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THE UNIVERSITY

OF ILLINOIS

LIBRARY



AGRICULTURAL
LIBRARY



UNIVERSITY OF ILLINOIS

Agricultural Experiment Station



BULLETIN No. 217



AN APPLE CANKER DUE TO
CYTOSPORA



BY FEANK LINCOLN STEVENS




URBANA, ILLINOIS, MAY, 1919



CONTENTS OF BULLETIN No. 217

PAGE

DESCRIPTION OF THE CANKER 367

THE FUNGUS 368

Isolations . .". - 371

SIMILAR FUNGI ON EOSACEOUS TWIGS 372

Valsas on Kosaceous Hosts .' 372

BIBLIOGRAPHY . . . 377



AN APPLE CANKER DUE TO CYTOSPORA

BY FKANK LINCOLN STEVENS, PROFESSOR OF PLANT PATHOLOGY,
UNIVERSITY OF ILLINOIS, IN COOPERATION WITH THE DEPART-
MENT OF HORTICULTURE

A canker on young apple trees which appears capable of doing
much damage was submitted to the author for identification in the
spring of 1918. Tho noted on only a few trees, its rapid and com-
plete possession of the tree, together with the fact that it does not
agree closely with other apple-tree cankers previously described,
makes it worth while to give rather a complete statement of the
present knowledge of it.

The apple cankers were sent by Mr. G. P. Callender, of Altona,
Illinois. He stated that he had received the trees from a certain nursery
company in New York, on April 27, 1918. Requests were made of
the company that they send specimens of any cankers they might
find in their orchards, but no reply was received.

DESCRIPTION OF THE CANKER

One specimen was found on the main trunk of a young tree
about 2 cm. in diameter. The canker extended a total length of
22 cm., completely encircling the tree thruout most of that distance,
altho it extended 2 or 3 cm. farther up and down on one side of the
tree than on the other side.

There was no abrasion or wound which seemed to mark the place
of the original infection. Altho several lateral branches had been
cut off from the portion found cankered, the wounds were in all
cases nicely healing over with callous. The canker for the most
part was of a tan color, similar to that which is frequently exhibited
in young cankers of apple blotch. Portions of the canker, toward
one end, were of much darker bronzed or purplish color, altho at
the other end of the canker this color was absent.

The demarcation between the diseased and the healthy tissues
was very sharp with a slight breaking away of the diseased from
the healthy tissues. On removing the bark, a black transverse line
about 1 mm. wide was disclosed, apparently separating the healthy
from the diseased tissues. It is quite probable that the canker at
this point was in dormant condition, resting, not progressive. The
other end of the canker did not show sharp limitations between the
diseased and the healthy tissues, which gradually faded, one into
the other, and did not show externally the 2-cm., dark, purplish band
mentioned above, adjacent to this end of the canker.

367



368



BULLETIN No. 217



[May,



The canker was studded thruout its area with black pustules
having the appearance of pycnidia or perithecia. These were slightly
raised conically above the surrounding surface, were black, about
1 to 2 mm. in diameter, and were so abundant that an unbroken
area of 5 square millimeters could scarcely be found. A color photo-
graph of this twig was made June 5.

THE FUNGUS

The fungus is apparent to the eye, externally, as small black
pustules under, or erumpent thru, the cuticle. On microscopic exam-
ination these prove to be relatively large compound pycnidia made
up of numerous irregularly arranged cavities in a mass of dense
Strom atic structure. Views of the pycnidia from various sections
are shown in Figs. 1 to 11.




