military Service.
5 On leave.



J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
V. E. Whitehurst, Jr., B.S.A., Asst. An.
Jesse Reeves, Asst. Agron., Tobacco
W. H. Chapman, M.S., Asst. Agron.'
R. C. Bond, M.S.A., Asst. Agronomist

Mobile Unit, Monticello

R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Milton

Ralph L. Smith, M.S., Associate Agronomist

Mobile Unit, Marianna

R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka

J. B. White, B.S.A., Asso. Agronomist


A. F. Camp, Ph.D., Vice-Director in Charge
V. C. Jamison, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Entomologist
W. W. Lawless, B.S., Asst. Horticulturist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
H. O. Sterling, B.S., Asst. Horticulturist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Asso. Horticulturist6
J. B. Redd, Ph.D., Insecticide Chemist


R. V. Allison, Ph.D., Vice-Director in Charge
J. W. Wilson, Sc.D., Entomologist'
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S., Asst. An. Hush.
W. T. Forsee, Jr., Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Eng.2
F. S. Andrews, Ph.D., Asso. Truck Hort.'
R. A. Bair, Ph.D., Asst. Agronomist
E. L. Felix, B.S.A., Asst. Plant Path.


Geo. D. Ruehle, Ph.D., Vice-Director in
P. J. Westgate, Ph.D., Asso. Horticulturist
H. I. Borders, M.S., Asso. Plant Path.


Clement D. Gordon, Ph.D., Asso. Poultry
Geneticist in Charge2


W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Asso. Agron.
Gilbert A. Tucker, B.S.A., Asst. An. Hush.'



G. K. Parris, Ph.D., Plant Path. in Charge

Plant City

A. N. Brooks, Ph.D., Plant Pathologist


A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Truck Horticulturist


S. O. Hill, B.S., Asst. Entomologist2 4
A. M. Phillips, B.S., Asst. Entomologist2


J. R. Beckenbach, Ph.D., Horticulturist in
E. G. Kelsheimer, Ph.D., Entomologist
A. L. Harrison, Ph.D., Plant Pathologist
David G. Kelbert, Asst. Plant Pathologist
E. L. Spencer, Ph.D., Soils Chemist


R. W. Ruprecht, Ph.D., Chemist in Charge
J. C. Russell, M.S., Asst. Entomologist6


E. S. Ellison, Meteorologist 2
Warren 0. Johnson, Meteorologist2

SHead of Department.
2In cooperation with U. S.
I Cooperative, other divisions, U. of F.
*In Military Service.
I On leave.


INTRODUCTION ................- ......-...............-...- ............ ..... 5
PURPOSE OF SEED TREATMENTS ............................ ............- 6
PROCEDURE .............................. .................. 7
RESULTS ...... .... -. .......- .......- .......... .......... -.. .... ............ 9
Bean (Lima) ..........---..-............... ......- .................... 10
Bean (Snap) ............................... .. ............ 12
Beet .................. ...................... ...... .................. ....... 13
Broccoli ............. .... --... ................... ................... .......... 14
Brussels Sprouts ....... ............. ............. .......................... 14
Cabbage ........................... ......... .. .. ...... .. .......... 14
Carrot ................ ... ......-......--............... ................... 16
Cantaloupe ..... ......... ....... .. .. .. .... ............ ............ ....... 16
Cauliflower ..-................ ....... .............. .. ...................... 17
Celery ........................ .................... ......... .................... 17
Cucumber .....--........ ..... ..----- ....-----.......... ................... 17
Eggplant ..---........ .................................. ................ 18
Escarole .............-....... ........... ... ....... 18
Lettuce .......-...--.... .................................. 18
Mustard .......-........... ...... .......................... ............. 20
Pea (English) .............. ........................... ..................... 20
Pepper ... ........... .......................... ....... .............. ..... 21
Spinach ..........-- ... --.... ---...--.............. -............ 23
Sweet Corn .......... .. ......... ....... .... .- .......... ...................... 26
Tomato ................--- .............................................. ...... 27
Turnip ...... .............-- ... ... .....- ..... .... ...... ......... 27
Watermelon .....-- ............ .......................... .. ...................... 28
TREATING THE SEED .........-................. ............. ........ .. ....................... 28
Summary of Treatments Recommended for Different Seed............. 29
DISCUSSION ..................... ............... 30
PRECAUTIONS .......-........................ ........ ................................31


Seed treatments have been used for many years to combat
certain diseases of plants that are caused by parasitic seed-
borne organisms. The treatments commonly used for this pur-
pose are hot water, formaldehyde, bichloride of mercury and
some of the organic mercury compounds. Some of the newer
seed-treatment materials also have provided protection against
these diseases. In recent years the importance of many seed-
borne diseases has been greatly reduced by growing the seed
in semi-arid areas of the country or by employing cultural prac-
tices that permit the production of seed that are comparatively
free of disease-producing organisms. With the use of these
two methods of control, damage caused by seed-borne diseases
has become of minor importance with most crops.
Although soil-inhabiting organisms have long been known
to cause diseases of seed and seedlings, little progress was made
in devising methods for reducing the damage caused by these
parasites until the last decade. Diseases caused by this group
of parasites are apparently becoming more prevalent and im-
portant in crop production, especially in localities where the land
is planted to the same kind of crop year after year. If seed
are planted in soils infested with these organisms when con-
ditions are favorable for their activity, poor stands or occasion-
ally even complete failures result. Steam, hot water and for-
maldehyde solutions have been used more or less successfully
for years to rid small amounts or areas of soil of parasitic
organisms. However, because of the high cost of treating soil
with these agents and the chances for reinfestation of outside
areas after treatment, they have been used on a field scale only
for certain crops of sufficient value to justify the expense of
repeated treatments.
It was early recognized that the chemicals which left a resi-
due on the seed when they were treated for controlling seed-
borne diseases also furnished some protection against some of
the diseases caused by soil-inhabiting organisms. Chemicals
which provided such protection were given the name "seed pro-
tectants," and this term is still in use. With this information
serving as a background, many chemicals have been tested as

Florida Agricultural Experiment Station

seed protectants during the last decade in various states and
as a result a voluminous literature has appeared on the subject.
Beneficial results obtained have encouraged the manufacture
of other seed-treatment chemicals and further experimentation
with them. Although satisfactory materials and methods for
their use have been developed in several states, results obtained
by experimental workers and growers show that the materials
which have proved most satisfactory for a given variety of seed
in one state are not necessarily the best for the same variety
in other states or even in different localities of the same state.
Furthermore, some of the materials have proved to be better pro-
tectants against certain seed-decaying organisms than against
others. This emphasizes the fact that the problem is not a
simple one. Consequently, to obtain the most benefit from seed
treatments it is necessary to demonstrate their value for each
variety of seed in each locality. Some of the factors which ap-
pear to influence their effectiveness are soil type, reaction, tem-
perature and moisture, the disease-producing organisms present
and the variation among varieties of seed to injury by the
To obtain answers to some of these questions, experiments
were begun about 5 years ago to determine which of the avail-
able seed-treatment materials are most beneficial in preventing
seed decay of the principal vegetable crops grown in various
localities of Florida. Although the work as originally planned
has not been completed, it seems advisable to make available
to growers the information obtained. This information should
be of considerable benefit to the growers, enabling them to
select the best material for each variety or locality and to pro-
duce more plants from the seed sown. It also should be bene-
ficial to the seedsmen because if farmers and gardeners use the
information there should be fewer complaints on germination of
Recommendations are made for certain other important crops,
although no experimental tests have been performed with them
in Florida. However, several of these crops are members of
the same families as the ones tested, and it seems probable that
they will respond to treatments in a similar manner, and recom-
mendations are made on this basis.
The seed treatments described in this bulletin are recom-
mended to prevent seed decay and death of young seedlings

