HI

 

145
113
THS

SOEL TREATMENTS FOR. THE
CONTROL OF POTATO SCAB

‘

Thesis {or the Degree of M. 5.
MICHIGAN STATE COLLEGE
Clem KenKnight
1937

 

RETURNING MATERIALS:
Place in Book drop to

LJBRABJES remove this checkout from
your record. FINES wil]
be charged if book is
returned after the date
stamped below.

’7r'7‘r1a‘27.

 

SOIL TREATMEETS FOR THE CONTROL OF POTATO SCAB

Thesis Presented for the Degree of
Master of Science

Michigan State College

by

Glenn EgnKnight

1937

Acxmovrmbommr

The writer is indebted to Dr. J. H. Muncie for
advice and aid in carrying out this study, and to
Drs. J. H. Muncie and E..A. Bessey for criticism and

correction of the manuscript.

£10312

TABLE OF CONTEXT

Review of the literature on the control of potato scab
Resistant varieties
Clean seed and crop rotation
Green manuring and antibiosis
Bacterionhagy
Fertilizers
Sulphur soil treatments
Soil disinfection with chemicals
Mercuric chloride
ther mercurials
Other chemicals
Soil conditions influencing scabbing
The problem
Greenhouse studies
Procedure
Erperiment'I
Experiment II
Experiment III
Experiment IV
Field studies
Relation of soil reaction to the effect of mercurial
soil treatments on scabbing of potatoes

Summary

SOIL TREATHENTS FOR THE CONTROL OF POTATO SCAB

Altho the Actinomyces scab of potatoes is probably the oldest
known disease of that crOp, no very effective methods which have more
than local application have been devised for its control. Numerous
control measures have been recommended, any one of which may be effective
under certain conditions. These include the use of resistant varieties,
clean or disinfected seed, crOp rotation, green manuring, physiologically
acid fertilizers, sulphur soil treatments, and soil disinfection by
chemical means. In addition bacteriophagy has been suggested as a

possible means of inhibiting the develOpment of potato scab.

Review of the Literature on the Control of Potato Sca

 

Resistant varieties

 

The solution of the potato scab problem may eventually be solved
through the develOpment of resistant varieties. Russet Burbank and Russet
Rural, which are at present our most resistant varieties, are sometimes
heavily scabbed. Breeding for scab resistance has been under way in this
country for several years (17, 25, 26). It is to be expected that progress
will be slow due to the diffi ulties involved in breeding potatoes (such
as bud abscission, pollen sterility and polyploidy), and because of the
high standards of yield and quality set by the present commercial varieties,
and the fact that potatoes are attacked by a large number of strains of
Actinomyces which differ widely in their physiological characteristics
as pointed out below.

Clean seed and crOp rotation

 

The importance of clean seed and crOp rotation has been recognized
for over a century (69), but even clean seed on virgin soil has produced
I, . . .
scabby crops (71, 10%). In 80118 that are relatively free from plant

pathoaenic Actinomyces, seed-tuber disinfection will control potato scab;

-2-

but, where the scab organisms grow saprOphytically in the soil, seed
treatment is of little or no value (11H, 115, 151). In fact, mercurial

seed treatments in some localities increase the severity of the disease

J

(-8. 35. 13M. 136).

fi

F3

here is generally less scab where potatoes are not raised oftener
than every four or five years on a given field. The pathogenic actino-
mycetes may maintain their existence as saprOphytes in the soil, or, if
given an Opportunity they may attack other crOps. Beets (2, 10, M9, 97),
turnips, rutabagas and radishes (MM, M9, 101) have frequently been
reported as being susceptible to potato scab. Carrots (58, 76), sweet
potatoes (1, 73, 103, 132), and leeks (101) are also said to be parasi-
tized by species of Actinomyces. The sequence of non-susceptible creps
in the rotation may influence the amount of scabbing of potatoes (5, M2).
In selecting crOps for rotation with potatoes, the effect of the
rotation upon the yield and quality of all the creps in the rotation
should be considered. Potatoes are relatively tolerant of soil reaction,
the Optimum reaction apparently varying according to the locality. Most
investigators find that scab causes little damage where the soil reaction
is pH 5.3 or lower. Along the Atlantic seaboard potatoes are most pro-
ductive on soils with a reaction of pH 5.0 to 5.5 (31, 53, 85, 1‘47).
This gives a narrow margin of safety in which a good yield of scab-free
potatoes can be produced. On Long Island Hardenburg (51) observed that
scab was not an important factor until the soil pH reached 5.8 or higher,
thus giving a wider margin of safety there. With reference to this
region, Hardenburg (52) concluded that "so long as soil organic matter
can be maintained through the use of green manure creps, it is not

always necessary or even desirable to grow crops in an established rotation"

-3-

He suggested two independent rotations, one including potatoes along with
acid-tolerant crOps such as beans, cereals, cannery crOps except beets,
soybeans, and alsike clover, and the other including crOps favored by
soils with a higher reaction such as alfalfa, sweet clover, red clover,
cabbage, and beets. The soil acidity could then be adjusted to suit each
rotation.

Berkner (5) in Germany found that potatoes were most productive
on soils with a reaction of about pH 6.0 and that scab was less trouble-
some than on more alkaline soils. With a view to maintaining a reaction
of about but not exceeding pH 6.0 on light, dry soils he suggested a
rotation of rye, oats, potatoes, lupines, and serradella.

In regions where the soils are highly buffered it is not easy nor
always desirable to acidify the soil for potatoes. The yield of potatoes
is not always favored by lowering the soil reaction. Bushnell (15) in
Ohio found little difference in the yield of potatoes due to soil
reaction from pH 5.3 to 8.0. Furthermore, in Nebraska Goss (M2) found
more scab on soils of pH 5.9 than on more alkaline soils. Acidification
of the soil is detrimental to alfalfa which crOp may be desirable in a
rotation with potatoes. Under dry weather conditions in Michigan, Bird (7)
reported that higher yields are generally obtained where potatoes follow
alfalfa than where potatoes follow any other crOp. Under irrigation
conditions in Nebraska Goss (M3) found that short rotations and rotations
where beets immediately precede potatoes were undesirable, and that longer
rotations including alfalfa were desirable both from the standpoint of
high yield and less scab. The same writer (#2) from a field survey in
western Nebraska found clear indication that cultivation of fields the

year preceding potatoes tends to increase scab as contrasted with non-

. ' O Y Q ‘ O I O
cultivated crops. In the same region hastings (46) obtained Similar

_ h _

results from a study of 15 different crOpping systems.
Green manuring and antibiosis

Altho there are relatively few experimental data on the subject,
green manuring has been widely recommended as a control measure for
potato scab. Hillard (9M, 95), in England, obtained a reduction in
scabbing by adding organic matter to the soil in the form of green grass
or spent hOps at the rate of 10 to 20 tons per acre. Later Hillard and
Taylor (97) found that grass alone exerted no inhibitory action on

scabbing, but that when Actinomyces praecoz a saprOphytic species) and

 

Actinomyces scabies were both inoculated into soil mixed with grass, less

 

scab occurred. Meyers (92) in Holland, reduced the amount of scab by

the addition of soybean or turnip meal to the soil. White (156) found
that green manuring reduced the amount of scab in Kansas, and that green
manure in combination with sulphur was more effective than alone. Sanford
(112) reported that green manuring with rye at 50 tons per acre had no
tendency to reduce the amount of scab on heavily infested soil of pH 5.0-
5.3 in.Minnesota. Hiha (107) reported negative results with green manure
for scab control in Czechoslovakia. Dippenaar (28) got no control of scab
in Wisconsin with green pea vines as a manure, nor with sulphur in combin-
ation with peas as a green manure. As pointed out by Huisman (57) it is
well known that the disease is prevalent on plowed up grass lands, altho
the contrary might be expected from the large quantities of plant remains
in the soil. However, he reported that it had been noted that infection
had been reduced by a green manure of oats. It may well be that green
manuring is effective in reducing the scabbing of potatoes only where the
green manure serves as a medium for the growth of organisms that are

antibiotic to plant pathogenic actinomycetes.

-5-

That actinomycetes may be antagonized by other organisms in culture
media is a well established fact. Sanford (116) suggested that the
influence of cultural methods on scabbing is brought about by antagonism
to the scab organisms on the part of other organisms favored by the

conditions.

Millard and Taylor (96) found Actinomyces praecox a saprOphytic

 

species, to be antibiotic to g. scabies in culture media and in field
trials. Sanford (113) reported that certain bacteria inhibit the growth
of’é, scabies in culture principally through change in pH of the medium,
though one bacterium inhibited the Actinomyces by some other means. Wier-
inga and Wiebols (158) noted that certain bacteria parasitized actinomycetes
in culture. McCormick (91) made a study of the associative action of some
species of Actinomyces in culture media. He concluded that the antagon-
istic action of certain bacteria and of actinomycetes to other actinomycetes
is a result of a change in the oxidation-reduction character of the medium
due to the metabolic products of growth. Weindling (lug, 1M9) and Weind-

ling and Emerson (150) found that Trichoderma lignorum produces a substance

 

lethal to certain fungi which enables it to parasitize them. However,
Daines (2M) obtained no reduction in potato scab on the resulting crOp

by dipping the potato seed pieces in suspension of Trichoderma spores.

 

Sanford (116) suggested that antibiosis may play an important part
in natural control of potato scab. However, in the case of natural control
brought about by a wet soil condition, he theorized that the reduction in
scabbing was due to the exclusion of air from the soil thus inhibiting

the growth of Actinomyces scabies which is said to be strongly aerobic.

 

However, Dippenaar (28) obtained no increase in infection by aerating the

soil. Moreover, he observed that bacterial flora predominated over fungous

- 6 -

and actinomycetous flora in soils with a high moisture content. The
reduction in scabbing under such circumstances could be explained by
assuming that certain of the bacteria were antibiotic to the parasitic
Actinomyces. However, Lutman, Livingston, and Schmidt (72) made monthly
bacteria and Actinomyces counts over a.period of eight years from a field
where a badly scabbed crOp of potatoes had been harvested at the beginning
of the experiment. They found no indication of antagonism between soil
bacteria, fungi, and Actinomyces under field conditions, for the Actino-
myces counts roughly paralleled those of the total number of organisms.
' Furthermore, Waksman and Dubois (1M5) observed that actinomycetes are not
exterminated by soil amoebae as are other soil bacteria.

The possibility of controlling potato scab by means of promoting
the growth of soil organisms antibiotic to plant pathogenic Actinomycetes
is perhaps worthy of further study.

BacteriOphagy

 

Recently'Wieringa and Wiebols (158) have isolated a polyvalent
bacteriOphage for species of Actinomyces, including é. scabies, and they
suggest the possibility of using bacteriOphagy in controlling potato scab.
However, as yet no bacteriOphage for any plant pathogene has been utilized
in controlling a disease under field conditions.

Fertilizers

 

When physiologically acid fertilizers such as ammonium sulphate,
super phOSphate and potassium phosphate are used for potatoes, if there
is any effect on scabbing it is usually a tendency to reduce the severity
of the disease, many investigators having reported partial to complete
control (3, 5, 6, 12, 22, 32, M7, 57, 81, 82, 107, 120, 129, 153). On

the other hand chlorides (21, 32) and nitrates are reported to have the

Opposite tendency (123).

Lime generally aggravates scabbing, so much so that many early
observers supposed that its chemical effects on the potato were responsible
for the trouble. However, excessive liming inhibits scabbing (9), and
scab is said never to occur on weathered limestone (9, 128). Blodgett and
Cowan (9) found evidence that calcium itself has no effect on scabbing
except as it alters the soil reaction. This is borne out by Sibilia's
observation (123) that scab was prevalent in one locality where the soil
contained only one percent calcium carbonate, altho the soil had a pH
value of 8.3. Sibilia in Italy (123) and Schlumberger in Germany (120)
recorded experiments where a reduction in scabbing was effected by appli-
cations of lime, and Bolley (11) and Rang (106) obtained some control with
calcium cyanamide. It is noteworthy that Schlumberger obtained reductions
in scabbing both with lime and with acid fertilizers indicating that
change in soil reaction was not the factor involved in control.