FIG. 1. CROSS-SECTION OF A PYCNIDIUM

Fig. 1 shows a cross-section, i.e., a section in a plane parallel
to the base of a pycnidium, which represents the condition most
frequently found. There is a large number of locules, irregular in
size and shape, but arranged in a circular manner around a sterile
area, with their longer axes along the radii. Another pycnidium
is shown in similar view in Fig. 2, and a section in the same direc-
tion but farther from the base, in Fig. 3. Fig. 4 is drawn from a
section longitudinal to the twig and parallel to the plane of the
radius of the twig, therefore cutting from the top of the pycnidium
to its base. The irregular locules are here shown, and the large




ILL. AGR. EXP. STA.



1919]



AN APPLE CANKER DUE TO CYTOSPORA



369




OOP



11



Fias. 2-11. CROSS AND VERTICAL SECTIONS THRU PYCNIDIA



370



BULLETIN No. 217



[May,



covering mass of sterile mycelium, all below the cuticle but break-
ing thru it.

Figs. 5 to 10 give similar views showing considerable variation
as to the locules and their openings into the ostiole, but a general
agreement in that the sporiferous cavities are covered in all cases
by a dense stromatic or clypeate structure. (Ectostroma, cf. Ruh-
land. 32 ) Fig. 11 shows a similar section, but nearly tangential to
the edge of a pycnidium. Fig. 12 shows the detail of the portion of
the pycnidium marked "a" in Fig. 1. The interlocular material is
seen to be a firm pseudoparenchyma, the walls of the outer cells
being somewhat thicker than the walls of the inner cells. The en-
tire inner surface of the locules is lined with a close palisade of
conidiophores, which are in the main simple and narrow, and about 17
to 20 p. long by .5 to .7 /A thick, tho in some instances they may
branch, as figured by Aderhold. 10 This conidiophore layer is shown
still more clearly in Fig. 13. Fig. 14 shows the detail of the part
marked ' ' a " in Fig. 10. It is seen that in certain parts the fungus
mycelium is loosely woven and with open interstices. Fig. 15 shows
the spores, which are produced in very great number. They are




FIG. 12. DETAIL OF PORTION OP PYCNIDIUM MARKED "A." IN FIG. 1



1919]



AN APPLE CAXKER DUE TO CYTOSPORA



371




FIG. 13. PORTION OF A CONIDIOPHORE
LAYER



hyaline, 1-celled, obtuse, quite uniform in size (7x1.6 /*), and either
straight or slightly curved.

The mycelium is thin and hyaline and by these two character-
istics is easily distinguished from the mycelium of the black-rot

fungus. Close search revealed no
ascigerous structures.

ISOLATIONS

The fungus was easily secured in
pure culture. Fragments from the
interior of a pycnidium were
placed in a drop of sterile water
and portions of this drop then
transferred to tubes of melted
corn-meal agar and poured into
Petri dishes. Thousands of pure growths were thus secured. Corn-
meal agar was also poured into Petri dishes and allowed to solidify.
Then bits of diseased tissue from below the cortex were placed upon
its surface. Invariably those bits gave rise to the same fungus se-
cured by the dilution method. The fungus thus secured in pure
culture was maintained for several months on various media. Tho
the fungus vegetated luxuriantly on various agars it did not bear
pycnidia in them, or spores of any kind. The colonies on all media
were colorless and with a floccose, aerial mycelium.

Inoculations from these pure cultures were made on apple and
other twigs (pear, rose,
blackberry, plum, and
peach) in test tubes with
a few cubic centimeters of
water to keep the culture
moist. These resulted in
rapid growth and the de-
velopment in the bark, in
about three weeks, of very
numerous pycnidia of com-
pound, chambered struc-
ture, identical with that
found in the natural can-
kers as described above,
tho under these conditions
there was always an exten-
sive development of aerial
mycelium not found under
the less humid natural con-
ditions. On all species of




FIG. 14. DETAIL OF PORTION OF PYCNIDIUM



MARKED "A" IN FIG. 10



372 BULLETIN No. 217

twigs employed, except box-elder, cherry, and 'maple, the fungus
grew well, penetrating under the cortex thruout the whole length of
the twig, some 8 to 10 cm., and breaking out with its erumpent pycnidia
over all parts of the twig. On certain twigs, e. g., those of black-
berry, tho growth was abundant and rapid, the
pycnidia were much smaller than on apple
twigs, yet no difference was noticeable in the
spores. Careful search was made in all cultures
for an ascigerous stage, but none was found.

