profitable industry. In the United States chestnuts have been considered
a marketable commodity ever since the Indians carried them to the
settlements and traded them for knives and trinkets. The demand has
always exceeded the supply and at the present time about $2,000,000
worth of nuts are imported from Europe annually. With the development of
the better varieties of the American nut has come an increased activity
in the United States and the chestnut orchard industry promises to
become one of very large importance. It has an added advantage that the
trees can be grown upon the poorer types of soil which are not adaptable
for farming or the raising of other fruit.
At the present time there are in what is known as the blight area of
Pennsylvania, or eastern half of the State, about 100 orchards ranging
from 12 trees up to 400 acres in extent. These orchards are in varying
stages of blight infection, some of them being almost entirely free, due
to the attention which has been given them. In order to protect such
orchards the Commission is compelling the removal of infected trees
within a certain radius of them.
As you know the blight has been a very serious factor in this industry.
Some of the orchards have been completely annihilated and the income
reduced from several thousand or more dollars per year to nothing.
Whether or not the blight will completely wipe out the orcharding
industry is a subject of large importance. Personally I believe that
chestnuts will be raised commercially in Pennsylvania in increased
abundance, and as the various phases of the blight subject are brought
to light, keeping the disease under control can be more easily
accomplished. At the present time this is being done in certain orchards
by the present methods of examining the trees often, treating each
infection, or removing the tree. If this policy is successfully pursued
for several more years it will demonstrate conclusively that chestnuts
can be grown in spite of the blight and this will mean an opportunity to
use vast areas of waste land in Pennsylvania and in the other states, in
a highly profitable manner.
* * * * *
The Chairman: The subject of the next paper is Some Problems in the
Treatment of the Chestnut. It will be presented by Mr. Pierce, after
which we will have a general discussion of the entire subject.
Mr. Pierce: Mr. President, ladies and gentlemen: I see that, as we wrote
our papers separately, some of the things I had in mind will be similar
to those Mr. Rockey had.
SOME PROBLEMS IN THE TREATMENT OF DISEASED CHESTNUT TREES
BY ROY G. PIERCE
Tree Surgeon, Pennsylvania Chestnut Tree Blight Commission
The problems that present themselves to the growers of chestnut trees
concerning the present disease may be summed up under three heads:
first, what the disease is, how it is caused, and how it may be
recognized; second, what is to be done with diseased trees to bring them
to health or to prevent them from infecting other healthy trees nearby;
third, what means in the future can be undertaken to keep a tree
healthy, that is, to prevent reinfection.
First, what the disease is, how it is caused, and how it may be
recognized. The disease known as the chestnut tree blight is caused by
the fungus, _Diaporthe parasitica_, which usually finds entrance to the
tree through wounds in the bark. The mycelium or mass of fungous
filaments gradually spreads through the bark in much the same manner as
mold spreads over and through a piece of bread, even penetrating the
wood to a depth of sometimes five annual rings. The spread of the
fungus, resulting in the cutting off of the sap flow, is the immediate
cause of the wilting and dying of the leaves and branch above the point
of girdling. This wilting of the leaves, followed later by the death of
one branch after another as the fungus spreads, has given rise to the
term "blight" of the chestnut trees.
The danger signals which the chestnut tree displays when diseased are
not a few. In summer, when the tree is first affected, the leaves turn
yellow-green and wilt, later turning brown. Small burs and withered
leaves retained in winter are some signs of the diseased condition of
the tree. At the base of the blighted part a lesion, or reddish brown
canker, is usually found. This lesion may be a sunken area or, as is
frequently the case, a greatly enlarged swelling, known as a
hypertrophy. After a branch has become completely girdled sprouts or
suckers are very apt to be found below the point of girdling. In old
furrowed bark on the main trunk of the tree the presence of the disease
is seen in the reddish brown spore-bearing pustules in the fissures. In
determining the presence of the fungus in the furrowed bark of old
trees, one must learn to recognize the difference between the light
brown color characteristic of fissures in healthy growing bark, and the
reddish brown color of the fungus. When the disease has been present
several years the bark completely rots and shrinks away from the wood,
and when the bark is struck with an axe a hollow sound is produced.
