Tobacco diseases and tobacco breeding..

L TOBACCO DISEASES.
U. TOBACCO BREEDING.

WOOSTER, OHIO, U. S. A., NOVEMBER, 1904,

BULLETIN 156._

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CHARLES (Ei, MP HORNE, mle PAC acre yarcnsintreiie eee ener Ba RSE iS NO dias Bact Director
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BULLETIN _ :

OF THE

Ohio Agricultural Experiment Station

NuMBER 126. NovrEmMBeEr, 1904.

-TOBACCO DISEASES AND TOBACCO BREEDING.

BYE AS 2 SHE BY.

I—TOBACCO DISEASES.

PRELIMINARY AND EXPERIMENTAL STUDIES OF MOSAIC DISEASE, ROOT ROT,
BED ROT, BROOM RAPE AND CURING HOUSE TROUBLES IN OHIO.

INTRODUCTION.

The tobacco’ industry in Ohio, though apparently somewhat
localized, has vital interest for the areas devoted to tobacco growing.
The writer confesses a personal sympathy with tobacco growers
by reason of early experience in the tobacco field. The recent es-
tablishment at Germantown, Montgomery county, of a Station test
farm upon which tobacco probiems are given especial consideration,
brings Station officers into closer relations with the tobacco. in-
dustry. Aside from such matters as arose from desultory cor-
respondence, little attention has been given by the department in
the past to the study of tobacco diseases. The present publica-
tion is issued with the double purpose of presenting some matters
of present value and of securing a closer study of tobacco maladies
by the growers of this staple. We should be able, in time, to
increase our present limited and fragmentary knowledge of the
treubles of the tobacco plant bed, the tobacco field and of the curing

house.
87

88 OHIO EXPERIMENT STATION; BULLETIN 156. g
pee 68

TOBACCO DISEASES CLASSIFIED. “|
The tobacco plant, in common with many others, suffers from
any lack of proper nutrition, and the diseases from this cause may
Le varied. Wemay have unsatisfactory growth and maturity from
lack of the 1:ineral plant foods or from lack of adequate mcisture.
In the present discussion, however, we shall not attempt to cover
this line of trou..'es; we confine ourselves rather to specific maladies
which may affect particular plants without touching others living
under like external conditions. Here a plant may have abnormal
color variations in the leaves as by yellow though not dying areas in
them, at the same time that the adjoining plants of the same
variety and seed strain are normal in color and healthy in behavior.
Or a plant may suddenly wilt ~own and fail to attain full recovery
and yet another may suffer fron: dead spots in the leaves. All these
abnormal features which impair the vigor, productiveness or health-
fulness of such plants, we term diseases. We shall omit here the
discussion of insect injuries, though these in a sense come under
one of the divisions to be considered. The root rot and the wilt are
parasitic diseases as we shall see later; they are caused by specific
parasitic organisms. Non-parasitic diseases are such as have n0

specific parasitic organisms constantly associated with them.

I. NON-PARASITIC DISEASES OF TOBACCO.
1. THE MOSAIC DISEASE.

The mosaic disease, or ““Frenching’’, of tobacco, locally known
in Connecticut as “‘calico,’”’ is one of unusual interest. ‘The diseased
plants exhibit such a mottled appearance of the leaves, due to the
alternating areas of darker green and yellowish green in them, as
to make the appearance of the plants very striking. The leaves
are veritable mosaics; as such they catch and hold the interest of
the observer. Certain plants will exhibit these characteristics and
color markings while others near them have the normal, uniform
green color. Jn the tobacco field, as most will recall, plants with
abnormal color are quite frequent in unfayorable soil situations
and especially around wet areas. This class of situations is how-
ever by no means the only one; no particular specifications may be
made to apply generally in th’s respect. The mosaic disease oc-
curs in practically ail tobacco areus of this state and of the United
States and under favorable soil conditions; indeed the disease is
general throughout the tobacco growing districts of Europe and
Asia as well. Along with the mottled, or mosaic z_ pearance of the
leaves we may have distortions of the leaves ave to the unequal-
rate of expansion in the more healthy and in the siseased areas of
the leaves.

TOBACCO DISEASES.

Pate I—Tobacco leaf showing Mosaic Disease.

90 OHIO EXPERIMENT STATION: BULLETIN 156.

Possibly no other type of plant disease has so long resisted
the efforts of investigators to discover the cause producing it. It
seems now that we must class the mosaic disease of tobacco, the
yellows of the peach, peach rosette, the mosaic disease of tomatoes
and the mosaic disease of forcing house cucumbers, which the
writer has recently investigated at Ashtabula, Ohio, in one and the
same group of maladies. To discover the actual cause, or causes
of these diseases has long been the aim of students of plant pathol-
ogy. In recent years decided progress appears to have been
made; but as yet the final word is to be said on this matter of cause.
Mayer’ early made a careful study of the disease. He showed that
the disease is transmitted by inoculation and concluded that it must
be the work of bacteria. In 1898 Beijerinck” made a decided contri-
bution. He showed that the juice of diseased plants, filtered through
porcelain filters, yet retained the power of producing the disease
when a small drop of it was injected intoagrowing bud of a healthy
plant; he also found that diseased tissue kept these infectious
qualities even after drying and retained its injurious properties in
the soil during the winter; he further demonstrated that the so‘l
around the roots of diseased plants may affect the roots of healthy
plants. Studies of the disease have been made in our country by
Sturgis’ and by Woods”. The lest named publication will be of very
great value to any one who wishes to study the conditions surround-
ing the production of the mosaic disease in tobacco. Just as in a
sense Beijerinck was the discoverer of what he called “a living fluid
contagium”’ which he regarded as the cause of the .disease, Woods
was able to go further and ascertain the presence of certain enzyms
in the plants known as oxidizing ferments and named ovédase and
peroxigase. Both these investigators were able to transmit the dis-
ease by inoculation of fluid from diseased plants into the young por-
tions of healthy plants. The difference between the results of the
one and the other is in the specific designation by Woods of the oxi-
dizing enzym as the active agent in producing the disease.

