selected because of their heavy-bearing tendency and because of the
excellent keeping quality of the nuts. Two of the trees bear nuts of
large size while the other three bear nuts of medium to small size.
Seeds from the five trees were planted before the use of the seedlings
as stocks in the budding experiment was planned, and since the seedlings
from each tree were planted together replication of the experiment was
not possible. However, the stock was grown in thoroughly mixed soil in a
coldframe and differences in performance of seedlings could hardly be
attributed to soil heterogeneity.
Buds from the five parent trees were placed on the five lots of their
own seedlings in all combinations of budwood and stock. The work was
done during the first week of September when the bark of both budwood
and stock was slipping yet growth had slowed down to some extent. Buds
were placed about two inches below soil level on the one-year-old
seedlings and the soil pulled back to cover the buds. Budding was done
by means of the familiar shield or T-bud method and rubber budding
strips were used as a wrap. Budwood was shipped from Albany, Ga., to
Beltsville, Md., and was damaged somewhat by high temperature in
transit, a factor which may be partially responsible for the overall low
percentage of buds that grew.
In referring to the results presented in table I, it will be noted that
considerable variation occurred in the performance of the five lots of
seedlings as stock, as well as in the take of buds from the five parent
trees. The totals in the last column on the right are all equivalent to
percentage since 100 buds were placed on each lot of seedlings. In like
manner, the totals in the bottom line are all equivalent to percentages
since 100 buds of each parent tree were used.
Seedlings of stock D were decidedly inferior to seedlings of stock C in
take of buds, and both of these lots of seedlings originated from large
nuts. Also, scion e gave a significantly lower take of buds on all lots
of seedlings than scions c or d. The scion e tree produces small nuts
whereas the scion c and d trees produce large nuts. Scions a and b are
intermediate in take of buds, and the source trees both produce small
nuts.
Discussion
At least one significant interpretation may be made from the results of
this experiment, that may partially explain the difficulties encountered
heretofore in propagating chestnuts. Using the take of buds as a
criterion it can be stated that in this experiment the five lots of
seedlings from known parents differed in their performance as stocks.
Moreover, the five parent trees used as a source of budwood differed
among themselves in the capacity of their buds to grow when placed on
comparable lots of stocks. If these results are correctly interpreted it
is clear that both the stock and the scion may influence the success or
failure of propagation technique. Doubtless both of these variables have
operated together in the propagation of existing varieties and, as would
be expected, the results have been unpredictable. It seems likely that
the grafting and budding of chestnut varieties should be worked out in
the future on the basis of using understocks derived from the seed of
special trees or clones found to be suitable sources by tests for
grafting performance.
It should be pointed out that the five trees used in this work
originated from two lots of seed imported from neighboring localities in
China and probably are closely related. The fact that significant
differences were obtained in this material furnishes basis for the
belief that great variability in the budding performance of the Chinese
chestnut is to be encountered in the many introductions that have been
made into this country.
Table I. Results of budding each of five Chinese chestnut clones on
its own seedlings and on the seedlings of four other clones. The
figure for each combination represents the number of buds that grew
out of 20 buds placed.
SCION
a b c d e Totals
S A 4 6 4 5 0 19
T B 3 2 8 4 0 17
O C 0 3 8 9 5 25
C D 1 2 3 1 1 8
K E 2 2 7 9 2 22
TOTALS 10 15 30 28 8 91
Discussion After Dr. McKay's Paper
Dr. MacDaniels: "A good scion on chestnut is one problem which we have
not solved."
Dr. Smith: "I find both Carr and Hobson difficult to graft and have
discontinued them."
Dr. Crane: "In California and Oregon they are having quite a lot of
difficulty with graft union failure with Persian walnuts. They have used
the Northern California black or Hinds walnut as root stocks. Now they
find that in some cases the union fails and results in what is known as
the black line disease. At the present time this trouble is the most
important cause of the loss of their trees."
Dr. Smith: "Zimmerman is a good bearing variety with a good nut. I find
that soil makes some difference with this variety."
Breeding Chestnut Trees: Report for 1946 and 1947
ARTHUR HARMOUNT GRAVES[5]
The chief aim of this breeding work is the development of a chestnut
tree of timber type to replace the now practically defunct American
species, _Castanea dentata_. For the principal economic value of the
chestnut was not in its edible nuts but its valuable timber, the loss of
which means at present many millions of dollars subtracted from the
assets of the American people; and when we consider the loss for all
time in the future the figures become astronomical.
