Foreign plant quarantines in-service training series


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14 Synchytrium endobioticum

United States Department of Agriculture
Bureau of Entomology and Plant Quarantine
Apr. 1, 1940
Foreign Plant Quarantines In-service Training Series. t'o. 6
(No. 1 is an introductory and expilanantory number.)
Prepared hy N. Rex Hunt

Name of Disease: Potato wart, potato canker or cancer, black -ca*.,
cauliflower, warty disease.

Name of Pathogen: Synchytrium endobioticum (Schilb.) Perc.
Syn. Chrysophlyctis endclobiotica Schilb.

Hosts: Hyoscyamus niger, Lycopersicum esculentum, Nycandra ,hysa-
lodes, Solanum alatum, S. album, S. chacoense, S. commerscni,
S. dulcamara, S. .jamesii, S. nodiflorum, S. tuberosum, S.
villosisimum, S. villosum, and by inoculation Datura inermiis,
D. metel, Physalts francheti, Schizmnthus pinnatus, Sol.-ntm
atropurpureum, S. marginatus. S.miniatumo S. miniatum rubricaule,
S. miniatum viridicaule, S. niger, S, nigrum macroc3rpum, S.
nigrum chlorocarpum, S. racemigerum.
Ducomet and Diehl (7) state that a study of tuberiferous
species of Solanum showed that types susceptible to wart are
present in all chromosome types, (1, 8, 15, 21)

Part attacked: On potato the tuters are particularly susceptible,
infection being through the eyes usually, but all underground
parts of hosts are susceptible. Leaves and stems Lecome in-
fected also at times on potato at least. (13)

Place of origin: South America.

Country of first report: Hungary, 1896. (The part of Hungary in-
volved later became part of Czechoslovakia)
It is said the disease cannot be found now in the area
from which Schilbersky first reported it. The disease ap-
pears to have been in England (1, 4) at the time it was
first reported.

First report from the U. S.: Pennsylvania, Sept. 1918.

Present distribution: Algeria, Austria, Belgium, Bolivia, Canc-da,
Czechoslovakia, Danzig Free State, Denmark, Englan.d, Faroe
Islands, Finland, France, Germany, Ireland, Japan, Malta
(said to have teen eradicated hut see (16), Miquelon Islar.di,
Newfoundland, Peru, Polar.d (in an area formerly part of
Germany), Portugal, Rumania, Scotland, Spain, St. Pier:e,
Sweden, Switzerland, Union of South Africa, Unitedr Stes,
Wales. It has been reported from Russia, apparc;.tly in
error. (19)


Factors affection severity: Susceptibility of host is the most
important factor. Wart is said to be confined to areas
with growing seasons of 140 days or less. Soils with tem-
peratures of 60 to 64 F. are said to favor development of
wart and with temperatures of 70 to 72 F. to inhibit de-
velopment. Periodic flooding of soils followed by drainage
and aeration favors development of wart. (2, 10, 11, 16)

Methods of spread: Any agency that will distribute soil, tubers
or other plant parts containing or bearing spores, including
drainage water, farm implements, men, animals, diseased
tubers, tubers with adhering spores, manure from animals
fed diseased tubers, garbage, etc. Local spread seems to
be especially prevalent in areas of dense population with
small holdings. Long distance spread is most likely to
occur with potato tubers in the form of adhering spores or
inconspicuous lesions. (6, 8, 10, 22)

Losses incurred: In Finland as a whole the average loss due to
wart, on infected land, was 7.4%. In Austria and in England
planting of a susceptible variety in contaminated soil has
been known to result in practically a total loss of crop.
(1, 10, 18)

Comparative losses: Strict state quarantine measures and the use of
immune varieties has prevented determination of possible
crop losses in this country. Where a prompt change to re-
sistant varieties is made, little direct loss results, though
the substitute variety may yield less and be of less de-
sirable quality.

