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CLASSIFICATION CONFIDENTIAL CDNf1Utl1IIAL
CENTRAL INTELLIGENCE AGENCY REPORT
INFORMATION FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS CD NO.
COUNTRY USSR
SUBJECT Economic; Scientific - Biology, plant
diseases
HOW
PUBLISHED Bimonthly periodical
WHERE
PUBLISHED Moscow
DATE
PUBLISHED Mar - Apr 1949
DATE OF
INFORMATION 1949
DATE DIST. /6 M 1951
NO. OF PAGES 21
SUPPLEMENT TO
REPORT NO.
TNII DOCUMENT CONTAINS NUOINAnor ?rnCI1M THE NATIONAL 011,29:1
M
If rfo?
o I"% TI.C.. f I ENO HI. a ~riroio. Tin TIUITSININIION 02 THE IIIC.LUTION UNAUTH $11101 NT TLAW. 1 NVNODYCTION Or TNI{ r0 ^ II -IION ISITf o.
THIS IS UNEVALUATED INFORMATION
Agrobiologiya, No 2, 1949, pp 123-140
NEW USSR DATA ON SUGAR-BEET-OOT DISEASE, / IP ROT7
D. L. Tverskoy, Cand Agr Sci
All-Union Sci Res Inst of Beet Culture
ffables and figures referred to are appended
In some of the rayons of the old beet-growing zone (Chernigov and Sumy
oblasts and the rayons of Kiev, Poltava, and Kursk oblasts which border on
them) the sugar-beet crop; each year suffers great damage from root disease.
In certain years acute infection by root disease is nearly universal. Ob-
viously the field management measures for control of root disease were not
quite effective and therefore it was urgent that root disease, first of all
its ecology, be studied in great detail.
In our investigations in 1938, new facts became evident quite promptly
which indicated the possibility of infection not only of weakened bitt::A]:so
strongly developed seedlings. One of the most instructive cases was reported
in 1939 at the Chernigov station by phytopathologist M. K. Fomyuk. The affected sugar-beet seedlings were found in soil having 60-80% of total mois-
ture-holding capacity, at atmospheric temperatures of 21-27%, in other words
in conditions relatively favorable for plants, which was confirmed by the
heavy weight of the seedlings. Although we did not understand this =act at
the time, we were prompted to prolong the study of root disease so that we
might explain it later.
As a first step, we considered it necessary to determine the causal
agents of the disease and to determine the role of each of them in their
contact with normally developing seedlings. -
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Causal Agents of Root Disease and Their Propagation
The first analyses of diseased seedlings taken directly from sugar-beet
plantings at the "Sukhanovo" Sovkhoz in Moscow Oblast indicated that a series
of microorganisms are found in diseased seedlings and that the fungus Pythium
de Baryanum Hesse is particularly widespread. Since this fungus was found in
nearly every diseased seedling, there was no doubt that it was responsible
for the development of the disease (Tverskoy and Zhukova, 1948).
It should be mentioned that in the USSR, P. de Baryanum Hesse was reported
in sugar beets only once before, in 1907, by the phytopathologist Trzhebinskiy.
It is possible that even earlier, in 1890, this fungus was encountered by Karl-
son, which is confirmed by descriptions and sketches. However, up to very re-
cent times, there were no rerorts of this fungus being found in the analysis
of diseased seedling'. Jn the contrary, some investigators explicitly reported
finding in diseased seedlings such fungi as Fusarium, Phoma betae, Penicillium,
and others, while the subject fungus was nut detected.
Since we constantly found P. de Baryanum in diseased sugar-beet seedlings
in Moscow Oblast, it was decided to establish its propagation in the sugar beets
of other beet-growing regions. In 1947, soil samples were taken from Voronezh,
Kursk, Kiev, and Moscow oblasts and from Krasnodar Kray. The samples were taken
at a depth of not more than 10 cm under sugar beets, wheat, and grass (clover
and lucerne). In each soil sample were planted sugar-beet-seed clusters which
had been treated with preparation 1 of the Scientific Institute of Fertilizers
and Insectofungicides (NIUFI-1) and carefully washed in running water. To
check the appearance of the sugar beets, they were subsequently gathered and
analyzed as far as growth on nutrient media is concerned. In all cases the
'moisture of the soil was maintained at 70% of total moisture-holding capacity.
In the results of these investigations, approximately the same microorgan-
isms were found as in the previous analyses of diseased seedlings from sugar-
beet crops of Moscow Oblast (the analyses'of diseased seedlings were made by
Aspirant K. P. Zhukova and B. S. Navsuts, junior scientific coworker of the
laboratory). One of the most widespread causal agents was here again found to
be P. de Baryanum. The highest percentage of infected plants and the plants
most strongly infected by fungi were found in the soil samples taken from Kursk
Oblast (in particular from the Deryuginsk Beet Sovkhoz) and-those least infected
among the samples taken from the Voronezh Experiment Station. At the same time,
fungi of the species Fusarium were found in large amounts in the diseased seed-
lings, but they were nearly always accompanied by fungi of the species Pythium.
In connection with this, it can be surmised that the development of the Fusarium
fungi is closely connected with the previous infection by other relatively more
aggressive fungi or follows the weakening of the seedlings under the influence
of unfavorable soil conditions.
Other fungi, Alternaria, Verticillium, Rhizoctonia, etc., were also found,
but in smaller amounts. The Ph. betae are not included, as their presence in
the diseased seedlings in our investigations can be attributed rather to incom-
plete disinfection of the seed clusters than to their presence in the soil. In
general, the degree of propagation of the basic causal agents of root disease in
the infected sugar-beet seedlings from various previous crops for an average of
all the. tested samples is as shown in Table 1.
In 1948, the investigation of the infestation of the soil was considerably
expanded. Thirty-five new soil samples were taken from Kharkov, Vinnitsa, Cherni-
gov, Kursk, Voronezh, Penza, and Moscow oblasts, and also from Alma-Ata Oblast,
Kazakh SSR, and Tashkent Oblast, Uzbek SSR. A somewhat different method was em-
ployed for examining the soil and diseased seedlings, primarily with the aim of
checking a larger field of moisture-loving fungi. As is seen in Table 2, the
mycological analysis of the diseased seedlings in this case indicates that one
of the basic causal agents of root disease in nearly all the soil samples
was found to be P.. de Baaryanum Hesse. Besides this, a completely new causal
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CogIDEPAI.
agent, Aphanomyces cochlioides Drechs, was found in the course of this in-
vestigaticn. As far as known, this fungus up to now had not been reported
in the beet-growing regions, with the exception of the solitary mention in
1907 by the phytopathologist Trzhebinskiy, who stated that fungi were de-
tected on two occasions. As seen in Table 2, the Aphanomyces cochlioides
were found in nearly all the soils with the exception of the samples from
Central Asia and from Penza Oblast, and in quantities exceeding the P. de
Baryanum.