[Footnote 5: Consulting Pathologist, Conn. Agric. Expt. Station; Special
Agent, Conn. Geological and Natural History Survey; and Collaborator,
Division of Forest Pathology, U. S. Dept. Agriculture.]
_The Chestnut Blight in Italy._ Early in 1946 we received a visit from
Captain John B. Woodruff, of Wilton, Connecticut, who told us that while
serving as Chairman of the Department of Agriculture and Forestry, and
Instructor in Forestry at the Army University Study Center in Florence,
Italy, he visited chestnut stands infected with the blight. _Endothia
parasitica_ was first discovered by Professor Guido Paoli in 1938 on a
private estate in Busalla, about twenty miles north of the seaport city
of Genoa. Since then the blight has been detected throughout the
province of Genoa in the legion of Liguria; and other widely separated
infections have been found. The fungus has been cultured and identified
by Professor Biraghi of the Royal Pathological Station in Rome, as
_Endothia parasitica_. It is believed to have been present in this
region for from five to eight years previous to its discovery. The
manner of its introduction into Italy is not known, but since Japan and
the U. S. have carried on considerable commerce with Italy, either or
both countries are possible sources.
The disease is spreading in Italy at a rapid rate. "By 1942 one half of
the 190,000 acres of chestnut in the province of Genoa had been infected
and spot infections had been discovered in the adjoining coastal
province of La Spezia, also in the region of Liguria."
I am devoting some space to this situation because it means so much to
the Italian people. In Italy fifteen percent of the forest is composed
of chestnut. Not only does the country use the nuts as a source of food
and income, approximately sixty million pounds being exported annually
in former years, but the young coppice shoots are used for the weaving
of baskets, older ones for poles for vineyards, still older for staves
of wine casks, and the oldest for telephone and telegraph poles. "Before
the war, chestnut flour was the principal food in many localities, but
during the war a serious food shortage forced the people in many other
areas to rely solely upon chestnut flour for weeks at a time."
Professor Aldo Pavari, Director of the _Stazione Sperimentale di
Selvicoltura_ at Florence, visited this country in the summer and fall
of 1946, under the sponsorship of the UNRRA, and spent four days with me
at our plantations, learning our methods and getting acquainted with the
blight resistant hybrids we have been developing by the breeding
together of oriental and native chestnuts. Prof. Pavari visited also the
plantation of the Division of Forest Pathology at Beltsville and
elsewhere, and other plantations in the west. In December we shipped to
Florence, Italy, nuts of our best hybrids, and in March, scions for
grafting--also this summer (1947) pollen of some of our best trees. On
October 15 of this year (1947) we sent another shipment of nuts. Thus we
may be able to give Italy the advantage of the progress we have made to
date.
Regarding the susceptibility to the blight of the European or Spanish
Chestnut (_C. sativa_) we have had the following experience. Our winter
temperatures appear to be too severe for this species. Dying back is
sure to occur, at least at our Hamden, Connecticut plantations, marked
more or less according to the degree of cold; and on the dead parts
_Endothia_ then appears, to later invade the parts still living. In 1932
I received nuts of _C. sativa_ from France from Professor Hochreutiner
of the Geneva Botanic Garden, from Professor Uldrich of the Berlin
Botanic Garden, and also from France from Dr. Guillaumin of the Jardin
de Plantes at Paris. Although I have given the resulting plants much
attention they continually die back each year so that we have only two
or three individuals that are more than six feet high. But Professor
Pavari says in recent correspondence (July 15, 1947) "Referring to
Spanish chestnuts, after we have been assured that the fungus we have
found and observed on _Castanea crenata_ in Spain is really _Endothia
parasitica_, we must admit that our hypothesis may be exact that
_Castanea vesca_ [_sativa_] presents in Spain races or types resistant
to the disease." He goes on to say that the fact that the chestnut
blight is so widespread at Naples and Avellino is at variance with my
theory that cold winters are the predisposing cause, for in the regions
mentioned the winters are mild and "very warm in comparison with those
of Connecticut." The essential fact seems to be that the European or
Spanish chestnut is very susceptible to the blight, perhaps as much so
as is our native species, but that evidently certain individuals or
races exist that are more or less resistant.
