Foreign plant quarantines in-service training series


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14 Solerospora spp.

United States Department of Agriculture
Bureau of Entomology and Plant Quarantine
April 1, 19W)
Foreign Plant Quarantines In-service Training Series. No. 5
(No. I is an introductory and explanatory number.)
Prepared by N. Rex Hunt


Quarantines 15, 24, and 55.

Downy mildew diseases due to species of Sclerospora are among
those covered by three foreign plant quarantines. Quarantine 15, the
sugarcane quarantine, promulgated June 6, 1914, does not name any of
the diseases responsible for its promulLation but among the serious
foreign diseases of cane which its enforcement tends to keep out are
species of Sclerospora. Quarantine 24, the corn disease quarantine,
promulgated April 29, 1916, effective on and after July 1, 1916,
lists two species of Sclerospora among the diseases responsible for
it. Quarantine 55, the seed or paddy rice quarantine, issued July
17, 1923, effective on and after September 1, 1925, starts the list
of diseases responsible for its promulgation with a species of

While much additional information regarding the Sclerosporas
has become available since these quarantines were promulgated, there
are many unsolved problems in identity, life histories, host ranges,
and geographic distribution of these fungi.

Uncertainty as to the identity and relationship of various
foreign Solerosporas is relatively unimportant from the quarantine
standpoint at present since we must guard against all of them. But
the entry and establishment of a form, the status of which is
doubtful, would immediately change the situation. There would be the
question of modifying the quarantined area without proper data on
which to make such modification. Control measures for the newly
introduced pathagen could not be satisfactorily worked out in the
absence of full knowledge of its life history, host range, and
amenability to various control measures.


Methods of spread.

The genus Sclerospora is in the same subfamily, Peronosporae,
as the general Phytophthora, Plasmopara, and Peronospora, all of which
cause serious downy mildew diseases of important crops. These fungi
get the name "Downy mildews" from. the fact that most species produce
a downy growth of conidiophores on the surface of affected areas.


The spread of Solerosporas is aocomplished.n. three principal
ways: (1) Local spread during the growing season is usually by means
of air borne conidia. These conidia are produced in enormous numbers
in some species and may be responsible for rapid spread which will
badly damage or ruin a planting within a few days after sporulation
starts. These conidia are produced during the night and collapse and
die in the morning if not already distributed and established by that
time. They are therefore not directly responsible for spread to
distant areas. (2) The sexual spores, called oospores, are produced
in thick-walled cogonia, are themselves thick-walled, and are capable
of remaining viable for years. many of these oospores may remain in
or on the soil to infect succeeding crops. Others become scattered
about as spores, oogonia, or in bits of the host tissue, get mixed
with seed of the host or of nearby plants and are transported to new
localities. (3) Sometimes the fungus is spread in the form of
living mycelium. In sugarcane cuttings used as seed pieces this is
especially likely to occur. One species is said to be systemic in
a perennial wild host* Since the host range of the various species
is not well known, others may be systemic in perennial hosts and thus
liable to be transported in living parts of such hosts.

For some species of Sclerospora conidia only are known.
Where host material is available at all times either as perennials or
as successive crops no other stage is needed to maintain the fungus.
For other species, conidia are unknown or rare. Such species may
spread little during the season but may fill the soil with resting
spores and are easily spread to new localities with seed or other plant
parts bearing oospores.

Named species on corn, sugarcane, and rice.

Eight named species, some of which may be synonyms, are
recognized as infecting corn, or sugarcane, or rice, or same combina-
tion of these hosts. In addition there are reports of undetermined
species which may add to the list. Notes regarding these species are
given in the accompanying work sheets. Attention may be called to
the following points:s

Two of the eight named species are already established in this
country on the mainland. These are S. graminicola, which attacks a
variety of hosts including corn, and S. macrospora which attacks a
number of hosts including corn and rice and is the species meant to be
included in the rice quarantine (No. 55) but misspelled there.

S. graminicola is readily separated from other species because
its coni'ia geminate by producing zoospores instead of germ tubes.
Later in the season oogonia are produced on some hosts. As oogonia
are seldom produced on corn the fungus probably gained entrance as
oospores with seed of some other host.


S. maorospora produces oogonia in great abundance in the
leaf tisTues of its hosts. Conidia, though reported to occur, are not
usually found. It is the only form regularly producing oospores on
corn, but has not been reported to occur on corn in the United States.

Of the six named species attacking corn and sugarcane and not
known to occur in this country, all produce conidia which germinate
by the production of germ tubes. Oogonia have been reported for three
of the speoies--S. misoanthi which occurs on sugarcane, S. sacchari
which attacks su'arcane and corn, and S. sohi which atTacs 'corn.
S. miscanthi and S. saochari are probably disseminated with cane
cuttings used as seed pieces and also in the form of oospores while
S. sorghi is disseminated as oospores with sorghum or other seed.

Of the three remaining species, S. mavdis which attacks corn,
may be a strain of S. sorghij S. philippTnensis which attacks corn may
be a strain of S. s'cchari; and S. spontanea which attacks corn and
cane may be a sTrain of $. miscanthi. its possible that the four
latter species are in reality a single variable species or that further
work will show a larger group of related species. Unless oospores are
produced their spread would be limited to local distribution as
oonidia and to transport in living host tissues.

Some of the species of Solerospora under discussion are
separated from others because of different host reactions or different
spore measurements. However, many fungi develop strains which prefer
certain hosts or certain varieties and it is known that a species of
Solerospora may virtually destroy some varieties of corn and scarcely
affect others near by. Spore sizes within a species are variable
also. Measurements by different workers vary and in the case of S.
sacchari two distinct sets of measurements for the conidia are given
in the original description. Whether such variations are due to
mixtures of two species, or some of the so-called species are unstable
hybrids, or the variations in size depend on host, environment, length
of day, methods of collecting and preparing spores for measurement,
or other conditions, the variations do occur and add to the difficulty
of clearing up the status of Sclerosporas. Cross inoculation data
would be very helpful in clarifying the situation.

Foreign species 'on corn.

On corn conidia are produced in abundance by S. maydis, S.
philippinensis, S. sacchari, S. sorghi, and S. spontanea but no
oospores are produced and "Wes'on_, 38) an'T Palm (17) were unable
to demonstrate that the disease was carried over in corn grains in
which the tissues had been invaded by mycelium. Hence corn is an
important factor in rapid local spread of downy mildews but has not
been proved to be important of itself in carrying the disease over
from season to season or in carrying the disease from one area to

" 4 -

distant areas* Further work may show that infected grains do carry
the disease. Unhusked roasting ears might carry actively sporulating
areas for long distances under modern storage conditions. Suscepti-
bility of corn varieties is extremely variable and oospores may be
formed in some varieties. Perhaps the most serious risk with corn is
the fact that it is often planted in close proximity to hosts on which
oospores are produced in abundance, that the corn .may become contam-
inated with such oospores and that if imported and planted the heavy
conidia production on corn might serve to spread the disease over
large areas and to other hosts before the nature of the disease could
be established and eradication effected.

Foreign species on sugarcane.

On sugarcane S. philippinensis and S. spontanea are only
known to produce conidia but S. miscanthi and S. sacochari produce
oospores. The first two species might be eradicated by use of a short
host free period but the two latter species would probably persist in
the soil for sone time after removal of the host plants if the oospores
had been released before removal of all diseased host material,

Infected sugarcane cuttings as used for propagation would be
unlikely to show any evidence of such infection. Growing all imported
sugarcane under rigid quarantine conditions until found to be disease
free eliminates the risk of introducir, Sclerosporas with such material.

The seeds of sugarcane might harbor the mycelium or be contam-
inated with oospores and should be handled with equal care.

Species on rice.

So far as known all Sclerospora downy mildews reported as
occurring on rice belong to S. maorospora which is now known to occur
in the United States.

Foreign species on other hosts.

The seed of hosts on which oospores of these foreign Soleros-
poras are produced and of other plants grown near by are likely to be
contaminated with oospores. Sorghum is not listed in quarantine No. 24
but oospores of S. sorghi are produced in abundance on it. Spread of
this fungus to new areas and continents has probably been accomplished
by transport of contaminated sorghum seed in most cases at least.

There are other named species of Sclerospora occurring on
grasses in foreign countries which might affect corn or sugarcane or
might possibly be identical with undetermined species listed as
occurring on corn or sugarcane.


Possible importance of these Sclerosporas in this country.