'Mayer, Adolph, Ueber die Mosaikkrankheit des Tabaks. ieee Versuch
Station 32:451-467 pl. I (1886). Review in Jour. Mycol. 7:382-385.

*Beijerinck, M. W., Verhandelingen der Koninklijke. Akademie van Weten
schappen te Amsterdam, Deel © No. 5. See also Centb. f. Bakt. Par. &c.,
II, 5:27-33 (1899).

sSturgis, W. C., Conn. Exp. Station, Report (1898), 250-254.

*Woods, Albert F., The Destruction of Chlorophyll by Oxidizing Enzymes.
Centbl. f. Bakt. Par. &c. II, 5.745 (1899).

5Woods, A. F., Observations onthe Mosaic Disease of Tobacco. Bull. Bureau
of Plant Industry, U. S. D. A. 18:1-24, pl. I-VI.

TOBACCO DISEASES. 91

More recently still Hunger’ has investigated the mosaic disease
of Deli (Sumatra) tobacco. Hunger’s observations had led him to
believe that the disease may be communicated by touching first
diseased then healthy plants, as when the coolies seek for the
young worms, that is, the larve which eat the tobacco leaves. He
planned and carried forward an experiment, using a definite system
in the matter of touching, and found as a result that a very high
percentage of the healthy plants, touched directly after a diseased
plant had been touched in the same tour, became diseased.
Hunger has contended, as a result of his latest work, that
not only is the disease infectious by means of the fluid extracts
from diseased plants, but it is also infectious, we may almost say
contagious, by this method of touching.

It has been customary to speak of the mosaic disease as a phys-
iological one, because no parasites in the sense of living or parasitic
organisms are associated -withit. I have for the present contented
myself with calling it a non-parasitic disease.

EXPERIMENTS TO DETERMINE COMMUNICABILITY OF
MOSAIC DISEASE.

In 1904, under the direction of the writer, Mr. True Houser,
field assistant of the department, conducted experiments in the
plots of the test farm at Germantown along the line suggested by
Hunger’s work on Deli tobacco. A few inoculation tests were also
made, including in all 30 plants. The plants were inoculated in
different ways; some by insertion of a small fragment from a
diseased plant in an incision of a healthy plant; others by injection
of awatery extract of diseased plants into healthy plants. In every
case the inoculated plants contracted the mosaic disease, the length
of time a’ter inoculation befere appearance of evidence of the dis-
ease varying from one to two weeks, usually from 9 to 12 days.

There was no apparent difference between those inoculated
near the base and those inoculated in the tender portion, although,
asa rule, only the new growth showed the evidence of the disease.
In some instances, where rather young leaves were inoculated, the
disease afterward appeared. In this connection inoculations were
made of extracts from plants suffering with what is locally known
as yellow french, wherein the plant has a general yellow aspect.

Hunger, F. W. T., De mozaiek-ziekte bij deli-tabak. Deel I. Verslag
van de op Deli met betrekking tot de Mozaiek-ziekte genomen proeven in de
jaren 1901-1902. Med. s’ Lands Plantentuin 63, Batavia, 1903.

*Hunger F. W. T , Die Verbreitung der Mosaik krankheit infolge der Bc-
handlung des Tabaks. Centbl. f. bakt. Par & c IT, 11:405-408. (1904).

Drief resume of Par. 4, Med. s’ Lands Plantentuin, 63 (1903) contributed

y the author. .

92 OHIO EXPERIMENT STATION: BULLETIN 156.

No result was obtained and no communication of the yellow condition,
thus confirming an opinion previously held that this discoloration is
due to the influence of unfavorable soii conditions.

- Blossoms of various plants were inoculated through the nectar
by transmission of nectar from diseased plants, as by insect visit-
ation. A slender brush of horse hair was used for this purpose.
No evidences of disease were observed as a result of this method.

MOSAIC DISEASE COMMUNICATED BY TOUCHING.

The touching experiments were planned to test the danger of
communicating the disease through handling first diseased then
healthy plants, as in the operations of transplanting, worming,
etc. The touched plants were arranged in sets of eleven plants
each. In each set were three series of three plants each, marked
a, 6 and c, respectively. The plant @ of each series was touched
directly after touching a diseased plant then 4 and cin succession
without retouching a diseased plant. Series 1 was touched but
once; Series 2, twice on succeeding days; and Series 3, three times
on successive days. The same plant was used for c of both Series
1 and 2, or of Series 2 and 3, making a total of eight plants for the
three series. ‘The three remaining plants were treated as follows:
one marked P was touched with considerable pressure (in some
cases sufficient to break open the tissues of the leaf) after having
done likewise to a diseased plant; one marked .S was touched
upon the stalk; and the remaining one, marked Z, was touched
upon the lower leaves. The last three plants mentioned were
touched twice on succeeding days.

In all cases, where no’ otherwise stated, the touching was
done on the upper or middle leaves.

Over 400 plants were touched, but owing to circumstances
which prevented the collection of sufficient data from part of them,
those with insufficient data have been omitted in the table. After
the touching, the disease becomes visible, if communicated, only upon
the new growth and is to be studied as in the cases of inoculation.