Control methods: Quarantines and use of immur.e or highly resistant
varieties are the usual control measures. The use of fungi-
cides is not profitable in general. Continuous growing of
cultivated non-susceptible crops makes possible planting of
potatoes once in eight years without serious losses.
Where the infected area is small, eradication by slow
starvation or by treatment of the soil with chemicals may be
profitable. (2, 10, 12)

Quarantine action: Section 7 of the plant quarantine act of August
20, 1912, provides that the quarantine provisions of this
section, as applying to potato wart, shall become and be
effective upon passage of the act. Under this provision the
Potato Wart Quarantine No. 3 was signed September 20, 1912
(issued September 28, 1912), effective immediately. More
recently the entry of potatoes has been governed by the
potato regulations which were originally issued December 22,
1913, and since revised or amended several times. These
regulations are based on potato wart primarily.

Description:. On susceptible varieties of potato the disease is
charac.teriZed by wart-like outgrowths sbn the* tubers or re-
placing tubers at the end of stolons. Theso "w.'arts" are
more commonly developed from the eyes of tubers, less often
on stolons or bases of stems. The warts are whitish at first
but turn black and often become watery as they get older.
When exposed to light at the ground surface, warts are green.
Warts may be extremely small or may be larger than the tubers
on which they are borne.
On resistant varieties of potatoes infected cells mn.y
turn brown and fleck off without producing spores and v.'h,-n
sori mature, they may be difficult to find even ",hen ex-
amined with extreme care. Such infections could not be found
with certainty by inspection methods applicable to commercial
shipments or even to small lots of potatoes.
In structure S. endobioticum is a very simple fungus,
without mycelium. The first infections in the spring are
produced by oval shaped one-ciliate zoospores about 2 mu
in length which are formed when the resting spores or spo-
rangia germinate. These first infections develop as sori
each of which divides to form about five summer sporarnio.
Within a few days after infection takes place there may be
an abnormal enlargement and multiplication of host cells to
form a tumor or in highly resistant varieties there may be
little enlargement of the host tissues. The summer sporangia
germinate by the production of 200-300 oval shaped one-ciliate
zoospores about 1.5 mu long. If these zoospores have been
mature for two or three days before there is sufficient
moisture to cause their release, a large part of them may
act as gametes, gametes from different sporangia uniting in
pairs to for-m zygotes. If the zoospores cause new infec-
tions such infections develop as sori and produce summer spo-
rangia, but infections produced by zygotes from resting
sporangia. Resting sporangia become dark brown, thick walled,
more or less globular and 50-70 mu in diameter. These rest-
ing sporangia may remain viable for some time but usually
germinate as soon after maturity as water is available whether
that is within an hour or two or is delayed a week or more.
Zoospores from resting spores may begin to disintegrate
within a couple of houis or so after the sporangium ruptures
if they are unable to infect a host and those from summer
sporangia in less than an hour. Either zoospores or zygotes
may infect wart tissue as well as normal host tissue. The
enormous .ulimbers of sporangia, particularly of resting spo-
rangia, that may be produced during a season, and the ability
of the resting sporangia to remain viable for year's enable
the fungus to survive ordinary crop rotations and cause hcal,.
damage at times in spite of the fact that it is not wind
borne, that the zoospores and zygotes which infect the host
are able to travel very short distances by their own efforts
and are short lived.

-f 4 -a

(The last paragraph is largely based on the publication by
Miss Curtis, (3). See also (5. 8, 9, 0, 13, 14, 22)