Dust Treatments for Vegetable Seed

before they emerge from the soil. This type of disease is tech-
nically known as pre-emergence damping-off, and the result is
poor stands. The grower usually attributes this phase of the
disease to low viability of seed, whereas it is more often due
to decay of good seed. The other phase of damping-off is known
as post-emergence damping-off. Both phases may be caused
by one or more organisms.
The post-emergence phase of damping-off becomes manifest
at any time after the seedlings emerge from the soil, provided
the causal organisms are present and conditions are favorable
for their activity. It is recognized on young, tender plants as
a water-soaked, collapsed condition of the stems at the ground
line, followed by sudden wilting and death of the plants. If
the plants are attacked after they become older or when condi-
tions are less favorable for activity of the parasite, the disease
advances less rapidly. Leaves of affected plants turn darker
green than those of healthy plants and brown lesions may be
found on the stems and taproots. The leaves may turn yellow
later and the plants become stunted and are usually unproductive
if they do not die. Seed treatments offer little protection against
this phase of damping-off and are not recommended for this
The fungus Rhizoctonia has been found most commonly asso-
ciated with this phase of the disease in the field, and pure cul-
tures of it produced the disease in the greenhouse. However,
different cultures of the fungus showed varying degrees of
pathogenicity and a tendency to become less pathogenic on arti-
ficial media. Another fungus, Pythium, was obtained from dis-
eased plants in 2 field tests, and the few greenhouse tests
performed with pure cultures of it proved that it was lcaabl
of causing a high percentaggQof edAdecay of certain crops.

The experiments were designed to evaluate several seed-treat-
ment materials for preventing the pre-emergence phase of
damping-off under Florida conditions. The tests were performed
in infested and noninfested soil in pots and flats in greenhouses
at Gainesville and Plant City and in the field in several localities
of the state. Soil used for the field experiments had been in
cultivation for several years and offered the possibility of being
infested with seed-decaying organisms. In some field tests the
soil was artificially infested with pure cultures of Rhizoctonia to

Florida Agricultural Experiment Station

increase the chances for damping-off to develop. Crops tested
in certain localities were the ones commonly grown there and the
seed were planted during the season the farmers usually plant
them. At Gainesville and Plant City, however, tests were per-
formed at different seasons to determine the effects of soil tem-
perature and other factors upon the comparative value of the
treatment materials.
Artificially infested potting soil was used for most of the ex-
periments performed in the greenhouse and in some cases similar
tests were run simultaneously at different soil temperatures.
Several varieties of seed were treated and planted in sterilized
soil to determine the extent of direct injury to the seed by the
chemicals. Soil reaction and organic content also were varied in
the same soil type to ascertain the influence these factors may
have on seed decay, on the value of treatment materials in pre-
venting it and on the harmful effects certain materials may have
on germinating seed. In all greenhouse experiments, except
where otherwise stated, the soil was first treated with formalde-
hyde or chloropicrin or electrically heated and then infested
with pure cultures of the fungus immediately before or at the
time of planting the seed.
The materials used were chemicals prepared and recommended
by the manufacturers for treating seed. Most of them are on
the market, while the others were distributed for experimental
purposes. All of them were applied as dusts to dry seed before
they were planted. At the outset, as much of the chemicals
were applied as the seed would retain, which is considered "full
dosage". In subsequent tests the materials were weighed and
applied to known weights of the seed to give dosages of various
percentages. The materials were applied by placing the seed
and chemical together in a container of suitable size, closing
the container and then rolling or shaking to assure uniform
distribution of the material over the seed. The desired numbers
of seed were then counted out for the desired number of replica-
tions, placed in packets and the small lots were planted without
touching with the hands. Beans and lima beans planted in the
field were planted by hand or with a mechanical planter.
The seed used in all of the tests were commercial lots pur-
chased from local seed dealers. New lots were used each year
and in some cases more than one variety of each crop was used.
There were differences in viability of the various lots of seed,

Dust Treatments for Vegetable Seed

and this apparently accounts for some of the variations in effec-
tiveness of the treatments.
In practically all of the outdoor tests it was necessary to water
the beds to encourage germination. This is common practice
of the growers during the fall and spring and, therefore, should
give results comparable with those they would obtain.
All of the field and greenhouse experiments were so designed
that the results could be evaluated by the statistical method
known as analysis of variance; the particular design used in
each case was determined by the number of treatments and
varieties involved. The seed were planted in randomized plots
with 5 or more replications in most tests. In all experiments
the differences between means were considered "significant"
when the odds were 19:1 and "highly significant" when the odds
were 99:1. These differences are referred to in some instances
as better or best. Differences with odds less than 19:1 are
referred to in some cases as being "slightly better". This com-
parison, of course, is made between treated and nontreated and
between materials and dosages. The ultimate object was to
determine the minimum dosage of the most effective treatment-
materials required to provide maximum protection to the seed
of each crop. To obtain this information numerous experiments
were conducted, but all of the tests have not been repeated under
the various conditions. Emergence counts were used in all tests
as a measure of the performance of the treatments. Results
of these tests serve as a basis for the recommendations made
in this bulletin.

Results obtained from seed treatments of most crops varied
considerably with the different treatment-materials and dosages,
as well as with the season in which the tests were conducted. In
some instances no benefit was obtained from treatments in one
season, whereas considerable increase in germination resulted
from the same treatments and on the same land at another
season. Likewise, certain treatments gave no improvement in
one locality and considerable improvement in another locality
during the same season.
Different isolates of Rhizoctonia used in greenhouse tests
showed differences in pathogenicity to the crop from which
they were isolated as well as to other crops. The tests also
revealed that the degree of pathogenicity to certain crops and

Florida Agricultural Experiment Station

the effect of materials on the seed and as protectants to the seed
are influenced in some cases by the soil temperature and reaction.
Since organisms other than Rhizoctonia are known to be in-
volved in seed decay in some localities and the factors influencing
their activity are unknown, it is possible that they may be active
where Rhizoctonia causes no trouble. It is concluded, therefore,
that seed treatments will not prove beneficial at all seasons of
the year in all localities, but because of the low cost, treating
the seed is a profitable investment.
For convenience, results of the experiments are considered by
crops, although seed of 2 or more crops were included in the
same experiment in many instances. In each case the most
effective dosages of the best treating materials will be indicated
for different soil types and soil reactions when this information
is known.