To insure against unintentional touching, the healthy and dis-
eased plants were wormed and topped at separate times. The
following table shows in the first part the results obtained upon
touching the plants as determined upon the dates given, and also
the increase of disease in the surrounding portions of the field. It
will be observed from this table that the lowest percentage of
plants becoming diseased under the 1c heading was 35.7 per cent.,
while the highest was 90 per cent., and the average of all the tests,

TOBACCO DISEASES. 93

after the lapse of one month, gave an increase of disease due to this
cause amounting to 68.66 per cent. Against this increase in the ex-
periment was an increase of less than 3 per cent in the surrounding
plots described in Table I as “not touched.”” These experiments
confirm the results obtained by Hunger and show the necessity of
great care if the spread of this contagious disease is to be checked.
In the light of these experiments of 1904, it seems highly probable
that the inferences made in 1903, as to the spread of the disease ‘in
the handling of the seedling plants, or otherwise, during the field
practice of that year, are well founded.

TABLE I—Showing the results of observations and experiments as to the spread
of the mosaic disease in tobasco upon ordinary plants and upon those
touched with fingers after previous touching of diseased plants.

PLANTS TOUCHED

Manner} Total Plants diseased | Increase of disease) Total of disease
Date of of No. by Aug. 12. from Aug.12-Aug.31} up to Aug. 31.
touchiny. of
eoebing |) plants: No. Per cent.| No. jPer cent.|| No. |Per cent.
July 26-20 .-...... scheme 3a 20 16 80 2 | 10 18 90

ro. ole 3b 20 lL 55 7 35 18 90
ee ae ge reer oe 3c 6 2 33.3 3 50 5 83.3
bee Ga Sek oT 2a 20 8 40 5 | 2% Bo 65
ReMi Maire Gses frastivta. sins 2b 20 8 40 8 40 16 80
TBE ee ee SENS. la 20 7 35 2 10 9 45
‘Sirs aus" aoe Ib 20 6 30 3 15 Weed 45
AS Might bee agree cae Ic 14 4 28.6 1 (fell 5 30 7
Hommes lai ere tel ce. : 2-8¢ 14 4 28.6 6 42.8 10 71.4
: Been aeraeas seine. 12 20 12 GO 5 25 17 85
a ed ode Saha hiais Ss 20 10 Ha) 4 20 14 70

Soe Cae a Onee L 20 6 ra) 6 30 12 60
Ss a ait actos ooo Se 1-2c 6 2 33.3 3 50 5) 83.3

Gramd totat ow fb Pls. 220 96 45.66 | 55 | 25 151 | 68.6
PLANTS NOT TOUCHED .*
| | 6012 | 92 | 1.53 77 1.28 286 4.76

*At the beginning of the experiment, 119 plants of the total number, 6,012, or 1.98 per cent. were dis

eased in the areas herein studied,
PREVALENCE OF MOSAIC DISEASE IN SOUTHWESTERN OHIO.

The writer and Mr. True Houser have studied the disease in
the Germantown district during the seasons of 1903 and 1904.
Taking some 12 farms in the vicinity of Germantown, Montgomery
county, including the Station test farm, there was not a single farm
on which the mosaic disease did not occur in 1903. ‘The varieties
grown here are chiefly a cigar leaf filler. known as the ‘“‘Zimmer’”’

94 OHIO EXPERIMENT STATION: BULLETIN 156.

and the Connecticut seed leaf. The percentage of diseased plants
varied from less than 1 per cent. to 43.5 per cent. in these scattered
areas. Upon the Station t-s* farm, where 9'-1ting was deferred untu
somewhat late, owing to de.ays incideat*o ¢lotting and ditching the |
tobacco areas, a very curious but withal interesting state of facts
was found to hold true in 1903. As is common in tobacco fields, the
plots were of a definite number of rows and the results have been
calculated dealing with the row as a unit, with the plot as a unit,
with the fertilized plots and with the unfertilized plots of the area.
The variations range from 0 to 56 per cent. of diseased plants
in individual rows of the several plots and from 0 to 38 per
cent. in the plants of the whole plot. No differences were discov-
ered as between fertilized and unfertilized plots. To the writer it
appears that the most striking feature exists in the extremely wide
variation in the number of diseased plants in different rows of the
same plot. Statedin its briefest form, we may repeat that the per-
centage of diseased plants varies from nothing—that is no diseased
plants—to a little over half (56 per cent) inindividual rows, and oc-
casionally this range is found within the same plot. Possible
explanations of this variation in the amount of disease occur to one.
First, although the plants were set by machine, they were handled
in removal from the plant bed, and the tendency would probabiy
be to gather the plants from a limited area into a single bunch.
Such bunches might represent a large number of plants diseased
in the plant bed, despite the intention to reject diseased plants. Sec-
ond, the apparent contiguous, or more or less contiguous situation
of the diseased plants in the row may arise from the communica-
tion of the disease after the manner described by Hunger, as
above quoted. That there was in these plots late occurrence of
the disease is shown by the fact that one or more stalks in the
plot, which had been shorn of the later branches of the panicle
to preserve a few early blossoms for seed, became subsequently
diseased. The lateness of this discovery prevented carrying
out a series of carefully planned observations, as suggested by
the facts already given. In 1904 the seeds from a diseased plant
of 1903 were planted at Wooster but no disease occured in the
progeny.
PREVENTIVE SUGGESTIONS.

Our preventive suggestions must finally be based on fuller
knowledge than we now possess. ‘Two suggestions stand out
prominently in the light of the observations made during the past
two seasons at Germantown.