The Sclerosporas do not seem likely to become outstandingly
destructive in this country except in the Mississippi Valley,
especially the lower part, or other areas with high humidity during the
early part of the growing season. While much of the corn belt may have
periods of weather favorable for the development of conidia and the
rapid spread of these downy mildews, the fact that some other host
would seem to be required to carry the fungus from season to season
makes control possible except where such hosts may be perennial or
where a continuous succession of hosts is maintained. With sugarcane,
losses would probably be severe since resting spores, of same species
at least, are produced on cane and conditions in cane fields are likely
to favor rapid spread-of the downy mildews locally. Establishment of
these Sclerosporas in the lower Mississippi Valley on hosts of species
infecting corn would provide a reservoir from which air currents could
carry infection up the valley to plantings of corn somewhat as wheat
rust is carried north, though the delicate structure of the Sclerospora
oonidia should greatly restrict the length of any one "jump."

While the available information regarding the foreign
Sclerospora downy mildews of corn and sugarcane is scattered, incomplete,
contradictory and difficult to evaluate, their possible destructiveness,
the absence of studies designed to enable prompt and efficacious
eradication or control in the event of their introduction, the decided
possibility of their entry, and the importance of these and other hosts
of the pathogens involved combine to fully warrant continued drastic
quarantine measures to prevent the entry and establishment of these
foreign downy mildews.


Name of diseases Downy mildew, Green-ear disease.

1Jame of pathogen: Soclerospora graminicola (Sacc.) Schroet.
Syns. Peronospora graminicola Sacc.
Peronospora setariae Pass.
Protomyces graminicola Saoc., etc.

Hosts: Members of the tribe Paniceae of the family Gramineae,
especially. Include Pennisetum typhoideum, Setaria
(Chaetochloa) viridis, Chaetoohloa spp., Panicum miliaceum,
Zea mays, Andropogon halepensis.

Part attacked: Leaves, sheaths, stem above and below the ground level.

Place of origin:

Comtry of first report:

First report from U. 8S. Wisoonsin, 1884.

Distribution: Europe, Asia, Africa, North America.

Factors affecting severity: High humidity and moderate temperatures
at night when conidia are produced presumably are necessary
for maximum production of conidia and local spread. Usually
formation of numerous oogonia soon ends production of conidia.
Conditions conducive to infection by oospores are not known
apparently. Host susceptibility is an important factor in
determining relative losses. Association with other hosts
may affect the percentage of infection also. In an area where
corn was the only host the disease might soon die out

Methods of spreads Air borne conidia are responsible for local spread
during the growing season in Florida (40) Chaetochloa
(Setaria) magna but spread from plant to plant during the
growing season does not seem to occur in India (5) on
Pennisetum typhoideum. The fungus seems to be systemic in
C. magna, which is a perennial, and hence might be carried in
living plant parts of this host. Oospores are produced in
abundance on most hosts and may be blown about or carried by
surface water or may get mixed with seed of the host or of
nearby plants.

Losses incurred: Apparently losses are not usually severe as to the
total crop although individual plants may be a total loss and
small areas are sometimes seriously affected. Losses in 15
districts in Manchuria were reported as 10 to 25% on Setaria
italica in 1927-29 (28).


Comparative losses Losses are small everywhere apparently and no
comparison is practical on basis of the information noted.

Control methods: Destruction of infected plants, crop rotation,
clean seed.

Quarantine action None.

Description: Symptoms vary with the host, age at time of attack and
spore form or forms produced. On corn only the conidial stage
is produced, causing discolored areas on the leaves but
causing relatively little damage normally. On Pennisetumn
typhoideum in India (5) the fungus causes "green ear disease"
so called because the solid spikate ear is wholly or partly
transformed into a loose, green head composed of a mass of
small, twisted leaves. Complete sterility of the head may
result. Infected young leaves show chlorotic areas or long
streaks, conidiophores emerge in masses through the stomata
covering the chlorotic areas with whitish downy growth from
which the conidia are produced. Conidia germinate by
production of zoospores but these do not seem to produce new
infections. Later, affected areas on older plants may turn
brown, great numbers of brownish oogonia being produced in
the tissues. Each oogonium contains an oospore. They are
formed in such abundance that the tissue between veins is
largely destroyed resulting in the splitting or shredding of
affected leaves.

In the case of systemic infections of Chaetochloa magna
in Florida (40) a pallid yellowish area is produced at e
base of the oTdest infected leaf and gets larger on each
successive leaf, running out in irregular, jagged extensions
toward the tip until the later leaves are yellowish white
throughout. Seedlings infected from oospores in the soil
presumably develop much as the systemically infected plants
but all leaves may be wholly chlorotic practically from the
time of emergence. In addition to the systemic infections
there are numerous leaf spots on other plants of the host,
presumably the result of infection by zoospores. These spots
produce some conidia but oogonia do not seem to develop in
them and they soon dry up, apparently without producing any
oogonia. These spots are never conspicuous.

Conidia 19-31 x 12-21 mu on Pennisetumn typhoideum in
India according to Butler (); 11-5 x 10-21 mu, usually
16-22 x 12-16 mu on Setaria viridis in Minnesota and Washington,
D. C., according to Weston (37=;1-56.9 x 11-24.9 mu on
Chaetochloa (Setaria) magna S Florida according to Weston and
Weber (40); 15-28.9 x 13-22.9 mu on Pennisetum typhoideum at

o8 -

Poona, India, according to Weston and Uppal. (?2) Mature
conidia have a papilla of dehisoence prominen-at the apex,
germination being by the production and release of 3 to 12
or more zoospores which are irregular kidney shaped with 2
cilia on the concave side, 9-12 mu in diameter when they
settle and round up. Oogonia with heavy uneven walls.
Oospores 22.5-35 mu averaging 32 mu in diameter according to
Butler (5), 19-44.9 mu, 541 of 1000 measured being 31-37 mu
and 814 being 29.-38.9 mu according to Weston and Weber (hO),
25-46.9 mu in diameter on Setaria italica, Pennisetum
tphoideum and S. viridis, 400 measurements on each host but
source of materTal not stated, over half of oospores on each
host 33-36.9 mu according to Weston and Uppal (42).
Bibliography, (5, 8, 9, 23, 24, 28, 3, 39, 40, 41, 12.)


Name of diseases Wheat downy mildew.

Name of pathogens Soleropora macrospora Sacc.
Syn. Solerospora oryzae Brizi

Hosts. Wheat and maize especially; also on oats, barley, rice,
rye, and wild grasses of the genera Phalaria, phragmites,
Glyoeria, Agropyron, Lolium, Bromus, Festuca, Holcus,
Alopeourus. Not found on corn in the United States but
reported on corn in Australia and elsewhere.

Part attacked Leaves.

Place of origin:

Country of first reports (Described from Australian material on
Alopeourus in 1890)

First report from Ue S.: California, Tennessee, Kentucky, 1921.
(Collected in California in 1919, probably present several
years in Tennessee and Kentucky).

Present distribution: Australia, Abyssinia, Bulgaria, Japan, France,
Italy, Russia, Spain.

Factors affecting severity: Seems to persist in low bottom lands
only and to cause destruction in areas that have been flooded
or at least remained wet for some time.

Methods of spread: Since conidia are not produced, usually, spread
must depend on dissemination of oospores by air currents,
surface water movement, transportation of spore bearing
plant parts, etc.

Losses incurred: Severe in low ground, especially flooded areas,
very little elsewhere.

Comparative losses: Apparently little loss in U. S., but losses
might be heavy any place in temperate zone in low wet ground
if susceptible crops were grown on it each year after
infection occurred there. Said to have caused considerable
damage in Europe at times.

Controls Crop rotation with eradication of all wild hosts nearby
should give control, or growth of non-susceptible crops on
the low spots at all times.

Quarantine action: The rice disease quarantine, No. 55, is based on
this and other diseases, the specific name being misspelled

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as S maorocarpa in the quarantine.

Description: Three types of symptoms on immature wheat were noted
by Weston (36): (1) Excessive tillering, all shoots soon
withering, browning and dying. (2) Internodes shortened,
leaves striped or yellow and fleshy, twisted or curled and
held in unnatural positions. (3) Leaves yellowed, thickened
and twisted but not so stunted as in (1) and (2). There are
also intergradations and combinations of these symptoms.

In maize the disease may be found on plants with twisted
and abnormal growth, particularly of the tassel. A more
accurate diagnosis is made by examination of apparently
infected leaves with a hand lens by transmitted light for the
innumerable spores in diseased tissue and pellucid dotted
appearance of such tissue.