Among the other fungi found in the an%lysis of the diseased seedlings,
nearly all were representatives of the species Rizoctonia and Fusarium, and
were particularly widespread in the soils from Central Asia. In all, there
were fewer Alternaria fungi in the diseased seedlings, and fever Ph. betas,
the fundamental source of which appears to be not the soil but the infected
seed. The P. de Baryanum were most highly represented in the soils taken
from under grass, the A. cochlioides in the soil from under beets ar.d wheat,
the Rhi7nrtnnia from under lucerne, and the Fusarium from under lucerne,
clover, and wheat (see Table 3).
Thus our investigations indicated that in diseased sugar-beet seedlings
planted in the soils of the various beet-growing regions, there were found
a fairly large number of the same varieties of fungi, relatively stable in th ,r
ratios. However, Pythium de Baryanum, Aphanomyces cochlioides, and Fusarium
must be considered to be the most widespread among them. All the remaining
fungi were more weakly represented, with the exception of some obviously hav-
ing narrow local importance (for instance, the Rhizoctonia in Central Asia).
Parasitic Activity of the Cacaal Agents of Root Disease
It was interesting to trace in what measure the fungi which we had
found appeared to be actually aggressive on contact with normally develop-
ing sugar-beet seedlings. To cl,par up this problem, a few tests were set
up in containers holding soil which 1iad been artifically infested with each
of the investigated fungi. The required amount of fertilizer was introduced
into the soil and the moisture was maintained at 70% of total moisture-hold-
ing capacity. Table 4 shows the results of one of those tests which was set up
in a greenhouse during the summer; and under very favorable temperature condi-
tions. A,;
As shown in Table 4, the greatest infection of the seedlings for rela-
tively normal conditions of development iL produced by P. de Baryanum, A.
Cochlioides, R. Aderholdi, R. Solani, and Ph. betae. All the other fungi
c+ ;sed only very insignificant infection of the plants, Thus it is clari-
fied that the microorganisms which have a part in root disease are totally
distinct in their parasitic activity. Under certain soil conditions, some
of the parasitic fungi. are able >,o infect normally developed seedlings.
Obviously we could not leave out the important characteristic of activity
of the causal agents of root disease given by the degree of infection of the
seedlings in various phases of their development. Some of the conducted tests
indicated that in artificial infection by f. i. of seed clusters of. plants in
the phase of ..forging and of those in th'. s% or ,f irst.,pair,of .leaves,, P. de
Baryanum niincipslly. attacks the young. seedlings .in the : soil "aid:, plazits in the
forking phase. Ph. betae appears to be mo.3t aggressive in the infection of
seedlings in the phase of forking and that of the first pair of leaves, in
other words, in that period when the young plants are converting to self-sup-
ported nutrition and bleaching of the root begins. Fungi of the genus Rhizoc-
tonia develop almost equally on young seedlings and on more mature plants (two
or three pairs of leaves). However, the degree of destruction of the seedlings
decreases ds their development progresses. A. cochlioides, when there is suf-
ficient moisture in the soil, strongly attacks plants in the forking phase and
in later periods of development, so that we must report the highest degree of
development of thi' fungus on plants having three and even four pairs of perm-
anent leaves.
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From those investigations it follows that in natural conditions when
there are suitable causal agents in the soil, root disease can develop over
a rather long time. Such a case is rarely observed, mainly in years with
protracted high moisture content of the soil in the spring.
In the eaumerated tests, we were able also to trace the course of the
disease in some detail. It is necessary to cite the characteristic symp-
toms of the disease caused by the more aggressive parasites, since up to
now the diagnosis of root disease of sugar-beet seedlih,,s has not been
covered.
External Symptoms of Diseased Sugar-Beet Seedlings
A. cochlioides affects only the part of the plant above ground, from
the root neck upward. Therefore, it is distributed on the petiole and
cotyledon. At the onset of the disease, the infected tissue has a character-
istic watery gray-green color. Later, the infected part turns brown, becomes
thinner, and finally is converted into a dark-brown of black fiber. time to
the infection, in the basic cortical parts of the plant, the leaflets remain
turgescent and dark green for a long time. P. de Baryanum in contrast tc the
preceding fungus affects the underground portions of the plant and rarely ap-
pears above the soil. Only on very young plants is the disease able to go so
far as to take in the whole seedling. In the beginning, the disease is charac-
terized by the appearance of a shiny, a; if watery, light-brown rot, which in
time withers and turns dark brown, and almost black,
The development of the disee'i starts in the soil and evidently at a
very early stage in the development of the plant, which is why many plants
do not come above to the surface. The diseased plants which do appear on
the surface show symptoms of withering and have ,ellov-green (lemon) colored
leaves. Ph. betae affects only the underground part of the plant, predomin-
ately at the place where the radicle and pediclL come out of the seed. In the
first stage of the disease, on the affected seedlings there appear small dark-
brown or black marks which are difficult to detect and which then spread, blend
together, and encircle the seedling. Later the infected part advances above
or below the initial locus of the disease, darkens, and assumes the carbon-like
color of the ensuing dry rot. At high temperatures, the infected plants wither
as if from a lack of water. R. Aderholdi develops on the underground part of
the plant in the form of reddish-brown lesions, some of which go so far as to
completely encircle the root. Badly diseased plants turn yellow and wither.
R. solani, induces relatively less intensive lesions, with a golden brown
color on the underground part of the plant. It rarely kills the plant. Fusarium
infects mostly the small radicles and the lower part of the main root, developing
a dry rot with a dark-brown or yell:'w-brown color.
Effect of Temperature and Moisture Content on the Development of the Causal Agents
of Root Disease in the Soil
It is very important to clarify to what degree the development of the sub-
ject fungi is connected with the moisture content and temperature of the soil.