TOBACCO DISEASES. 95

First, all plants showing disease in the plant bed should be
removed. |

Second, it will be found advisable to destroy the diseased plants
in the field after removal.

The reason for the first suggestion will be evident and need not
be further discussed. The basis of the second suggestion is the
proved communication by touching, first, diseased then healthy
plants. This amounted to about 69 per cent. of infection in 1904.
(See Table I). It is recognized that we must know more of the
actual losses, both as to quantity and quality, resulting from the
mosaic disease before we can secure the largest interest on the part
of the practical tobacco grower.

Koning’ has already shown the need for care in topping. In
this, he reported the result of an experiment on a large scale, in
1897, in which diseased plants were first topped and directly a great
number of healthy plants had tops broken by means of the fingers
infected by the diseased plants; 88 per cent. of these healthy plants
afterwards became diseased. It is clear therefore that any hand-
ling of the plants must discriminate between healthy and diseased
ones. ‘To top, worm and sucker diseased and healthy plants
separately at different times, with disinfection of the hands before
passing from the diseased to the healthy, is essential if.we hope to
limit the spread of the mosaic disease in the field after it once
appears.

II. PARASITIC DISEASES OF TOBACCO.
a. DUE TO PARASITIC FUNGI AND BACTERIA.
1. ROOT ROT (BLACK ROOT).

In 1899 the writer received from Mr. B. W. White, of Neville,
Clermont county, Ohio, specimen plants of size for resetting, the
roots of which were attacked by a fungous disease which they had
designated “black root”. This trouble was described as being
very bad wherever beds were made the second or third year upon
ground that had been devcted previously to the seed bed.. The
roots of the plants were discolored externally, especially on the
shin or internode immediately above the earth’s surface, often
accompanied by cracking and deformation (Fig. 1.). A brief
examination with the microscope disclosed the constant presence
of the very characteristic parasitic fungus which we may call the
tobacco root rot fungus, 7/zelavia basicola Zopf’ (Fig. 2).

‘Koning, C. J., Die Flecken- oder Mosaikkrankheit des hollandischen
Tabaks. Zeitschr. fur Pflanzenkr. 9:55-80 (1899).

*Zopf, Die Pilze. 1890, page 97.

Yo OHIO EXPERIMENT STATION: BULLETIN 156.

From a drawing by F. M. Van Fook.

Fic. 1—Tobacco seedling affected with root rot.

So far as known to the writer, this is the earliest reported oc-
currence of this fungus upon the roots of tobacco in America, and of
this a note was presented before the Botanical Club of the American
Association for the Advancement of Science, at its Pittsburg meet-
ing. (See Science, new series, 1900.) Peglion' has earlier reported
upon the root rot of tobacco in Italy, attributed to the same fungus,
and in America Thaxter has reported its occurrence as a root rot
of the violet.” Some years ago the writer studied the fungus in
connection with nematode enlargements upon the roots of the cul-
tivated Begonia rubra.* Latterly, in 1903, similar specimens were
received from the plant beds of the Station test farm at German-
town. ‘The Assistant Pathologist, J. M. Van Hook, has recently
discovered 7%irelavia producing root-rot of ginseng. In the first
case mentioned, from Clermont county, the variety of tobacco was

1Attid. R. Aced. Lincei CCXCIX, V. I-II pp. 32-99.

*Report Conn. Agr. Exp. Station 13:166-167 (1891).
SBulletin Ohio Agricultural Experiment Station, 73:228. (1896)

TOBACCO DISEASES. | 97°

White Burley; the Germantown specimens were of a different vari-
ety. It is apparent that we have here a parasitic root rot disease
which, while manifesting itself more
conspicuously upon the young
plants in the plant bed, may be com-
municated to the larger plants of
the field should any diseased ones es-
cape rejection. Aside from the dark
color due to the reaction~:between the
parasitic fungus and the host on the dis-
eased areas, the symptoms of the dis-
ease are not different from other inju-
rious root diseases.

In the matter of preventive measures
it is clear, from the Clermont county ex-
perience that, plant beds should be made
upon new earth each year. Further-

more, all plants with black root should be
From a drawing by FM. Van Hook. | rejected in resetting. The field develop-
Fic. 2—The fungus of tobacco root rot : 5

Thielavia basicola Zopi. Camera lucida yspent of the trou ble remains open for
drawing of the fungus as it occurs Bpey ]

ginseng, tobacco and begonia. @ an r with us.

conidial forms; ¢ ascospores. All mag- study Wat

nified 665 diameters.

23 BED ROT:

On June 22d, of the present year, the writer observed areas,
in the plant beds of the Germantown test farm, in which the
plants had damped off, or rotted, asa result of the attacks of some
specific fungus. The destruction in these areas was strongly
marked and the diseased plants showed all gradations from fallen
to lesion-marked stages of the disease. (See Plate II). Specimens
were collected and photographed and microscopic examinations
were also made. ‘These show that we have here injury due to the
fungus /?hizoctonia. It is not possible at this time to state
any further specific characteristics of the fungus, which does not
appear to differ essentially from its forms upon other plants, in-
cluding the potato.

The source of the /?eAizo tonia appears to have been in the soil
employed or in the added manures. It is evident that we have
here to deal with a plant bed trouble (which we have named dcd
rot) of possible serious character, as well as with the root-rot pre-
viously described. The occurence of this bed rot warns against
-e-seeding in old plant beds. It is quite possible that soil treat-
-aent with formalin, of the strength employed for potato treatment

98 OHIO EXPERIMENT STATION: BULLETIN 156.

From a photograph by F M. Van Hook.

