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The Rural Manuals
Epitep sy L. H. BAILEY
MANUAL OF TREE DISEASES
The Rural Manuals
Epitep By L. H. BAILEY
*
MANvuAL oF GARDENING — Bailey
Manuat or Farm Animats — Harper
FARM AND GARDEN Ru e-book — Bailey
MANvAL OF Fruit Insects — Slingerland and Crosby
ManvuAu or WEEDs — Georgia
THe Pruninc-MAanuat — Bailey
Manuat or Fruit Diseases — Hesler and Whetzel
Manuva or Mitk Propvucts — Stocking
MANUAL OF VEGETABLE-GARDEN InsEcTs — Crosby
and Leonard
MaANvuAL oF TREE DisEAses — Rankin
ManvuAt or Home-Maxine —Van Rensselaer, Rose,
and Canon
MANUAL
OF
TREE DISEASES
BY
We HOW AnD RAEN KEN: A.B:; Pa.D.
ASSISTANT PROFESSOR OF PLANT PATHOLOGY
NEW YORK STATE COLLEGE OF AGRICULTURE
AT CORNELL UNIVERSITY
Neto Bork
THE MACMILLAN COMPANY
1918
All rights reserved
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Copyrigut, 1918,
By THE MACMILLAN COMPANY.
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Set up and electrotyped. Published November, 1918.
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Norwood jsress
J. S. Cushing Co. — Berwick & Smith Co.
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PREFACE
THE steadily accumulating knowledge of the diseases of
trees in the United States has never been brought together and
made available to the general public. The intention of this
Manual is to describe and suggest means of control for the
tree diseases that have been most studied. Much remains to
be learned about many of these diseases, and still many more
have never been investigated. Therefore, in the treatment of
this subject there are many unavoidable limitations which the
trained reader will perceive. The diseases of fruit-trees, and of
field and vegetable crops, have received the attention of plant
pathologists in most parts of the country for many years.
The results of these investigations have been made available
to the growers of these crops in various ways. On the other
hand, the diseases of forest, shade, and ornamental trees have
been largely neglected until very recently.
Tree diseases cause enormous losses in the large tracts of
forests on which we depend for timber. The timber owner
has been slow to adopt the fundamentals of scientific forest
practice, and so far methods for the control of forest-tree
diseases have not begun to operate in reducing losses. The
owners of shade and ornamental trees are constantly con-
fronted with diseases which they wish to control. They have
become accustomed to controlling insects, but the funda-
mentals involved in the appearance of a disease and the meas-
ures necessary to protect trees from further damage are largely
puzzling to them.
An understanding of the cause of disease is essential to the
undertaking of adequate control measures. That the tree is
Vv
vi PREFACE
a living organism which requires water, food, air and sunlight
is often overlooked. Many of the diseases outside the forest
are due to the failure to recognize the importance of main-
taining suitable conditions for tree growth. The soil must
contain the proper supply of food materials, and be of a texture
which will conserve the water and air that are necessary for
healthy root development. Pavements and sod are frequently
never considered as the cause of the decline and death of trees.
Likewise, it is seldom appreciated that the smoke and poisonous
gases in the atmosphere in cities kill many trees. Also the
appearance of leaf-spots, cankers, wood-rots and root-rots in
no way explain themselves unless it is understood that in-
visible parasitic plants are growing in the living tissues of the
tree and causing their death. The technical facts regarding
the relation between a tree and its environment are more easily
comprehended than the life history of the parasites which cause
diseases. Nevertheless, the tree owner must understand the
nature of these organisms, the appearance of the symptoms
they produce, and many other facts regarding diseases before
he can intelligently attempt their control. It is hoped that
the details concerning the diseases discussed in this book will
assist to that end. The treatment has been made as simple
as possible, and only the essentials regarding the disease, which
are necessary to recognize and understand it, have been in-
cluded. A glossary is appended, which will assist in explain-
ing the more technical terms.
It has been necessary to treat the general and specific diseases
separately. Those diseases which are more or less common
to all kinds of trees are discussed in the first four chapters.
The more specific diseases will be found in the chapters follow-
ing, which are arranged alphabetically according to the com-
mon name of the various groups of trees. Cross-reference
has been freely made in the different chapters to more complete
discussions found elsewhere. This would be unnecessary if
PREFACE Vil
the book were to be read from cover to cover. The plan of the
book is intended, however, to facilitate the diagnosis of a dis-
ease of a certain kind of tree and to group the diseases of this
tree in one place where comparisons may be made. Under
each of the host-chapters, the diseases are arranged according
to the part of the tree affected and will be found in the fol-
lowing order: leaf, twig, branch, trunk and root diseases.
The reader is advised to make free use of the index, which will
facilitate the finding of those discussions unavoidably scattered.
It is regretted that specific information is not yet available
on many common tree diseases. Most of the leaf-spot diseases
have not been studied. Likewise, control measures are largely
limited to eradication methods, so far as definite reeommenda-
tions can be made. This apparently will always be the case
for the diseases of the woody parts of trees, until means of
naturally or artificially immunizing trees are devised. Spray-
ing and dusting for leaf diseases will be practicable when these
diseases are better understood. Such methods are expensive,
however, and their use will be limited for this reason.
The author is indebted to Dr. F. D. Kern, who has read
the discussions of the rust diseases and offered many helpful
suggestions. Grateful acknowledgment is also made to Mrs. W.
H. Rankin and to the following co-workers in the Department
of Plant Pathology at Cornell University for many suggestions
regarding the manuscript and for photographs loaned: Prof. H.
H. Whetzel, Dr. L. R. Hesler, Dr. Donald Reddick, Dr. V. B.
Stewart, Dr. C. T. Gregory, Dr. H. M. Fitzpatrick, and
Miss Edwina Smiley.
W. Howarp RankIN.
CorNELL UNtIversity, ITHaca, New YorRK,
September 1, 1918.
CONTENTS
CHAPTER I
SEEDLING DISEASES AND INJURIES .
Damping-off
Sun-scorch
Winter-drying
Freezing-to-death
Smothering-disease
CHAPTER II
LEAF DISEASES AND INJURIES
Winter-drying
Late frost-injury ; ,
Drought-injury and sun-scorch .
Smoke- and gas-injury
Leaf-spots
Powdery mildews
Leaf-cast of conifers .
Sooty molds
Silver-leaf .
CHAPTER III
Bopy AND BRANCH DISEASES AND INJURIES .
Freezing-to-death of twigs and bark .
Frost-cracks ~ 3 é
Sun-seald . ,
Lichen-injury
Slime-flux .
Mistletoe diseases
Electrical injuries
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CONTENTS
Galls
Wood-rots
CHAPTER IV
Root DIsEASES AND INJURIES
Drying and drowning
Freezing-to-death
Gas-injury .
Shoe-string root-rot
Mycorhizas
Roots parasitized by dowenae plants,
CHAPTER V
ALDER DISEASES
Powdery mildew of catkins
Catkin-deformation
Brown checked wood-rot
Common white wood-rot
Root-tubercles
CHAPTER VI
ARBOR-VITZ DISEASES
Seedling-blight .
Leaf-blight
Brown pocket heartwood- mot
Red-brown root- and butt-rot
CHAPTER VII
AsH DISEASES .
Leaf- and twig-rust
White heartwood-rot
CHAPTER VIII
Batp Cypress DISEASES
Pecky heartwood-rot
97
OF
CONTENTS
CHAPTER IX
Basswoop DISEASES
Powdery mildew
Leaf-spot
White sapwood-rot
Southern root-rot
CHAPTER X
BeecH DISEASES
Yellowish sapwood-rot
Common white wood-rot
Uniform white sapwood-rot
White butt-rot .
Parasitized roots
CHAPTER XI
Brircw DISEASES
Leaf rust
Yellow jeaf blister
Red leaf-blister .
Powdery sapwood-rot
Yellowish sapwood-rot
Common white wood-rot
Brown heartwood-rot
White butt-rot .
CHAPTER XII
BucKEYE DISEASES
Leaf-blotch
Powdery mildew
Curled leaf-blight and wieches’ aroaw
White sapwood-rot
CHAPTER XIII
Butternut DISEASES
Leaf-spot
Xl CONTENTS
Common white wood-rot
Brown checked wood-rot
CHAPTER XIV
CATALPA DISEASES
Yellowish wood-rot
Brown butt-rot .
CHAPTER XV
CrepAR DISEASES
Eastern leaf-rust
Western leaf-rust
Brown felt-blight
Eastern witches’-broom
Western twig-blight and relion feroemt
Branch-swellings
Pecky heartwood-rot
CHAPTER XVI
CHESTNUT DISEASES
Large leaf-spot .
Twig-blight
Endothia canker
Strumella canker
Brown checked wood-rot
Straw-colored heartwood-rot
White piped butt-rot
CHAPTER XVII
Eum DISEASES
Leaf-spot
Powdery mildews
Brown wood-rot
CHAPTER XVIII
Fir DISEASES .
Leaf blister-rusts
CONTENTS
Leaf-rusts .
Leaf-cast 3
Rust witches’-broom .
Gray mold twig-blight
Mistletoe burl and witches’-broom
Pecky wood-rot .
Red-brown sapwood-rot
Stringy red-brown heartwood-rot
Brown pocket heartwood-rot
Brown heartwood-rot
Brown root- and butt-rot .
Red-brown root- and butt-rot
Yellow root-rot .
CHAPTER XIX
HacKBeRRY DISEASES
Powdery mildews
Witches’-broom
CHAPTER XX
Hemuock DISEASES
Seedling root-rot
Leaf-blight
Brown-mold leaf Blipht
Leaf and cone blister-rusts
Leaf-, cone- and twig-rusts
Red-brown sapwood-rot
Stringy red-brown heartwood-rot
Brown pocket heartwood-rot
Cuboidal wood-rot :
Red-brown root- and butt-rot
s
CHAPTER XXI
Hickory DISEASES .
