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Coniothyrium pirina (Sacc.) Sheldon, although it occurs abundantly on apple leaf-
spots, appears to have nothing to do with their formation.

The several other fungi that were tested, such as Hendersonia sp., Coryneum sp.,
PestaloBzia sp., and Alternaria sp., proved to be non-parasitic in these experiments and
probably occur on leaf spots only as saprophytes.

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Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 189

The work of Scott and Rorer is practically confirmed by C. E. Lewis
(1909). After making, several inoculation experiments the latter writes
(1912 : 55), in agreement with Hartley (1908 b), as follows:

The results of these inoculation experiments seem to indicate that Sphaeropsis is
able to attack the leaves of orchard trees when they are inoculated early m the season
under favorable conditions for growth. No spotting has been produced by any of the
other fungi which have been tested although it has been found that they grow readily
on dead spots which have been killed by other causes.

The investigations of L M. Lewis began in 1908 and were continued by
Brooks and DeMeritt in 1909. As Brooks and DeMeritt state (1912 : 183),
the summer's work was not conclusive. Later cultural work revealed to
them great variation in the nature of growth of different strains of the
ftmgus, and also in the time required for spore production. It has been
mentioned elsewhere (page 172) that these authors found morphological
strains. This discovery led them to investigate the correlation between
the morphological and biological variations of these forms. Their final con-
clusion (page 190 of reference cited) is: "Several strains of Sphaeropsis
Malorum may be obtained, varying in general vigor and in power to produce
diseased conditions. The large-spored form, with single-loculed, ostiolate
pycnidia is largely responsible for the production of leaf spot."

The writer performed inoculation experiments in an attempt to produce
apple leaf spot during the summers of 1910 to 1913 inclusive. In the
experiments of 1 9 1 o the leaves of mature trees were inoculated in the follow-
ing manner: Pycnidia were removed from pure culture and the spores
liberated by crushing the fruiting bodies in a watch glass containing water.
The contents of the watch glass were removed to an atomizer and the
spores were sprayed on both surfaces of the leaves. In some cases the
leaves were previously wounded with a needle, in others they were left
iminjured. Data regarding the source of the fimgus, the variety and age
of the tree whose leaves were inoculated, the date of inoculation, the number
of leaves inoculated, and the results, for 1910 to 1913, are given in table 3.
It is to be noted that no moist chamber was provided in any of the
experiments of 1910. In 191 1 a series of inoculations made on May 27
resulted in infection where woimds and moisture were provided. The
method of work here was the same as in 19 10, except for the provision of
a moist chamber. This consisted of a lamp chimney, into which the in-
oculated leaves were inserted and the ends of which were closed with
damp cotton. The series of inoculations performed in July, 1910, and in
August, 191 1, should be compared. In neither case was a moist chamber
used and the results were negative. In the experiments of 191 2 and 19 13
no spotting of the foliage was obtained by artificial inoculations. The
writer has no explanation to offer. The explanation offered by Brooks



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Black Rot, Leap Spot, and Canker op Pomaceous Fruits 191

and DeMeritt (19 12) for the leaf spot problem in New Hampshire is
apparently not applicable under western New York conditions, since a
variety of morphological forms was used in the intxnilation work. The
restilts obtained indicate that there is no correlation between morpho-
logical and biological characters with respect to pathogenicity.

CANKER OF APPLE. Waitc (1898 a) was the first to attribute the canker
to a fungous parasite; he suggested that Schizophyllum commune Fr. was
the causal organism. Paddock (1899b: 183) found dark spores on the
cankers, but supposed they belonged to some saprophytic form. How-
ever, he grew this organism, as well as Schizophyllum commune, on artificial
media, and made pure culture inoculations in the following manner: A
small opening was made in the bark by means of a sterilized knife, and a
small quantity of material from bean stem cultures was inserted between
the wood and the bark. The incision was covered with moist filter paper
and kept moist for thirty-six hours. All the inoculations made in 1898
with the dark-spored fimgus on apple trees were successful; other fimgi
failed and the woimds soon healed. Paddock's conclusions are sum-
marized in the following words (page 184 of same reference): "These
experiments showed conclusively that the dark-spored fungus can pene-
trate living apple-tree bark imder certain conditions and produce a
cankered condition of apple-tree limbs and also indicated that it may pro-
duce a diseased condition of pear-tree bark." Again he says (page 185 of
same reference): ** The result of over fifty inoculations made from cul-
tures that were obtained from cankered apple tree limbs prove that the
apple-tree canker of New York apple orchards is caused by a fimgus of
the genus Sphaeropsis.'* Over one thousand inoculations were made by
him in 1899 (pages 200-201 of same reference) and only a very few gave
negative results. He further asserts that the fimgus causes canker of the
quince if the material from pure culture is inserted under the bark,
whereas imder other conditions the experiments were not conclusive.