Tests were set up in plant containers with artificially infested soil the mois-
ture content of which was maintained at 40, 60, and F'% of total moisture-hold-
ing capacity. To prevent dustiness;?the soil was first mixed with uncontaminated
calcined sand in the proportion of one part of sand to three parts of soil. The
tests were conducted in a greenhouse during the summer at a temperature most fa-
vorable for growth of the seedlings. The number of dead plants was checked each
day. On the thirtieth day, when all the sugar-beet seedlings had developed their
first pair of leaves, a check was made, the results of which are recorded in Ta-
ble 5. As the table shows, the fungi which we tested,. with the exception of
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P. de Baryanum and A. cochlioides, infected the greatest numbe- of seedlings
in the soil with 40% moisture content, Under these conditions the seedling;
fell prey not only to the more aggressive fungi, but also to the less active
microorganisms such as B, cinerea, Fusarium, and A. tenuis.
Reduction of the amount of moisture in the soil evidently weakens the
plants and they become vulnerable to the attacks of even the lees active fungi.
From this we can conclude that where the seedlings have considerably deterio-
rated almost to the point of destruction, it is possible for them to be infested
by the very harmless saprophytic microorganisms.
With increased moisture in the soil, the parasitic activity of subject
fungi drops and the aggressiveness of P. de Baryanum and A. cochlioides is
increased. In our tests, due to the mixing of the soil with sand in contain-
ers and the resulting high moisture content, the physical conditions were com-
pletely normal. Consequently, the infection of the seedlings in this series
of containers uiust be considered as highly representative of the characteristics
of the vit the
of the parasitic u,. ti1~y Vl I faItsx.
It is clearly apparent from the test that root disease can infect both
the weak and strongly developed sugar-beet seedling'., However, chiefly the
semiparasitic and even saproph;,-tic fungi attack the weak plants, whereas only
some of the most aggressive parasitic fungi develop in the healthy seedlings.
From among the group of fungi chiefly attacking the weakened seedlings, the
most important in the beet-growing regions is Ph. betae. However, it does. not
cause serious damage to the sugar-beet crop. According to the available data
on Ph. betae, it is not preserved in soil when crop rotation is applied, and
the Sckluucuess of the infection of seedlings by Ph. betae is completely. dependent
on the degree it has it?ected the seed. Therefore, treatment of the seed by a
fungicide can serve as a very effective method of controlling this causal agent
of root disease. The measures for controlling the other less active causal
agents of root disease can basigally be reduced to maintaining normal moisture
content in the soil, which increases the strength of the plants and their re-
sistance to infection.
From the group of more active fungi infecting mostly the healthy seedlings,
P. de Baryanum and A. cochlioides are particularly widespread among sugar beets.
These fungi are permanent constituents of the soil and must be considered the
most dangerous causal agents of root disease. Since large-scale development of
the subject fungi is invariably connected with an increase in soil moisture,
the control of these fungi must involve the elimination of excess moisture, in
addition to other measures.
According to available data, one of the causal agents of root disease, P.
de Barjanum, despite its need for moisture, is pronouncedly aerobic and there-
fore develops mostly in the upper layers of the soil. We arranged a little test
with dried soil. The test was set up in wood.-n boxes of completely sterile soil,
artificially infested with P. de Baryanum. The moisture content of the soil was
maintained at around 60% of the maximum moisture-holding capacity. The soil in
one box was loosened every 2 days, starting when the seedlings emerged; in the
other, it was loosened only twice, once when sprouts emerged and the second time
5 days later. The test was concluded when the plants reached the completely
forked stage; then the data arranged in Table 6 were compiled.
In the box where the soil was repeatedly loosened, 44,1% of the plants were
found to be diseased, and 27.1% of them died. In the other box where the soil
was only loosened twice, 91.4% of the plants became infected, and 58.6% died.
Thus this short test indicated that for control of moisture-loving fungi such
as P. de Baryanum, repeated loosening of the soil was of value. The loosening
of the soil, in the first place, resulted in the drying out of the upper soil
layer, which destroyed the fungi in the mycelia stage when they are very sensi-
tive to lack of moisture. Secondly, the frequent aeration of the soil accel-
erated the development of the young plants, which shortened the period of great-
est susceptibility to infection.
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CONFIDE ' AL
The data arrived at here is conformed to closely by ?.nvestigations made
under field conditions, In tests conducted in 1936 at the Kiev (Mironovski;r)
Experiment Station of the All.-Union Scientific Research Institute of Beet Cul-
ture, it was found that when the soil was loosened up with a rye harrow 4 - 5
days after sowing, 24.2, of the seedlings were infected with root disease; when
it was hoed "bliid," using market plants, 3C,5% were infected; and when it. was
hoed after the seedlings emerged, 41,'(% were infected,
In other cases, hoeing at the time of the first marking of the rows re-
sulted in 22% diseased seedlings, hoeing on the second day after this produced
29% diseased seedlings, on the fifth day 31%, and on the tenth day 47%.
In these tests. there was evidenced not only the importance of loosening
the soil, but also of the time at which it is carried out. The greatest re-
duction in the development of root disease was found when the loosening was
done prior to the emergence of the seedlings or at the time when they broke
through the surface of thn soil. T'nes,-~ results do not differ from those pro-
ducedVin our box tests. Early loosening here produced the same results, the
drying out of the soil. As is known, the soil. Is moister during the period
of seed germination. Timely loosening dries the soil in the upper levels but
does not change the amount of moisture in the lower layers, which leads decid-
edly to reduction of the activity of the moisture-loving fungi. Loosening
of the soil. after rainfalls achieves the same results, and the sooner this
operation is done the more effective it is. Loosening of moist soil is very
valuable for other reasons as well. Timely loosening prevents crusting of
the soil.