Priate I--Bed rot of tobacco seedlings. produced by the fungus
Rhizoctonia.

ae

TOBACCO DISEASES. 99

might improve conditions, but the chances are much against the
successful use of formalin in earth where tender seedlings, like
those of tobacco, are to be grown and transplanted. It is neces-
sary in all such cases to reject diseased plants. It does not appear
that this fungus has been previously investigated in its capacity to
injure tobacco. Subsequent to the bed studies, or during August,
plants in the field were observed showing peculiar injury ina rib-
bon like band extending frem root almost to the growing tip.
These plants tend to wilt down and especially to turn to the side
with this ribbon lesion. The injury, we have determined, is asso-
ciated with the bed rot trouble and doubtless results from the
transplanting of some seedlings marked by this fungus.

3. DECAY OF TOBACCO SEEDLINGS.

Behrens’ has described a wilting and decaying of tobacco seed-
lings, in which the symptoms consist of a wilting and a slime lixe
covering of the wilted parts. With this a dirty green color 1;
noticed, previous to becoming black. In the later stages a fungus
may be seen covering the parts, especially the young secd leaves.
This is identified by Behrens asa species of A/fernaria, possitly
identical with A. fenu/s. While it is possible that this disease may
have been met with in the young seedlings of the plant bed in our
tobacco districts, it has not been my privilege toexamine specimens’
as yet. Tobacco growers are solicited to send specimens of the
young seedlings which may be found drooping, or dying, in tie
plant bed.

4. THE GRANVILLE TOBACCO WILT.

Within the past three years a destructive wilt of tobacco has
been studied in Granville county, North Carolina. The symptoms’
are described as a drooping of the leaves, which soon become soft
and flabby, as if suffering from want of water. Asa rule, the lower
leaves droop first, the wilting gradually proceeding from the ground
upward. Frequently the leaves of one side of the plant succumb
earlier than those of the other. Often even a single leaf wil show
only one side infected. The wilted leaves soon die, dry ud, and
eventually the whole stalk dies, but remains standing with its dead
leaves still hanging, and isnot to be confounded with the temporary
wilt due to lack of moisture, excessive heat, etc. At the stage of ear-

1Behrens. J., Ueber den Schwamm der Tabaksetzlinge. Zeitschr. f.
Pflanzenlcr, 2:327-332;, (1892).

’See Bull. N. C. Agr. Exp. Station 188: (1903). ‘‘The Granville Tobacco
Nile: 2

100 OHIO EXPERIMENT STATION: BULLETIN 156.

liest wilting a section across the stem shows discoloration of the
woody portion; at more advanced stages the wood is found, either
‘in its internal or outer parts, to be punctured with longitudinal
black stripes. I have been informed that this disease was ob-
served in the vicinity of Germantown during 1903. The disease
differs from that known as “‘sore shin” in the south, in that the
stem of the wilt-affected plant never topples over from loss of
roots, as is true in sore shin.

Fic. 3—Tobacco plant attacked by the Granville, North Carolina, tobacco
wilt. (from Bulletin 188, North Carolina Experiment Station.)
CAUSES OF THE GRANVILLE TOBACCO WILT.

Two studies have been published up to this time with respect
to the cause of the Granville tobacco wilt. The one by Stevens
and Sackett (North Carolina Agricultural Experiment Station
Bulletin 188, September, 1903) the other by R. E. McKenney (Bu-
reau of Plant Industry, Bull. 51, 1903.) Stevens and Sackett have at-
tributed the disease toa species of bacterium and have produced the
disease from cultures of the germ obtained from affected plants.

TOBACCO DISEASES. 10]

McKenney, on the other hand, has found the conidia of a fusarium
in the vessels of diseased plants and attributes the causal relations
to the fusarium, which also causes wilting of cotton, cowpea and
other plants. Whether it may be found upon another investigation
that one or both of the organisms suggested are the cause of this
- wilt, we apparently have here a parasitic disease of which the cause
is propagated in the soil and is peculiarly adapted to be destructive
in case the same soil is planted successively in tobacco. With dis-
eases of this kind we are sure that crop rotation becomes a neces-
sity, and soil which produces the disease may be regarded as
“tobacco sick’. The writer would be very much pleased to re-
ceive information concerning the occurrence of this trouble, or
of similar troubles, in Ohio tobacco fields. I am indebted to Pro-
fessor Stevens for the illustration of this wilt (ig. 3).
5. LEAF BLIGHT (FROG EYE).

Tobacco, in common with most foliage plants, is attacked by
more than one species of parasitic fungus which produces abnor-
mal conditions in the leaves. Of this the leaf blight fungus, Cercos-
pora nicotianw, Eilis & Everhart, isone. This trouble has been de-
scribed by Sturgis’ as occurring in North Carolina. The writer has
met with various spotting conditions on tobacco in Ohio and inserts
this note respecting leaf blight to bring forward observations in
this line.

6. WHITE SPECK AND BROWN SPOT.

From North Carolina has come to us the description of another
disease of tobacco, under the name of white speck, attributed to the
fungus J/acrosporium tadscinum Ellis & Everhart’. . Another
species of the same genus Muacrosporium longipes K. & E.” is cred-
ited in the same state as the cause of brown spot.

7-8. DOWNY AND POWDERY MILDEW.