During the early part of 1947 we had a visit from Professor Cristos
Moulopoulos of the University of Salonika, Greece. Although the disease
had not then appeared in Greece, the pathologists there would like to be
ready for it when it does come.
_Pollinations in 1946 and 1947._ Without going into details, the general
purpose of the pollinations during these last two years has been to
incorporate more and more of the resistant Chinese stock into our
hybrids. Beginning in 1937, we crossed our best Japanese-American
hybrids with Chinese, and we now have a considerable number of young
saplings of flowering age, which have the pedigree: Chinese x
Japanese-American. Unfortunately, in this cross the Chinese is usually
dominant as regards habit, but not always. We have some tall,
straight-growing individuals of this combination which may well be the
forerunners of a blight-resistant forest stock for America.
Therefore, during 1946 and 1947 we have been crossing these fine Chinese
x (Japanese-Americans) with the following:
1. Our best Chinese
2. American-Chinese and Chinese-American
3. American (C. dentata)
4. Our best Japanese-Americans
5. Among themselves
For it is the ultimate aim of this work to develop a race of tall,
hardy, blight resistant individuals which will breed true and thus of
themselves re-establish the chestnut tree in the forests of Eastern
North America. As everyone knows, the re-establishment of the chestnut
as a forest tree can not be done in a few years or even a score of
years, but by continued breeding and patience and perseverance it can be
done. The materials are at hand, i.e. tall, erect growth, and blight
resistance; and with persistent effort the desired combination can be
made.
For (1) above we were fortunate in 1946 in receiving a supply of pollen
from tall-growing Chinese trees, through the kindness of Mr. Michael
Evans of Greenville, Delaware and Professor Maurice A. Blake of the New
Jersey Agricultural Experiment Station.
As a result of our pollinations in 1946, in which 72 combinations were
made, we harvested and planted in our cold frames in October 479 hybrid
nuts, a large proportion of which germinated, so that this summer (1947)
we have set out in our nurseries about 325 hybrid seedlings.
In 1947 we have made 58 combinations in which 213 branches were bagged;
October 10-13 we gathered 380 hybrid nuts resulting from these cross
pollinations. The large yield of 1947 is doubtless the result in part of
a good growing season, for there was plenty of rain--at times almost too
much--in southern Connecticut. One drawback was the cold period during
the latter part of June. From the fifteenth to the twenty-sixth the
minimum temperatures were 55 or below--on three days as low as 50. This
set back the flowering period four days to a week later than usual,
depending upon the species or hybrid.
_Cooperation in Diller's Underplanting and Girdling Method for the
Establishment of Chestnut Forest Stands._ In the 37th Annual Report of
our Association for 1946 is printed a paper by Dr. Jesse D. Diller of
the Division of Forest Pathology, U.S.D.A. entitled "Growing Chestnuts
for Timber" pp. 66-68. Many people seem to think that all you need to do
when planting a tree is to stick it in the ground--just _any_ ground.
This may be true of some kinds, but is certainly not true of the
chestnut. For best growth and development the chestnut requires a fairly
deep, well-drained soil, rich in mineral elements and humus, with a fair
degree of moisture and plenty of sunlight. Two things chestnuts will
_not_ endure are shallow soil and drought, the latter often depending on
the former.
As tree indicators of the kind of site required for the establishment of
a chestnut forest Dr. Diller has chosen yellow poplar, northern red oak,
white ash, sugar maple, and yellow birch, with spice bush as a shrub
indicator and maiden hair fern, bloodroot and other herbs as herbaceous
indicators. Using a small area of about one eighth of an acre, Dr.
Diller's plan is to girdle all the trees and then underplant with
chestnut seedlings. He says: "As the girdled overstory trees die they
gradually yield the site to the planted chestnuts in a transition that
does not greatly disturb the ecological conditions, particularly of the
forest floor. Rapid disintegration of the mantle of leaf mold is
prevented by the partial shading which the dead or dying overstory,
girdled trees cast." This may seem to some a rather drastic method, but
when so much is at stake, namely the re-establishment of the chestnut in
our forests, it would seem a justifiable experiment on a small area.
In March, 1947, we supplied Dr. Diller with one hundred seedlings, one
or two years old, of our best stock, for underplanting in two of these
selected sites, fifty seedlings each, namely on the estate of Mr. E. C.
Childs at Norfolk, Connecticut, and on lands of the T. V. A. at Norris,
Tennessee. Our best wishes for a successful blight-resistant future go
with these little trees.