Tests were also made on soils from "Sukhanove" Sovkhoz in Moscow Oblast,
"Pobeditel"' Kolkhoz in Rakttyansk Rayon, Kursk Oblast; and on soils from the
Nemarchansk State Selection Station, In these experiments, ins-easing the
moisture content of the soils up to 60-8% of the total moisture-holding ca-
pacity also always sharply increased the infection of seedlings by root dis-
ease. Analysis of the diseased seedlings invariably Indicated the presence
of the fungi P. de Baryanum end A. cochlioides,
We chec,ced the effect of temperature on the development of microorgan-
isms in the sugar beet seedlings in a polythermostat [incubato,7o Small
clay dishes of completely sterile soil were infested with subject fungi and
placed in chambeis with the temperature gradients shown in Tel-le 7. Dishes
with sterile noninfested soil were used as controls. In each dish were
planted 25 seed clusters of uniform size, each of which had been disinfected
in a solution of NIUIF-1 and carefully washed. In sterile water. The moisture
of the soil was mainiuuincd uL 701, of total mointurc-holding capacity. The
test was repeated four times for accuracy. In the course of the test, the
appearance of the seedlings and the number of dead plants were recorded. The
test was extended until all the seedlings emerged, which action took place
at different times in each chamber. The data collected in this test are ar-
ranged in Table 7,
First of all, the tested microorganisms reacted differently on the sugar-
beet seedlings, As in the previous tests, the first four fungi were found to
be the most aggressive. The others caused very mild disease in the seedlings,
even in conditions which were not favorable for the development of the, plants
(faint illumination), The effect of the temperature was shown to be such that
the P. de Baryanum and R. Aderholdi. infected the greatest number of seedlings
at from 21-25? C, the Ph, betae and R. solani at 210 C, the B. cinerea at 25?
C, and the A. tenuis at 32? C. The Fusarium fungi produced only a very low
percent of infection at all. temperatures,
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The infection of the seedlings at different temperatures very naturally
conforms to the intensity of growth of the fungi at the same temperatures o-n
nutrient mediums in a Petri dish.
Previously, we ha, succeeded in determining the dependence of A. cochlio-
ides on temperature. As compared to P. de Baryanum, it has a somewhat higher
optimal temperature of growth, in relation to which the maximum degree of in-
fection of seedlings by it dropped to 29.300 C.
The dependence of the growth and activity of fungi on temperature are
shown graphically in Figure 1, using as an example one of the most widespread
cau.al agents of rout disease, P. de Baryanum.
The number of seedlings remaining in the infested soil in comparison to
the sterile soil control is decreased gradually by the rise in temperature.
The number of seedlings killed were found to be; at 9? C - 23.0%, at 12.5? C -
50cult nr. at 210 C - 80..%, at 25? C - 100%, and at 320 C -
83.4,,
In Figure 1, it is obvious that the maximum number of killed seedlings
and the greatest growth of fungi were found at 250 C. At 32? C the growth of
the fungus is somewhat depressed, which is directly reflected in the reduction
of the number of killed seedlings. The relation we found, namely, that of a
direct connection between the energy of development of the fungi and the en-
ergy of growth of the plant, demonstra+:ss that fungi P. de Baryanum has a
clearly expressed parasitic nature whoa it affects sugar-beet seedlings. It
to be a well adapteli parasite developing best in conditions which are
uppcurG
the most favorable for the beets. This biological feature of the fungus makes
it very difficult to eliminate from sugar beets. Along with this, the intimate
connection of the fungus with the plants in the root contradicts the previous
hypothesis that healthy sugar-beet seedlings could not be infected by soil
fungi (Murav'yev, 1939). What must be taken into consideration is not only
the necessity to produce strongly developed seedlings but also the equally
important requirement of creating in the soil. conditions which inhibit the de-
velopment and accumulation of parasitic fungi.
At the same time, we studied the effect of temperature on the degree of
infection of seedlings in naturally infested soils with the same moisture con-
tent. Sterile uninfested soil was used as s control. The data derived in this
test concurs almost completely with the results of the previous test for P. de
Baryanum. As is seen in Table 8, the largest number of seedlings remaining
alive when all the seedlings had emerged was at the point when the temperature
was 12.6? C; the smallest number was at the point when the temperature was 20.7
and 26.50 C.
Damage Done by Root Disease
In our tests made in the conditions of Moscow Oblast corresponding to
severe infection of sugar-beet seedlings by root disease, the productivity
of the roots was reduced as much as 80% and the total yield of the harvest
as much as 40%. On tt,0 average, for the past 3 years the infection by root
disease reduced the sugar-beet yield around 30%. On the basis of the data
in our possession we can surmise that in regions where there is constant and
severe infection of sugar beets by root disease, the loss due to this disease
is arc?ind 25-30%.
In 1948, we did some tests which indicated that the harmful effect of
root disease is due to the disruption of the carbohydrate metabolism by rea-
son of severe infections of the cortical parts through which the circulation
of assimilated substances occurs. This disruption is shown in delayed draw-
ing off of sugars at night and the slow accumulation of them in the daytime.
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In one of these tests the amount of sugar in infected seedlings during the
daylight hours was 40% less than that in the healthy plants. In time the
disruption of the carbohydrate metabolism leads to: a sharp inhibition of
the growth of the plant. The plants are inhibited in passing through their
stages of growth and have lower weights than the healthy seedlings (see
Table 10).
Tests for studying the effect of root disease on the thinning out of a
crop of seedlings after emergence were made at "Sukhanovo" Sovkhoz in Moscow
Oblast on sugar-beet crops 94% infected with root disease. It was found that
after emergence approximately 70% of diseased seedlings remained in the field.
Furthermore, about 25% of the diseased seedlings died in the first 2 months;
the remainder survived, but their yield was lowered. In one of these tests
it was established that in a case of 73% infection of the field after emer-
gence, the sugar-beet yield was reduced more than 38%. Thus one important
side of the destructive activity of root disease was made apparent, which up
to the present had not been paid the attention due to it and which had been
frequently ascribed to other factors (principally vermin).
Susceptibility of Crops Rotated With Beets to the Basic Causal Agents
of Root Disease
Since the majority of root disease causal agents are typical soil para-
sitic fungi, it was very important to determine in what degree they are able
to infect other crops which are rotated with sugar beets and thus be preserved
in the soil. Special tests were set up in which some crops were planted in
artificially infested soil. The tests were conducted in a greenhouse in broad
clay dishes and a quadruple check was used. The moisture' content was kept at
70% of the maximum moisture-holding capacity. Dishes with sterile soil in
which the same crops were planted were used as controls. After 30 days a
complete record was made, the results of which are arranged in Table 11.
As can be seen in the table, A. cochlioidas infected only the sugar
beets. All the other crops were shown to be completely resistant to this
parasite. The two other fungi were unusually severe as regards the Infec-
tion caused by the fungi in beets, peas, clover, lucerne, and exparsette.
Vetch and sunflowers were considerably less affected and the grain cultures -
wheat and rye - were almost completely unaffected.
Tess it has been shown that in beet-crop rotation there are crops which
are susceptible to the basic causal agents of root disease. Due to these crops,
the causal agents are preserved in the soil. In addition, their preservation
can be due to some weeds (pigweed and others). Data can also be citsd on the
infection of sugar beets by root disease from previous crops. This data, taken
from a report by K. P. Zhukova, an aspirant of the laboratory, is shown in Ta-
ble 12.