Because of the difficulty growers have experienced in obtain-
ing a stand of Fordhook lima beans and because some of the
seed treatment materials tried by them have caused decided
injury to seed and seedlings, numerous experiments were con-
ducted with this variety in an effort to ascertain some of the
factors which influence the treatments. A few tests were con-
ducted with the Henderson Bush variety, although there are
fewer complaints of poor stands with this variety than with
Fordhook. Since reports from other states indicate that many
materials are injurious to Fordhook lima bean seed, only the
ones that have proved less injurious were used in most of
these tests.
To test the direct effect of the treating materials upon the
germinating seed and seedlings, treated Fordhook seed were
planted in sterilized soil in the greenhouse, in which a series
of soil reactions from pH 5.5 to 8.5 was established by the
addition of sulfur or lime. Results of these tests are given
under each seed treatment material. From a cultural standpoint
it was found that in sterilized soil the seed germinated more
promptly and the plants grew more vigorously at reactions from
pH 6.5 to 8.5 than at lower reactions. Tests performed in the
field showed that not only was plant growth better but the yield
of beans was higher at soil reactions of pH 6.0 to 6.5 than at
pH 5.3 to 5.6. Thus, it appears that soils with reaction below
pH 6 are unsuited to Fordhook lima beans.

Dust Treatments for Vegetable Seed

Since Rhizoctonia is apparently responsible for most of the
seed decay in the fields, a parasitic strain of this organism was
used for inoculating soil used in some of the greenhouse tests.
Field tests were also conducted in soils naturally infested with
this Rhizoctonia. Reactions of these soils were pH 5.5 for the
Scranton soil and about pH 7.00 for the Norfolk sandy loam.
The natural reactions of these soils were changed in some plots
by the addition of sulfur or hydrated lime, and the effect of
the treating materials upon the seed, plant growth and yield
was studied.
Some baldheadd" plants appeared in all tests and there was
a significant difference due to treatment in a field test on Scran-
ton soil, where fewer baldheadedd" plants developed from seed
treated with arasan and spergon. The percentage of such plants
was never over 10 percent, except in 1 test in which the mean
percentage was 28 percent. In this test a heavy rain fell when
the seedlings were in the "crook" stage of germination and the
mean temperature was comparatively low for the following 3
days, which retarded emergence. In another test with seed
from the same stock planted 10 days later only 8 percent of
the plants were baldheadss." This indicated that the heavy
rain washed infested soil through the breaks in the seed coats
and the fungus, Rhizoctonia, killed the plumules before the
plants emerged. Furthermore, the primary or juvenile leaves
of many other plants were damaged in various degrees, as evinced
by holes and frayed margins, and the results indicated that
seed treatments provided no protection against this type of
Arasan.-This material was tested at the rates of 0.08, 0.125,
0.25, 0.30 and 0.42 percent. The 0.42 percent dosage caused
slight injury to the seed when the soil was cool. The 0.125
percent dosage was as effective in preventing seed decay in
most cases as the higher rates of application. In most field
tests the treated seed produced a significant increase in stand
of better plants than nontreated seed. The seed coats shed
promptly and the cotyledons remained clean. Arasan is recom-
mended at a dosage of 0.125 percent.
Cuprocide.-This material increased the stand of Fordhook
lima beans in certain years on the muck soils of the Everglades,
while in other years it gave no improvement. It greatly reduced
germination on the sandy soils in the central part of the state.
This indicates that the amount of organic matter in the soil

Florida Agricultural Experiment Station

influences the effect of cuprocide on the seed. In the sandy
soils with reaction below pH 6.0 injury was more severe than
when the reaction was higher. At soil reactions above pH 6.5
cuprocide caused no injury.
Cuprocide hardened the seed coats and prevented them from
splitting to permit emergence of the shoots. In some cases
injury to the stems was so severe that the plants never emerged.
In sandy soils with reactions above pH 6.5 cuprocide did not
improve germination. Therefore, this material is not recom-
mended for treating lima beans.
Spergon.-This material showed no signs of injury to the
seed at any rate of application (0.25 to 2 percent) or at any
soil reaction tested. In Scranton soil artificially inoculated with
Rhizoctonia the 0.42 percent rate of application was more effec-
tive in improving germination than the lower rates, whereas on
Norfolk soil a dosage of 0.25 percent was as effective as the
higher rates. The seed coats of treated seed split and shed
promptly and the cotyledons remained green and attached to the
stems longer than did those from seed treated with any other
material with the possible exception of arasan. Spergon is one
of the best and safest materials for treating Fordhook lima beans
and is recommended for use at dosages from 0.25 to 0.40 percent.
In one of the 3 tests with Henderson Bush lima beans spergon
produced a significant increase in germination, while other treat-
ing materials produced no significant increases. It appears,
therefore, that benefit will not be obtained consistently from
treatment of this variety.
Zinc Oxide.-This material was used in several tests at dif-
ferent dosages. It showed a tendency, especially in the higher
dosages, to harden the seed coat and reduce germination. In
infested soil, zinc oxide was less effective as a seed protectant
than arasan or spergon. Therefore, it is not recommended as
a seed protectant for Fordhook lima beans.
As a rule, little or no difficulty is experienced with seed decay
of snap beans in commercial fields when viable seed of standard
varieties are planted. However, poor germination has been re-
ported with certain varieties and from old seed of low viability.
A few tests were performed on Norfolk sandy loam soil to
determine whether seed treatments are beneficial under field
conditions. Giant Stringless Greenpod seed were treated with

Dust Treatments for Vegetable Seed

full dosages of spergon or zinc oxide and with 0.125 and 0.25
percent dosages of arasan and 0.25 percent cuprocide and
spergon. None of these materials or dosages gave any increases
or decreases in germination. However, when seed of the same
variety were treated with semesan, spergon, zinc oxide and
cuprocide at a 0.25 dosage and planted in potting soil artificially
infested with Rhizoctonia a decided improvement in germination
resulted from all treatments. Semesan gave a much higher
increase in germination than any of the other 3 materials, which
were about equally effective. When old Kidney Wax seed of
low viability were treated with a 0.25 percent dosage of spergon,
cuprocide or zinc oxide and planted in Scranton soil in late fall,
significant increases in germination were obtained from all treat-
ments. In this case spergon was better than the other 2.
One test was performed with a pole variety, U. S. No. 3, be-
cause of reports that poor germination was sometimes secured.
Spergon and arasan were used at dosages of 0.13, 0.21 and 0.42
percent and the seed were planted in the greenhouse in soil
artificially infested with Rhizoctonia. All treatments signifi-
cantly increased germination, but there were no differences
between materials or rates of application.
Results of these tests and observations of commercial plant-
ings show that little or no benefit may be derived from treat-
ing seed of high viability of Stringless Greenpod. However,
benefit may result from treating old seed or seed of certain
susceptible varieties. Spergon at a 0.25 percent dosage or
arasan at a 0.125 percent dosage is recommended. None of the
seed-treating materials caused a reduction in post-emergence
damping-off which is common in many areas of the state.

Garden beet seed have responded well to most seed treatments
which have been tested on them. An exception is spergon,
which reduced the emergence of beet seed treated at the rate
of 2.0 percent when planted in rather dry peat soil. Arasan when
used at rates of 0.25, 0.50 and 1.0 percent, ceresan at 1.0 per-
cent, and cuprocide at 1.5 percent increased the stand of beets
in peat soil by about 100 percent. In other states weak seed
lots have shown greater response to seed protectants than seeds
of high viability. The treatment with arasan at 0.50 percent
is recommended for beets. Ceresan may be used if desired.

Florida Agricultural Experiment Station

No seed-treatment tests were performed with broccoli in
connection with this work, but since seed of this crop have been
found to respond to seed treatments in other states in a manner
similar to cabbage, it appears that the same would hold true
in Florida. Consequently, arasan at a dosage of 0.25 percent
or semesan at a 0.35 percent dosage is recommended.