_Grafting Work._ We are continuing with our method of "inarching" young
"suckers" from below a blighted area into the trunk above the lesion,
the diseased tissue of the lesion being first cut out. This method (see
Brooklyn Botanic Garden Chestnut Breeding Project. 35th Annual Report of
Northern Nut Growers Association for 1945. pp. 22-31--1945) is entirely
successful in case we desire to preserve partly resistant hybrids of
good parentage for future breeding and for scions. (Figs. 1 and 2) But
inarching of the native chestnut is for the most part unsuccessful
because the fungus grows too rapidly and girdles the stem, killing the
parts above before the inarched tips of the suckers can take hold. There
seems to be a certain relation between the amount of disease resistance
in the tree and the possibility of restoring it to health by the
inarching method.
By the common ordinary cleft-graft method, using Japanese, or better,
Chinese stock we are adding to the supply of our most desirable hybrids.
_Insect Pests._ The spring canker worm, _Paleacrita vernata_, has not
been destructive either in 1946 or 1947 and no special preventive
measures have been taken. Japanese beetles have done a little damage.
This year the first one appeared July 11. We find the best method with
these is to pick them off at dusk after they have settled themselves for
a night's sleep, dropping them into kerosene oil. Under these conditions
they will usually slip readily off the leaf into the oil. One thing I
should like to emphasize (which probably others also have noticed) is
that new beetles keep coming, day after day. Apparently the adults are
issuing from the ground all summer. Last year I found a few Japanese
beetles in November. So one must keep continually on the job all through
the season. This summer (1947) we have had a spray program of three
sprayings, August 15, 30, and September 10, with "Deenate" (fifty
percent DDT) to destroy the chestnut weevils which appeared for the
first time rather extensively in our Hamden plantations last year. (See
E. R. Leeuwen; DDT for chestnut weevils, American Fruit Grower 67: 28.
1946) This spray, which we have used on the ground as well as on the
young burs, kills Japanese beetles as well as the weevils. This fall I
have seen very few weevils in our whole crop of nuts.
The louse, _Callaphis castaneae_, appeared on July 5, 1947, at least the
leaves became so much curled that its presence was then noticed. Two
spraying on successive days with nicotine sulphate ("Black Leaf 40")
were sufficient to control it. With us this insect attacks leaves of
American stock only. Japanese-American hybrids are also susceptible, but
not Chinese-American or American-Chinese. The lice, of an orange color,
congregate in great numbers along the midrib of the leaf, sucking out
its juices.
This summer, perhaps on account of the unusual almost tropical weather
conditions--hot and humid with continually recurring showers--we have
been harassed by a new pest which has appeared in one of our plantations
only sparingly for five or six years--a mite, which Connecticut
Agricultural Experiment Station authorities say is _Paratetranychus
bicolor_. Affected leaves have a whitish or grayish color chiefly along
midrib and principal veins, due partly to the deposit of the creature's
shells on molting, and partly to injury to the tissues of the leaf.
Hexa-ethyl tetraphosphate, known in the trade as "Killex 100," was used
effectually twice as a spray. Unfortunately this chemical has no
ovicidal properties, so that a second spraying was necessary to kill the
mites newly hatched out from thousands of eggs. We are informed that DN
111 will kill the eggs as well as the mites and will kill aphids at the
same time. The mites seem to prefer Chinese chestnut leaves, but this
summer they didn't seem particular and spread from one badly infested
tree as a center.
[Illustration: Fig. 1--Japanese-American hybrid chestnut (Hammond 86-31)
34-1/2 feet in height, 16 years old. This is the same tree three years
later as that shown in figures 1 and 2, in 35th Ann. Rept. of Northern
Nut Growers Assoc. for 1944. Note healthy development, as shown by
foliage and long yearly growth. Hamden, Conn. Photo. Sept. 13, 1947 by
Louis Buhle.]
_Chinese Chestnuts._ I am enthusiastic about Chinese chestnuts as a nut
substitute for our old native chestnuts. The Chinese are quite blight
resistant. They are attacked by the blight fungus--at least most
individuals suffer at some time in their lives, and yet the fungus
doesn't thrive and the trees are able to overcome its attacks, in many
cases forming a healing wound callus around the lesions; in others the
lesion becomes simply a granular mass in which the fungus appears to be
living only in the outer bark. Cultivation, fertilization, and judicious
pruning certainly help these trees to withstand these fungus attacks. We
harvested a bumper crop last year and this from trees given us in 1929
by the Division of Forest Pathology, U.S.D.A.
