DISEASES OF GINSENG.
The following is from an article on "The Alternaria Blight of
Ginseng" by H. H. Whetzel, of Cornell University, showing that the
author is familiar with the subject:
Susceptibility of Ginseng to Disease.
The pioneer growers of Ginseng thought they had struck a "bonanza."
Here was a plant that seemed easily grown, required little attention
after it was once planted, was apparently free from all diseases to
which cultivated plants are heir and was, besides, extremely
valuable. Their first few crops bore out this supposition. No wonder
that a "Ginseng craze" broke out and that men sat up nights to figure
out on paper the vast fortunes that were bound to accrue to those who
planted a few hundred seeds at three cents each and sold the roots in
five years at $12.00 a pound.
Like many other grow-wealthy-while-you-wait schemes, nature herself
imposed a veto. Diseases began to appear. The prospective fortune
shrunk, frequently dried up and blew away or rotted and disappeared
in the earth. Several factors contributed to this result:
1. The removal of a wild plant from its natural habitat to an
entirely artificial one.
2. The encouragement by the application of manures and cultivation of
a rapidity of growth to which the plant was by inheritance an entire
stranger, thus weakening its constitution and depriving it of its
natural ability to withstand disease. Cultivated roots in three years
from the seed attain greater size than they often would in twenty
years in the woods.
3. The failure in many cases to provide conditions in any degree
approximating the natural habitat, as, for example, the failure to
supply proper drainage that is in nature provided by the forest trees
whose roots constantly remove the excess of rainfall.
[Illustration: Diseased Ginseng Plants.]
4. The crowding of a large number of plants into a small area. This,
in itself, is more responsible for disease epidemics than perhaps any
other factor.
Of all the twelve or fifteen, now more or less known, diseases of
this plant one in particular stands out as _the disease_ of Ginseng.
Altho one of the latest to make its appearance, it has in three or
four years spread to nearly every garden in this state and its
ravages have been most severe. This disease is the well known
Alternaria Blight.
The Most Common and Destructive Disease of Ginseng.
The disease manifests itself in such a variety of ways, depending
upon the parts of the plant attacked, that it is difficult to give a
description by which it may always be identified. It is usually the
spotting of the foliage that first attracts the grower's attention.
If examined early in the morning the diseased spots are of a darker
green color and watery as if scalded. They dry rapidly, becoming
papery and of a light brown color, definite in outline and very
brittle. With the return of moist conditions at night the disease
spreads from the margin of the spot into the healthy tissue. The
disease progresses rapidly so that in a very few days the entire leaf
succumbs, wilts and hangs limp from the stalk. If the weather is wet,
the progress of the disease is often astonishing, an entire garden
going down in a day or two. Under such conditions the leaves may show
few or no spots becoming thruout of a dark watery green and drooping
as if dashed with scalding water. All parts of the top may be
affected. The disease never reaches the roots, affecting them only
indirectly.
Cause of the Disease.
The disease is the result of the growth of a parasitic fungus in the
tissues of the Ginseng. This fungus is an Alternaria (species not yet
determined) as is at once evident from an examination of its spores.
These are in size and form much like those of the early Blight
Alternaria of Potato. These spores falling upon any part of the plant
above the ground will, if moisture be present, germinate very
quickly, sending out germ tubes which pierce the epidermis of the
host. These mycelium threads ramify thru the tissues of the leaf or
stem as the case may be, causing death of the cells. From the
mycelium that lies near or on the surface arise clusters or short
brown stalks or conidiophores on the apex of which the spores are
borne in short chains. The spores mature quickly and are scattered to
healthy plants, resulting in new infections. Only one form of spores,
the conidial, is at present known.
That the Alternaria is a true parasite and the cause of the disease
there can be no doubt. The fungus is constantly associated with the
disease. Inoculation experiments carried on in the botanical
laboratory this summer show conclusively that the germ tube of the
spore can penetrate the epidermis of healthy Ginseng leaves and stems
and by its growth in such healthy tissue cause the characteristic
spots of the disease. This is of special interest as it adds another
to the list of parasitic species of genus long supposed to contain
only saprophytes.
Upon the general appearance of so destructive a disease, one of the
first questions of the growers was "where did it come from?"