It can be seen from the table that the largest number of sugar beets in-
fected by root disease occurred when the sugar beets were planted after beets
and the smallest number when they followed grain crops. Very high infection
of the seedlings occurred when the sugar beets followed clover, potatoes, peas,
and also wheat when the crop preceding wheat was also sugar beets,
The above test was conducted in a greenhouse in special boxes and th.:re-
fore the length of time any of the crops were cultivated was not observed,here,
which was particularly important in relation to the clover, the long cultiva-
tion of which promotes the accumulation in the soil of valuable saprophytic
flora which aid in the control of parasitic fungi. The data produced here
ought to be checked in crop rotation under field conditions. None the less,
even now we can assume that, to reduce the preservation of parasitic fungi
in the soil, it would be necessary first of all to introduce grassland crop
rotation with the greatest possible use of a grass mixture containing those
plants of the grass family which our..tests showed not.. to be infected by the ad-
tive causal agents of root disease and thus facilitate ridding+the.soil.,of
them.
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Beet sowing should be done after an uninfected previous crop (chiefly
after winter grains, which were planted on pure fertilized fallow, on
spring graJn after grass), where beets have not been grown for 2-3 years.
In addition, it is necessary to carefully control the weeds on all crop-
rotation fields...
Treating Sugar Beet Seeds With a Fungicide to Control Root Disease
Karlson had shown in 1890 that treatment of seed clusters with a 2%
solution of blue vitriol cut in half the infection by root disease. Car-
bolic acid (2%) showed a milder effect, but did not affect the germination
of the seed. In 1905, treatment of the seed by a fungicide was studied by
the phytopathologist Trzhebinskiy. After a great number of chiefly labora-
tory tests, he came to the conclusion that the best fungicides sefagainst
mer-
root disease were a 2% solution of blue vitriol and an 0.5% solution
curic chloride. A more detailed study of fungicides was made from 1925 to
19by Grushevoy at the Mironov Experimental Selection Station. A great
number of different fungicides, containing mercury, copper, arsenic, and
other poisonous ingredients, were tested. The tests showed thethefungi-
cides cides reduced the infection by root disease only slightly, but preparations
commonly impeded the germination of the seed. The mercury putP
were somewhat better than the other sabste:.ces tested. From the results,
it was concluded that treatment of the seed clusters by fungicides as a
measure for controlling rout disease is of little effect and therefore it
was not recommended in practice (3).
After the tests at the Mironov Experimental Station, the further study
of treatment of the seed by fungicides was almost completely discontinued,
because the principal causes of root disease were considered to be different
types of unfavorable soil factors, the elimination of which would reduce the
development of the disease. A minor role was relegated to microorganisms,
so that the treatment of the seed by fungicides was considered to be without
purpose, which was a premature judgment. Then it was found that one of the
most wideaWvAd, causal agents of root disease, Ph. betae, was carried
by the seeds. The necessity of treating the seeds with fungicides became
obvious, if only for the reason that the seeds had to be protected against
this particular fungus. Nevertheless, research on new fungicides capable
not only of destroying the infection in the seeds but also possibly capable
of protecting the young sprouts from microorganisms of the soil was indi-
cated.
A decision was made to restudy the treatment of seeds with fungicides.
N. V. Perkel', a co-worker of our +-+ed a large selection of
contemporary fungicides. Fie found that the ones which were most toxic for
the microorganisms and which did not adversely affect the germination of "Granozan the seeds, were the esapikilogr m of seed. dilution 1:30
com!
in the amount of 5 grams
pletely free the seed clusters of Ph. betae and offer considerable protection
to the seedlings r,ainst infection in the soil.
These mercury fungicides were tested under practical conditions at the
"Sukhanova" Sovkhoz of Moscow Oblast and the"Pyatiletka" Kolkhoz in Rakit-
yansk Rayon of Kursk Oblast. The results are shown in Table 13. its shown
in the table, the treatment of the beet seeds by the fungicides, in partic-
ular by "Granozan," reduced the infection of the crop ;y root disease, in-
creased the density of root spacing, and as a final result, produced an in-
crease in the sugar-beet yield. In addition to this, it was found that the
fungicides did not protect the seedlings in the field in the sam e degree as
in the tests using the fungicides against each causal agent of the disease
individually. In the crops treated 'nth fungicide, it was found that at
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first the fungicides promoted dense sprouting and relatively less infection
by root disease, but gradually the number of diseased plants increased, rea-h-
ing a considerable figure at the end of the test.
Special tests were set up to uncover the reasons for the poor protection
which the fungicides gave to the seedlings after the seedlings emerged from
the soil surface. We had noted the poor effectiveness of the fungicides un-
der field conditions in 1946, when we thought that it appeared to be connected
with the growth of A. cochliuides on the sugar-beet seedlings. As soon as this
fungus was found in infected sugar-beet seedlings and a pure culture of it iso-
lated, we quickly proceeded to investigate the effect which fungicides have on
it in comparison to the effect the fungicides have on P. de Baryanum. The test
was conducted in a greenhouse with the average temperature no lower than 180 C,
and the soil was artificially infested with A. cochlioides in one series and P.
de Baryanum in the other. The seed used was treated with "Granozan" in the
amount of 5 grams pcr kilogram of seed. During the whole series of tests, ob-
servations were made on the development of the disease, and the number of dis-
eased plants was recorded daily. The results of the tests are Sh:P n in Figure G.
It is clearly sewn that treating the seed with "Granozan" protects the seedlings
from P. de Bavyanum unusually well. In this section of the test, the treatment
by fungicide effectively promoted a high degree of sprouting of the seedlings
and their number remained more or less constant up to the end of the investiga-
tion. In the other section of the investigation, the subject treatment had al-
most no effect on A. cochlioides. In this case, the treated and untreated seed
produced almost en identical number of sprouts, but they quickly started to die
and were all dead by the end of the test. Thus it is shown that fungicides, in
particular "Granozan," protect the seedlings only from P. de Baryanum and do not
protect them at all from A. cochlioides, and that this is obviously what takes
place when fungicides are used in practice.
Surmising that in the given case the difference in the effect of the fungi-
cide was directly connected with peculiarities in the development of these fungi,
we set up a test .determin ing'the dynamics of infection of the sugar-beet seed-
lings in soil artificially infested with P. de Baryanum and A. cochlioides.