[Illustration: Fig. 2.--Close-up of lower part of tree in fig. 1,
showing inarched basal shoots which at the beginning were as slender as
the leafless shoot now showing on right side, below, coming from base of
trunk. Note exposed dead part of trunk showing old canker disease. Photo
Sept. 13, 1947, by Louis Buhle.]
_Public Interest in the Problem._ Last fall, September 1946, in an
article in the Yankee Magazine, I asked for nuts and pollen of the
American chestnut. As a result the following persons from many different
parts of the country sent in nuts: Mr. Henry Hartung, Methuen, Mass.;
Mrs. Marie Garlichs, Brooklyn, from Lake Minnewaska, N. Y.; Mr. Charles
Ericson, Brooklyn, nuts from Staten Island, N. Y.; Mrs. Jay B. Nash, N.
Y. City, from Lake Sebago, Sloatsburg, N. Y.; Mr. H. W. Donnelly,
Tacoma, Wash.; Mr. George M. Hindmarsh, Kent County, R. I.; Mrs.
Steiner, Niota, Tenn.; Miss Marjorie Bacon, New Haven, Conn. from
Litchfield, Conn. through Dr. Edgar Heermance; Mr. Harold E. Willmott,
Bethel, Conn.; Mr. W. F. Jacobs, Tallahassee, Fla. (_Castanea crenata_);
Mr. P. P. Pirone, New Brunswick, N. J. (_C. crenata_); Mr. Morton F.
Sweet, Seattle, Wash. (_C. sativa_), nuts, and scions in March '47; Mr.
John I. Shafer, Sparta, Tenn. This lists shows not only the widespread
interest in the subject but also that the chestnut sprouts are still
bearing nuts. In some cases the nuts were "blind," i.e. sterile,
containing no kernel or embryo. In order to develop a good nut there
must be two chestnut trees within a reasonable distance of each other so
that cross fertilization may take place. Isolated trees will usually not
bear nuts. In other words, the chestnut is usually self sterile. We are
still planting all nuts received, labeled with the name and address of
the sender. The resulting trees are being set out in the Yale Forest in
Tolland and Windham Counties, Conn. under the direction of Mr. Basil
Plusnin, Forester in charge. Thus the possibility is being explored of
the existence of blight resistant strains of the American chestnut. When
nuts are sent they should be mailed within a few days after harvesting
and wrapped in moist cotton, peat moss or something similar. Drying of
the nut kills the embryo so that it will no longer germinate. Nuts
should be mailed to me at Chestnut Plantations, Wallingford, Conn.
Pollen of the American chestnut is getting scarce. After scouring the
vicinity of Hamden, Conn. this summer, we found a good supply at
Bethany, Conn. from native shoots. The following persons also sent us
American pollen, for which we are indeed grateful: Mr. George Gilmer,
Charlottesville, Va.; Mrs. M. E. Garlichs, Lake Minnewaska, N. Y.; Mr.
Alfred Szego, Pine Plains, N. Y.; Mr. Seward Pauley, Sumerco, W. Va.;
and Mr. Charles W. Mann, Fennville, Mich. To ship the pollen it is
necessary only to wrap small branches bearing the catkins in oiled paper
and mail to me, preferably by air mail. The catkins should be ripe, i.e.
shedding the pollen.
_Acknowledgments._ It is a pleasure to have this opportunity to express
our appreciation of the cooperation of the above mentioned persons. The
interest of these and many other persons and institutions is
encouraging. During 1946 and 1947 this project has been sponsored by the
Connecticut Geological and Natural History Survey, and we have as usual
enjoyed the cordial cooperation of the Division of Forest Pathology,
U.S.D.A. Dept. of Agriculture.
Beginning as of October 1, 1947, the work is also being sponsored by the
Connecticut Agricultural Experiment Station, New Haven, Conn. On July 1
I retired from my position as Curator of Public Instructor at the
Brooklyn Botanic Garden and shall now be able to devote my entire time
to the chestnut work. My permanent address will be: Chestnut
Plantations, Wallingford, Conn.
Chinese Chestnuts in the Chattahoochee Valley
G. S. JONES, Route 1, Box 140, Phenix City, Alabama
(Excerpts from letter to Secretary, Oct. 23, 1947.)