Paddock's work was continued (1900) for the purpose of confirming
former results and to determine if possible the relationship between the
species of Sphaeropsis that occur on various plants. He obtained cultures
from apple fruit and apple bark, and inoculated the apple tree and other
plants. The results were positive, thus further proving the pathogenicity
of the organism, as well as establishing the identity of the fungus on fruit
and bark. .The conclusions reached by Paddock are essentially con-
firmed by C. E. Lewis (1909:188-189) and by McCready (1910).

The writer (1913:293) has summarized the results of earlier inoculation
work as follows:

During the past summer [1913I several inoculations have been made with cultures
from the ascospores of the ascomycetous fungus. The apple, pear, quince, crab apple,
and other plants were inoculated, in each case wounds being made to serve as infection



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192 Bulletin 379

courts. Three varieties of apples, namely Twenty Ounce, Baldwin, and ChenangQ
Strawberry, were inoculated between May 20 and Jmy 16, 1913. Eleven sets of e3cperi-
ments involving about seventy incisions were made, all of which gave positive infections,
the checks remaining healthy.

The above quotation concerns the ascomycetous fungus from apple.
A morphologically similar organism on Hamamelis virginiana did not
produce infection, as is seen from the following statement (Hesler,
1913 : 293) : "About twenty-five different inoculations were made [with
the ascomycete from H. virginiana] on all the plants mentioned above
but no infections occurred."

The writer has carried on inoculation experiments during the past
four years, both in the greenhouse and in the field, the most of the work
being directed toward the infection of bark tissues. The methods employed
have already been described (page 183). The results discussed at this
point concern only experiments in which apple strains of the ftmgus
(Physalospora Cydoniae Amaud [ = Sphaeropsis Malorum Berk.]) were
used on apple itself. The more important points in this regard are shown
in table 4, indicating the source of the strain, the variety and age of the
tree inoculated, the conditions tmder which inoculations were made, the
number of inoculations, and the general results. The infection work done
in the summers of 1910, 1911, and 1912 was not conclusive, but with
the use of various strains more satisfactory results were obtained in the
season of 1913.

It may be noted in table 4 that races of the fungus came from different
varieties of apple, isolations being made from fruit, leaf, and bark. It was
desired to determine if possible whether strains obviously living imder
saprophytic conditions, as those following winter injury and fire blight,
were capable of inducing bark injury, and to determine the nature
of the parasitism of certain other strains that appeared to be parasitic.
The results on these points are conflicting and it seems that the strains
are as variable in their biological relationships as in their morphological
characters. A race may produce infection on slightly woimded bark
after it has been living under saprophytic conditions, for example, following
fire blight. Again, those strains which in nature appear to beT








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202 Bulletin 379

ash (Fraxinus americana L,), basswood {Tilia americana L.), bittersweet
(Celastrus scandens L.), box elder (Acer negundo L.), cherry (Prunus
avium L., P. pennsylvanica L., P. virginiana L.), cherry laurel {Prunus
lauro-cerasus L.), crab (Pyrus coronaria L.), currant {Ribes sp.), dogwood
{Cornus stolonifera Michx., C. sanguinea L.), elder {Sambucus cana-
densis L.), elm {Ulmus americana L.), fig (Fictis carica L.), grape {Vitis sp.),
hawthorn (Crataegus oxyacantha L.), hop hornbeam (Ostrya virginica
[Mill.] K. Koch), lilac (Syringa vulgaris L.), maple {Acer saccharinum L.),
mulberry (Morus alba L.), oak (Quercus alba L., Q. prinus L.), osage
orange {Maclura pomifera [Raf.] Schneider), peach {Prunus persica
[L.] Stokes), pear {Pyrus communis L.), persimmon (LHospyros
virginiana L.), pine {Pinus strobus L.), plum {Prunus domestica L., P.
triflora Roxbg.), quince {Cydonia vulgaris Pers.), rose {Rosa canina L.,
Rosa sp.), rose of sharon {Hibiscus syriacus L.), spicebush {Benzoin
aestivale [L.] Nees), sumac {Rhus typhina L., /?. glabra L.), sycamore
{Platanus orientalis L.), witch-hazel {Hamamelis virginiana L.). Where
fresh material was available the writer cultured the fungus from all these
plants except three — dogwood, lilac, and rose of sharon, which have just
been collected — and these cultures were used in all cross-inoculation
experiments. The source of the cultures used, the plants inoculated, and
the results, are shown in table 5. The methods used were similar to
those described in connection with the inoculation experiments on apple
fruit (page 183). In some of the earlier experiments a moist chamber
was used consisting of a petri-dish lid, the inner margin of which was lined
with damp cotton. Later the glass lid was eliminated and a cotton cap,
made by rolling a strip of cotton about the finger, was employed. Moisture
was provided at the time of inoculation and was added daily for several
(usually from three to seven) days subsequently.