In Java, Van Breda de Haan has reported both a powdery and
downy mildew of tobacco and referred them respectively to Erysiphe
communis, (Wallr.) Ley. and Phytophora nicotiane n. sp. In Australia
these mildews are reported and referred tothe same fungi. The
downy mildew, should it occur with us, may be expected to prove
destructive. The destructive character of the downy mildew of
cucumbers as well as the downy mildew or rot fungus of the potato
may be recalled in this connection. The powdery mildew of the
pea and of many weeds and other plants, as well as this one of
tobacco, may be expected to disclose themselves by a whitish covering
of the growth of the fungus and is much less liable to prove destruc-
tive.

IReport Conn. Agr. Exp. Station, 20:273-277 1896.
2See Journa: of Mycology 7:134, 1892.

702 OHIO EXPERIMENT STATION: BULLETIN 156.

6. DUE TO PARASITIC FLOWERING PLANTS.
9, BROOM RAPE OF TOBACCO AND HEMP.

The most of our plant diseases, as we use the term, are pro-
duced by theattacks of parasitic fungi and bacteria. A few diseases,
however, are due to parasitic flowering plants, such as the dodders
which attack flax, alfalfa, cloverand certain wild plants. These dod-
ders are like other flowering plants, produced from seed -which has
matured in seed pods or capsules, but they are strongly marked by
the absence of green foliage; being parasites these have not the ne-
cessity for chlorophyll to be acted upon by sunlight in elaborating
food, so the plant does without the green leaves. Broom rapes, which
are likewise parasitic flowering plants, are analogous ina certain way
to the dodders but, different in that the broom rape is attached to un-
derground parts of the host plant—that is to the roots—while the
dodders become attachedto the parts above the earth.

The broom rape of tobacco, Orobanche ramosa L. was earlier
known in Kentucky upon hemp than upon tobacco; it attacks also
the tomato, rape, cabbage, parsnip, etc., and is known in Japan,
India, Europe and the United States. It has been described and
illustrated by Garman™*. It is from the last named bulletin by
Garman that we note the host plants of the different species of
broom rapes. In this (Bulletin 105) Garman reports the occurrence
of Orobanche luduvania on tobacco in Davis county, Kentucky. ‘The
nearest allies, among our common native plants, of this tobacco
broom rape are the beech drops and the squaw root; also the flowering
broom rape, which the writer has collected in the vicinity of
Columbus. Any one who is particularly interested in the broom
rapes of cultivated plants will do well to consult Professor Gar-
man’s Bulletin 105. The accompanying illustrations, Plates III,
IV and V will show the manner in which the broom rape occurs in
Ohio tobacco fields. It has been reported to the writer from a
small area near Neville, Clermont county, for several years past.
Specimens were sent tome by Mr. White, in 1901. The photo-
graphs from which the half tones were made were taken by
the writer in September of the present year. It will be noted
that the plants growing under the central tobacco plant of Plate III
are in bloom, and this broom rape produces seed freely, so that
it may be dispersed in the seed pod or through the seedsof plants
like hemp and tobacco. It would appear less likely to become ad-

“The Hemp Broom Rape of Tobacco. Bull. Ken. Agr. Exp. Sta., 24: 1890; &

Annnal Rpt. Ken. Agr. Exp. Sta., 1890, pp. 57-73, with 8 figures.. Also
Bull. Ken. Agr. Exp. Sta. 105, Mch. 1903.

TOBACCO DISEASES.

Photograph by A.

IlI— White Burley tobacco plant attacked by broom rape. Ovobanche +

¢

WLOSA

ee

104 UuiO EXPERIMENT STATION: BULLETIN 150.

/ vom a photograph by A, D. Selby.

PLare 1V—Showing tobacco broom rape, Orobanche ramosa, fully developed on
root of tobacco plant.

105

TOBACCO DISEASES.

‘*

From a photograph by A. D, Sclby.

PLATE V—Various stages in the development of the tobacco broom rape, Orobanche ramosa,
upon the roots of tobacco.

106 OHIO EXPERIMENT STATION: BULLETIN 156.

mixed with tobacco seed. owing to the manner in which the tobacco
seedis usually harvested. Theareaofinfectionin Ohio is smalland
confined to somewhat low bottoms skirting the river upon two
different farms in Washington township, Clermont county. Infec-
tion here may have come from the transporting of seed by the
water or it may have come from another source. The clus
ters of the broom rape often attain a very large size after the har-
vesting of the tobacco.. The amount of seed produced must be
considerable, so that it will be difficult to get these tracts of land
entirely free from the broom rape, so long as tobacco growing is
practiced at intervals. We have no evidence from the small area
in Ohio as to attack on other plants, but Garman states that in
Kentucky, infested land may be devoted to grains or grasses with
safety. Caution is advised with respect to the growing of tobacco
plants upon soil which is even suspicious. It will be a great draw-
back to tobacco culture to have other areas of the state so infested
with rape as are many of the hemp and tobacco lands in Kentucky.
The fact that it occurs in Ohio on tobacco would serve as a warning
against its further distribution within the state.

c. CURING HOUSE TROUBLES OF TOBACCO.

The tobacco diseases previously discussed relate to the growing
tobacco plant; other troubles of the curing house, that likewise
cause loss and impair the quality of tobacco, sometimes occur.
Those engaged in the curing and subsequent handling of tobacco
will recall many unfavorable conditions, which tend to affect the
quality of the crop, aside from its original quality when first cured.
The fermentations in the process of curing are regarded as essen-
tial to proper flavor, but unless properly controlled these fermenta-
tions may produce unfavorable results.