(1) Anonymous
1904-1931 Leaflet No. 105, Board of Agriculture and Fisheries
(of Great Britain) was first issued in April, 1904, and has
been revised from time to time by the Board and its suc-
cessor, the Ministry of Agriculture and Fisheries. The
leaflet summarizes information regarding potato wart, methods
of control, immune varieties, and quarantine measures in the
British Isles.
Revision of December 1908.
Although the disease has been known to potato growers in
the Liverpool district for some 15 years, it was not reported
to the Board until 1901. Also in Wales, Scotland and else-
Leaflet No. 105, Ministry of Agriculture and Fisheries,
rewritten May 1928.
Wart originally discovered in Upper Hungary (now part of
Czechoslovakia) in 1896. May have been in England ten,
twenty, or even more years previously. In any case the two
earliest British records, made in 1898, show that the disease
was already present here then, but those who saw it at that
time did not diagnose it correctly. "The first accurate
account of Wart Disease published in this country was based
on experiments carried out by Professor Potter with material
collected in Cheshire in 1900, and is to be found in the
Board's (now the Ministry's) Journal for Decemter, 1902."
Reported in Scotland in 1907 and in Ireland in 1908. -- Dis-
ease found in Austria, Belgium, Czechoslovakia, Denmark,
France, Germany, Holland, Norway, Poland, Sweden, and Switzer-
land in addition to original place in Hungary. Also in Malta,
South Africa, New Foundland, Canada, and U. S. p. 2 3
Losses due to Wart disease.--It is impossible to estimate
with accuracy our present actual losses from this disease.
They must be on the whole relatively small...... ". ......even
under field conditions instances are not unknown where the
planting of a susceptible variety in contaminated soil has
resulted in practically a total loss of crop." p. 5. Spread
of the Disease, of itself, by seed, water, man, animals, dung,
etc. Hosts p. 5 & 6. p. 5 Disease has appeared in a crop
grown in land originally contaminated with sporangia, but in
which no potatoes had been grown for periods of eight and
twelve years. "......there is apparently at present no instance
on record where soil, once well contaminated with the resting
sporangia of the Wart Disease fungus, has ever yet become quite
free from them and absolutely safe for the renewed planting of
a susceptible variety in it." (Also in 1931 edition)
Leaflet No. 105,. Oct. 1931 revision.
p. 2 adds Finland, Roumania, Japan to countries infected and


says recent findings in So. America are believed result of
introduction from Europe.
p. 6 Solanum villosisimum and S. album, Nicandra physilodes,
Solanum chacoense, S. commersonii, S. jamesii. S. ncdiflorum,
and S. villosum among hosts listed.

(2) Bell, R. H. and Hartman, R. E.
1939 Potato Wart in Pennsylvania. pp. 1-8, map. Mar. 1,
1939. (mimeographed)
Historical summary of wart, surveys, quarantine and
especially treatment work in Pa. Quarantine removed from
some areas after annual tests for 5 years showed freedom
from wart. "Since the inception of the eradication program
in 1934, a total of 3,911 gardens in the 21 treated areas
have been planted to susceptible potatoes and nr.ot a single
new infection has been uncovered." From investigations and
observations conclude that soils with temperatures of 6C to
64 F. favor development of wart and with 70 to 72 F.
inhibit development. Wart confined to areas with growing
seasons of 140 days or less. Without cultivation disease
lives in soil 20 years; with fallow or semi-fallow culture
without host plants is starved out in 10 years. Expect to
eradicate the disease in Pa. by the use of 2,000 pounds of
Ammonium Sulfo-Cyanate per acre on generally infected soil
and of 2 quarts of Mercuric Chloride (1-1,000) rer square
foot for small infected spots.

(3) Curtis, K. M.
1921 The life history and cytology of Synchytrium endobioticum
(Schilb.) Perc., the cause of wart disease in potato. Phil.
Trans. Roy. Soc. London, Ser. B, 210: 409-478. 1921.
An illustrated, detailed study of the organism.

(4) Cuthbertson, W.
1915 Wart Disease of Potatoes. Gard. Chron. 57: 97. Feb.
20, 1915.
Wart said to have been figured and c'.escrited in Journ.
of Hortic. of Dec. 15, 1898, by G. Abley (in England). His-
torical and general information, immune vars., etc.

(5) Dix, W. and Kuglmorgen
1932 Untersuchungen uber die deimung der Dauersporangien von
"S nchytrium endobioticum." (Investigations on the germin-
ation of the resting sporangia of Sychytrium endobioticum.)
Pflanzenbau, Pflanzenschutz u. Pflanzenzucht 9: 209-16. (Ab-
str. in R.A.M. 12: 322, 1933).
Potato extract from either susceptible or immune var-
ieties hastens germination. "The highest percentage of germin-
ation after four months in this series (82) was obtained in
a 6 percent solution of expressed leaf juice of the resistant


variety." The variety was Preussen. Spores rea(y to germin-
ate at about 5% a month" .... so that in about .wo years all
would presumably have germinated." Stimulants have no effect
after a time, so treated and untreated spores might have the
same percentage germinated after 6 mos.