Leaf-mildew and witches’ Sere
Common white wood-rot
X1V CONTENTS
CHAPTER XXII
PAGE
JUNIPER DISEASES . : : ‘ : : : 5 . 190
Seedling twig-blight . 4 ‘ : : : ; ‘ - 190
Leaf- and stem-rusts (general) . : . i ‘i : . 192
Leaf- and twig-rusts . ‘ : ; ‘ : ; : . 196
Cedar-apples. : : : ‘ ; P : ‘ . 197
Rust witches’-brooms : : : : ; : , « 200
Branch-galls.. : : s : ; ; ; » 200
Fusiform branch-sw alah : ‘ ; ; : 2 . 202
White bark : : : ; : ‘ ‘ , . 204
Brown pocket heartw Sadao : : : : : 5 . 204
White pocket heartwood-rot : : : ; F - 206
Yellow wood-rot ; ; : F en : : » 208
Stringy brown wood-rot. : ‘ $ ‘ ‘ : . 209
Basal heartwood-rot . ; : ; é : : ; « 210
CHAPTER XXIII
LarcH DISEASES. : : 5 : : ‘ ; , pees
Seedling root-rot : : : , c : ; : - 22
Leaf-rusts . : , j ‘ , . 212
Mistletoe burl and witches Riraorn F ; = ; ‘ . 214
Pecky wood-rot ‘ ; F : : : : : « 2S
Red-brown sapwood-rot . : : F : é é Ae alls
Brown heartwood-rot ; , : : é : : +) 2G
Brown pocket heartwood-rot 2 : . ‘ ; oe
Red-brown root- and butt-rot . : ‘ ‘ Z < oro eles
Yellow root-rot . ‘ : : ; ; , : , « 218
CHAPTER XXIV
Locust DISEASES . : : ‘ é ‘ : : : . 1219
Yellow wood-rot : : ; 5 : : : é « “219
Brown checked wood-rot . ; : ; : F ‘ 2 22
Root-tubercles . 4 . , 3 ‘ : ; ‘ . 22
CHAPTER XXV
Marie DISEASES. ‘ : , : : : : : : 1228
Tar leaf-spot . : : ‘ ; : 4 : : . | 223
CONTENTS XV
PAGE
Black-specked was 225
Leaf-spots . 226
Powdery mildews 227.
Leaf-blight 228
Canker 229
Wilt . 3 231
Common white youdtot 232
Brown checked wood-rot 232
White strand wood-rot 233
Uniform white sapwood-rot 234
White streaked sapwood-rot Dow
White butt-rot . : : : 236
CHAPTER XXVI
Oak DISEASES . , ; : : : : ; ; ; Ae PBI
Leaf-blight : : ; : : ? : ; : Bay
Leaf-blister : : ; . : : ; , : 3239
Powdery mildews : ‘ : : : : 5 : . 2AT
Brown mildew . : . : F ; . : 2 5 PAS
Large leaf-spot . : : : : : : ; ji . 248
Twig-blight ; ‘ ‘ 3 ; F é : : . 244
Strumella canker ‘ : 3 , : ? : : » 245
Brown checked wood-rot . s : : : : ; 5 ii
Common white wood-rot . : : P : : : 5 PRO
White pocket heartwood-rot —. ‘ : ; ‘ : . 250
String and ray butt-rot. ‘ ‘ ; : : ; 2 252
Wet heartwood-rot . : ? : : . : : 5 a!
Honeycomb heartwood-rot , : ; , : ‘ 200
Soft heartwood-rot . ; x F : 3 ; : 5 ARI
White piped butt-rot . ‘ ‘ ; i : ‘ : > (258
Straw-colored butt-rot ‘ ; : ; : é i . 259
White wood-rot . : : 5 : ; : : E . 260
White butt-rot . : : : ; : : : A -- 260
White root-rot .. . ‘ : : ‘ : : f Le oll
CHAPTER XXVII
PINE DISEASES : : - : , 5 ‘ : : . 264
Seedling root-rot ‘ ; : 2 ‘ : ; 3 . 264
Xvi CONTENTS
PACE
Leaf blister-rusts 5 ; : : ; ‘ A : . 265
Leaf-rust . ; , ‘ 5 " : < 3 « 200
Leaf-cast of white pine’. ; : : : : ; . 270
Brown felt-blight f : : : ee!
Leaf-cast and witches’-broom ae Sei vellone pine : : aad
Twig-blight : : : : : F ‘ . 2h2
Mistletoe burls and witches: ireama : : : F «2273
Blister-rust of five-needle pines . : ‘ : i . ~ QA
Sweet-fern rust . : : ; E : F : ; 28
Comandra*¥ust . ; : : 3 ; ; i : ne Sie
Castillejasrust . : ; . , 2 : ‘ é . 285
Oak rust . ‘ : : ; : : : ; : . S2RF
Pinon blister-rust ; : : : ‘ : : ; . 290
Basal canker. , é : : : é d : ; 290
Pecky wood-rot : : : : oy MY oe : ‘ . 291
Red-brown sapwood-rot . : : : ; : ‘ . 292
Brown heartwood-rot é ; ; 5 : , 2 » 292
Brown pocket heartwood-rot . ‘ , ‘ ‘ 5 . 293
Red-ray wood-rot : ‘ ; i 5 : ‘ . 293
Red-brown root- and butt-rot . j : ; : ; . 294
Yellow root-rot . : - : ; ; : i ; . 296
Brown root- and butt-rot . : : : : : : . 296
CHAPTER XXVIII
PopLarR DISEASES . ‘ ; : ; : P ‘ : . 298
Leaf-rusts . ‘ ; ‘ : : : : : : . 298
Powdery mildew : : : A 4 : : : . 300
Yellow leaf-blister . : : ; : : rc 4 UU)
Catkin-deformation . : : ; : : : 5 5 lil
Canker : : 5 : : : : : ; $ . oul
Limb-gall . : 3 : : 5 : : ; : . 3804
Common white wood-rot . : 2 - : : 2 . 304
White pocket heartwood-rot ‘ : . ; : . 310
White butt-rot . 3 : : : : ; : é Se asi;
CHAPTER XXIX
SPRUCE DISEASES . : : 4 : 5 : : ‘ 5 ells:
Seedling twig-blight . - : : = - : : . 313
CONTENTS
Leaf blister-rusts
Leaf-rust
Brown felt- blight
Leaf- and twig-blight
Cone-rust .
Rust witches’ Berane.
Mistletoe witches’-broom .
Pecky wood-rot
Red-brown sapwood-rot
Stringy red-brown heartwood-rot
Brown pocket heartwood-rot
Cuboidal wood-rot
Brown root- and butt-rot .
Red-brown root- and butt-rot
Yellow root-rot .
CHAPTER XXX
SYCAMORE OR PLANE TREE DISEASES
Leaf- and twig-blight
CHAPTER XXXI
WALNUT DISEASES
Leaf-spot
Common white wood- 16
Brown checked wood-rot
CHAPTER XXXII
WILLow DISEASES
Powdery mildews
Leaf-rusts .
Tar leaf-spot
Common white wood-rot
White wood-rot
CHAPTER XXXIII
TREE SURGERY
Pruning
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XVili CONTENTS
Disinfecting wounds .
Wound dressings
Lesion excision .
Cavity treatments
CHAPTER XXXIV
SPRAYING AND DusTING FoR LEAF DISEASES
APPENDIX
Common names of trees
Synonymy of polypore names
Glossary . : A : : :
General bibliography of tree diseases .
INDEX
PAGE
348
048
ool
300
307
361
361
364
365
367
ovl
SR OO, Se Stee ea
ILLUSTRATIONS
Frost-crack in a maple
Frost-crack healed over in summer
Mistletoe growing on white fir
Galls on branch of oak
Polypore fruiting-body showing : spores
Shoe-string root-rot on pine
Young toadstools of Armillaria mailed
Mature fruiting-body of see root-rot fungus .
Ash rust
Leaf-spot of basew oad (by V. iB. Stew A
. Fruiting-body of Fomes fomentarius ;
. Beech wood decayed by Fomes applanatus
. Fruiting-body of Polyporus betulinus
. Leaf-blotch of horse chestnut
. Leaf-spot of butternut
. Brown felt-blight
. Endothia canker of chesiane
. Mycelial fans between bark and w a
. Spore-horns of chestnut canker fungus
. Perithecial stage of chestnut canker fungus
. Leaf-spot of elm (by H. M. Fitzpatrick)
. Powdery mildew of elm ;
3. Pecky wood-rot, early stage
. Pecky wood-rot in Douglas fir :
. Fruiting-body of Echinodontium tinctorium
. Brown heartwood-rot of Douglas fir .
. Fruiting-bodies of Rhizina undulata (after Bupa
. Cuboidal wood-rot of hemlock (by G. F. Atkinson)
. Cedar-apple fungus on wild apple leaves (after Weimer)
Cedar-apple fungus on haw leaf
. Cedar-apples. — early stages of development (after Wecimen)
2. Cedar-apples in late autumn (after Weimer)
. Cedar-apple in spring with spore-horns (after Weiner)
X1x
PAGE
50
50
56
63
68
79
80
81
94
102
106
109
114
119
125
131
142
143
145
146
12
153
164
164
167
169
178
186
194
195
197
197
198
ILLUSTRATIONS
. Fruiting-bodies of Fomes roseus
5. Fruiting-body of Fomes rimosus
Tar leaf-spot of maple
. Leaf-spot of maple caused by Piyllosticala minima
Leaf-spot of maple caused by Glaosporiwm apocr as m pues: H. M.
Fitzpatrick) , ;
Leaf-blight of maple .
. Nectria canker on maple i
. Sections through Nectria canker on mane
. Sections through trunk of maple affected by wilt
3. Section through fruiting-body of Hydnum septentrionale
. Leaf-blight of oak tx.