10. POLE BURN OR POLE ROT.

This is a disease of the curing house, referred by tobacco
growers to the effects of warm, damp, foggy weather upon the
newly hung tobacco. The first symptom is noticed in the neighbor-
hood of the veins and the midrib of the leaves where moisture is
abundant; later on the disease may extend. Sturgis has given usa
very full description in the Connecticut Station report for 1891,
pages 168-184. The entire contents of the curing barn may be leit
quite worthless as tobacco by the extension of the deadly burn fun-
gus. The disease may certainly be expected in every tobacco area in
our country, as it has been known to exist in the past in Connecti-
cut, Virginia, Kentucky, &c. The too close hanging of the tobacco,

TOBACCO DISEASES. 107

with the weather conditions already noted, will be likely to aggra-
vate the trouble very greatly; while more room and a limited
amount of artificial heat will be found to be favorable. Insufficient
ventilation willlead to bad curing. The actual organisms of the
decay have been studied by Sturgis, but it is doubtful whether

these are peculiar to this form of decay as against any other decays
of vegetable tissues.

11. STEM ROT.

When the tobacco stalks are hung up in the curing house the
leaves wilt and later dry up more or less, while the thick, succulent
stem dries out but slowly. Under conditions which may prove
unfavorable to the drying out, or even under average conditions, the
danger of rotting at the stem is considerable. The stem rotisa
disease of this character. It begins by white patches of a velvety
aspect upon the diseased parts, more especially the stem. ‘The
patches may spread to the veins of the leaf and induce unfavor-
able results. Sturgis’ has reported upon this disease and found it
to be due in Connecticut to a fungus known as JSotrytrs longibra-
chiata, and Behrens’ agrees with Sturgis except that he regards
this Botrytis longibrachiata as a form of PB. cinerea.

REMEDIES FOR STEM ROT.

In the curing house, this is usually remedied by gathering
the diseased stems and destroying them and by the use of germi-
cidal sprays in houses where the trouble has been serious. A spray
consisting of formalin of the strength employed for potato scab
should be very useful for this purpose and may be scattered
throughout the building by using an ordinary spray pump, suchas
is employed in orchards.

_ NOTES ON CURING HOUSE TROUBLE SOLICITED.

In order to present before tobacco growers some of the con-
ditions recognized elsewhere, these brief abstracts of curing house
troubles have been given in this bulletin. More complete notes and
advices as to the occurrence of curing house troubles will be thank-
fully received and will meet with response. It will be difficult to
state just what our peculiar conditions may bring forth in Ohio
until strict study has been made of these conditions in the curing
house.

1Rpt. Conn. Agr. Exp. Sta. 15:184-186 1891.

2Trockene und nasse Faule des Tabaks. ,,Der Dachbrand‘‘ (Zeitschr. f.
Pflanzenkr. 3:82. 1893.

108 OHIO EXPERIMENT STATION: BULLETIN 156.
II. TOBACCO BREEDING.

PRELIMINARY STATEMENT CONCERNING SELECTION AND CROSSING OF
TOBACCO IN RELATION TO NEW VARIETIES.

Since the establishment of the southwestern test farm of this
Station, through the efforts of the Germantown Tobacco Growers’
Association, the various phases of the local tobacco problems have
been under study. The Department of Plant Physiology and
Pathology has been requested to take up the question of producing,
or securing new varieties of tobacco for “cigar filler’? purposes.

In the various efforts made during the past two years, the
results of which are in part indicated on subsequent pages, the
botanist has been assisted by Mr. True Houser, field assistant of
the department. The crossing and selection work has béen done
by him under the direction of the writer, who wishes to express
his obligation to Mr. Houser for efficient assistance.

It has been stated by many prominent tobacco growers that
the Zimmer variety, so long grown for locally, cigar filer does
not meet all requirements, and that, therefore, new varieties should
be sought. In undertaking an investigation of this character the
general principles involved are not essentially different from those in
other jlines of plant breeding. "The methods may be stated in
brief to consist either (1) in selection or (2) in crossing followed

*

by selection.
_SELECTION- PROCESSES.

In the method of selection, new strains of established varieties
are obtained by the choice of individual growing plants of the de-
sired type, or types. These growing plants may be in special
gardens or simply in the tobacco field. When suitable types are
discovered the specimens are protected by bagging from undeter-
mined cross pollination, and the plant is permitted to ripen a few
of the earlier seed pods. At the time of bagging the other
branches of the cluster are clipped off; the bagging must, of course,
be done previous to the opening of the first blossom. ‘The pro-
geny from the selections thus made, must subsequently be grown,.
and the product after curing and fermentation, submitted to the
necessary tests to determine its quality and special adaptations.
It is apparent upon reflection, that this method has its limitations
in regard to the extent of difference between the variety grown
and the desired variety. If the variety already under culture
possesses most of the desired characteristics, then this method of
selection will prove well adapted; if, on the other hand, a wide

TOBACCO P@EEDING. 109

difference exists between the variety grown and the ideal new
variety, either the process by s*'~ction alone 1 1s" se laid aside, or
a longer time allowed for the breeding work in order to secure tne
finalend sought. The tendency of the variety under culture to
variation will naturally influence greatly the length of time nec-
essary to attain the ends in question. However, one serious
difficulty in tobacco breeding, and this applies at all stages to both
methods, is the relative immaturity of the tobacco plants at the
time the seed selection must. be made. It is but fair to state in
this connection that selection alone, if unsatisfactory, must give way
to other processes of breeding, and that whatever work is done
must be done under the limitations imposed by the course of
development run by the plants of the tobacco upon which we work.

METHOD OF CROSSING AND SELECTION,

In the second method, namely, that of crossing followed by
selection, we endeavor to secure the plants for subsequent selec-
tion by crossing two given varieties. The nature of the tobacco
flower and its adaptation to self-fertilization, as well as the labor
necessary toinsure cross pollination, must be duly considered.