Many of the owners of chestnut trees throughout Pennsylvania do not
acknowledge that a fungus is causing the death of the trees. They state
that since they have found white grubs or the larvae of beetles in
nearly every tree that dies, that it has been the larvae that killed the
tree. It is acknowledged that generally white grubs are found in dying
chestnut trees, and that in nearly all of the large cankers or lesions
these grubs are present. However, if one will take the pains to examine
the small twigs and branches or the new shoots rising from the stumps,
that are diseased, he will not find the grubs present.
Second, what is to be done with diseased trees to bring them back to
health or to prevent them from infecting other healthy trees nearby. To
bring the trees back to health implies that the disease can be cured.
This is not always true for the tree may be already nearly girdled, when
the disease is first noticed. A tree taken in time, however, may have
its life prolonged indefinitely though it may have the blight in some
portion of it every year. More particularly does this apply to valuable
ornamental and orchard trees.
Prof. J. Franklin Collins, Forest Pathologist in the Department of
Agriculture in Farmer's Bulletin No. 467 on "The Control of the Chestnut
Bark Disease" gives the following: "The essentials for the work are a
gouge, a mallet, a pruning knife, a pot of coal tar, and a paint brush.
In the case of a tall tree a ladder or rope, or both may be necessary
but under no circumstances should tree climbers be used, as they cause
wounds which are very favorable places for infection. Sometimes an axe,
a saw, and a long-handled tree pruner are convenient auxiliary
instruments, though practically all the cutting recommended can be done
with a gouge with a cutting edge of 1 or 1-1/2 inches. All cutting
instruments should be kept very sharp, so that a clean smooth cut may be
made at all times."
All of the discolored diseased areas in the tree should be removed.
Small branches or twigs nearly girdled are best cut off. Cankers in the
main trunk or on limbs should be gouged out. Carefulness is the prime
requisite in this work. If the disease has completely killed the
cambium, the bark should be entirely removed as well as several layers
of wood beneath the canker. By frequent examination, however, diseased
spots may be found on the tree where the mycelium of the fungus is still
in the upper layers of the bark. It is not necessary then to cut clear
to the wood, but the discolored outer bark may be removed and a layer of
healthy inner bark left beneath the cut. The sap may still flow through
this layer. The border of the diseased area is quite distinct, but
cutting should not stop here but should be continued beyond the
discolored portion into healthy bark, at least an inch. The tools should
be thoroughly sterilized by immersion in a solution of 1.1000 bichloride
of mercury, or 5 per cent solution of formaldehyde, before cutting into
the bark outside of the diseased area. Experiments have shown that a
gouge or knife may carry the spores into healthy bark and new infection
take place. Experiments are being carried on in the laboratory to
determine the length of time which spores will live in solutions of
different strengths of fungicides.
It has been shown that a cut made pointed at the top and bottom heals
much faster than one rounded. The edges of the cut should be made with
care so as not to injure the cambium. The chips of diseased bark and
wood should not be allowed to fall on the ground then to be forgotten. A
bag fastened just below the canker will collect most of this material as
it is gouged out and prevent possible reinfection, which might take
place if the material were allowed to scatter down the bark. Canvas or
burlap spread around under a small orchard tree might be sufficient to
catch all of the diseased chips of bark and wood cut out of the lower
infections. This diseased material should be burned together with
blighted branches. After completely cutting out all of the diseased
parts the cut surfaces should be either sterilized or covered with a
waterproofing which combines a fungicide with a covering. Among these
might be mentioned coal tar and creosote, or a mixture of pine tar,
linseed oil, lamp black and creosote.
The trees which have been killed by blight, or nearly girdled, have been
overlooked. These should be cut off close to the ground, the stump
peeled and the bark and unused portions of the tree burned over the
stump. The merchantable parts of the trees should be removed from the
woods promptly, as all dead unbarked wood furnishes an excellent
breeding place for the blight fungus.