Stable manure is an excellent medium for Actinomyces and has generally
been conceded to cause an increase in scabbing when applied on potato land
(3, M1, M7, M8, 6M, 66, 123, 130), yet Hahne and Chelard (56) in Germany
recommended liberal use of green manure and stable manure for scab control.
Goss (H2) from a survey in Nebraska found no indication that the use of
manure for crops in rotations with potatoes had resulted in more scab, but
rather the reverse as less scab occurred than following alfalfa.

Sulphur soil treatments

 

The vast literature on the use of sulphur for the control of potato
scab was well reviewed in 1927 by the Canadian workers, Duff and Welch (30),
who carried on experiments with sulphur in six Canadian provinces, and

concluded that sulphur at rates of MOO, 600, 900, 1200 pounds per acre

—8-

was not uniformly effective, but "promising in clay soils infested by
moderate numbers of attenuated strains of the organism, and under
conditions of light rainfall." Sporadic studies for half a century in
Michigan have indicated that sulphur soil treatment for the control of
potato scab is not an economic practice here (131, 1M6, 152). On the
.other hand, the New Jersey workers in most cases have reported economic
control of potato scab with sulphur, especially with inoculated sulphur
(MS-51, 67, 78-80, 83-86). A reduction in total yield often accompanies
sulphur treatments, though the yield of salable tubers may be greater
than on untreated plots. Caution must be exerCised in applying large
quantities of sulphur to the soil, for other crOps in the rotation may
be injured by the treatment (36, M0, 121, 122). Orton and Field (99)
reported injury to the tubers of the potato crOp from application of
sulphur in the furrow, andldorse and Shapovalov (98) obtained an.increase
of 20 to 30 percent in the number of plants diseased with Rhizoctonia
following sulphur soil applications.

Where sulphur is effective in controlling scab, the prOper time,
method, and quantity of application appears to vary according to the soil
and climate. Taubenhaus (133) was unable to reduce scabbing by broad—
casting sulphur on neutral and calcareous soils in Texas, though he obtained
complete control by applying sulphur in the furrow at rates of 500-1500
pounds per acre two or three weeks before planting. Martin finds that
sulphur in the furrow is injurious to potatoes in New Jersey, and he gets
best results by broadcasting 300-600 pounds of sulphur per acre with a lime
distributor and harrowing it in before planting. Merely rolling the seed

tubers in sulphur gives control Of scab under some circumstances (16, M8, 130),

whereas up to 1200 pounds per acre may be ineffective (28, M5).

-9-

Since potato scab is seldom of much importance on upland soils more
acid than pH 5.2 (28, 37-39, 135), it might be supposed that when the
reaction of the soil can be lowered to this point by applications of
sulphur a clean crOp of potatoes could be produced. However, sulphur may
inhibit scabbing without having any appreciable effect on the soil reaction

(

below pH 5.0 without affecting the amount of scabbing (30). From the evi-

\JJ

0, M5). On the other hand, sulphur may bring the soil reaction down well

dence at hand, it seems probable that acidification of the soil does not

kill the scab organisms, but inhibits their growth so that if such soil is
heavily infested, the potato tubers, which have a pH of about 6.5 (112, 151)
will come in contact with the spores which then germinate and cause infection.
If this is the case, control might be obtained by keeping the soil acid for

a considerable period of time before planting a susceptible crOp so as to
eliminate the scab-producing organisms by starvation. This hypothesis is
rendered some support by the results obtained by'Martin who, by means of
applications of sulphur and ammonium sulphate, reduced the soil reaction of

a field badly infested with scab to pH 5.1. After the soil had been limed

to bring the reaction back to a pH favorable for scabbing, there was scarcely
a trace of scab on the first crop of potatoes. However, the second crOp was
badly scabbed. Perhaps scab might have been eliminated completely until
reinfestation took place if the soil had been kept strongly acid for a longer
period of time.

Since sulphur soil treatments control scab in some cases where the soil
is so highly buffered that no appreciable change in soil reaction takes place,
factors other than soil acidity must be involved. Wilcoxon and ficCallan
(159) have shown evidence that sulphur is toxic to fungous Spores because

it exnibits an appreciable vapor pressure and is readily reduced to H25 by

living material.

-10...

Williams and Young (160) found that sulphur yields varying
amounts of toxic factors depending upon the reaction, oxidation,
temperature and moisture conditions. Sulphur treated with such oxidi-
zing agents as potassium permanganate, manganese dioxide, and arsenious .
acid was found to be extremely toxic to certain fungous spores. It was
found further that the toxic factor was destroyed by alkalis and strong
acids. Furthermore, as shown by Lipman, McLean and Lint (68) sulphur
oxidation affects the availability of mineral salts in the soil. Thus,
in some instances, sulphur may inhibit scabbing through its effect on
the nutrition of soil actinomycetes.

Soil disinfection with chemicals

 

Many toxic chemicals have been tried as soil disinfectants for
potato scab. Of these several mercurials, COpper sulphate, aluminum
sulphate, and formaldehyde in some instances have been reported to inhibit ,

scab. None have proved successful in Michigan.

Mercuric Chloride:

In 1895 Halsted began a series of trials of mercuric chloride as a
soil treatment for potato scab in New Jersey. That year on a plot near
Freehold he got good control of scab with applications of 30, 60, and 120
pounds of mercuric chloride per acre, but the yield in all cases was
materially reduced (#7). He also controlled scab with sulphur at rates
of 150, 300, and 600 pounds per acre, in which case the reduction in yield
was slight. However, since Halsted planted scabby seed-pieces and got
almost complete control of scab by seed treatments with mercuric chloride,
copper sulphate, kainit, or sulphur dust, it is apparent that he was not
dealing with soil-borne scab.

The same year, which was a very favorable one for potato scab,

-11..

Halsted tried some seed and soil treatments on the potato plots at the
-Station Farm. The scab was certainly soil-borne, for his seed treat-
ments failed completely. Here the trifling quantity of 36 gallons of
.lfl mercuric chloride solution per acre, and like quantities of Bordeaux
and cuprain reduced the amount of scab from 97% in the checks to 80, 70,
and 80% respectively, while sulphur at 300 pounds per acre reduced the
per cent of scab to five.

At New Brunswick in 1896'Ha1sted (he) applied a 0.1% solution of
mercuric chloride to the soil at the rate of M320 gallons per acre and
obtained a reduction of scab from 80% in the checks to 10% in the treated
area. However in 1897 (M9) mercuric chloride at 60, 30, and 15 pounds
per acre reduced the amount of scab only slightly altho the same plots
had received a similar amount of the mercurial two years earlier. He
concluded that "corrosive sublimate acts only feebly and not to an extent
to be observed by the untrained eye".

MacLeod and Howatt (7M) in Canada reported that they obtained good
control of common scab and Rhizoctonia scurf by mixing mercuric or
mercurous chloride through the soil, the chemicals being applied at the
rate of 10-15 pounds per acre, diluted 3 to l with diatomaceous or other
earths to facilitate application. The fungicides causfl.a slight reduction
in yield.

van der Slikke (12M) in Holland poured 0.1% or 0.05% mercuric
chloride solutions in the potato holes before planting and got good con—
trol of Rhizoctonia scurf and common scab at rates of 1/8 to l/h liter
of 0.1% solution per hill, and with l/u liter of 0.05% solution.

Johnson (61), in trials over a four year period in England, almost

eliminated common scab and Rhizoctonia scurf with applications to the

soil of mercuric chloride either dry or in solution, at rates amounting

to lO-MO pounds per acre.

Taylor (135) in New York failed to control scab with mercuric
chloride at 5 pounds per acre. In another field there was significantly '
more scab where mercuric chloride was added to the soil at 9 pounds per

acre than in untreated soil.

Other Mercurials:

Apparently the various mercury compounds that have been used as soil
disinfectants for potato scab give similar results under similar circum-
stances. Thus in New Brunswick, Canada, calomel and corrosive sublimate
were equally effective in controlling scab at 10-15 pounds per acre (7h);
so also on Long Island calomel and yellow oxide of mercury each controlled
scab at u—6 pounds per acre; In Ohio neither Semesan Bel nor calomel at
M pounds per acre appreciably affected the severity of the disease; while
in western New York and at various points in.Michigan soil treatments with
mercurials increase the severity of potato scab (3M, 35). In New Jersey
where Halsted had gotten erratic results with mercuric chloride, Martin
(87-89) has gotten varying results with several organic mercuries, calomel,
and yellow oxide of mercury. In some soils he has consistently controlled
scab with mercurials, while in other soils the treatments have failed.

Where mercury compounds fail to control scab they generally show their
effect by causing an increase in scabbing, often two or three-fold. In
view of the fact that mercurial seed treatments also consistently increase
scabbing in some soils, it may be that the effect of the mercury is to
make the host plant more susceptible to the disease. Otherwise it must
be assumed that the mercury migrates through the soil from the furrow in
which it is applied and affects the soil flora over all the area where

tubers are set. In the latter case, either the weak mercury solution

_ 13 -

stimulates the growth of Actinomyces, or has an adverse effect on other
soil organisms whidh compete with or are antagonistic toward the patho-
genic Actinomyces. Evidence presented by Frutchey and Muncie (35)
indicates that mercurials do affect the soil flora, the effect depending
upon the moisture content of the soil. However, the amount of mercury
added to the soil on potato tubers that have been soaked one or two hours
in a 0.1% solution of bichloride of mercury must be very small.

Another factor to be considered is the marked effect of other salts
on the solubility of mercury compounds as shown by the work of Clark (18),
Rosa (109), and many others. Consequently, the chemical composition of
the soil solution may be an important factor influencing the effectiveness
of mercurial soil treatments for potato scab.

The effect of the use of mercurials on yield has been as various as its
effect on scabbing, Taylor (13%) reporting an increase in yield in pronor-
tion to the effectiveness of the mercurials in increasing scabbing, Martin
sometimes getting a reduction in yield, and Eddins (31) reporting marked

injury.

Other Chemicals:

Aluminum sulphate, which has been used effectively in controlling
Rhizoctonia damping-off of conifers (157). was found ineffective at 20
pounds per acre for potato scab in Michigan (3M). Dippenaar in Wisconsin
(28) failed to control scab with applications at rates up to 1080 pounds
per acre. However, Taylor (13”) reports that in western New York aluminum
sulphate gives partial control of scab but also causes a reduction in
yield.

Halsted (M9) applied copper sulphate to the soil at rate of 300, 150,

and 75 pounds per acre and reduced the percent of scabby tubers to 5, 5,

- 1h -

and 2% respectively as compared with H75 scab in the check. However,

seed treatment alone gave even better control so that he obviously

was not dealing with a soil infestation of the scab organisms. Halsted

in New Jersey (M9) and Mader and Blodgett in western New York (77)

reported a reduction in scab following frequent heavy applications of
Bordeaux mixture to the foliage. Halsted found that Bordeaux mixture
applied to the soil at M320 gallons per acre at planting reduced the amount
of scab in some instances only. Lutman and Cunningham (70) failed to
control scab in Vermont with applications of 600 pounds per acre of COpper
sulphate.

Halsted (99) reported that carbon bisulphide, benzene, and kerosene
each at 120 pounds per acre had little effect on potato scab. Millard (93)
got negative results with creosote and bleaching powder. Halsted (#9),
van der Slikke (12h), and Johnson (61) failed to control scab with formalde-
hyde as a soil treatment, while Hiha (108) found formalin partially effective
at high concentrations.

Acids, when used in controlling potato scab, if effective are prob-
ably so through their effect on the soil reaction. Halsted (M9) obtained
negative results with oxalic acid at 120 pounds per acre, fiiha got partial
control with phospheric acid. Reports on the use of sulphuric acid are
almost as numerous and equally as erratic as those for sulphur.

Soil conditions influencing scabbing

 

Soil type, temperature, reaction, moisture content, and infestation
are all important factors influencing the incidence of potato scab. Scab
occurs on almost any type of soil - gravel, sand, loam, clay, muck -
except on weathered limestone. It is more likely to be severe on sandy

,and on other well-aerated types of soil than on heavier types, even though

Fousek (33) found a much lower ratio of Actinomyces to bacteria in sandy

- 15 -

soil than in loam.