This crop has been found to respond to seed treatments in a
manner similar to cabbage and other members of the mustard
family, and arasan at 0.25 percent or semesan at 0.35 percent
is recommended where treatment appears advisable.

The varieties used in the experiments were Charleston Wake-
field, Copenhagen Market and Golden Acre. All of these vari-
eties responded to seed treatments in a similar manner, but
there were some differences in response among different seed
lots of the same variety. As a rule, seed of low viability showed
greater increase in germination from treatment than lots of
high viability. The tests were performed at all seasons of the
year in both greenhouse and field plots to take advantage of
the different soil temperatures. Tests were conducted in loamy
potting soil in the greenhouse and outdoors in Bladen sandy
loam with a reaction of pH 4.53 to 5.43, Norfolk sandy loam
with pH 5.50 to 6.94, Scranton fine sand, pH 5.5 to 7.0, and
Manatee sandy loam, pH 6.5. These soils were either naturally
or artificially infested with Rhizoctonia or naturally noninfested
or artificially sterilized. Several seed treatment materials were
tested at rates of application varying from 0.125 percent to full
dosage; that is, all the seed would retain. Conclusions from
results of the tests are as follows:
Arasan.-Arasan and thiosan 1 were tested in several dosages
on several soil types that had been given various treatments.
A 0.25 percent dosage of arasan was significantly better than
most other materials tested for protection against Rhizoctonia,
and the increases against Pythium were highly significant.

SThiosan is a fungicide containing the same active ingredient as arasan.
It was used in 1 or more tests with most of the varieties of seed and since
both forms acted in a similar manner, results are reported for arasan,
the seed-treatment form.

Dust Treatments for Vegetable Seed

Since there were no indications of injury to the seed or seedlings
under the experimental conditions, arasan appears to be a safe
and effective seed protectant for cabbage at a 0.25 percent
Cuprocide.-This material gave significant increase in ger-
mination under some conditions, but was usually less effective
than some other materials used. Furthermore, it caused injury
in varying degrees. The injury was most severe when the
material was used at full and 2 percent dosages on light soils
with low organic content and reaction below pH 6. When used
at 0.25 percent and the seed planted in heavier soils with re-
action above pH 6 cuprocide provided good protection against
seed decay and caused little or no injury to the germinating
seed. Because of these limitations cuprocide is not recommended
for general use as a seed protectant for cabbage.
New Improved Ceresan.-This material at dosages of 0.25,
0.50 and 1 percent gave significant increases in germination but
caused some stunting of plants at all dosages. The 0.25 percent
dosage gave most improvement and the least amount of stunting,
but since it was less effective than other materials it is not
Phenyl Mercury Compounds.-One test was run with 2%
phenyl mercury acetate and 4% phenyl mercury chloride at a
dosage of 0.5 percent in soil artificially infested with Rhizoc-
tonia. Both materials caused a highly significant increase in
germination and the 2% phenyl mercury acetate was signifi-
cantly better than the 4% phenyl mercury chloride. The latter
material retarded germination and caused severe stunting of
the seedlings, while the former caused less injury. Both ma-
terials are too toxic for use at a 0.5 percent dosage. These
are experimental materials and not yet on the market for
seed treatments.
Semesan.-At full dosages on Norfolk sand and at a 2 per-
cent dosage on Scranton and Manatee soils semesan reduced
germination or retarded growth of the seedlings. However,
good control of seed decay was obtained on all 4 soils with 0.25
and 0.50 percent dosages and there were no indications of in-
jury. Different soil types, temperatures and reactions showed
no influence on the behavior of this material. Thus, semesan is
one of the best protectants for cabbage when used at the proper

Florida Agricultural Experiment Station

Spergon.-Results obtained with spergon were somewhat vari-
able but it controlled seed decay in some degree at all dosages
tested without showing any signs of injury to the plants. A
0.50 percent dosage provided the most consistent protection
against Rhizoctonia, which in some cases was equal to that
provided by the best materials. In a limited number of tests
it was less effective than other materials against Pythium.
Effectiveness of spergon appeared to be influenced more by soil
temperature than by any other environmental factor. It was
more effective at soil temperatures above 750 F. than at lower
temperatures. At the higher temperatures the 0.50 percent
dosage was more effective than a 0.25 percent dosage and equal
to the higher rates of application. An impure grade provided
by the manufacturers for trial proved to be as effective as the
pure grade. Spergon appears to be a good seed protectant for
cabbage seed in a 0.50 percent dosage.
Zinc Oxide.-This material showed no injury to cabbage seed
at any rate of application from 0.25 percent to full dosage, ex-
cept in soils with reaction below pH 5.5, where 2 percent and
full dosages caused some injury. In most tests a 0.50 percent
dosage was as effective in preventing seed decay as higher
percentages of the same material. Soil type or soil temperature
showed no influence upon its behavior. Generally, however, it
was slightly less effective in protecting seed against Rhizoctonia
than certain other materials and significantly less effective
against Pythium.
Experimental work with carrot seed treatments on peat soils
in the Everglades has not demonstrated any significant increases
in germination with arasan, spergon, semesan, cuprocide or zinc
oxide. No tests have been performed on other soil types in the
state, but all of these materials have been reported to be bene-
ficial in several other states at dosages of 0.50 to 1 percent,
and arasan was slightly more effective than the others.
No experiments have been performed with cantaloupe in Flor-
ida but in other states it has responded to treatments in a
manner similar to cucumber. It appears that the same materials
and dosages as recommended for cucumber would be effective
for cantaloupe. Arasan at a 0.125 percent dosage and semesan
at 0.30 percent are recommended.

Dust Treatments for Vegetable Seed

In the states where tests have been performed cauliflower has
responded to seed treatments in about the same manner as
cabbage and other cruciferous plants. Hence, arasan at a dosage
of 0.25 percent or 0.35 percent semesan is recommended.

Pre-emergence damping-off has not been of much importance
in the peat soils of the Everglades, but post-emergence damping-
off is usually a serious factor.
Seed treatments which have been tried with celery for the
control of post-emergence damping-off caused by Rhizoctonia
have not shown significant increases in the number of seed
sprouting. No tests have been performed on other soil types
and seed treatments usually have been non-effective in other
states. The mercurial treatments seem to be slightly detri-
mental. Cuprocide or spergon might be used if desired.

