some of those enumerated, but at present we shall not attempt to name
them. There are many otherwise fine varieties that are not included in
this list of plums we already have, but because of a certain weakness of
the blossom they require to be intermingled with other varieties, or the
blossoms do not fertilize properly. They only bear well when conditions
are very favorable. We class such varieties as being not productive
enough.
Many attempts, with more or less--generally less--success have been made
to improve our native plums through the growing of seedlings. Mr. H.A.
Terry, of Crescent, Iowa, has done more of such work in his day than any
other one man. His method was to plant the Americana kinds, like the
DeSoto, alongside of varieties of the Hortulana type, like the Miner,
then growing seedlings from the best plums thus grown. From such cross
bred seedlings Mr. Terry originated and introduced a great many very
fine varieties. But where are they today? The Hawkeye and the Terry are
about the only ones the general public knows very much about. I will
venture this statement, that as far as I know there is no variety of
native plum in which there is an intermingling of Hortulana or Chickasaw
type that has proven productive enough to be generally profitable.
The Surprise plum belongs to this type, as also does the Terry plum. The
Terry plum we want to keep a while longer, not because it is a mortgage
lifter for the growers but because of the extraordinarily large size of
its fruit, as well as for its fine quality.
There are many injurious insects and fungous diseases that tend to make
life a burden to the man who tries to grow plums in a commercial way.
Among the insects are the plum curculio and the plum tree borer, better
known as the peach tree borer. The curculio sometimes destroys all of
the fruit on the tree, and the borer very often will destroy the whole
tree of any variety.
Among the fungous diseases are the shot hole fungus and the plum pocket
fungus, but the worst of all is that terribly destructive disease of the
plum known as the brown rot. This brown rot fungus sometimes destroys
the whole crop of certain varieties, besides injuring the trees
sometimes as well. This one disease has done more to make plum growing
unpopular than all other causes combined. Give us a cheap and efficient
remedy, one that will destroy the rot fungus and not do injury to the
foliage, buds or tree, and a long stride will have been made towards
making plum growing popular as well as profitable.
_Japanese hybrid plums._--Just now the Japanese hybrid varieties are
attracting considerable attention. One prominent Minnetonka fruit grower
said this to me about them:
"Mr. Cook, what is the use of making all of this fuss about these new
plums? Plums are only used for the purposes of making jelly anyway, and
we can usually get a dollar a bushel for our plums, and they would not
pay any more than that, no matter how large and fine they are."
This brought me up with a jerk, and I have concluded that no matter how
advanced a place in horticulture these new hybrid plums may eventually
take, that there will always be a place for our native varieties, even
if only for the purpose of making jelly.
It seems to the writer that in view of the fact that after many years'
attempt to improve our native plum through the process of seed
selection--and we have made no material advancement in that line--that
the varieties of plums that are on the way must almost of necessity be
the product of the Americana and some of the foreign varieties of plums.
Mr. Theo. Williams, of Nebraska, a few years ago originated a great many
varieties of these hybrid plums. He claimed to have upward of 5,000 of
them growing at one time. Only a few of them, however, were ever sent
out. Of these the writer has been growing for quite a number of years
the Eureka, Emerald, Stella, Omaha, B.A.Q. and some others. As a class
they are all reasonably hardy for my section. They grow rapidly, bear
early, usually the season after they are planted or the top grafts set.
They set fruit more freely and with greater regularity, as the seasons
come, than do the best of our native varieties. The fruit is of larger
size and of firmer flesh, while the quality of some of them, like the
B.A.Q., ranks rather low. The quality of others of them, like the
Emerald, is almost beyond comparison.
One year ago in answer to a question by the writer as to why the people
of Iowa did not take more interest in the planting of these hybrid plums
of Mr. Williams, Mr. C.G. Patten stated that it was because the plums
rotted so badly on the trees. Now, Mr. Patten stated the situation
exactly--most of these fine varieties are notoriously bad rotters. The
brown rot seems to be a disease of moist climate. Nature's remedy is an
abundance of sunshine and a dry atmosphere, but we cannot regulate the
climate. Prof. Hansen has sent out a few varieties of these Japanese
Americana hybrid plums, and our Supt. Haralson is doing a great work
along this line. We can only hope--but cannot expect--that Mr. Hansen's
hybrids or Mr. Haralson's hybrids as a class will prove more resistant
to the brown rot than do those of Mr. Williams of the same class.