From field observations made in EurOpe and America, Jones and
McKinney (62) concluded that scab is more prevalent in regions having
warm growing seasons than in regions where cool summers prevail, and
likewise a greater amount of scab seems to develOp in a given locality
during a warm season than during a cool one. The same investigators (63)
produced scab eXperimentally at constant temperatures ranging from 110 C.
to 35.50 C. and considered 220 C. the Optimum temperature for scab
development. Dippenaar (28) obtained scab over a range of 13° C. to 25° C.
with approximately 20° C. as the Optimum. Sanford (110) under controlled
moisture and temperature conditions obtained a maximum amount of scab at

IMO C., 17° C., and 25° C. The scab organisms thrive better at a some-

what higher temperature. Dippenaar (28) using three strains of Actinomyces

 

g

scaoies found their Optimum temperatures to be 28°, 28° to 32° , and 32°
to 36° C. respectively. Cocchi (l9) studying three strains of plant
pathogenic Actinomyces (é, flavus, é, clavifer, and an unidentified species)
found them to grow from 100 C. to ”00 C. with the best development at around
25° - 30° C. However, Wingerberg (161) found that the Optimum temperature
for Actinomyces in culture was dependent upon the medium upon which they
were grown as well as upon the reaction of the medium.

Scab is most prevalent on slightly acid to alkaline soils. Generally
soils with a reaction lower than pH 5.0 or even 5.3 give little or no
scab (8, 37-39, 13M-l36), but the disease has frequently been reported
severe at much lower readings (12, 15h), down to pH 3.3 (30). BOysen (12)
on experimental plots recorded scab at pH 3.6 and severe scab at pH 3.7
with the most severe scab at pH h.h—M.5. Reports as to the upper limit of

soil reaction for scabbing are equally as variable as those for the lower

limit. Smith (125), from field observations in western New York, concluded

- 16 -

that the Optimum soil reaction for scabbing is pH 6.08-6.51 below and
above which the disease is less severe. Wessels (15h) in Long Island
found that the severity of scabbing continued to increase with rise in

pH up to 6.9 or 7.0. Goss (M2) found the reverse to be true in Nebraska.
He reported a very evident and consistent decrease in both the amount and
severity Of scab as the pH values increased from 5.92 to 8.25. Millard
(9h) concluded that soil reaction is not a direct factor in scab control
for scab may occur at pH M.h and is found in only slight amounts in soils
of high pH, while on more nearly neutral soils there is no relation between
soil pH and scab. In the present study the writer found no correlation
between soil reaction and scabbing over the range of pH 6.2-8.h on his
eXperimental plots. Blodgett and Cowan (9) in field surveys found little
scab on soils more alkaline than pH 8.3. However, Sibilia (123) reported
that scab was prevalent in one locality where the soil pH was 8.3. San-
ford (111) has shown that the scab organisms thrive on media as alkaline
as pH 8.0-8.7. Cocchi (19) found that the maximum reaction at which the
strains Of Actinomyces that he studied would grow to be about pH 9.0.

Waksman (lhh) reported that the limiting acid reaction for Actinomyces

 

scabies in culture solutions, prOperly buffered, and in sterile soil
varies with the strain of the organism. In the majority of cases the
limiting acid reaction was about pH 5.0-5.2; some strains grew even at

pH n.8, while others began to develOp only at pH 5.3-5.6. The Optimum
pH of soil cultures was 5.8«7.7, and the limiting reaction pH 8.8. This
is in accord with the report by Snow (126) who studied the flora of wind-
blown soils from 6 regiOns. In Arizona arroyo banks with a soil pH of
8.6-9.0 she found 52% of the organisms to be Actinomyces. However, only

10% of the soil organisms were Actinomyces in soil from Death Valley,

- 17 _

..
and only 0.66 in soil from Shackleford Bank, N. C. The reactions Of
these two soils were pH 8.9-9.0 and pH 9.0-9.2 respectively. Soils
from sand banks in three other regions gave 15 to M58 Actinomyces,
with a soil reaction range Of pH 5.9-8.0. From these results it appears
that in the type of soil studied, actinomycetes do not thrive at a pH
higher than 8.9 or 9.0. As pointed out by Millard (9M), many neutral
soils produce little or no scab.

From empirical observation potato scab has generally been regarded
as a disease of relatively dry soils. Sanford (110), Martin (80), and
Dippenaar (28) have all demonstrated experimentally that scabbing decreases
with increasedsoil moisture. On the other hand, Schacht, 185M, (117)
ascribed the disease to "heavy moisture of rich soil". Lutman and Cunning-
ham (70) stated that "apparently excessive moisture does materialbrincrease
scabbing". Voelkel and Klemm (131) recorded very severe scabbing during
an unusually wet year. MaCMillan (75) found that formaldehyde seed
treatment was non-effective against scab under irrigation where mismanage-
ment in the use of water caused an excess of soil moisture for an extended
period at any time during the early stages of tuber develOpment, and that
steadily growing plants, either treated or untreated, maintained free
from excess of drought or moisture appeared to escape the disease a
longer time than where imprOper application of water had occurred.

Soils thoroughly infested with plant pathogenic Actinomyces may
remain so over a considerable period of years and produce a scabby crop
.ny time potatoes are planted. Several investigators have expressed
doubt as to the value of crOp rotation for scab control (119, 139).
However, crop rotation is sometimes fairly effective in controlling scab.

In a case of this kind Lutman, Livingstone, and Schmidt (72) made monthly

- . o .. o .4
counts of the s011 organisms during eight years beginning in 192”. 99.2p

-13..

of the 1916 crOp was badly scabbed. The field was not planted to potatoes
again until 1935. That year only 3.3% of the tubers were scabbed although
many Of the tubers counted as clean in the latter crop showed a russeting
of the skin either in spots, over large areas, or Over the entire tuber;
yet during the 8 year period the number of actinomycetes in the soil had
neither increased nor decreased. The authors suggest the possibility that
the scab-producing actinomycetes are weakened in pathogenicity after a long
period of deprivation Of their host, the potato tuber, and live saprOphy-
tically in the soil, gradually acquiring pathogenicity once more when pota-
toes are planted again.

Actinomycetes constitute a considerable portion of any soil flora
amounting to 20-30%, 308, and 37.58 of the total organisms according to
counts by Hiltner and Stromer (55), Krainsky (65), and Conn (20) respectively.
Waxsman and Curtis (193) found 3.5-h6fl actinomycetes in 25 soil samples from
various parts of North America and Hawaii. ~Both Beijerinck (M) and Waksman
and Curtis (193) found the ratiO‘ of actinomycetes to bacteria in the soil
to increase with depth. Beijerinck reported actinomycetes common at a
depth of one meter in garden soil, and present at a depth of two meters
below the surface of sand, at three meters in alluvial mud, and abundant
in river water. The ratio Of actinomycetes to total Organisms has been
found by Fouseck to vary with soil type (33), and with soil acidity by
Jensen (59). Snow (126) found 52% of the colonies derived from wind-blown
desert sand in Arizona to be Actinomyces. Accordingly virgin soil could
be readily infested with pathogenic actinomycetes by means Of wind-blown
spores. However the occurrence of potato scab on virgin soil could also
be explained by Lutman's (72) acquired pathogenicity hypothesis.

A large number of strains of Actinomyces are capable of causing

potato scab. American authors, although fully cognizant of the fact that

_ 19 -

there are several types Of potato scab from the standpoint of appear-
ance, and that the organisms Vary greatly in their morphology and
physiology in culture, have generally considered these as being races
of a single species. On the other hand, EurOpean authors have named
about twenty species of Actinomyces that are pathogenic on potato tubers
(95, 162). Recently Taylor (137) in this country has undertaken an
extensive study of soil actinomycetes with a view to separating them into
species on their physiologic characteristics.
The species of Actinomyces that have been described as parasitic

on potatoes vary greatly in their ability to utilize various carbon
and nitrogen sources (19, 29, 96, 138, l62),as to their oxygen, tempera-
ture, hydrogen-ion potential, and redox potential relations (91, 157),
as to their response to association with other organisms (91), and as to
the type of scab produced (19, 27, 58, 95, 162). As demonstrated by
Wingerberg (161), the Optimum temperature and Optimum pH of a given
strain is dependent upon the medium on which it is grown. Consequently
Vdifferent soils might be expected to harbor different strains Of Actino-
myces, with the result that the soils would reSpond in various ways to
treatments for the control of potato scab.

' Quoting from Jensen (60), "The -—-- practice adopted by'Millard
and Burr, 1926, of establishing species differences on the basis of
every Observed constant difference, is certainly logical, but hardly
practical, since nearly every strain of Actinomyces isolated
from a plating from an ordinary soil could then be raised to the rank
of species." It is clear that the number Of strains of soil Actinomyces
is a legion and that many of them are capable of causing scabbing of

potatoes. Since fungicides are generally specific, controlling certain

disease organisms and not others, it is hardly to be expected that a

-20-

single chemical applied as a soil treatment would control all the

strains of plant pathogenic actinomyces in every soil.

THE PROBLEM

McCallan and Wilcoxon (91),.in studying the relation of
fungicidal action to the periodic system of the elements, tested

the toxicity of about 50 elements to the spores of Sclerotinia

 

americana, Botrytis paeoniae, Pestalotia stellata, and Uromyces

 

caryOphyllinus. They listed the elements in the descending order

 

of their toxicity to the four fungi: g, Os, Hg, Ce, Ru, La, Cd,
U, Cu, Y, Er, Nd, Pb, Au, Th, A1, Th, Pd, Mn, Zn, Ni, Co, Cr, As,
Pl, Ta, Va, and Ti. The sulphur group and the halogens are omitted
from the list because the toxicity of these elements varies greatly
according to the compounds used.

Of this list only mercury, copper, and aluminum compounds had
been tested for potato scab control, and these had all given conflict-
ing results. The purpose of this study was to test other chemicals

for their value as soil disinfectants for potato scab.

-22-

GREENHOUSE STUDIES

Procedure:

*3

rials in the greenhouse were conducted in 6-inch and S—inch pots,
with three pots for each treatment. The soil was a light sandy loam
with a moisture equivalent of about 30% and a pH value of about 7.5.
The tap water used for irrigating the pots had a reaction of about pH
7.8. Infestation of the soil was insured by mixing a tablespoonful of
macerated scabby potato peelings through the soil in each pot. Rates
of treatment per acre were based on the surface area of the pots. The
dry chemicals were diluted 9 to 1 with oven-dry sand to facilitate dis-
tribution and were mixed thoroughly through the tOp four inches of soil
in the pots. The creosotes were diluted 9 to l with acetone so that 20
gallons per acre of creosote would also mean 180 gallons per acre of
acetone. Untreated tubers of Y.tahdin potatoes were planted in all cases.
With the exception of experiments III and IV, the potates were planted
the same day that the soil was treated.

In recording the amount of infection that occurred during the
various treatments, exact methods of measuring scabbing were considered
unnecessary since control was the goal sought. The scab readings, which

are recorded in tabular form, are arbitrary estimates.

Experiment I

 

Chemicals tried: Potassium permanganate, COpper sulphate, cerium
oxalate, nickel cyanide, potassium dichromate, and sodium fluoride each
at rates of 5, 15, and 50 pounds per acre, Formacide (a proprietary compound
containing formaldehyde) at 50, 325, and 650 pounds per acre, and coal tar

and wood creosote each at 1, 5, 20 gallons per acre. The potatoes were

-23..

planted in S—inch pots January 20, 1936 and harvestedllarch 30. The
pots were randomized at the beginning of the exneriment and again a
month later to compensate in a measure for variations in light and soil
temperature. The temperature of the greenhouse was maintained at about
25° c. by day-and 20° C. by night.

As shown in Table I the control plants were heavily scabbed. Many
of the treatments gave as much scab as the controls or perhaps more.
No chemical reduced the amount of scabbing at all the rates of treatment
employed, but c0pper sulphate and nickel cyanide each at 50 pounds per

acre appeared to reduce somewhat the amount of scabbing.

xperiment II

 

This was largely a repetition of Experiment I using most of the
chemicals at higher rates, substituting red c0pper oxide for c0pper
sulphate, and adding aluminum chloride and calomel to the list. The
potatoes were planted in 6-inch pots March 27, 1936 and harvested June 6.