As can be seen in Figure 3, the development of the subject fungi is com-
pletely different in` character. P. de Baryanum develops chiefly in the early
stages of seedling growth and usually leaves most of the plants on the four-
teenth day after planting, On the contrary, A. cochlioides attacks the seed-
lings in the later phases of their growth, so that the greatest number of seed-
lings were destroyed by it in the second half of the test.
Quantitatively this difference was expressed in about the following decree.
If the first fungus on the fourteenth day has der royed 46 seedlings and in the
remaining time only 14 plants, then the second fungus destroys only 16 plants in
the first 14 days but kills 56 in the remaining 7 days. Thus the first fungus
is adapted to the earlier growth stages of the seedling while they are still ger-
minating in the soil, and the second fungus is adapted to the later stages and
infects them on the surface of the soil. Apparently the fungicide is adsorbed
into the soil and prevents infection of the above-ground part of the young plant,
either to a slight extent or not at all. In view of this, the treatment of seed
with a fungicide, despite its undeniable advantages, will be of limited value
until su.:h time as a method can be found for protecting the shoots from attack
by the parasitic fungus A. cochlioides, In this connection, a total disinfec-
tion of the soil in rows seems to promise the greatest degree of success.
In conclusion, it should be mentioned that much of the data given here ob-
viously ought to be carefully checked in practice.
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Conclusions
It was established in our tests that, contrary to previous, opinion, root
disease infects the strongly developed sugar-beet seedlings as well as the
weaker ones. In both cases, the disease is caused by microorganisms, but semi-
parasitic and even saprophytic fungi attack the weaker seedlings, whereas only
the very active parasites attack the healthier ones. Thus, contrary to pre-
vious opinion, the fungi in some cases represent directly the determining fac-
tor in the development of root disease.
The main causal agents in large-scale developments of root disease are the
parasitic soil fungi P. de Baryanum and A. cochlioides. Ph. betae is of second-
ary importance. This fungus is propagated chiefly from the seeds, from which
it can be eliminated by treatment with fungicides. All the other fungi found
in diseased seedlings are weakly represented (R. Aderraldi) or they are typical
semiparasites or even saprophytes (Fusarium, Alternaria, Penicillium). These
fungi are able to develop only as secondary causal agents (more frequently after
t
Pythium) or else they attack only the weak plants psu?ciy as a rasul~t of faulty
field management.
Typical parasitic soil fungi s,ause the greatest Infection of seedlings
when the moisture content of the soil is high (60% or higher) and the tempera-
ture is relatively high (160 and above). Ph. betae, on the other hand, infects
the seedlings to the greatest degree when there is a lack of moisture, i.e.,
when the seedlings are somewhat weakened. These data enable us to provide a.i
explanation for large-scale outbursts of root disease and also to check the
regions where it is most widespread.
The data compiled in this article permit us to assume that the control
of root disease should be reduced to the use of suitable methods of field man-
agement and some special measures. The field management methods must not only
provide for the normal development of the plants, but also create conditions
in the soil which inhibit the development and preservation of parasitic fungi.
Among these measures the following are recommended at present:
1. Introduction of grassland crop rotation, using a grass mixture of
leguminous and grass family plants which promote the greatest reduction of
parasitic fungi in the soil.
2. Drainage of wet soil ground water which occurs nearby.
3. Planting the beets subsequently to uninfectable previous crops, pre-
ferably after winter grain crops which had been planted in pure fertilized fal-
low or after spring grain crops which had been planted subsequently to grass,
and replanting beets on an area only after an interruption of 2-3 years.
4. Treating the seed before planting with "Granozan" in the amount of 5
grams per kilogram of seed or with the NIUFI-1 preparation in the dilution
1:300, using the moist type of treatment and letting the seed lie for 2 hours.
5. Loosening the soil over the crop with a light weight harrow (nail type)
before the emergence of the seedlings and promptly hoeing after they emerge. In
case of rains, the hoeing should be repeated to prevent caking and drying out of
the upper layer of soil.
6. Digging the beets out promptly and requiring the collection and removal
of all vegetative litter to reduce the preservation of infection in the soil.
7. Careful contra of weeds, since it is known that the root disease causal
agents.infect many weeds, as well as sugar beets. Control of weeds should be car-
ried out in all crop rotation fields, especially fields left in fallow prior to
winter crops, after which sugar beets are planted.
CONFIDENTIAL
14
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1. Broyakovskiy, N. V., Root Disease of Sugar-Beet Seedlings, Trudy Verkhn-
yachskoy Sortovodnoy Stantsii, 1934.
2. Buchholtz, W. F., Crop Rotation and Soil Drainage Effects on sugar-Beet
Tip Rot and Susceptibility of Other Crops to Aphanomyces cochlioides,
Phytopathology, Vol 34, No 9, p 85. 19 asur 3. Grushevoy, S. Ye., Treatment of Seed C$ustersewith Fur gicides asUMeao re
for Controlling Root Disease in Sugar
(16), p 149, 1929.
4. Karlson, Em., Wurzelbrand, Izvestiya Petrovskoy s.-kh. Akademii., 1890.
..hods for Controlling Them,
Murav'yev, V. P., Sugar-beet ir]sen=s a.n ..u Met
5.
Sveklovodstvo, Vol III, Part II, VNIS, 1939-
6. Tverskoy, D. L., and Zhukova, K. P., Relative Aggressiveness of Causal
Agents of Root Disease in Sugar Beets, Sakharnaya Promyshlennost', No 3,
1948.
7. Trzhebinskiy, I.N., Effect of the Disinfection of Sugar-Beet Bulbs annoy
the Soil on the Intensity of the Root Disease of Crops,
vrnmvshlennosti, p 496, 1907,
8. SIbid, eedlings,oVestnik SarkharnoyDPromyshlennostiC,,ppg586, 1907. in Beet
rTaules and figures follov_]
Table 1. Propagation of Fungi as Affected by Previous Crop
De ree of Occurrence of Fungi
Previous
No of Diseased
Seedlings (~)
P de Baryanum
Fusarium
Pb. betae
Cron
47
6
13.6
Beets
60.9
41.7
.