The results of cross-inoculations were not conclusive, particularly in
cases in which the fungus failed to develop. Failure to produce infection
may be accotinted for in two ways: either the fungus was not parasitic
on the plant inoculated, or conditions favorable for infection were lacking.
In many cases further trials are desirable.

In nature the fungus rarely shows a parasitic tendency on wild plants —
with the exception of Quercus prinus (see Rankin, 1914) — but it is
generally found developing on dead and fallen twigs; cankers have not
been observed which cotdd with certainty be attributed to this organism.
On cultivated plants it commonly shows the same habits as it does on wild
plants, or it may develop in healthy tissues, resulting in the formation
of a canker. Here, then, on the cultivated plants are found both sapro-
phytic and parasitic tendencies. This phenomenon is in accordance with
the commonly accepted theory that parasitism originated from sapro-



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Black Rot, Leap Spot, and Canker op Pomaceous Fruits 203

phytism. This is what is to be expected; and the theory is further sup-
ported by inoculation data which show that the strains from wild plants
may be induced to infect cultivated plants. The reverse process — that
is, the infection of wild plants with strains from either cultivated or wild
forms — has been almost wholly unsuccessful in the writer's experience.
This in the main confirms the work of Paddock (1899 b, 1900).

On certain wild plants there is found a saprophytic race which, when
carried to cultivated forms such as the apple or the pear, acts as a woimd
parasite. On cultivated plants the fimgus follows fire blight and winter
injury, and hence is a saprophyte, but the latter strains are not necessarily
obligate saprophytes since they have been induced to cause canker by
artificial inoculation. This is shown by strains 22, 38, 57, and 70 in table 4.
It does not appear, therefore, that the fungus can be segregated easily
into physiological groups, since varying degrees of parasitism are exhibited
by a given race.

From the experiments described and tabulated it is clear that there is
considerable variation in the virulence of races, but just how long a given
parasitic strain will retain this mode of life is a difficult question to answer.
The ability of the organism to act as a wound parasite, and to adapt itself
naturally to the saprophytic mode, makes it a serious pest from the stand-
point of control. Its ability to remain saprophytic indefinitely tmtil the
host is injured in some way only increases the difficulty in alleviating the
disease.

NAMES AND SYNONYMY

The work that has been done on cross-inoculations and on the mor-
phology of Sphaeropsis from several different plants makes it apparent
that there is one large polymorphic species. It is true that many inocula-
tions failed, and that two given races may differ widely in their mor-
phology; but there is considerable evidence that these characters are
variable and are not important in taxonomic considerations.

The several forms as they have been described from time to time have
been given a specific name, usually one for every host plant. This pro-
cedure has resulted in the accimiulation of a large nimiber of specific
names which could now be disposed of only by the examination of t5rpe
material of each so-called species. Several generic names have become
involved in the synonymy of the fungus, due to the indefinite limitations
and wide variations, and consequent overlapping, of certain form-genera.
Saccardo (1884 a) believed Sphaeropsis Malorum Berk, to be a Phoma,
since it was originally described by Berkeley (1836) as having yellowish
green spores. It is now known that the young spores have this color
characteristically, and furthermore Dr. C. L. Shear, who has seen Berkeley's



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204 Bulletin 379

type, has stated (in conversation with Dr. Donald Reddick, of Cornell
University) that the organism is unquestionably identical with Sphaerop-
sis Malorum as now recognized. Subsequent to Saccardo's use of the name
Phoma, this genus was divided into Phoma and Macrophoma — the former
genus containing species with spores less than 15/i long, the latter con-
taining species with spores more than 15/i long. Thus Phoma Malorum
(Berk.) Sacc. was renamed by Berlese and Voglino (1886) as Macrophoma
Malorum (Berk.) Berl. & Vogl.

It appears that certain species of Sphaeropsis have been confused with
those of Diplodia. The two genera are separated on the basis of one-
celled spores in the former and two-celled spores in the latter. But
both genera fail in their chief distinction, so that mycologists have been
misled on this point. Fuckel (1869:393) used the name Diplodia pseudo-
diplodia Fckl. in describing the fungus on branches of apple; elsewhere
(page 395 of same reference) he used Diplodia Malorum Fckl.