(6) Ducomet, V. ar.d Foex, E.
1928 Essais effectues en 1927 au champ d' experiences etabli
par 1' Institut des Recherches Agronomiques a Euss-Hershach
(Bas-Rhin) en vue de l'etude de la maladie verruqueuse (Syn-
chytrium endobioticum (Schilb.) Perc.) de la oirmre de terre
(Trials conducted in 1927 on the experimental field laid out
by the Agricultural Res. Inst. etc. for investigation of wart)
Comptes rendus Acad. d' Agric. de France 14: 442-45. 1928.
(Abstr. in R.A.M. 7: 596, 1928.)
Wart infection and resistance of potato varieties. -
Studies showed infection was transmitted (1) thru the soil to
a depth of 50 cm., (2) thru soil of field infected 2 yrs.
before, (3) thru sweepings from a cellar where infected
potatoes had been stored, even tho disinfected with lime,
(4) thru refuse of a village in the infected zone, (5) thru
soil of a meado',.' irrigated with water from infected zone,
(6) thru soil adhering to turnips dug from a field infected
in the previous year. Air infection spread tests were nega-

(7) Ducomet, V. and Diehl, R.
1936 La galle verruqueuse de la Pomme de terre (Synchytrium
endobioticum (Schilb.) Perc.). Mise au point de la question
de la resistance des varieties. (A critical summary of the
question of varietal resistance.) Ann. Epiphyt., N. S. i,
pp. 57-79, 2 maps, 1936. (Abstract in R.A.M. 15: 601-2.
Sept. 1936.)
Notes on introduction into France and present distribu-
tion there. "In the north of France new infection centres
are due more to the introduction of foreign tubers than to
the spread of already existing diseased areas." (R.A.M.)
"It appears that under certain conditions favorable to tissue
proliferation some reputedly resistant varieties may be very
slightly attacked and serve as a source of spread." (R.A.M.)
"A study of tuberiferous species of Solanum shoved that types
susceptible to S. endobioticum are present in all chromosome
Groups." (R.A.M.)

(8) Esmarch, F.
1927 Untersuchungen zue Biologee des Kartoffelkrehscs. II
(Investigations on the biology of the potato vwart.) Angew.
Bot. 9: 88-124. 1927. (Abstr. in R.A.M. 6: .:,-6, 1927 see
also R.A.M. 5: 577-8, 1l26 & R.A.M. 3: 477. 1924.)


After-ripening period of resting sporangia varies with
conditions. Under favorable conditions most ripen and germin-
ate within a year, a few persisted to 3- years. Little
moisture required for germination. Rain causes more in-
fection than capillary moisture. Limits of sphere of in-
fection are 10 cm. laterally, 10 to 15 cm. upward, 15 to
20 cm. downwards in a vertical direction. "The zoospores are
primarily transported toward the tubers by currents of soil
water, their own movements being of little significance in
this respect. In the early stages of their journey, the
motion of the zoospores appears to be without definite di-
rection: only in the immediate vicinity of the tubers is a
chemotactic stimulus probably exerted by the susceptible

(9) Glynne, Mary D.
1934 Infectivity of summer sporangia of Potato wart disease
in incipient infections on varieties immune in the field.
Nature 134: 253, 1934. (Abstr. in R.A.M. 14: 55, Jan. 1935.)
Wart developed in the laboratory on potato varieties
apparently immune in field. Infection soon sloughed off.
"Inoculations on the susceptible Arran Chief variety from
such incipient infections bearing summer sporangia which
developed in the laboratory on Snowdrop, Bishop, and Ben
Cruachan (apparently immune in the field) gave positive re-
sults." (R.A.M.)