Third, what means in the future can be undertaken to keep a tree
healthy, that is, to prevent reinfection. The spores may be carried by
so many agents that it is difficult to prevent reinfection. However it
is clear that the farther infected products or trees are removed from
healthy trees the less liable they are to have spores carried to them.
Cooperation with nearby owners of diseased trees will help solve this
problem.
Spraying on a large scale has only been carried on, so far as I know, on
the estate of Pierre DuPont, Jr., at Kennett Square, Pennsylvania. At
this place there are many large chestnut trees ranging from sixty to
ninety feet in height, many of which were planted some sixty-five years
ago. Mr. R. E. Wheeler started the work of cutting out diseased limbs
and cankers in October 1911, and began spraying with Bordeaux mixture in
April 1912. The formula 5-5-50, five pounds of copper sulphate and five
pounds of lime in 50 gallons of water was found to be injurious to the
foliage in the Spring. This was changed therefore, to 4-5-50, which had
one pound less of copper sulphate. This did not seem to injure the
foliage.
About 70 trees were sprayed twenty times during the season. Nearly all
of these were gone over four times to remove diseased branches and
cankers, once in October 1911, then in early summer and again in
September and November 1912. As an example take tree No. 6 which was
studied, December 14, 1912. It is 39 inches in diameter at breast
height, and approximately 70 feet in height. On this one tree six
diseased limbs were removed, and sixteen cankers were cut out. Of these
sixteen, two infections continued, that is, were not completely cut out,
and had spread; three had infections below old limbs which had been
removed, and eleven were healing over. This tree was about 1000 feet
away from other badly infected trees, though but 25 feet away from other
chestnut trees in the same row. The experiment of Mr. DuPont in spraying
shows what can be done on valuable lawn trees. On the whole, these trees
look well and healthy. Trees which were not sprayed over three times and
were within 50-100 feet from badly blighted trees, became infected in so
many different places that it will be necessary to remove them.
One of the problems to be solved next year will be that of the least
number of sprayings which will be effective in preventing new infection.
* * * * *
The Chairman: The question of the chestnut blight is now open for
discussion.
Mr. Littlepage: I should like to ask these gentlemen how far west they
have heard of chestnut blight--that is, heard of it with any degree of
authenticity, and also whether or not they care to express an opinion as
to what the prospects are in the middle west, say out in Indiana,
Illinois and Ohio?
Mr. Pierce: In answer to that question, I will say that in Pennsylvania
we have found infections in Wayne County and also in Fayette County,
both near the western extreme of the state, but those have been attended
to, very largely, and the boundaries closely determined. In Ohio there
have been several reports of the blight being found, but I don't think
either of the reports have been proven. There has been a fungus that I
have spoken of as the Connellsville fungus, that has been all around in
that neighborhood, south-western Pennsylvania and eastern Ohio.
The Chairman: Is the Connellsville fungus also _diaporthe parasitica_?
Mr. Pierce: Yes, sir. It was placed by Mr. Anderson, who did the work
on that, in the same genus as diaporthe, but he preferred the name
_endothia parasitica_.
The Chairman: The question is of changing the generic name, from
_diaporthe_, on the basis of the previously established species?
Mr. Pierce: Yes, sir, previously established species of _endothia_. It
is only a suggestion of Mr. Anderson; it was made by him. This was very
similar to the true blight fungus and when our men first went out into
the western part of the State, they reported these various cases that
came up there as chestnut blight, and none of the pathologists of our
force then were competent to determine the difference, except that the
fact was noted even then that it was not growing as a parasite in the
sense that the true blight fungus has been growing in the east.
The Chairman: That may be due to varietal differences, though, rather
than specific?
Mr. Pierce: Yes, although Mr. Anderson seemed to think it was specific.
The Chairman: Is there any further discussion? The subject is worthy of
a good deal of comment.
