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POTATO WITT CAUSED BY FUSARIUK OXYSFORUM.

Thesis for tne Degree of Master of Science,

Michigan Agricultural College.

he?

Robert W. Goss

June

1915.
 

~~

THESI-
*

TABLE OF CONTE: TS.

History ----<------------- eer cree -- ercrero-e ---fp 1
Geograpnic distrivution,------- mec cr ere e rene -- 13
Economic: Imvportance--------- eoewere eee aorene 16
Field obeervations ~~ ----<----- wens ecee creer 19
Descrivtion of alc eage.-- - erence eennn- ccce--- 35
Btiology crvrcrccccr-e--- wer mmm reer eter err e-ee - 45
Patnogenicity ----------------- eer ccesceceee-- | (45
MOTOg LOBYyY wen - one eee ---- wee ener ee -------- 46
Cuttural s tudleas----------- were cece r nee eee-- o-- 54
Spore germination studies ------- eeceeeeeee--= ) (77
Maximum and iilninum Zrowtn, -e-escse-- eee wn -ne- C1
Toeral deata point, ----e-+-------------------- G4
Polsonous binroducsvs ot tue Tungus e--2------- ~ &5
Infection exneriments, ---------<------------- - &&
Control - «----2-------------------- ewww eenwee 103
Experiment witn intected tuvers. ---------e-enn-- 105
2eSts WIth Neil aAlsa eeneerseowowenne ween ee ene--110
Eftect of tungicid:.] econo eee een n-ne --e- eee - lil
WeEdL@ LOrm@lAae@ snc ennn- meen - - mew ee we wen eene 116
Literature, wee e ee eee---- wee ween e-e-ee e--- 119.

96428
POTATO WILT CAUSED BY FUSARIUM OXYSPORUM

HREKKKHKKKE

HISTORY.

The Fusarium wilt of potatoes was probably
present in this country for many years beiore the cause of
tne wilt was determined, The tirst note of the patnol ogical
condition caused by thia disease in this country dates only
as far back ae 1695 when G.P. Ciinton reported the disease
in Illinois. Since that time it nas been widely observed but
until recent years it has probably been more or less contused
with the other wilts of the potato, In most cases simply tne
presence of the condition caused by the organism: wae noted
and very little attempt was made to determine the cause of
thie pathological condition. It was not until about 1904
that the disease came into prominence, when it tirst assumed
economic importance in this country. At tnis time there
appeared a bulletin py Smith and Swingle (1904) describing
Fusarium oxysporum as the cause of the wiit of potatoes
noted in Miecnigan ard the District ot Columbia.

nO important epidemic periods or epocha in
tne nistory of the dieeagse are found; this is probably owing
to tne slow and insidious nature of the irfection of tne

potato crop, not caueing a rapid rot of the plants but slowly
 

 

 
undermining tue seed stock and gradually decreasing the
yield.

Very little work was done on the disease in
this country after 1904, until a widespread occurrence of
the disease wae reported in California in 1908, which was
studied vy Orton (1909), wno also satudied tne diseases of
potatoes in various parts of the country in 1909 and 1910
and abroad in 1911. He found Fusarium wilt to be very wide-
epread in America but not recognized in Burope. Since that
time very valuble work nas been done by Dr. Wollenvweper,
especially on the morphology and classification of this
especies of Fusarium, and inoculation exrerimentsa nave been
conducted by Manns in Onio,

The diseare was first noted in Micuigan in
1899, (Smith and Swingle 1904) and since that time very little
has been done with the disease in this state. It was reported
by G.H. Coons (1914) and was studied py the writer in various
parts of the state during the past season and found to be of
widespread occurrence, and while strictly speaking it has
not caused an epidemic as yet in thie atate it is certainly

assuming great economic importance.

PREVICUS WORK.
The literature on the taxonomy of the genus

Fusarium has been in a very cnaotic etate until recent years,
3.

‘and necessarily that part of the literature in reference to
the pathological conditions caused by these organisms has
been in no better condition.

In regard to Fusarium oxysporum in particular,
tne literature nas been very corfusing, principally because
no reliable cultural and morphological studies and inoculation
experiments have been conducted with reference to the path-
Ological conditions noted in the field.

Fusarium oxysporum had long been regarded as
tne cause of the dry rot of potatoes, even up to 1904 wnen
Smith and Swingle 1.c. wrote on the suodject. In tueir bulietin
tne authors describe a species of Fusarium. which they identity
witn te Fusarium oxysporum of Schlechtendal (1824) and
wnich they report as causing a dry rot as weil as the wilt of
the potato vlant. No inoculation experiments were made and it
ie very probable that they were working with more than one
species, in the Lignt of tue recent ctudies of Wotlenwevber
wno hae shown that F. oxysporum is a vascular varasite causing
wilt and wintering over in the atem enda of tne tubers but
not producing a decay of tne tuber.

Wilcox in 1912,(Wilcox, Tink and Pool 1912, )
working with a Fusarium causing the dry rot of the tuber
compared his epecies with that which Smith sent him as
F. oxysporum and found that the two were not identical. The

F. oxyeporum caused a wilt but not a decay, while his species
which he calles F. tuberivorum (sp. n. Wilcox and Link) was
a saprophyte incapable of infecting any part of the potato
plant except the tuber.

In fact previous to 1910 no reliable work
had been done on the genus. In that year a publication by
Wollenweber and Appel (1910) appeared which was the first
authoritativepunplication giving a aystematic treatment of
the morphological characters and laying the foundation for
the seperation of the spesies.

Wollerwevoer in 1913* aescribed F. oxysporum
as a"*vascular parasite causing the wilt disease but not the
tuber rot of Solanum tuberosum in the United Statee of
America, possibly also in Soutnern Europe and the potato
districts of South Africa, Australia, etc. Aliso found on
various hosts, such as Solarum lycopersicum, Vigna, Pisum
and Ipomoeo. The disease associated with the fungue has been
confused with " leaf roil" a disease called "Blattroll-
krankneit® in Germany."(A fuller discussion of tnese two wor:s
is given under morphology.) Tne final result of Dr. Wo:lermeber's
etudy of this gems will undoubtedly «straig/ften out and
simplify the cnaotic condition of the present classification
of tnis geme.

Tois description and classification is
considered authoritative and is used as the basis for the

following work.

* Woilenweber, H.W. Phytopath. 1913, p. 24.
5.

It is not the purpose of thie article to
discuss the literature in regard to classification,
nomenclature and morpnological chacterietics which are
fully covered in Wollermeber's work as well as in Smith and
Swingle's, where comvlete bibliographies can be found. The
account which follows concernes itself with the publications
upon the pathological aspect of tne wilt in the field and .
the presence of the disease as noted in different sections
of tne country.

Probably the first note upon the pathological
condition caused by this disease in this country was tnat by
Clinton in 1895.* He deacibes a condition found in the tubera
whicn ne caéils * burdle blackening". * Tnis ia a fungus
trouble of stored potatoes which srows as smalit aots or lines
@ snort distarce from the surfacer-e--re---- Tuese bundles
originate at tne stem end and send off a few bundles to each
of the eyes. The fungus gains entrance, probably after tne
potatoes are gathered, through the aead atem, and proceeds
from this through the bundies cauring them to turn biack as
the result of its attack." He goes on to say that, * tne
fungus is quite similar to the one causing the following
trouble.* He then describes a condition of the tuber whicn
he calle * dry end rot", * It affects all the tissue ase it
slowly advances forward, until, pernaps, the wnoie tuver is
destroyed. As in the preceeding case the trouvnle begins at
the stem end, the fungus gaining entrance after the rupture

* Clinton, C. P. p. 139, 1895.
6.

of the tuber from the plant.” He believed that the latter
disease was due to F. solani. In none of his observations
has ne connected the patnological conditions in tne fieid
witn the conditions he notes in storage, and he has probably
eonfueed the bundle blackening of the wilt with the stem
end rot caused by another Fusarium,

Stewart in 1696 writing on*Another Stem
Blight of the FPotato® describes a wilt of the potato and in
his paper says he was doubtful if any organism was responsible
for the trouble, This has been considered in previous
literature to nave been one of the first reports of the
F. wilt in this country and was tnought by Smith and Swingle
to be probably the same disease tney were working on, but
according to Orton # “The disease deacrived py Stewart (1896)
and thought by Smith and Swingle to be probably the same,
was stated by Prof, Stewart at a recent meeting of the
American Pnytopatnological Society to be not due to Fusarium."

Clinton in 1904*reports from Connecticut that
"many vines wilted pefore the middle of July" probably
caused by F. oxysvorum described by Smitn and Swingle l.c.
He connects the wilt with the umaual amount of bumie
blackening and rotting found in market potatoes. He apparently
reporte a condition simiiar to that described by Smith and

# Orton, W.A. 1913, p.3.

* Clinton, G.P. 1904, p. 349.
7.

Swingle in which he has contused tne wilt with other
Oorganismea causing dry rot of the tuber.

Smitn and Swingle l.c. in 1404 give the first
accurate description of the syptoms of the disase, and it is
to tnem tnat we owe much of tne present knowledge of the
Fusarium wilt in tnia country. In spite of the fact that
Wollerweber has since proved that tney were probably working
with more than one organism, their conditions of the path-
ological conditions found in tne field is atiil standara as
well as much of tneir cuitural work. It is well to note tnat
the first tubers Smith observed and on which he worked were
from Hubbardston, vichigan.

Tne next report of the disease comes from
Maryland, Norton in 1906 * reters to a dry rot as causea by
F., oxyenorum. * The disease is indicated by tne iignter
colored and more or less rolled up condition of the leaves.
When dug the potatoes may appear sourd, but internally snow
black or brown streaks, and later are destroyed at least at
One end by the dry rot." Here again we find the confusion of
the wiited condition of the plantea with the dry rot of the
tubers.

gne next report is by Orton in 1909 # from

California and is probably the tirst report of the disease

* Norton, J.B.8. 1906, p. 67.
# Orton, W.A. 1909, p. 4.
6.

on the Pacific coast. He says, ® Tne principal cause of the
marked decrease in the yield of old potato land is the presence
.0f a fungus disease, tne wilt or dry rot- Fusarium oxysporum
Sehlec. He gives a descripticucn of the wilt and dry rot
similar to that by Smth and Swingle.

Again Orton in 1911 * aescribes tne disease
in regara to its geographical distributién, ne says " the
disease described by Smith and Swing] e--------- e-----is now
coming into prominence as one of the most wide apread and
deatructive maladier of thie crop. It appears to occur
throughout the United States, but is more injurious in the
irrigated sections of the west and in the soutnern half of
the potato belt." His description is the same aa nis previous
one, °

worse in 1909 # revorts tne disease from Maine,
saying," Fusarium ary rot caused oy the fungus F. oxysporum
Scnliect. has bveen found for the first time in Maine during
the past summer.* He reports it as not being very widely
distributed through Kaine,

Loundsbury in 1909 ** desrcibes a dry rot of
the potato tuber found in Cape Colony as caused py Nectria

solani. He says, “* the infection is introduced into tne soil

* Orton, W.A. 1911, p. 751.
# Morse, W.J. 1909, p. 2.
** Loundsbury, C.P. 1904, p. 42.
9.

with diseased tubers and it remains there from season to
season, 80 that a crop from perfectly healthy seed may get
infected if grown on tand that previously pore an aftected
crop. The disease generally enterm at the stem end. The
fungus developes most rapidly in the vascular ring." From
his reference to the wilt symptoms shown by affected vines
it appears tnat ne nas confused the Fusarium wilt witn
another species causing a rot of the tuber.

Tidewell in 1910 describer a dry rot ana wilt
of the potato in New South Wales, which he says is caused by
¥. sclani, an organism which he claims shald be more properly
called F. oxysporum. He also makes refererce to the wilting
ot the tops, blackening ot the vaeculur regions and root
infection, showing that ne probably confused one or more
otner diseases with the wilt of the plant.

Manns in 1911 publianed a twilletin on tnis
disease in Onio. He desacrives a ex: ndition in the fieid and
storage similar to the one that Smith and Swingle reported.
He goes a step further, however, by saying that tne Fusarium
found in the vlackened vascular ring is identical with the
Fusarium of dry rot. Tnis he proved oy isolating the organism
from the two sources, and carrying them through artificial
cultures and inoculation experimenter. They were identical
and both brought about wiiting in the field. These inoculation

experiments are probably the first reported in this country
10.

and according to Orton (1914) cultures of the Ohio strain
have been studied by Dr. H.W. Wolienwever in comparison witn
& targe number of others and proved to be what we stiil call
F. oxysporum.

However according to Wollenweber's work iarna
must nave been dealing with a dry rot organism in connection
with the F. oxys-orum whieh he nad. The only point in his
infection experiments which might be open to criticism is the
fact that most of nis inoculation experiments were conducted
by growing healthy plants on baaly infected soil, and ne draws
the conclusions that * Tne disease comes on much more definetly
under the sick soil conditions than it did where artificial
cultures had veen used.” There is a possibility that a great
deal of the poor stand he speaks of in the sick soil may have
veen due to other organisms, because in carrying out an
inoculation experiment, in order to draw definite anda reliable
conclusions, it would be necessary to use realtny seed grown
in sterilized soil that had been imected with tne diseace
artificially.

The next report of the wilt comes from
Minnesota, Stakman in 1912 reports tne wilt as one of the
worst potato diseases in that state. He associates the wilting
of the plants and the browning of the tubers with the storage
rot , but says, * It is doubtful wetner this rotting is

caused by the same fungus which causes the wilting o1 the
ll.

vines. If it is not identical with the wilt fungus it is very
closely related to it."

Jones in 1912* makes note of the disease in
Wisconsin and describes it as a wilt and ary rot, wnich ne
reports as not ocaring seriously anywhere in Wisconsin,

* It seems most frequent in the southwest part of the state
where the soil is warm and early potatoes are grown,“ He

also mentions in the same paper a slight browing of the stem
end of the tuber which ig not caused by the wilt. “Apparently
due tO late autumnal growth or other cause, wnich interferes
with the full normal matureing of the tubers.*

Wollenmweoer in 1913 ** published another
article on the gems Fusarium, wiich he divides into rections
on the basis of torm of conidia and other morpho: ogical
chacteristics. F. oxysporum he places in the section fleganr
which contains all tne vascular parasites causing wilt, and
differenciates this section from the other Fusaria,

Wollerwever in 1913 1.¢c. also publisned in
Phy topatnology, the results of furtner work on Fusaria. in
thie he refers to the unreliability of the stroma as a
taxonomic character owing to the variation of forms on the
defferent substrata. He describes in detail the morpnoi ogical
characteristics of this species, whicn will be taken up later,

* Jones,L.R. 1912, p. 4.

*%* Wollenweber, H.W. Ber. d. deut. Bot. Gea. 1913.

 

 
-~_—-
le.

and also states that the potato is the host of 30 different
forms of Fusaria. This article refers to many inoculation
experiments and also contains a complete pibiiograpny.

The latest article in print on this subject
is probably the one by Orton (1914) in which he takes up a.
general discussion of the symptoms, cause of the disease
and control measures aa well as the geograupnical diatribution
of the trouble, which ne claims is found in all the potato
growing districts of the Umted States and he also beleives
that there is no evidenee that tne Ame:ican wilt disease

occurs in Burope.
13.
GEOGRAPHICAL DISTRIBUTION.

In tne first extensive work aone on this
disease by Smith and Swingle l.c.*tney report after examinati on
of tubers from District of Columbia, Michigan, Virginia,
Kansae, Nebraska, New York, Florida and Wiscorsin that ,
°® It seems safe to sry that Lnis disease extends north to
Canada, east to the Atiantic, south to the Gulf of rexico
and west to Colorado. How much wider its distribution is in
this country cannot be stated at the present time, but it is
almost undouvtedly beyond the limits from whicn it nas been
so far reported."

This latter statement was soon proved by the
widespread reports of the disease in sucsequent years,
especially from Califernia where the disease had not been
reported at that time.

Orton(I914)* after a study of the occurrerme
of the disease in the United States, concludes that " It is
certain that tne Fusarium wilt is a nation wide problem and
one that will have a marked infiuence upon American agriculture,"
He aleo states that aftera study trip througn Germany, Austria
and England in1911 he veleived tnat there was no evidence
tnat the American wilt occurs in Europe. Reports of such
occurrence have been confused with the leat roll disease.

* Smith, E.F. and Swingle, u.B. 1904, p. 42

** Orton, W.A. 1914, p. 16.
14.

Dr. Wollenweber in his morvnnoiogical studies of Fusaria
has been able to differeaciate the F. oxysporum cauei ng

American potato wilt from the European form.