Conidia rare, said to have been found on Holcus lunatus
in Italy (18), papillate, 60-70 x 38-52 mu on sort peduncles.
Also obtained on infected wheat plant parts in water (19).
Germination by production of zoospores. Oospores 60-65-mu in
diameter according to Saccardo, caused shredding of barley
leaves in California (12) but often remained imbedded in
tissues. Some oospores germinated in moist chamber (18) and
produced macroconidia which in turn germinated by the
production of zoospores. Mature macroconidia are lemon-
shaped with the papilla well marked, 75-80 x 55-60 mu.

Bibliography: (12, 18, 19, 29).

- 11 -

Name of disease: Downy mildew.

Name of pathogen: Sclerospora maydis (Rac.) Palm (not Butler)
Syn. Peronospora maydis Raciborski
Sclerospora javanica Palm

Hosts: Zea mays, hybrids of maize and teosinte.

Part attacked: Leaves and other parts above roots.

Origin: Java (7)

Country of first report: Java, 1897.

First report from U. S.: None.

Present distribution: Java, Sumatra, Belgian Congo (1937).

Factors affecting severity: Humid nights as for other downy mildews
of maize favor production of conidia and local spread.

Methods of spread: Local spread during the growing season is by
conidia, largely air borne. The fungus may be carried over
from season to season on a succession of hosts only, as
oospores are not known. Unless oospores are formed movement
of the disease from one country to another would require
transport of living infected plants, so far as we know.

Losses incurred Severe at times, damage of 30 and 50 percent of
the crop in some localities in the Dutch East Indies in 1920

Comparative losses: Said to be very destructive in Java at times.
According to Dr. R. D. Rands (verbal statement) a series of
American varieties of maize being grown at the experiment
station in Java were naturally attacked and virtually no crop
produced on any of them. Javan varieties were not so
susceptible. The disease is said to be capable of being very
destructive in Belgian Congo where the natives make successive
plantings, but the crop has no sale value there, hence the
losses are not very important.

Controls Use of resistant varieties, and of a host free season
might be effective.

Quarantine action: Under the original name Peronospora maydis
Raciborski this is first on the list of diseases responsible
for the promulgation of the corn disease quarantine, No. 24.

- 12 -

Description Symptoms are said to be siailar to those of
Solerospora sorghli. According to Steyaert's (24) description
of the disease on maize in Belgian Congo the first leaves
attacked do not always show the disease in an acute form. By
the time the 7th or 8th leaf is produced the severity of the
disease is usually manifest. Chlorotic zones start from the
base of the leaves and progress to the point. The leaves
remain small, narrow, chlorotic and erect While normal leaves
fall in curves. The whole plant has the appearance of being
weakly and dwarfed. The chlorotic tissues take a greenish
yellow tinge or even pure yellow. On plants that have made
a normal start the symptoms are not so pronounced. It is,
in general, only the bases of the leaves which are attacked.

Long chlorotic striations start from the base of
infected leaves and advance along the ribs, often more
rapidly along the midrib. These striations later become
confluent at the base, brownish, necrotic spots appear and
secondary organisms develop.

The tassels may be conspicuously deformed and the ears
equally deformed.

In describing the disease in Java, Palm (17) divides the
symptoms into three types two of which are similar to those
given by Steyaert and a third type in which the disease
produces narrow, inconspicuous brown stripes full length of
the lowest leaves and growing progressively shorter until only
the tips of some of the younger leaves are affected and the
top leaves are normal green throughout.

Palm's measurements for the conidia are 19-26 x 15-20 muna
while Steyaert's are 17.5-27.5 x 13-75-17.5 mu. Germination
is by production of a germ tube.

Oospores are not known. How did it get from the East
Indies to Belgian Congo?

Bibliography (1I7, 20, 24, 32, ).

- 13 -

Name of disease: Downy mildew.

Name of pathogen: Sclerospora miscanthi T. Miyake.
Syn. Sclerospora macrospora (?) tentative
determination used by T. Miyake (16).

Hosts: .iscanthus (Eulalia) japonicus, M. sinensis, Saccharum
officinarum, and S. spontanea.

Part attacked: Leaves.

Place of origin:

Country of first report: Formosa (found in February, 1911).
First report from U. S.:

Distribution: Formosa, (Philippine Islands only place listed by
Stevenson and Rands)(25).

Factors affecting severity: No information but might be similar to
S. macrosora which it is said to resemble.

Methods of spread: No information.

Losses incurred: Miyake (16) speaking of it in Formosa says its
power of spreading is small and the extent of the damage
very limited and it only occurs over a small area.

C omparative losses:

Control methods:

Quarantine action: None specifically but would be covered by the
general statement used in the sugarcane quarantine, No. 15.

Description: On Miscanthus japonicus (16) the affected leaves split
up into threads resembling those of millet affected by S.
raminicola. Sugarcane planted following the clearing off
of diseased M. sinensis became affected, the leaves stripping
and the stems being liable to be broken or bent over at the
nodes. Cane is mostly attacked from June to September or
October when growing rapidly, especially in poorly prepared
fields, according to Miyake's fellow station workers.
Conidia were not found for some time after publication of the
description but are said to be similar to those of S. sacchari.
Whether similar to the long or the short conidia of S. sacchari
or both is not stated. (Or is it possible one groupbelongs
to each species?) Oogonia on M. japonicus, 52-75 x 45-69 mu,
reddJish brown, walls 3-.8 mu up to or 4 tim'nes that, uneven;

oospores 40-55 mu round, yellow, with a glossy yellow wall
4 mu thick. Weston (41) measured large numbers of the
oospores and found mosT of them were 47-48.9 mu. in diameter.
Bibliography: (1-, 13 ).

- 15 -

Name of disease: Philippine downy mildew of maize.

Name of pathogen: Sclerospora philippinensis Weston
"Syns. Sclerospora maydis (Rac.) Butler (not Palm)
Sclerospora indica Butler
Sclerospora maydis Re inking

Hostsi Zea mays, Euchlaena luxurians, Andropogon sorghum.

Part attacked: Leaves and all parts except roots.


Country of first report: India, 1912.

First report from U. S.s None.

Present distributions: India, Philippine Islands (1916).

Factors affecting severity: High humidity at night is necessary for
maximum production of conidia and of spread of disease in
epidemic form.

Methods of spread: Oogonial stage unknown, hence possibility of
spread from area to area unknown, except possible transport
of diseased fresh host material which might continue to
sporulate under favorable conditions. See above also.

Losses incurred; In the Philippines losses of 40 to 60% were frequent
in the maize growing areas of Laguna and Batangas. Losses in
imported varieties sometimes 100%.

Comparative losses, In India losses appear to be light with only
individual plants affected.

Control miethodst Where infection is light as in India, destruction
of infected plants might be effective. In the Philippines
sanitation and crop rotation might be useful in some cases but
breeding for reslstar. varieties should be attempted.

Quarantine action: Partly responsible for promulgation of the corn
disease quarantine, No. 24.

Description: Symptoms vary with the age of the corn plant when
infected, means of infection, variety, environmental condi-
tions, etc. In general the disease manifests itself by loss
of chlorophyll in more or less sharply defined areas of the
leaf, by the production of whitish down, mostly on the
chlorotic areas and by alterations in normal growth of the

- 16 -

plant. Effects of the disease may show any time from the
putting out of the third or fourth leaf until tassel and
ear mature.

In young plants two or three narrow longitudinal stripes
of pale yellow to whitish color show at the base of the
nearly developed second, third, or even fourth leaf in
contrast to surrounding normal green. The leaves above these
earlier ones are almost wholly ohlorotio, remain narrow and
become rigid. Stem growth is checked, so plant is more or
less dwarfed. The leaf sheaths develop almost full length
and hence overlap. The weakened plant may be attacked by
secondary parasites and killed or may produce a few grains.

When older plants are infected the oldest leaf to show
infection, that is, basal ohiorotic stripes, may be the
fourth and up to the eighth leaf. The basal discolored areas
and the stripes are broader and larger on the oldest leaves
infected than on leaves of plants showing the disease early
and get progressively worse on the leaves above. In these
older plants the shape, size and flexibility of the leaves is
not so much altered from normal, but the invasion of the
fungus may cause the midribs to become so brittle they break
so the leaf hangs straight down along the stem. Reproductive
structures of the host show all sorts of malformations. Ear
production is delayed.

In later stages of the disease especially in plants less
heavily attacked the diseased areas regain most of their
color so they can scarcely be distinguished from non-invaded

Susceptibility varies with age but plants with kernels
hardening may be attacked through young suckers. In such
cases only the lower leaves of the old plant may show narrow
pale irregular broken stripes. No conidiophores are produced
on these areas.

Conidiophores are not produced on any of the types of
infected plants unless conditions are favorable.