Mr. Pomeroy: I want to ask the speaker what the approximate cost would
be for one spraying of a tree about that size, 70 feet in height?
Mr. Pierce: We have photographs on the table there showing our eight
hundred dollar spraying machine, the same kind used in Massachusetts in
gypsy moth work. With this two men can spray about ten such trees in a
day. I haven't got it down in black and white but I figured that, on
those chestnuts at DuPont's, they sprayed about 600 gallons a day. Ten
trees a day would make it, say, with a $2.50 man, not very high for a
tree. I think it costs in all something like four dollars a tree during
the whole season, but that is a very rough estimate and the materials
are not included.
The Chairman: The cost will have to be calculated on a sentimental basis
for the ornamental trees, and on a commercial basis for the commercial
trees. The actual value of the spraying has not yet been determined.
This spraying cannot reach the mycelium in the cambium layer; if the
disease has been carried in by a beetle or woodpecker your spraying
would be ineffective.
Mr. Pierce: Yes indeed, that was just the thought Mr. Galena had,
notwithstanding the fact that they cut out all visible infections and
the trees were so blue with spray that you could see them for half a
mile.
The Chairman: But, later on, cracks and squirrel scratches and all sorts
of injuries would allow new spores to be carried in?
Mr. Pierce: Yes, sir.
Mr. Reed: The future of the chestnut depends so largely on the
conquering of this disease that no other horticultural problem of this
nut is, just at present, imperative. So far as we know, all of the
European and American varieties are highly subject to this disease, so
much so that there is no inducement to plant them, and we are waiting
for Dr. Morris and a few other hybridizers to find some hybrids, or
straight Japanese varieties, that are of sufficient merit, and of
sufficient degree of resistance to this disease, for us to have a basis
for building up the future industry. On the tables there are quite a
number of exhibits from Mr. Riehl and Mr. Endicott of Illinois. Most of
them are hybrids between the American and the Japanese species, but, so
far as we know, they have not been tried in communities where the
disease prevails. We don't know whether they are resistant or not, as
they are being grown in a section entirely outside of the area where the
blight exists. I think I am right in that, am I not, Mr. Pierce? Is
there any chestnut blight in southern Illinois?
Mr. Pierce: There has been none reported.
Mr. Reed: I think that the varieties that these men in Indiana have
originated are the most promising we know of. I think that in examining
these specimens you will agree that they are of fairly high quality and
good size, and if they prove to be resistant to the disease much may be
expected from them.
Mr. Hutt: I have not seen the chestnut blight at all. I hope that it
isn't in our section. I have heard it was brought in from some point but
I do not know whether it was identified exactly as the chestnut blight.
Mr. Pierce: I saw a specimen sent from North Carolina and it proved to
be the Collinsville fungus.
Mr. Corsan: If you remember reading Fuller's book on nuts, he reported
that the chestnut blight extended through the Carolinas but said that
chestnuts were still coming from that direction in great abundance. Up
in Canada we haven't the chestnut blight. The chestnut tree runs from
the Ohio River to the Niagara River but it doesn't cross into Michigan,
except along the Michigan Southern and Lake Shore Railroad where some
enterprising gentlemen have planted the chestnut with the tamarack
alternately all the way from Cleveland to Chicago. I examined the state
of Indiana across and from top to bottom several times in the summer and
I never saw any chestnuts there, but I have seen some newly planted
places in Michigan; near Battle Creek I saw a farm of about fifty acres.
We are having up in Ontario, beyond Toronto, a blight that has attacked
the Lombardy poplar and that looks similar to the chestnut blight. I
have been watching it for the last ten years and the tree seems to have
at last outlived it. It dies down and then a little sprout comes out
from the carcass.
The Chairman: Isn't that the poplar tree borer that always attacks the
Lombardy?
Mr. Corsan: Oh no, it's very similar to the chestnut tree blight. We can
grow chestnut trees all we like but no one has brains enough to grow
them. The farmers grow pigs and things but don't bother with chestnut
trees; consequently the chestnut blight does not exist there.