CLIMATIC RELATIONS.

Most of the Fusaria causing a wilt dis+ase of
other crops are apparently diseases of tne waruwer clinates.
The Fusarium wilt of potatoes is undoubtedly more serious
and causes more Joss in the soutnern atatea than in tne north.
In fact Orton (1914) states that +usarium wilt le avparently
a@ disease of warmer climates. The soutuern states with high
summer temperatures seem to suffer more than the northern
States. new England and tew York are reported comparitively
free from tne disease, wiile Manns in Onio reports a very
wide distribution. Going weet the tungus is found furtuer
north, many cases having veen observed by the writer in the
irrigated sectiorns of Idano and in eastern Oregon.

she results of a months atudy of tie aisease
in ..ichigar snowed the rresence of the wilt even as far nortn
as Houghton, and several sections of the Upper Peninsula.
were found to ve neavily infected; the same amount of infection
was found in the southern part of the Lower Tenineulayz, 80
that in the opinion of the writer the temperature conditions
do not affect tune distrivoution of the disease to any anvraciable
amount in tne state of sicnigan, and probably a closer

inepection of potato crops in many of the other northern
15.

potato growing st ates would reveal the preserce of the
wilt in many cases.

Neither do the s:i0lature conditions present
any detinite distinction on the severity of infection, aa
mary of the fielde examined in the Upper Peninsula had been
exposed to excessive rains in the tater part of the summer,
while fields simiiarly infected nad been through a comvaritively
dry field in the Lower Peninsula. There is nowever,an affect ,
that the various moisture conditiors would nave on the
severity of infection by means of weakening tne nrlants and
predisposing them to infection or by causing a pvreaking down
or the tissues in the plant and making them more suceptible

to invasion by the fungus.
16.

ECONOL:IC IMPORTANCE.

The economic importance of the disease in the

United States varies greatly with the comitions found in tne
various localities, but it is undouvotediy much greater than
was previously supposed, and the disease will contime to
spread until more tringent metnods are used for its control.
According to Orton (1914) the disease in the
soutnern states wnile of possibly greater severity, is of
minor importarce owing to the fact that in most districts
tue Irisn potato is a minor crop, while in the trucking
sections of the soutn the main crop is the early one grown
tor nortnern markets and the infection of this cron is
relatively slignt compared with that of the fall crop. in tne
irrigated sections of the west the disease plays an important
role because of the necessity for a longer rotation of crops
less remunerative than the potato. In Caliiornia the wilt is
tne prinepal factor in causing a reduction of tne yield in the
San Jouquin Vatley, (Orton 1909). It is also serious in Oregon
and a few otner western states. In the middie west Ohio and
Michigan are badly infected and recent reports would show
that tnere is also a great deal of infectiun in Wisconsin.
Estimates of the money losses caused by this
disease are necessarily very aard to ovutain, owing to the
peculiar nature of the disease, and the small amount of

im ormation avallabie. Tne loss is occasioned principally by
17.

a reduction in the yieid, and there are so many otner factors
wnicn may cause a reduction of the yield that it is almost
impossible to determine tne exact amount of ioaes caused by the
wilt.

Manns of the Ohio station reports in191l tnat
the sick sc:il conditions may reduce the crop in mary cases
50 # or more of. the average yield. Their experiments on
infected fields show a yield of 69 bu. per acre, while the
average for the county was 186 bu.. Tne nreceeding four years
average for the station was 1:0 wu. and the county 101 bu.
This shows the large amount of injury to the yielid-caured by
tne wilt, and fuguring that only 5 @ of tne Onio fields were
infected, he would estimate that the loss would amount to over
870,000 bu. for the state.

In this state the lora could not be accurately
acertained from the field data. The fieldea exa;ined showed an
average of 30 % siight infection and 1.5 % serivus; clearly
inaicating the large amount of toss due to the disease in tnis
state. In many cases where the infection was bad the yield was
reauced to under 100 bu. per acre, while there were very few
Other fungus troubles found in the same fields. Tne averare
given nere is probably low for the entire state as this was
taken from the best fields growing votatoes for seed purposes,

The disease is more important economically in

this state in the seed growing section, The serious infection
| 18,

found in bhe state during the last year was not large enough
to be of great economic importance, but the fact that the
high percentage of slight infection is present, is of vital :
interest to the seed grower as even the slight imnfection of
the tubers without materially decreasing the yield for the
present year would disqualify tne potatoes for seed,

‘The widespread occurrene of the wilt in this
state makes it undoubtedly one of the worst enemies of the
potato grower, especially as it is hard for many growers to
realize, that while the present years crop may not be badly
damaged, by planting the irnfecteec tubers the following year
tne stand will probavly be very poor anda the yield materially
reduced.

Thus it is seen that tne disease is of tne
greatest economic importance in this state especially in
those sections where the growing of potatoes tor seed is
being conducted, and it should be considered as such, vecause
of the great ditficulty in eradicating the trouble from the

fields after it has once gained a foot hold.
19.
FIEYV.D OBSERVATIONS.

Early last fall it was decided to conduct a
system of potato seed inspection and certification in this
state by the cooveration of the Michigan State Potato
Association and the Michigan Agricultural College. The writer
attempted to conduct this work and during the month of
September and October many of the ost important seed potato
producing centers were visited personally, in both the
Upper and Lower Peninsulas.

A general survey of the potato diseases in the
state were obtained in this way and the widespread nresenceof
the Fusarium wilt was noted and the particular condition of
the infected fields was observed by tne writer and accordingly
was made tne subject of special atudy in the field and the
coOntinuence of the work on the »roblem during tne winter.

Tne following data were ovtii ned py tne writer
during September and October, one examination being made just
vetore digging time, Only tnose lields were examined that
were being grown for seed, so that the nercentage of diseace
taken trom these fields would probably not be ase hign as an
average of the entire potato crop of the state. It waa
impossihle to make examinations of all tue potato growing
sections in the state bu. tnose counties which were examined
are probably afair avcrage for the entire state. Two counties

were examined on the Upper Peninsula; the principal potato
20.

“rowing sections in the northern part of the Lower Peninsula
as well as St. Clair county in the southeast and several
isolated fields of the larger growers in the central and

western sections,

METHOD OF TABUT.ATION., .

Tne percentage of infection in a one- half
acre field was obtained by a close examination of about 300
tops, a short examination of the entire field, and by digging
up three or four groups of 10 consecutive hiils in various
parts of the fild to obtain a good average. In all the hills
dug up a cross section was made of the stem end of tne tuber
and alego of the main stem of the plant a short distance
above the tuber, and sections further up the stem were made
to determine how far up the stem che fungus advarced. On
larger fields a greater mmber of plants were examined, in
propor.ion to the size of tne field.

Tne percentage of slight iwfection does not
relate to the depth of infection in the tuber but indicates
tuat the plant was fully matured, all tubens tormed, no
wilting of the tops occuring and no material damage to the
crop could be seen, although the browing of the vascular
system in the stem and tuber was present,

Tne percentage of serious infection indicates
that the Plant had witted and died before the tubers had

matured thus greatly decreasing the yleid.
the field
indicated

and would

was taken

21.

Total infection indicates that all hills in
showed infection, either slightly or serious as
in the tables. Tnis is simvoly an approximation
vary trom 85 % - 100 %.

In all the examinations the entire tield

as the unit and not the acreage,
Cle

ALPENA COUNTY.

yi ¥
slight serious other frost date —
Now Acres-Variety-infect.-infect.-disease-killed-inspection.

 

Late 1%

I.- +-Petoaky-- trace-e- —mae ee -slighte noee Sept. el.

 

 

Rural ,
2.-I4- N.Y. ow ® r " " ne
3-H ” 2% * e ° " .
Late
4.-8 -Petosky-- 5% " " " Oct. 25.
5,<I- ] I ” ® " i] Sept. 12.
6,-3- " 4." * ” e n .
7et2- ec = ww we a " " n .
8.-I - * 8 & " moderate " " ".
Jet = " " . slight " " ".
Rural
I0-3 - N.Y. 4G " serious " . ".
Late
II-4 -Petosky " " moderate " " ".
I2-4 - "* IO & 8 serious " " ".
DELTA CCURTY.
Sir “alter
I- I3- Raleigh- 15 %-- 25% moderate no Sept. 31.
ANTRIM COUNTY.
ate :
I-19 -Ppetoaky -- 3% ---- moderate- yes Sept. I0.
2-34 - * a" " serious no no 8,

3-10 o Lf I " ] « "” #8 "

 
23.6

IRON Ccusty.

 

slight nerious otner troat date
Nov Acres- Variety-infect-infect.-disease-killed= inspection.
Sir Walter ~
I- } -Raleigh --15 fe- 2% slight yes Sept. 21.
Early
2.- I -Mackinaw--20 "  ---- " " " 23,
3 - t -8S.W.Ral.-- 6 * 2 & " " " 18.
4- %- * 3% ee. moderate no " I7.
5- ¢e- * I5 * 3% serious " " 23.
6-}- * 5" I* glight yes " 18.
72° +t- * 6 * 4" moderate "* " 19.
8- ¢- * 7°" 6" slight " " 18.
9- I- 8 I5* 5A " " " e
I0- 2% - * 100 * ---- moderate " " 23.
Il- It - * 7” 2% serious no " ",
I2- 1/f8- * 20 * 6" " yea " 2I,
I3- Is - * I0o * eoe- " " " no
I4- H- " 6 * 3% moderate '" " 18.
I5- I - * 9" 6 * seri ous " " ".
I6- 3#- * 8 * ---- moderate " " I9,
I7- t¢- * 58 ---- serious " " 17.
I8e %- * 8" cw, “ no " 18.
19- ¢- ® I5 * 5" " yes " 2I.
20- $- * 35" 4° " " " a.
21- 2-+ " 6° 3" slignt " . 19.
22- I- * 8" 4° " no " ".
24,

%o fo

elight serious other frost date
No~Acres-Variety-infect.-infect.-disease- killed-inspection.

 

23- 4 - S.W.Ral.- 35 %- ---- slight yes Sept.23.
| 24- t- " BM " serious " " 17.
25-2 - " 6” " moderate " . "
26- 2 - " | 28 * 2 slight . . 2I.
27- I- - 20 * " " no " 21,
28- I4 = 3° “ moderate yes " 18.
29- It - * 100 * " " “ n 22,
30- I = " I2 * " silght a " 23.
3I- ¢- " 8" 24 serious " e 19.
32- ge " 30 & wwene moderate "* " 2I.
33- ¢- " 20 * 4% slignt " . * .
34- I - * 4* op. " no * 19.
35+ 24 - " I00 "% -«ee- serious yes " 2I.
36- 4 -Carmer# 3- 2 * " moderate " * I7.
37- 4= Rural N.Y.- 18 * " " " n 623.
38-23 - " 58 2¢ " " noon.
39- 2 -S.W.Ral. - 10% ---- " n = 17,
40- I - " 100 * " serious " . "
4I- 4- " 2° " slignt " " #9.
42 -} - ° 6" 22 n " ” .
43- I - " 4 * 3 & moderate " " *
44- ¢- * 30 * 4°” serious " * 2iI,
45- 2 -Rupal N.Y. Qo” 3° moderate " " "
25.

% %
slight serious otner trost date
No- Acres-Variety-infect.-infect.-diseases-killed.-inepection.

Gant...

 

46- be Petceky-- 8 %e I %- moderate- yes- Sent. I9.
47- +-S.W.Ral.-- 20 * 2" serious . " 21.
48- H- * 5 * oon slight " . 18,
49- 2 - " 35 * " modtrate . " 21.
50- 2- * 20 " 34 " no " ".
5I-e I- * Io * 2" slight " " 23.
52- 24-  =* 4 " e-e- serious yes 17.
53- I - " I00 * . slight " . 22.
542 3. 8 6" " n n " 18.
Green

55=- 5 -Moufitainea- 25 " . serious no Oct. I6.

 
HOUGHTON COUNTY.

%

slight

%

gsericus

otner

frost

date

26.

Now Acres-Variety-intect.-infect.-diseases-killed-inspection.

 

Oo co ~“ On we Ww N -
9

ro
pL
é

15=

I}-Irish -
Cobbler
2 @

4-S.W. Ral.
+ «
If *
Rural
2 N.Y.
IRISH
2 Cobbler
2 @

I+ *
£-3.W. Ral.
4 Barly Onio-

Beauty of
44 Hebron
3 S.W.Ral.

Irish
I-Cobblers

4-S.W. Ral.

15 %
40 °
20 *
100 *
30 *
10 &
20 &
I0o *
100 *
100 *
5.
100 *
40
30 *

16-18 -Rural N.Y.- ----

I7- 3¢-S.W. Ral.

15 %

25 %

IO %
*

3 %
Qo 0

8%
30 &

moderate
siight

slight

moderate
slight

serioue

no

yes

no

yes

no

yes

no

yes

Sept.25.
27,
ST. CLAIR COUNTY. |

%

slight serious other frost date
No- Acres#Variety-infect.-infect.-diseases-killed-inspection.

 

Green
I - 44-Mountains- II % “--- moderate yes Oct. 3.

2.1 " 58 " n " "4,
Rural
3- I0 Ruseseta Ioo * " slight " " *.
4 - 2 Gr.Nount. 100 * " moderate " . *,
5- I Irish Cobbler * " " " " ".
6 - 1 Peach Blow- 100 * " slight “ “ ",
Barly
7 - 4-Eureka 100 * " . . * 5.
8 -I/s Rural N.Y. 100 Z& " o--- " _  ®,
9 -10 Gr. Mount. 8 * " slight " _  *,
I0-IO0 Carmen #2- 100 * " serious " _ 8,
II- 4 Early Mich. 100 " " slight " . *,
I2- 5eGr. Mount. 17 * " serious " » 6.
I3- 4 " 6" " slight " mM,
I4 -4-Rural N.Y.- I00 * " serious . " *,.
I5- 4- Gr. Mount.------ " slight — " _  *,
I6- 2 " 24% " " " n a.

 

BARAGA CUURTY.
I - Is- §.W.Ral. 8% I5 4 slight yes Sept.25.

2.- 6-Carmen #3.- 8 * I" . no ° "* *®,
SUMMARY OF DATA,

28,

 

Average
7 for
ALPE NA- ST. CLAI R- HOUGHT ON- I RON- State.
No. tields exami ned--------- l2s- 16s- 17s°- 55e- 100.
Total acreage------ eccene--- 22.5- 56. 49.5 84.75-212.
Aver. acreage per field----- 1.8 3.3 2.9 1.5 2.6
Aver @ slignt inf. per field. 4. % 60. & 40.5% 21.8% 30. %
" " " " " acre-- 2.1* 17.3" 13.9% 414.2" #11. *
* © gefious " " field- -<2- -<--- 4.5" 1.6" 1,58
" “ ® * " acre-- neee eeee 1.5" 1. * ~6"
@ tieldea with total inf.---- ---- 56. "% 29, * 10." 23. "
» © over 10% slicnt inf. ---- 75." 76. * #49." 50. ”
" " " "serious " ., ---2 ---- 3.5 *% -cnee oh
" " slight & " " eres ecco 3.5 " 50. *® 13.3"
" " total infect. s81.& ser. ---- --=-- 40. ~er- 10. *
" " serious infection,\---2 <«-e2 c--- 35." 52. " 21.7"

 

DISCUSSION OF DATA.

It appears from the above data that there waa

@ large amount of Fusarium wilt present in this state during

the past season and that the greater part of it proved to be

a slight infection which showed as a aistict browning of the

stem and tuber in the vascular system. Tnis infection showed
 

 

ene. =
RS ne nee ste
29.

when the tops were still large, green and vigorous, but did
not appear to materially injure the yield.

There is an average slight infection=e taken
with the tield and not the acre as the unite of 30 % while the
average serioua infection was only 1.5 % Practicaily all the
fields nad some slight infection while only 21.7 % of the
Tields nad any serious infection, and two of the four counties
visited proved to ve entirely free from ang serious infection.
The percentage of the fields having a total irfection of a
slignt nature was 23 &.

This peculiar comition i.e. the large amount
of slight imection has been made the subject of investigations
conducted in the laboratory during the past winter.

Nany of tne plants infected with Fusarium early
in the year appeared to have wilted down and then in the
subsequent wet weatner, a bacterial decay set in and caused
a@ rotting of tne stem and main root down to the tuber, so as
to resemole black leg, yet distinquisnanle from it in most
canes as the rotting was not as black aa in the typica! black
leg and there was no rotting of tne stem erd of the tuber,

In all of tne fields examined the s0i1 conditions
varied so greatiy that no conclusive resuits could be optained
as to the effect of different soils and fertilizers on the
amount of the disease present.