No attempts to produce the disease on trees
in the open were made because it was not thought
wise to run any danger of giving it wider in-
troduction in this state. From the laboratory
evidence as well as from the statements of Mr.
Callender it appears that this canker is one of
very rapid development and one that might
cause serious loss should it become widespread
and suitable conditions for its development ob-

Fio. 15. SPORES




This fungus eyidently belongs to the form genus Cytospora Ehrenb.
( Cytispora Fries. ) Several Cytosporas have been referred, on more
or less conclusive evidence, to the ascigerous genus Valsa Fries. It
is therefore of interest in connection with this canker to note other
cankers that have been reported upon related hosts, due either to
Valsa or to Cytospora.

VALSAS ON ROSACEOUS HOSTS

There are more than 225 species of the genus Valsa proper noted
by Saccardo. 8 Lindau, 5 with a broader conception of the genus, says
there are about 400 species. The following list, tho not entirely com-
plete, at least contains the names of the most important of these, from
the viewpoint of pathology, that occur on Eosaceous hosts. The
synonomy and conidial relations, when stated, are as given in the arti-
cle cited. 1

1. Valsa ambiens Fries (1:565) (2:120) conidia=Cytispora carphosperma Fries

(2:120) (5)=Cytispora leucosperma Fries (25:826)=C. ambiens Fr.
(7:2,729). On apples in Europe (8:1,131) (11:278). On most deciduous
trees (5)

2. Valsa acclinis Fr. on Pyrus (8:1,130)

3. Valsa amphibola Sacc. on Pyrus (8:22,354)

4. Valsa ceuthosporae Cke. on Prunus (8:1,143)



J The first number given in parentheses r efers to the Bibliography, as does also any
number standing alone in parentheses. Numbers following indicate volume and page.



1919] AN APPLE CANKER DUE TO CYTOSPORA 373

5. Valsa ceratophora Tul. (5) (8:1,108) on broad-leaved twigs in Europe

and North America

6. Valsa eerasi Feltg. on Prunus (8:17,563)

7. Valsa cincta Fries (10) (8:1,143) (5) on Prunus in Sweden, London, Ger-

many, and France=Cytospora rubescens Fr. (33)

8. Valsa coenobitiea (de Not) Ces. and de Not (5) on broad-leaved trees in

Germany and Italy

9. Valsa clypeata Fuck, on Eubus (5) (8)

10. Valsa coronata (Hoffm.) Fr. on Crataegus (8)=Cytospora

11. Valsa crataegi Allesch. on Crataegus in Europe (5)

12. Valsa cydoniae on Cydonia vulgaris in Portugal (5)

13. Valsa excipienda (5) Karst. on Sorbus (8:1,139) Finland and Lapland

14. Valsa excorians C. and E. on Pyrus (8)

15. Valsa flavovirescens (Hoffm.) Nitz. (5) on various broad-leaved trees in

Europe

16. Valsa hoffmanni Nitz. on Crataegus (8:l,118)=Cytospora. On peach, plum,

and almond (29:485). On apricot

17. Valsa lauro-cerasi Tul.^Cytospora laufo-cerasi on Prunus (8)

18. Valsa lata (Pers.) Nitz. (5) on various broad-leaved trees in Europe

19. Valsa leucostoma (Pers.) Fries (8:1,139) (10) (22) (2:120) (5) (28)

(27:515) (4)=V. personii Nitz. (5)=Cytospora rubescens Fr. (5) (14)

(33) (ll:278)=e. leucostoma (10) (6:180). On Prunus in Europe

(34) and North America (8) (4:264). On pome and stone fruits in
Europe, Australia, and America (11:278). On peach, plum, and almond
(29). On peach, plum, apricot, and cherry (14). On cherry in Amer-
ica (9:184). On peach (4:264) (15). On cherry (10)