The symptoms on teosinte are less marked than on corn,
the percentages of infection and loss are less and fewer spores
are produced.

In sorghum the percentage of infection is very low but
plants are infected when young and soon die, no further
infection being noted.

17 -

Conidia elongate, variable in size, 17.-52.9 x 11-24.9
mu (37), usually 27-39 x 17-21 mu, hyaline, germinating by
production of a germ tube, spores produced at night.
Oospores not known.

Bibliography: (6, a, 24, 50, 35, 37, 38).

- 18 -

Name of disease: Downy mildew of sugarcane.

Name of pathogen: Sclerospora sacohari T. Miyake.

Hosts: Saccharum officinarum, Zea mays, Euchlaena (teosinte). (see (L)

Parts attacked: Leaves and stalks.

Place of origin: New Guinea?

Country of first report: Formosa, found in 1909, description
published in 1912. Found on cane recently introduced from

First report from U. S.:

Distribution: Fiji, Formosa, India, Japan, New Guinea, Philippines,
Queensland, Siam. (May have been eradicated from India. An
attempt was made to eradicate it in the Philippines.)

Factors affecting severity: Apparently there is only a limited
production of conidia on sugarcane but on corn and teosinte
conidia are produced in such numbers that it is unsafe to
plant them in the neighborhood of sugarcane fields. Humid
nights presumably are required for production of conidia, as
in other species.

Methods of spread: Local spread during the season is due to air
borne conidia presumably as in several other species. At
least a part of the distant spread has been due to carriage
of the fungus in or on sugarcane cuttings used for seed pieces.
The role of oospores and of living mycelium in this carriage
is not known.

Losses incurred: No definite data available. Said to be severe on
corn and on sugarcane growing near infected corn and teosinte,
in Formosa. According to Weston (535) it may attack cane "with
violent intensity."

Comparative losses: Apparently the disease is not usually severe on
cane in Australia. This may be accounted for by the fact that
corn usually does not become infected in Australia. Available
data do not permit any authoritative explanation of the
extreme differences in behavior of this fungus. (but see (43).

Quarantine action: The corn disease quarantine No. 24 was based on
several diseases, this being one of those named.

- 19 -

Description: Based on the translation of Miyake's bulletin (16) by
Hiroda & North, on cane when a leaf is affected by this
fungous disease it first shows a few yellowish stripes
running parallel with the veins. These stripes increase in
number until most of the leaf loses its green color and
becomes marked here and there by reddish brown spots. At the
same time a fluffy growth develops on the under surface of the
leaf which becomes dry, yellowish brown and dead. At the last
stage of the disease some of the leaves became torn
vertically into threads near their tops only. A diseased leaf
is likely to be lighter and narrower than a healthy one.
Mycelium invades the stems also. On most varieties there are
more nodes in diseased canes. Diseased canes are often two
or three feet taller than healthy ones and witches' broom-like
growth resulting from the disease may weight tops to the

On maize and teosinte leaves show whitish yellow stripes
like those in cane, but not so pronounced. Conidia are
produced all over the plant instead of being restricted to
lower leaf surfaces. Growth was not checked by infection of
maize and teosinte but maize ripened and teosinte continued
to grow and seemed to outgrow the disease by the end of
August. Apparently the teosinte did not show infection until
August 10 while the disease swept over the maize field early
in July, thus accounting perhaps for difference in behavior
on the two hosts.

Oogonia were found in cane in December 1910 but could not
be found in either living or dead leaves from April to July of
1911. Oogonia 49-58 x 55-73 mu, oospores 40-50 mu in
diameter, wall 3.8-5 mu thick, in tissues of slightly
splitting leaves. Conidia 25-41 x 15-25 mu or elongate and
49-54 x 19-23 mu.

It may be noted that Weston (4I), when describing S.
north compared it with S. sacchari and stated that the"
oospores of S. sacchari are usually between 49 and 54.9 mu in
diameter and wall 5 to 8 mu thick. He also mentions ".......
the ooronial Sclerospora occurring on Saccharum spontftneum L.
in the Philippincs, a species very similar to S. sacchari but
perhaps separate front it."

Subramanian (26) found the conidia 18.5-45.1 x 13.2-
26.4 mu the average of 200 spores being 31.5 x 18.8 mu in
India on the single sugar cane plant found diseased. These
measurements agree reasonably well with the smaller of the
two types of conidia mentioned by Miyake.

Bibliography: (2, 3, 0o, 14, 16, 23, 26, 27, 35, 41, ).

-20 -

Name of disease, Downy mildew of sorghum.

Name of pathogen: Solerospora sorghi (Kulk.) Weston and Uppal.
Syns. Solerospora graminicola (Saoc.) Schroet.
in part
Solerospora graminicola var. Andropogonis
sorghi Kulk. ..

Hosts: Andropogon sorg Zea mys, Euohlaena mexioana. E. mexicana
has been inoculated successfully and it is thought likely a
downy mildew found on this host by Butler in 1905 was this
species (31).

Part attacked: Leaves.

Place of origin:

Country of first report: India (Bombay and Madras Presidencies), 1907.

First report from U. S.:

Present distributions India, Egypt, Tanganyika.

Factors affecting severity: According to Butler (5) it was noticed
in Madras that the disease is generally (though not always)
most severe in the wetter parts of fields. Presumably as in
other species of the genus, high humidity at night would be
required for production of conidia, but it has not been
demonstrated apparently that there is any appreciable spreading
of the disease by conidia.

Method of spread: So far as can be determined most of the spread is
through distribution of oospores and these are not produced on

Losses incurred: Losses have not been heavy in any case apparently.
This may be because infections are so nearly confined to those
from oospores, i.e., there is no great amount of spread from
plant to plant in the field. This species has been confused
with S. graminicola and data relating to it specifically and
unmistakably is incomplete. It is possible that with
different varieties of its host plants or under more favorable
humidity or other conditions it would be more destructive.

Comparison of losses: Data inadequate.

Controls No control measures would be required where corn was the
only host grown since oospores are not produced on corn
apparently and the disease would not live over from one season
to the next. On sorghum, rogueing, resistant varieties and
orop rotation should be effective.

- 21 -

Quarantine Action: This fungus would fall under the term "other
downy mildews" as used in the corn disease quarantine, No.

Description: According to Butler (5) seedlings of Andropogon
sorghum may show the disease very soon after they come up,
affected seedlings having pale yellow, narrow leaves,
covered on the lower or on both sides with the white downy
conidial stage of the fungus. In 5 or 6 weeks white streaks
appear on the upper leaves followed by shredding of the
tissues which turn brown from ooapores produced there.
Oospores may form in the upper part of the sheaths also. The
diseased seedlings are stunted and produce no ears.

When symptoms do not show on individual plants until
they are about two months old, the top leaves and the bases
of lower leaves turn white followed by browning when the
oospores are produced. On the lower leaves pale yellow
patches indicate the presence of the oonidial stage. Plants
of this type produce stunted ears if any. This is the
commonest and most prominent form of the disease.

When symptoms appear on groups of older plants, the
disease seems to spread from them, which is not true of the
seedlings or of individually infected older plants. On these
groups the leaves develop long narrow streaks and patches
which turn from pale yellow to orange and then brown.
Conidia form on both surfaces especially on the under side
but no oospores are produced. The patches appear to spread
from the lower to the upper leaves and from the tip to the
base of individual leaves. The whole leaf may turn brown but
there is no shredding. Normal ears are produced.

Uppal and Desai (3) state that the symptoms and general
effects of this downy mildew on the individual plants of
sorghum and maize were the same, as observed in the field.
When the plants were 5 weeks old, leaves of affected plants
were pale yellow and covered with the oonidial stage of the
fungus. However, the sorghum plants later showed shredding
while the corn plants did not. The latter continued to
produce conidia instead of changing to the production of

Conidia 18-32 x 16-23 mu according to Kulkarni (9, 42),
15-28.9 x 15-26.9 mu according to Weston and Uppal (l_,
germinating by production of germ tube or hyphae.

Oogonia similar to those of S. graminicola, oospores
25-42.9 mu in diameter, the majority 31-36.9 mu; wall 0.3-
4.3 mu, usually 1.1-2.7 mu thick (42).


Unlike S. gremin cola the formation of the oogonia
chiefly within elongate reddish discolored areas is followed
by marked disintegration of the leaf tissue into tangled
fibres. This stage does not occur in corn.

Bibliography: (5, ., 9., 13* 15. 2!*, 5, W) ).

- 23 -

Name of disease: Downy mildew.

Name of pathogen: Sclerospora spontanea Weston.