In some of the fields especially in Hougnton

County the disease arpneared in the field in streaks and patcnes
30.

giving an indication that there is a possibilityof the

disease being svread by means of cultivation.

FROSTING.
The question was brought up by many growers
as to the effect of frost on the peroentage and seriousnesa
of the infectnn.
FIELD DATA. Average

for
Alpena-St.Clair-Houghton-Iron- State.

 

Aver. slight inf. before t rost- 4. % -2-- 17.5% 2.3% 5.9%

* serious * ° " eece ones 4,3" .2" «101°
" " after " erce core 4.7" =+1.3" «+125"
. slight. . . . “eo 60.% 6}. . 19. . 35. .

 

The plants examined after frost appeared to have

only the foliage killed, in mo: t cases the main stem was atill
in a green condition,

Fields examined in August vy Wm. Stuart and
1e-%.Jonnson on tneir -otato inspection trip in te Upper
Peninsula and declared to be free trom Fusarium wilt, were
latter inspected by the county agent and all plants snowing
any symptoms of the disease on the tops were pulled out.

When examined by the writer a tew days after frost they showed
_ wee re
31.

practically a total infection with Fusarium. Tne probability
is that the above mentioned men had not dug up any of the plants
and so had not noticed any of tune vrowning of the stem and
tuber, wnich may not nave been accompanied by the wilting
condition. In other fields examined by them and declared to be
free, and examined voy tne writer bel ore irost there was a
large amount of slight infection not accompanied by tne wilt.

} In the above data we tind that tnere is 35 %

of slight and h.§ % of serious infection found when the exanm-
ination was made after the plants had been wilted by frost,
against 5.9 % slight and 1.1 &% serious infection found on
Plants exanined before frost.

There are several conditions and possibilities
that should be considered betore definite conclusions can be
drawn from these data.

From the first two counties we can draw no
detinite conclusions as in Alpena county the tields were all
examined vefore frost, while in St. Ciair county tne entire
examination was conaucted after frost. In Houghton and in
Iron counties the exami nation of the fields were made at
practically the same time in the respective counties and tne
tields not frosted were due to their particular iocation and
elevation, In these tields we tind an average slight infection
of 61 4 in Houghton and 19 @ in Iron county after frost,
against 17.5 % and 2.3 &% resvectively vefore frost.

Tne next consideration is that the percentage
32.6

of infection be compared with that of tne field from which the
seed was obtained. This could only be dore in Alpena and in
Iron counties and the fields in Antrim and Delta counties
from which the seed was obtained were examined in the same
condition relative to frost as those in the former counties,
and it was found that the percentage ot infection was about
the same,

The most imvortant condition, that of the land
on wnich the crop was grown was not a constant factor in any
of the above mentioned lields.

In order to draw detinite conciusions it
wouLtd be necessary to examine crops from tields on which no
potatoes had been grown for a long enough period to 1 nsure
against the possibility of soil infection. Tne seed snould
be obtained from the same source and the fields should be
examined at the same time, some being frosted and otners atill
in the growing conaition, As the conditions were not constant
in ary of the examined fields no detinite conclusiors coulda
be drawn.

There is also the possibility of the frosted
condition weakeni;g tne plant s0 as to make it casier ior the
enterance of the organism, but as all the fields were examined
Within a short time after frosting it does not seem porsible
for the organism to have meade its appearance in such a short

space of time.
33.

The writer knows of no condition in which the
frost, only killing the toliage of the plant, could cause a
browning in the vasctlar system of the main stem for only a
snort distance above the surface of the ground and also in
the root and stem end of the tuber, shown by the presence of
F, oxysvorum in tissue cuitures taken from these tubers. So
the possibility of frost being responsivle for the large
percent of slight infection found in this state has not been

considered in the following investigations.

VARIETAL SUSCEPTIBILITY.

FIELD DATA, Average
for
Alpena-St.Clair-Houghton-Iron- State.

 

Rural New York, slight infect- e--- 100. © 12.5 %10. % 31. %

° * © gerious "* 4.5% ene 4." 1.6" 1.4"
Late Petosky, slight " 2.3% enn core 8. * 2,5"
Green Mountain "* " cere 21. " “7 25.-" 11.5°
Irish Cobbler " " ee-2 100. " 17.8" -«--= 29,4"
Carmen . . ---- 100. * ocoe 2. * 25,5"
Sir Waiter Ral. * " ence evne 58. * 23. * 20.2"

" . " serious . erce eee 4.2" 1.7" 1.4%

In regard to the susceptibility of the ditfrerent

varieties grown in the examined 1ieldsa no reliable data could
34.

be obtained from which definite conclusions could be drawn,

In order to obtain definite results on varietal
susceptibility it would be necessary to have plots of the
different varieties to be tested growing in the same infected
tield under the same soil and atmospheric conditions, all seed
being free from ihe disease and the examination conducted at
the same time on all che plots.

It is not possible to opntain this data so no
conclusions are drawn as to varietal suscentibility, but tnis

is a field in which very imvortant results could be obtained.

SUMMARY OF FIELD OBSERVATIONS.
1. There is @ large amount of Fusarium wilt
in the state that appears late in the season causing no wilt
of the plant and no onservable decrease in the yield.
2. A much smailer vercentage of sericus infection.
3. Fumerous fields showed a condition indicating
a spreading of the disease tnrougn tne soil by mesna of
cultivation,
4. no definite conclusions could be draw: as
to the effect of frosting, varietal susceptibility, or soil

condi tions upon the ama nt ot infection in the field.
35-6

SYMPTOMOLOGIC ASPECTS.

DESCRIPTION OF DISEASED PLANTS.

The most characteristic symptoms of this diseace
are a change in the color of the roliage accomnvanied by a
rolling and wilting of the leaves, causing a premature death
death of tne foliage; and the occurrence of the fungus F,
oxysporum in the vascular systems of the lower part of the
stem and of the roots and tubers.

The tirst noticable indications of the disease
varies greatly with the seriousness of infection. In case very
badly diseased seed stock has peen used, the germination is
poor and the stand is uneven, Aithough all the plants may
appear above the ground they will vary in size and vigor.
the disease progresses as in the following description but is
more rapid owing to the early infection before the planta
have obtained a good growth.

The more common occurrence of the disease is
found nowever,in tubers not so seriously imected the early
growth may be retarded slightly, but the disease tirst becomes
noticable to the casual observer when the plants have attained
the neignt of 8-14 inches, In many cases the rlant does not
show any marked symptons till midsummer, and often wilting o1
the plants does not occur until a snort time, two or three

weeks, before the normal death of the planta,
36.

In all of these serious types of infection
the witting of the top is the first symptom to be ovserved.
This avpears first as a change in the color of the foliage,
usually to a lighter green than that of the healthy plants,
particularly in the lower leaves. This lighter green appearance
gradually changes to a yellow or brownisn color, entirely
covering the infected vines and giving the field a mottied
appearance; Or in cases where tne infection is found in
patenes there will ve a very conspicuous yellow patch of
diseased hille contrasted against tie normal green foliage of
tne nealthy vlants. In some varieties havi ng @ dark green
foliage, tne changes in color are not so prominent. This
yellowing of tne foliage is accomvanied by a rvelling of the
leaves from the midrib upwards and inwards. The lower leaves
or tne plant are tne tirst to die, they wilt over and remain
attacned to the main stem by a email strip of the stem. Tne
upper leaves then roll uv and wilt but do not drov; they
appear very limp and die in a snort time,

When the top of tne plant nas been entirely
wiited the disease has usuaily crogressed tar enogn to
materially weaken the stem and the plant often droops over and
lies on the ground, especiaily if the so01l1 has not been
hilled up. Ysually when the plants reacn this condition
they can be-nulled up very easily, tne roote being very

brittle and friable,
37

This premature death of the plant shortens

the life of the crop from two to six weeks, thus materia'ly
decreasing the size of the tuvers, which have not as yet
matured, and appreciably decreasing the yield.

| Another tyve of the disease which nas appeared
to a great extent in Nicnigan during the past year is
cnaracterized by a late or slight irfection of the vlants.
In tnois case tne early symptons of yellowing, wiiting and
premature death of the plant are not onserved. Tne disease
does not avpear until after the entire plant nas matured, and
there are no visable symptomea ot the disease in the parts
above ground. However when the plant is dug the cnaracteristic
browning of tne vaacuiar systema in the stem and tubers are
found. This condition cannot be observed by a casual examination
of the tops but can only be deteruined oy digging the plants
and cutting across the stem and the tuver. It is probably due
to thie fact that this stsge of the diseage has not been more
widely noted, and the subile and persistant nature of this
manner of infection more seriously considered py plant path-
ologists.

Tnis condition was briefly refered to by

Smitn and Swingle * wno write, * In case the plants are not
attacked untit the stem and leaves have nearly reached maturity,
the early symptoms of curling and dwarfing of the foliage

ado not appear. Even in such cases, however, if the roots are

* Smith,E.F. and Swingle, D.B. 1904, p.14.
38.

entirely destroyed beofre the tops nave died down there are
the later symptoms of wilting, but often the fungue grows
into the tuner without causing any visable symptoms in the
parts above ground.* Apparently the same condition was
noted by Orton * who states, * It is not uncommonm to find
prematurely dead hills in infected fields which show compar-
atively slight vascular browning, wnile others remain living,
yet wnen examined they prove to nave both stems and tubers
neavily infected with F. oxysporum, Tnis apparent resistance
may ove exvrlained by the fact that sucn nills were either
accidental admixtures of other varieties, or bud sports,
called'run out nills'. In either case they are plants that
remain in an active vegetative condition longer and thus
resist the effects of the wilt. Stiil other hills are found
which remain nealthy till the normal time for maturity and
are also free from fungus infection, thereby supporting the
hope tnat resistant strains may be develoned vy selection.®
._He goes on to state however, that in cases where selection
had been made, they were all attacked by the wilt the
following year.

The same condition can be noted in potato
plants attacked with Rhizoctonia after reaching maturity,
in wnien case the tops have a normal greencolor, and remain
green even after the rest of the »-lants ave died down, while
the stem may be entirely rotted off a snort distance pelow
the surface of the ground and can be pulled uv easily.

*Orton, W.A. 1914, p.6.
39°

It would appear in the light of our present
knowledge that tnere is a great possibility of tnia condition
being due to a late infection attacking the plants after the
‘tubers have matured. But it may also be vnossibly due to the
presence of resistant strains or to a comvination of both.

Wetner this late infection is due to a slight
infection through the seed stock or to an infection through

the rootea from the soil nas not been determined as yet.

OCCURRENCE OF THE CAUSAL FUNGUS IN THE STEM.

the presence of tie mycelium of the organism
is shown in the vascular ring of the stem as a characteristic
brown discoloration. This extenda through the entire under-
ground portion of the plant, and a short distance, several
centimeters, in tne above ground stem. The mycelium does not
nowever extend up into the upper stem and ieaves, Cultures
made from the upper stem and foliage o1 infected rliantsa
snowed no presence of F,oxysporum nor did a micrscopic exam
ination snow the presence of any hycvhae. However mary cul tures
were made from the vascutar ring in the stem, slightly below
the surtace of the ground, and at ditferent points extending
down to the tuber. inese cultures yield almost always, a
single species of fungus, Fusarium oxysporum, altnough other
organisms are often prerent as may be expected.

By means of this cistinet brown disco] oration

of the eatem for a short distance above the surface of tne
ground and exte:ding into tne roots, we are able to distinguish
clearly between the Fusarium wilt herin dercrived and the
varicus other wilts and leaf rolls of the vnotato plant. In
the case of Verticillium wilt the brown discoloration extends
up into the top of tne plant and is the cniet means of
distinquisghing the two wilte wnich would otnerwise be easily
confused. The amount of nypvnae present am the depth of
discoloration varies greatly.

In mary cases not all the shoots in the same
hill show infection, and it ie not unusual to find some
shoots in a hill uvright and hneaithy , whiie otners have
wilted and died. In the seme manner we ofter find a mmber of
potatoes in a hill srowing infection wnile others are entirely
free from the fungus. Znis fact would irdicate trnat much of this
infection comes through the doil and enters the planta tnrougn
the roote and gradua:ly invades the atem also working back to
tne seed piece but not rapidly enough to apread it to tne

Otner shoots in the hill.

OCCU RENCE IN THE ROOT.

As stated above the fungus is evidently abie
to gain entrance to the plant through the smailer roota as
well as through the seed riece. This entrance is usually
made through wounds and is shown as a brown discoloration

of the vascular system. !umerous cultures were made from tiuese
41.

discolored portions and in nearly all cases F. oxysporum was
obtained, It is often accomvanied by otner species of fungi
causing a white or pink growtn of mycelium on the affected
roots. The infectea roota are usuaily much more orittle than
normally and can be easily vroken between the fingers, instead
of veing nliabie as in the normai roots. Tne main root ia
aiso much more tender and brittle than normaiiy. The fungus
is also found extensively in tne underground stem on which
tne tubers are borne, and extending into tne tuber, but these
portions of the plant do not appear as vorittle as the roots.
The diseased condition of tne root hairs and
secondary roots is probably recponsible for only a slight
part of the checked developement and death of the tops, althougn
possibly causing the first siages of the disease.
Undoubtedly the greater damage is due ratner to
tne invasion of the water conducting tissue of the plant oy
the mycelium of the fungus, or to a poisonous byproduct of

the fungus or a combination of both.

OCCURRENCE IN THE TUBER.

Tne presence of the fungus in the tuber can
always be observed by the diatinct browning of the vascular
ring shown by cutting across the stem end of the tuber.

The depth of the brown disc::loration varies
so greatly that in the cases where only a very slight discolor

ation is found it is hard to iaentify it as F. oxysporum
42.

without the cultural studies or the accompanying symptoms

on the tops. In nearly ajl cases tried where the brown ring
extended for only 2-3 mm. into the tuber it was possible to
Obtain cultures of F. oxysporum, In the few cases wnich did not
show the presence of the organism, bacteria or other fungi

were always found, and had probably entered the tuber for a
siight depth through tne diseased etem,

The mycelium advances slightly into the tuber
in storage. Smith and Swingle Obeerved cases where the fungus
advanced the entire length of the tuber, but during the past
winter no cages were found here where the infection snowed
as a brown discoloration for more than half the length of the
tuber, and the fungus did not appear to progress very rapidly
tnrough the tuber in storage,

Tubers of all sizes are attacked often snowing
the presence of the furgua before the tube: is mature,

The affectea potatoes to all ovtward appearances
seem perfectly sound, and the flesh inside and outside the
vascular ring ia white and perfectly normal. Such potatoes
pass in the market and are often planted by the grower who is
not familiar with these signs of the disease.

This tuber imtection and the stem end rot
condition were considered identical by Smith and Swingle but
recently Woilenweber(1913) has proved that F. oxyeporum is a
strictly vaecular parasite incapable of attacking the tuber

through wounds or of producing a rot of the varenchyma.
$3.
ETI OLOGY

PRESENCE OF THE CAUSAL ORGANISM.

The fungus Fusarium oxysporum has been repeatedly
isolated in tne laboratory from vilantsa snowing infection by
tne cnaracteristic wiiting of the tops and vascular discolor-
ation of the undervround portions of the plant.

The isolations were made from the vcuvers as
tollowea:- The suspected tubers were first washed with water
thoroughly and then soaked in 1-1000 solution of HgClo for
about 10 mimtesa. A not spatula wea then used to sear the

surface of the tuber where the cut war to be made, then by
means of a hot knife the tuber was cut part way trirough, then
broken across the reet of the way. With a sterile scalpel,
emall pieces avout 2mm, in lengih were then removed from the
im ected vascular bundles on the broken surface, This piece
of tissue was then transfered to a poured rlate of agar.
Usually potato agar was used and sometimes mtrient agar.

The same met ods were used in making isolations from the stem
and roots. From these plates the tungus was then transfered
to tubes of eteamed potato plugs.

The fungus was isolated in this way from a
large number of tubers obtained in various parts of the state
and varying greatly in the depth of infection. In practically
all caeea the fungus appeared in a few uays as a white

mycelial growth, sparse at firat, growing directly out of the
44,

imfected tissue and quickly epreading out into the media,
All of these mmerous isOlations produced the same morphe
ological characteristics in culvcure,

In a few cases bacteria appeared along with the
fungus, when the tissue was taken from the extreme end of
tne tuber, the bacteria probably entcring through the diseased
stem in the same way as vhe fungus. Usually the fungus alowly
overgrew the bacterial colonies and it was pogsible io
transfer the culture to steamed potato plugs.

