U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF PLANT INDUSTRY-BULLETIN NO. 121, PART VI.

B. T. GALLOWAY, Chief of Bureau.

THE IMMUNITY OF THE JAPANESE CHESTNUT
TO THE BARK DISEASE.

BY

HAVEN METCALF,

Pathologist in Charge of the Laboratory op Forest
Pathology. .

Issued February 10, 1908.

WASHINGTON :

GOVERNMENT PRINTING OFFICE.

1908. ■

CONTENTS

Page.

The extent of the bark disease --... 3

An immune variety 3

121— TI

2

B. P. I. -347.

THE IMMUNITY OF THE JAPANESE CHESTNUT
TO THE BARK DISEASE.

By Haven Metcalf, Pathologist in Charge of the Laboratory of Forest

Pathology.

THE EXTENT OF THE BARK DISEASE.

The bark disease of the chestnut, caused by the fungus DiaportJie
parasitica Murrill, has spread rapidly from Long Island, where it was
first observed, and is now reported from Connecticut, Massachusetts,
Vermont, New York as far north as Poughkeepsie, New Jersey, Penn-
sylvania, and possibly Delaware. It is no exaggeration to say that it
is at present the most threatening forest-tree disease in America.
Unless something now unforeseen occurs to check its spread, the com-
plete destruction of the chestnut orchards and forests of the country, or
at least of the Atlantic States, is only a question of a few years' time.

AN IMMUNE VARIETY.

Observations made by the writer during the past year indicate that all
varieties and species of the genus Castanea are subject to the disease
except the Japanese varieties {Castanea crenata Sieb. and Zucc). All
of the latter that have been observed in the field or tested by inocula-
tions have been found immune. This fact can hardly fail to be of
fundamental importance to the future of chestnut nut culture. Although
the nuts are distinctly inferior in flavor to the European varieties, such
as Paragon, the Japanese chestnut is already grown on a large scale as
a nut-producing tree. There are, however, many trade varieties of
dubious origin. Some of these may prove later to be subject to the
disease. Immunity tests of all known varieties of chestnuts have been
undertaken.

Attempts will also be made to hybridize the Japanese with American
and European* varieties, with the hope of combining the immunity of
the former with the desirable qualities of the latter.

However excellent as a nut and ornamental tree, the value of the
Japanese chestnut as a forest tree is doubtful. It can be recommended
only experimentally at present for forest planting. It certainly will not
take the place of the American chestnut. The tree is said to attain a
height of 50 or 60 feet in Japan. As seen in this country it is a hand-
some tree, dwarfish and compact in habit, and rather slow growing.
It has hardly had time to show how large it can grow.

121-vi 3

4 EVIMUNITY OF JAPANESE CHESTNUT TO BARK DISEASE.

The immunity of the Japanese chestnut, together with the fact that
it was first introduced and cultivated on Long Island and in the very
locality from which the disease appears to have spread, suggests the
interesting hypothesis that the disease was introduced from Japan. So
far, however, no facts have been adduced to substantiate this view.

121-vi

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