Hostsi Saccharum spontaneum, Zea M2s, Saccharum officinarum and,
by inoculation, Euchlaena luxurians, Miscanthus japonicus.

Part attacked: Leaves.

Origin: Philippine Islands.

Country of first reports Philippine Islands, 1921.

First report from U. S.s

Present distribution: Visayan group of the Philippine Islands, Siam.

Factors affecting severity: Not very well known but humid nights
would doubtless be necessary for maximum production of
oonidia as in other species* Hos+: association may be
important also. So far as kno'-n the disease cannot live
over on corn but lives over on the perennial Saccharum
spontaneum which is not severely injured. A few conidia
from S. spontaneum serve to start the disease on corn on
which abundant production of conidia may soon result in an
epidemic on the corn. S. spontaneum is said to be susceptible
in the seedling stage

Methods of spread: Local spread during the growing season is by air
borne conidia. There is an undetermined species of
Sclerospora which produces abundant oospores on S. spontaneum
in the Philippines and which might belong to this fungus. If
oospores are produced on this or same other host, they would
serve to spread the disease as in other Sclerosporas.

Since the disease persists year after year in clumps of
the perennial S. spontaneum, movement of living parts of this
host might spread the disease.

Losses incurred: Said to be as destructive on corn as S. philip-
pinenss which causes losses up to 50% or more of the crop.
Little damage found on S. spontaneum. Inadequate information
with respect to other hosts.

Comparative losses :

Control methods Since the disease is not carried over on corn
apparently, eradication of perennial hosts might eliminate
the disease. If oospores produced on other hosts are a stage
of this fungus, it might be desirable to rotate crops to


eliminate them from the soil before planting corn on the
Sam-, .*

Quarantine action This disease would be included under the term
Mother downy mildews* as used in the corn disease quarantine,
No. 24.

Description: The symptoms and destructiveness of this disease on
corn are said to be the same as those of S. philippinensis
(35). S. spontaneum is very resistant anxd even though
heavily infected shows only slight striping of the leaves,
remains undeformed and is not materially retarded in
development. Infected plants tiller and produce dense
clumps on which the downy mildew persists year after year.

Conidia 25-64.9 x 11-20.9 mu, usually 39-45 x 15-17 mu
(37). Germination by formation of a germ tube.

Oogonia and oospores not known. Oogonia are commonly
found in the Philippines on S. spontaneum, offioinarum, and
Miaoanthus japonious, but have not been coneoted with
conid--a forms. The oogonia on all three hosts are so
nearly alike that they may belong to one species.

S. spontanea is the first conidial species of
Solerospora to be found on a wild host. Infected plants from
which the tops have been removed will produce new growth in
which the fungus persists and produces conidia.

Bibliograh: (j, 24, L5, 37, 38, 41).

- 25 -


Sclerospora sp. on maize in South Africa reported by Storey and
McClean. Material of this fungus was examined by Dr. Weston who
states in correspondence that it agrees very closely with S. maydis
and S sorghi as they occur on corn. (Bibliography (1, I, 7
25).- -

'Solerospora madis Butler" reported by Lobik as attacking corn in
Crimea. The on al measurements given, 17-28.8 x 11.4-15.2 mu,
fit those of S. graminicola and S. maydis (Rac.) Palm fairly well.
Presumably it-is noM graminioola because the illustration shows
no papillae of dehiscence at the apex of the conidia. S. maydis
Butler is now S. philippinensia Weston which has far larger conidia.
Bibliographys (iLT.

Sclerospora sp. was reported on corn and sorghum in Uganda by Small
who said the oospores were only half the size of those of the downy
mildew in India (S. gram inicola and S. sorghi) which would seem to
preclude placing the fungus in any species for which the oospores
have been described. Oospores were reported as occurring in sorghum
but not in corn. Bibliography: (21, 22).

Solerospora sp. on cultivated sugarcane in Fiji reported by Weston
on the basis of correspondence with Mr. D. S. North as apparently
distinct from S. sacchari as it does not cause elongation of the
shoots, rarely--shows oonidial stage and produces more oogonia and
leaf splitting. Bibliography: (41).

Solerospora spe on sugarcane leaves in Formosa, India, Siam Queens-
land. On Sacoharum spontaneum, Philippine Islands, Siam. Listed by
Stevenson and and

Sclerosaora sp. on corn in Tanganyika. S. sorghi is reported on
sorghum. The fungus on corn may be that species also.
Bibliography, (W).

Solerospora sp. or spp. on Saccharum spontaneum, S. officinarum,
and Miscanthus in the Philippines. Weston (3 p680) calls atten-
tion to the fact that oogonia on these three-hosts, and no, yet
connected with any conidial form, are so nearly alike they may be
one species. However, the oogonia of S. graminicola and S. sorghi
are quite similar and it is possible the oogonia of both S.
philippinensis and S. spontanea will be found in the undetermined
oogonial forms on one or more of these hosts.

Bibliography: (37, these may be included in whole or in part in 23

Spore measurements of Sclerosporas of corn, sugarcane, and rice.

Species ..'.Conidia -__Oospores
S. graminioola 19 31 x 12 21 mu--Butler (5) 22.5 35 mu diameter, average
Scorn et al 11 35 x 10 21 mu, usually l6 22 x 12 l6 mu -- 32mu--Butler (5)
Weston (59) 25 46.9 mu, mostly29 l 41. --
15 28.9 x 3 22.9 mu, usually 17 22.9 x 15 Weston and Uppal (.)
16.9 mu--Wes ton and Uppal (142)
S. maorospora 60 70 x 38 52 mu--Peglion (18) 60 65 mu diameter --Saccardo
corn, rice, et al ,
S. maydis 19 26 x 15 20 mu--Palm (17)
corn 17.5 27.5 x 13-75 17.5 mu--Steyaert (2)
S. sorghl 18 32 x 16 23 mu--Kulkarni (9) 25 142.9 mu diameter--Weston and
corn, et al 15 28.9 x 15 26.9 mu, usually 19 24.9 x 19- Uppal (42)
22.9 mu--Weston and Uppal (12)
S. miscanthi Said to be similar to S. saechari (16) 4 0 55 mu diameter--Miyake (16)
sugarcane, et al usually 47 48.9 mu--Westoan TI)
S. spontanea 25- 64.9 x 11 20.9mu, usually 39- 45 x 15 -
S(sugarcane, et al)' 17 mu--Weston (7)
S. philippinensis 17 52.9 x 11 24.9 mu, usually 27 39 x 17 -
Sorn, et al 21 mu--Weston (35)
28 45 x 16 22 mu--Butler (5)
S. sacchari 25 41 x 15- 23 mu or 40 50 mu diameter, wall 3.8 -
Scorn, sugarcane 49 54 x 19 23 mu--Miyake (16) 5 mu--Miyake (16)
18.5 45.1 x 13.2 26.4 mu--ubramaniam (26) usually 49 54.9 mu, wall 5 8 mu
--Weston (41)



(1) Anonymous
1924 Departmental Activities: Botany. Journ. Dept. Agr.
S. Africa 8, 452-454. (Abstr. R.A.M. 4, 24. 1925)
Sclerospora sp. reported for the first time in the Natal
coast belt in 1923.

(2) Anonymous
1929 Bureau of Sugar Experiment Stations; Queensland Agric.
Journ. 32: 4-7.
Sclerospora sacchari destructive on some canes. Found
in 5 of 71 plantings surveyed in Giru district in April 1929.

(3) Bell, Arthur F.
1929 A Key for the Field Identification of Sugar Cane Diseases.
(See Bul. No. 2, Queensland Bureau of Sugar Exp. Stas., pp. 7-653,
(43) pls. 17.
also) pp. 31-32, Downy Mildew
Alternative names Leaf stripe, leaf splitting disease,
solerospora disease.
Causal agent Slerospora sacchari Miy.
Diagnostic characters, transmission & control discussed.

(4) Bottcmley, A. M. and Doidge, E. M.
1929 Maize diseases in South Africa. Pan-African Agric. and
Veterinary Conf. Pretoria, Aug. 1 17, 1929. Agric. Sect.
2, 235-237. (Paper 46).
Solerospora maydis (Rao.) Butl. of minor Importance in
the Unio. Occurs all along the Natal coast and in isolated
localities in the Transvaal. Note. S. madi (Rao.) Butler
is now a synonym of S. philippinensis Weston, but the identity
of the fungus noted Ts not yet known with certainty.