Wheat
46.4
34eO
60.6
15.E
;1.3
29.3
55.7
16.5
Grass
15.1
Average
51.1
35.2
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55.3
1
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Table 2. Mycological Analysis of Diseased Beet Seedlings
Place From
Which Soil
Sample Was
Taken
Preceding
Crop
Quantity of
Diseased
Seedlings (')
Kharkov Oblast
Kharkov State
Selection Station
Beets
Wheat
Lucerne
95.8
21.6
67.1
Nemerchanak State
Beets
100
Selection Station
Wheat
20.9
Clover
65.8
"Chervonyy Zhovten"
Beets
39.0
oZ
Vladovo-Lyulenetsk
Beets
100
Selection Station
Wheat
19.0
Clover
30.0
Chernigov Oblast
Nosovskiy ROSKh
Beets
100
Regional Depart-
ment of Minist
of Agriculture3J
L'govsk Selection
Beets
88.0
Station
"Strang Sovetov"
Beets
57.0
KO
"Pobeditel" Kol-
Beets
100.
khoz -
Seedlings Killed
Microorganisms N)
Before
After
Emergence
7.5
85..8
50.6
71.6
10.0
15.7
0,.0
0.0
0.0
0.0
0.0
2.3
20.8
65.2
:LO.4
9.0
31.4
9.6
90.4
55.4
-33.9
0
7
0.9
35.0
58.0
20.0 C]
.
12.8
27.2
51.1
24.8
u.6
19. o
T
10.0
7.0
28.5
28.5
14.2
4
71.
0
17
83.0
35.7
84.2
3.4
T
9.2
.
0
12
2.0
26.8
38 3
40.9
m
.
14.0
6.o
44.3
10.5
71.2
34.0
16.0
84.0
54.2
72.0
r
50X1-HUM
7.0
42.0
31.0
55.0
13.7
20.6
0.0
36.0
32.5
67.5
6.8
18.7
28.0.
72.0
30.6
71-0
--.
13.1
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Seedlings Killed
Microorganisms
Quantity of
Diseased
Before
After
es
barium
Rhizome a
Seedlings Emergence Emergence Ph
hium Uhano c
.
20.0
7.5
5.9
83.3 16.5
30.2
11.9
0.0
0.7
.
100
3
25
12.7
0.9
0
70
.
0
0
100
37.8 75.8
u 47
3
100
.
0
0 60
2
9.
.
63.1
4.0
25.0
.
9.
0
8
60.0
19.0
14.0
3.0
.
40.0
Voronezh Oblast
Voronezh Experiment
Station
Ramonak Selection
Station
Preceding
Crop
Beets
Clover
Lucerne
Beets
Wheat
Clover
Penzena Oblast
Beets 100
h
S
K
edsk RO
S
os
Moscow Oblast
"Sukhanovo" Sovkhoz Beets
Wheat
Clover
Potatoee
Beets
Alma-Ata Oblast
"Passvet" Kolkhoz Beets
"Pervoye Maya",X-a ;$ects
khoz, Brigade No 3
Tashkent Oblast
Ak-Kayak Agricul- Cotton
tural Experiment Wheat
Station Lucerne
96.3
0.8
93.0
4.5
59.4
27.0
95.4
0.1
95.3
0.0
0.0
13-.0:
0.0
U.0
2.0
17.0
9.0
35.0
19.0
*.Small amount of fungi, percentage not calculated.
U.
88
6
42.3
73.6
8.0
28.0
.
77.0
33.8
53.0
20.9
4
1
27.1
14.2
30.7
r"
19.0
85
9
.
3
25.4
67.2
14.5
24.5
.
5.6
48.0
62.9
16.0
25.3
1
50X1-HUM
0
0
--*
.
4.0
15.8
20.0
80.0
4.0
13.7
86.3
3
0
.
16.0
9.8
40.2
50.0
38.8
52.2
13.4
38.5
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Propagation of Fungi (%)
Crop Seedlings (~i) Py hium Aphanonyc Rhizoctoaia Fusarium
Beets 73.5 38.4 65.8 12.7 33.6
Wheat 39.5 31.1 52.3 11.3 43.2
Clover 37.2 41.7 17.6 12.3 36.3
Lucerne 42.4 48.3 10.4 25.5 60.4,
Averag: 4.3.1 39.9 36.5 15.6 43.4
50X1-HUM
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Table 4. Percentage of Diseased Seedlings in Soil Infested by Various Fungi
Percent of Seedlings
Cauaal Agents
Healthy
Medium and
Intensely
Diseased
Kill
ed
Control
100
0.0
0.
0
P. de Baryanum
26.4
27.0
36.
6
A. cochlioides
10.6
20.2
59.
0
R. Aderholdi
18.8
26.4
41.
6
R.:solani
56.2
13.4
9.
8
Ph. betae
27.3
38.5
5.
2
A. tennis
92.3
0.0
0.
0
I. cinerea
97.5
0.0
0.
0
Fusarium strain No 1
84.8
4.2
0.
0
- 15 -
CONFIDENTIAL
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Table 5. Effect of Moisture Content of Soil on infect-ion
of Seedlings by Causal Agents of Root Disease
Percent of Seedlings
Causal Agents
Health[
Severely
DLse~ ar sed
Killed
Control
100
--
P. de Baryanum
70.0
14.0
9.4
A. cochlioides.
72.5
14.5
8.2
R.erho1dl
3.7
61.0
35.6
R. solani
24.8
47.0
5.7
Ph. betae
27.7
53.7
B. cinerea
69.9
5.8
10.9
Fusarium iitrain No 71 .
67.0
8.0
3.7
A. tennis
66.4
2.8
0.0
Variables of
(
the Test Diseased Seedlings s
Loosened twice 8.6
Loosened many times 55.9 -
Diseased. Seedlings NO
Mild
Avg
Severe:
-
Killed Seedlings (~)
15.5
6.8
10.5
58.6
5.1
5.1
6.8
27.1
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6cF.1
ent of Seedlings
r
P
Percent of Seedlings
e
c
Medium and
Seberely
Diseased
lth
Killed
Medium and
Severely
HealthDiseased
Killed
y
Hea
100 .