As shown in Table II the only case of apparent control occurred where
nickel cyanide was applied at 500 pounds per acre, although 150 pounds
was ineffective. Calomel at 150 pounds per acre was markedly injurious
to the potato plants. The tubers were very small, and one plant that

bore no tubers had very scabby rhizomes.

Experiment III

 

One—half liter per 6-inch pot of 0.1% solutions of each of nine
metallic salts - copper sulphate, potassium permanganate, nickel nitrate,
lead acetate, potassium dichromate, sodium fluoride, zinc sulphate,
cobalt chloride, and mercuric chloride, was applied as soil disinfectants

for potato scab. The soil was treated a week before planting. On the

basis of surface area of the pots, the quantity of the chemicals

-221-

employed amounts to about 250 pounds per acre. A half liter of water
was added to each control pot. The potatoes were planted February 28,
1936 and harvested April 17. The complete absence of scab on the checks
at the end of six weeks may have been due to the fact that the soil was
kept rather wet. However that m.y be,in equally wet soil one or more

of the plants under each of the treatments except mercuric chloride

produced scabby tubers as shown in Table III.

Experiment IV

 

Aniline dyes have been shown to be highly toxic to many micro-
organisms, but gentian violet at l and 10 pounds per acre and malachite
green at l, 10, 50, and 150 pounds per acre as soil disinfectants showed
no tendency to control potato scab (Table IV). At the same time, New
Improved Ceresan (5% ethyl mercury phosphate) was tried at 5, 15, 50, and
150 pounds per acre. 150 pounds of this material per acre was markedly
injurious to the potato plants but did not eliminate scab. The chemicals
were applied dry to the soil on'March l. The potates were planted in

6-inch pots March 3, 1937 and harvested May 15.

l
R)
XII
I

FIELD STUDIES

Some of the same chemicals were tested in the field to determine
whether or not they would give results similar to those obtained in
the greenhouse. Yellow oxide of mercury and borax were added to the
list. Corrosive sublimate was tested by the same method that van der
Slikke used, (12H), pouring one liter of l-lOOO HgCl2 in the planting
holes before planting. All the other chemicals were tried at three rates
each. They were mixed with dry soil and applied in a band about four
inches wide in the bottom of the furrow. Calomel and yellow oxide of
mercury were employed at 5, 10, and 20 pounds per acre and red c0pper
oxide, lead sulphide, potassium dichromate, potassium permanganate, borax,
zinc oxide, and sodium fluoride were used at 5, 15, and 50 pounds per
acre. Each treatment consisted of a block of 20 hills, M rows wide and
5 hills long, and was replicated twice giving 60 hills. Six similar
blocks were left untreated as controls. All the blocks were randomized.

The land available for this eXperiment had been treated with varying
amounts of sulphur and lime two years earlier in a study of the effect of
soil reaction on gladiolus scab. At the time the potatoes were harvested,
the soil pH varied from 6.0 to 8.u. This was regarded rather as an advan-
tage because it gave an Opportunity to observe whether soil reaction would
affect the results from the soil treatments. An attempt was made to
determine the "average" pH of the soil of each block, and the results which
may be regarded as approximations are recorded with the results of the
trials in Table IV. The soil was a light sandy loam with a moisture equiv-
alent of about 50%. The chemicals were applied and Katahdin potatoes

planted on June 9. In an effort to insure infestation, a water suSpension

of macerated scabby potato peelings was sprinkled in the furrows, and all

-26-

the seed pieces were dipped in this suspension. However, this method
of soil infestation was apparently of little value in the dry summer
of 1936 since there was no more scab and no less variation in scabbing
from hill to hill in the check plots of the experiment than there was
in the border rows where the relatively clean seed tubers were soaked
one hour in a cold l-ZMO formaldehyde solution and where no inoculum
was employed. The crOp was harvested September 30.

Due to very dry weather following planting, a poor stand was obtained
so that the number of hills per block at harvest varied from 8 to 20. The
blocks were harvested separately and the tubers graded for scab as heavy
(50-100% of the surface scabbed), medium (eo-Eofi), light (2-20%), trace
(less than 9fl), and clean. The per cent of scabby tubers from each treat-
ment does not give so vivid a picture of the effect of mercurials on
scabbing as can be obtained by expressing the scabbing in per cent of the
surface area of the tubers scabbed. These latter figures are estimates
obtained by arbitrarily assigning 70%, 30$, 10%, and 1% as the average
area of the tubers scabbed in the heavy, medium, light, and trace classes
respectively. Variation in soil reaction was ignored in obtaining these
figures, since any effect pH may have had was not obvious.

Potassium permanganate and the mercurials appear to have caused an
increase in scabbing, whereas there was less scab with lead sulphide
at 15 and 50 pounds per acre, potassium dichromate at 50 pounds and zinc
oxide at 5 and 15 pounds. None of the treatments gave control of potato
scab in any of the replications. unere reductions in scabbing occurred
the differences are not statistically significant., None of the treatments
affected the stand of potatoes. The numbers involved were too small to

determine what effect, if any, the treatments may have had on the yield.

However, Hester and Carolus (5M) found that cOpper, manganese and zinc

-27-

sulphate applied to the soil at 50 pounds per acre separately or 25
pounds per acre of each of the three in combination had no effect on the
yield of potatoes in Florida. Vandecaveye (1H0) found that lead as a
soil treatment retarded the growth of barley and alfalfa seedlings. The
erratic effect of mercurial soil treatment on potato yields is discussed

earlier in this paper.

The relation of soil reaction to the effect of mercurial soil

 

treatments on scabbing of potatoes

 

As stated in the preceding experiment, the ground on which the
experiment was conducted varied widely in soil reaction. In order to
determine the influence of this variation in soil pH on the effective-
ness of mercurial soil treatment, calomel and corrosive sublimate were
applied at rates of 5, 10, and 20 pounds per acre in 5 hill plots, with
12 replications, and 23 plots left untreated. The plots were randomized.
The methods employed in applying the chemicals and infesting the soil
were identical with those of the precedi-g experiment. The plots were
planted to Katahdin potatoes June 9, 1936. The hills were harvested separ-
ately September 30. A soil sample was taken from around the tubers in each
hill and its pH determined colorimetrically.

The methods employed in arriving at the pH of the soil of each hill
are open to certain objections. Only one sample was taken from each hill,
and these were collected in paper bags and permitted to dry out. The
effect of air drying soil samples on the pH readings is thoroughly discus-
sed by Snyder (127). Drying the soil samples generally has a tendency to
slightly lower the pH readings especially in highly alkaline soil, but
with some soils there may be a slight tendency in the Opposite direction.
Soil pH may vary during the growing season (127). In the present instance,
a few of the random samples taken in June gave pH readings of 5.7 whereas
the lowest reading obtained in October was pH 6.0. Only the readings from
the samples taken at harvest time are recorded in the data presented here.
It would perhaps have been less objectionable to have taken the samples

during the period of tuber formation. In determining the pH of the samples

colorimetrically two indicators were used in each instance, and where the

l
R)
‘..O
I

results were not comparable the determinations were repeated.

In Table VI the results of the mercurial soil treatments are given
without regard to soil reaction. It will be noted that one-half of the
tubers in the check hills and from 26-kofl of the tubers under the various
treatments completely escaped scab. Because of this great variability
the differences obtained are not statistically significant. However, the
data show that there were decidedly more medium to badly scabbed tubers
where mercurials were used than in the checks. In Table VII the scab

for hills at each pH readins is given separately for each treatment.

L)

ratin

LR

These are summarized in Table VIII. The data are presented in Table IX

in bar graphs and the hills classified in groups according to the soil
reaction in one-half instead of one-tenth pH units. Using these larger
groupings it will be noted that with every treatment over the entire pH
range there was decidedly more scab than in the checks. There appears to
have been little if any relation between scabbing and soil reaction in the
checks, heavily scabbed hills occurring over the entire pH range. In hills
treated with mercurials the amount of scab increased with rise in pH up to
about pH 7.U, at which point with all the treatments where several hills
were concerned there was a decided dropping off in scabbing with a rise

again at about pH 8.0.

-30..

Greenhouse Trials

of

Chemical Soil Treatments

TABLE I

Results of Erperiment I

 

Treatment

Pounds per
acre

Scab

 

 

Check

\N

r:

 

CuSOu

 

Ki LnOu

 

[U {(3 F‘PJCD(D<D<3 firm)

 

mam)2

 

K20r204

<D<D<DPJFJI

cmxxmrarordru14caeru<3taxaca

$r$r$5kaudnakukux-:1p-#*N>#flx

 

 

Formicide

325

 

Coal tar
creosote

1 gal.
5 gal.
20 gal.

F‘RJRDRJ$7FJRJVJC)

n3$f$fifnfivJ£rsa

M
‘f—

#Tn345trirn3be45n3

 

Wood creosote

1 gal.
5 gal.
20 gal.

 

 

I'-‘

H

 

NPR)

 

kurukn

 

i-II’KNNt-‘O

clean

trace of scab
slightly scabbed
moderately scabbed
heavily scabbed

no tubers

plant died

Greenhouse Trials
of
Chemical Soil Treatments

TABLE II

Results of Experiment II

_A_

Treatment Pounds per Scab

 

acre a b

 

O
:3.
O
Q.
'1
47C)

 

Lfl,4

 

tNtA
C) \51

 

U"! (3 0'3 C.) \J1\Jl

CeCEOu 500

 

Hi( CIT-)2

 

Kecrzoh 15

 

150
NaF SOO

 

5
PbS 15

50
150

 

150

A101 500

 

5
HgCl 50
150

aINH Ol—‘F’Jr-C'H NWWKNKJJ-FI'OKNl—J \NNNWWOI—‘H-‘TN

I'

 

 

 

H
‘Jl
:3

(3(314 (DPJ-CNNIAEA +4+4+4+4l4ro C3r454 <3<3 F‘l +4<3 ltd

 

clean

trace of scab

slightly scabbed

moderately scabbed

heavily scabbed

no tubers

no tubers but rhizomes heavily scabbed
plant died

swan-IO

it

mm mwrzrfiwwwrr OWE—J wmef-F—‘Lw-P’JI‘ w

 

Greenhouse Trials

of

Chemical Soil Treatments

TABLE III

Results of Experiment III

 

 

 

 

 

 

 

 

 

 

 

 

Treatment Scab

a b C
Creek 0 O O
CuSOu O 2 2
1(an)4 o o 2
Ni(no3)2 o 1 2
Pb(02H302)2 2 2 2
K20r207 O O 2
Na? _ h u
ZnSOu 2 2 3
00012 O 2 2
Hg012 O O O

 

 

 

 

F’WNI—‘O

clean

trace of scab
slightly scabbed
moderately scabbed
heavily scabbed
plant died

Greenhouse Trials
of
Chemical Soil Treatments

TABLE IV

ya
.‘J

esults of Emperiment IV

 

 

 

 

 

 

 

 

 

 

 

Treatment £ounds per Scab
acre a b 0
Check h h M
New Improved 5 2 2 M
Ceresan 15 M H M
50 2 u 1+
150 0*: 1*: 1st
Gentian Violet l 2 3 3
10 3 3 1+
Malachite Green 1 3 3 U
10 3 1L 1+
50 - 2 1+
150 3 1+ 2+
O = clean
1 = trace of scab
2 = slightly scabbed
3 = moderately scabbed
h = heavily scabbed
** = Tubers very small
- - plant died

- 3M -

TABLE V

Field Trials of Chemical Soil Treatments

 

 

 

 

 

 

 

 

 

 

 

 

 

1bS7 pH No. Av. 8 of
Treat« per of No. of of NO' Of Scabby Tubers % surface area
menthacre soil tubers hills Heavy Medium Light Trace Clean clean scabbed
Check - 6.8 39 1h 2 2 2 1 32
7.7 73 1“ 3 8 6 3 53
6.7 55 In 5 5 3 11 31
7.5 57 11 o 5 9 1 M2
6.6 50 2o 0 8 10 7 25
7.3 57 16 6 29 9 h 9 58 9 8
H801 5 7.6 67 15 11 7 15 3 31
6.8 71 18 1 13 20 u 33
7.0 62_1 1h 12 16 175 555 12 38 17.5
10 6.5 50 15 h 2 5 2 37
6.5 53 16 3 6 11 3 30
6.8 57 in 1h 9 12 7 15 51 1n.2
20 7.8 87 1h 3 5 16 h 59
6.6 52 18 2 2 1 o u7
6.9 59 13 1o 11 9 8 16 63 9.7
HgO 5 6.6 38 15 1 3 h ' 5 25
6.5 32 15 o 1 3 u 29
7.5 68 18 11 31 16 2 8 M1 15.5
10 7.6 62 1h 0 11 8 8 35
6.5 63 2o 7 h 7 1o 35
6.6 65 15 12 17 20 h 12 M3 1u.o
20 7.7 58 12 6 9 13 6 23
6.9 88 17 51 28 5 M o
6.5 M7 13 3 5 19 9 11 28 30.5
ch12 1 gm. 6.9 8 13 2h 18 3 8 5
per 7.0 1 9 5 u 10 2 20
6111 6.5 67 15 o 9 18 15 15 26 21.1
Cu20 5 7.1 38 15 1 1 3 1 32
6.5 26 12 o h o o 22
7.1 #373 8 37 12 8 5 5 58 11.7
15 7.9 68 1h 11 9 9 7 39
7.0 ”3 17 1 2 1 3 36
7.1 52 19 o 11 15 "7» 19 58 7.8
50 6.8 56 19 1 2 h 0 M9
6.7 60 17 1 2 6 3 n8 -
7.3 an 12 6 8 8 3 9 66 8 8

 

 

 

 

 

 

 

 

 

 

 

 

-35..