Many isolations were attempted from the tireue
On eitner side of the discolored vascular bundle and also
from the vascular system immeaiately in advance of the brown
discoloration, but in no case was fungus growth optalned,
while isoiations of the discolored pundles even in cases of
avery elight discoloration only a few millimeters deep
produced a good growth ina few daya.

Microscopical examination of sections of the
vascular bundle snowed the abundant presence of mycelium,
while sections made from the tissue on elther side, or in
advance of the discoloration or even at the extreme end of
tne discoloration did not reveal the presence of any hyphae.

The same results were onmtained py isolations
made from the stem. These facts indicate that the fungus does
not proceed in advance of the brown discoloration, but that
the brown discoloration may vroceed slignitly in advance of

the fungus. Also that the fungue aoes not apread out from the
45.

bundles into the surrounding healthy parenchyma tiesue,

PATHOGERICITY.

The pathogenicity of the organism worked with
was proved by isolating the fungus from the tuber as described
above, it was then grown in culcure on steamed potato plugs
or stems and later inoculeted into neaithy plante in varioua
ways, ( infection experiments p ) Tne characteristic
browning of the vascular system was produced and the fungus
again isolated and grown in culture where the same morphological
charactere were observed as beirore.

The stock cuiture used in all the following
experiments war obtained by tisaue cu:itures made as described
above,irom potatoes showing only a slignt intection obtained
from farm near Paw Paw, Van buren County, Micnigan, Tue fungus
was tnen transfered to potato agar slants and a single spore
was traneferea to a poured vlate of agar. Tnis was done on
plates to make it possible to examine it unaer the microscope
and determine that unly one spore nad been transfered. Tne
single spore was obtained with a very fine platimm Loop from
the agar slant, observed under the mic: oscope. This culture
after a few days was then transfered to poteto plugs, several
sub cultures made and teo of there sent to the Laboratory of
Plant Pathology, Bureau of Plant Industry at Washington D.C,

for identification, Tney were identitied as Fusarium oxysporum.

Cul tures#3377 and # 337%.
46,

MORPHOLOGY.

The fungus is found to grow readily on a wide
variety of media but the form and density of the growth as
well as the morpnological characters of the spores vary
greatly according to the subetrata,

In the infected vascular bundle the mycelium
shows as a slender colorless hypnae, trequently septate and
only slightly pvranched. No spores were found in ary of tne
sections ezamined.

Wollerwmeber * describes the fungus as 1f0110ws;
“ Sporodocia and a reduced pionnotees present, in masses
ealmon colored, the conidia of both being 3 septate up to 100%,
25-45 x 3.25- 4.5 microns; 4 septate up to 25 %, 5 septate up
to 10 % where tney are 40-50-x 3.5 4.75 uwacrons in size,
Sclerotia biue on steamed potarioes. A slight lilac odor on
ateamed rice, milk, ete. *

These characteristics were oOvuserved in the
cultural etudies made, the most characteristic growth veing
obtained on steamed vnotato estems.

All the following observations made on morph-
Ological caaractera and spore germination as well as the
drawings on Plates 1-6, were optained in every case from a
"Hoch-Kuitur® which has been observed by Drs. Wollerever
and Appel (1910) to ve the most cnaracteristic form vest
suited for measurement and study. In their work they show

*Wollemeber,.W. Phytopatn. 1913,
47.

that it is necessary to nave a pure culture satage which snows
the normal stages and if vossible all the stages ot tne fungue,.
Thus in their clasaification of the genus Fusarium they
difterenciate the different cultures as tollows. “An-Kultur *
is the original culture obtained vy isolation from the diseased
plant, a transfer of this culture produces the *Norm-Kul tur"
which can be kept by repeated transfers until a cnange or
degeneration sets in which they term the "Ab-Kuliur",. Again
the "yormeKultur * is divided into tne *“Jung-Kuiture * which
has conidia of abnormal size and forn, uneuite dle for stuay,
the"Hocn-Kui tur® which force after 8-14 days; in this culture
the greatest uniformity is prdauced and will tast for a mmber
of weeks, from this form we have the pvorly develoned later
forms known as the *AlteKuliur",

In the following studies the *Hoch-Fultur® form
was used and was grown on potato stems unlesa otnerwise noted,
In a study of the comparison of tne different cultures described
acove, it was found that in the"AneKuitur " conidia were
oroaguced very sparingly although there was an abumant mycelial
growth. The transfer from this showed abu ndant aporification.

In a study on poured plates of potato agar # 20,
it was found that the spores germinated in about 6 hours. The
mycelium wae produced rapidly, the co1onies being about 1] om.
in diameter at the end of 48 hours. The margin as a rule is
circular or neariy so. Tne diameter gradua. ly increases until

when the colony is about 2 weeks old it will almoeat entirely
48,

till tne plate. Examining the colonier from the under side of
the plates they appear to be formed by concentric rings of
growth; tne center of the colony appears as a ratner dense
tuft of myceliun about 2-3 mm, in height, surrounding the
central tuft is a zone of mycelium with very srort aerial
hyphae which is iteelf surrounded by another zone of slightly
taller hypnae tyan that in the center; cutside of tnis is
another one of short aerial hypnae made up of several concentric
rings, each ring being marked cy somewnat taller hyrhae.
Finally the entire cchony is covered with this t-11 grothn of
mycelium,

Tne mycelium appears as somewhat slender
cOlorless nyphae, many septate and much branched except at
the extreme edges. of tne colony wrere the nypnae pusn out witn
1ittle branching and no production of svores,. The mycelium

ie deneely filled witn gramilar cytoplasm. Microconidia

are proauced both aerially and in the substrata, macrospores
being produced in tne older nyphae and only aerially, and the
cnlamydospores are forued a little later.

On steamed potato plugs # 3 and a few other
vegatable media, blue sclerotia are formed in about one week,

The growth on all agar appeared white, wnile
on potato vlugs xept:in brignt daylight a faint rxalmon color
was croauced, On bolled rice the characteristic pink colora-
tion was observed and a slight lilac odor, and when a little

alkaiie was added tne color of the growtn turned a deep blue,
49.

On boiled prunes, the reduced pionnotes formation was found,
very little or no aerial hyphae peing rnroduced with an
abundance of svores and cnlamydospores. On many plates of

mitrient agar the pionnotes form was tound to occur.(Piate # 9.)

MICROCONIDIA.

The formation of the microconidia was best
observed in nanging blocks of agar or liquid media, used in
Van Tieghem ceiis. Tne microconidia are produced in about
24-30 hpurs after the spores have geri rated and the young
mycelium formed.

Tne first sign of spore tormation is a alignut
swelling along tne hypnae at various points,(Plate #5 ) it
was Observed usually in 24-34 hours. These small awei tings
rapidly elongate until the normal size of the microconidia
nas been obtained when it is cut off and immediately the
hyphae ovegins to push out past tne newly formed epore and the
same process ie repeated. In many cases tne microcunidia
seem to be cut off the end of small lateral brancues by a
constriction furrow, or the same process may take vlace on
the terminal hypnae. Tne entire overation trom tne cutting
off of one spore to the next usually does not take longer than
one hour and in many casea it nas been oObese:'ved to take |
Place in 45 mimtes.

The microconidia formed are usually more or

leas oval in shape, tnin walled, one celied and often sligntly
206

curved. They avry in size from 5.5°15.5 microns in length,
and from 1.7 - 5.5 microns in widtn. The most common size
observed on potato stems was about 7.6 x 3.8 microns,

The time required for germination varies
greatly in the different media and also for the different
individuals in the same medium. This is snown on the tavles
following. Usuaily in 7-8 hours 50 % of the conidia nad gern
inated but the hypnae are snort and not branched. In 30 hours
the vrancning was Observed but not extensively.

In all the examinations conducted on the
germination of conidia it has been Observed that on all media
there are always a few microconidia, up to 25 % that do not
germinate even aftcr 48 nours. It would thus seem that many
of tne microconidia cut otf are incapable of sending out germ
tubes and producing nypnae under the average cultural conditions
cited below.

The germiration of the microconi dia isa very
simole, (Plate #3.) they tirat swell a little and in some
cases become almost sherical, the ;erm tube ig then pushed out
usually from the end, altnough in some cases it wae observed
to take rnlace from the side and frequently from both ends,
al though when they are sent out from both ends they are found
to start at diitferent times. Later tne nypnae vranch out and

become septate.
Sl.

MACROCOVNIDIA

Tne macroconidia are found to vary greatly on
different media and also different individuals on the same
medium. On potato satems they usuaily appear as 1-5 septate,
moetly 3 septate. They are also found to vary in size on
tnis medium from 9.5- 38 microns in lengtn and 3.5 -7 microns
-inwidtn, the average for the 3 septate comdia velng about
27 x 3.8 microns, the 4 and 5 septate averaging lxrger and the
two and one sentate be: ng smaller. Tne conidia vary in shape
from nearly straight with slightly blunt ends, to a much
curved form with one end blunt and the other with the cnaracte-
eristic foot, or pedicellute base. This type of conidia,
flizntly curved, 3 septate , more or less sickle shaped, ana
with the cnaracteristic pediceliate base is the characteriatic
conidium used in the ciaseitication of this esrecies. All the
spores are thin walled.

Tne macrocoridia were never oOvoseerved being
borme below the surface of the media and therfore the Obser-
vation of the metrod of toruation was very ditticult. As far
as could be observed the formation t=zkes place at the end otf
snort laters] branches, the ends of wnicn are cut of1 by
constriction turrowse. Several nours efier being cut off the
septa begin to 1orm,

The time of germination of the macroconidia
varies greatly on difirerent media and from ultferent mecia.

In sterile distilled water germination usually bdexins in
52.

about 4 hours and in 7-8 hours practically all were germinating.
Tne germination of the macroconidia is more

complicated than that of the microconidia. Usually the end

cells germinate firat but not alwaya, sometime the germtubes

being sent out from the side of the epore, from the middle

celle. Any of the cells are capavie of sending out one or

more than one cerm tube and in many cases all of the cells in,

a 3 septate conidium have been observed to germinate, usually

however only two germ tubes :re sent mt and sometimes three.

The cell begining germination slightly swells and pushes out

@ germ tube which rapidly elongates and in 7-10 hours is

about 20 microns long, septation then teker place and in 32

hours conidia formation stzerts,.

CHLAMYDOSPORES.

Chlamydospores are found as large, one or two
celled spores, usually epnerical, smooth with a heavy wall,
and a brownish color, Tney are borne either ter:inally on. the
main hypnae or on its lateral branches, often intercalated
witnin the mycelium and sometimes within the conidia.( Bl.# 6 )
Severgl of them may be formed aiong the same hymae in chains.
Tne contents appear as heavy rounded masses of cytoplasm.

ne formation of the cnlamydoepore is firat
seen as an enlargement of tip of the nypnae or as a large
swelling in the hynhae, usuaily at the point of septation, The

swelling contimes until tne large characteristic form hes
 

-

 
536

attained. It ir cut off from the hypnae by crose walls before
it reacnesa ite mature form but does not always drop off. They
vary in diameter from 6-11.4 microns, the usual size being
7.6 microns.

The number of chiamydosrores produced varies
greatly with the different media used, but on favorable media
they are produced aburdantiy. The geru:ination of the chnlamydo-
epore is simialr ir process to that of tne microsnore, a simple
germ tube being sent out eitner from one end or from both, and
it then proceeds the s-me as the hypnae from the other spores.
In distilled water the germination gegins in abcut 5 nours, at
the end of 30 hueures they were siigntly brancned and as in the

case of :.icroconidia mary of tnem failed to ¢-rminate at all.

SCLEROTIA.

A nodule like mass of plectenchyma with a rougn
surface wae tound to grow On various of the vegetable media.
On potato plugs they were found as blue green sclerotia and
also on boiled white beans, sweet potato plugs and carrot plugs.
In the latter they appeared more greenish, Tney develope at
the surface of the kedium and are partly covered over with
- the -hite mycelial growth. Examined under the microscope they
appear only as tightly woundmasses of my’ elium, seeming to

tunction as the resting etage.
 

So ef =,
54.6
CULTURAT, SIUDIES OF VARICUS STRAUS.

This experiment was conducted with the
following objects in view.
1. A study of the cultural characteristics of F. oxysporum
on different media.
2. A comparative ctudy of the difterent strains of F. oxysporum
isclated from potatoes euspectec Of Fusarium wilt which were
obtained from tielde examined in different parts of the state,
to show that the organism was identicalin the mme:oue fields,
and to substantiate the diagnosis made in the field from
which the data on field obervations were compiled.
3. A comparative ctudy of cultures isolated from tubers showing
a deep infection and from tubers snowing a slight discoloration
of the vascular ring.ior only a few mii:limeters,
4. A comparative etudy of culiures ieolated from tuoers having
a white mycelial growth on the outside of tuber infected
with F. oxysporum and cuiturer tzken from the vascular ring.

In the following data all the media ig numbered
and formulae of them is given on pn. All cuitures were kept

at room température in a norinern light.

METHOD OF OfFTALNING DATA.
The size of the spores was taken by observing
several fields in each slide, several slider being made from

each culture. The size of the asanores varied so much that it
mer

wae impossivie to ootain a talir average that would be a true
indication of the size of the spores on the various media,
theretore only the maximum and minimum length and thickness

is given. tn the same way the mmber of macrospores which are
One, two or three septate is not given in percentage as it

was not possible to make large enougn countea to be able to

give a definite percentage. However by observing three or

four fields on eacn slide under iow power it was tound possible
to make a fairly accurate eatimation of tne »vredcminznt

method of sentation, accordingly they have been comvariti-ely

estimated in the following data,

SOURCE OF THE DIFFERENT “TRAILS USED.
1. Isolated from notatoes ovotai ned from farm near "aw Paw
Van Furen county. Tnese showed a slight infection, the brown-
ing of the vascular ring being only about ¢ inch deep.
2. Isolated from slightly infected potatoes on College farm,
browning on:y 1/8 inch deep.
3. Isolatea from po.atoes from the same field as 1 but with
a deep inrection.

4,Iso0lated from potaioes trom Stonington, Delta Courity. nese
were infected with late blight, a ary rot stage had set in,
and wnite my:elial tufts were developed on the tubers when

kept at room tempefature.
56.

5. Cultures made from the witnered roote of infected
potatoes that had been sterilized in HgClo and sprouted in

eterile sand in large moist enambere in tne lLavoratory.

The ages of the various cuiturer used in tiis

work varied greatly, they were as 10llowe:-

#1.-14 days old grown on media # 3- Potato pluga.
2.2 4 months, 9 daysa-- " ° " *20- " agar
oe a 4° no n #8 3
4.-3 °* a on "#90

5.- 2 rn 24 n fn 0 “ " 3.

 
57 »

NUTRIENT AGAR # I.

 

Height
No~--Growtn-- Density-- Color in lignt-- Remarks,

 

 

 

I-- 2.5 mm.- moderate-- white growth slow,feathery.
Qe 8. © very dense- . " faster, "

Je- 8 " " "

4-- " moderate " .

5e- 7 um- " n "

No-- Microconidia-- Macroconidia-- Cnolamydospores.

 

 

 

I-- moderate very few. present,
5.5-13.3 x I.7-5.5- I -3 septate
mostly I *
II.4 x 3.8 to
22.8 x 5.2
2 many, few few- 7.6 diam,
7-6 x 3.8 to I-3 septate
14.4 x 5.5 most I "
9.5 x 3.8 to
20.9 x 5.5
3-- 0 ” | n
4e- " few I-3 septate .
most I °
36. ~6x3.8 ,?
x 7.6
San " 1ew I-4 septate .
most 1

II.4 x 3.8 to
18. x *

 
 

 

 

 
No.

PRAR AGAR #I0.
Height

Growth---Density-- Color in lignt-- Remarks.

 

characteristic foot.

 

 

 

 

I - 2m, - Sparse - White -macro & microconidia equal.
2 o e ® R @
3- * " " more macro than microconidia,
4.2 " " " macroconidia large, thicker.
5- " very sparse * tew large macrosnores.
No. Microeonidia---Macroconidia---- Chl amy dosn ores
I-- mumerous mimerous-26 x 5.5 mmerous
7.6 x 3}.8microns- many 3 septate
few 2 .

gee R " ”
3<- " " "
4e~ " mimerous 38 x 7.6

many 3 septate

few2&I " "
Fen " t ewe "

many I &2 sepate

14.2 x 3.
few 3} septate

22.4 x 3.8

 
PRUNE AGAR # II.