10.0
30.5 19.4
38.0
1.2 15.7
78.4
27.3 16.2
50.0
0.0 17,0
88.0
13.5 29.7
37.4
11.7 21.3
52.4
41.5 44.7
0.0
70.0 11.7
1.9
34.1
8.0
69.4 12.1
1.5
87.6 o.6
3.8
95.8 1.6
0.0
86.8 1.4
0.0
97.5 o.8
0.0
81.7 4.1
0.0
94.0
Table 6. Effect of Loosening thA Soil on Infection cf Beet Seedlings by the Fungus P. de Baryanum
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Tr-,'Ole -7. Effect of Temperatufe on the. ection of Seedlings
by Causal Agents of Root Disease
250
Percent of Seedlings 3.'^-r Temperatures (?CL
210 16.50
Type of
Fungus Diseased Killed Diseased Killed Diseased Killed riseased Killed Diseased Killed Diseased Killed
P. de Bar-
yeana 100 83.3 100 100 100 80.0 95.2 64.3 60.2 50.8 - -23.0 23.0
R. Ader-
holdi 100 100 100 10') 100 79.5 95.2 83.7 75.8 60.8 '10.1 3.2
R. solani 34.6 0.0 73.2 44.1 82.2 20.0 54.8 4.6 38.7 6.2 8.2 3.1
Ph. betae 62.9 8.1 75.6 58.5 78.7 36.1 51.2 24.0 1$.1 0.0 8.3 0.0
B. cinerea 11.1 0.0 4"E.1 8.2 0.0 0.0 9.5 9.5 5.1 3.2 3.8 1.6
A. tenuis 26.2 0.0 l .7 2.8 2.2 2.2 0.0 0.0 5.0 0.0 0.0 0.0
Fusarium
strain :..i
No 71 5.5 5.5 7.3 8.8 12.2 12.4 0.0
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1
Table 8. Effect of Temperature on Development of Root Disease
in Naturally Infested Soil
Quantity of Seedlings
No of Killed Seedlings
Completely Emerged in
t
ol
Before Emergence
Aft-3r Emergence
Temp (~C )
r
Percent of Con
30.7
52.9
4.7
42.4
26.5
30.0
9.0
61.0
20.7
27.7
24.1
48.2
17.2
36.2
19.0
44.0
"0
24.4
12.6
12.-,
-)
Table 10.
Effect of Root Disease on Seedlings
No of Seedlings in the Follnwina P
ee (d) Ape Wt
f
One Plant
0
Condition of
1st Pr
2d Pr
3d Pr
4th Pr
in Percent of
s
f L
of Leaves
of Leaves
of Leaves
Control
Seedling
eave
o
Healthy
Slightly infected
5.4
24.3
40.5
29.8
Infected to an average
degree
6.)
44.8
48.3
0.0
53.2
Severely infected
15.4
76.9
7.7
0.0
23.1
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Table U. Infection of Various Crops
of Root Disease
Percent of 3ee3linas
Aphanomyces
Crops
Healthy
Wheat
100
Barley
100
Beets
.. .0.0
Peas
100
Vetch
100
Clover
100
Lucerne
100
Bsparikette
100
Sunflowers
100
Rhizoctonia
Degree of
Infection:
Avg and
Degree of
Infection:
Avg and
_
Killed
Beal
Degree of
Infection:
Avg and
Severe
Killed
Severe Killed.
H
Severe
0.0
0.0
93.7
0.0
0.0
'2.5
6.2
0.0
0.0
0.0
97.3
0.0
0.0
}.00
0.0
0.0
5.8
94.2
1.2
3-5
95..3
0.0
5.1
83.0
o n
0.0
0.0
0.0
8.3
65.7
0.0
58.3
41.7
0.0
0.0
86.8
0.0
7.9
26.3
0.0
0.0
0.0
0.0
1.1
0.0
9
-.
0.0
93.2
0
0
95.0 3r.
0.0
0.0
1.1
3.3
87.8
.
01-
0.0
0.0
3.5
4'3.4
32.1
18.7
81.3
0.0
0.0
87.5
0.0
10.0
10.0
2.5
Sanitized Copy Approved for Release 2011/10/19: CIA-RDP80-00809A000600390321-2
Sanitized Copy Approved for Release 2011/10/19: CIA-RDP80-00809A000600390321-2
Sanitized Copy Approved for Release 2011/10/19: CIA-RDP80-00809A000600390321-2
CONFIDENTIAL
Table 12. Infection of Sugar Beets by Root Disease
After Various Preceding Crops
Infected Seedlings (`~)
Healthy
Preceding
Crops Seedlings (%
Wheat, wheat,
wheat
Wheat, oats,
PeAs
74.6
68.1
Wheat, spring
wheet, peas
28.9
Wheat,'beets,
wheat
15.3
Wheat, barley,
beets
0.0
ld
Average
Severe
Killed
Seedlings
Mi
22.0
0.0
0.0
3.4
9.5
5.7
16.8
12.0
0.0
32.5
14.8
11.9
11.1
36.0
14.0
11.7
15.5
39.8
7.2
92.8
Table 13. Results of Using Mercury Fungicides in Practice
Place Tested, Name of
and Year of Tent
Chemical
Percent of
Reduction of
Infection by
Root Disease
,
"Sukhanovo", Sovkhoz Mos-
Cnv, 0h1n t (;rattozan in
doses of 5 gr per kilo-
gram of seed (1947)
36.2
Same (1948)
43.4
NIUIF-1, in 1:300 dilu-
(1948)
tion
21 4
"Pyatiletka" Kolkhoz Rakit-
yanskiy Rayon, Kursk Oblast.
Granozan in doses of 5 gr per
kilogram of seed (1948)
51.0
*Data by N. V. Perke.l'
Increase
Density of
Sprouts -
Density of
Planted Roots
Yield of
Roots
57.3
30.0
15.0*
44.2
29.4
--
41.0
29.0
16.0+E
CONFIDENTIAL
Sanitized Copy Approved for Release 2011/10/19: CIA-RDP80-00809A000600390321-2
Sanitized Copy Approved for Release 2011/10/19: CIA-RDP80-00809A000600390321-2
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Figure 1. Quantity of Seedlings Related to the Total Number of Seeds
Sprouted in Sterile Soil and Soil Art1AU,ally Infested With
P. de Baryanum. I - sterile soil, II -.infested, III - growth
of fungi in a Petri dish
h.~
/I
y B P. di Ooiyanum
4 r
-DAYS
Figure 2. Dynamics of the Emergence and Destruction of Sugar-Beet
Seedlings for the Planting in Naturally ?3lfested Soil of
Seed Treated With a Fungicide and That Which Has Not Been
Wanted
A
Mnye
Dynamics of the Dying of Seedlings in Soil Artificially
Infested With P. de Baryanum and A. cochlioidas
- END -
Ct41 WENi0AL
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