Valsa leucostoma Fr. var. cincta Eolfs, common on stone and pome fruits

everywhere (9:180). On peach (9:300)
Valsa leucostoma Fr. var. rubescens Eolfs. On apricot and almond

(9:157). On plum (9:360)

20. Valsa massariana de Not on Sorbus (8:l,138)=Cytospora

21. Valsa macrostoma Eehm. on Prunus (8:1,145)

22. Valsa maheleb C. and E. (8:1,137) on Prunus

23. Valsa niaura (Fr.) Nitz. (5) on wood of Prunus spinosa in Sweden and

Germany

24. Valsa microspora (Crouan) Sacc. on Crataegus (8)

25. Valsa microstoma (P.) Fr.:=(Cytospora microstoma) on Prunus (3) (7)

(8:8,111)

26. Valsa monadelpha Fr. on Prunus (8:1,128)

27. Valsa opulifolia Pk. on Spirea (8:9,449)

28. Valsa prunicola Pk. on Prunus (8:9,452)

29. Valsa prunastri (Pers.) Fr. on Prunus in Europe and North America (5)

(2:111). On plum, apricot, and pear (4:264) (13:218) (6) pycnidia=
Cytospora rubescens (2:111) (12:196). Lindau (4:264) says the con-
nection is doubtful. On apple, plum, etc. in England (11:278). On
apricot, peach, and plum (26:77)

30. Valsa rhodophila B. and Br. on Eosa (8:1,136)

31. Valsa rubi Fuck, on Eubus (8:1,109)

32. Valsa sorbi (All. and Schw.) Fries (5) on Sorbus in Europe=Cytospora

rubescens (12:196)

33. Valsa siberica Thiim. on Cotoneaster (8)

34. Valsa sorbicola Nitz. on Sorbus (8:1,124)

35. Valsa sepincola Fuck, on Eosa and Eubus (8:1,134)

36. Valsa tumidula Cke. and Pk. (5) on Crataegus and Platanus



374



BULLETIN No. 21i



[May,



In the accompanying tabulation are given the Cytosporas recorded
as such on Rosaceous hosts ; also the Cytospora-like conidial forms of
various Valsas on Rosaceae.

CYTOSPORAS AND CYTOSPORA-LIKE FORMS ON ROSACEAE
Arranged in order of minimum spore length (/*)



No.


Name


Saccardo
Vol. Page


Spore
Length X Breadth


Shape


Loculea


1


C. cerasicola Sacc


3 255


3X1


Curved


Many


2
3


C. dendritica Berl. and Vogl.
C. dst&rophordi Sacc


10 244
3 254


3-4X.5
3.5-4X1


Allantoid
Allantoid


Many
4-5


4


V '. japonica




3.5-15.7X1-2.6






5


C. ruibesccns Fr


3 253


4


Allantoid




6


V. ceratophora Tul


1 108


4X1


Allantoid


Many


7


C. Candida Speg


22 956


4r-6Xl


Curved




8


C. microstoma var. amelan-
chicris Cke


10 244


5-6






q


C. leuco'stomo, (Pers.) Fr. . .


3 254


5-6






10
11


C. capitata Sacc. and Schl.. .
V. hoffmann/i Nitz . ...


3 254
1 118


5-6
5-6X1


Oblong-
botuliform
Allantoid


Sinuous


12
13


V . microstoma (P.) Fr. ...
C. rosarwm Grev


1 111
3 253


5-6X1.4
5-6X1.5


Allantoid
Allantoid


Many
Many


14


C corphospermo, Fr .


3 274


5-6.5


Allantoid




15

16


V. rhodophila Berk, and Br.
V excipienda Karst


1 136
1 139


5-7X1
5-8X1


Allantoid


Many
Many


17


C. niphostoma Sacc


11 509


5-8X1-1.5


Allantoid


Many


IS


C. fannosa Feltg


18 297


5.5-7X1.5-2




Few


19


C cydoniae Schl. .