Several varieties of cucumber were used in the tests but the
variety Abbott and Cobb was used most extensively. The tests
were performed in flats in greenhouses, in field beds and in com-
mercial fields. Reaction of the Scranton soil was pH 5.8 and
that of the Norfolk was pH 7.15, while that of the soils used
in the greenhouse tests ranged between these extremes. For
some greenhouse tests a series of soil reactions ranging from
pH 5.5 to 7 was established by adding hydrated lime or sulfur
to the soil. The soils were naturally infested with seed-decaying
organisms or artificially infested.
Cuprocide, semesan, spergon and zinc oxide were used at
dosages of 0.20, 0.25, 0.30, 0.50, and 1 percent; arasan at 0.125,
0.20 and 0.25 percent; new improved ceresan at 0.30 percent
and yellow cuprocide at 1 percent. All of these materials gave
increases in germination but arasan and semesan were con-
sistently better than the others. Increases were not always
significant with these in the Norfolk soil, indicating that field
conditions were not always favorable for seed decay. There
were no significant differences between dosages and none of
them caused any apparent signs of injury to the seeds and
seedlings. Hence, it appears that cucumber seed are very toler-
ant to treatment materials and that the treatments are generally

Florida Agricultural Experiment Station

beneficial. Arasan at a 0.125 percent dosage and semesan at
0.30 percent are recommended.
Eggplant is grown in the fall, winter and spring seasons in the
southern part of the state and as a spring or fall crop in other
areas. Usually little or no difficulty is experienced with germina-
tion of seed, but the seedlings are often affected with daming-off
after they emerge. Two seed-treatment tests were performed
on Norfolk sandy loam soil-1 in the fall and the the
spring-to ascertain whether any treatments might prove bene-
ficial. For the fall test full dosages of cuprocide, semesan and
zinc oxide were used. Zinc oxide gave a highly significant in-
crease in germination, whereas semesan and cuprocide gave
no significant increases. There were no signs of toxicity to
the seed.
In the spring test cuprocide, semesan, spergon and zinc oxide
were used at 0.50, 1 and 2 percent dosages. Zinc oxide again
produced a higher percentage increase in germination than any
of the other materials included in the test. None of the other
3 materials gave significant increases in germination at any
dosage, but there were no signs of toxicity to the seed. There
were no significant differences in germination between dosages
of zinc oxide. Hence, it appears that a 0.5 or 1 percent dosage
would be as effective as higher ones.

Two field tests were performed with escarole seed and results
were practically the same as with lettuce under similar condi-
tions. Therefore, the same treatments are recommended for
this crop as for lettuce.
Because of the variable results obtained in the experimental
locations several tests were run with lettuce seed in an effort
to learn some of the factors that influence the treatments. The
variety Imperial 44 was used in practically all cases. The tests
were made at different temperatures in the greenhouse and in
field beds on 3 different soil types in different seasons. Reactions
of the potting soils used in the greenhouse ranged from pH 5.7
to 6.7. In the field beds the reaction of the Leon soil was pH
5.27, the Bladen sandy loam pH 4.53 and 5.77, Scranton fine

Dust Treatments for Vegetable Seed

sand pH 5.8, and the Norfolk sandy loam pH 6.00 to 7.2. The
field tests were performed in the seasons when the growers
normally plant lettuce in the respective localities to ascertain
whether soil type, temperatures and reactions have any influence
on effectiveness of the treating material or on their harmful
effects to the seed.
Strains of Rhizoctonia and Pythium are the fungi that have
been found attacking lettuce seedlings thus far in commercial
plant beds. These organisms were used to infest soil for tests
in the greenhouse. Tests were performed also in field plots in
some of which the soil was known to be infested with 1 or both
of these organisms. Failure to obtain beneficial results in some
of the field tests appeared to be due to environments unfavor-
able for the development of seed decay or to absence of seed-
decaying organisms. The comparative effectiveness of seed pro-
tectants in preventing seed decay by them is discussed below.
Arasan.-This material was used at dosages of 0.125, 0.20,
0.25, 0.30 and 0.40 percent. In all of the tests the 0.20, 0.25 and
0.30 percent dosages gave larger increases in germination than
the lower or higher concentrations. In soil artificially infested
with Rhizoctonia in the greenhouse arasan at dosages of 0.20
and 0.25 gave as high increases in germination as any other
treatment. Furthermore, in soil artificially infested with
Pythium, arasan was significantly better than any others. When
the daily mean temperature was 700 F. or above, heavier dosages
than 0.25 percent retarded germination, resulting in irregular
emergence. In the field tests arasan did not always produce
significant increases but at a 0.25 percent dosage it was as
effective as any other material used. Because of its high
specific toxicity against Pythium, arasan at a dosage of 0.25
percent appears to be a safe and effective treatment for lettuce
when the seed are planted at the usual time in the state.
Cuprocide.-This material was used at dosages of 0.25, 0.50,
1 and 2 percent. Results obtained with it were variable, and all
the causes of the variation were not determined. In some green-
house tests, at 1 and 2 percent dosages, it gave good protection
against Rhizoctonia but poor protection against Pythium. In
a few of the field tests a 0.5 percent dosage was as effective as
higher rates of application. No signs of injury resulted from
any dosage. Since other materials proved to be more consistently
effective, cuprocide is not recommended for lettuce, especially
in soil infested with Pythium.

Florida Agricultural Experiment Station

Semesan.-This material was tested under various conditions
at dosages of 0.20, 0.25, 0.50, 1 and 2 percent. In most of the
field tests the 0.50 percent dosage gave significant increases in
germination; the 1 and 2 percent dosages not only failed to in-
crease germination but injured the seedlings. A 0.50 percent
dosage gave a significant increase in germination in soil arti-
ficially infested with Pythium, but it was much less effective
than arasan or spergon. From results of these tests it appears
that semesan has a limited use as a treatment for lettuce seed
in Florida and is not recommended for general use.
Spergon.-This material was tested at dosages of 0.25, 0.50,
1 and 2 percent, in both field and greenhouse. It gave no sig-
nificant increases in germination in any of the field tests, but in
some tests it gave about as much benefit as any other material.
There were no signs of injury to the seed or seedlings at any
dosage. In the greenhouse dosages of 0.50 and 1 percent ranked
next to arasan in protecting seed against Rhizoctonia and the
difference between dosages was not significant. Because of
these results a 0.50 percent dosage of spergon appears to be a
satisfactory treatment in most soils where lettuce is planted.
Zinc Oxide.-Zinc oxide was tested at dosages of 0.50, 1 and
2 percent in the greenhouse and outside beds artificially or
naturally infested with Rhizoctonia. In some cases it gave
significant increases in germination at dosages of 1 and 2 per-
cent that were about equal to those produced by arasan, but it
was much less effective against Pythium. There were no indi-
cations of injury to the seed or seedlings under any conditions,
and the results indicate that it will improve germination at
dosages of 1 or 2 percent in soils that are not heavily infested
with Pythium.
Mustard is another cruciferous crop that has been found to
respond to seed treatments in other states in about the same
manner as cabbage; hence the same treatments may be used.
These are arasan at a dosage of 0.25 percent or semesan at 0.35
This crop, which is grown extensively only on the peat soils
in the Everglades, is frequently subject to severe losses due to
seed decay and post-emergence damping-off. The Rhizoctonia

Dust Treatments for Vegetable Seed

fungus is believed to be the principal factor causing these losses.
It is most active when showers and warm weather occur during
the period when the seeds are sprouting. Several fungicidal
dusts give good results in the control of such losses.
Arasan.-This material has been tested at dosages of 0.06,
0.13, 0.25 and 0.50 percent. It was very beneficial at all of these
dosages. Seedling stands were increased by about 25 percent.
The 0.25 percent dosage is recommended.
Cuprocide.-Cuprocide when tested at dosages of 0.06, 0.13,
0.25 and 0.50 percent over a period of years has always given
the best results at the rate of 0.50 percent.
Semesan.-This material has given very good results at
dosages of 0.13, 0.25 and 0.50 percent. The 0.25 percent dosage
should be adequate for the protection of the seed in most in-
Spergon.-Spergon has given best results of all treatments
tried on peas. When tested at rates of 0.06, 0.13, 0.25 and 0.50
percent it gave the highest stand counts with the 0.25 and 0.50
percent rates. The 0.25 percent dosage is recommended.
Vasco-4.-This material was tried in 1 experiment at dosages
of 0.13 and 0.50 percent. It did not give good results at either