5. Leaf-blister of oak (by H. H. Whetzel)
. Powdery mildew on oak leaf (by G. F. Ailaneen)
. Twig-canker on oak :
. Brown checked wood-rot in oak as G. iH Adlaneoni
. Fruiting-bodies of Polyporus sulphureus :
. Fruiting-body of Polyporus Berkeleyi
. Fruiting-body of Polyporus dr yadeus
2. Blister-rust on twig of white pine (after Hele aaa Whetzel)
Blister-rust on trunk of white pine
. Uredinial stage of Cronartiwm ribicola on currant Gites Hester aa
Whetzel)
5. Telial stage of Cronartium ribicales on veureent (alter Headee Pa
Whetzel)
Blister-rust on lodgepole pine
. Limb-galls on poplar
Common white wood-rot (after Ejeaior ea Whetsel)
9. Fruiting-body of Fomes igniarius
Fruiting-body of Fomes igniarius (form éalled Fores iigeieree
. Section through fruiting-body of Fomes igniarius
2. Witches’-broom on black spruce
3. Mistletoe witches’-brooms on black spruce
. Pecky wood-rot in spruce .
5. Pecky wood-rot, advanced stage
. Leaf-blight of syeamore
. Sycamore tree defoliated by eae iis te fangs (a M. F. Barks)
. Cankers on small sycamore twigs : F
. Cankers on limbs of sycamore
. Powdery mildew on willow leaves &, G. F. Dy eigea
PAGE
205
220
224
226
227
228
229
230
231
235
238
239
242
244
248
249
253
262
276
277
278
278
286
304
306
307
308
309
322
323
325
326
J04
325
336
307
342
MANUAL OF TREE DISEASES
MANUAL OF TREE DISEASES
CHAPTER I
SEEDLING DISEASES AND INJURIES
From the very beginning of the life of a tree, the seedling is
subject to many more or less serious diseases. Damping-off
may cause death, even before the tiny plant has grown above
the surface of the soil. Later, if damping-off is avoided, va-
rious blights are common in the seed- and transplant-bed.
Although many pathogenes are known to cause seedling dis-
eases, it is very difficult for the layman to identify the trouble
any more accurately than by the general symptoms of damping-
off or blight. Damping-off symptoms are mostly due to the
activities of specific soil-harbored fungi. Blight symptoms
may be produced by various rapidly spreading fungi, or by
adverse moisture and temperature conditions. After a careful
comparison of the blight symptoms produced by environmental
conditions, with the usual symptoms caused by parasites,
the layman should be able to distinguish between these two
general types of seedling blights. In some cases, the seedlings
of certain kinds of trees are affected by well-known specific
leaf-, stem- or root-parasites which cause blight. These dis-
eases are described in the chapter on the diseases of the species
of tree affected. Otherwise, the damping-off and blights such
as sun-scorch, winter-drying and freezing-to-death of seedlings
of both coniferous and deciduous trees, are treated below.
B 1
2 MANUAL OF TREE DISEASES
DampINnG-OFrr
Caused by various species of fungi
The damping-off diseases have commanded serious atten-
tion from all persons who have attempted to grow seedlings,
especially of conifers. Schreger, in an early compilation of the
facts known about tree diseases, published in 1795, writes about
the damping-off of beech seedlings. Since the growing of large
quantities of seedlings for forest planting was first attempted in
Europe, the earlier literature on damping-off appeared mostly in
foreign languages. American nurserymen have grown small
quantities for ornamental and shade tree stock for many years.
The increasing demands for large quantities for forest planting
were not supplied, however, by the production of the commer-
cial nurserymen. It is thought that the small quantity pro-
duced and high prices demanded for the stock were due mainly
to the difficulties of handling the damping-off diseases. To-day
the growing of coniferous seedlings in federal and state nurseries
has developed until millions of trees are produced yearly. It
was during the development of these specialized nurseries that
the damping-off diseases in this country were studied, and
methods evolved for their control.
Damping-off is a universal seedling trouble. The fungi
causing the disease are common soil-harbored organisms asso-
ciated with decaying plant material. Seedlings grown in new
soil may suffer from damping-off as severely as those in beds
which produced diseased plants the previous year. The seed-
lings of coniferous trees in general show marked susceptibility,
while those of deciduous trees are less often attacked. Beech
and maple seedlings, however, often suffer. When no pre-
cautions are taken, damping-off may kill practically the entire
stand of seedlings, especially when large numbers are grown
under crowded conditions.
SEEDLING DISEASES AND INJURIES 3
Symptoms.
The critical period in the development of tree seedlings, so
far as damping-off is concerned, extends from the time of the
germination of the seed until the stem-tissues become woody,
—a period of one or two months. Usually the first indication
of damping-off is a water-soaked or brown area of decaying
tissue in the stem, near the surface of the ground. If the dis-
ease occurs very early in the development of the plants, the
stems may be killed before their tips emerge from the ground.
Often, also, the lesion originates just below the surface of the
soil after the plant has pushed out, and wilting of the plant is
the first sign of the trouble. Wherever the lesion may occur,
the diseased stem-tissue soon collapses and allows the plant to
fall over, while further disintegration of the tissue results in
the death of the seedling. Root-rot may accompany damping-
off and often is only another indication of the work of the same
fungus. In the case of deciduous trees, especially the beech,
the first lesions may show as cotyledon-spots. These lesions
soon enlarge, however, so that the stem is involved and damping-
off follows. Under conditions favorable for the development
of damping-off fungi, large circular areas of dead plants appear
and only a few days are sufficient for the spread of the patho-
gene from a few centers to all parts of the seed-bed.
Cause of damping-off.
Numerous species of fungi have been found to cause damp-
ing-off. In general these fungi have no restricted host-range,
and are so prevalent and omnivorous that seedling crops uni-
versally suffer. In this country most of the work on these
diseases has been done with conifers. Numerous species and
forms of fungi belonging to the genus Fusarium have been
found to be the most common cause. Pythiwm debaryanum
Hesse and species of Rhizoctonia have also been found to be
important damping-off pathogenes in certain cases. In Europe,
4 MANUAL OF TREE DISEASES
Phytophthora omnivora de Bary is the most common on both
coniferous and deciduous tree seedlings. This latter fungus is
widely distributed in this country and may be found to be of
importance with further investigations on deciduous seedlings.
It is to be assumed that many other species of fungi may also
at times produce damping-off in tree seedlings, since Thielavia
basicola (B. and Br.) Zopf and species of Botrytis, Colle-
totrichum, Volutella and other fungi have been discovered
producing this disease in seedlings of other crops. Numerous
inoculation experiments by various workers have established
the power of the above mentioned pathogenes to cause this
type of disease.
The causal fungi represent many widely different types of
life history. The parasitism of these fungi is of a very primi-
tive sort. This is evidenced by their usual saprophytic char-
acter, extreme destructiveness to the host-plant, wide host-
range and the fact that they are limited in their activities to
very young seedlings, which have not developed the more com-
plex physical and chemical nature of older plants. These
fungi exist ordinarily as common saprophytes on decaying
vegetable matter in the soil and thus their mycelium is the
main infective material. Various types of spores are formed
by the different species of fungi concerned in damping-off, but
they are rarely instrumental in the inoculation of healthy
plants. These spores, however, are mainly useful in carrying
the fungus over winter and through other conditions detrimental
to vegetative growth. The entire life history of these fungi
then, so far as explaining the appearance and development of
damping-off in seedling-beds, is confined largely to the growth
of the mycelium through or on the surface of the soil, from one
plant to another. This manner of spreading is often well il-
lustrated when all the plants in a single row are destroyed and
only occasional plants in the adjacent rows are affected. Al-
though some one or several of the damping-off fungi are generally
SEEDLING DISEASES AND INJURIES 5
present in all soils, their presence may not become evident if
conditions are adverse to their development. All damping-off
pathogenes are markedly influenced by temperature, soil
moisture and the humidity of the atmosphere. A relatively
high temperature, moist and compact soil and a humid at-
mosphere furnish ideal conditions for these fungi, while lower
temperatures and drier conditions of soil and atmosphere may
check successfully a destructive development of these organisms
after some damage has already been accomplished.
Control.
Since damping-off may be caused by any one of numerous
species of fungi and may occur under such variable conditions,
no general rules for treatment can be prescribed which will
apply in all cases. The control of damping-off may be effected
by one of two general methods: (1) protection of the seedlings
by maintaining conditions of temperature and moisture which
interfere with the destructive development of the pathogenes ;
(2) eradication of the pathogenes from the soil of the seed-bed
by means of disinfectants.
(1) Protection.
Every investigator agrees that much can be accomplished
in the control of damping-off by giving careful attention to
the manipulation of soil moisture, temperature and atmospheric
humidity. At the same time, it is realized that one may
find it difficult, in regulating the amount of moisture and
other factors, to preserve the equilibrium necessary to grow
seedlings, and at the same time to prevent the growth of the
fungi. The following method of procedure is advised :
Each seed-bed should be provided with upright frame, with
wire-mesh sides and removable top, which can be made into
half-shade or full-shade by laying on laths.
The seed should be sown on the surface of the prepared
soil and covered to the desired depth with clean dry sand
6 MANUAL OF TREE DISEASES
obtained by digging three or four feet below the surface. This
furnishes a surfacing for the bed which is sterile and easy to
keep relatively dry.
The beds should be covered and kept moist enough to pro-
mote germination. After the seeds have germinated, partial
shade should be furnished on bright days but should be removed
in cloudy weather, in order to allow as much evaporation as
possible from the surface of the soil. These precautions are
especially important if it is warm and rainy. If the surface
of the soil does not dry sufficiently, more clean coarse sand may
be scattered over it.
(2) Eradication.
Two general eradication methods are recommended for the
control of damping-off: (1) disinfection of the soil before
planting, usually with formaldehyde; and, (2) for coniferous
seedlings only, disinfection at the time of planting with sulfuric
acid.
If damping-off has previously occurred in a bed, the best
practice is to remove the top-soil and substitute new soil. This
is desirable since a large accumulation of the resting spores of
the causal pathogene is to be expected after a severe outbreak.