22 955


6




Many


4 >0


V coTonata (Hoffm ) Fr . .


1 110


6X1


Allantoid




?1


C. clypcatdt Sacc


3 252


6X1


Allantoid


Many


99


C. ambiens Sacc


3 268


6X1


Botuliform




93


V. sepincola Fcl


1 134


6X1.5


Curved


Many


24


V massaTTiana de Not


1 138


6-7X1


Allantoid




?*>


C, microspofa (Cda ) Rabh


3 253


6-7X1-1.3




Many


26


C. microstoma var. cotoneas-
tri


10 244


6-7X1.5






27


C. lauro-cerasi Fuck. var.
rainulorum Sacc


3 276


6-8X1


Botuliform




98


C. oincto, Sacc


3 254


6-9X1.5-2


Curved


Few-


99


C. cydoniae B and K


18 297


6-9X2


Allantoid


many
Many


30


C. onceps Sacc


3 255


6-10X1


Allantoid


1 few


31


C. foliioola Lib


3 275


7X1


Botuliform




39


C, mespili Sacc


11 509


7X2


Allantoid


Many


33


C. prunorum S. and S


18 297


7-8X1.5-2


Allantoid


Many


34


C. crataegicola P Brun


14 915


7-8X3


Straight




35
36


C. leucosticta Ell. and Bart.

C. cincta Sacc. var. amyg-
dalina Karst


14 916
10 245


7-10X1.5
7-10X2


Curved
Curved


Many
Many


37


C. maoularis Sacc. and Schl.


3 256


8x3


Allantoid





1919]



AN APPLE CANKER DUE TO CYTOSPORA



375



Nft


Name


Saccardo
Vol. Page


Spore
Length X Breadth-


Shape


Locules


38
W


C. oxycanthaevaT.monogynae
C. co<toneastri Thm


14 915
3 256


8-9X2-2.5
9-10X2.5


Botuliform


10-12


40


C. phyllogena P. and S


3 275


10-12X2.5-3




Many


41


C. eutypelloidffs Sacc


22 956


11-14X1.5-2


Allan toid


20-30


42
43


C. prum Ell. and Dear
C selenospOTQ, Oud


11 509
16 903


12-16X2.5-3
14X2.5


Fusoid


1-2


44


C. acharii Sacc


3 267




Curved


1


4")












46




14 915






Many


17


C Tubi Schw


3 252








IS


C. pirioola West


3 276








19


C oxycanthae Eab


3 255






Many


"iO


C. persicae Sch


3 256








51


C persona/la Fr


3 267




Curved


Many


5?,


C.leucosperma (Pers.) Fr. .


3 268








53


C. flavo-viTens Sacc


3 268




Curved




54


C flocco&a Wallr


3 254








55


C. globifera Fr


3 255








56


C. hendersonii Berk, and
Bron


3 252




Curved




57


C. leucovhthalma B. & C. .


3 255


Small


Curved





The questions of the identity of the various species of fungi
similar to this, and of their parasitism, are interesting and are worthy
of consideration. Obviously final classification must rest on rather
complete knowledge of both the ascigerous and the conidial stage
and of the biologic or host relationships. As to all of these much
uncertainty at present exists. The genus Valsa as treated by Lindau 4
contains the subgenera Eutypa, Endoxyla, Cryptosphaeria, Crypto-
valsa, Cryptosphaerella, Endoxylina, Leucostoma, Eutypella, Euvalsa,
and Valsella, chiefly distinguished from each other in stromatic char-
acters. Saccardo treats of these subgenera as genera. Many sugges-
tions as to the ascigerous connection of conidial forms have been made,
often based merely on the association of the two forms on the same
twig. Many of these claims are conflicting, assigning several conidial
species to the same Valsa, e. g., at least three Cytosporas are given as
the conidial form of V. ambiens ; or several Valsas to the same conidial
form, e. g., C. rubescens is by various writers connected with at least
four separate Valsas. As to the parasitism of these forms there has
also been much discussion and divergence of opinion. Many species,
probably a large majority of them, are purely saprophytic, growing
only on dead twigs; some follow closely on frost injury or injury
from other causes, or may be classed as wound parasites. Con-
cerning the particular question of parasitism of Valsa on drupes:
Goethe, 30 Labonte, 46 Sorauer, 48 - 49 Raschen, 47 and Zapfe, 37 held the