In the principal pepper-growing areas of the state seedbeds
are maintained during 2 periods, 1 extending from July through
September for fall setting and the other from November through
January for the spring crop. Seed decay is usually of little
importance in the early seedbeds, but post-emergence damping-
off may be a serious problem. In late seedbeds neither seed
decay nor post-emergence damping-off is very important except
when mild wet weather prevails. This indicates that soils in
pepper-growing areas are not commonly infested with organisms
which cause serious decay of pepper seed.
To take into account the factors which might be associated
with the different planting dates, all experiments with pepper
seed were performed in field beds on Scranton and Manatee
soils, using the varieties Florida Giant and World Beater. In
some of the experiments a series of reactions varying from pH
4.5 to pH 7.0 was established by adding hydrated lime or sulfur
to the soil. Manure was added to some plots in other experi-

Florida Agricultural Experiment Station

ments. Only 3 seed-treating materials, cuprocide, semesan and
zinc oxide, were used in most of the experiments; copper carbo-
nate and spergon were included in 3 tests. All of these materials
were used at dosages of 0.25, 0.50, 1 and 2 percent. One of the
tests was performed simultaneously on the 2 soils and the others
were performed only on Scranton soil that had been given vari-
ous treatments.
Results of the experiments varied with the time of year the
seed were planted and with the presence or absence of seed-
decaying organisms in the soils. The Manatee soil was found
to be only slightly infested with seed-decaying organisms para-
sitic to pepper or environmental conditions were otherwise un-
favorable for seed decay. Because of this no outstanding or
consistent results were obtained with any of the treating ma-
Copper Carbonate.-In the 3 experiments where copper carbo-
nate was used it caused no increase or decrease in germination.
There were no signs of injury to the seed or seedlings.
Cuprocide.-This material gave no significant increases in
germination under any conditions. On Scranton soil with low
organic content and reaction below pH 6.0 it reduced the stand.
This injury was most pronounced with dosages above 0.25 per-
cent. Cuprocide, therefore, appears to be unsuited for treating
pepper seed on the sandy soils with low pH.
Semesan.-This material caused a significant increase in
germination in only 1 test, and was more effective in manured
soil with a reaction above pH 5.6 than in nonmanured soil with
a lower pH value. Response to all dosages was similar and there
were no signs of injury. Semesan appears to be a safe treat-
ment for pepper seed and apparently will prove beneficial in
soils infested with seed-decaying organisms. A dosage of 0.25
to 0.50 percent is recommended.
Spergon.-This material did not cause significant increases in
germination at any dosage and the higher dosages showed a
tendency to reduce germination during the summer. In the fall
planting a 0.25 percent dosage gave as good germination as any
material tested. It would apparently be safe and beneficial to
use under these conditions.
Zinc Oxide.-This material gave better results in most cases
than any of the other materials tested and did not show as much
tendency to injure the seedlings on sandy acid soils as did the

Dust Treatments for Vegetable Seed

others. Germination with dosages of 0.25 and 0.50 percent was
slightly better than with the higher ones. Hence, it is recom-
mended that zinc oxide be used at dosages of 0.25 to 0.50 percent.

Spinach is commonly grown in Florida home gardens during
the fall and spring months, but until the last few years com-
mercial plantings have been limited to a comparatively small
acreage. Reports have indicated that poor stands are of fre-
qent occurrence and that post-emergence damping-off is very
serious in some localities. Because of these reports, numerous
tests were performed in different seasons with several materials
and dosages to learn whether any improvement in stand might be
obtained by treating the seed. Varieties used in the experi-
ments were Bloomsdale Long Standing Savoy and Virginia Savoy.
The tests were performed in the greenhouse at Gainesville
in artificially infested soils and in field beds at various localities
on Norfolk sandy loam with reactions of pH 6.5 to 7.2, Leon
with a reaction of pH 5.27, Bladen sandy loam with reactions
of pH 4.53 and 5.67, Manatee fine sandy loam with pH 6.5 and
Scranton fine sand with pH 5.8. The last had been manured
3 months before and artificially infested with a strain of Rhizoc-
tonia parasitic to spinach. The field tests were performed in
late fall and early spring when the daily mean temperature was
comparatively low, while the greenhouse tests were performed
mostly during the winter months when advantage could be taken
of artificial heat to vary the soil temperatures. In these tests
Rhizoctonia caused a higher percentage of seed decay at a mean
soil temperature of 800 F. than at 660. Results of the tests
are as follows:
Arasan.-A 0.25 percent dosage of arasan produced highly
significant increases in germination at 800 and at 66 F., but
the percentage increase was higher at the higher temperature.
In greenhouse soils artificially infested with Pythium irregu-
lare Buis. germination of seed treated with 0.40 arasan was
practically twice that from nontreated seed and slightly better
than that of seed treated with a 0.20 percent dosage and all
other treatments.
In outdoor beds on Norfolk, Manatee and Scranton soils 0.25,
0.50, 0.75 and 1 percent-dosages gave about the same increases
in germination of Virginia Savoy seed and were equal to in-
creases due to any of the other materials used. Increases in

Florida Agricultural Experiment Station

germination of Bloomsdale Savoy seed planted at the same time
and under similar conditions were not as large as with the Vir-
ginia Savoy but germination of the seed treated with arasan
was as good as that with any other treatment. On the Bladen
sandy loam infested with P. irregulare and Rhizoctonia, dosages
of 0.125 and 0.25 percent gave significant increases in germina-
tion which were about the same, and equal to that resulting from
any other treatment. There were no signs of injury from any
of the dosages under any conditions. Arasan, therefore, appears
to be a safe and effective seed treatment for spinach. It is
recommended for use at a dosage of 0.25 to 0.50 percent.
Ceresan.-A full dosage of this material gave a larger increase
in germination than similar dosages of any other material tested
on the Leon sandy loam and Norfolk sandy loam. In these tests
there were signs of stunting and the beds were not maintained
long enough to ascertain whether the plants would overcome
the injury.
Dosages of 0.25, 0.50 and 1 percent produced no increases in
germination on the Norfolk soil at the different levels of soil
reaction and organic content. On Bladen sandy loam 0.50 and
1 percent dosages gave no increase in germination. Results of
these tests indicate that ceresan is not a satisfactory material
for treating spinach seed.
Cuprocide.-On the Norfolk sandy loam and Leon soils a full
dosage of cuprocide gave highly significant increases in germina-
tion. In another test on Norfolk soil dosages of 0.25, 0.5 and
1 percent gave significant increases in germination regardless
of soil reaction, whereas on the same soil type to which manure
had been added they caused decreases in germination at each
reaction. On the Scranton soil 2 percent cuprocide gave a highly
significant increase in germination. On Bladen sandy loam in-
fested with Pythium and Rhizoctonia 0.5 and 1 percent dosages
of cuprocide gave practically the same increases in germination
and were slightly better than any other material in the test.
However, it was less effective than arasan or spergon in soil
artificially inoculated with P. irregulare. Results of these tests
indicate that spinach seed are not very sensitive to injury by
cuprocide and that this material is a good protectant under most
conditions. It may be used at dosages ,of 0.5 to 1 percent.
Semesan.-In early spring full dosages of semesan gave highly
significant increases in germination on the Leon sandy loam