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lbs. pH No. A. f
Treatq par of No. of of N0. of Scabby Tubers i su:fa§e°area
mentnacre soil tubers hills Heavy Medium Light Trace Clean clean scabbed
FbS 5 7.7 MM 9 0 2 M 5 33
6.7 7M 16 7 8 5 3 51
6.5 26 10 1 10 9 1 5 62 9.M
15 7.9 61 1M 1 1 3 3 53
6.9 M0 17 3 1 3 h 29
7.2 56 18 1 10 1M 15 16 62 5.9
50 8.2 52 1M 3 1 M 0 MM
- 6.8 57 13 0 M 6 1M 33
6.5 52 12 0 1 7 6 38 71 3.6
K c 0 5 6.9 63 20 2 3. 11 8 39
2 2 # 6.7 57 18 0 1 M 6 M6
6.8 92 17 11 35 28 9. .9 MM :12.0
15 6-9 56 20 O 2 M 9 M1
6.8 6M 16 0 5 1M 2 M3
7.2 6M 20 155 2M 6 5 1M 531 12 2
50 6.8 52 16 0 3 6 o “3
7.3 M5 11 1 M 10 7 23
7.2 M5 16 0 2 6 5 32 69 M.0
KMnOu 5 7.M 29 11 3' 6 6 a 11
7.0 M7 10 0 M 9 30
6.6 59 10 59 0 0 0 0 30 35.5
15 6.9 M0 13 1 2 M 0 33
6.8 32 1M 0 2 2 1 27
7.3 51 1M 6 16 19 6 M 52 11.0
50 7.6 70 1M 0 3 10 2 55
7.5 72 17 1 7 6 o 38
6.9 58 19 1 18 22 10 7 56 1M.6
He no 5 6.9 7M 17 0 0 M 2 68
23 7 _7.2 M8 16 1 M 9 7 27
1.1 5M 12 1 7 1.5 0 28 70 M.6
15 7.0 70 16 M 8 5 r M M9
7.6 79 15 0 5 M 10 60
6.7 M8 13 0 16 16 7 9 60 7.2
50 6.9 35 1M 6 3 5 3 18
6.9 63 18 3 0 0 12 M8
7.2 51 13 #5 22 11 6 7 »M9 - 13.7
ZnO 5 7.0 M3 17 0 7 5 3 28
6.9 M3 10 O 5 7 5 26
6.7, 60 20 1 12 17 1o 20 51 6.6
15 8.0 62 16 2 M 8 9 39
6.3 52 17 1 0 7 5 39
6.] 68 19 o 5 15 13 35 63.2.; 11.11

 

 

 

 

 

 

 

 

i163. pH No. Av. ¢of
Treat- per of N0. of of No. Of Scabby Tuber 9 % surface area
men acre soil tubers hills Heavy Medium Light Trace Clean clean scabbed
50 7.6 58 10 M 2 5 5 M2
7.6 69 19 3 5 5 5 39
7.1 77 18 11 19 23 9 15 M7 12.0
mar 5 6.6 36 1M 0 2 5 M 25
6.M 57 16 0 0 M 1 52
7.2 77 1M 18 29 111 .5 8 59 1M.6
15 7.9 60 1M 3 9 M 5 39
6.5 M9 15 0 0 2 5 M2
7.3 32 10 3 0 7 2 20 _”72 5.9
50 6.9 6M 18 M 3 2 2 5
6.7 M3 15 2 2 2 g 3
7.3 59 18 5 5 19 26 68 7-9

 

 

 

 

 

 

 

 

 

 

 

-37..

TABLE VI

The Influence of Mercurial Soil Treatments on Scabbing

 

 

 

Scab ( 6 ) 5 of surface
Treatment N0. tubers Heavy ‘Medium ‘Lfgfit race Clean area scabbed
Check 791 5.M 12.9 2M.6 6.6 50.M 10
ch1. 5 lb. 338 15.M 17.8 23.7 5.9 37.3 19
ch1. 10 363 29.2 26.7 23.7 MM.1 36.3 31
HgCl, 20 352 - 26.M 27.9 21.6 3.1 35.2 29
ch12, 5 M07 27.8 27.3 20.1 3.7 M0.7 30
H5012, 10 261 18.8 2M.5 2M.2 6.1 26.1 23
H5012, 20 239 23.M 32.6 28.8 3.3 23.9 29

 

 

 

 

 

 

 

 

_ 3g -

 

 

 

 

 

 

 

 

 

TABLE VII
gelatin of Soil Reaction to the Effect of Mercurial Soil Treatments on Potato JS_c_ab
Soil I
3980- $011 No N0 N0. Of Scabby Tubers % of Surface
tion reatment hills tubers Heavy Medium Light Trace area scabby clean tubers
Check 0 - - - - - - -
HgCl,5]lbs 1 12 0 8 33 0 6 58
I 10 I 0 _ _. .. - _. ._ ..
6pg . 20 fl 0 - - - - - - -
o 1 ’51b 0 " ‘ "' " "‘ - "
I! 210 n1 0 - _. - .. - .. -
u 20 N 1 12 33 17 25 0 21 25
Check 0 - - - - - - -
H801. 5 O - - - - - - -
' 10 0 - - - - - - -
.9 ~ 20 o - - - - - - -
HgCla. 5 0 - - - - - - -
a 10 1 3 0 33 0 33 10 33
u 20 0 - - - - - - -
Check 3 35 0 3 26 11 M 60
8801. 5 1 6 17 17 17 0 18 50
pH . 10 1 9 11 67 22 0 30 0
6.2 ' '20 0 ’ ' ‘ “ ‘ ‘ “
ch12. 5 2 20 20 20 25 0 23 35
' 10 2 13 8 15 31 0 1 M6
' 20 M 23 26 MM 22 0 3 9
Check M 28 M 21 3 M 13 32
ch1. 5 3 21 10 19 2 0 15 M8
pH ' 10 1 5 M0 20 M0 0 38 0
6.3 M 20 0 — - - - - - -
H8012. 5 0 - - - - - - -
n 10 0 - - - - - - -
I 20 1 8 0 25 63 0 3LL 9
Check 3 3M 0 9 29 9 6 53
ch1, 5 M 38 21 13 26 13 21 26
‘H I 10 3 18 11 28 28 6 19 28
6‘M ” 20 0 - - - - - ~ *
3801 . 5 1 8 0 1 13 0 5 75
n 2 10 M 33 2M 2 6 M 25 8
I 20 3 16 6 31 31 6 17 25
Check M 36 3' 6 8 3 M 80
Hg01. 5 1 5 20 20 0 0 20 60
I 10 2 16 25 25 25 6 28 20
n 20 0 - — - - - _ _
6.5 HgClg, 5 1 10 0 30 30 0 31 M0
6 10 1 6 0 0 0 0 0 100
' 20 2 1M 21 50 21 0 32 7

 

 

 

 

 

 

 

 

 

 

-39...

 

 

 

 

 

 

 

 

Relation of Soil Reaction to the Effect of Mercurial Soil Treatments on Potato Scab
Soil ‘
Reac- 3011 No No N°° °f Scabby TUbers 8 of Surface 3
tion Treatment hills tubers Heavy Medium Light Trace area scabby clean tubers
Check 6 52 8 13 27 2 12 50
ch1. 5 2 1M 0 0 21 0 2 79
I 10 5 39 3M 36 26 3 37 3
pH I 20 0 - - - - - - -
6.6 38012. 5 3 27 15 33 26 7 23 19
I 10 0 - - - - - - -
I 20 0 - - - - - - -
Check 5 M1 5 10 17 0 8 68
ch1. 5 1 7 1M 1M 0 0 1M 71
' 10 5 53 23 23 36 9 26 9
ya I 20 5 51 26 26 2M 2 26 2M
6.7 ch12, 5 3 28 M 18 29 18 11 32
I 10 3 32 25 19 25 6 26 25
I 20 1 8 25 13 63 0 28 0
Check 7 58 5 10 5 5 7 7M
ch1, 5 M 36 8 20 22 11 1M 39
I 10 7 67 37 18 15 5 33 25
pH I 20 M 39 27 21 23 0 26 31
6.8 Hg012, 5 E 33 36 12 21 6 31 21
I 10 22 23 55 23 0 35 0
I 20 2 19 27 37 21 5 32 11
Check 5 37 8 22 19 1M 1M 38
ch1. 5 2 1M 1M 0 M3 1M 1M 29
I 10 M 26 62 19 M M M9 8
25 I 20 3 22 9 32 27 9 l9 23
6.9 Hg012. 5 ; 3 51 31 18 27 M 30 20
I 10 M 18 6 28 39 6 16 22
I 20 M 31 6 39 26 3 19 26
Check r18 150 7 13 29 9 12 M2
HgCl, 5 M 2 28 19 25 6 27 22
I 10 5 6 2M 26 39 0 29 11
PH ' 2O 8 66 35 33 17 5 36 11
7.0 ch12, 5 8 M5 22 33 27 0 28 18
I 10 M 16 6 13 13 6 9 63
I 20 6 27 M8 26 11 0 M3 7
Check 11 89 3 12 25 7 9 53
8gc1, 5 2 23 9 22 30. 9 16 30
I 10 0 - - - - - - -
ya I 20 5 51 2M 20 1M 0 2M M3
7.1 ch12, 5 1 7 1M 28 57 0 2M 0
I 10 1 5 0 M0 20 20 15 20
I 20 0 _ .. .. ._ .. .; ..