 

 

 

Height
No. Growth--Density--Color in light-- Remarks,
Ie-- ] om.-- very dense-- white few spores.
2-- * " " small macroconidia
j-- C8 ° " large "
4-- * . . larger, thick, straight.
See = " " few sma:l macroconidia.
Now- Licroconidia-- Macroconidia-- Chlamy dospvoresa,
I-- very few very few numerous.
7.6 x 3.8 mostly 2 & 3 septate 7 mic. diam.
12.5 3.8
2Qe- mary mimnerousel4.5 x 3.8
7.6 x 3.8 mostly 2 septate
tew I & 3 °
mmerous-28 x 3.8
je ° mostly 3 septate "
few2&I *
slender, sickle shape
‘hoo e numerous=-30 x 3.5 .
mostly 4 septate
few 2 & I .
very tick
5- = n few-- II.4x 3.8

mostly I septate none seen,
few2&3 *
60.

OAT AGAR # I2,

neaght
No--growth==- Density-- Color in lignt-- Remarks.

 

 

 

I-- I cm.=- moderate- White mostly microconidia
3-2 " dense ° macro, more mmerous,iarger.
hee ” moderate . . thicker, blunt.
5e= omm.-very scarce °
No-= Microconidia-- macroconidia-<- chl amydospores.
I-- mmerous very few-I9 x 3.% numerous
7.6 x 3.8 mostly 2 sep.ate 8.6 microns diam,

few3 &I1 *

3-2 " mimerous=-28 x 3.8 "
mostly 3 sepsate
few4&5 *
very * 2&1 *

4-- " numerous-25.5 x 7 "
moestiy 3 septate
tnick, blunt ends,
no foot.

=~ " } numerous=-31.5 x 3.8 .
mostly 3 septate
No--

él.

LETTUCE AGAR # 14.

Height
Growth--Density-- Cotor in tight-- Remarks.

 

 

 

I cm. very dense white
@
td 0 ”
” ° ° faeroconidia tnicker,

 

Microconidia-= Macroconidia-- Cnhlamydospores.

a_i

 

miuervus numerous numerous, terminal
7.6 x 3.8 many 3 septate IIl.4 diam.
: 15 x 3.5
° * .
few 4 septate .
® ° 6 @
. rune: ous very mmervus
mary I septate
19 x 6

few2&3 "
23 x 7

 

 
62.

STEAMED POTATO STEMS # 2.

 

Height
No--growth--Density-- color in light-- Remarks.

 

I-=- 4 mm.-- moderate-- white equal no. of micro &
macroconidia,

Le ° " more micro.tnan macro,

3-2 «(C8 " “ macroconidia smatler.

4-- * " " more macro, tnan micro.

slender, more curved.

5-- " 0 n n

 

Norw- Microconidia-- hacroconidia -- Clamydospores.

I-- moderate 9.5-38 x 3.8 ‘umerous
IIl.4 -5.5 x 3}.8-- numerous
I=-3 septate
most 3 *

 

 

 

Q-< " ° very ;umerous.
most 3 septate
few 4& 5 *

few very few.
13.5 0626.5 x 3.8
I - 3 septate
most I .

4-- " mmerous-15.2-30.6 x 3 "
mostly 3 septate
slender, more curved.

ee mumerous very few, numer us.
mostly I septate
small.
STEAMED POTATO # 3

Height
No.- Growth-- Density-- Color in light-- Remarks.

 

 

 

 

Ie- Iom. very dense--wnite to lignt salmon blue sclerotia,

Goa " « ® 0
hea 0 " %3 r
5e- . snarse ° no scierotia.

 

Now- Microconidias-- Macroconidia-- Chlamydospores,

 

 

 

I-- numerous numerous numerous, terminal.
9-7 x 3-3.8 mostly I septate
11.4-22.8 x 3.8

Qeo= ° mimerous .
aver. 4.3 x 3

3-- " a few.
mostly 2 septate
few 3 "
II.4 x 3.8 to
22.5 x%¥ 7.4

 
64.

BO: LED CARROT. #13.

 

. Hergnt
No--Growth-- Density--Color in light--Remarks,

 

 

 

spore production profuse

I-- I cm.--very dense-- wnite-- greer-olue sclerotia,
macroconidia small
@

 

Cen " " "
3--— si ® dense ” "
hee 0 a " 0
macro. iarger, thick, straignt.
5-- ~=Cl® " " " long, narrow, curved
Sclerotia present.
No-- Microconidia-= Macroconidia-- Chlamy aospores.

 

 

 

I-- very mmerous-- very few-14.4 x 3.8 present.

726 x 3.8 mostly 2 septate
2-- " " "
3-- " " @
hun " nmumerous-21 x 7.6 “

most 2 septate.
thick blunt end.

j-= mary mmerous 3I x 3 "
mostly 2 septate
long, thin, with
a distinct foot

 
65.

BOILED CORN MBAL # 4,

 

Height
No.-Growth-- Density--Color in light-- Remarks,

 

 

 

I-- I cm.-- very dense= light pirke- mycelium very gramlar
no typical macroconidia, .

Da = 0 " " | "
3-- " " "0 "
he . " " more mcroconidia, thicker.
See C8 . red .

 

No-= Microconidiaes iacroconidiae- Chlanydospores.

 

 

 

I-- numerous very few very few.
5,527.4 x 3.8 I- 4 septate
most I *
II.4-26.2 x 3.8

2-- . most 1 septate "
3-2 0 a "
hee " numerous "

l-3 septate
moat I "

aver. 19.6 x 7.6
very thick, bliunt ends.

5-- " same as #3
66.

STEAMED BEAN STEMS # 5

 

Heignt
No--Growtne-- Density=-- Color in Light-- Remarkea

 

 

 

 

Ie-- 4om, dense-- Wwiuiite
Dae « e "
3-2 ” ” ”
4-- 2mm, moderate .

 

No-- Microconidia-- Macroconidia-- Chlamydospores,

 

lee mumerous mmerous mmerous
72-5 xX 3.8 #£x%I-3 septate
most I *

II- 19 x 3.8
straignt, blunt.

2-- . . .
3-- " " 1 ewer,
4-- tnicker rumerous "
most 3 septate
26 x 7.6
few 2 septate
18 x 7.5

few I septate
II x 7.6

 
67.

BOILED WHITE BERANS # 6

 

Height
No--Growth-- Density-- Color in light-- Remarks.

 

 

I-= I cm. very dense white blue green sclerotia.
Dee OR " " "
je 8 " " e
fue (8 " " “
5-- 5 mm. scarce . °

 

No-- Microconidia-- Macroconidia-- Cnlamydospores.

 

 

 

[-- mimerous f ew rumerous
7.6 x 3.8 most i & 2 septate
few 3 .
I5 x 3.8
Qa " : @
3-- ” e @
4-- . mmerous, thick few.

many 2 septate
few3&I1 *
2.1 x 6.5

5-- " same as # 3

 
68.

STEAMED LUPINE SPRUUTS # 7

 

Height
No--Growth-- Density-- Color in light-- Remarks,

 

 

 

I-- 2mm, moderate white
2-- * aense .
3-- 8 " "
few a "
feo * scarce "

 

No-- icroconidias= iacroconidia-- C hlamyaospores.

a

 

I-- minerous numerous very few.
7.6 X 3.8 I- 3 septate
most I "

I5 x 3.8
Qeoe ® ” *
3-2 ® ® @
hon " ° occasional
most 2 septate
2I x 7.6

Se< f ew very tew none sen,

 

 
STEAMED PARSNIPS # I5

 

Height
Noe-- Growtn-- Density=-- Color in :ignt** Remarks.

 

 

 

I-- 4 om, moderate wnite myceiium with many
vacuoles,

2-- Icm. very dense . .

3-- e ® ° e

daw " " e "

5-- e ” " °

 

Noe=- Microconidias-=- Lacroconidia-- Cnlamydospores,

——--

 

I-- mame.cous mimerous noderate
9.6 x 3 mostly 2& I septate
19 x 3.5

o-e « * mmerous
3-- ” e e
hea " °

thicker 19 x 7 °
Gen . 3 septate

26 x 3 slender .

 

 
 

 

 
79.

BOILED RICE # I6.

 

Heignt
No-- Growtn--Density-- Color bn tight -- Remarke.

 

 

 

 

I-- 1.5 cm. very dense pink jilac odor, pi:k tunns
biue when alkalie is
added.
Dow " " " «
3-2 ° * @ e
heaw e 0 ® *
f-- . .

No-- Microconidia-- Macruconidia-- Cniamydospores.

 

 

 

l<-- mumerous very few numerous
7.6 x 3 mostly 2 septate many terminal
19 x 3
2o- . numerous very rumerous
3-- . . .
4e- " many, thick, .
ma:tly 2 septate
25 x 6

See " same as # 2.

 

 

 

 

 
71.

STEAMED SWEET POTATO # 17.

Height

 

No.- Hrowth-- Density-- Color in tight-- iiemarks.

 

I-- 4mm very dense

2-2 ® .
j-- 8 ,
hea @ "
5-- .

 

 

reddisn gray

 

Nor=- Microconidiase- Macroco:iadiae- Clamydospores,

 

I-= rmmerous

7.6 x 3
Dan °
3-- @
how e

 

tew, 19 x 3.8
mostly 2 septate
few 3 & l .
mimer ous °
few .
maiy 3 septate
19 x 6.

sa..e as # I,

 

 

mimnerous
many terminal
726

BOILED LUPINES # 8.

 

Height
No.- Browthn-- Density-- Color in lighte- Remarks.

 

 

 

Ie- 2 1M, scarce white

3-- 0 e "

 

BOITED PRUNES # 9.

 

I-- 2 mm, dense brownian white-- profuse pionnotes
granulated cytoplasm.
Dean " ” r "
3- o " " @ ®
LUPI IRS

Nowe Licroconidia-- macroconidia-- CUnlamydospores,

 

 

 

 

I-- numerous mimerous none seen
7.6 x 3.8 most I & 2 septate
few 3 "
I5.x 3.8
cigar snare
3-- ° ° present, many terminal,
PRU NES.
I-- mumerous few, most I septate merous
726 x 3 II x 3.5
Ian ° ® "

3-2 " ® a

 
73

DISCUSSION OF DATA,

From the above data it appears that all five
cuitures are identical. While they vary in some extent in the
mumber and size of the microspores, macrospores and chlamydo-
spores, it is safe to say after a careful stuay of the
ditferent cultures in wnich the mycelial growth, spore
production, color of growtn and especially the average size
of the spores and their torm, noting the presence of the
characteristic foot vresent in the macrospores; that these
various strains are all identical witn culture # 1 which
was tne atock culture of F.oxyecorum, What small diferences
are found can be accounted 1or vo some extent by the great
error possible in examining sucn a large mumber ot apores
comparatively , especially when only tne maximum: and mininum
size is given. Tne color of all the cultures was the same on
all tne respective media, |

According to Wollenwever i.c. F. oOxysvorum
produces a characteriatic pink color and lilac odor on boiled
rice, tnis was found to be true in every case. When a strong
alkali was added to this medium the pink color of this
mycelial growth cnanged to a brignt blue,

The blue sclerotia Ovserved on potato plugs
were tound in every case. Tnese were also observed on Sweet
potsto plugs as well ae carrot plugs and polled wnite voeans,

Tue few ditterences that are observed between

the several ‘ultures are probably accounted for to some extent
74.

by the great variation in the age of tne cultures from which
the transiers were made, the variety of the media the original
cuitures were grown on, as well as the possible difierences
in the moisture content and the composition of the substrata.
There is also a possibility o1 ditferences in cultural cnhar-
acteristica being produced depending On wetner tne culture
was started from mycelium, microspores or macrosvores, in
most cases probably ail three were used,

The study of the results obtained by growing
the same strain on different media bears out conclusively the
statements made by Wollerweber 1.c. and Smith and Swingle l.c.
that the fungus grows readily on a wide vuriety of media. It
‘varies greatly in density,color, height of growth, and the
Mmumber, eize and torm of microspores, macrosvores, and chlamy-
dosvnores according to tne subctrata and enviroment. The
growtn on vegatable media seems to be the most favorable for
@ profuse growt: and characteristic sporification. Potato
plugs and especially votato stems are provanly the best media
for this fungus.

The cultures made in the above experiment
were isolatea from potatoes tnat varied greatly in the depth
of infection from 1/8 of an inen to a very deep discoloration.
The possibility of the slight discoloration being Fusarium
wilt has been questioned many times put the above results
point out that the organisms obtained from both the slight

and. the deep infection were the same. The same resulta nave
756

also been obtained in a atudy of other cultures isolated

from such slightly infected tubers, a large mumber of these
have been made in the laboratory from tubers obtained from
fields where the actual field conditions had been observed,

and in practically all cases these cultures proved identical
with the F. oxysvorum. In the few cases where it waa impossible
to obtain cultures from the alightly infected tubers the chief
cause was the presence of otner Organisms which had worked
their way into the stem for a few milliueters,

When these slightly infected tubers were
examined in the field work they were diagnosed as F. oxysporum
if accompanied by a browning of the vsscular ring of the sten,
However mmerous sets of two tubers esch, from two infected
fields on the college f-rm, one of whicn snowed a slignt
intection and the other a deep browning of the vascular ring,
brought vack greatly varied answers when sent out for diagnosis
to patnologists at otner stations. This was done in an effort
to determine how the different depths ot browning would be
diagnosed in the ditferent states.

While there is undoubtedly a grave cause for
doubt when only a slight browning of the tubers is found, it

appears to the writer that when accompanied by the charactér.

isticbrowning of the vascular ring in the stem for only a
few inches above the surface of the ground and extending

downwards to the tuber, these symptoms may be safely diagnosed
76,

as Fusarium wilt caused by F. oxysporum, This statement is
based on the large number of isolations mace from such slightly
intected tubers from varicus parts of the state, all of which
appear identical with those given in the above data,

In examining Culture #4 we find that the same
morpnological characters are present as in the other cultures,
while this culture was isolated from the white mycelial tufts
on the outside of the tubers and the othera were isolated trom
the vascular ring.

Tiis would appear to bear out the atatements
made by Smith and Swingle 1.c. that the fungus is «apable of
penetrating from the vascular ring of the potato tuber to the
epedermis or tne tuber,

| According to Wollenwever l.c. F. oxysvorui is
strictly a vascular parasite, yet this work would indicate
tnat there is a poasivility of tne tungus spreading through
the tuber to the surface and then producing the white mycelial
growtn in a case where the tuber is attacked by another
disease which produces a decay of the tissues between tne
vascular ring and the evedermis,

Simitar results were obtained as the result of
cuitural and infeciion experiments by Manns il.c.

In any case it will take a good deal more
careful investigating with particular study as to tne nrogress
of tne mycelium in the tuber as well as careful cultural and

inoculation work to prove that this fungus sends its nycelium

theough the tissue to tHe epedermis,
77.

SPORE GERMINATION AT DIFFERENT TEMPER.uU RES.

Tnie data was obtained by germinating the
spores in distilled waver in Van Tie.gnem cells. The various
tempertures were obtained vy us¢ying the same apparatus as
that used tor the determination of maximum and minimum growth.

Spores were obtained from a stock culture on Potato stems.

Nos Temp.- 7 nours-- IO nours-- 24 nours.
I-- 8 C. -no growth-- no growth no .rowtn
2--I0 * " " few macroconidia
3--14 * -50% thacro. 80% macroconidia all macro
IO micro, 50 merocondia most micro.
tubes short germtubes 20 microns.
4--18 * e " longer growth
5-24" . " mich branched,
tubes 20 mic. tubes long
6--30 * no growth no wrowth few macroconidia
7--38 * " " no growth.

It is seen from tne above data that from I8 to
24 degrees C. ie tne most favorable temperture for. the best

spore germination, With a gradual decrease above ard below.
78.

GERMINATION OF SPORES ON VARIOUS MEDIA.
All esvorees obtained from a stock culture on
potato stem and germinated in Van Tieghem cells at room temp.

Hours. ‘Condition at tne ena
Medium Kind of spores- I10%50%-All- of 24 hours.