Believing that it was a natural enemy of the wild plant, now grown
over powerful under conditions highly unnatural to Ginseng, I
undertook to find proof of my theory. I visited a wooded hillside
where wild Ginseng was still known to exist. After half a day's
diligent search I obtained seventeen plants of different ages, one of
which showed spots of the Blight. Examination with the microscope
showed mycelium and spores of the Alternaria. Unfortunately I did not
get pure cultures of the fungus from this plant and so could not by
cross inoculations demonstrate absolutely the identity of the
Alternaria on the wild plant with that of the cultivated. So far,
however, as character of the spots on the leaves, size and form of
the spores are concerned, they are the same. This, I believe, answers
the question of the source of the disease. Introduced into gardens on
wild plants brought from the woods, it has spread rapidly under
conditions most favorable to its development; namely, those pointed
out in the earlier part of this paper.
The wind, I believe, is chiefly responsible for the dissemination of
the spores which are very small and light. Not only does the wind
carry the spores from plant to plant thruout the garden, but no doubt
frequently carries them for longer distances to gardens near by. The
spores are produced most abundantly under conditions favorable to
such dissemination. During moist, cloudy weather the energies of the
fungus are devoted to vegetative growth, the spreading of the
mycelium in the host tissues. With the advent of bright sunny days
and dry weather mycelium growth is checked and spore formation goes
on rapidly. These spores are distributed when dry and retain their
vitality for a long period. Spores from dried specimens in the
laboratory have been found to germinate after several months when
placed in water. The disease might also be very readily carried by
spores clinging to the roots or seeds, or possibly even by the
mycelium in the seeds themselves. The fungus very probably winters in
the old leaves and stems or in the mulch, living as a saprophyte and
producing early in the spring a crop of spores from which the first
infections occur.
Summer History of the Disease.
Altho it is on the foliage that the disease first attracts the
attention of the grower, it is not here that it really makes its
first appearance in the spring. The stem is the first part of the
plant to come thru the soil and it is the stem that is first
affected. The disease begins to show on the stems very shortly after
they are thru the soil, evident first as a rusty, yellow spot usually
a short distance above the surface of the soil or mulch. The spot
rapidly increases in size, becomes brown and finally nearly black
from the multitude of spores produced on its surface. The tissue of
the stem at the point of attack is killed and shrinks, making a
canker or rotten strip up the side of the stem. Such stems show well
developed leaves and blossom heads giving no evidence of the disease
beneath. Occasionally, however, the fungus weakens the stem so that
it breaks over. Growers have occasionally observed this "stem rot"
but have never connected it with the disease on the leaves later in
the season.
[Illustration: Broken--"Stem Rot."]
It is from the spores produced on these cankers on the stem that the
leaves become infected. The disease begins to appear on the leaves
some time in July and by the middle of August there is usually little
foliage alive. Infection frequently occurs at the point where the
five leaflets are attached to the common petiole. The short leaf
stems are killed causing the otherwise healthy leaflets to droop and
wilt. This manifestation of the disease has not generally been
attributed to the Alternaria. The seedlings are frequently affected
in the same way causing what is sometimes known as the "top blight of
seedlings."
From the diseased leaves and stems the spores of the fungus find
their way to the seed heads which at this time are rapidly filling
out by the growth of the berries. The compact seed heads readily
retain moisture, furnishing most favorable conditions for the
germination of any spores that find their way into the center of the
head. That this is the usual course of seed head infection is shown
by the fact that it is the base of the berry on which the spots
start. These spots, of a rusty yellow color, gradually spread all
over the seed which finally becomes shriveled and of a dark brown or
black color. Spores in abundance are formed on the diseased berries.
Affected berries "shell" from the head at the slightest touch. This
manifestation of the disease has long been known as "seed blast." If
the berries have begun to color the injury from the disease will
probably be very slight. The "blasting" of the green berries,
however, will undoubtedly reduce or destroy the vitality of the seed.
There is a strong probability that the fungus may be carried over in
or on the seed.
[Illustration: End Root Rot of Seedlings.]
The roots are only indirectly affected by this disease. The fungus
never penetrates to them. Roots from diseased tops will grow
perfectly normal and healthy plants the following season. It is in
the leaves of the plant that practically all of the substance of the
root is made. The bulk of this substance is starch. The destruction
of the foliage, the manufacturing part of the plant, long before it
would normally die means of course some reduction in the growth and
starch content of the root. However, it seems probable that the
greater portion of root growth is made before the blight attacks the
foliage. This seems borne out by the fact that even blighted
seedlings usually show nearly as good growth and bud development as
those not blighted. In the case of older plants this is probably much
more true as the latter part of the season is devoted largely to
growing and maturing the berries. The Alternaria blight is dreaded
chiefly because of its destructive effects on the seed crop.
Preventive.