We have hopes that from some of Mr. C.G. Patten's hybrids of the
Americana and Domestica plum will come some varieties worthy of general
planting, and also of Prof. Hansen's crosses of the Americana plum and
the Chinese apricots.
There is another class of hybrid plums that are something wonderful in
their way, beginning to bear nearly as soon as they are planted, the
very earliest of all plums to ripen its fruit, immensely productive and
of finest quality. I refer to Prof. Hansen's sand cherry hybrid plums.
My opinion is that Prof. Hansen has done all that man can do in the way
of producing elegant varieties of this class of fruit. But there is the
uncertainty, however, or perhaps I had better say the certainty, that
the brown rot will take a good portion of the crop nearly every
season--sometimes only a part of the crop, and other seasons it may take
the entire crop of these fine sand cherry hybrid plums.
Bordeaux mixture has been the one remedy advertised for years for the
control of this disease, and however well it may work in the hands of
experts of the various university farms, it has not proved uniformly
successful in the hands of the ordinary fruit grower.
Now, if some medicine should be invented, or some magic made, whereby
the brown rot would be banished from our orchards then a great many of
the fine varieties of hybrid plums would be transferred from the "plums
that are on the way" to the list of "plums that we already have." The
brown rot is a controlling factor.
Mr. Kellogg: What do you know about the Surprise?
Mr. Cook: Oh, I know a little more than I want to know about it. I have
had the Surprise a good many years.
Mr. Kellogg: You have been surprised with it?
Mr. Cook: Yes, sir, I have been surprised quite a bit, but in the last
two years since the plum crop failed there have been a few plums on the
Surprise trees, but for a great many years when other plums bore heavily
we got nothing.
Mr. Hansen: Do you know of any plum that has never had brown rot?
Mr. Cook: In my paper--as they only allowed me fifteen minutes I had to
cut it short, and I didn't say very much about the brown rot. All the
Americana plums, and all varieties of plums I have ever grown, have in
some way been susceptible to the brown rot, but some have been more
resistant than others. Now, that is one reason, I believe, why the
DeSoto takes the lead. It is less subject to the brown rot. We have here
a moist climate, and sunshine and dry atmosphere is the remedy, but some
of these varieties have such a peculiar skin it is resistant to brown
rot, and it seems certain, I don't know, if it is not on account of the
thick skin. The Wolf has a thick skin and is subject to brown rot, but
the DeSoto is not subject to that so much but more subject to the
curculio. The Japanese hybrid plums, Mr. Williams said at one time--I
saw in one of the reports--that he had Japanese plums enough to grow
fifty bushels of plums, but he generally only got a grape basket full.
He didn't think very much of them. In these sand cherry hybrids, I think
Mr. Hansen has done all that man could do.
Mr. Ludlow: What is the difference between the brown rot and the plum
pocket fungus?
Mr. Cook: Professor Stakman will tell you that in a later paper, but it
is an entirely different disease. The brown rot will work the season
through. It will commence on some varieties and work on the small plums
and work on the plums half-grown and on the full-grown. The plum pocket
fungus, it works on the plums in the spring of the year and sometimes
takes the whole crop. The Terry plum, I think, a year ago, it took the
whole crop.
Mr. Kellogg: What is the best spray you know of, how often do you apply
it and when?
Mr. Cook: Which is that for, for the brown rot?
Mr. Kellogg: Yes, for the plum generally.
Mr. Cook: Oh, I don't know of any. Let me tell you something, the plum
as a class is very susceptible to injury from sprays. I know when
Professor Luger was entomologist there was some talk of spraying plums
for curculio, and some tried it, and while it generally got the curculio
it killed the trees, and Professor Luger said that the foliage of the
plum was the more susceptible to injury from arsenical poisoning than
that of any other fruit in Minnesota. The Japanese hybrid plums, I
think, will take injury a little bit quicker than the native, and when
you come to the sand cherry plums it is extremely dangerous to spray
with anything stronger than rain water.