The following steps are essential for thorough disinfection :
A solution of formalin should be made by adding one gallon
of formalin (which should contain forty per cent formaldehyde
by volume) to fifty gallons of water.
The soil should be prepared by forking or raking. The
formalin solution may then be applied to the bed with a sprin-
kling-can, using about two quarts for every square foot of soil
to be treated. If the nature of the soil is such that this amount
cannot be put on in one application, as much as possible should
be applied without making the soil muddy and the remainder
added a few hours later.
The bed should be covered as securely as possible with
heavy paper or other impervious material for forty-eight hours.
SEEDLING DISEASES AND INJURIES 7
The active substance in the formalin solution is liberated as a
gas (formaldehyde). The cover is necessary in order to retain
this gas in the soil for a period sufficient to kill the pathogenes.
Three or four days after the cover is removed, the soil should
be thoroughly forked and allowed to stand in a loosened con-
dition for another day or two, after which the bed may be
prepared for sowing the seed. It is important to time the
application of the formalin so that the seed may be sown as
soon as the operations above described are completed, since
the soil may become contaminated again from surrounding
soil. Experience shows that beds contaminated after dis-
infection may exhibit greater loss than those not disinfected.
The increased virulence of damping-off fungi in disinfected
beds is thought to be due to the lack of competition with
other soil organisms which have been killed by the disin-
fectant. With ordinary care, however, under most condi-
tions a clean crop of seedlings is assured if the disinfection
is thorough. Even after carefully disinfecting the soil, all
the measures advised above under Protection should be ob-
served (see page 5).
The application of sulfuric acid to the soil at the time of
seeding has given good results in controlling damping-off in
coniferous seed-beds. Sulfuric acid should never be used on
deciduous seedlings. The amount of acid used with safety
will necessarily vary with the natural acidity or alkalinity of
the soil. A too heavy application of sulfuric acid will cause
injury to the seedlings. This method is more difficult to handle
than the formalin treatment because in loose sandy soils the
capillary movement of the water will bring the acid to the
surface and produce there a concentrated solution, which must
be counteracted by daily watering. With heavier soils, no wa-
tering seems necessary from the experiments so far reported.
With the two uncertain factors in mind, the natural acidity
or alkalinity and the physical nature of the soil to be treated,
8 MANUAL OF TREE DISEASES
the grower must experiment under his own conditions before
applying this method generally, else the chemical injury by
the acid to the seedlings may be greater than the losses due to
damping-off if no treatment were used. If this method can
be handled without damaging the seedlings, two special ad-
vantages are gained over the other two methods given above.
In the first place, dicotyledonous weeds rarely grow in the acid
soil and the saving of the expense of weeding will often pay for
the treatment. Secondly, the disinfectant is present in the soil
throughout the critical damping-off period. This assures
complete control since contamination of the beds from neigh-
boring soil is not possible and, moreover, conditions of tempera-
ture and moisture favorable to seedling growth can be provided
without danger.
The average amount of sulfuric acid is three-sixteenths of a
fluid ounce of clear commercial sulfuric acid to each square
foot of soil to be treated. A solution is made by adding three-
sixteenths of an ounce of the sulfuric acid to each quart of water
(this is at the rate of one part of acid to 170 parts of water).
This solution should then be applied when the seed is sown
at the rate of one quart to each square foot of soil. If the soil
is light and sandy and conditions are favorable for excessive
evaporation, light watering once or twice a day may be neces-
sary to prevent acid-injury. In heavier soils no watering
may be necessary. The strength recommended above is suffi-
cient to disinfect a soil which is not strongly alkaline. If the
soil is naturally acid, the three-sixteenths of an ounce to each
square foot may be too much. It would, therefore, be advisable
to divide a given bed into three parts, applying sulfuric acid to
each part respectively in the following quantities, one-eighth,
one-fourth and three-sixteenths of an ounce in a quart of water
to each square foot. From this experiment it may be deter-
mined which strength can be safely employed under the exist-
ing soil conditions.
SEEDLING DISEASES AND INJURIES 9
REFERENCES ON Dampinc-OFFr
Hartley, Carl, and Pierce, R. G. The control of damping-off of conif-
erous seedlings. U.S. Dept. Agr. Bul. 453: 1-32, pls. 1-2, fig. 1
1917.
Johnson, James. The control of damping-off disease in plant beds.
Wisconsin Agr. Exp. Sta. Research Bul. 31: 29-61, figs. 1-12.
1914.
Gifford, C. M. The damping off of coniferous seedlings. Vermont
Agr. Exp. Sta. Bul. 157: 1438-171, pls. 1-4, figs. 1-10. 1911.
Jones, L. R. The damping off of coniferous seedlings. Vermont Agr.
Exp. Sta. Ann. Rept. 20: 342-347. 1908.
Hartley, Carl. Injury by disinfectants to seeds and roots in sandy
soils. U.S. Dept. Agr. Bul. 169: 1-35, pl. 1, figs. 1-2. 1915.
Spaulding, Perley. The damping-off of coniferous ewes Phyto-
pathology 4: 73-88, pl. 6, figs. 1-2. 1914.
Hartley, Carl, and Merrill, F. C. Preliminary tests of disinfectants
in controlling damping-off in various nursery soils. Phyto-
pathology 4: 89-92. 1914.
Pettis, C. R. Problems in nursery practice. Proc. Soe. Amer. Fores-
ters 4: 43-44. 1909.
Seott, Chas. A.
4
6
oxidation products which
stain the mycelium and
cell-walls of the wood.
The mycelium of wood-
rotting fungi uses the
dissolved wood-tissue as
food material. After a
considerable amount. of
this food is obtained and
stored, the production of
the fruiting-bodies be-
gins. For this purpose
a tissue-like development
of closely tangled my-
celium, in the shape of
ms a knob, usually forms at
ae the original point of in-
Fra. 5.— Under surface of a polypore, show- fection. The food ma-
ae Sper Gade of Beer eG ate tubes. En- terials from all directions
arged (several times).
are transported to this
point and the fruiting-body develops an upper sterile surface and
a fertile suspended layer of spore-bearing tissue on the under
surface. In the case of the toadstools the spores are borne on
the sides of pendent plates or gills (Fig. 8, page 81), and in
the bracket-fungi or polypores, they are borne on the inner sur-
face of perpendicular tubes which are open at the lower end
and are visible to the naked eye as small holes in the lower
surface of the fruiting-body (Fig. 5). Besides the character-
istic action of the mycelium of the different species of fungi
t
BODY AND BRANCH DISEASES AND INJURIES 69
causing the wood-rots, the characters of the fruiting-bodies
serve to identify the causal fungus, if they are definitely as-
sociated with the rot. The correct determination of the dif-
ferent species of bracket-fungi is, however, not easy in some
cases. The number of species of annual forms represented in
the United States is greater than that of the perennial forms.
A generic distinction between the annual and perennial forms
is recognized and they have been named respectively Po-
lyporus (po-lip’-pore-us) and Fomes (fo-meez). Other genera
have been split off from these two, which probably represent
a more natural classification. Since, however, the simpler
and more artificial classification is still used by laymen and
most scientists, the genera Polyporus and Fomes are used in
the discussion of the wood-rot fungi in this book. For a
synonymy of polypore names, see the appendix, page 364.
The species of Polyporus usually produce a more or less fleshy
or corky fruiting-body which is soon destroyed by insects or
decay and rarely functions in producing spores for more than
the single season. The species of Fomes, on the other hand,
form hard, woody structures which develop a new layer of
tubes on the under surface each year as long as food material
is being obtained by the mycelium, in its advance into normal
wood. In this manner the size of the fruiting-body increases
yearly and its age may be determined by counting the layers
of tubes when the fruiting-body is split perpendicularly.
Dissemination of the spores.
The spores of the bracket-fungi are borne in groups of four,
each on a tiny spine, at the ends of branches of the mycelium
which project from the inner sides of the tubes. * When mature,
these spores are shot from their attachment with just enough
force to bring them to the center of the tube, and then they
drop_out of the open end at the bottom. The wind, or even the
slightest breeze, serves to carry the spores for long distances,
70 MANUAL OF TREE DISEASES
since they are very light and buoyant. Millions of spores are
disseminated from a single fruiting-body during a few days
after they become mature. They are somewhat sticky and
adhere to any object with which they come in contact. The
larger part of them never reach suitable places where infection
may be accomplished. However, a sufficiently large number
is produced that a few usually find lodgment where infection
is possible. Wounds such as the splintered ends of the branch-
stubs which hold moisture readily are most likely to become
infected. The spores are very short-lived and suitable con-
ditions of moisture must be encountered in order to have ger-
mination take place. The germ-tube of the spore produces short
branches of mycelium which immediately begin the decay of
the wood at the point of infection, and as soon as a firm foot-
hold is gained, a copious growth of the mycelium occurs, which
spreads rapidly.
Control of wood-rots.
Wood-rot diseases are more abundant and destructive in
the forest than in individual trees grown for shade or ornament.
Conditions in the forest are ideal for the development of these
fungi. All sorts of wounds are available for infection and thus
dissemination and germination of the spores is more efficient
in causing a higher percentage of infection. Another factor
which makes wood-rots more serious in the forest is that great
quantities of fallen trunks and branches are present on which
fruiting-bodies of most of the wood-rot fungi continue to be
produced in great abundance. Outside the forest, the absence
of these conditions makes infection less common. A few of
the wood-rots, however, are important diseases of shade-trees.
In controlling these rots, tree surgery methods are effective
if the wood-rot is not too far advanced and if the expense is
considered justified by the value of the tree. The methods
for eliminating heartwood- and sapwood-rots are discussed under
BODY AND BRANCH DISEASES AND INJURIES ‘771
tree surgery, page 345. The necessary care in pruning to leave
a wound which will heal most rapidly and protecting the wound
in the meantime by the use of wound-dressings are important
measures for reducing wood-rots to a minimum. These opera-
tions aré also more fully discussed under tree surgery methods.