 

Single distilled-Macroconidia-4- 5- 6- many nicroconidia not

water Microconidia 4=- 7e--- germinaced, Zerm tunes
short.
Double " Macroconidia 4= 6- 9- Germ tupes of macro,

Nieroconidia 4- Je--- much branched, witn
epore tormation,
0

Tap water macroconidia 4- 6- 9
Microconidia 4- 6+ <-
Giycerinated Macroconidia b= 7- &- " no
Nutrient agar Nicroconidia 6- J---=- spore tormation. 275%germ.
Glyceri rated Macroconidia 5- 6- 9 spore forijation
Beer oroth Kieroconidia be Jee-- 75” germ.
Beef broth waeroconidia 6 6 & not pranched  epores
Microconidia 6 7 ---- 75% geri. formed.
Nutrient agar tacrosonidsa 5 6 8 much cranched, spores
Microconidia 6 / e--2- 75% germ. tormed
Synthetic agar Macroeonidaa 6 7 & . " no spores
#25 Microconidia 6 7 ---- 1ormed.
Synthetic media: Macrocunidia 4 6 7 " | "
#26 Microconidia 5 7 e#--<-
Oat agar macroconidia 6 g 8 * spores
Microconidia 6 one tormed.
Hard Potato Macroconidia 5 6 7 Littie no spores
agar Microconidia 6 7 --- vrsanching t1ormed.
Cucumber agar kacroconidia 5 6 7 much prancned-spores
Microconidia 6 7 --- formed,

-
 

79 «

The epores were obtained trom cultures on

various media 5 weeks old, germinated in distilled water

Q
in Van Tiegnem cells, at room temperture.

 

Hours. Condition at end

Media Kind of spores-10%-50%-All=- of 24 nvuura

Nutrient agar- Macroconidia 6- 7- 8 Mucn brunched spores
Microconidia 6 Iife= Mary not germ. § toruied.

Pear agar macroconidia 4 6 7 slight brancning
hicrocomdia 8 9 ---

Prune agar Nacroconidia 7 II 24 . "
Kicroconidia 9 24 ---

Oat agar Nacroconidia 5 6 9 Kuen brarened 8
Microconidia 6 24 e---

Cucumber ager iacroconidia 6 g & " "
Nicroconidia 7 oo

Boiled prunes \acroconidia 8 9 " "
Microcoridia 4 7 ----

Boiled rice wacroconidia 5 6 9 " "
Kicroconidia 6 7

Potato etemsa :.acroccnidia 4 5 6 " ,
Microconidia 4 7 <=

Potato agar Macroconidia 6 8 9g " "
Microconidia 7 8 ---

Carrot plugs wacroconidia 6 8 9
Microconidia 7 II --- " "

Bteamed potato Macroconidia 6 8 9
Microconidia 4 7 -=-- ° .
80.

SUMMARY OF SPORE GERMINATION TESTS.

In the preceeding tavies it is snown that the

germination of spores from difterent media vary as well as
epores on different media, |

Tne svores taxen from potato stems seem to
have the greatest power for rapid germination, both for earty
and total germination. In most _ cases the spores taxen from
vegetable media seem to nave greater vitality tnan those
from agar,

In the data on germination on various media
we find that for the most rapid germination once distilled
water is the best while liquid synmtnetic media # 26 starts tne
germination of macroesporesa at about the same time but the
total germination is a little slower.

Since this experiment vas conducted it nas been
found that Kmdaonts full mtrient liquid meaia # 27 will
produce tne same or perhaps sligntiy bettei resuits tnan
distilled water, also causing a more rapid growth of the

germ tubes and tne production of conidia.
81.

NAXI;2Z0M AND MINI UM TEMPERATURES FOR GROW-H.

The range of temperatures at which tne organ-

ism groes best was tested by growing the fungus on potato

Plugs and mtrient agar as follows:-

Exp. 1. 8 test tubes were used containing mtrient agar. In

each was placed a sterile thernoueter to record the actual

temperature,

the bulb of the tnermometer being placed near

tne point of inoculation on the agar. These tubes were placed

in an apvaratus consisting of a galvanized tin box about 2

inenes deep filied witn water, one end being in contact with

the ice box the other with a similiar box containing water

kept at a constant temperature by means of an electric neater.

The cultures were thus kept at alair.y consiant temperature,

witnin an error of 1 uegree 1n 6 hours.

Temperature --

 

l1.- 24°

2.- 28
3.- 30
4.- 33
54-34
6. 36
7.- 38

but no

2 days
C. slight
" very "
" n "
" e 0
" no. growtn

 

3 days 4 days.
medium abundant
elaght mea ium
” L
0 "
very "* giignt
no growtn very *
# . e

 

8

Otner cultures were tried at nigner.temperawures

growth was obtained in any case,
82,

Bxp.# 2. The same test as the above was also conducted
using potato plugs as the mecium. Tunis was carried on ina
smaller anparatus than the previous test but with a greater
range ot temperature. It consisted of an air chamber anout
6 inches deep and 3 ft. long, throughly insulated, one end
oveing in contact with an ice box the other with a similar
box contain. ng water kept at a constant nigh temperature,
Tne air chamver was divided into 9 comvartments each about
3 inches in widin, The tubes stood upright, each with a

thermometer next to it. All tubes were of the same size and

 

 

 

 

 

tnoiek ness.

Temperature 3 days 5 days 1 week.
#1. 7° C. | no growth no growth no growth
ee 9 * ° slight slight
32°12 " ° . medium
4.-18 * slight medium avundant
54-24 . " a "
6.-294 " very siight slight slight
7.237 e * ” e

None of the cultures placed at nigher temperature

produce: any growtn.

 

 
 
83.

Exp. #3. The same test was agin repeated by using potato
stems, each tube being kept at a constant temperature in

incubators and thermostats,

 

 

 

 

 

Temperature 2 days 4 days 1 week.
1.- 5° C, no growtn no growth no growth
2.-14 * . slight "medium
3.223 * meaium abundant abu ndant
4.-294 * very slight slight medium
5.234 * " " slight
6.-374 " no growth no grow tn _ no growth,
RESULTS.

All three of these experiments snow practically
parallel re-ults. We find that the fungus groes pest in culture
at a temperature of from 18-24 degrees. At 14 degrees the
growth is slow, gradually decreasing with a decrease in the
temperature until at 9 degrees tnere is very slight growth.
Tne fungua was not ovserved to xrow at all at 5 degrees.

Above 24 degrees the growtn became slower and siower as the
temoerature wac raised, ceing slow at 30 degrees with only
avery siignt growtn at 34 and 36. At 37 degrees the culture
did not grow in any case.

Tne Low temperature at which tnis fungs
ceases growtn may possibly be che cause Of the inability of

tne fungus to penetrate into tne tops of the plant.
 

THERMAL DEA: H POINT.

The thermal deatn point of the organism was
determined as follows.- Test tubes of equal size and thickness
18 x 150 millimeters, with thin walls were used containing
nutrient agar # 1. A large water bath was used, the temperature
being kept constant by regulating the flame of the he ater
with a thermo regulater. Tne water in the bath was kept at
an even temperature by revolving fan kept in the vottom of
the water batn and connected with a emall mouor. Two test
tubes were always used together, one being used as a check
On the temperature. A thermometer was placed in the agar in
this tube and the temperature tnere ovuserved was taken as the
temperature of the inoculated tube placed adjacent to it.

The cneck tube was of the same thickness as the testea tube
and contained the same agar. The second tube was inocu! ated

by transfer from a stock cultu re, after tne agar in the tube
nad remained constant at tie temperature to be tested for

10 minutes, Tne tuve was then suojected to the temperature

to be tested for 10 mimtes and then poured into a petri dian.
The firet tuber to be teated were sub) ected to a temperature
of 36 aegrees, and tne temperature was tnen raised one degree
for each successive test until a temnerature was reacned that
would ki1tl tue fungus.

RESULTS: - It was found that wnen the svorese were subjected
to a temperature of 614 degrees C. for 10 mimtes, germination

uid not take place,

 

 
85.
POISONOUS BY PRODUCTS OF ‘tn FUNGUS.

Owing to the fact tnat- many cases of tne wilt
have been ovserved wnere the foliage was entirely witited,
witn only a slight trace of mycelium present in the mtem and
roots, the nypotnesia was brought : orward that the wilt may
be due to a secretion of the fungus as well aa to the
invasion and blocking up of the water tubes by the mycelium,
Accerd ngly teste were conducted as follows,

A euspension ot the fungus wae made by grinding
up a stock culture of the fungus in water, this was then
filtered through a Berkfeld filter. About 30 c.c. of tne
filvrate was then vlaced in lire teat tubes 1.x 8 unches,
and the tops of healtny brancnes were cut and niaced in tnese
tucesa of liquid to be tested. In the s me way similar brencnes
were inserted in tubes containing sterile ater and anotner
set in tubes contaimng a sterile water suspension of the
tungus. All the tuves were kept inthe greennouse under the

same comitiones eacn bel ™ tig..tly plu:.ged.

3 daya 1 week,
1. Filtrate sligntly witited badly wiited
Oe " " "

3. spore suspensiagrm ovadly wi: ted--- completely wilted.

4. " « @ ®
5. Sterile water no wilt no wilt
6, ° “ e.

It 1s seen that in three days the brancnes

Imiersed in the snore suspension snowed the first signa of
86.

wilt crosely followed by tne tubes containing the fiitrate,
the cnecks remaining :ealthy and upright. At tue end of one
week the branches in the spore suspension were compietely
wilted ana dead, while the ones in the filtrate were badly
wilted and drooned over, tne cnecks still remaining healthy.
In ten days the cnecks had also wilted down owing to the water
in the tubes having been completely taken up by the transnira-
tion from the leaves, At this time ine amount of ‘liquid in

the tubes containing spore suspension haa been but very
Sligntly reauced, wnile in the tubes containing tne tiltrate
less than half of the liquid remained.

Upon examination the checks ahnowed no presence
of fungus growth, the wilt being entiely due to the drying
out of tne water in the tubes, The branches in spore susper-
eion when cut open showed the presence of the mycelium in the
water conducting tissue for an inch above’ the level of the
liquid, the loss of the tiquid probably being due to the
transpiration ot the plant before the mycelium in the water
tubes had berome dense enough to entirely plug them up; but as
the wilt began earlier and warm more rapid toan that of the
til.rate it would seem that it was caused by a combination
of both the mycelium invasion of the water corducting tisaue
and a poisonous byproauct secreted py the fungua,.

In the brancn kent in the filtrate no funsus
presence was noted and as tnere was satill a large amount ofr

liquid in the tube after tne top had completely wilted, it
87.

would seem that the wilt was probably due to some poisonous
secretion by the organism.

More complete work with tnis problem is to
be carried on as it appears to open up a new fieia of experiment
with tne Fusarium wilt.

W.H.whetzel nas reported verpvally to Dr. Bb. A.
Bessey that in working a similar experiment using the fungus
that causes the Verticillium wilt oft trat particular plant
ne was working with, the Ginsing, that he optained resuites

similar to the above mentioned experiment.
——wa— ee

 

 
88.
INFECTION EXPERIMENTS.

While a great deal of study nas been given in
the tast few years to Fusarium oxysporum very few arti: icial
infection experimente ave been reported.

Smith and Swingle l.c. report the injuries
to the plant caused vy a Fusaria in the vascuiar ring of the
seed piece, but they do not report inoculation experiments,
aithnougn their work has ofiven been so interpreted and has
even been referred to in literature as such, for example,
Duggar* says, * Smith and Swingle nave by careful cultural
and inoculation experiments demonatrated the causal connection
of a Fusarium with these types of the discase."

Wollenwever **eatabiianed the patnogenicity of
the fungus stating, in reference to F. oxy ap-rum, that," The
patnogenicity of tnia fungus established py Smith and Swingle
has been confirmed oy this autnor gor the strain uvon wiien
the diagnosie given above is based."

Manne * revort: suceasful inoculatione vy
wounding the roots, but ne also states that * The organism is
however, productive of imection in the avsence of any root
disturbance or stem injury, as wae shown by a number of
exnerimenta.* but ne s.ates that inoculations vy means of

* Duggar, B.M. 1909, p. 317.

** Wollenwever, H.W. Phytopatn. 1913, p. 42..
**x* Manns, B.F. 1911, p. 317.
ag,

injuries brougnt about the moat rapid infectian. His 1 fection
experiments however were conducted by hrowing the plant in
* sick soil " whicn he repor.s produces @ greater infection
tnan tne use of pure cultures, He states * The di-ease came
on much more detinitely u:der sick soil rnfeetions than it
did wiere rure artificial cuitures were used witnout incisions
or root injury. The great difference between sick s.il infect-
tion and that from pure cultures or even internal seed
infection, is that in the use of sick soil the roots are
attacked at practically every point, wnile with pure cultures
or seed internally infected, tne fungus attacks only i: close
proximity to the main root wnile most of the secondary and
root nairs remain healvhy."

The chief ovjection to these experiuents is
tone fact that the * sick soil * will probpably contain a great
number of organisms otner than that of tne fungus in question,
In the following infection experiments in the greenhouge,
tnese possibly u::dersirable conditions have been eliminated
by using tnorougenly saterilized soil and inocurating it witn
F, Oxvsporum, leaving the sick soil exneri ente to be conducted
in the field.

Toe experiments were conducied using various

methods of inocutations, as foblows.

1. Inoculations of seed linge on healthy and injured roots.
2. Inoculiation in gaoil of pure cuiture with roots sound.

3. r * * " 6 " " " injured.
90.

4, Inoculation in soil of pure culture with rootea sound and
also with tne addition of Rnizoctonia,

5. Inocuiatea vy wounding the stem and inserting mycelium
and spores of a pure culture.

6. Inocuiate by plucing the stem end of infected tubers in
the pots with sound roote.

7 « ° * ainjured roots.

INFECTION OF SEEDLINGS.

Tnis experiment was conducted to deteruwine
the ability of the fungue to invade sound roots of seedlings.

In using seedlings it was real.zed tnat the
natural conditions of the fieid were not opntalrned, but there
were several distinct advantages in this metnod, such as tne
exclusion of all fungi from the seed by ‘nore effecient
sterilization than could be obtained in using mature tuvers,
a€s well as the perfect sterile conditions of the soil that
could be obtained vy using Large test tubes 1 x 8 inches,
and alao tne prevention or injuries to the roots,

For tnese experimerts potato seed were obtained
trom Wm. Stuart, Urited States Deptartment of Agriculture,
from Houlton, itaine. various methoda of sterilization were used,
as it was found to be very diliticult to opotain nearly perfect
eterilization without injury to the seed.

freatment with 95 % alcohol tor 10 mimtegs,
concentrated sulphuric acid for 15 minmiter and 1-2U0 mercuric

chloriae tor 14 -3 mimes resuited either in the death of
91.

the seed or very “oor germination.

The seeds used in this experiment were treated
by soaking the seed overnight in running water, was:uing in
distilled and aterile water and tnen dipping in 1-200 mercuric
enjoriae for a few seconds. inese were tnen placed on nutrient
agar and allowed to germinate, Practically all gernasinated and
the few seed that showed contamination were removed. Tre
remaining were placed in various tuves and grown in the
greennouse,

Seed were placed in large test tubes 1 x 8
inones, of svil extract agar # 28 and after a growth of several
inenes nad been obtained they were inoculated by transi ering
&@ small looptul of mycelium and spores from a stock cuiture

to the surtace of cine agar.
Examined 4-19-15-

lee inoculated 4-8-15, ----------- the seedlings were all

2. " . dead, with a neavy mycelial
3-2 " . gZrowtn covering the etem
4, " " and great spore tormation.
5 .- O ry |

6.-cneCck ----- Oren cee wen ewer en nn- good nealt y .raown, 3
72° * lnenes in neignt.

8.5 8

Ge- =—*

 

DISCUSSION OF RESULTs OF SEEDIIAG. INFECTION,

In Experiment # 1 all the seediingea inocu. @ted
92.

with the fungus died inside of 10 days while the checks still
remained healthy. The roots were not sectioned and stained so
that the presence of the fungus in the vascular system of tne
seedlings was not determined. It was attempted to cut seciions
with the freezing microtome but owing to the profuse mycelial
growth and the luxurient spormfication which entiriy covered
the seedlings it was impossible to get good resuits.

Tue deatn of the seeuii ngs may nave been due
to tne invasion of the water conducting tissue , or possi vly
to a poisonous byproduct of tne tungus Or simoly to the
profuse growtn wnich covered the young and tender spruut.
This condition is paralgel to that found in the field condi-
tions where the turgus attacks tne nlant wnen the young and
tender shoots are lirst proauced, causing the early deatn o1
the vlant, or to an attack of the root haire at:a iater period
probably nephing in tne first wilting of the tops, by means
of a gen ral weakening of the vitaiity ot .he plant caused by

tne invasion of che root epestem,

INFECTION EXPERIMENTS WITH GROWING PLANTS.