Dust Treatments for Vegetable Seed

and on Norfolk sandy loam and there were no conspicuous signs
of injury. In the fall when the temperature was higher, dosages
of 0.5, 1 and 2 percent caused decreases in germination on the
Norfolk soil at different soil reactions and organic content. Seed
treated with 0.25, 0.50 and 1 percent dosages and planted in late
fall on Bladen sandy loam gave significant increases in germina-
tion and there were no significant differences between dosages.
Although semesan has given beneficial results in some instances,
its behavior seems to be erratic and less satisfactory than that
of certain other materials.
Spergon.-This material was tested at dosages of 0.25, 0.50,
0.75, 1 and 2 percent in the greenhouse and in outdoor beds. In
soil artificially inoculated with Rhizoctonia dosages of 0.50 and
1 percent gave equal and highly significant increases in germina-
tion. A 0.50 percent dosage also gave a highly significant increase
in germination in soil artificially infested with Pythium, but
the increase was significantly lower than that due to treatment
with arasan.
In field plots on the Bladen sandy loam dosages of 0.50 and
1 percent gave equal and significant increases in germination.
On the same soil the following year 0.25 and 0.50 percent
dosages gave highly significant increases that were about equal.
In both tests spergon gave about as good results as any other
material tested. On the Norfolk sandy loam no dosage gave
a significant increase in germination of Bloomsdale Savoy seed.
This lot of seed was highly viable, which is probably why no
benefit was obtained from seed treatment. On the Scranton
soil a 1 percent dosage of spergon gave a highly significant in-
crease in germination. On a basis of these tests it appears that
dosages of 0.50 to 0.75 percent are safe and effective for spinach
in most cases.
Phenyl Mercury Compounds.-Two mercury compounds, 2%
phenyl mercury acetate and 4% phenyl mercury chloride were
included in 1 test at dosages of 0.50 percent. In soil artificially
infested with Rhizoctonia in the greenhouse these materials
gave about equal increases in germination which were highly
significant. On a basis of this 1 test these materials appear
to be effective for spinach seed.
-Zinc Oxide.-A full dosage of zinc oxide gave as good control
of seed decay on the Leon sandy loam as similar dosages of any
other material used in the test. On the other hand, it was less

Florida Agricultural Experiment Station

effective than the other materials on the Norfolk sandy loam,
although it gave a significant increase over the check.. In beds
where the reaction was reduced to pH 6.18 by the application
of sulfur, increase in germination was as good as that from any
other treatment, and all increases were significant. In late fall,
dosages of 0.5, 1 and 2 percent gave no increases in germination
on Norfolk soil, regardless of the reaction or organic content.
The following spring 2 percent zinc oxide gave significant in-
creases with both varieties on Norfolk and Scranton soils. In
late fall on the Bladen sandy loam neither 0.5 percent nor 1
percent dosages gave a significant increase in germination,
whereas similar dosages of other materials did.
In soil artificially inoculated with P. irregulare in the green-
house with a mean daily temperature of 73 F., 2 percent zinc
oxide gave a highly significant increase in germination but the
increase was lower than that due to treatment with arasan.
These results indicate that zinc oxide reduces decay of spinach
seed under some conditions, although it was not always as
effective as certain other materials. No signs of injury were
ever observed with any dosage. It appears that either a 1 or 2
percent dosage is a good treatment for spinach seed under most

Sweet corn seed of high viability usually germinate promptly
without much damage from seed decay. However, when the
seed are planted in cool wet soil germination is retarded and
poor stands are not uncommon, especially with weak seed.
Two seed treatment tests were made with sweet corn planted
in Scranton soil during early spring of 1944. In 1 test seed of
the variety Ioana were treated with semesan Jr., arasan, spergon
and barbak C, each at 0.19 and 0.38 percent dosages. In the
other test seed of Golden Cross Bantam and Long Island Beauty
were treated with arasan at 0.13 percent, spergon and a special
impure grade of spergon at 0.30 percent dosages.
There was no increase in germination due to seed treatments
with Golden Cross Bantam. The seed showed high viability,
germinated quickly and the plants grew rapidly. Seed of loana
and Long Island Beauty were of lower viability and germinated
slowly. Some of the seed treatments improved germination,
arasan being better than any other material. The low rate of
application gave as good results as the higher rate. Both grades

Dust Treatments for Vegetable Seed

of spergon improved germination to an equal degree. Semesan
Jr. at the higher rate increased germination but did not give any
increase at the lower rate. Barbak C gave no increase in germi-
nation at either dosage and produced a slight stunting effect
upon plant growth. Arasan at a 0.13 percent dosage is recom-
Reports of growers indicate that tomato seed, like seed of
eggplant, usually germinate satisfactorily, but the seedlings
may be killed by damping-off soon after they emerge. Because
of this situation only a few seed-treatment experiments were
performed with tomato seed.
Seed of the Marglobe variety were treated with 0.50, 0.75,
1 and 2 percent and full dosages of cuprocide, semesan, spergon
and zinc oxide and planted in the spring on Norfolk sandy loam
soil with normal reaction of about pH 7.00 and pH 6.08 established
by the addition of sulfur. All 4 of the materials and dosages,
except 2 percent and full dosage, produced significant increases
in germination on the soil with normal reaction, but only spergon
and zinc oxide gave significant increases on the soil to which
sulfur was added. There was no indication that the sulfur caused
direct injury to the seed. None of these 4 materials produced
significant increases in germination of seed planted on the same
land in the fall. All 4 materials produced significant increases
in germination of seed planted in the winter on Leon soil with
a pH value of 5.27. Full dosages of all 4 materials reduced
germination on the Scranton soil.
In 1 test in the greenhouse arasan, semesan, spergon, ethyl
mercury-p-toluene sulfonanilide, 2% phenyl mercury acetate,
4% phenyl mercury acetate, and 4% phenyl mercury chloride
were all used in a dosage of 0.25 percent. None of these ma-
terials produced any significant increases in germination. Re-
sults of these tests indicate that seed treatments do not
always produce increases in germination of tomato seed, even
at high rates of application. The seed appear to be tolerant
of seed-treating materials on soils with high pH reaction during
cool -weather but may be injured during warmer periods. Zinc
oxide and spergon may be used at a 0.50 percent dosage if desired.
No treatment tests were performed with turnip in connection
with this work, but in other states the seed have responded to

Florida Agricultural Experiment Station

treatments in about the same manner as cabbage. Arasan and
semesan are recommended at dosages of 0.25 and 0.35 percent,
Growers have been treating watermelon seed with cuprocide
or semesan for several years and report beneficial results in cool,
wet soil. No experimental tests have been performed in con-
nection with work reported in this bulletin but increases in
germination from the use of these materials have been reported
in other states. Therefore, cuprocide and semesan are recom-
mended at dosages of 0.5 and 0.35 percent, respectively.