The immediate destruction of newly developing fruiting-bodies
of all kinds in the vicinity of trees to be protected will reduce
greatly the amount of infection.
In the forest, the factors concerned in the complex of soil,
atmospheric and biologic relations, influence greatly the yield
and quality of timber that is realized. Methods of forest
management in this country have seldom taken into consid-
eration many of these vital factors, one of the most important
of which is the control of the wood-rotting fungi of living trees.
The subject of forest pathology is too complex to be adequately
dealt with in a small space and is outside the field of this book.
A simple method of disease control in the forest is the elimina-
tion of all diseased trees at the time cutting operations are
in progress. For some types of forests and systems of selec-
tion for cutting, this procedure is not economically possible.
Thus it will be possible to control the loss factor due to decay
only when all the complex relations existing. in the forest have
been studied for different types and localities. Before control
measures can be incorporated into scientific forest regulation,
such points as the following must be determined: the relations
which determine the rate of growth and general health of the
trees, the extent, nature and cause of wounds, the life history
of the wood-rotting fungi, the relative susceptibility of different
species and different age classes, and many other relative factors.
REFERENCES
Schrenk, Hermannvon. Fungous diseases of forest trees. U.S. Dept.
Agr. Yearbook 1900: 199-210, pls. 21-25. 1901.
Meinecke, E. P. Forest pathology in forest regulation. U.S. Dept.
Agr. Bul. 275: 1-62. 1916.
CHAPTER IV
ROOT DISEASES AND INJURIES
Tue roots serve both for anchorage and for gathering from
the soil the water and dissolved raw materials needed by the
tree in its growth. The structure of certain types of soil,
and the food materials contained, often determine the kinds
of trees which will grow best in it. However, it is not the
intention to discuss here the adaptability of different species to
soil-types or of the poor growth or injuries resulting from a
lack of such adaptability. Although a tree may be growing in
suitable soil and obtaining from it the proper materials for
normal growth, there are other factors which often inter-
vene to cause injuries to the root system. Any such injuries
to the roots of the tree may impair certain functions or destroy
living tissues and cause various symptoms of disease to appear
in the aérial portions of the tree.
In diagnosing tree troubles, the possibility of root diseases
should be considered and care should be taken to ascertain
whether or not the condition of the roots may be the primary
cause of the difficulty. Impairment of the root functions may
be due to such conditions as : too much water in the soil, causing
drowning; too little water because of sod, pavements, or packed
soil above the roots; poisonous gases or over-abundance of
certain food materials applied to the roots with fertilizers; and
the attacks of certain parasitic fungi and bacteria which invade
and kill living tissue. These various injurious factors work
more or less slowly, and the usual symptoms noticed in the parts
above ground are: slow growth, thin foliage, sun-scorch of the
72
ROOT DISEASES AND INJURIES is
leaves, early fall of leaves in autumn, death of certain entire
branches, stag-head, and lichens on the bark. When such
general symptoms of decline occur without apparent associa-
tion with a cause in the branches, leaves or atmospheric con-
ditions, the presence of a root trouble may be suspected.
DRYING AND DROWNING
Caused by too little and too much water in the soil
Trees must obtain at all times enormous quantities of water
from the soil, during the period when the leaves are expanded.
With a normal water supply and a healthy root system, a tree
is naturally so balanced in its development of roots and leaf-
surface, that it is able to supply the water lost in transpiration
from the leaves, except under the most abnormal atmospheric
conditions. But if the supply of water is limited because the
natural rainfall does not soak into the soil, the leaves may tran-
spire more water than the roots can take up ina given length of
time. This condition will cause sun-scorch of the leaves and
if repeated year after year may cause the death of the tree (see
page 22).
The other extreme of too much water in the soil may result
in more speedy death of the tree. The tips of the roots, which
are in contact with the soil-particles and absorb water and food
materials, must at the same time obtain a ready supply of air
to make healthy growth and perform their function of absorp-
tion. The older parts of the roots must also have access to a
supply of air in order that the living tissues they contain may
function in growth and transporting food materials and water
to the parts above ground. If the amount of water in the soil
is excessive, it drives out the air, thus disturbing the balance of
air and water necessary to plant growth. This results in slow
or rapid death of the roots by drowning. The leaves may show
sun-scorch injury the same as when too little water is present.
74 MANUAL OF TREE DISEASES
This may seem peculiar, since there is an over-abundance of
water in the soil, but it is explained by the fact that the trans-
porting of the water to the trunk is dependent on the healthy
condition of the roots and when these are injured, the power
to absorb water is diminished accordingly. Therefore, al-
though there is plenty of water in the soil, it cannot be supplied
to the leaves.
The remedy for such conditions of abnormal water supply
may be undertaken after the symptoms are noted, if the re-
covery of the tree seems possible. When heavy sod, tight
paving or compact soil is the cause of too little of the normal
rainfall reaching the roots, artificial means must be used for
watering. The best method is to keep the sod broken up, but
when this is not desirable, upright sections of tile may be
placed at intervals flush with the sod and the necessary water
furnished by running water into these from a hose. It should
be remembered that the feeding rootlets are under the edges
of the branches and not up close to the trunk of the tree.
The tile should, therefore, be placed at intervals in a circle
under the tips of the branches. A certain amount of artificial
fertilizing may also be accomplished through the tiles. When
the soil contains too much water, the ordinary methods of
drainage should be employed.
REFERENCE
Graves, A. H. Root rot of coniferous seedlings. Phytopathology 5:
213-217, figs. 1-2. 1915.
FREEZING-TO-DEATH
Caused by low temperatures
Many kinds of trees are more or less injured by the freezing
of the roots. White pine, maple, elm and ash are particularly
susceptible.
ROOT DISEASES AND INJURIES 19
Symptoms.
The symptoms of freezing-to-death in the roots, as noticed
in the aérial parts, are general, although somewhat distinctive
and diagnostic. The primary symptoms can easily be deter-
mined by examining the roots themselves. Tissue which has
suffered from freezing-to-death gives no external evidence of
its condition until some time after it has thawed. Then it ap-
pears, at first, water-soaked and later, after some disintegration
processes have set in, it becomes brown. Tissue thus killed is
soon invaded by the numerous saprophytic organisms in the
soil and is further disintegrated.
Severe injury to the entire root system results in the death of
the tree before summer. The leaves may come out, but re-
main small and misshapen. Less severe and re-occurring in-
jury to the roots may result in a varying succession of symptoms.
One of the most common effects is that of sun-scorch of the
leaves, and is most common in the pine and maple (see page 22).
The inability of the remaining healthy roots to provide enough
water for the leaves to equal the amount transpired on hot days
results in the wilting and death of the leaves. The entire tree
suffers then, since the diminution of the leaf-surface makes im-
possible the manufacture of enough food materials for normal
growth. Another symptom of root-injury is the production
of thin foliage at the top, in excurrent trees, and stag-head may
be the cumulative effect of this condition.
Cause of freezing-to-death.
In the process of maturing the new tissue formed during the
summer, the roots are the last part of the tree to attain the con-
dition necessary to withstand low temperatures without injury.
A combination of-a late warm autumn followed by deep freez-
ing of the ground may lead to serious root damage. Thus, it
happens that winter-injury to the roots 1s exceptionally common
some winters and rare in others when the temperature falls to
76 MANUAL OF TREE DISEASES
even a lower point. The injury caused to the roots is the type
known as freezing-to-death (see page 12). The water in the
cells is withdrawn during the formation of ice crystals between
the cells. As the temperature becomes lower, the physical pull
incident to ice formation causes a larger amount of water to be
withdrawn from the living cells than they can endure without
being killed. Since the root system of most kinds of trees may
extend from a few inches to several feet below the surface, it is
natural that shallow-rooted trees will show the first and most
serious injury provided the minimum temperature for the roots
of that species is reached. Also, the amount of damage to the
root system of a given tree depends on whether its roots are
largely superficial or are found at varying depths.
Control.
Winter-injured roots should be uncovered and the dead parts
pruned off. The wounds should be treated with a wound-
dressing, and the soil conditions around the tree made con-
ducive to the rapid regeneration of new roots by fertilizing.
Mulching may be practiced to protect the soil around sus-
ceptible trees from freezing deeply.
REFERENCE
Stone, G. E. Winter injuries of roots. Jn Shade trees, character-
istics, adaptation, diseases and care. Massachusetts Agr. Exp.
Sta. Bul. 170: 200-204. 1916.
Gas-INJURY
Caused by illuminating gas
Trees are commonly injured by the poisonous effect of illumi-
nating gas on the roots, when leaks in gas-pipes are not promptly
repaired. The effect is usually cumulative and the tree may
show no sign of the injury until some time has elapsed.
ROOT DISEASES AND INJURIES C0
Symptoms.
The symptoms are general in nature, being about the same
as those produced when any agency causes a gradual death of
the root system. Partial freezing-to-death of the roots and
cumulative gas-injury cause similar symptoms. The turning
yellow or brown of the foliage is a common symptom, probably
due entirely to the interference with the conduction of the
necessary supply of water. Later, the living tissues m the root
and trunk will be found dry and turning brown, showing that
the lack of water and the poisonous properties of the gas com-
bined have killed the tissues. At this stage various branches
die and saprophytic fungi attack the dead bark. The length
of time which it takes for a tree to die from gas-poisoning de-
pends entirely on the amount of gas in the soil. Even a
small quantity of gas present continuously will produce serious
injury within two or three years. Conifers are much more
resistant to gas than deciduous trees. At times, the former
recover after the injury becomes apparent, while deciduous
trees which begin to develop the symptoms of poisoning rarely
recover, even if the leak is repaired.
Cause.
The injury to the roots caused by illuminating gas is probably
of two kinds: first, true asphyxiation, since the air necessary to
the roots is replaced by the gas; and second, the living tissues
are poisoned. Many toxic substances are contained in the dif-
ferent kinds of illuminating gases. These substances when
dissolved in the soil-water are absorbed into the root and the
cumulative effect is shown in the death of the cells.