The first experimental work on the control of this disease so far as
I know, was carried out by Dr. I. C. Curtis of Fulton, N. Y. Having
suffered the total loss of foliage and seed crop during the season of
1904, Dr. Curtis determined to test the efficacy of the Bordeaux
mixture the following season as a preventive of the blight. The
success of his work, together with this method of making and applying
the mixture is given by him in Special Crops for January, 1906.
Extensive experiments in spraying were carried out during the past
season by the Ginseng Company at Rose Hill, N. Y., under the
direction of the writer. During 1905 their entire seed crop was
completely destroyed by the blight. Losses from the same disease the
previous season had been very heavy. During 1905 they had succeeded
in saving a very large proportion of their seedlings by spraying them
with the Bordeaux mixture. Encouraged by this they began spraying
early in the spring of 1906, just when the plant began to come thru
the ground. This was repeated nearly every week during the season,
the entire ten acres being sprayed each time. On account of poor
equipment the earlier sprayings were not as thoroughly done as they
should have been, and some disease appeared on the stalks here and
there thruout the gardens. A new pump and nozzles were soon installed
and all parts of the plant completely covered. Practically no blight
ever appeared on the foliage. There was some loss from "blast of seed
heads" due to a failure to spray the seed heads thoroughly while they
were filling out. The seed heads Were doubtless infected from the
diseased stalks that had not been removed from the garden. A very
large seed crop was harvested. The formula of the Bordeaux used at
Rose Hill was about 4-6-40, to each one hundred gallons of which was
added a "sticker" made as follows:
Two pounds resin.
One pound sal soda (Crystals).
One gallon water.
Boiled together in an iron kettle until of a clear brown color. It is
probable that more applications of Bordeaux were given than was
necessary, especially during the middle part of the season when
little new growth was being made.
From these experiments it is evident that the problem of the control
of the Alternaria Blight of Ginseng has been solved. Thorough
spraying with Bordeaux mixture begun when the plants first come thru
the ground and repeated often enough to keep all new growths covered,
will insure immunity from the blight. Thoroughness is the chief
factor in the success of this treatment. It is, however, useless to
begin spraying after the disease has begun to appear on the foliage.
* * *
_To the President and Members of the Missouri State Ginseng Growers'
Association._
Gentlemen--In response to a request from your secretary, I was sent
early in August to investigate your Ginseng gardens, and, if
possible, to give some help in checking a destructive disease which
had recently appeared and had in a short time ruined much of the
crop. Thru the aid of some of your association, at the time of my
visit to Houston, and since that time, I have been furnished with
valuable data and specimens of diseased plants.
The summer of 1904 was marked by a very abundant rainfall. The shade
of the arbors kept the soil beneath them moist, if not wet, for
several weeks at a time. This moist soil, rich in humus and other
organic substances, formed an exceedingly favorable place for the
growth of fungi. Gardens under dense shade with poor drainage,
suffered the greatest loss. All ages of plants were attacked and
seemed to suffer alike, if the conditions were favorable for the
growth of fungi.
Symptoms of Disease and Nature of the Injury.
Between the first and the fifteenth of May black spots having the
appearance of scars appeared on the stems of the Ginseng plants. All
ages of plants were attacked. The scars increased in number and grew
in size, sometimes encircling the stem.
The first indication of injury was seen when one leaflet after
another turned brown; from them the disease spread down the petiole
to the main stalk. Other stalks were attacked so badly that they
broke off and fell over before the upper portions had even become
withered. After the loss of the top from this disease the crown of
the root was liable to be attacked by fungi or bacteria, causing
decay. I found little of this in the gardens at Houston. The greatest
loss caused by this disease lies in the destruction of the seed crop.
I have succeeded in isolating and studying the fungus which causes
this disease. The fungus belongs to the genus Vermicularia and occurs
on a number of our common herbaceous plants. I found it near Columbia
this autumn on the Indian turnip. The fungus lives beneath the
epidermis of the Ginseng plant; breaking the epidermis to form the
black scars in which the spores, or reproductive bodies, are
produced. The spores when ripe are capable of germinating and
infecting other plants.
Treatment.
Fortunately this disease can be effectually checked by the use of
Bordeaux spraying mixture.
Damping-off Disease.
Another source of loss was in the damping-off of young plants. The
fungus which causes this disease lives in the surface layer of the
soil and girdles the plants at the surface layer of the ground,
causing them to wilt and fall over. The trouble can be largely
avoided by proper drainage and stirring the surface layer, thus
aerating and drying the soil.
The Wilt Disease.