Prof. Hansen: I want to talk about the lime-sulphur. We will probably
have that in the next paper, only I want to say that seems to have taken
the place of the Bordeaux mixture. Brown rot, that is something that
affects the peach men too. In the state of Ohio in one year the peach
men lost a quarter of a million dollars from the brown rot, the same rot
that takes our plums. We are not the only ones that suffer from the
brown rot. Well, they kept on raising peaches because they learned to
control it, and if you are not going to spray I think you better give
up. As to trying to get something that won't take the rot, it is
something like getting a dog that won't take the fleas. (Laughter.)
Mr. Older: I had considerable experience in putting out seedling plums.
When large enough to get to bearing there wasn't a good one in the whole
lot. I got some plums, the finest I could pick out, and three years ago
they first came into bearing, and one of my neighbors went over there
when they were ripe and said they were the best plums he had seen, but
since then I have had none. I got some Emerald plums from Mr. Cook. They
were nice plums, and when he came to see them he said, "I came to see
plums, I didn't come to see apples," but the brown rot gets a good many
of them. I had some last year, and just before they ripened the brown
rot struck them, and it not only took all the fruit but got the small
branches as well. I don't know what to do about the brown rot.
Mr. Drum: I would say that my experience was something like Mr. Older's
with the sand cherry crosses. They grew until they were large and I
sprayed them with lime-sulphur. I couldn't see any injury from that
until they were grown, nearly ripe, and then in spite of me in a single
day they would turn and would mummy on the trees. I had a Hanska and
Opata and the other crosses, and they bore well. They were right close
to them, and the brown rot didn't affect them particularly.
Mr. Ludlow: I would like to ask these experts what is the life of a plum
tree. Now, an apple tree, we have them that have been bearing for forty
years, but my plum trees that were put out less than twenty years ago,
they got to be a thicket and they don't bear any large plums at all. I
introduced years ago, if you remember, the Ocheeda plum, that come from
seedlings that we found in the wild plum at Ocheeda Lake. It is a very
fine plum. I had about twelve bushels this year, and I have never seen a
bit of brown rot in that variety of plums, although the other varieties,
if they bore at all, they were brown rotted all over. The Ocheeda plum
has a very thin skin, and when the rain comes at the right time and the
sun comes out they all split open. That is its fault. But my orchard is
getting old; it is twenty years old. I had a young man work for me, and
he left me and bought a new place. I told him he could take up all the
sprouts he wanted of those Ocheeda plums. He did so and put out an
orchard of them. I think that was about ten years ago. This year while
my plums didn't average me, my Ocheedas didn't average, over an inch or
an inch and an eighth in diameter from that old orchard--he had sold out
and gone to California--but from that orchard a man that never thinks of
cultivating sold three wagon loads of the finest plums I ever saw.
Mr. Kellogg: How large were the wagons? (Laughter.)
Mr. Ludlow: Well, the ordinary wagon box. He hauled them and sold them
in town. That was from an orchard that had been left without any
cultivation.
Mr. Philips: I have heard George Kellogg say you could prove anything in
the world in a horticultural meeting. I was glad to have Mr. Cook say a
word in favor of the DeSoto. The first plum I ever bought was a DeSoto
thirty-five years ago. I planted it and never saw any brown rot on it
and had five bushels on it this year. George Kellogg saw it; I can prove
anything by him. (Laughter.) Talking about Prof. Hansen's sand cherry
crosses, I have a number of his trees. I have two in particular that are
nice trees. My wife the last three years has selected her plums from
these trees for preserving and canning. I never saw any brown rot on
them. They are nice trees, and I propose to stick by Hansen as long as
he furnishes as good stuff as that. The locality makes a great
difference in this brown rot. Some of the smaller varieties of Prof.
Hansen the brown rot takes. As some one has said, it will take the plums
and the twigs after the plums are gone. It may be that the locality has
something to do with it.
Mr. Cook: A year ago I was talking with some gentlemen in the lobby of
this hotel here and among them was a gentleman from the Iowa society,
and I was trying to urge and tell them about the great value of some of
those hybrid plums. Mr. Reeves said to me: "Mr. Cook, if you were going
out into the woods to live and could only take one variety of plum with
you, what variety would you take?" If he said five or six different
varieties I would have made a different answer but he said only one
variety, and I said it would be the DeSoto, and his answer was, "So
would any other man that has right senses about him."