Control.
The remedy for gas-injury is to stop the leakage and stir the
soil until all the gas has escaped. If only a portion of the root
system and trunk is killed, the tree may be saved by the use of
- surgical methods to remove the dead tissue (see page 345).
78 MANUAL OF TREE DISEASES
REFERENCES ON Gas-INJURY
Stone, G. E. Effects of illuminating gas on trees. Jn Shade trees,
characteristics, adaptation, diseases and care. Massachusetts
Agr. Exp. Sta. Bul. 170: 220-228, figs. 938-97. 1916.
Stone, G. E. Effects of illuminating gas on vegetation. Massa-
chusetts Agr. Exp. Sta. Ann. Rept. 25:1: 45-60, figs. 1-8. 1913.
SHOE-StRING Root-Rot
Caused by Armillaria mellea (Fries) Quelet
The shoe-string or honey-mushroom root-rot is common
throughout the United States on many kinds of coniferous and
deciduous trees. It has been noted especially on oak, pine,
chestnut, larch, sycamore, poplar, locust, hemlock, birch, alder,
maple and many kinds of fruit-trees and shrubs. In some
sections of the country, especially in south central United States
and on the Pacific Coast, orchard-trees are commonly affected
and killed. The disease is most destructive in orchards on
land recently cleared of oak. In Europe this disease is also
common on cedar, pine, fir, peach, cherry, olive, grape and
many other kinds of woody plants. There seem to be no.
definite host relations for the activities of the fungus causing
this root-rot. It is known to attack the potato.
No very accurate facts are available as to the parasitic po-
tentialities of the honey-mushroom. It occurs everywhere .on
stumps and dead wood and is commonly found on trees in poor
health or badly wounded. The relation between the decline of
the tree and the attack of this fungus is hard to determine.
However, abundant evidence is at hand that young thrifty
trees in the forest and orchard are often killed, when there is
no doubt that the honey-mushroom was directly and primarily
the cause of the decay of the roots. It is, therefore, reasonable
to expect that on further investigation this root-rot will be
fully shown to be a primary cause of the decline and death of
the trees. In many cases, however, it may play only a sec-
»
signs of decline to final death
mycelium of the causal fungus
ROOT DISEASES AND INJURIES 79
ondary part. The fungus is so prevalent as a saprophyte that
its occurrence as a wound parasite and root-rotting fungus on
trees 1s not surprising.
Symptoms.
The bark and wood of the roots are affected and the living
tissues destroyed. The decay may also extend up into the
bark and sapwood of the lower
part cf the trunk (Fig. 6).
Trees with the root system
partially destroyed display
general symptoms of decline
and poor health, such as dead
limbs, scanty and light green
foliage, and but little annual
growth. In conifers a large
amount of resin exudes from
the base of the tree and ac-
cumulates as a hard cake (Fig.
6). The time from the first
may extend over a period of
three or four or more years.
There are many diagnostic
symptoms by which this root-
rot may be identified. The
when growing in the soil out-
side the roots is bound to-
gether in long round, blaek Fie. 6.— White pine killed by shoe-
= string root-rot.
strands somewhat resembling
shoe-strings. These black strands may be found growing
attached to the bark of the roots and trunk or running
through the soil for long distances away from the affected
80 MANUAL OF TREE DISEASES
roots (Fig. 6). The strands may be traced to points at which
they enter the roots. At these points the white mycelium in-
side the black strands spreads out and runs in all directions in
the bark and sapwood. Thin white sheets of mycelium are
found in the cambium region (Fig. 6). The tissues of the
cambium and bark are destroyed and replaced by the white
sheets. The mycelium also penetrates the medullary-rays and
sapwood and causes a wet white rot. After the bark is killed,
the black shoe-strings are formed abundantly between the
bark and wood. ‘They anastomose in all directions and form
a network. The decayed
area of sapwood and bark
is bordered by a_ brown
zone.
The fruiting-bodies of the
fungus are honey-colored
toadstools or mushrooms.
They appear on the sides of
the trunk, exposed roots or
directly from the ground. _
Close examination will show
their attachment to the
Fic. 7.— Young toadstools of Armillaria 2 5
mellea attached to shoe-strings. black shoe-strings (Fig. a:
The toadstools occur in ~
clusters, attached to one another at the base of the stalks. -
The stalks are somewhat swollen at the base and have a fragile
collar just beneath the cap. The upper surface of the cap
is smooth and yellowish or brownish. The under surface is
composed of radiating pendent plates or gills of the same
color (Fig. 8).
Cause.
The shoe-string root-rot of trees is caused by the mushroom,
Armillaria mellea. The spores are borne on the sides of the
ROOT DISEASES AND INJURIES 81
gills or plates on the under surface of the fruiting-body (Fig. 8).
The tree-roots are infected in several ways. The spores may
cause infection through wounds at the base of the tree or in ex-
posed roots. The black strands running through the soil may
also penetrate the
bark of the roots.
In this manner the
fungus spreads
through the — soil
from the roots of
one tree to another.
This mode of infec-
tion accounts for
the occurrence of
circular areas of dis-
eased trees. Since
the fungus also com-
monly occurs as a
saprophyte on dead
wood, the fruiting-
bodies are produced
in great abundance
on prostrate trunks
and on old stumps
for ‘several years
after the affected Fic. 8.— Mature fruiting-body of Armillaria mellea,
tree is dead. showing gills on under surface.
Control.
Root diseases are difficult to control since the condition of the
roots cannot be readily ascertained. By destroying the toad-
stools and removing the diseased roots or parts of roots, the
individual tree may be saved. In the orchard or forest, dis-
~ eased trees or groups of trees may be surrounded by isolation
G
82 MANUAL OF TREE DISEASES
trenches, a foot or two deep. All roots bridging the trench
must be removed and the trench kept free of débris and fruit-
ing-bodies. The trench must be dug far enough away from
the affected trees to insure the absence of diseased roots out-
side of the area to be isolated. — +
REFERENCES
Long, W. H. The death of chestnuts and oaks due to Armillaria
mellea. U.S. Dept. Agr. Bul. 89: 1-9, pls. 1-2. 1914.
Schrenk, Hermann von, and Spaulding, P. . Root-rots. Jn Diseases
of deciduous forest trees. U.S. Dept. Agr. Bur. Pl. Ind. Bul.
149: 22-24, 1909.
Hesler, L. R., and Whetzel, H. H. Armillaria root-rot. Jn Manual
of fruit diseases, pp. 96-102, figs. 26-27. 1917.
Hartig, R. Agaricus melleus L. Jn Die Zersetzungserscheinungen
des Holzes ete., pp. 59-62, pl. 11. 1878.
Hartig, R. Agaricus (Armillaria) melleus Le In Wiechtige Krank-
heiten der Waldbaume, pp. 12-42, pls. 1-2. 1874.
Lawrence, W. H. Root diseases caused by eats mellea in rie
Puget Sound country. Washington Agr. Exp. Sta. Bul. (special
series) 3: 1-16, figs. 1-5. 1910.
Piper, C. V., and Fletcher, S. W. Root diseases of fruit and other
trees caused by toadstools. Washington Agr. Exp. Sta. Bul.
59: 1-14, figs. 1-5. 1903.
Horne, W. T. The oak fungus disease of fruit trees. California State
Com. Hort. Monthly Bul. 3: 275-282, figs. 79-81. 1914.
Horne, W. T. Fungous root rot. California State Com. Hort.
Monthly Bul. 1: 216-225, figs. 85-91. 1912.
Horne, W. T. Oak fungus or Armillaria mellea in connection with
nursery stock. California State Com. Hort. Monthly Bul. 4:
179-184, figs. 31-33. 1915.
Barss, H. P. Mushroom root rot of trees and small fruits. First
Biennial Crop Pest and Horticultural Report (Oregon Agr. Exp.
Sta.) 1911-1912 : 226-233, figs. 23-38. 1913.
Mycoruizas
Caused by various species of fungi
An interesting type of parasitic relation between certain
species of fungi and the living roots of many kinds of trees con-
ROOT DISEASES AND INJURIES 83
sists in the development of mycorhizas. These structures
probably in no manner interfere sufficiently with the growth of
the roots to cause any damage. ‘Trees with mycorhizas on the
roots cannot be distinguished from those without by any above-
ground symptoms. A short account of them is, however, of
interest since the structures are now generally considered to
represent a diseased condition of the roots and not a true type
of symbiosis or mutual-advantage relation, as was previously
believed by many.
The term mycorhiza is used to signify the infected root and
the mycelium of the fungus, as an association of two distinct
but physiologically interdependent tissues. This usage is thus
similar to the use of the term lichen, the formation of which
requires the association of certain algze and fungi to form the
characteristic structures known as lichens. Mycorhizas are
of two types: ectotrophic, when the mycelium forms a mantle
or sheath around the root-tip and penetrates the tissues by inter-
cellular (existing between the cells) threads of the mycelium ;
and endotrophic, when the mycelium is within the tissue and is
largely intracellular (within the cells). Recent investigations
have shown that hickory, oak, basswood, birch, larch, poplar
and beech commonly show ectotrophic mycorhizas, and species
of maple, butternut and horse-chestnut have endotrophic forms.
Elm and species of willows were found not to have mycorhizas.
This list is by no means complete, but represents the species
reported in the reference given below. With the exception of
this work, little is reported in American literature on mycorhi-
zas. European literature on the subject, however, is abundant.
Both types of mycorhizas are annual. The mycelium of the
species of fungi capable of forming mycorhizas penetrates the
young root-tips in the summer. The association with the root-
tissues is rapidly formed and food materials are obtained by the
fungus. Later, the fungus may produce a growth of mycelium
in the soil in the autumn, in which case fruiting-bodies are
84 MANUAL OF TREE DISEASES
formed on the surface of the ground. Several kinds of toad-
stools and puff-ball fungi have been proved to be mycorhizal
fungi. Ectotrophic mycorhizas are recognized by the short,
stubby, lateral rootlets, which are covered with the fungus
mantle and may be white, brown, yellow or red. The same
tree may show several different kinds of mycorhizas, each caused -
by a different species of fungus. When the mycorhizal pro-
duction is profuse, whole clusters of the stubby roots may form
a coral-like structure. The endotrophic mycorhizas on maple
roots form bead-like swellings, often in chains. The mycelia
of some endotrophic mycorhizas have been found to produce
fruiting-bodies, which place them in the genus Phoma.