(10) Hilli, A.
1932 (The reasons of the spread of potato wart (Synchytrium
endobioticum (Schilb.) Perc.) in Finland and abroad.) Valt.
Maatabouskoet. Julkais. No. 46. 249 p. 1932. From the
English abstract p. 231 249:
p. 232. speaking of factors of spread "The most important
of these are the transportation and trade of potatoes and
the way of cultivation due to the kind of settlement. Other
factors of culture (the transportation by soil, manure,
fertilizers, animals, people and implements and by the work
of eradication of potato wart) are in this respect of greater
significance than natural factors (moisture, temperature,
light, oxygen, kind of soil, soil reaction, host-plants,
parasites). Writer thinks wart as tolerant as potato. Suf-
ficient moisture present in cultivated land to germinate
wart spores any time. Resting sporangia endure long drought.
p. 233. "On the surface flow of water potato wart can be
carried at least 200 metres in cultivated lands just being
tilled, as experiments carried out in Pyhajarvi parish in
Uusimaa ad. dist. have shown." Wart organism endures cold
and heat better than host. Light of little significance.
Nature of soil has no great influence. Influence of soil
reaction slight. Influence of other hosts slight.


Successfully inoculated Datura inermis, D. metel, Phys2lis
francheti, Solanum atropurpureum, S. mirpinatum, and S.
tuberosum; few sporangia on hosts other than potato. "In
Finland (Pusula parish, Hyrkkyla village) it has been pos-
sible to ascertain by experiments, that Synchytrium en.lobioticum
resting sporangia retain their viability in meadow land at
least 13 years (Tables 1 and 2, p. 28-29). The strength of
the infection of the disease has been greater in meadow lands
than in such soils which are annually tilled." The table on
p. 28 shows 80% contagiousness the 13th year; the table on
p. 29 shows 75% contagiousness and 55% contagiousness in
cultivated soil 7 years and 8 years after potatoes were grown.
p. 234. "In Finland an ordinary 8 year rotation of the
cultivation of corn and mowing grass has prevented the dis-
ease in ordinary agricultural cultivations." Fertilizers
increase wart, resulting in practice of using "fresh" soil
from sound fields as fertilizer in Finland. Transporting
of wart by human feet mentioned by Sanders (1919) and Neu-
weiler (1923). "Also in the potato wart areas of Finland
the spreading of the disease from one cultivation to another
in the earth adhering to footwear has been proved." "It
was proved in 1929-1930 on the potato wart infected areas
of Hyrkkyla village of Pusula parish, that Synchytrium endo-
bioticum sporangia were preserved in life even over winter on
implements plastered with earth."
p. 235. Wart sporangia occur in intestines of earthworms
in wart infected areas. Quarantines recommirended, Finnish
laws require that imported potatoes be grown at least 50 kms.
from nearest wart infected areas. (50 kms. almost equal 31
miles) immune vars. "The cultivation of potato varieties
immune to wart disease has considerably affected the extent
of spread of potato wart, as this is the most general and
reliable eradicative means."
p. 236. Formalin, 10 litres of 10% per sq. metre failed so
first infected area in Finland was given 3 litres of 20%
unrefined sulphuric acid and copper sulphate 1 kg. pr sq.
metre. Apparently successful. Chemical, eradication not
practicable. Wart found in Finland in 1924 in 5 small areas,
in 1925-26 no new areas found, but since 1927 new infected
areas have been found each year. "The writer's detailed
investigations of the potato areas in Finland made in 1S25-
1932 have proved however that the disease has reached Fin-
land with three different consignments of potatoes (1893
to Pusula from England, 1929 to Nauvo from Holland and 1929
to Joutseno and Lappi from Germany) and spread from these
centres of infection caused by them to the surroundings and
even to more distant tracts through the agency of cultural
factors." The Holland potatoes are consigned by Messrs.