Mr. Anderson: It was my pleasure some time ago, I think it was in 1896,
to set out a few plum trees, DeSotos, and those trees grew and grew
until they bore plums, and I was very much pleased with them. It was
also my fortune about that time to sell plums that another man had
grown, such varieties as the Ocheeda, the Wolf and the Wyant. They were
such beautiful plums, and I obtained such beautiful prices for them, I
was very much enthused over growing plums. I purchased a number of trees
of that variety, but up to the present time I have never marketed a
bushel of plums from any tree of that kind. The DeSotos bore plums until
they died a natural death, which was last year.
Mr. Goudy: I have one DeSoto in my orchard which is seven years old,
never had a plum on it, never had a blossom on it. What shall I do?
(Laughter.)
Mr. Ludlow: Cut it out.
Spraying Plums for Brown Rot.
PROF. E. C. STAKMAN, MINN. EXP. STATION, UNIVERSITY FARM, ST. PAUL.
The brown rot of plum is without doubt one of the important limiting
factors in plum-growing in Minnesota. In seasons favorable to its
development, losses of from twenty to fifty per cent. of the crop in
individual orchards are not uncommon.
Experiments on the control of the disease have been carried on by the
sections of "Plant Pathology and Tree Insects and Spraying," of the
Minnesota Experiment Station, since 1911. No accurate results could be
obtained in 1912 and 1915 on account of crop failure in the orchards
selected for experiment. Results are available for the years 1911, 1913
and 1914.
Brown rot is caused by a fungus (_Sclerotinia cinerea (Bon.) Wor._).
Every plum grower knows the signs of the disease on the fruit. Blossoms,
leaves and twigs may also be affected. The diseased blossoms become
brown and dry, and fall from the tree; the diseased leaves become brown
and may die. Young twigs may also be killed.
Infection may occur at blossoming-time. The amount of blossom blight
depends very largely on weather conditions; in fairly warm, moist
weather there is usually more than in drier weather. The same is true of
the rot on the fruit; during periods of muggy weather it may spread with
amazing rapidity. The rot does not usually attack the fruit until it is
nearly or quite ripe, although green plums may rot, especially if they
have been injured. It is important to know that a large percentage of
rotted plums have been injured by curculio. Counts have shown that in
many cases as much as eighty-five per cent. of the rot followed such
injury.
Rotted plums should be destroyed for two reasons: (1) The spores
produced on them may live during the winter and cause infection in the
spring; (2) if the mummies fall to the ground, late in April or early in
May of the second spring the cup fungus stage may develop on them. This
cup fungus produces a crop of spores capable of causing infection.
Spraying experiments, the summarized results of which are given here,
show that the disease can be fairly well controlled even in badly
affected orchards.
Some of the experiments were carried on in the orchards at University
Farm and some in commercial orchards. There were from twelve to
forty-five trees in each plot, and the trees on which counts were to be
made were selected before the rot appeared. The percentages given below
refer to fruit rot and do not include blossom or twig blight. The object
was to determine the times for spraying and the most effective spray
mixtures. Details are for the most part omitted, and the results of
various experiments are averaged.
For convenience the times of spraying are designated as follows:
1. When buds are still dormant.
2. When blossom buds begin to show pink.
3. When fruit is size of a pea.
4. Two weeks after third spraying.
5. When fruit begins to color.
It did not pay to apply Spray 1. In the plots on which applications 1,
2, 3 and 4 were made there was an average of 6.3 per cent. of rot, while
in those from which Spray 1 was omitted there was an average of 6.7 per
cent. rot, a difference so slight as to be negligible. Neither did Spray
4 seem to pay, there being an average of 10.9 per cent. brown rot when
it was applied and 11.4 per cent. when it was omitted.
The schedule finally adopted was therefore the application of Sprays 2,
3, and 5. Spray 2 is necessary to prevent blossom blight, although it
has not always reduced the amount of rot on the fruit. Spray 5 is the
most important in reducing the amount of rot. In all of the experiments
during three years the average amount of rot in the sprayed plots which
did not receive Spray 5, was 10.7 per cent. On the plots which received
Spray 5, with or without the other sprays, the average amount of rot was
4.6 per cent., and the average on unsprayed plots was 34.8 per cent.
Excellent results were sometimes obtained by applying only Spray 5,
although this did not, of course, have any effect on blossom blight. In
1913 the amount of brown rot in one plot which received only Spray 5 was
3.3 per cent., while in the unsprayed plots it was 33.9 per cent. In
1914 the amount of rot was reduced from 38.8 per cent. in unsprayed
plots to 6.5 per cent. in the plots to which Spray 5 was applied.