By far the most destructive and dangerous disease remains to be
described. It made its appearance about the first week in July,
causing the leaves to turn yellow and dry up; the seed stem and
berries also dried up and died before reaching maturity. This was the
disease which caused the greatest loss; whole plantations often being
destroyed in a week. Neither the Bordeaux spraying mixture nor lime
dust seemed to check its ravages.
I have succeeded in isolating the fungus which is the cause of this
destructive disease and have grown it in the laboratory in pure
cultures for nearly five months. Cultures were made by scraping the
dark spots on diseased stems with a sterile needle and inoculating
sterilized bean pods or plugs of potato with the spores scraped from
the stem. In two or three days a white, fluffy growth appears on the
bean pod which rapidly spreads until it is covered with a growth
which resembles a luxuriant mould. I have also isolated this fungus
and made cultures from the soil taken from diseased beds.
The fungus belongs to the genus Fusarium and is probably identical
with the fungus which is so destructive in causing the wilt of
cotton, watermelon and cowpeas, and which has been carefully studied
by Smith and Orton of the United States Department of Agriculture.
Treatment.
It will be seen from this brief description of the fungus that it is
an exceedingly difficult disease to combat. Living from year to year
in the soil it enters the plants thru the roots and spreads upward
thru the water-conducting channels. It does not once appear on the
surface until the plant is beyond recovery. Obviously we cannot apply
any substance to kill the fungus without first killing the plant it
infests.
There is but one conclusion to be drawn, viz.: That application of
fungicides will not prevent the wilt disease.
There are, however, two methods of procedure in combating the
disease: First, the use of precautions against allowing the fungus to
get started; second, the selection and breeding of varieties which
will withstand the disease.
From the very first the arbor should be kept free from all possible
infection by the wilt fungus.
Gardens should be small and located some little distance apart, then
if one becomes infected with the disease it can be taken up before
the disease infests a larger territory. If the roots have reached
merchantable size they had best be dried and sold, since they are
likely to carry the disease when transplanted. If they are
transplanted they should be carefully cleaned and reset without
bruising.
Proper drainage is very necessary for a successful Ginseng garden. It
is advisable to locate the garden on a gentle slope if possible. In
all cases the ground should be well drained.
The belief of many that the death of the Ginseng was due to the wet
season was without foundation, because the fungus develops best in
soil which is continually moist and shady. This also accounts for the
well-known fact that all rots, mildews and rusts are worse in a rainy
season than in a dry one.
[Illustration: The Beginning of Soft Rot.]
Ample ventilation must also be provided in building the arbor. Many
arbors are enclosed at the sides too tightly.
The material used for mulching should be of a sort which will not
contaminate the garden with disease. Some fungi will be killed if the
ground is allowed to freeze before putting on the mulch.
The second and, to my mind, most promising mode of procedure lies in
propagating a variety of Ginseng which will be resistant to the wilt
disease. In every garden, no matter how badly diseased, there are
certain plants which live thru the attacks of the disease and ripen
seeds. These seeds should be saved and planted separately, the
hardiest of their offspring should be used to propagate seeds for
future planting. By thus selecting the hardiest individuals year
after year it will be possible in time to originate a variety of
parasitic fungi. There seems to me to be more hope in developing such
a resistant variety of Ginseng than in discovering some fungicide to
keep the disease in check.
Bordeaux Mixture.
It is surprising that any considerable number of farmers,
horticulturists, Ginseng growers, etc., are ignorant of a preparation
so necessary as Bordeaux for profitable cultivation of many crops.
The following is taken from Bulletin 194 of the New Jersey
Agricultural Experiment Station. The advice given in this paper
recently by Professor Craig is repeated and emphasized. Every farmer
should have the bulletins issued by the experiment station of his own
state and have them within easy reach at all times.
Bordeaux mixture derives its name from the place of its discovery,
Bordeaux, France. It consists of copper sulfate, which is commonly
called blue vitriol or bluestone, fresh lime and water.
Formulas used--Several strengths of the mixture are used under
different conditions:
1. (2:4:50) Copper Sulfate 2 lbs.
Quick Lime 4 "
Water 50 gals.
2. (3:6:50) Copper Sulfate 3 lbs.
Quick Lime 6 "
Water 50 gals.
3. (4:4:50) Copper Sulfate 4 lbs.
Quick Lime 4 "
Water 50 gals.
4. (6:6:50) Copper Sulfate 6 lbs.
Quick Lime 6 "
Water 50 gals.
Formula 1 is used for very tender foliage, as peach, plum, greenhouse
plants, tender seedlings, etc.
Formula 2 which is a half stronger than the preceding has about the
same use but for slightly less tender leaves.