376 BULLETIN No. 217 [May,

fungus to be secondary, while Frank, 40 - 41 Aderhold, 10 Stewart et al., 18
Rolfs, 14 - 15> 16 and later several others, 13 - 20 - 52 have held that it was
the cause of the disease, a view that is now definitely established.

The most comprehensive articles bearing on Cytospora and Valsa
on drupes are by Aderhold 10 and Eolfs. 16 Aderhold referred the
form on drupes to Valsa leucostoma, and by extensive cultural and in-
oculation studies demonstrated its parasitism.

Rolfs studied Valsa on peach, plum, apricot, and cherry, and
showed that the forms are interinoculable ; but on the basis chiefly of
slight variations in spore measurements, tho to some extent on vari-
ations in growth on media, he distinguished two varieties, V. leu-
costoma var. cincta on cherry and peach, and V. leucostoma var.
rubescens 011 apricot and plum, a varietal distinction that has been
recognized in at least one textbook. 9 That such a varietal segregation
should exist is somewhat surprising, especially when the biologic re-
lations claimed are considered, and the question naturally arises as
to the validity, for taxonomic purposes, of the characters selected.

While the literature regarding Valsa and Cytospora on drupes is
extensive there are but few references to either as causes of disease
on cultivated pomes.

Aderhold 10 made inoculations upon apple, but makes no reference
in later publications to its natural occurrence upon that host, tho
in 1900 45 he recorded it as the cause of cankers on pear in Proskau.

Von der Byl, 53 also Evans, 56 noted Cytospora leucostoma as the
cause of die-back of apple trees in South Africa ; Darnell-Smith and
MacKinnon 38 report Valsa and Cytospora on apple in New South
Wales ; Nicholls 54 reports death of apple trees in Tasmania associated
with Valsa prunastri and Valsa ambiens ; and Ideta 23 in his textbook
gives Valsa mali as the cause of canker on apple twigs. The illustra-
tions given by Darnell-Smith agree closely with the canker under
discussion.

Cockayne 35 mentions what is probably a Valsa on apples, pears,
and other trees in New Zealand, but with inconclusive evidence as to
parasitism and as to the species of fungus involved.

To place clearly before the reader the difficulties of classification
and the necessity of taxonomic revision of these fungi the preceding
tables and lists are presented. Truly Aderhold was justified in con-
cluding that from the conidial forms alone it is impossible to make a
specific determination.

Tho the fungus here discussed agrees well with the Cytospora of
Valsa leucostoma, it is best to defer final judgment as to its specific
name. It is to be noted that many similar fungi described on other
hosts may in fact also grow on Rosaceae ; also that Cytosporoid fungi
belonging to genera of the Valsaceae other than Valsa may cause
cankers on these hosts.



1919] AN APPLE CANKER DUE TO CYTOSPORA 377

BIBLIOGRAPHY

1. MASSES, GEORGE. Diseases of Cultivated Plants and Trees. 1910.

2. COOKE, M. C. Fungoid Pests of Cultivated Plants. 1906.

3. ALLESCHER in Babenhorst, L. Kryptogamen Flora von Deutschland 1. Pt.

6. 1901.