Possibly Spray 3 could be omitted without seriously interfering with
results; success in controlling the rot with Spray 5 alone seems to
indicate this. It was hoped to settle the matter during the past summer,
but spring frosts spoiled the experiment.
For the present it seems advisable to recommend the application of
Sprays 2, 3, and 5. In the first two, two and a half pounds of arsenate
of lead paste, or one and one-fourth pounds of the powder should be
added to each fifty gallons of spray mixture in order to kill the
curculio. In the plots sprayed in this way in 1911 ninety-six per cent.
of the fruit was perfect, while in the unsprayed plots only 81.6 per
cent. was perfect, and in 1913 and 1914 the amount of brown rot was
reduced from 34.8 per cent. to 4.6 per cent. Several growers have
reported excellent results from these three applications, and there is
no reason why other growers should not duplicate them.
[Illustration: Brown rot of plums showing the small, grayish brown tufts
of spores. Can be controlled by destroying mummies and thorough
spraying.]
The efficiency of various fungicides was tried. Self-boiled
lime-sulphur, 8-8-50; commercial lime-sulphur, 1 to 40; 2-4-50 and
3-4-50 Bordeaux; iron sulphide made up with 1 to 40 commercial
lime-sulphur, and iron sulphide made up with 10-10-50 self-boiled
lime-sulphur were tried and all gave good results. Commercial
lime-sulphur, 1 to 40, has been used in commercial orchards with
excellent results, and it will probably be used more than the other
spray mixtures because it is so easy to use. Possibly weaker solutions
of lime-sulphur would do just as well as 1 to 40. This will be
determined, if possible, during the summer of 1916.
Good results were obtained only when a high pressure was maintained in
spraying. There was a clearly observable difference between plots
sprayed with low pressure and those sprayed with a pressure of more than
175 pounds. For large orchards a power sprayer is desirable; for small
orchards a barrel sprayer with an air-pressure tank attached is large
enough. Such an outfit can be bought for $35 or $40 and can do good
work.
The cost of spraying three times should not exceed fifteen cents a tree.
The results from spraying orchards which contain a great deal of brown
rot and have never before been sprayed will probably not be so good the
first year as in better kept orchards, but by spraying regularly each
season the disease can be well controlled.
Mr. Cashman: Please state what you mean by 3-4-50 there.
Mr. Stakman: 3-4-50 Bordeaux mixture means three pounds of bluestone or
copper sulphate, four pounds of lime, and fifty gallons of water. The
copper sulphate should be dissolved in twenty-five gallons of water, the
best way being to put it into a sack and hang the sack in the water. The
lime should be slaked and then enough water added to make twenty-five
gallons of milk of lime. Here is where the important part of making up
the spray comes in. Two people should work together and pour the milk of
lime and the bluestone solution together so that the streams mix in
pouring. It is very important that the mixing be thorough and the
mixture should be used fresh.
The President: Do you add any Paris green at any time or arsenate of
lead?
Mr. Stakman: Always add arsenate of lead two times, when the buds are
swelling and when the plums are the size of green peas.
The President: How much?
Mr. Stakman: I would rather leave that to Professor Ruggles. We used
from 2-1/2 to 3 pounds and Mr. Ruggles, I think, found 2-1/2 pounds was
enough.
The President: That is, 2-1/2 pounds to 50 gallons of water with the
other ingredients?
Mr. Stakman: Yes.
Mr. Dyer: I would like to ask if you have ever used arsenate of lead for
spraying plums?
Mr. Stakman: In the experiments which we conducted in co-operation with
Mr. Ruggles, of the Division of Entomology, we always used arsenate of
lead in the first two sprayings to kill the curculio.
Mr. Dyer: I had quite an experience, so I want to know what your
experience was.
Mr. Stakman: We never had any trouble with it.
Mr. Dyer: I have had an experience of thirty years, and I have never
seen or had on my place any brown rot, and I never was troubled with any
curculio, and I practically always used arsenate of lead.
Mr. Cashman: Isn't it a fact if you begin spraying your plum trees when
they are young and spray them early, at the right time, you have very
little trouble with the brown rot? And spray them every year?