Formula 3 is the formula for general use on apples, pears, asparagus,
grapes, tomatoes, melons, strawberries, etc.
Formula 4 is the strongest formula that is often used. It is
considered best for potatoes and cranberries. It may be used on
grapes, on apples and pears before blossoming and sometimes on other
crops. It was once more commonly used, but, except as here quoted, it
is generally being displaced by Formula 3.
* * *
Normal or 1.6 per cent. Bordeaux mixture:
Copper-sulfate (Blue Vitriol) 6 pounds
Quick-lime (Good stone lime) 4 "
Water 50 gallons
Six pounds of sulfate of copper dissolved in fifty gallons of water,
when applied at the proper time, will prevent the growth of fungi.
However, if applied in this form, the solution will burn the foliage.
Four pounds of quick-lime to six pounds of copper will neutralize the
caustic action. When sulfate of copper and lime are added in this
proportion, the compound is Bordeaux mixture.
Weighing of copper and lime at time of mixing is very inconvenient.
Bordeaux mixture is best when used within a few hours after being
mixed. Therefore a stock mixture of Bordeaux is impracticable. It is,
however, practicable to have stock preparation of sulfate of copper
and of lime ready for mixing when required.
The lime should be fresh quick-lime and when slaked must always be
covered with water to exclude the air. In this manner a "stock"
mixture of lime can be kept all summer unimpaired.
Sulfate of copper can be dissolved in water and held in solution
until needed. One gallon of water will hold in solution two pounds of
copper sulfate. To accomplish this the sulfate should be suspended at
the surface of the water in a bag. The water most loaded with copper
will sink to the bottom and the water least loaded will rise to the
surface. If fifty pounds of sulfate are suspended in twenty-five
gallons of water on an evening, each gallon of water will, when
stirred the next morning, hold two pounds of sulfate. This will form
the stock solution of copper sulfate.
If three gallons of this solution are put in the spray barrel, it is
equivalent to six pounds of copper. Now fill the spray barrel half
full of water before adding any lime. This is important for if the
lime is added to so strong a solution of sulfate of copper, a
curdling process will follow. Stir the water in the lime barrel so as
to make a dilute milk of lime, but never allow it to be dense enough
to be of a creamy thickness. If of the latter condition, lumps of
lime will clog the spray nozzle. Continue to add to the mixture this
milk of lime so long as drops of ferrocyanide of potassium (yellow
prussiate of potash) applied to the Bordeaux mixture continue to
change from yellow to brown color. When no change of color is shown,
add another pail of milk of lime to make the necessary amount of lime
a sure thing. A considerable excess of lime does no harm. The barrel
can now be filled with water and the Bordeaux mixture is ready for
use.
The preparation of ferrocyanide of potassium for this test may be
explained. As bought at the drug store, it is a yellow crystal and is
easily soluble in water. Ten cents worth will do for a season's
spraying of an average orchard. It should be a full saturation; that
is, use only enough water to dissolve all the crystals. The cork
should be notched or a quill inserted so that the contents will come
out in drops. A drop will give as reliable a test as a spoonful. The
bottle should be marked "Poison." Dip out a little of the Bordeaux
mixture in a cup or saucer and drop the ferrocyanide on it. So long
as the drops turn yellow or brown on striking the mixture, the
mixture has not received enough lime.
"Process" Lime for Bordeaux Mixture.
The so-called "new process," or prepared limes, now offered on the
market, are of two classes. One consists of the quick-lime that has
been ground to a powder. The other is the dry water-slaked lime made
by using only enough water to slake the quick-lime, but not enough to
leave it wet. Practically all of the process lime on the market is
the ground quick-lime.
When the hard "stone" lime becomes air-slaked it is evident to the
eye from the change to a loose powdery mass. Should one of these
prepared limes be to any considerable degree air-slaked, its
appearance would be no indication of its real condition.
A simple test for the presence of much carbonate of lime in these
prepared limes, can be easily performed, a small amount of lime--1/4
teaspoonful--dropped on a little hot vinegar, will effervesce or
"sizzle" if it contain the carbonate of lime, acting about the same
as soda.
A sample of a new process lime analyzed at this Station showed 30 per
cent, magnesia. This came from burning a dolomitic limestone, that
is, one containing carbonate of magnesia with the carbonate of lime.
The magnesia does not slake with water like the lime and hence is
useless in the Bordeaux mixture. There is no easy way outside a
chemical laboratory of telling the presence of magnesia.
As a general rule more "process" lime is required to neutralize the
copper sulfate than good stone lime. It is always well to make
Bordeaux mixture by using the ferrocyanide of potassium test--Cornell
University.