(5) Butler, E. J.
1918 Fungi and Disease in Plants. 547 -p.p 206 figs.
Solerospora graminicola on Pennisetum typhoideum and S.
sorghi (under its synonym S. grami oola var. andropogonis-
aornl!) an sorghum discussed rather fully, both fungi and
disease e symptoms.
Sclerospora philippinensis (under the name S. maydis
(Rac.) Butler) on maize is discussed and pictured also

(6) Butler, E. J.
1913 The downy mildew of maize. Memoirs Dept. Agr. India, Bot.
Ser. 51 275-280, May, 1913.
Solerospora ph1ipp inensis discussed under the name S.
maydis (Rao.) Butl. as he thought it the fungus described-as
Peronospora maydis by Raciborski.

(7) Doidge, E. M. and Bottomley, A. M.
1951 A revised list of plant diseases occurring in South
Africa. Mem. Bot. Surv. So. Africa No. 11. 78 pp.

- 28 -

"Sclerospora maydis (Raeo.) Butl." on corn along the
Natal coast and in the Transvaal. Usually unimportant.
(This is the undetermined species discussed by Storey and
S. graminicola on Johnson grass, Sudan grass, sorghum,
and Slerospora (?) 1graminicola on Eragrostis spp.

(8) Jones, G. Howard
1934 Egyptian plant diseases: a Summary of Research and
or 5 Control. Tech. and Scientific Service (Mycological Sect.)
Bul. No. 146, pt. 2 pp. 9-41, List of Diseases of Crop
Plants. (Not dated apparently)
Reports S. graMinicola on corn (p. 24) and sorghum
(p. 26) but it seems likely S. sorghi is referred to.

(9) Kulkarni, G. S.
1913 Observations on the downy mildew (Sclerospora
graminicola (Saoc.) Schroet. of Bajra and Jowar. Mem.
Dept. Agric. in India 5: 268-273. 2 pl. May.
Separates form on sorghum as S. graminicola var.
Andropogonis sorghi because conidia germinate by production
of germ tubes instead of zoospores as in the species proper.
Note: Bajra Pennisetum typhoideum and Jowar sorghum.

(10) Lee, H. A. and Medalla, M. G.
1921 Leaf Stripe Disease of Sugar-cane in the Philippines.
Science, N. S. 54: 274-5,
Sclerospora sacchari found on sugar-cane imported from
Formosa. Eradication being attempted.

(11) Lobik, A. I.
1933 Present position of the problem of the diseases and
injuries affecting maize in N. Caucasus. Bull. N. Caucasiah
Inst. for Plant Protection I (VIII) 2. pp. 3-51, 2 pl.,
bibliog. 1931 (in Russian) (Abstr. R.A.M. 12: 505-6, 1933)
This paper lists Sclerospora maydis Butler as occurring
on corn in Crimea, gives the symptoms briefly and the
measurements of the conidia, 17-28.8 x 11.4-15.2 mu.
Oospores are not mentioned and drawings show no papillae of
dehiscence so the species can hardly be S. graminicola but
the conidia measurements seem to preclude S. philippinensis
of which S. maydis Butler is a synonym.

(12) Mackie, W. W.
1930 Sclerospora macrocarpa in barley. Phytopath. 20- 107.
Barley in California found infected. Note.- The
Erroneous use of macrocarpa for macrospora in the federal
quarantine (Rice quarantine No. 55) and elsewhere is


(13) MoRae, W.
1931. Report of the Imperial Myoologist. Sci. Repts.
Imper. Inst. Agric. Res., Pusa. 1932-33, pp. 134-160.
A Sclerospora agreeing with S. sorghi was found on
Panioum trypheron, first report on host.

(l4) MoRae, W.
1932 Report of the Imperial Mycologist. Imper. Inst. Agric.
Res., Pusa. 1930-31, pp. 73-86.
Reports occurrence only, of Sclerospora sacchari on
cane, maize, and Euohlaena luxurians in India*'-

(15) Melchers, L. E.
1931 Downy mildew of Sorghum and maize in Egypt. Phyto-
path. 21t 239-240. (Feb.) (Abstract in Rev. Appl. Mycol.
lo0 4I9. 1931)
Oospores of Egyptian material (S. orhi) were studied
by Dr. Weston. Variable but most close ely resembles
specimens franom Kirkee, India, rather than fram Poona, India,
where Kulkarni established this species as a variety of S.

(16) Miyake, Tsutane
1912 On a fungus disease of sugar cane caused by a new
parasitic fungus, Sclerospora sacohari T. Miy. Bul.Div.
Path., Sugar Exp. Sta. Formosa No. 1. 61 pp. Dec. 1911
(Transle by Mr. Hirode & Dr. D. S. North in Library files).
(Bull. printed Mar. 28 and published Mar. 30, 1912).
A copy of the original, in Japanese, and a copy of the
translation made from a copy loaned to Dr. Weston by Dr. H.
L. Lyon of Hawaii who received it fran Dr. North, both are
in the U. S. Dept. of Agr. library and were consulted in
preparing notes.

Information regarding S. miscanthi is found on p. 21
of the translation and p. 27 has a note said to have been
added in July, 1913, saying that the oonidial stage had
been found recently and closely resembled that of S.
sacchari and that the species had been named S. miscanthi
T. Miyke. *

(17) Palm, Bjorn
1918 Onderzockingen over der omo lyer von de mais. Dept.
Landb. Nivj. en Handel (Dutch East Indies), Meded. Lab.
Plantenziekten, No. 32, 78 p., 8 pl. English summary, p.
55-57. Literatuurlijst, p. 78.
Describes Sclerospora javanioa Palm now a synonym of
S. maydis (Rac.) TPalm.

- 30 -

(18) Peglion, V.
1930 La formazione del conidi e la germinazione delle
oospore della 'Sclerospora macrospora' Sacc. Bol. R. Staz.
Pat. Veg., N. S. 101 153-164. (Abstract in Rev. Appl.
Mycol. 10: 174-5. 1931.)
Symptoms given for disease on wheat and Phragmites
ommuunis (said to be a constant source of inoulum). Conidia
found on Holcus lunatus are papillate, 60-70 x 38-52 mu on
short peduncles from mycelium. Part of oospores germinate
after 15-20 days in moist chamber at temperatures not exceed-
ing 18 C. forming a large macroconidium which at maturity is
75-80 x 55-60 mu and usually germinates by production of

(19) Peyronel, B.
1929 Gli zoosporangia nella Sclerospora macrospora. Boll. R.
Staz. Pat. Veg. N. S. 9f 353-357* (Abstract in Rev* Appl.
Mycol. 9t 513, 1930.)
Conidia obtained on bits of infected wheat oulms and
leaves in water, emerging in groups through stomata the guard
cells of which constrict bases making them easily detached.
Production of short duration, from very young actively growing
mycelium which had not produced zoospores. Conidia germinate
by production of zoospores which soon lose cilia and round up.
This species unique in the genus in forming its conidiophores
in water instead of air.

(20) Raciborski, Maryan
1897 Leijer, Eine Gefahrliche Maiskrankheit. Ber Deut. Bot.
Gesell. 152 475-478. 1897.
Describes Peronospora maydis Rao. now known as Sclerospora
maydis (Rac.) Palm.

(21) Small, W.
1922 Ann. Rept. of the Gov't. Mycologist for 1921 in Ann. Rept.
Dept. Agric. Uganda for year ending Dec. 31, 1921. pp. L9-57.
(Abstract in Rev. Appl. Mycol. 2: 156. 1923.)
On page 52 a downy mildew of sorghum is reported with
oospores said to be only half the size of those of the fungus
which induces the same disease in India.

(22) Small, W.
1922 Diseases of Cereals in Uganda. Dept. of Agric. Uganda,
Circ. No. 8, pp. 1-27.
Solerospora sp. on sorghum (pp. 5-6) and on corn (pp. 9-
10), both conidia and oospores found on sorghum but conidia
are not described and it is not stated to be the same species
on both hosts. The fungus on corn was not studied, determina-
tion being based on symptoms.

- 31 -

(23) Stevenson, John A. and Rands, R. D.
1938 An annotated list of the fungi and bacteria associated
with sugarcane and its products. The Hawaiian Planters'
Record L2: 247-313. 1938.
Sclerosporas on pp. 304-305, include S. raminicola,
S. miscanthi, S. philippinensis, S. sacchari, an S.
spontanea, also Sclerospora sp. on leaves of cane in Formosa,
India, Siam, Queensland, and on Saccharum spontaneum in
Philippine Islands, Siam.