4. LINDAU in Sorauer, P. Handbuch der Pflanzenkrankheiten, 2. 1908.

5. LINDAU in Engler and Prantl. Die Natiirlichen Pflanzenfamilien, 1. Abt. 1.

6. BANT, A. Die gummosis der Amygdalaceae. Diss. Amsterdam, 1906. In

Ztschr. Pflanzenkrank., 17, 179. 1907.

7. WINTER, G. Die Pilze in Babenhorst's Kryptogamen Flora von Deutsch-

land, etc.

8. SACCARDO, P. A. Sylloge Fungorum Omnium Hucusque Cognitorum.

9. HESLER, L. E., AND WHETZEL, H. H. Manual of Fruit Diseases. 1917.

10. ADERHOLD, B. Ueber das Kirschbaumsterben am Bhein, seine Ursachen und

seine Behandlung. Arb.a.d. Biol. Abt. fur Land und Forstw. Kais.
Gsndhtsamt., 3, 309, 363. 1903. An extensive discussion of the morph-
ology, taxonomy, and pathogenieity of the fungus, with studies of pure
cultures. See also review in Zeit. Pfk., 15, 339.

11. STEVENS, F. L. The Fungi Which Cause Plant Disease. 1913.

12. FUCKEL, L. Symbolae Mycologicae, 196. 1869.

13. DUKE OF BEDFORD AND PICKERING, S. U. Observations on a Disease of Plum

Trees. Beport on the working and results of the Woburn Experimental
Fruit Farm. Beport II, 218, London, 1900; also review in Zeit. Pfk.,
12, 177. Beports Eutypella prunastri Sacc. on plum and almond.

14. EOLFS, F. M. Die Back of Peach Trees. Science, 26, 87, July, 1907. Cyto-

spora rubescens followed by its ascigerous stage Valsa leucostoma is
given as the cause of the disease on peach and plum.

15. A Disease of Neglected Peach Trees. Mo. St. Bd. Hort., Ept. 2,

278-83. 1908. Due to Cytospora (Valsa, leucostoma}, which he thinks the
same as that reported by Stewart et al. is

16. Winter Killing of Twigs; Cankers and Sunscald of Peach Trees.

Mo. St. Fruit Exp. Sta. Bui. 17, 1-101. 1910. An extensive account
of the morphology, pure cultures, and inoculations. Two varieties of
Valsa leucostoma are erected, var. cincta on cherry and peach, var.
rubescens on apricot and plum.

17. WATERS, B. Jour. Agr. N. Zealand, 14, 190-96. 1917. Notes presence of

Valsa ambiens (?) and Valsa a/uerswaldia as saprophytes or facultative
parasites on apple and other fruit trees.

18. STEWART, F. C., EOLFS, F. M., AND HALL, F. H. A Fruit Disease Survey

of Western New York. N. Y. (Geneva) Agr. Exp. Sta. Bui. 191, 304, 318,
323. 1900. Cytospora sp. on apricot, peach, and plum.

19. MCALPINE, D. Fungus Diseases of Stone Fruit Trees in Australia and

their Treatment. Melbourne, 1902.

20. WORMALD, H. The Cytospora Disease of the Cherry. Jour. Southeast Agr.

Col., Wye, Kent., No. 12, 367-80, pi. VII-XXII. 1912. Description
of canker with plates; studies of morphology, pure cultures, and inocu-
lations. Attributed to Cytospora leucostoma=Valsa leucostoma.

21. LUSTHER, GUSTAV. Untersuchungen iiber die Ursache des Bheinischen Kirsch-

baumsterbens. Ber. d. Konigl. Lehranst. fiir Wein Obst u. Gartenbau,
Geisenheim a. Eh. (1907) 307. 1908.

22. EWERT. 1st das Eheinische Kirschensterben auf eine Pilzekrankheit zuriick-

zufiihren. Proskau. Obstbau Ztg., 13, 2-8. 1908.

23. IDETA, A. Handbook of Plant Diseases of Japan, 295. 1909. Gives Valsa


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