- 10 -

N. A. V. von Ende & Zoons of the Hague.
p. 237. It is stated that a detailed study of the spread
of the disease in Finland, including records of movement
of families as shown in church registers of the communities,
was made and is given in main text. Some of these noted on
pp. 237 & 238. On one estate losses in gardens of workers
averaged 30.6% while on the estate fields it was only 5 %
due to the 3 to 12 year interval between potato crops on
this land.
p. 239. "At the end of 1931 there proved to be potato wart
in Finland (Table 46, p. 117) all in 28 villages on the
areas of 15 communities. Isolated areas said to be at the
time a total of 205, had been in the possession of 163 culti-
vators. The total area of the tracts infected was 23 hectares
87 ares and the average crop-loss 7.4%."
pp. 239-240. Give some details of infection in different
population densities, different soil types, different lengths
of time between potato crops.
p. 241. In Sweden at end of 1930, 1725 hectares infected
according to information from Thore Lindforss. Norway 48
localities infected.
p. 242. Disease thrives in Faroe Islands where average July
temperature is below that of Finnish Lapland. About 6,000
infected cultivations in Denmark at end of 1928 according to
p. 243. 1741 communities in 280 district areas infected in
Germany, everywhere about but especially Prussia.
p. 244. "In Holland potato wart occurs (Fig. 12, p. 172) in
different parts of the country. In the year 1920 the disease
was found in 135 cultivations making a total area of 75.36
hectares. In 1922 the said area was already 410 hectares
and it has continued to grow yearly (e.g. in 1928 by 142
hectares)." Chiefly around Winschoten, in northern part of
country but also in southern part on banks of river Maas and
near Amsterdam. Spread almost exclusively in parts with
slight rainfall. Distributed largely according to density
of population.
pp. 245-248. Discussion of situation in various countries
especially with reference to correlation of wart and popula-
tion density. 247 wart in Poland in area formerly part of
Germany. 248 report for Japan on basis of information
given by Pethybridge to writer in 1931. No specific informa-
tion. p. 249. Believes So. America original home of wart.
Fig. 12. Communities in Holland infected with wart disease
of potatoes by end of 1927. Drawn up by the author on
particulars presented in literature. 55 numbered and named.
(on p. 172.) (Maps of other countries shown also.)

- 11 -

(11) Hintikka, T. J.
1929 U-er die Verbreitung, des Kartoffelkre!%es in verscl-eidener,
Landern sowie uber einige klinntisI:i.en Faktoren der ver-
seuchlen Cebiete. (On tie distribution of potato wart in
different countries and on some climatic factors of the in-
fested areas). Vallion M4aataloukoetoiminnan Julkaisuja 23,
102 pp. 11 maps, 1929. (Finnish with Germany summary) (Ab-
stract in R.A.M. 12: 50-52. 1933)
Immune vars. listed with countries of origin. Discus-
sion of genetics, variability of susceptibility in different
countries, etc. Effects of soil, light, moisture, etc.; wet
localities seem to favor disease, but in ', disease occurs
in comparatively dry areas. Coldest Euroreai: centers of
infection in Finland a,.d Sweden lie within isotherms 3
to 4 C., warmest at 20, south of which point wart occurs
only in mountains or in rainy districts,

(12) Hunt, N. Rex, O'Donnell, F. G., .nd Marshall, Rush P.
1925 Steam and chemical soil disinfection v/ith special refer-
ence to potato wart. Journ. Agr. Re-. 31: 301-363. Aug.
15, 1925.
This paper gives the results of exrerinents in treat-
ing soil to eliminate wart, by the use of steam alor.e, of
chemicals alone, and of stesam and cLemicals combined. It
also gives the results of studies on soil penetration by
steam heat and by chemicals and a discussion of potato growth
in chemically treated soil. (Copies of this paper are avail-

(13) Kohler, E.
1931 VWeber das Verhalten von Synchytrium endobioticum auf
aufalligen und widerstar.ds-fahigen Kartoffelsorten. (On
the behavior of Synchytrium eniobhioticum on susceptible and
resistant potato varieties.) Arb. Biol. Reichsanst, fur
Land und Forstwirtsch. 19: 263-284, 1931. (Abstr. R.A.M.
11: 69-70. 1932) Author differentiates following grades of
1. All or nearly all sori fail to develop.
2. Most sori abortive, intact ones on upper infected leaves
and portions of stem.
3. Most sori intact on upper infected leaves and mid-stem
region of full shoots; conspicuous : restricted
to stem base and lower leaves.
4. Sori predominantly intact; extensive nec-oses almost all
on lower leaves.
5. Necroses barely perceptible, but all or nearly all sori
develop completely.
Mode of infection same for susceptible and resis-.ant varieties
and number of successful penetrations sam.e. Death of parasite