(24) Steyaert, R. L.
1937 Presence du Sclerospora maydis (Rac.) Palm (S. javanica
Palm) au Congo beige. Scientific bull. No. 13 of the I.N.E.
A.C. (L'Institut National Pour L'Etude Agronomique du Conro
Discussion of Sclerospora spp. on corn, additional
hosts, distribution, etc., and assignment of downy mildew
found in the Belgian Congo to S. maydis, on basis of symptoms
measurements, etc. Discussion of other Solerosporas in

(25) Storey, H. H. and McClean, A. P. D.
1950 A note upon the conidial Sclerospora of maize in South
Africa. Phytopath. 20: 107-8.
Sclerospora sp. on corn, never determined, though
material was studied by Dr. "'Aeston.

(26) Subramaniam, L. S.
1931 A note on the downy mildew of sugarcane in India.
Agriculture and Live-Stock in India, Vol. 1, pt. 1, pp. 52-
33, pls. 5 and 6. Jan. 1931 (Calcutta). (Published for
the Imperial Council of Agric. Research.) Plate 5 is
colored showing symptoms on cane leaf and pi. 6 shows
details of conidia, etc. The disease was found on one cane
plant in 1930 at Pusa. Inoculations were tried on cane,
maize, sorghum, Pennisetum typhoideum, Eleusine coracana,
Euchlaena and Setaria italica, maize being the onlypossible
host to become infected. All plants destroyed apparently
and disease eliminated. A detailed study of the organism
was made, based on material from the one infected cane
Said to be Sclerospora sacchari.

(27) Swingle, Walter T.
1916 In a letter to Dr. C. L. Marlatt, dated February 29,
1916 Dr. Swingle says "...... in February, 1916, Mr. S.
Kanecko, Agriculturist of the Sugar Experiment Station at
Daimokko, Formosa, informed me that the disease has sub-
sequently proven to be very bad on corn, in some cases
destroying the crop entirely, and that the Formosan Govern-
ment has prohibited the growth of corn in the vicinity of 0404'

- 52 -

fields." The disease referred to is Solerospora
saccharin as described from Formosa by T. Miyake.

(28) Takasugi, H. and Akaishi, Y.
1933 Studies of the downy mildew (Solerospora graminicola
(Sacc.) var.. setariae-italicae Traverso) on Italian millet
in Manchuria. I. About the germination of oospores.
S. Manchuria Ry. Co. Agric. Exp. Stat. Res. Bull. Il,
pp. 1-20, 8 pl. 19533. (Japanese with English abstract.
Abstract in Exp. Sta. Rec. 70: 489-490. 19534 and in Rev.
Appl. Mycol. 153, 4356. July, 1934.)
Field investigations 1927-'29 in 15 districts in
Manchuria showed 10 to 25% damage to Setaria italica by
Sclerospora graminicola, oospores of which remain viable
for over eight years.

(29) Takasugi, H.
19532- Additional list of the fungi of Manchuko. Trans.
Sapporo Nat. Hist. 13: 185-190. 19534. (Abstract in Rev.
Appl. Mycol. 13: 804. Dec., 1934).
Rice was attacked by Sclerospora oryzae Brizi.
(usually referred to as S. maorospor Saco.J

(50) Uppal, B. N. and Weston, W. H., Jr.
1956 The basis for merging Sclerospora indica with S.
philippinensis. Indian J. Agr. Sci. 6, 715-719. (Abstract
in Rev. Appl. Mycol. 15: 794-5. Dec. 1936)
Comparison of material on corn shows such slight
differences S. indioa is reduced to a synonym of S.
philippinens-s. Six- percent of the Indian conifia were
3355-44 mulong and 65% of the Philippine conidia were 531-59
mu long. Width frequencies overlap mostly but S. indica
has a tendency to be slightly narrower.

(51) Uppal, B. N. and Desai, M. K.
1952 Two new hosts of the downy mildew of sorghum in
Bombay. Phytopath. 22: 587-594. Illustr. June, 1952.
Euchlaena mexicana and different varieties of corn were
successfully inoculated using oospores of Sclerospora
sorghi from sorghum. Only 6.8% of plants of Philippine corn
became infected as compared to 534.4g of Golden Bantam.
Conidia 15-28.9 x 15-26.9 mu on both corn and sorghum with
slight variations in numbers in size groups. Disease occurs
naturally on corn as well as sorghum in Bombay. Oospore
production on sorghum only. Authors believe the downy
mildew seen by Butler on I. mexioana at Poona in 1905 was
S. sorghi instead of S. g raminieoa since latter does not
Tnfect teosinte apparently.

-33 -

(32) Van Hall, C. J. J.
1921 Ziekten en plagen der culturgewassen in Nederlandsoh -
Indie in 1920. Meded van het Inst. voor Plantenziekten 46,
50 pp. (Abstr. R.A.M. 1, 18-20, 1922)
Outbreaks of "yellow disease" of maize due to Solerospora
javanica serious in some localities damage estimated at 30
to 509 of crop. S. javanica is now a synonym of S. maydis.

(33) Wallace, G. B.
1933 Report of the Mycologist. Ann. Rept. Dept. Agric.
Tanganyika Territory 1932, pp. 76-80. 1933. (Abstract in
Fev. Appl. Mycol. 12t 552. 1933)
Sclerospora sp. caused considerable damage to sorghum,
9.6, 5.9a 10.8 and 10.7 percent infection on four varieties in
trial grounds, another variety was practically immune.

(34) Wallace, G. B.
1937 A revised list of plant diseases in Tanganyika Territory.
East African Agric. Journ. 2t 305-310. Ja. No. 4.
Scleroapora sp. reported on corn, S. sorghi on sorghum.

(35) Weston, W. H., Jr.
1920 Philippine downy mildew of maize. Journ. Agr. Res. 19:
97-122. 12 pls. (2 col.) May 1, 1920.
Destructiveness, symptoms, hosts, and detailed study of
the pathogen, here named Sclerospora philippinensis.

(36) Weston, W. H., Jr.
1921 The occurrence of wheat downy mildew in the United States.
U. S. Dept. Agric. Circ. 186. June, 1921.
Sclerospora macrospora found in Tennessee and Kentucky in
1921 and herbarium specimens show it was collected in California
in 1919. Found on Bromus c ommutatus as well as wheat.

(7) Weston, W. H., Jr.
1921 Another conidial Sclerospora of Philippine maize. Journ.
Agr. Res. 20: 669-684.
Downy mildew which attacks Saccharum spontaneum and corn
especially is described as S. spontanea. Symptoms said to be
similar to those of S. philippinensis as given by Weston in
paper on Philippine downy mildew of maize.
Spore measurements of the two species, based on measure-
ments of 700 spores, are analyzed. The bulk of the spores of
S. philippinensis fall in groups 31 to 56.9 mu in length and
T to 18.9 mu in width, those of S. pontanea in the groups
37 to 46.9 mu in length and 15 to 16.9 mu in width. The spores
of S. philippinensis are usually 1.55 to 2.14 times as long as
they are wide and S. spontanea 2.35 to 2.94 times as long as
wide. As few as 200 spore measurements give the same ratios.

- 34 -

(38) Weston, W. H., Jr.
1923 Production and dispersal of oonidia in the Philippine
Sclerosporas of maize. Journ. Agr. Res. 23s 239-278, 10
plates., Jan. 27, 1923.
Discussion of the nocturnal production and dispersal
of conidia of Sclerospora philippinensis and S. spontanea.
S. philippinensis produced from 758,033,L400 to 5,946,069,600oo
conidia per corn plant during one night. Production of
conidia may continue for weeks, up to two months or more.
Conidia responsible for spread locally but oospores
probably means of distribution to new and distant areas.

(39) Weston, W. H., Jr.
1924 Nocturnal production of conidia by Sclerospora
graminicola. Journ. Agr. Res. 271 771-78L I 2 pls March
Bs 1924.
Studies made on Setaria viridis found naturally
infected in Minnesota and somofplants transferred to
Washington, D. C. and studies continued. Nocturnal produc-
tion of oonidia established, and development of conidio-
phores and conidia and their structures studied. Conidia
11-35 x 10-21 mu, usually 16-22 x 12-16 mu. Drawings in
plates show various stages of development of conidiophores
and conidia.

(h40) Weston, W. H., Jr. and Weber, Geo. F.
1928 Downy mildew (Sclerospora graminioola) on Everglade
millet in Florida. Journ. Agr. Res. 6: 935-963. 2
plates. June 1, 1928.
Sclerospora graminioola was found on Chaetochloa magna
( Setara maa) or Everglademillet in Florida 1922.
This host is indigenous, perennial and common on low ground
in Florida. Photomicrographs of oospores, also other
figures shown. Discussion of disease, of organism, and of
importance. Conidia 13-36.9 x 11-24.9 mu, usually 15-27 x
13-21 mu; oospores 19-45 mu, usually 27v39 mu, a majority
30-36 mu.