 

 

 

 

 

 

 

 

 

 

_ ho -

Relation of Soil Reaction to the Effect of Mercurial Soil Treatments on Potato Scab #

 

 

 

 

 

 

 

 

Soil
ReacJ Soil No No NO' of Scabby Tubers % of Surface %
tion Treatment hills tubers Heavy Medium Light Trace area scabby clean tubers
Check 8 67 2 5 21 8 5 66
H801. 5 5 33 6 20 3M 3 13 37
I 10 3 3 27 2M 18 6 28 27
pH I 20 8 72 29 M0 25 1 EM 8
7.2 ch12, 5 1 11 55 18 18 0 6 9
I 10 0 - - - - - - _
I 20 2 8 25 75 0 0 Mo 0
Check 8 63 11 17 33 10 17 28
H861. 5 3 33 33 3 18 6 3M 39
I 10 3 31 10 36 19 7 20 29
pH ' 20 O - - - - - - -
7-3 H8012. 5 8 69 23 55 2O 7 35 23
I 10 1 12 0 8 58 o 8 33
I 20 1 3 0 33 66 0 50 0
Check 1 3 O O O O O 100
ch1, 5 1 3 M0 60 0 0 0 M6
I 10 1 75 0 25 0 55 0
58 I 20 0 - - - - — - —
7.M ch12. 5 M 31 38 26 6 3 35 26
I 10 0 - - - - - - -
I 20 1 7 0 28 28 28 11 1M
Check 3 25 0 16’ 2M 7M 7 56
HgCl. 5 2 17 19 19 23 0 22 M
I 10 - - - - - - - -
23 I _ 20 2 18 33 33 33 0 37 O
7.5 Hg012, 5 1 8 0 25 25 0 11 50
I 10 _. _ _. .. .. - .. -
I 20
Check 3 36 1M 11 28 6 16 M2
ch1. 5 1 6 o 33 0 17 10 50
I 10 1 2 50 50 0 0 50 0
pH I 20 M 16 13 31 19 13 20 25
7.6 Hg012, 5 1 6 0 17 17 0 7 67
I 10 M 32 19 3M 25 13 26 9
I 20
Check 1 8 0 0 25 0 75 3
H801. 5 - - - - - - - -
I 10 - - — - - - - —
58 I 20 1 9 11 0 22 22 10 MM
7-7 H8012. 5 - - - - - - - -
I 10 1 12 0 0 8 0 1 92
I 20

 

 

 

 

 

 

 

 

 

 

- M1 -

Relation of Soil Reaction to the Effect of Mercurial Soil Treatments on Potato Scab z

Soil
Reac-
tion

 

Soil

Treatment

N0
hills

No
tubers; Heavy

No. of Scabby Tubers

 

Medium

Light

Trace

% of Surface
area scabby

clean tubers

 

PH
.8

Check
11801 . 5
' 10
” 20
chj'e’ 5
' lO
' 20

NIHIN!

2O

5

ll

OIOIO'I

lO

0

27

5

MO

27

IOIOI

27

I-F'IKNI

l

H

85
68

18

 

Check
3501: 5
“ lO
" 2O
H8012. 5
' lO
" 2O

IIHI

 

8.0

Check
11801. 5
I 10
' 20
88012. 5
I 10
' 20

O

O

 

Check
H801. 5
' 10
' 20
88012. 5
' lO
' 2O

 

Check
3801. 5
' 10
' 20
88012. 5
' lO
' 20

 

 

Check
8° 5

10‘

" 20
88012. 5
" lO
" 2O

 

 

 

 

 

 

 

 

 

Relation of §9i1 Reaction to the Effect of Mercurial Soil Treatments on

-M2..

Potato Scab fl

 

 

 

Soil F-
Reac- Soil No N0 No“ Of Scabby Tubers % of Surface %
tion Treatment hills tubers Heavy Medium Light Trace area scabby clean tubers
Check 1 M 0 0 0 0 0 100
Heel. 5 - - - - - - - -
I 10 .. - .. .. .. .. .. ..
pH ' 20 - - - - - - - -
8.M 8.3012. 5 - - - - — - - -
I 10 1 8 25 50 13 0 3M 13
a 20 _ - _ - _ _ - _

 

 

 

 

 

 

 

 

 

 

-M3-

TKBLE VIII

The Influence of Soil ReactiQIOn the Effectiveness of Mercurials

as Soil Disinfection for Potato Scab Control

 

 

 

control HgCl HgCl HgCl HgCl2 Hg012 Hg012 Hg
45 lbs. 10 lbs. 20 lbs. 5 lbs. 10 lbs 20 lbs. av.#
3* Sc" H Sc H Sc H Sc H Sc H Sc H Sc H Sc
pH 6.0 0 1 6 0 0 0 0 1 21 2 20
6.1 0 0 0 0 0 1 10 0 0 10
6.2 3 M 1 18 1 30 0 2 23 2 13 M 3M 10 26
6.3 13 3 15 1 38 0 o 0 1 1M 5 19
6. g 6 M 21 3 19 0 1 5 M 25 3 17 15 20
6.5 M 1 20 2 28 0 1 31 1 0 2 32 7 2M
6.6 6 12 2 2 5 37 0 3 23 0 0 10 26
6.7 5 8 1 1M 5 26 E 26 3 11 g 26 1 28 18 23
6.8 7 7 M 1M 7 33 26 5 31 35 2 32 26 29
6.9 5 1M 2 1M M M9 3 19 3 30 M 16 M 19 20 26
7.0 18 12 M 27 5 29 8 36 8 28 M 9 6 M3 35 30
7.1 11 9 2 16 0 5 2M 1 2M 1 15 0 9 21
7.2 8 5 5 13 3 28 8 3M 1 M6 0 2 M0 19 29
7.3 8 17 3 M 3 20 0 8 35 1 8 1 50 16 31
7. 1 0 1 6 1 55 0 M 35 0 1 11 7 36
7.5 3 7 2 22 0 2 37 1 11 0 3 27 8 26
7.6 3 16 1 10 1 50 M 20 1 7 M 26 2 51 13 27
7.7 1 13 0 0 1 10 0 1 0 0 2 5
7.8 0 2 3 0 1 M 0 2 11 0 5 7
7.9 0 . 0 0 1 0 0 0 0 1 0
8.0 1 32 0 0 0 0 1 0 0 1 0
8.1 1 3 0 0 0 0 0 1 0 1 0
8.2 0 0 0 0 0 1 1M 0 1 1M
8.3 0 3 38 0 0 0 0 0 3 38
8. 1 0 0 0 0 0 1 3M 0 1 3M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

* Number of hills

*' 'fi of surface area of tubers scabbed

# [sighted average (based on the number of tubers involved)

mercury treatments.

of all

pH
6.0

to
6.M

UH
6.5
to
6.9

pH
7-5
to
7-9

Check
Calomel, 5
u ’ 10

Corrosive sublimate,
II "

Check

Calomel, 5
n ’ 10
ll ’ 20

Corrosive sublimate,
n u

I! If

Check
Calomel, 5
ll ’ 10
u , 20
Corrosive sublimate,
II H
II 1!

Che ck
Calomel, 5
ll ’ 20

Corrosive sublimate,
u u

Check
Calomel, 5
Corrosive sublimate,

S of surface area scabbed

D.) [-4 \J]
O O

10
2O

10
2O

10

- h

M -

           
 

l0

{5

10

15

squemqeelq
'env pueag

'd

A

{'7

.0

IO
U

‘H II9

uses up

efiuEJ

30

b

l

f

I

v
p,
d
m
o
[.43
m
H
|-'
In
(IQ
d
“'1
w
W
d-
33
('D
E.

”M”

'env

{cage 30

‘
d

35

{oxiuoo qeos oieiog so; siuuqoegutsrq 7703 se

sIerinOJefi go sseuenrioeggg eui no

6412308 1108 80 808281381

XI STE?

.RSHMRY
l. Twenty-four chemicals were tested as soil disinfectants for the

control of potato scab:

 

 

Chemical Greenhouse ‘ Field
Aluminum chloride 150, 500*

Borax 5. 15: 5O
Cerium oxalate 5, 15, 50, 500 5, 15, 50
Cobalt chloride 250

COpper sulphate 5, 15, 50, 250

COpperous oxide 5, 15, 50 5, 15, 50
Lead acetate 250

Lead sulphide 5, 15, 50, 150 5, 15, 50
Mercuric chloride 250 20
Mercuric oxide 5, 10, 2O 5, 10, 2O
Mercurous chloride 5, 10, 20, 50, 150 5, 10, 20
New Improved Ceresan 5, 15, 50, 150

Nickel cyanide 5, 15, 50, 150, 500 5, 15, 50
Kickel nitrate 250

Potassium permanganate 5, 15, 50, 150, 250, 500 5, 15, 50

Potassium dichromate 5, 15, 50, 150, 250 5, 15, 50
Sodium fluoride 5, 15, 50, 150, 250, 500 5, 15, 50
Zinc oxide 5, 15, 50
Zinc sulphate 250

Formicide 50, 325, 650

Gentian violet l, 10

Malachite green l, 10, 50, 150

Coal tar creosote l, 5, 20 (gallons)

Wood creosote 1’ 5. 20 (gallons)

* The figures Opposite the names of the chemicals indicate the
rates in pounds per acre at which the chemicals were employed.

- M6 _
2. None of the chemicals tested controlled potato scab at any of
the rates employed, except nickel cyanide at 500 pounds per acre in
the greenhouse, — a rate too high to be considered for practical control.
3. Mercurial soil treatment increased the scabbiness of the cr0p two
to three-fold.
M. Plots in a field which varied widely in soil reaction were treated
with calomel and corrosive sublimate at rates of 5, 10, and 20 pounds

per acre. The hills were harvested separately and a soil sample was

taken from around the tubers in each hill for pH determination. The
O - I ' O 0 fl ’ ‘ O O 0
results indicate that w1tn1n the pH range 01 b.0-8.M s01l reaction d1d

I"

not appreciably afzect the tendency of mercurials to cause an increased
amount of scabbing.

5. The literature on control measures for potato scab is reviewed and

discussed.

-147-

Literature Cited

Adams, J. F. An actinomycete, the cause of soil rot or pox

in sweet potatoes. PhytOpath. 19: 179-190. 1929.

Arthur, J. C. and K. Golden. Diseases of the sugar beet root.

Ind. Agr. EXp. Sta. Bul. 39. 1392. (Cited by Lutma

D

c - 1
and Cunningham, 1914).

0

Beckwith, 3. H. Report of the assistant horticulturist.

N. Y. Agr. Exn. Sta. Rpt. 6: 307-315. 1333.

Beijerinck,1!. W. Sur la production de quionone par 1e Streptothrix

 

chromotena et la biolocie de ce microbe.

 

Archives Héerlannaises d. Sc. exactes et naturelles.

La Haye. 1900. Ser. 3. T 3: 327-330. Abst. in Central.

fur Baht. Abt. 2, 6: 661. 1900.

Berkner, F. Die Ursachen des Kartoffelschorfes und Wege zu seiner

Bekfimnfung. Landw. Jahrb. 78: 295—3M2. 1933.

Die Wirkung einer physiologisch sauren bzw. alkalischen

 

Dungung auf Ertrag, Schorfbefall und Eisenfleckiakeit von
drei genetisch und Bkolorisch verschieden eingestellten

z. PflErnfihr Dun”. A, #5: 205—21~. 1a36.

‘C‘l
\

Kartoffelsorten.

Abst. in Rev. Appl. Eye. 17: 53, 1937.

Dry weather potato growing inliicnigan.

Bird, J. J.

Amer. Potato Journ. 8: 235-239. 1931.

Blodgett, F. H. and F. B. Howe. Factors influencing the occurrence

of potato scab in Hen York. Cornell Aar. Exp. Sta. Bul.

5g1. 193k.

and E. K. Conan. Relative effects of calcium and

 

acidity of the soil on the occurrence of potato scab.

Amer. Potato Jour. 12: 263-27u.

9.11.

.«el2.

’18.

-_¢20.

._ 11,3 _

Bolley, H. L. Prevention of potato scab.
H. D. Anr. Exp. Sta. Bul. 9. 1393.

Biology.

 

N. D. Agr. EXp. Sta. Bul. 19M: 36-50. 1926.

Boysen, H. Flatskurv -- Actinonyces-skurv —- 0g jordreaksjon.
Hoen iakttagelser fra Hvam forsksgard. Tidsskr. Horske
Landbruk 1932 ( 10 ). 6 pp. 1932.

Brann, J. W. and R. E. Vaughan. Potato scab.
Wis. Agr. EXp. Bul. 331. 1921.

. Organic mercury disinfectants

 

 

tested in potato disease control. Wis. Agr. Exp. Sta.
Bul. 905. 1929.

Bushnell, J. The tolerance of potatoes to soil reaction in Ohio.
Proc. 13th Ann. meet. Pot. Assoc. Amer. 1931: 99-93. 1932.

Chester, F. D. ZXperinents in the use of sulphur for scab of the
Irish potato. Del. Agr. Exp. Sta. Rpt. 10 (1898): 95-96.
1899.

Clark, C. F., W. P. Raleigh, and F. D. Stevenson. Breeding for
resistance to common scab in the potato. Amer. Potato
Journ. 13: 256—2 9. 1936.

Clark, J. F. 0n the toxic value of mercuric chloride and its
double salts. Journ. Phys. Chem. 5: 239-316. 1901.

J '

Cocchi, F. Ricerche sulla 'scabbia' della natate. 3011. R. St

[13
0

k
b.
0

Pat. Veg. n. s. 13: 79-139. 1933.