- 12 -

in resistant varieties result of necrotic processes in host.
In severe infection the whole diseased area dies and forms a
dark brown layer over infected organ. Growing organs gradually
shed this layer. Varieties in grades 1 and 2 are absolutely
immune in field, those in 3 to 5 are partly immune and partly

(14) Kohler, E.
1931 Der Kartoffelkrebs und sein Erreger (Scnchytrium endo-
bioticum (Schilb.) Perc.) Landw. Jahrb. 74: 729-8C6. 1931
(Abstr. in R.A.M. 11: 321, 1932.)
This is a complete study of disease and fungus, history,
distribution, morphology, biology, hosts, specialization,
technique, control, bibliography.

(15) Kohler, E.
1936 Untersuchungen uber Syvnchytrium endobioticum (Schluss-
bericht). (Studies on Synchytrium endobioticum (final re-
port) Z. Pflkrankh,, 44: 214-223, 1936.) (Abstr. in R.A.M.
15: 524-5. Ag. 1936).
Successfully inoculated Schizanthus pinnatus. Solarm
dulcamara, tomato (Lucullus and Tuckswood varieties), S.
nigrum vars. macrocarpum and chlorocarEum, S. miniatum and
vars. viridicaule and rubricaule, and S. racemjge um. Simp-
toms less marked than in susceptible potatoes.

(16) Lepik, E.
1935 On the Distribution of the Potato Wart Disease, Syn-
chytrium endobioticum. Phytopathological Experiment of the
University of Tartu in Estonia, Bul. No. 28, 1935. (See
also Lepik abstract in R.A.M. 13: 799)
Author gives a map showing distribution and sources of
infected potatoes (indicated by arrows) but says errors were
made in marking the direction of distribution in some cases.
"The literary data, which the writer of this article is
convinced are v,'rong, have been left out." This includes
some of his own reports in a previous paper (R.A.M. 13:
799). He says there is a difference of opinion as to the
source of infection in some cases, Holland disclaiming re-
sponsibility for some distribution of wart attributed to
her. He seems to think there is ground for argument but
commends the Holland service. Claims wart is absent from
Esioc.;ia, Latvia, Lithuania, and Russia. In Finland, With
regard to conflicting reports as to Malta quotes Pethybridge,
"With regard to the Island of Malta, : am not able to state
with certainty whether Synchytrium endobioticum is still
present in that island, but we have official information
that in the spring of 1914 a few cases of Wart Disease were
observed at Lia and Musta in the variety, Up-to-Date, the
seed of which had been imported from England. It was stated
that the disease was stamped out immediately and, therefore,

- 13 -

it may not be in the island now. On the o+hr hliand, when
one remembers how difficult it is to absolutely eradicate
a soil parasite like the one in question, it seems quite
possible that it may still be in Malta....." Mlap lists
Canada, Newfoundland, U.S.A., Peru, Faroe Islands, Portugal,
So. Africa, Malta, and Japan. The map is small and not
very clear but has dots indicating infections in the
Isles, France, Switzerland, Germany, Czechoslovakia, Austria,
Hungary, Poland, Norway, Sweden, Finland, Holland, Belgium,
and perhaps others. Pethybridge, G. H. Fungus ni.d other
diseases of crops 1928-1932. Ministry of Agric. and Fisher-
ies, Bul. No. 79, 1934 is only Pethybridge article in litera-
ture cited, but quotation cites Pethybridge (1935 in litt.)

Lindfors, T.
Potatiskraftan i Sverige: des utbredning och
instill ar 1935. (Potato wart in Sweien; its distribution
and control up to the year 1935) Medd. Vazixtsy'
Stockh. 11, 1935. (Abstr. R.A.M. 14: 787-8. Dec. 1S35.)
Wart distribution in Sweden since discovered in 1912
followed by apparently complete disappearance until 1928,
360 infection centres covering 4,329 hectares. Spread largely
by seed potatoes also by manure, domestic animals (csp.
poultry), agricultural implements, and running water. C.ows
and other birds may be involved in spread. Hosts, by in-
oculations, include Solanum nigrum, S. dulcamara, and Hyos-
cyamus niger. Wart spores said to have rema.i:ed viable 13
years in Finland and 10 years in Denmark.