While tobacco blossoms are freely visited by birds and insects
with long bills or probosces, such as the humming birds and the
hawk moths which lay the eggs of the tobacco worm, thus con-
tributing to cross pollination, the tobacco blossoms are seif. fertile
without insect or other visitation. Their adaptation to insect
visitation and attraction, through the nectariesof the blossom, are
but a possible co-operation in the widespread cross pollination se-
cured in the vegetable kingdom. If, therefore, we wish to cross-
pollinize, the blossoms must be emasculated by removal of the im-
mature anthers or pollen sacs, ata time just previous to the fall
opening of the tobacco piossom. ‘This period is indicated both by
the development of the corolia of the flower, including its chan-ze of
color, and by the slight yellowing of the anthers, or pollen sacs, at
the same time. The emasculated blossoms must then be protected
from insect visitation, by covering with suitable bags of a hardened
paper manufactured for this purpose. Since the anthers are re-
moved before maturity, at this time the pistil is not mature,
or receptive to pollen; tke receptivity continues for some days
usually, unless pollination occurs. Ripened and bright yellow s
from the sort it is desired to cross upon such an emasculated
pistil, are chosen the next day, or subsequently, and upon the

*The bags used in this work were manufactured by Schmidt, Dusseldorff,
Germauy, and may be obtained in various sizes.

110 OHIO EXPERIMENT STATION: BULLETIN 155.

cautious removal of the bag, applied to the stigmatic, or sticky
surface of the pistil of theemasculated blossom. Caution in this
manipulation is exercised so as toinsure only pollination by these
chosen pollen sacs. Such crossing does not change the plants upon
which it is performed, but the cross-fertilized seeds will be in-
fluenced and grow, when sown, into plants having certain charac-
teristics which resulted from the crossing. Usually these char-
acteristics have been found to be more or less intermediate, varying
from those plants showing very close resemblance to the one parent,
by almost imperceptible gradations into types approaching the other
parent. In our tobacco work, we have found thatin all, more strictly
intermediate types have prevailed in the progeny; these types par-
tale very decidedly of the characteristics of both parent varieties.
The crosses thus far made, have included, more particularly, crosses
between the large-leafed ‘Connecticut seed leaf” variety, and the
slender variety grown in the Miami valley underthe name of “Cuban.”
The illustrations will possibly show how the crosses exhibit the inter-
mediate characters. Most of the crosses show much larger leaves
than the Cuban, but with longer internodes than the Connecticut seed
leaf. The actual qualities of the cured tobacco remain to be
subsequently determined.
SELECTION OF CROSSES.

In the manner above indicated, about 30 crosses were produced
in 1903. The seed of some of these was lost, but 25 of them were
grown during the season of 1904. These are recorded by the
numbers under which the original cross-pollination was entered.
In this instance, they run from No. 51 to No. 75, inclusive. The~
illustrations will show the variation in part. Another factor will
be found in the yield of cured leaf, and still another in the quality
of this leaf. For final application of the results of crosses, the
favorable, or suitable sorts, must be determined by the processes
of selection which have been heretofore discussed. ‘Ten out of
the twenty-five varieties have been rejected, or at least set aside,
and only fifteen of these are to be planted in 1905. ;

While, during 1904, only a single row of each number was grown
in a plot, in 1905 duplicate 20th acre plots will be grown Of vediGn
selected number, checked by standard plots of the Zimmer and
grown along with plots of the ‘‘selection”’ strains of Zimmer and
with plots of the Cuban and Connecticut'seed leaf. In this manner
the habits of growth, productiveness and quality of the various
crosses will be determined in the course of two to five years, ac-
cording to the amount of retesting necessary.

TOBACCO BREEDING. 111

Numbers 53, 54, 55, 58, 59, 61, 63, 64, 68, 69, 70, 71, 72,74 and 75
have been selected for plot tests in 1905, while numbers 51, 52, 56,
57, 60, 62, 65, 66,67 and 73 have been set aside as of less apparent
merit. It willthus be seen that the procedures in plant breeding
require rather long periods of time; several years are ordinarily
required in the selection of a suitable type, or variety, from
crosses or from more or less fixed varieties already grown. It
always remains to be determined, when across is grown, whether
the plants are uniformly of one type, and if they are not, the sort
must be grown repeatedly until the type is ‘“‘fixed.””. We made
notes in’the field in 1904 which show that, with the crosses thus far
studied, the variation among the plants of the rows of the same
number in 1904, was much less than anticipated. It is expected
therefore that the fixing of type with the tobacco crosses will be
less prolonged than in the case of wheat and some other plants.

This statement of the processes employed and the progress
made in breeding varieties of tobacco is published at this time, in
order not only that the members of the legislature who, aided
in the establishment of this tobacco test farm, and the members
of the Tobacco Growers’ Association, may discover the manner
in which the Station is carrying out its obligations, but also that
the general tobacco growing public may know something of the
operations in this line. Two or more years must yet elapse
before the results of this tobacco breeding will merit further
publication.

BULLETIN 150.

OHIO EXPERIMENT STATION

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TOBACCO BREEDING.

From a photograph by A. D. Selby.
Priate VII—Tobacco crosses of Connecticut Seed Leaf and Cuban varieties as grown in 1904. Nos. 71, 72, 74 and 75 have
been selected for plot tests in 1905. No. 13 has been set aside as of less apparent merit.

BULLETIN 156.

XPERIMENT STATION

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