‘ U

Conn, H. J. A possiole function of Actinomycetes in soil.

n. Y. Agr. Exp. Sta. Tech. Bul. 92. 1916.

Conner, S. D. Irish potato scab ( Oospora scabies ) as affected

by fertilizers containing sulphates and chlorides.

22.
---23.
”929.
KP“
;;.25.
4/” 260
{/7
2" 27 o

(.0.

3 29.

Darling, 2., J. G. Leach, and F. A. Krantz.

Proc. Ind. Acad. Sci. 1913: 131-137. 1919.

Coons, G. H. Potato scab and type of soil.

Hich. Agr. rap. Sta. Quar. Bul. 3: 132-139. 1921.

Cunningham, H. S. The addition of mercury compounds

fertilizer mixture as a control for common
potato under Long Island conditions. Amer.

13: 100-103. 1936.

 

to the

scab of the

Potato Jour.

Daines, R. H. Antagonistic action of Trichoderma on Actinomyces

 

scabies and Rhizoctonia solani. Amer. Potato Jour.

 

14: 35-93. 1937.

Scab resistance in

potato seedlings. Phytopath. 25: 13-1h. 1935.

A study of scab resistance in the potato.

 

Dippenaar,

Duché, J,

Duff, G. H. and Welch, C. G.

Eddins, A. H.

Jour. Agr. Res. 59: 305-317. 1937.

Bruijn, H. L. G. Het schurftvraagstuk van mycologische zijde

~ .01 - 0 ‘W
beteken. Landoouwk. Tlgoscnr. Wagenlngen 47: 579,

8 pp. 1935. Abst. in Rev. Appl. Myc. 15:

B. J. Environmental and control studies of the common

scab disease of potatoes caused by Actinomyces scabies

 

T'azt.) Guss. Dept. Aer. Union South.Africa Sci. Bul.

136. 1933.

Les actinomyces du groupe albus.

EncyclopediaIEycologique, 6. Paul Lechevalier et

fils. Paris. 193M.

scab of potatoes. PhytOpath. 17: 297-319.

Sulphur as a control agent for common

1927.

Effect of inoculated sulphur, lime, and mercury

compounds on the yield of potatoes. Amer. Potato Jour.

11: 295-302. 1939.

f 32. Eichinger, Kartoffelschorf und Dungung. Teil I. Superphosphat

3-16. 1931. Teil II. Fortscher. der Landw.

—4
o.

7: 193-197. 1932. Teil III. Superphosph1at 9: 2.1933.
‘*~33. Fousek, A. Uber die Rolle der Streptothricheen im Boden. Mitt.
Landw. Lehrkranz K. K. Hochschile B0denku1t.Wien.
1: 217-2ue. 1912. Abst. in 330. Sta. Rec. 27: 620-621.
1912.
2/“' M. Frutchey, C. W. Studies on potato scab caused by Actinomyces

scabies. Xich. State Col. H. S. Thesis. 1932.

._135. and J. T. Nuncie. Soil treatments with mercur ri ls

 

for the control of potato scab. Mich. Agr. Exp. ta.

r‘ ." H‘l
(211941.. 311.10 16: 239-203. lruleTo

"

(336. Gardner, J. S. Some obser irations on the us e of sulphur to correct
scab in potato land in Kentucky. Proc. 10th. Ann. Meet.
. r- f \
Potato Assoc. Amer. 1923: 159-101. 1924.

4F’37. Gillespie, L. J. and L. A. Hurst. Hydrogen—ion concentration
measurements of soils of two types: Caribou loam and

Washburn 10am. Soil Sci. 9: 313-319. 1917.

 

9 33. The growth of the potato scab organism at various
hydrogen-ion concentrations as related to the comparative
freedom of acid soils from the potato scab. PhytOpath.
8: 257-269. 1913.

g339. and L. A. Hurst. Hydrogen—ion concentration - soil

 

type - common potato scab. Soil Sci. 6: 219— 230. 1913.

o1

‘1‘\

3; MO. Geise, F. W. EXperiments with inoculated sulphur. Preliminary
report. Va. Truck Exp. Sta. Bul. 92: 255-263. 1923.
‘21U1. van der Goot, P. Overzicht der voornaamste Ziekten van het

Aardaopelgewas 0p Java. Inst. voor Plantenziekten.

\ .
Bul. 13. 1924. Rev. Appl. Lyc. 9:1136-137 1923.

51.

52.

53-

_ 51 -

Goss, R. W. A survey of potato scab and Fusarium wilt in western
’ '1 ' ' r- ‘
hesraska. PhytOpatn. 2+: 517-527. 1934.

Goss, R. W. The effect of irrigated crop rotations upon potato

scab. Amer. Potato Jour. 13: 91—96. 1936.

.- ~ /

Gram, E. Plantesygdomme i Danmark 1930. Tidsskr. f.
\
Planteavl. 37: 156-503. 1931.

Graham, J. C. Some emperiments with sulph r as a control for

potato scab. Proc. 10th. Ann.I{eet. Potato Assoc. Amer.

\J

-3) : 161-165. 1929.

r

(19

p

Hastings, S. H. Irrigated cr0p rotations in western Nebraska,
1912-1939. U. S. D. A. Tech. Bul. 512. 1936.
Halsted, B. D. Field eroeriments with potatoes.
N. J. Agr. Exp. Sta. Bul. 112. 1395.

Field experiments with potatoes in 1396.

 

N. J. Aar. Exp. Sta. Bul. 120. 1897.

Experiments with potatoes.

 

n. J. Agr. Exp. Sta. Rpt. 13 (1397): 276-239. 1393.

Experiments with potatoes.

 

N. J. Agr. Exp. Sta. Rpt. 19 (1393): 299-303. 1399.

Potato experiments in 1900.

 

N. J. Agr. EXp. Sta. Rpt. 21 (1900): h13-his. 1901.
Hardenburg, E. V. Potato rotations and fertilizer program.
Amer. Potato Jour. 8: 192-195. 1931.
Hester, J. B. The influence of lime upon soil reaction and yield
of Irish potatoes. Trans. Peninsula Hort. Soc.

29: 95-51. 1939.

and B. L. Carolus. lree years' results with the

 

use of copper, manganese, and zinc sulphate in fertilizer

/

,-— 57 .

mixtures for potatoes. Amer. Potato Jour. 14: 37-39.

1937-

ziltner, L. and K. Stramer. Stucien fiber die Eakterien-flora des

Ackerbodens. Arb. K. Gesundheitsamte. Biol. Abt.

3: 993-495. 1903.

. o I 1 c o o A o
Rflnne, E. and G. Cnelard. Hat c1e Dflngung e1nen Einiluss auf die

r

Schorfbildung bei Lartoffeln Die Phoschorsaure.

f \

M: 161—107.
Huisman, T. J. De gewone Schurft van de Aardappelknol. Tijdschr.
39: 173-183. 1933.

over Plantenziekten.

Janchen, E. Der Kartoffelschorf. Oesterr. Zeitschr. fur
Kartoffelbau 1: nos. 3-U. 1921.

Jensen, H. L. Actinomyces in Danish soils. Soil Sci. 30: 59-77.
1930.

Contributions to our knowledge of the Actinomycetales.

 

Proc. Linn. Soc. 2. S. Wales. 56: 79-93, 395—370. 1931.

Johnson, L. R. Trials of mercuric chloride for the prevention of

'potato sickness. Ann. Appl. Biol. 23: 155-165. 1936.

Jones, L. R. and H. H. McKinney. The influence of soil temperature

on potato scab. Phytopath. 9: 301-302. 1919.

, and H. Fellows. The influence of soil

 

 

temperature on potato scab.

Wis. Aer. Exp. Sta. Res. Bul. 53. 1922.

Kinney, L. F. Potato scab. R. I. Exn. Sta. Bul. 14. 1391.

Krainsk~, A. Die Actinomyceten und ihre Bedeutung in der Katur.

Centralbl. f. Bakt. Abt. II, 91: 599-633. 1919.

Lamson, H. H. Notes on potato and apple diseases.

Exp. Sta. Bul. 65. 1399.

I
‘ J1
‘aN
I

,a.67. Lint, R. C. Report of potato scab eXperinents.
r. J. Agr. Exp. Sta. Rpt. 35 (1915): 977-933, 1916;
36 (1916): 375—331, 1917; 37 (1917): 613—625, 1913.
E 3. Lipnan, J. G., E. C. McLean, and H. C. Lint. Sulphur oxidation
in soils and its effect on the availability of mineral
phosphates. Soil Sci. 2: 999-533. 1916.
3169. London. Encyclonedia of agricultur . 1325. (Cited by Lutman
and Cunningham, 1919).
._ 70. Lutman, B. F. and G. C. Cunningham. Potato scab.

Vt. Agr. EXp. Sta. Bul. 139. 1919.

--71. Potato scab on new land. PhytOpath. 13: 291-299. 1923.

 

~~ 72. , R. J. Livingston, and A. M. Schmidt. -Soi1 Actinomyces

 

and potato scab.
Vt. Agr. Exp. Sta. Bul. 901. 1936.

73. Yanns, T. F. and J. F. Adams. An actinomycete, the cause of soil

\491

rot or pox in sweet potatoes. PhytOpath. 19: 179-190.
1929.
79. IdaeLeod, D. J. and J. L. Howatt. Soil treatment in the control of
certain soil-borne diseases of potatoes. Amer. Potato
Jour. 11: 60-61. 1939.
a, 75. Iiadfillan, H. G. Potato seed treatments in western states.
Abst. in PhytOpath. 12: 39. 1922.

f 76. and O. A. Plunkett. Plant diseases observed in

 

southern California in 1936. Plant Dis. Rpter. 21: 73-79.
Har., 1937.
77. Nader, E. O. and F. M. Blodgett. Potato Spraying and potato scab.

Amer. Potato Jour. 12: 137-192. 19}

\fl

|

x ‘31
CQ
H

(Q
09.

(Q
\o

.+—— '-

V. The relation of sulfur to soil acidity and the

control of potato scab. Soil Sci. 9: 39 3- 903. 1920.

J J J

A comparison of inoculated and uninoculated sulfur

 

for the control of potato scab. Soil Sci. 11: 75- 85.
1921.

Influence of soil moisture and acidity on the

 

develOpment of potato scab. Soil Sci. 16: 69-73. 1923.

The inf uence of source of nitrogen on the prevalence

 

r. J. Agr. Exp. Sta. Rpt. 93 (1922): 596- 599. 1923.

Influence of fertilizer ingredients on t1 e dew elop-

 

ment of scab.
N. J. Agr. Exp. Sta. Rpt. 94 (1923). 353-359. 1929.

Potato scab control. Proc. 10th. Ann. Heet. Potato

 

Assoc. Amer. 1923: 127-139. 1929.

Control of soil-borne scab.

 

N. J. Aer. EXp. Sta. Rpt.5m(13) 5.59. 1929.

KN
\

Soil reaction and the potato crOp. Hints to Potato

 

Growers. ll: Ho.7, 1930.

Soil reaction and the potato crop. Amer. Potato

 

Jour. 8: 59-69. 1931.

The use of disinfectants in fertilizers for the

 

control of potato scab and Pnizoctonia. Asst. in
. . l
PnytOpatn. 21: 104. 1931.

Fer ilizer-mer y studies. N. J. Agr. Exp. Sta.

 

Fertilizer-mercury studies. n. J. Aer. Exp. Sta.

 

9 90.

3.91.

92.

93-

I
x 71
\11
I

ficCallan, S. E. A. and F. Wilcoxon. Fungicidal action and the
periodi system of the elements. Contrib. Boyce Thomp.
Inst. 6: 979-500. 1933.

McCormick, R. B. The associative action of some species of
Actinomyces. Cornell Univ. Ph. D. Thesis. 1935.

Meyers, P. G. Landbouwk. Tidschr. M7: 633. (Cited by Wieringa
and Wiebols. 1936).

IIillard, W..A. Common scab of potatoes.
Univ. Leeds and Yorkshire Coun. for Agr. Educ. Bul. 118.

1921. Also in Ann. Appl. Biol. 9: 156-169. 1922.

. Common scab of potatoes.