Some seed may be treated already when purchased, or if
desired one may have the dealer treat them. Treating seed is
not a difficult or expensive task. Seed to be treated should be
clean and dry and kept dry until planted. Use all treatment
chemicals in the form of dusts. Weigh or measure them ac-
curately, because more than the recommended amount usually
does no good and may cause injury.
Equipment for applying the dust is determined by the quantity
of seed to be treated. Small lots may be treated in the package
in which they came, in a tin can or glass fruit jar that has a
tightly fitting cover. The amount of material that will lie on
the flat end of a toothpick is usually sufficient to treat a 10-cent
package of small seed. This can be put into the packet with
the seed. Fold the open end of the bag and shake well to dis-
tribute it over the seed. For larger amounts of small seed or
for bigger seed fill the container about half full of seed, add the
recommended amount of chemical, put on the lid and roll or
shake it for 3 or 4 minutes, turning it about in a manner that
will assure an even distribution of the dust over the seed. When
facilities for weighing small amounts of dust are not available
the dust may be measured with a teaspoon, using a level tea-
spoonful of the loosened or fluffed-up material as the basis of
measurement in all cases. Use a straight-edged object or in-
strument to level off the chemical in the spoon.
The rotary barrel treater appears to be the most practicable
machine for treating large quantities of seed. A 55-gallon steel
drum is preferable but if one cannot be obtained a wooden barrel
may be used. When this is properly equipped and mounted it

Dust Treatments for Vegetable Seed

rolls and throws the seed against a mixing board and in addition
surges them from one end of the drum to the other. These 2
motions cause the dry dust to be evenly and completely spread


Crop Chemicals* Ounces for Level Teaspoonfuls
100 Ibs. Seed for 1 lb. Seed**
Bean (lima) spergon 4 %
arasan 2 1/
Bean (snap) spergon 4 Y
arasan 2 1/_
Beet arasan 8 1
ceresan 8 ___
Broccoli arasan 4 1/
semesan 6 Y
Brussels sprouts arasan 4 1/2
semesan 6
Cabbage arasan 4
semesan 6
Carrots arasan 8 1
spergon 12 1%V
Cantaloupe arasan 2 14
semesan 6 1
Cauliflower arasan 4
semesan 6 1
Celery cuprocide 8
spergon 12 1
Cucumber arasan 3
semesan 5
Eggplant zinc oxide I 8 %
semesan 6 1/2
Escarole arasan 4
spergon 8 1
Lettuce arasan 4 Y
spergon 8 1
Mustard arasan 4
semesan 6 '
Pea (English) spergon 4 %
arasan 4 '
Pepper zinc oxide 1 8 Y
semesan 6 /2
Spinach arasan 4
S cuprocide 8
Sweet corn arasan 2 14
spergon 6 6 4
Tomato zinc oxide I 8
spergon 8 1
Turnip arasan | 4 V
semesan I 6
Watermelon cuprocide 8
semesan 5 I
*Chemicals for each crop are listed in order of preference.
**The fractions of a teaspoonful are the nearest to the percentage recommended that
can be conveniently measured.

Florida Agricultural Experiment Station

over the seed. When properly constructed it is dust-tight, which
is an added advantage. Fill the barrel about half full of seed,
add the correct amount of dust, close the door and turn the
barrel slowly for about 5 minutes. Slow turning is necessary
to assure tumbling the seed from one end of the drum to the
other and to avoid mechanical injury to the seed.

Experimental work has been performed with seed of several
important vegetable crops in which many of the common ma-
terials recommended for seed-treating purposes have been com-
pared at various dosages. Many of the tests were performed
in 2 or more localities of the state on different soil types and
in seasons of the year when the seed are normally planted.
Other tests were performed in greenhouses where the effective-
ness of materials was tested against various isolates of Rhizoc-
tonia and Pythium under different soil temperatures and re-
In these tests no treatment material or dosage always proved
beneficial with all varieties and all seed lots under all conditions.
The variations appeared to be due to several factors. Seed lots
of low viability were benefited more by seed-treatment than seed
of high viability. As a rule, seed treatments gave largest in-
creases in germination when the mean soil temperature was
comparatively low and soil moisture was high. The amount of
undecomposed organic matter was found to influence activity
of Rhizoctonia and effectiveness of the treating material in some
cases. When large amounts of organic matter were turned under
shortly before the seed were planted a higher percentage of
seed decay and post-emergence damping-off resulted and in some
cases the seed-treatment materials were less effective. On the
other hand, some of the treatment materials, especially cupro-
cide, were less effective in preventing seed decay and more in-
jurious to the seed on sandy soils with low organic content and
a pH value below 6.0.
In certain field tests very little seed decay developed and seed
treatments were not beneficial, but damping-off became a serious
problem soon after the plants emerged. This was especially
noticeable in cabbage, celery and pepper seedbeds planted in late
summer when the mean soil temperatures were relatively high.
In other tests with cabbage and certain other crops a high per-
centage of seed decay occurred and this was followed by damping-

Dust Treatments for Vegetable Seed

off within a week or 2 after the seedlings emerged. Results of
tests performed in greenhouses indicate that both phases of the
disease may be caused by the same fungus. On the other hand,
results of field tests indicate that different fungi or different
strains of the same species may be involved in both seed decay
and damping-off. Rhizoctonia and Pythium were the 2 fungi
found to be most commonly associated with seed decay and
damping-off in the field. The numerous isolates of Rhizoctonia
showed varying degrees of pathogenicity to the crops from which
they were obtained as well as to other varieties. Such variations
in pathogenicity were evident even among isolates obtained from
the same small plant bed. It appears probable, therefore, that
there are different strains of Rhizoctonia and other fungi occur-
ring in various soil types and that other environmental condi-
tions also influence their pathogenicity.
Results of the tests clearly demonstrated that seed treatments
provide little protection against post-emergence damping-off,
even though they are very satisfactory in preventing seed decay.
Seed treatments, therefore, offer a practical solution for increas-
ing the stand of crops that are affected by seed decay but cannot
be relied upon for preventing damping-off after the plants
emerge. Crops that are susceptible to both seed decay and post-
emergence damping-off sometimes escape damping-off because
weather conditions are unfavorable for the disease. In some
cases, however, it will be necessary to supplement seed treat-
ments with spraying or drenching after the plants emerge to
provide adequate protection, or to treat the soil to eradicate
the organisms before planting the seed. Consequently, the seed
treatments recommended in this bulletin are for control of seed
decay only. Control measures for the damping-off phase of the
disease have been worked out for celery 2 but not for other crops.

Several of the dust fungicides recommended in this bulletin
are poisonous and the others are more or less irritating to the
eyes and nose. Treating equipment should be so arranged that
there will be as little free dust as possible. Treat the seed out-
doors or in a well ventilated building to avoid inhaling the dust.
It is advisable to use a mask or respirator when treating seed in a

2 Fla. Agr. Exp. Sta. Bul. 397.

32 Florida Agricultural Experiment Station

Benefits may be expected in most localities from treating the
seed with any of the chemicals recommended; however, do not.
treat the same lot of seed with more than 1 of them. The seed
can be safely treated at any time within 30 days before planting,
probably longer, provided they are kept dry. Treated seed should
be distinctly labeled, indicating the material and dosage used
and date of treatment.
Use treated seed for planting only, and keep them where they
will not be eaten by human beings or domestic animals.

The authors gratefully acknowledge the aid of the companies that con-
tributed the seed-treatment materials used in these experiments. The
companies participating in this manner were: Du Pont Semesan Co.,
Inc.; F. W. Berk & Co., Inc.; Naugatuck Chemical Division of the United
States Rubber Company; and Rohm and Haas Co., Inc.