(41) Weston, W. H., Jr.
1929 A new Sclerospora from Fiji. Phytopath. 19: 961 -
967. Oct. 1929.
Described S. north which attacks Erianthus maximus
var. Seemanni causing shredding of leaves similar to
effects of formation of oogonia in sugarcane attacked by
S. sacchari, in Miscanthus by S. misoanthi and in Setaria
2hctetochoa.) by S. graminicol. Conidia not knomn.
In discussing relationship and characters of
Sclerosporas on members of the tribe Andropogoneae casts
doubt on validity of S. miscanthi, S. sacchari, and S.
spontanea as distinct species.

55 -

States that Mr. D. S. North reports a leaf-splitting
disease of "Veico", a wild cane (probably Saccharum
spontaneum), fungus perhaps S. spontanea. Also Sclerospora
sp. on cultivated cane, formerly assumed to be S. saccharin
but now thought by North to be distinct as it does not
cause elongation of the shoots, rarely shows the downy
conidial phase, and produces oospores more readily,
accompanied by more leaf splitting.

(142) Weston, W. H., Jr., and Uppal, B. N.
1952 The basis for Sclerospora sorghi as a species.
Phytopath. 22: 573-586. June, 1932.
Detailed study of measurements of conidia and oospores
of S* sorghi on sorghum and S. graminicola on Pennisetum
typhoideum, structural and physiological distinctions
discussed, drawings.

(43) Bell, Arthur F.
1939 Report of the Division of Entomology and Pathology.
in Thirty-ninth Ann. Rept., pp. h5-59. Queensland Bur.
Sugar Expt. Stas. (Australia). 1939.
(NOTE. This article was received after the Sclerospora
material had been prepared for reproduction. The data
presented are in marked contrast with that previously
available from Australia.)
"Downy mildew at present constitutes the chief
sugar-cane disease problem in that State, and is, to a
considerable extent, a limiting factor in the control of
other diseases." (p. 56)
"Field observations over the past two years have
strongly suggested the possibility that maize grown in
the vicinity of oanefields has been responsible for the
spread of outbreaks of downy mildew, if not for their
initiation." (p. 57)
In a test of possible downy mildew hosts, inter-
planted with downy mildew diseased sugar-cane, all three
varieties of Zea Mays "rapidly became heavily infected
and produced spores in qu&anitity from both surfaces of
leaves. Leaf streaks were readily visible on all sor-
ghums, but no visible dovwny mildew was produced; on
only one occasion were a few spores scraped from the
leaves of Natal 6, but nothing from the other varieties.
A few odd leaf streaks and a few spores and sporophores
were observed on Johnson grass on one occasion, a few
leaf streaks but no spores on Soudan grass, and no
symptoms or spores on the remainder. Sugar cane was

- 36-

reinfeoted by the exposure of freshly-cut setts of
the variety P.O.J. beneath the leaves of diseased
The results of this trial and current field
observations have indicated that maize is readily
infected with sugar-cane downy mildew, that infection
weeps through the maize in the course of a very few
weeks, and that the disease produces a marked stunt-
ing of plant and cobs. The ultimate course of the
fungus in the maize plant has not yet been determined,
but it is obvious that planting of corn in the
vicinity of sugar-cane, in the presence of downy
mildew, must be condemned."
The corn and sorghum varieties tested are listed
as "(a) Zea mays L.o 3 varieties Imperial Yellow
Dent, Funks 90-Day, and Reid's Yellow Dent. (b)
Soru app. Snow. a 3 varieties Natal 6, Wheat-
land Milo, and American Early Red."
Minimum temperature for sporulation is about
16 Co., maximum about 31 C. with no well defined
optimum, in tests made. Daily exposure to sunlight
seemed to be necessary to produce daily sporulation.


Bvorglade millet infected with S. &roxinicola (left) and healthy (right).
fterglade millet stunted by long standing systemic infection.
Shredding of tops following formation of oospores.
Infected head largely transformed into a mass of elongated bracts*
F, and G, Oospores as seen at different magnificoations G treated to
bring out structure.

(From Jour. Agr. Ros. 361 935-963. June, 1928. Plate 2)



74i i:: ^ ^ I / ^ ^ ( T
U 'V
I/ \-/ pt M & I \ v




1 3 28 491

A. --S. graminioola on Pennisetum typhoideun, 1-4 oonidiophores, 5-7 oonidia showing
p-plae rough Aih i oospores emerge at germination.
B. -S. sorghi on sorghum, 1-4 and 8-10 oonidiophores, 5-7 oonidia, showing that
gerSeon is by formation of hyphae.

(From Phytopath. 22t 573-586. June, 1932. Plate 1.)

Solerospora spp.

Plate 3 S. maydis





1c _
M' -

9 /ON


A.-Sterigmata bearing oonidia.
C, D.-Germination of a oonidia.
E.-Conidiophore with oonidia beginning to form.
F.-Poorly developed late conidiophore before formation of
oonidia. G--Fully developed oonidiophore prior to dehis-
oenoe of oonidia. H.--Conidiophore from whioh oonidia
have begun to dehisoe. I, J.-Septation of basal cells.

(From Publ. Inst. Nat. Etude Agron. Congo Beige Ser. Scient.
No. 13. 1937, Plate, page 14.)

8olerospora app.

Plate 4 5. hilippliznoie-

Young planets of Guam Uhite Dent mies, the two on the right
showing ohiorotie condition oaused by 8. philippinensi. Ti.
plants are 31 day. old and developed symptoms of the diaso
25 days after emerging from the soil.

(From Jour. Agr. Reo. 191 97-122. May, 1920. Plate B)

Solerospora spp.

Plate 5 S* philippinensis



0 0 0
4> w

14 0
^~ tCi ( I=J

0 4'
5 4 e 0i

*- ^ 0

*A I%94445

m 00
"\. fl 0 6900
6 1^:0

Solerospora sp.

Plate 6 S. philippinensis










i -4

00 0






A and. B. Etiolated markings due to jS..philippinensin on maize -natural size,
C, D, and E. Douny growth of conidiophores of So philippinensis on maize leaves
(C & Dj and sheath (9).


A and B. Btiolated marking due to S. ph4l4ppinesis on maize natural size.
C, D, and E. Downy growtho ondih of phS lippinensi8 on maize leaves

(From Jour. AgTro Res. 23s 239-278. Jan. 27, 1923. Plate 4)

Solerospora app,

Plate 8 Soleropora (spoie not given)

A A. Two young maisze plants
(Guam'White Flint) 10 days
after emerging; the smaller
and nearer one, healthy;
the larger one already
infected and showing (at a)
the etiolated conidiophore-
bearing areas characteristic
of the dowmy mildew.

B. The same plants about a
month later. The conidio-
l phore-bearing area which was
inconspicuous and occupied
only a few square centimeters
on the leaves of the young
plant is now very extensive
and conspicuous and supports
the production of vast
numbers of conidia each
favorable night. The meter
stiok, which is the same as
that shown in A, is marked
off in 5-cm. divisions.

(From Four. Agr. Res. 23: 239-278. Jan. 1923. Plate 2)

Solerospora sp.

S. apontanea

Plate 9









4 4


U (0
o ai







^, sl'


0 0


o a




*n 0



0 vo

o bo e

(00 14
0 .
10 14-)
0S *0 .0

14> IS~
o ,o.

*d -*q
0 46 r4
0 0t

40 C

Solerospora spp.

Plate 10 S. spontanea and S. philippinensis




Urj= otd.

\ 1 A'^'


* 0
Q 0 wQ

1P 0 0

o fp it

f- K 0 0

0~- "q0 -
40 ^ c-44
'o M4)C.rt 0
0 4* -1 9 Q

F^ *O S 4)


a 00

I, 33 g g

IH -r
*P 0 1< 0 4-)a

0 g9

P ,tgo 0
a 1 4 M. 00
9 Nn (d -I^ H4
^0 bad*o4

:3 "4 -p 0 0
*O 4- ) to co a









Solerospora app.

Plate 11 S8 .pontano

A.-Typioal and B
f terminating while
D# E, and 0 from
I, J L-K.-Typioal
S. apontaneum and

poorly developed oonidiophoreu. C.--Conidia
still attached* D-H.--Typioal basal portions
Saooharum spontaneumj F and H from augaroeane).
oonidia, some germinating (I from maizes, J from
K from sugaroane).

(From Jour. Agr. Re. 20& 669-684. Feb. 1921. Plate 79)

Solerospora app.
Plate 12 S. uaoohari after Mlyake (No translation of legend available)

I 7

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