It has been noted previously that the pycnidium sometimes approaches
and even reaches the condition characteristic of the form-genus Botryo-
diplodia. It becomes evident that the names of certain species of this
genus may stand only as s)aionyms of Physalospora Cydoniae Amaud.

The origin of several of these S3monyms has been discussed in an earlier
paper by the writer (19 12), to which the reader is referred. At that time
it seemed desirable to attempt the selection of the name that should,
according to the rules of priority, be applied to the pycnidial stage.
Recently, however, the perfect stage of the fungus has been found, and thus
the selection of a specific name from the pycnidial forms is of minor
importance. The generic name now becomes Physalospora, and the
writer has chosen Cydoniae as the specific name. The following state-
ments bearing on this question are quoted from another paper by the writer
(1913:295):

The problem of selecting a specific name is somewhat perplexing. The organism
with which the writer is dealing strongly resembles P. Cydontae Amaud but we have
not seen his type material and there remains the question of whether his fungus has not
been previously described. In this connection a few species which suggest this possi-
bility may be noted: P. eniaxia E. & E., P. festucae (Lib.) Sacc. and P. nigropunctaia
Romell, the last on limbs of Pyrus malus according to Saccardo. Until further data
are at hand the writer is inclined to accept tentatively the name Physalospora Cydoniae
Amaud.

Soon after the above-mentioned paper appeared in print, the writer
received from Amaud a glycerin-jelly mount of his type material. It
is clear that morphologically the organism is identical with the one
described by the writer (1913) under the same name. But the question
of the specific name is still tmsettled, for it is not improbable, as stated
above, that the organism has been previously described under some other
specific name. This problem, as in the case of the several pycnidial



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Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 205

forms, would involve the study of type material, which as yet has not
been available to the writer. Under liie circumstances Amaud's specific
name will be retained tentatively by the writer. The following is a
partial list of species which are concerned in the synonymy of the fimgus;
citations to literature are also given:

Physalospora Cydoniae Amaud. Ecole Nat. d'Agr. Montpellier.
Ann. 12:7. 1912.

Spkaeria sunuichi Schw. Amer. Phil. Soc. Trans, n. s. 4:205. 1834.
Sphaeria rkuina Schw. Amer. Phil. Soc. Trans, n. s. 4: 218. 1834.
Sphaeria pomorum Schw. Amer. Phil. Soc. Trans, n. s. 4:219. 1834.
Sphaeria Malorum Berk. English Flora 5:257-258. 1836.
Diplodta pseudodiplodfa Fckl. Symbolae Mycologicae, p. 393. 1869.
Diplodia Malorum Fckl. Symbolae Mycologicae, p. 395. 1869.
Sphaeropsis Cydoniae C. & E. Grevillea 6: 84. 1878.
Sphaeropsis Malorum Peck, Sylloge Fungonun 3 : 294. 1884.

Several years ago Ellis (1880) studied the variability of Boiryosphaeria
fuligtnosa (M. & N.) E. & E. [= Sphaeria Quercuum Schw.], and came to
the conclusion that this species really included at least eighteen so-called
species. Among these may be" noted, using Ellis's nomenclature, Sphaeria
entaxia C. & E. [= Physalospora entaxia Sacc], 5. viscosa C. & E. [- P.
viscosa Sacc.], S. erraiica C. & E. [= P. erratica Sacc], Boiryosphaeria
piistulata Sacc., and others. Ellis found wide variation with respect to
stromatic formation. Sometimes the perithecia were scattered and
distinct, and again they were confluent and united in a stroma. Consider-
able range with respect to the ostiolum is also noted by Ellis (1880). But,
as stated by Ellis and Everhart (1892:547), certain forms of Boiryo-
sphaeria fuliginosa — those lacking a stroma — are removed to the genus
Physalospora. It may be that under certain conditions P. Cydoniae
develops a stroma, but such a tendency has not been observed; for this
reason the generic name Physalospora is selected.

LIFE HISTORY STUDIES

The mature morphological structures of the fimgus have been described,
so that the following paragraphs concern only the successive stages in its
development: where and in what condition the organism hibernates, the
manner in which it is disseminated, its entrance and effects on the plants
attacked, and the development of certain of its fruiting bodies.

SOURCE OP THE INOCULUM. The fimgus passes the winter as mycelium
in the tissues of the host and as pycnospores in pycnidia. If a canker
is examined in the spring when growth is resumed by the host plant,
the margin of the old lesion may show discoloration. The writer has
frequently planted bits of the bark from the edge of a canker in agar
plates, pure cultures resulting. This is evidence of the restimption of
growth of the mycelium in the old lesion. It is stated by Caesar (1909)



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2o6 Bulletin 379

that as a rule the fungus does not die out but continues to extend in every



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