Neumann, H.
Ein Versuchsfeld zur Bekampfung des Kartoffelkrebses.
(An experimental field for the control of potato wart.)
Oestrr. Zeitschr, fur Kartoffelban, 1931, Sondernumml:er,
pp. 115-116. (Abstr. in R.A.M. 11: 321-2. 1932)
Field of 1,000 sq. m. in Austria planted in 1931 to the
susceptible var. Alma, harvested Sept. 11. Of 3,000 plants
only 35 were free from infection and these appeared to be a
different variety. About 200 kg. of potatoes harvested,
i.e., approximately the quantity used for seed. Plot believed
uniformly infected and well adapted for soil disinfection

Pissareff, V. E. and Vesselovsky, I, A.
Translation of Russian title Potato selection in the
Leningrad region, Ann. State Inst. of Exper. Agron. Lenin-
grad, 7: 290-300. 1929. (Abstr. R.A.M. 9: 401, 1930.)
Among the medium-early and medium-late varieties, Great
Scot was very resistant to virus diseases, late blight, and
wart disease (Synchytrium endobioticum), but is r.ot a heavy





cropper in the region; Parnassia was also very resistant to wart
disease, but is a poor producer in the neighborhood of Lenin-
grad. (From R.A.M. abstract Later articles in R.A.M. say
wart is not in U.S.S.R.)

(20) Selaries, P. & Rohmer, G.
1936 La maladie verruqueuse de la Pomme de terre en Alsace.
(Potato wart disease in Alsace.) Ann. Epiphyt. E. S. i,
pp. 23-55, 26 figs., 1936. (Abstr. in R.A.M. 15: 601. Sept.
Variety resistance tests show some resistant varieties
diseased at times in field. Laboratory infection tests
show some vars. resistant in field readily diseased, but
infection not apparent. Resting stage produced in lesions
on resistant vars. as shown by microscope examination.

(21) Weiss, F., Orton, C. R., and Hartman, R. E.
1923 Investigations of potato wart. U. S. Dept. Agr. Dept.
Bul. No. 1156, pp. 1-21. May, 1923.
I. The varietal and species hosts of Synchytrium en-
dobioticum, by Weiss and Orton.
II. The adaptability and use of wart-immune varieties
of potato in the quarantined areas of Pennsylvania.
By Hartman.
III., The stability of wart immunity, by Weiss.

(22) Weiss, F. and Brierley, P.
1928 Factors of spread and repression in potato wart. U. S.
tech. bull. No. 56. March, 1928.
This paper includes proof that apparently healthy po-
tatoes may bear adhering spores and become infected when
planted. Agencies of spread distribution of wart spores in
surface 8 inches of soil only, duration of infectiousness
of soil, tomato hosts, resistance of spores to heat and to
seed disinfectants are discussed.

Synohytrium endobiotioum

Plate 1

., S

Showing "warts" caused by S. endobiotioum on stolons of
Bliss Triumph (at left) and on a Netted Gem tuber (at right).
The size of the warts produced varies with varieties and
conditions. Bliss Triumph tends to produce small warts on
tubers, larger ones on stolons.

(From U.S.D.A. Department Bull. No. 1156. May, 1923. Plate III)

Synohytrium endobilotioum
Plate 2

1. Resting sporangia developing in wart tissue. 2. Resting sporangium
in tissue. 3. Resting sporangium with zoospores fornai-., in it. 4.
Zoospore from resting sporangium. 5. Zoospore enterin- a host cell.
6. Nearing the end of the prosorus stage. 7. A sorus bLowing 5
sumner sporangia. 8. Summer sporangium nearly ready t. discharge
zoospores. 9. Zoospores from summer sporangium. 10. Z spores
acting as gametes uniting to form a zygote.
(After Miss K. M. Curtis, in Roy. Soo. London, Phil. Trans., Ser. B.
210 4D9-4a78. Pis. 12-16. Jan. 14, 1921.)



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