Mr. Pierce: I didn't answer a portion of Mr. Littlepage's question. Mr.
Littlepage asked whether or not the blight might be expected in the
Middle West. That depends, more or less, upon the results of the work
Pennsylvania is now carrying on. If we can keep the disease from
extending through the territory in which we are working, there is a very
good chance to keep it out of the West. If we are not successful, it may
be expected to develop, in time, over the whole chestnut range.
There seems to be a very good opportunity for growing the chestnut
commercially beyond its present range; that is, where it is so
infrequent as not to be in danger from infected growths nearby.
In the eastern part of the state different people have reported that the
blight seemed to them to be dying out and, a number of these reports
coming from a certain locality, the Commission decided to investigate
one which seemed to be better reported than the others. It was found,
after a very extensive investigation, that this dying out was true only
in the sense that it was not spreading, perhaps, as fast as it had been
spreading before. The mycelium and the spores were healthy and were
affecting the new trees in quite the same manner as the year before and
as in other parts of the state.
The Chairman: The question of controlling blight after it has appeared
is of very great consequence. Concerning any commercial proposition
with chestnuts the people are wide awake to the seriousness of the
blight. They are afraid to go into growing chestnut orchards; they have
had so many fake propositions in the past in pecan promotions that they
are afraid of chestnuts and everything else. Any proposition for
bringing forward chestnuts commercially must be a plain, simple,
straightforward statement of the truth, the whole truth and nothing but
the truth. We are ready, all through the North and East, to raise
hundreds of acres of chestnuts, such as Mr. Reed has spoken about, ones
which resist the blight, or ones which resist the blight comparatively
well.
Let us consider comparative immunity for a moment. We know how expensive
it is to manage an apple orchard, and yet, with the present high prices,
the profits on apple orchards, well managed, are great. May we not have
chestnut orchards managed with the same degree of relative expense and
the same degree of relative profit? I would like very much to hear from
some of the men who have actually raised chestnuts in orchards
concerning the relative care of the chestnut compared with the apple,
and the relative profit. I see Col. Sober here; can't you tell us about
your experience in managing the blight? Can it be managed successfully
in proportion as apple tree parasites are managed?
Col. Sober: My experience has been this; I have four hundred acres of
chestnuts in bearing. They range from five years to fifteen years old. I
find that I can control the blight easier than I can control the scale
on apple trees. If anyone doesn't believe this I invite him and all to
come to my place and see for themselves. I think I have nearly one
million seedling and grafted paragon trees. I don't think you will find
fifty affected trees on the whole place today. I have men going in every
grove at the present time who have inspected thousands of trees and
found seven that had blight on the limbs, so I know what I am speaking
about.
The Chairman: What is your method?
Col. Sober: Cutting out, cutting off anything I see; if it is really
necessary, cut the tree down; but we don't often find that necessary
because just as quick as we see any affected, or any limb dying or dead,
we cut it off. I had my groves laid out in sections of a hundred feet
wide and numbered; and I had charts made so that they can be inspected
section by section. In that manner, every tree is inspected. One
individual will inspect the trunk and another one the top. In each
section I can show you as far as we have gone. I can show you how many
trees are in each section and how many affected trees there are in that
section, or whether there are any or not. I say I can control it easier
than I can control scale and with less expense and I want that to go on
record. There is no question about it. It can be seen at my place. I go
over my groves about four times a year and have been doing it all the
time, and I don't doubt but that I discovered this disease the first of
anybody in the state, perhaps, in 1902. I was looking around to cut
scions and I saw one tree whose center was dead and around it were the
finest shoots almost that I had ever seen for grafting purposes. I went
to it and saw the center was dead. I cut some scions and today that is
one of the finest trees I've got on my place. From what I know now that
was a blighted tree.
A member: Did you paint over the scars?
Col. Sober: No sir, but we are doing it now, using white lead.
A member: How much blight is there around you?