Artificial infection experiments we.e be gun
in January under greenhouse cunaitiuns,

Paratftined vaskets were used nolding avduut
one cuvic foot of soil. Tnese baskets were all wasued in

mercuric chloride after paraf1rining and were then filled
93-

with s0il that had been sterilized at 22 lba. nressure for
2 nours.

lwo sets of enecks wee used and these were
vlaced in various parts of the greem.iouse with the infected
plante.

In baeketea 1-50 inclusive tne tubers used
were procured from Frank Lowell, Gardner, Maine and are
known as the Lowell Green Mountain variety, they were obtained
turough the kindness of Dr. W.J. Morse of the Maine Experiment
Station. All these tubers were exam ned for Fusarium and
found to be free. They were then treated in various ways
witn formaitdehyde and mercuric chioride. Thia was done for
use in another exveriment on the effect of disirfection on
tne esvrouting of the tube:s, and then were tne: used for this
infection experiment, if anything they aid in the work as
Only tnose tuberswhich produced the mort nealtny and vi gorous
shoots were ueed for this experiment. |

All tuvere were planted Jamary 25 th. trey
were inoculated harch 1 st, and dug May 10th.

Tne formaldenyde treatment was as follows;
the sound tubers were was:ed in water tnorougnhly and then
soaked ina solutiun of formal dehy de, lpint to 30 gaitons of
water, using tne 40% foruaidens@e, for 14 - 2 nours, tnese
were tnen allowed to dry before planting.

Mercuric chioride treat:ent was for the same

length of time in a 1©1000 sclution ot mercuric chioride.
94.

INOCULATIONS.

dne plants at the time of inoculation were all
aout le2 ft. in height, growing vigorously.

Tne spore suspension was made by grinding up
a atock cul ure of F. oxysporum in aterile water, this suspen-
sion wae then nut on the @eoil. ‘ithe cut roots were injured
by inserting a trowel in the soil at different points thus
injuring and breaking the roots, bout not serverly enough to
materially injure the vigor of the Plante.

The Fnizoctonia suspension was made up in he
same way. |

Where direeased pieces of infected potatoes
were used, tne stem end whicn was deeply irnfectec was cut oif
and placed in the vasket from wnich the soil had been removed
around the roote and che diseased pieces were then placed in
ec1ose proximity to tre main roots and ihe ecil put back so
as not to injure the roots.

Where mycelium wae introdueed into the stem
Below the murtace, the soit was geniuiy removed so as not to
injure che roots, the stem was then washed in mercuric chioride
and the myceliuiw introduced cy means of a aterile platimm
inoculation evade.

It was tound impossigaie to make a diagnosis
of the Icliage 10r wilt symptoms as owing to the crowded
condition in the greenouse the plants were set too ciose

togetner and resulted in a spindling pxrowth, which soon wilted
95-6

down owing to the excessive ne t in the greenhouse in the
epring and tne changes in moisture conditions, wnich in some
casee even caused a rotting of the seed viece and stem. Tne
tubers produced were very emall and scarce and it was impossible
in many cases to diagnose the disease in this way. The :
following data were obtained by observing the condition of
the atem and following it down to the roots and tuber if
possible,

Any cases which were slight enough to make
@ diagnosis very dvuubtful were taken into the laboratory
and tiseue cultures were made trou. tnece and the re«uits

snown 1n the tables,
METHOD OF INOCULATION

55.
6.
7°
8,

10.
11.
}2.
13.
14,
15.
16.
17.

1S
20.

21

22.
23.
24,

INFECTED PLANTS.

 

spore suspension

sound roots

snore suspension

imured roots

mycelium in contact

with inured ro

F. & Rniz. "

* sound roots

ote.
"

SEED TREATYVENT

 

t ormaldehyde

t
6
a
"
mercuric cnloride
«
«

Iormaideny ue

0
*
mercuric chioride
0
#
«
*
TO: aldehyde
|

96

SIZE OF SEED.

 

single eye

quartered

single eye
quartered
"
nalved
"
n

Single eye

quartered.

naivea,
KETHOD OF INOCULATIO?

25,
26.
27.
28.
29 6
30.
31.
32
33.
34.
35.
36.

 

Check

SEED TrEATVENT

 

formal denyde

mercuric chioride

37-placed diseased cieced of--formaldenyde

38, int, plants in pot,

39 «

40.
41

42,
43.
44,
45.
46.
47.
48,
49.
50.

SOund roots.

same s@ above with

injured rcots
°

ineert mycelium in =tem

beiow ground
e

necuric chi oride

97-6

SINGLE EYE

 

nalved

Single eye

nalved
Singie eye
fe
quertened
®
«
”
Single eye
”

quartered,

nalved
98.

RESUT.TS.
DIAGNOSIS TIS:UE CUT.TUR:S.

No browning Uf either stem, roots or cubver.-=- no growtn

Stem showed wet rot aue to moisture=conditions- no growth

Noinfectiun of stem, roots or tuver, .

oO cs OO ww PP WW N -~
@

2
oO
®

Slignt imrection of stem «nd tuvder--= good growth.
11. Stem a:d roots wet roiced.

12. "

13. No antection

14. Sitight infection of tne stem.

15. .

16, Deep infection of stem, roots ana wuper.

17. .
18. Slight infection of stem---- ------------- goud growth,
19. Deep infec.ion of stem, no Rnizoctoria, "

20. No infection, Rnhizocionia on svem and routs-clagnt,
2l. * . no Ruizoc,. lesions.

22. Wet rot ot stem and roots.

23. | .

24, No imection, few slight Rnizoc. 1tesions on steus and roots,
DIAGNOSIS

25. Wet rot

26. Xo infection.
27. °

28 Wet rot.

29. No infection.
30. .

31. .

RESULTS

32. Slight infection------

33. No anfecticn,.

34. "
a
36.027"
cy

38. Wet rot.

39. Very slight browning of s

40. No infection.

41. "

42. Deep infection,

43 "

44, Wet Trot —-

45. Very slignt intection.

46. °

47. Stight infection.

48. Deep infection

49. "
50. "

99

CULTURE.

eeaeau ove gv0d growth.

tem------ suspected.

ereen-- no growtu

=ocee suspected

eeaeccea good growth,
 

100.
SUMMARY OF RESULTS OF IsFECTION EXDER ILEsTS.

In considering tne resulta of tnese inocula-
tion experiments, tne difirerent metnods of cuiting tue seed
pieces and sterilization nave pneen disregarded, only the
various metnods of inocuiations nave been considered,

une plants practicaily all died down beiore
digging, but it was a premature deain caused vy the poor
cultural conditiunsa in the greennouse and the tubers were by
no means mature wnen the examination was made. Tnus if the
plants had been erown under petter conditiona and the growing
ceriod maintained 1or a longer time, infection might have
taken nlace tater in cases wnere the inoculations did not
succeed, or 1t may nave been present very slignily in tne roots
at the time the ex ail nation was made but owing to the poor
condition of ihe plants for diagnosis it wa: impossible to
oveerve them.

In all cases where the inoculation was carried
On by means of using a vater suspension of tne svorer on tne
sound roots, no irfection occured and no mlturer made in
the laboratory snowed the presence of the fungus. This shows
the inavility of the fungus to,penetrate the sound roote of
the plant quickly after a vigorous growt: nad beer obtained,
It ie very poreibie that if'aick soil * had been used or even
pure culture inocu.iations made in the soil vetore the plants
nad made a good growth, that the Ilurgus would be avle to
penetrate the smaller roote and bring about the slight infection

whicen Manne reports l.c.
101.

In the case of the apore suspension used with
injured roots, infection takes rlace rapiuly and 5 out of &
of ine plante enow the cnaracteristic browning of tne sten,
from which qmliwres were ovtained in the laboratory. Two died
tnrough other causes making 1t impossibie to determine the
presemce ot the fungus, and only one sriowed no infection.
This is provably the cause of the rapid spreading of the
disease in the field either through infected tubers or by
meane of badly infected soil. Tne cultivation of the crop
undoubtedly injures the roots to some extent and the entrance
of tne fungus ie mace mech easier.

The object of the exreriment wiere inoculations
were made f:ireave with Rhizoctonia and later wich Fusariu:. .
was to determine the eifect the Rnizoctonia tesions on tne
roots have to che entra:ce of Fusarium. However curly two out
of six plants showed tne rreeence of Rnizuctonia lesions on
tke roote and these but slightly, thus practicaily the same
conditions were found as in the inoculation experiments on the
sound roote and no irfection was found in a:y ‘age,

Where disezsed pieces of imecte:. potatoes
were used witn soaind reota, only one showed a very alight
browning, suspected to ve an irfection wiile 4 showed no
no,intection, these reeuitsa are -ravcticaily tne same as in

the other expe imente on sound roots.
102

Vhere the same metiiod as avove was used with
injured roote there were 1our infec.ions out of tive, one
aying of the wet rot, two of tnese four cases snowed a very
deep infection, Tnis experimert sanows the degree of infection
to be about the same ase in the case wnere the srore suspension
was used on injured roote.

All of the plants inoculated by introducing the
mycelium into the stem below the surface of the ground snowed
infection, ail but one being a wery deep infection from which

the organism was isolated in the :avoratory.

SUMMARY.

1. The parasitism of the fungus on the seedlings.

2. The inabili.y of the rungus to penetrate the sound roots
oftthe plant quickly under the conditicns of tne experiment.
3. The rapidity with whicn the funzus gains entrance tn: ougn
root imnuries.

4, Inocuration witn svore suepension caused tne disesse as
quickly as the diseased pieces of infected tucersa,.

5. Patnogericity of the orgaris:., snown vy the infection

produced by the inoculation of the myceliu: into tne stem.
103.
CONTROL.

Taking uv the study of the remedial measures
necessary in the contro: of tnia disease the cnief Iactor to
be observed is the metnod of infection. From the preceeding
experiments it can be seen that the fungus enters the plant...
through the underground system at any time during the season,
and it ie shown 1n the following experiments that itis
capable of Living over in tne vascuiar system of the host and
intecting the young sproutsa in the avring. Trese two methodar
ot infection make the disease one of the nardest potuto
troubles to control.

It can be readily seen that a spray sucn as
Bordaesux wixture applied to the iopa of ihe plants will have
no alte:t on the progress of the fungus is the underground
system of tne plant. In the same way it is seen that the
ordinary to.maldenyde or mercuric chloide dips applied to the
outside of the potato tuber vel ore plan.iing wiil have absoiutely
no efirect on tne control of ine fungus. Thus we find that a
contro. of this disease mesa. be accomplished eitner by the
eradication, exclusion, or protection from the causal 1 actor.
‘tne following excerimenta vere conducted with tnis opject in

view.

CONTRO, EXP®RIPEeTS.
Work on the control of tnis divseace by means

of various metnod: ot tueatment with tne infected tubere

 
104,

w:s done by Manns * 1l.c. wno corducteu cis work under field
conditions. He reports that *" Tne increased yield brougnt
about by cutting away the infection and treating tne seed
varied just about in proportion to the amount and serveiity of
the Fusarium infec tion.-c-e------ - Treatment alone without
cutting away tne intection as a rule gave no ve.ter results
than ine untrested, snowing that tne chiet facvor in reducing
the yield was tne Fusarium infection, wnicn was internal in to e
seed and the treatment did not reacn it."

In tne fo:towing experiments conducted in the
greenhouse the condition the condition of injured roots
caused vy cuitivation and the possibi ity of spreaaing from
hill to niil is done away witn as eacn vlant was kept in
seperate baskets prepareu in the same way as in tne inte:tion
experiments, uslng sterile soil in all cases , tuus making
a vetter controled experliuent tnan could be conductedcin tne
field.

Tne deptn of the infection in che tive.s used
in this experiment varied very little, usually avout ¢-l inch
in depth. In all cases where the infection waa cut eway the
cut was made ea far as the prown disco: oration appeared, Tune
Lreatment with tormaidenyde and mercuric ciuroride was the

same ag in the infection exre_imente. When che stem ends were

re:oved tne treatm .ents:with the disirfe tants wes made afier
105.

cutting. If the tube: was cut in nalf for butt and etem end
experiments the treatment was made be.:ore cutting and in all
cases the tubers were allowed to dry before planting.

When the tubers were cui the knife was sterilized
before eacn cut, preventing the pocsibility of carrying the
infection 1 rom some of the tubere to the others,

The tubers used were of the Sir Walter Raleigh
variety grown on a badly anfecrted field tnat suowed practically
a@ total irfection with a premature death of the plant several
weeks early.

All tubers were planted in tne baskets Feourary
Qtu and examined May Stn. In most cases tne foliage was still

green and the tubers had not matured.

 

TREATNWENT OF TUL ERS

L. Infection not cut away, tubers not treated.

2, . oe

3. « #

4, " "

De " "

6. " "  eeee- etem end
7 . n eece-= butt end
S, Infected atem end removed, treated HgCl5

9, " "

10. " .

li. . .

l2. " ”
106.

TREATMENT OF TUBERS.

13. Infected stem end removed, treated tormaldehyde.

14. " "

15. . "

16. ° .

17. Infection not cut away------ treated HgCl,

18. a" «

19. ._ reece treated forma] denyde.

20. 7 "

21. " "

22. " . Were ceee- stem end
23. . " butt *
24. 7  eeeeee HgClo treatment stem *
25. " ne butt "
26. . ee ewee not treated. stem "
27. " " butt *
28, " " stem "
29. " " butt "
30. * " stem *
31. . " butt "
32. " ° etem *
33. . " butt *
34. . * “ sten ”*

35. . . butt *
 

107.

CONDITION OF PLATS MAY 8.

 

Lab. culture,

1. Stignt infection, f:-w roots, no tubers,

2.

3. No infection.

4. Deep infection, no tucers, screener en eee ene good growth.

5.Sprout only 1 1mch in neignt, stunted.

6. Deep imection, no tubers.

7- No imection, growtn of plant very slow.

8, Top wilted, suspected infection, no tubers.-- ro growtn.

9. Top dead, very slignt infection. c-sceree-e- euspected.
10. . deep infection. °

ll. 0 " °

12. No infection.

13. Suspected infection, no tuiersm -reen--eeeeee no growtn.
14. No intection.

15. Stunted eprout, oniy 2 inenes nign.

16. No intection.

17. 0 " no tubere,.

15. Deep infection of etem and roots, no tuvera.

19. Slight infection in tne tubers.

20. So infection in stem or tubere, etunted frowtn.

21. .

22. Deep infection in stem, siight in iube:.,--- slight growth.
23. Very siight browning in stem, suspected.--- no growin.
24,
25.
26.
27.
28.
29.

30.

31.
32.
33.
34.

336

108,
CONDITIC?E OF PLATS.
Lad. culture,
Top dead, no tubers, deen infection in stem.
Stunted, svrout only 2 inches, no roots.
Entire plant dead and rotted, no diagnosia.

No infection.

Deep intection.

NO "
Deep .
NO "
Deep "
Wey rot.

 

DISCUSSION OF RESu:..TS,

Tubers not treated or cut snow infection in

all cases,one of these being so badly infected that tne

esprouting was retarded so mucn tnat only a growth a few inches

long wae made,(Plate 8) the seed piece remaining sound but

no

roota being 10Yrmed. Tne sare tube 8 snow tnat tne stem

end of such intected tubers produces a deep infeotion wnile

the plant from the boutt end ia healtny.

Wnen the stem end was removed and the tuvders

treated witn sgClo we find that tne infection was slight in

3 out of 5 cases, and wnen treated in the sume way with

f.omaldenyde oniy one infection w-s found, sowing tne better
 

109.

fungicidal effect of tormaldenyde, while the cutting of tne
stem ends controls the disexase greatly.

inese experiments while not conducted on a
large enough scale to give conclusive data on control under.
tieid conditions, are indicative of certain results, and
parellel exyreriments will be run in the field this summer.

Where HgCl5 and formaldehyde were used without
cutting off tne stem end we find that practically all the
plants, 7out of 9 show irfection, which clearly snows as may
be expected thatfungicicea applied to the outside of ihe tuber

cannot materially injure the fungus growtn on tne inside.

To recapitulate:-
It is seen that tie cutting of1 ot tne irfected ends of the
tubers is the greatest weans of «ontroling the dise: se,
erepeciaily if a to:maidenyde din is used.

The stem erd of tne infected tuber is the
cnief factor in producing the discase unleas the infeciion
is very deep.

inatew cases spi outing was restarded to saucn
and extent that no tope resulted. This condition ir tne field
would greatly injure the crop causing an uneve:: atand and a
poor yield, a condition which has cften beer noted by tne

writer in icnigan,
 

 
110.