 

Part II. Ann. Appl. Biol. 10: 70—88. 1923.

n ‘ O A
and S. A. Burr. A study 01 24 stra1ns 01 Actinomyces

 

 

and their relation to types of common potato scab. Ann.
Appl. 3101. 13: so-644. 1926.

and C. B. Taylor. Antagonism of microorganisms

 

as the controlling factor in inhibition of scab by green-
manuring. Ann. Aspl. Biol. 19: 202-216. 1927.

and F. Beeley. fiangel scab - its cause and histogeny.

 

Ann. Appl. Biol. 19: 296-311. 1927.

horse, 9. J. and M. Shapovalov. Seed and soil disinfectants for
the Rhizoctonia disease of potatoes. Abst. in Phytopath.
6: 113-119. 1916.

Orton, W. A. and E. C. Field. Sulphur injury to potato tubers.
Abst. in Sci. n.s. 31 (303): 796. 1910.

Environmental influences on the pathogenicity of

 

Solanum tuberosum. Jour. Wash. Acad. Sci. 3: 180-190.

 

1913.

102.

;'103-

A 105.

r~I 107.

103.

109.

~‘llO.

111.

_ s6 _

Palm, B. T. Notiser om sydsvenska actinomycoser. Bot. Notiser
7‘ 1‘1 "’ ‘
1934: L 9—h36. 1934.

Pierstorff, A. L. Potato scab control demonstrations in 1933.

. . \ r—f' \
Proc. thn Ann. Meet. nio. Ve”. Grow. Assoc. 174-lho. 19 4.
/ C) J -

Poole, R. F. Some results obtained in the i-vestigation of pox

disease control of sweet potatoes. N. J. Agr. Eat. Sta.

Rpt. nu (1923 : 39h-323. 192M.

Pratt. O. A. Exoeriments with clean seed potatoes on new land in

southern Idaho. Jour. Agr. Res. 6: 573-575. 1916.

Ramirez, 3. Plagas de la agriculture en el distrito federal.

La Revista Agricola (Hexico). 5: 6b2-663. 1921. Abst. in

Rev. Anpl. Nye. l: 375. 1922.

Schorf und Stippigkeit bei Kartoffeln. Deutsche Landw.

Rang.

59: 60h. 1932. Abst. in Res. Appl. Myc. 12: 239.

Presse

1933-
d.

A a I u 0 I o o ‘
Rina, J. Coranne prostredky prot1 obecune strupovistostl Bramboru.

Ochrana Rostlin 6: 73-30. 1326. Abst. in Rev. A pl.

\

6: 246—2u7. 1927.

3.’
{£er 0

Rosa, J. T. Effect of sulphur and acid fertilizers on scab in

California. Proc. 10th. Ann. Meet. Potato Assoc. Amer.

157-138.

On the preparation of mercuric chloride solutions.

 

Proc. 11th. Ann. Heet. Potato Assoc. Amer. 113-115. 1925.

Sanford, G. B. The relation of soil moisture to the develonment

PlvtOpath. 13: 231—236. 1923.

of common scab of potato.

6

Some factors inzlu ncing the develonment of potato

 

scab. Abst. in PhytOpath. 1U: 53. 192M.

"“"*ll2.

--116.

.1

ii
I

117.

32113.

-57...

Sanford, G. B. The relation of some soil factors to the develOp-

ment of common scab of potatoes. Proc. 12th. Ann. Meet.

Potato Assoc. Amer. 113-120. 1926.

Some factors affecting the pathogenicity of

 

. q o - - -—V. r’
Actinomyces scabies. PhytOpatn. 16: 525-ha7. 1920.

 

The limitations of treatment for potato tubers

 

against scab and Rhizoctonia. Amer. Potato Jour. 8: 11-13.

1931.

On treating seed potatoes for control of common

 

scab. Sci. gr. 13: 36M—373. 1933.

Some soil microbiological aspects of plant patholozy.

 

Sci. Agr. 13: 633-6h1. 1933.

. - r v a - o ‘:
Scnacnt, H. Lartoffeloflanze und deren hrananeitern. 1854.

Schreiner, O. and B. E. Brown. Soil treatment for potato scab

control. Proc. 10th. Ann. meet. Potato Assoc. Amer.

139-136. 192M.
Shapovalov, M. Is the common potato scab controllable by mere

PhytOpath. 9: M22-u2u. 1919.

rotation of crOps?

Schlumberger, O. Versuche zur Bekfimpfung des Kartoffelschorfes.

Mitt. Deutsche Landw. Gesellsch. M2z200, 1927; h3:33,

1928; nu 11, 1929: u5z75. 1930: h6:229. 1931: M7=55-.7.

1932: h8:195-197, 1933: 50:129-130. 1935:

Sherbakoff, C. D. Potato scab and sulfur disinfection. Cornell

Agr. EXp. Sta. Bul. 350: 707-7u3. 191k.

The after effects of sulfur treatment on soil.

 

PhytOpath. 5: 219—222. 1915.

Sibilia, C. EXperienze di lotta contro la scabbia delle patate.

3011. R. Staz. Pat. Veg. n.s. 12: 298-305. 1932.

Vla12u.

_/ 4‘; 1C3 '
,«V/

63130.
“f.

131.

~-132.

van der Slikke, C. M. Verslag van Rijkstvinbouwproefvelden
over grondontsmetting tegen de Rhizoctoniaziehte en de
schurft on Aardapnelen. Tidjdschr. over Plantenziekten
1:1: 65—73. 1935.

Smith, 0. Effect of soil reaction on the growth of the potato.

Amer. Fbt. Jour. 10: 118-121. 1933.

Snow, L. Flora of windblown soils. Soil Sci. ho: 181-190.

1935:

Snyder, E. F. Methods for determining the hydrogen—ion concentra-

1935-

Der Einfluss von.Bodenart, Bodenreaktion und

tion of soils. U. S. D..A. Circular 56.

Snennermann, F.
angun; auf den Kartoffelschorf. Pflanzenbau, Pflanzen-

schutz u. Pflanzenzucht. 10: ESL-270. 1934.

Stone, G. E. Influence of various potash salts on potato scab.

1007.

J

L)

Agr. Exp. Sta. Rpt. 20 ( 1907 ): 133—135.

Sturgis, W. C. Experiments on the prevention of potato scab.

Conn. Agr. BXp. Sta. Rpt. 18: 113—139. 1296; 19: 166—173,

1897: 20: 296-266, 1898.

Taft, L. R. Potato scab. Mich. Agr. Exp. Sta. Bul. 57: 23-25.

Taubenhaus, J. J. Pox, or pit (soil rot) of the sweet potato.

Jour. Agr. Res. 13: 437-H50. 1918.

Studies on potato—scab control. Abst. in PhytOpath.

 

2k: 836. 1934. .

Taylor, C. F. Potato scab and Rhizoctonia and their control.

Amer. Potato Jour. 10: 66—67. 1933.

Field eXperiments on potato-scab control in

 

western New York. Amer. Potato Jour. 11: MO-ME. 193M.

and F. M. Blodgett. Further field ezperiments on

 

potato-scab control in western New York. Amer. Potato

Jour. 13: 1M5-13o. 1936.

:fl37. Taylor, C. F. Separation of Actinomyces isolates obtained from

scabbed potatoes and from soil. Abst. in PhytOpath.
27: 191. 1937.

'.138. Thomas, J. B. Growth of Actinomyces macilatus (Hillard) in

.x'

 

various solutions. Hededeelinqen van het
Phytopath. Lab. Willie Commelin Scholten. Baarn.
13: u7_57. 1939.
£139. Tilford, P. E. Potato scab and Rhizoctonia and their control.
Amer. Potato Jou . 10: 68-69. 1933.
190. Vandecaveye, S. C., G. M. Horner, and C. M. Keaton. Unoroductive-
ness of certain orchard soils as related to lead arsenate
Spray accumulations. Soil Sci. M2: 203-213. 1936.
‘\~lul. Voelkel, H. and Klemm. Die hauplsachlichsten starken Schfiden an
Hackffichten im Jahre 1932. Nachrichtenbl. Deutsch.

Pflanzenschutzdienst 12: 101-103. 1932.

 

xplhg, Waksman, S. A. Bacterial numbers in soils at different depths and
in different seasons of the year. Soil Sci. 1: 99-135. 1
1916. !
-ilh}. and R. E. Curtis. The occurrence of Actinomycetes

in the soil. Soil Sci. 6: 309-319. 1918.

I INN. The influence of soil reaction upon the growth of

 

Actinomyces causing potato scab. Soil Sci. 19: 61-79.

 

1195. and R. J. Dubois. Sur la nature des organismes que
.’ ,
decomposent la cellulose dans 1es terres arables.

C. R. Acad. Sc. Paris 185: 1226-1228. 1927.

.- \ . . . - o n -
avg 146. Wedgwortn, H. H. Investigation on the relation 01 sulphur to

- 60 -

the Actinomyces scab of potato. Rich. State Col.
3:. s. Thesis. 192M.
“”1M7. Vessels, P. H. Soil acidity studies with potatoes, cauliflower,

and other vegetables on Long Island. Cornell Agr. Exp.

Sta. Bul. 536. 1932.

\

'148. Weindling, R. Trichoderma lirnorum as a parasite of other soil

 

. - \ -.
fungi. PhytOpatn. 22: S3 -845. 1932.

r 199. Studies on a lethal principal effective in the

 

parasitic action of Trichoderma lifnorum on Rhizoctonia

.—

 

solani and other soil fungi. PhytOpath. 29: 1153—1179.
1939.

‘r-l50. and O. H. Emerson. The isolation of a toxic

 

substance from the culture filtrate of Trichoderma.

PhytOpath. 26: 1068-1070. 1936.

\‘ .'~.§

.1 l. Weiss, F. and R. B. Harvey. Catalase, hydrogen-ion conCentration

\J1

and growth in the potato wart disease. Jour. Agr. Res.
31: 589-592. 1921.
.1 152. Wheeler, E. J. and H. C. Moore. Potato seed treatment tests.
Mich. Agr. Exp. Sta. Bul. 296. 1933.
g 153. Wheeler, H. J. and B. L. Hartwell. Observations on the effects
of certain fertilizers in promoting the develOpment of

potato scab. R. I. sap. Sta. Bul. 26. 1393.

.1115u. , and G. E. Adams. On the use of flowers of

 

sulfur and sulfate of ammonia as preventives of potato

scab in contaminated soils. R. 1. Air. 31;. Sta. Rpt.

x.

;;,-155. , B. L. Hartwell and H. L. C. Moore. Upon the

 

after effects of sulfur when applied to soils for the

”/156 White, R.

2157. Wiant, J.

.p

Wieringa,

_ 61 _

purpose of preventing potato scab. R. I. Agr. Exp. Sta.

189

.1

Rpt. 12: 163-167. 9.

P. Potato experiments for the control of Rhizoetonia,

scab and blackleg, 1922 to 1927. Kansas Agr. Exp. Sta.

. \
Teen. Bul . 24 .
S. The Rhizoetonia damping-off of conifers, and its

control by chemical treatment of the soil. Cornell Agr.

(‘1
EXT-'3. Sta. }'-:emo (.1 o 192' O

K. T. en G. L. W. Wiebols. De Aardappelschurft en de
Heterolyse der Sclurftparasiet. Tijdschrift over

P1ante.ziekten

,5159. Wilcoxon, E. and S. E. A. McCallan. The funqicidal action of
N sulphur II. Contrib. Boyce Thomp. Inst. 3: 13-38. 1931.
5:160. Williams, R. C. and H. C. Young. Chemistry of the toxic factor of
sulphur. Abst. in Phytopath. 19: 8M. 1929.
,r 161. Hingerberg, F. Studien fiber den gewbhnlichen Kartoffelschorf
und seine Erreger. Kfihn- Arehiv 33: 259-295. 1932.
~__162. Wollenweber, H. W. Der Kartoffelsehorf. Arb. d. Forschungsinst.

fur Kartoffelbau 2: 1-102. 20.

19

 

 

1‘ L I - III. 9 I I ‘A‘II' ' ‘0
' I‘ i ..
‘5 ' Ix 'Ql‘f' I ' In ‘Ilo ." I
l' . n. .
“if: Ir JIJZ v .0 I 0 l I
a w 'A'
.l t

as. . I
.. K a.

 

"I11111171111111155