REFERENCE
McDougall, W. B. On the mycorhizas of forest trees.. Amer. Jour.
Bot. 1: 51-74, pls. 4-7, fig. 1. 1914. (Bibliography given.)
Roots PARASITIZED BY FLOWERING PLANTS
Several species of flowering plants attach their root-like
organs to the roots of other plants and trees, and draw a certain
amount of food materials from them. All degrees of para-
sitism are found, from the species of the broom-rape family
(Orobanchaceee) which develop no leaves or chlorophyl and
are entirely dependent on other plants for food, to those types
which develop normal green foliage above ground, and some-
times grow without forming any attachments to the roots of
other plants. Certain species of Comandra have been found
to be of the latter type. Their roots normally develop disc-
like attachments, which connect the tissues of the Comandra
roots with the roots of various other plants. They have been
found attached to the roots of the following trees: maple,
birch, chestnut, poplar, oak and sumac. Very little damage is
done to the tree. Examples of the former type, mentioned
ROOT DISEASES AND INJURIES 85
above, where all the food materials required by the plant are
obtained through the connected roots, include the common
beech-drop (see page 108), indian-pipe and many other plants
belonging to various families of the flowering plants.
REFERENCES
Hedgecock, G. G. Parasitism of Comandra umbellata. Jour. Agr.
Res. 5: 133-135. 1915.
Harshberger, J. W. Vegetal agents of disease. Jn A text-book of
mycology and plant pathology, pp. 298-306, figs. 117-123. 1917.
CHAPTER V
ALDER DISEASES
SEVERAL native species of alder (Alnus) are common forest-
trees in the Northwest and Rocky Mountain region. They
grow in river-bottom lands and on mountain sides. In eastern
United States, the European alder is used as an ornamental and
in some localities has become naturalized.
The alder is particularly subject to wood-rot diseases. The
common white and the brown checked wood-rots often cause
death by destroying the sapwood. The leaf-blisters, deforma-
tion of the catkins and catkin powdery mildew attract attention
when they occur, but they do only slight damage to the tree.
The alder also is one of the non-leguminous plants on which
the nitrogen-fixing bacteria form root-tubercles. The several
shrubby species of alder are subject to the same diseases as the
larger trees.
PowpERY MILDEW oF CATKINS
Caused by Erysiphe aggregata (Peck) Farlow
In northeastern United States, the female catkins of alder are
often covered with a powdery mildew. A similar, if not identi-
cal, fungus attacks the twigs of alder in Europe. The catkins
are covered with a white or yellowish coating of mycelium which
later may be dotted with clusters of small black fruiting-bodies.
The life history and methods of control of the powdery mildew
fungi are discussed on page 37. Two other species of the pow-
dery mildews occur on alder leaves.
86
ALDER DISEASES 87
CaTKIN-DEFORMATION
Caused, by Hxoascus amentorum Sadebeck
The catkins of several species of alder are affected by this
disease. ‘The same disease is common in Europe. The scales
of the fertile catkins become much enlarged and project as
curled, reddish tongues. Later they are covered by a white
glistening coat of the fruiting structures of the parasite. The
mycelium is perennial in the twigs. Practically no damage is
done to the tree. If preventive measures are desired, the prun-
ing of the diseased parts should eventually eliminate the
difficulty.
Brown CHECKED Woop-Rot
Caused by Polyporus sulphureus Fries
The alder is one of the many deciduous trees commonly af-
fected by the brown checked wood-rot. Chief among the other
kinds affected are oak, chestnut, walnut, butternut, maple and
locust. The causal fungus enters through some wound where
the heartwood is exposed. The heartwood and sapwood are
both decayed and become like red-brown charcoal. Thin
yellowish sheets of mycelium, within concentric and radial
checks, divide the decayed wood into small punky cubes. The
fruiting-bodies emerge, usually, from old branch wounds and
consist of many overlapping shelves forming a large, more or
less globose mass. The upper surfaces of the shelves are orange-
red, while the under surfaces are sulfur-yellow. For further de-
tails concerning this wood-rot see under oak diseases, page 247.
Common Wurte Woop-Rot
Caused by Fomes igniarius Fries
Alders are destructively affected in Europe by the common
. white wood-rot. In the United States such trees as beech,
88 MANUAL OF TREE DISEASES
poplar, willow, maple, butternut, walnut, oak and hickory are
the most commonly affected by this wood-rot. Specific men-
tion of this disease in alder is less frequent in this country be-
cause of the slight economic importance of the species of alder.
For a description of the symptoms of the common white wood-
rot, see under poplar diseases, page 305.
Root-TUBERCLES
Caused by Bacillus radicicola Beijerineck
The roots of alder commonly show large clusters of short
stubby roots. These abnormal roots represent a diseased con-
dition by which the alder benefits. The dwarfed roots are in-
habited by the same bacterium which causes the root-tubercles
of clover, bean, cowpea, locust and other leguminous plants.
The bacteria gain entrance to the young lateral rootlets by way
of the root-hairs. They multiply within the cells of the cortex
of the root and stimulate this tissue to over-growth. They
live parasitically and obtain their food materials from the proto-
plasm and cell sap of the alder roots, but they do not kil! the
cells they inhabit. These bacteria take the free nitrogen gas
from the air and combine it with other substances. After this
is accomplished, the alder roots eventually receive this combined
nitrogen and the tree uses it in its metabolic processes. In this
way large quantities of nitrogen are obtained indirectly from
the air by the alder. The higher plants cannot utilize nitrogen
gas from the air and the plants which are parasitized by the
nitrogen-fixing bacteria are thus greatly benefited. Such a
mutual-benefit relation between the alder and the bacteria is
known as symbiosis, although strictly speaking the bacteria are
parasitic even though they do not cause the death of the root-
tissues.
REFERENCE
Spratt, Ethel R. The morphology of the root tubercles of Alnus and
Elwagnus, and the polymorphism of the organism causing their
formation. Ann. Bot. 26: 119-128, pls. 138-14. 1912.
CHAPTER Vi
ARBOR-VITZ DISEASES
Two species of arbor-vitee (Thuja) are common forest-trees
in northeastern and northwestern United States. They occur
in moist river-bottom lands and along mountain streams. The
western arbor-vite grows to a much larger tree than the eastern
species. Both species are extensively used as ornamentals.
The eastern arbor-vite is especially free from diseases.
The wood and roots of the living tree are seldom decayed
and no leaf or twig-diseases of any importance are known.
The western arbor-vite, on the other hand, is destructively
attacked by a leaf-fungus. The younger trees may be killed
outright. In the nursery, arbor-vite is subject to a common
blight which also affects juniper. Ornamental arbor-vite
seldom suffer from fungous diseases but frequently are injured
by freezing-to-death, sun-scorch and other general troubles
(see index).
SEEDLING-BLIGHT
Caused by Phoma sp.
At least three species of Thuja, including the eastern and
western arbor-vite, are affected by this seedling-blight. The
same disease is common on juniper. Young arbor-vite trees
up to four years old are affected in the same manner as juniper
(see page 190). Cankers are formed which girdle the stem,
causing the plants to die. The disease often becomes epiphy-
totic and causes serious losses in nursery-beds. Control
measures have not been determined.
89
90 MANUAL OF TREE DISEASES
Lear-BiicHt
Caused by Keithia thujina Durand
The leaf-blight or black leaf-spot of western arbor-vite is
common and destructive, especially to young trees, throughout
its range in northwestern United States. In dense stands
and in localities where humid conditions prevail, this disease
causes the death of a large percentage of the seedlings less than
four years old. In late summer the lower branches of older
trees when affected by this blight appear as if scorched by fire.
In some localities the foliage of the upper parts of the trees
also may be affected. This is, however, essentially a disease
of seedlings. The affected parts are those which are covered
by snow until late in the season.
Symptoms.
In spring and summer the affected leaves show from one to
three more or less circular brown cushions bursting through the
epidermis. Later these bodies turn black. The affected leaves
die and turn brown in late summer. The twigs bearing the
brown leaves also fall, leaving the branches bare. In autumn
the black bodies in the older leaves often fall out, leaving holes,
and these leaves turn gray.
Cause.
The leaf-blight or black leaf-spot of the western arbor-vite
is caused by the fungus Keithia thujina. This fungus is closely
related to the tar leaf-spot fungi of maple and willow and the
black-specked leaf-spot fungus of maple. The black fruiting
bodies on the leaves crack open, irregularly, and expose the
ascospore-bearing surface within. The ascospores are wind-
blown and infection usually occurs in the autumn. Moist
weather is necessary for the discharge of the spores.
ARBOR-VITHA DISEASES 91
Control.
Preliminary experiments seem to indicate that soap-bordeaux
mixture applied to young trees, every ten days or oftener in
the autumn, will greatly reduce the amount of infection.
REFERENCES
Weir, J. R. Keithia thujina, the cause of a serious leaf disease of the
western red cedar. Phytopathology 6: 360-363, figs. 1-2. 1916.
Durand, E. J. The genus Keithia. Mycologia 5:6-11, pl. 81.
1913.
Brown Pocket HEARTWoop-RotT
Caused by Fomes roseus Fries
There are few statements in literature concerning the fungi
which cause the decay of the wood and roots of arbor-vite.
Mention is made of brown pockets of decay in wood of the trunk
which are probably due to Fomes roseus. This fungus causes
a heartwood-rot of fir, juniper, larch, spruce, pine, and hemlock.