TESTS WITH C:tEMICALS.

It was thougnt tnat by adding cnemicals to the
soil as fertilizers the disease might be controlled in tne
ecil, so attempts were made to test this out in the laboratory.

snis was done by growing the fungua on potato
stems, sterilized, to wnich the cnemicals to ve teeted were
added.

rotato stema weighing 2.5 gr.were put in teat
tubes with 3.5 cc. of distilled water, to two tubes each were
added .1 gr. of the chemical to be tesied tnus making tne

chemical added 1.6 % of the total suvstance in each case.

 

3 daye 1 week.
1. Potassium cnloride,-- abundant abundant
2. " suifate -- vary slight "
3. Flowers of sulfur -- abundant "
4. Cneck -- " "

 

“0 appreciable differences in the different
growtns were Observea, showing tnat the fungus is capavoie of
growing abundanily in the presence of these chemicals in much
larger amounts than would ordinariiy be found under field
conditions, and therefore it may be concludea that the use
of tnerse chemicals are useless in contro:ling thia dis.ase

in the soil.
lll.
EFFECT OF FUNGICIDES.

The experiments conducted in the greenhouse
inaicated that the disinfe::tantes used in treating the seed
are capable of controlling the disease to a alight extent if
brought in direct contact with the Organism,i.e. by treating
the cut endea of infected tubers. inis work was carried on
in the laboratory to deter:.ine just wnat effect the disinfec-
tante used nave on tne organism.

An aburdant cuivture of poth mycelium anu spores
was obtained by -rowing in a flask of Kmadson's Fuli nutrient
media #27. Several of the large colonies tormed were then
transfered to tuber of HgClo 1-1000 sol. and to tpoes of
formaldenyde, lpt. to 40 gal. water. They were allowed to
reuain in these tuvee for 14 hourr and tnen the culvunies

were transfered to tubes of nutrient agar and plates rnoured.

RESUT.TS.

Ll. HeClo-- 2 tuves -------- no ;rowtn at end of w. ek.
2; Formualdenyde--- 2 tubec-- "

3. Cueck, no cLreatmente----- good growth.

White it is impossibie for the disinfectants to
be of ery use in controlling the disease vher a simple dip is
used, Owing to the fact tnat tne fungus is in tne vascular
system of the tuber, there is no douvt tnat a dip used after

the infected ends of the tuber nave veen cut away, will
112

necessarily penetrate a small distance into the vascular
system and kill tne fungue presert, which may nave been
overlooked by wine grower who ie not familiar with the disease
and might rosgsibly fail to cut deep enough.

unere is aiso the vossibility tnat if the
disirfectant penetrated the vascular system enougu to kill
tne fungus it would also penetrate deep enougn to prevent
germination, but the usual time aliowed for dipping has been
used in mary localities after cutting the seed etock without
great danger, altnougn it is rather a riaky practice witnout

further experi:entai data.

 

 

 

 

 
113.

SUMMARY OF CONTROL MEASURES.

After s study ot the disease in the field
and tne preceeding experiments conducted during tne winter,
tne foilowing recomendations are made for tne control of tne
disease.in tnis state.

fae tirst most tundanental and important control
method to be recomended is tne exciusion of the causal factor.
TO accomoliisn this the grower must vecome finliLiar with the
symptoms ot the disease in tne field. Tne plants snowing
wilt in toe field snould ve staked out and harvested seperate
from the rest of the crop. Again at digging time mmerous
tubers snould oe examined to determine the rogsaibliity of
the organism being present in tne tubers that nad not srowed
any Signs of the wiit on the tops in the field. in this way
tne percentage of anf::ction in the cror can be opvatained
and the course to be followed in the next years planting
can be Laid out.

If possible enougn nexsltny plants enould be
selected .rom tne inrerted tield to atart a eamall seed plot
the next year on land that is free from infection, preterably
lard tnat nas never been plantexu to potatoee. Tne antected
seed snouid not be sola or used for seeu purpuyses, out the
infection unless very serious does not materiaitly injur: tne
tubers for market purvoses and they can be uisvosed or in

this way. From the seed plot the next year there should be

 
114.

a large enougn yield of healthy tubers to plant the next
years crop. In tnis way votatoes not only free from tne
Fu:arium wilt but also from the other notato diseases may
be obtained as well as a metrod of hill selection which
enould be used to keep un the standaru of cuality and to
ineressc the yield. By using this metnod tne grower is enabled
to vroduce nis own seed and raise the stanaard of his quality.
this is greatly to be recommermded over the practive of
sciling tne ertire iniected crop and buying new seed from
some unknown source. The amount of Fusarium wilt found in
thie state, and in tne entire countru in tact is so great that
in most casea it 18 men sater to select your own seed tnan
to risk bywying it Irom otners.

Tne organism nas been ynroved to live over
in tne soil tor a number of years and thereitore a longer
rotation tnan tnree years snould be used. badly infected
tietas =nould not ve vianted again to notatoes for 6 years
and a longer period ie better. Cu! tivated crops will naturally
help in enreaaing the fungus tnrough the soli and should not
be used on infected fields.
. From the few small expeciments conducted witn
chemicaslfertilizerea in tne laboratory and from the large
amount of work done along this tine by Smitn anda Swingle i.c.
it appears that the use of adding cnemical fertilizers to

the s0il to help control tne syread of tne funguais useless
115.

and no evidence as yet has been presented to show that it

controls the discase in any degree,

TREATLE!?T OF INFEC ED SHED.

If it is necessary to plant seed that snows
a slight infection tne following metnods are to be recommered.
All tubers srnould be examined by cCulting across tne stem end
and acertainng tne depth of tne infection. This intected
piece snoid be cut awagp ae tar as tne brown disev.oration
appears and the tuber then treated with a formaidemyde din,
1 pint of 40% tormaidehyde to 30 galtons of water, for 13

huurs alioved to dry and tnen planted.

Tnere 18 2 slignt danger of injuring the seed
germination poy treating witn disinfectants after cutting,
and although it is used in many Localities witnout any visable
injury to the stard it is a met::od that is not safe to advise
witrout turtner experimental data.

If the infection is siight and tne cut made
deep enough to remove all tne prown discoloration, it is
better to use tne dip vefore cutting, then tne seed may be
dried out and tne deptn of irf ection eagliy ovserved at tne
time of cutting the seed. Tne cnief objection to tnis metiod
is the great loss ot treating a large m ve: of pOtoé@s and
tnen naving them tnrown out.

The safest plan in tne contro. ot tnisa disease

is the use of sound seed On elean soil.
 
 

 

116.
L.EDIA FCEMULAE

 

#1. Nutrient agar.

 

Diesolve 3 gm. extract of beef in 500 cc. water, add 10 gm.
peptone, add to 500 cc. water in wnich has been dissolved
15 gm. agar. Steam 30 min. cool to 60°, add egg albumen,
boil 10 min. over free flame, filter, tube, autoclave,

#2. Steemed potato stens.

 

Potato stemea wasned trorougnly and
placed in test tuves with email amount cf distilled water,
heated 3 succes<ive dys for 10 min. at 100° «,
#3. Steamed potato plugs.

Large smooth tubere wun: roug:ly wasned
and pared tnick, cut into plugs 2 incnes 1Ong witn knife,
trim to Long B' ant, wach over night in running water,waasu in
Qistiiled water, and place in tuoes witn a mall amount of
distilled water. Heated 3 successive d-ysa at 100°C, tor 10 min,

#4. Boiled corn meal

 

4 incn corn west in tube, add 10 cc.
water, sO&sK Over rignt, autoclave 15 win. at 15 lb.
# 5. Steamed bean ctems.
Same as #2.
#6. Boiled wuite beans,
Fill tuve } inch, coarsely cracked wnite
navy beans, add 10 cc. water, soak weil, autociave 15# for 15 mi
#7. Steamed tupine sprouts.
Lupi:e sprouts wasned tnorvougnily, placed

in tube with distilled water, steam 3 days at 100° 4,
-— _ - aoe 7 apes e——— FT
. —_-

 

 

117.

#8.

Boiled lupines

Same aa # 6,

 

#9. Boiled prunes.

Cut vcrunes in nalf, add water, autoclave

for 15 min. at 15 1b.

 

#10. Pear agar.

500 cc. vear twig decoction, 500 cc. water
in wiien was disolved 10 gm. a-ar end 10 gi. nentone, steam

for 1 nour, filter, tube, sutociave, afver adding e; g abumen,

 

#11.Prune azar.

120 gem. prune juice, 1000 ce. distiiled
water. 12 gm. agur flour, 10 gm. egg albumen, Steam, fi: ter,

tube and eutoclave,

 

#12. Oat agar.

50 gm. ground oats, 350 cc. dietililed water.
eteam in cooker, strin tnurough cne es clotn, 1U gm. agar
heated witn 150 cc. water. i.ix tnoroug: ly and voit in ateamer,

tilter, tube and autoclsve, 15 iin.

 

# 13. Carrot plugs.

Same as # 3.

 

#14, Lettuce agar.
15 em. avar f our, 1000 er. water, 10 gm

pentone, = lb. cneonned letiuce, lU gn. e: g albumen,

 
118,

# 15. Stesmed p-renipe.
: Same as # 3.

 

os gm clean rice, aad 10 ce. water,

autoclave, 15 min. at 15 lb.

 

#17. Sweet potsto plugr.
Same as # 3.

 

# 20. Fotato agar.
Potatoes wasied, pared tniick, cut in than

slices, 300 gm. potato, 500 cc. water. Cook in -tesmer 1or 1% hr.
Stratp, dissove 15 g@ ag.rin 500 ce. water, mix witn infusion

aad 20 gm giucose, autociave 45 min. filter, tune, autoclave,

 

# 26. Soii extract. agar.
Soli exirsct 1000 cv. 15 gm. agar, KoHPO4

tube, autoclave,

 

#26 Sy rtnetiec medium.
1u00 ce. w.ter, NgSOqg .4932 gm.-- KHoPO4 1.362 gm.

Na,C0, 1.061-- Maltase .7204-- Aeparagin .2644,

 

# 27 Kmdeson's Full Nutrient.
1000 cr. waver , 1 gr. HNO3--.5 gr. KHoPO4

-25 gr. MgSO,-- .002 gr.FeoCl3--5 gr. cane sugar.

 

# 34. Cucumber agar.
Grind cucumbers in cnopper, ressout juice,

tilter througn cnessecloth, to tnis add 10 er. afar disolvea
in 600 cc. water. Add egg atiumen, steam for hour, 111ter,

tube and autoclave,

 
119

LITERATURE.

1895---Clinton, G.P. Dry End Rot. I11l. Agr. Exp.
Bull. # 40, 0 139-140
1896---Stewart, F.C. Another Stem Biignt of ine Potato.
“SY. Gen. Exp. Sta. Bul. 101, p 83 and 84,
lS97er- * " The G@omuiricibility of Botato Stem Blignt
N.y. Gen. Exp. Sta, Bul. 138, p 632 and 624.
1904--- Clinton, G.P. Dry rot of the Fusariuy oxycnvorum.
Rpt. from the Conn. Exp. Sta. 1903; tig b om 1. 22
1904--- Smitn, E.F. and Swingie D.B. The Bry Rot of Potatoes
due to Fusarium oxys»orum. Bur. Pi. Ind. U.S.
Dept. Agr. Bul. 55, pp i-62. 8 1. 2 text tig.

1906 -- Norton, J.B.S.
ITrisn Potato Diseases, karyland Agr,

Exp. Sta. Bul. 108. p. 67.

1909*-+- Tidsawell,z
Dry Rot. Rnt. Gov. New Soutn Wales,

Bur, Microviology, 60-61. Ilius.

1909--- Morse, W.J..
Potato diseases in 19U8,

Maine Avr. «xn. Sya. Bul. 1604-p.2.

1909e-- T:oundsnoury, C.P.
Dry Rot of tne Potato,

Agr. Jour, Cave of Good Hope 35: 42-46. 3 tig.

1909 ---Dugwar, Boi.
Fungus Diseases of Plants.p.31/7 & 31%
120

1909--- Orton, W.A.
Potato Diseases in San Jouquin County,

Cal. U.S.Dept. Agr. Bur. Pi.nt Ind. Cir. 23
p 4-8.

1910--- Anpel,O and Wollenweber, H.W. :
Grungiagen einer .oO:rO0gapnie aer Gattung

susarium. Aro.k. L101. Ansar. Land -ue "oratew.
Band 1b- 8 tnat is not rignt 1-207.
Pls. l-3. fig.-l-2.

1910--- Orton, W.A.
Seclence Vol. 31. pe. 751.

19ll--- Manns, T.F.
The Fusarium Blignt and Dry rot of tie Potato

Onio, A r,Exp. Sta. 224, p.v.299-336. Pil. l-l.

19l2--- Jones, 7..R.
Potato diseases in Wiescorsin ind . eir

Control. Wis. Agr. xp. Sta. “ir. 36.9, 4.

Wle\--- Ctakeman, #.C.
Potato viseases,

tinn, Agr. Bap. Sta. Bul. 35
1912--- Wilcox, E.N.- Tank,G.K.K. ana “oil V.¥.
Dry Rot of wie lrian Potato Tuner.
Neb. Agr. Exp. Sta. Kesesren 1ul,1,np 1-88
1913--- Wollerwever H.",
Piizrarasitvare Welke:.rar;keiten
der Kuiturntlanzen, Ber. d. Deut. Bot. Gea.

Hett i. vo 17-33.
121

1913--- Woilermweber H.W.

Studies on tne Fusarlu. rroviem

Pnytonata, vol3.no1, p 24-51, pl and ltext 11g.

1914---

Potato Leaf Boil und Related M1 seases,
U.S.Dent. Agr. Hur. “L. Ind.Bul. 64 vrofersionalr
pl. Isyure Lard 2,
WotLenwecer, °:..W.
fdentitication of Upeciea ofr
Fusarius occuring on tne Sweet Potato, lL -omea satat

Jour. Agri. Kescearen, vol 2. No, 4 , 251-286,

1914--- Coons, G.H.

Potato Disagses of »ieni gan.

Mien. Agr. Exp, Sta. Bot. Dept. Sv, bul # 66,

 * NO attemnt nie veen mude to give a counite

bibtiograpny. Tnis works inciudes all oftne revert works

On tie sunject and revorts of tne disease trom tne difier nt

localities,
EXPT.ANATIONS OF PLATES.

PLATE 1, Fig. 1. Showing the difterent methnoda ot sentation
in macroe~ores from 1 to 5 septa:e, and the cn:racteristic
tormea tourd in 2 weers old culture on potato sten.

Fig. 2. Average tor.s tourd of microconidia,

PLATE 2. Showing different metnods ot germination of tiie
macroconidia from tne game culvure.

Fig. 1 and 5 , 8 nour old showing metnod of atarting
germ tubes,

Fig, 2,3 and 4, s11 24 houre old.

PLATE 3. Fig. 1. setnod of microcomdia gernination.
Fig. 2. Abnor:za: forme of macrocomdia o:tained trom

an old culture.

PLATE 4, Showa the growtn Oot tne same conidia tnurougn the
various stagea ot growtn to tne cpore tormatiun, snown on
PLATE 5.
PLATE 6. Fig. 1 Terminal chianydospore.
Fig. 2 terminal and intercalated in same nyp:ae.
Fig. 3. Intercalated in conidia,

Fig. 4. Cnlanydosnorcs gerilrati «+.
Plate 2.

Fig. 1 Fig. 5.

Kua

Fig. 4.

 
Fig. 2.

Plate 3.

Fig. l.
Plate 4,

10 are.

16 nrs.

 
Plate 6,

 

Fig. 3.

 

 

 
 

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EXPLANATION OF ‘T.ATES 7-10

PLATE 7. Fig. 1. Culture 1 week old, snowing pionnot«sa
form on nutrient agar.
Fig. 2. Plate poured in mtiient agar at 56 °C

wnen testing for tnermal deathn point.

PLATE 8, Fig. 1. Badly inferted tubers, 3 montha after
planting, in the greennou-e,
Fig. 2. Tuvers snowing tne vorown discoloration

of the vaacular system in tne atem end.

PLATE 9. Showing cultures in test tunes,
Fig.l. On mtrient agar.
Fig2. “ boited rice.

Fig. 3. " potato ctem.

PLATE. 9. Tissue culture mace from tuvers of pia ta
inoculated in tne freennouse witn mycelium introduced in the

etem ,
 
 

 
 

PLATE 9
PLATE 10.

 

 

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