The fruiting-bodies have been found also on a few deciduous
trees. The decay caused by this fungus is described under
juniper diseases (page 204). The color of the decayed wood
varies from dark to a lighter brown according to whether the
normal wood is deeply colored or not. In some cases the
similarity between the effects of Fomes roseus and Polyporus
Schweinitzii may lead to confusion as to which is the true cause
of the rot, unless the sporophores are found attached to the
tree in question.
Rep-Brown Root- ano Butrt-Ror
Caused by Polyporus Schweinitzii Fries
This is one of the few wood-rots of conifers which occurs
in arbor-vite. Pine, fir, spruce, hemlock and larch are seri-
92 MANUAL OF TREE DISEASES
ously damaged by this root disease throughout their range.
The wood of the affected roots is at first yellowish and cheesy
but later it becomes red-brown and brittle. The rot sometimes
extends up into the trunk. A more complete description of
this disease is given under pine diseases, on page 294.
CHAPTER VII
ASH DISEASES
SEVERAL species of ash (Fraxinus) are common forest-trees
in most parts of the United States. White, green and black
ash are the important timber-trees. These are common
throughout eastern and central United States. The same
three species mentioned above are frequently used for shade
and ornament.
Ash is exceptionally free from destructive diseases. The
rust of the leaves occurs sporadically and may assume an
epiphytotic nature. Little damage is caused to the trees,
however, unless defoliation occurs two or three years in suc-
cession. Several parasitic fungi cause leaf-spots on ash (see
page 29). Only one wood-rot is described as important in ash.
This disease is rarely found in the East but is destructive on
the western limits of the white ash. The slow growth which
the ash makes in that region seems to predispose the trees to
this disease. Where the trees grow more rapidly, they are
seldom affected. The roots of ash frequently are killed by
. low temperature (see page 74).
LreaFr- AND Twic-Rust
Caused by Puccinia fraxinata (Link) Arthur
The leaf- and twig-rust of red, green and possibly other
species of ash is striking because of its effect on the leaves and
twigs and its epiphytotic nature. It is common, at least in
eastern and central United States, but varies greatly in abun-
93
94 MANUAL OF TREE DISEASES
dance from year to year. In central Iowa and eastern Nebraska,
this disease was so abundant in 1885 that it was difficult to
find leaves not affected. The next two summers scarcely any
of the rust could be found. In 1888 it was again abundant
in the same region. An epiphytotic of this
disease was reported in 1887 around Washing-
ton, D. C., with very little of the rust in
that region the next year. No recent reports
of such outbreaks have been published.
Symptoms.
This rust causes swellings which are irregu-
lar or more or less globose. They appear on
the petioles of the leaves and on the twigs ~
(Fig. 9). Swollen areas are also formed on
the leaves which are much distorted. Soon
after the swellings are formed they are covered
by numerous blister-like protrusions, which
break open, leaving cup-shaped areas filled
fee Bee with yellowish powder (Fig. 9). This stage
causal fungus on of the rust is called the cluster-cup stage.
oS OREN The yellow powdery material is composed of
the spores (eeciospores) of the fungus. The distortion of the
petioles and leaves, covered with the yellow cluster-cups, make
this disease conspicuous.
Cause.
Ash-rust is caused by Puccinia fraxinata. This fungus
requires two kinds of host plants to complete its life history.
The spores produced in the cluster-cups on the ash do not
reinfect the ash, but must find lodgment on the marsh or
cord-grasses (Spartina) in order to continue their develop-
ment. On the grass plant, spores are produced which infect
the ash the next spring.
ASH DISEASES 95
Control.
The disease will probably not be noticed until the cluster-
cups have broken open and shed their spores. It would then
be of no avail to destroy the diseased parts of the ash, since
the spores have already been distributed. If practicable, ash
trees should not be grown in the vicinity of marshy land where
the Spartina grass-hosts grow. In the absence of the grass-
host, so far as the life history of this rust is known, there is
no chance of infection of the ash.
Wuire Hrartwoop-Ror
Caused by Fomes fraxinophilus Peck
White ash is commonly affected by this heartwood-rot in
parts of Iowa, Missouri, Kansas and Oklahoma, on the wes-
tern limit of growth of this species. The disease is rarely
found in eastern United States. West of the Mississippi
River, where the white ash attains only three-fourths its normal
size, ninety per cent of the trees are often found diseased; a
fact which suggests some correlation between the condition of
the trees in this region and their apparent greater susceptibility.
The slow rate at which wounds heal, however, may be the
predisposing factor which accounts for the greater abundance
of the disease. Trees of all ages and especially those over
seven inches in diameter are affected.
Symptoms.
The rotted area as seen in cross-section of the trunk is very
irregular in outline and often is more extensive on one side of
the tree. The normal wood of the white ash is light yellow.
In the first stages of decay, the wood is stained brownish. Later
the affected wood becomes whitish and is surrounded by a
brown zone where the decay is extending into the normal
wood. The spring-wood of each annual ring becomes
96 MANUAL OF TREE DISEASES
white, while for a time the summer-wood remains brownish.
Shortly, however, the summer-wood becomes whitish and in
the final stages of the decay the wood is soft and crumbly.
The perennial sporophores of the causal fungus are formed
at old branch wounds. They are usually small bracket-shaped
bodies. The upper surface is hard, dark brown or black and
marked by concentric folds. The under surface is velvety,
straw-colored and covered with large circular pores. The
inner structure of the fruiting-body is white or light brown,
according to its age. A new layer of tubes is added to the
lower surface each year.
Cause.
The white heartwood-rot of white ash is caused by Fomes
fraxinophilus. This fungus is rarely found on any other tree.
Living green ash trees have been observed with the fruiting-
bodies on them and it is possible that a rot of similar nature as
that caused in white ash may be found in green and other ashes.
The spores borne within the tubes on the under surface of the
fruiting-body fall out of the pores and are blown about by the
wind. When they find lodgment on exposed heartwood of the
white ash, a new mycelium may be initiated. The initial
stages in the decomposition of the fibers result in a brown
liquid which stains the wood. Later this colored liquid disap-
pears and the mycelium delignifies the cell-walls and dissolves
most of the cellulose. The fungus is not known to occur as a
saprophyte. For further details concerning the life history and
control of the wood-rotting fungi of living trees, see page 64.
REFERENCES
Schrenk, Hermann von. A disease of the white ash caused by Poly-
porus fraxinophilus. U. 8. Dept. Agr. Bur. Pl. Ind. Bul. 32:
1—20, pls. 1-5, fig. 1. 1903.
Schrenk, Hermann von, and Spaulding, P. White heart-rot of ash
caused by Fomes fraxinophilus. Jn Diseases of deciduous forest
trees. U.S. Dept. Agr. Bur. Pl. Ind. Bul. 149: 46-47. 1909.
CHAPTER VIII
BALD CYPRESS DISEASES
Tue bald cypress or Taxodium is an important timber-tree
in southern and southeastern United States. It is frequently
used as anornamental. The pecky heartwood-rot is the only
known disease of any importance which attacks this tree.
Pecky Hrartwoop-Rot
Caused by Fomes geotropus Cooke
The pecky heartwood-rot of bald cypress is a common disease
and is recognized by every one who handles cypress timber.
The disease is also known by the names peggy-, botty- and bot-
cypress and the peck or puck of cypress. Bald cypress trees
throughout their range are more or less affected by this disease.
It seems, however, to be more common and destructive in the
extreme southern states. It has been estimated that one-third
of the cypress timber available is damaged by this wood-rot.
Older trees are most often affected and, in many cases, the tops
of the trees are decayed without damage to the principal timber
portion. The number of trees showing more or less peckiness
has been found to vary from practically 100 per cent of the stand
in Florida and Louisiana to smaller percentages toward the
northern limits of the range of cypress in North Carolina, In-
diana and Missouri. Since the pecky wood has been found to
be practically as durable as the normal unaffected wood, it is
used for rough lumber and as ornamental finishing for rustic
H 97
98 MANUAL OF TREE DISEASES
effects. The general worm-eaten appearance of the pecky
wood leads to the impression that the injury is due to wood-
boring insects.
Symptoms.
The tops of trees one hundred and twenty-five years old or
older are frequently affected. The rot is also found in the butts.
Younger trees are rarely affected by this disease. The first
indications of the rot are localized areas yellowish in color and
about one-fourth inch wide and several inches long. The wood
between the yellowish areas is unchanged. Decomposition of
the wood elements in the yellow areas proceeds until definite
cavities are formed. These cavities are partially filled with a
yellow-brown powder and occasionally white mycelium and
fibrous masses of partially decayed wood are found mixed with
the brown powder. Sometimes the pockets are found entirely
empty. The pockets extend lengthwise with the grain of the
wood and are about one-fourth of an inch wide and four or five
inches long. They are very smooth-walled and nearly cylindri-
cal and blunt ended. Peckiness is usually confined to the upper ~
part of the trunk and older branches. In very old individuals,
the wood at the base of the tree may be affected. The pockets
are not always found at the center of the tree but may be located
on one side or extend around the trunk leaving the center un-
affected. The pockets may be several inches apart and scat-
tered through the cross-section; or densely aggregated in the
older wood or in certain annual rings. The badly affected trees
are not appreciably weakened and are rarely blown over. ‘The
wood between the pockets is slightly darker in color than the
normal wood but it is unchanged structurally. Recently it has
been learned that the hollows sometimes found in the butts or
trunks of cypress seem to be due to the complete destruction
of the wood between the pockets.
The fruiting-bodies of the fungus causing the peckiness are
\
BALD CYPRESS DISEASES 99
rarely found. They also occur on many kinds of deciduous
trees and may be associated with wood-rots in these trees.
The perennial fruiting-bodies are produced on the lower part of
the trunk and are thick, woody, shell-shaped bodies, measuring
from three to six by five to ten inches. The upper surface is
marked with numerous concentric ridges. It is straw-colored
and slightly hairy or smooth. The under surface is rose-colored
at first but becomes darker with age. The pores are small.
The inner substance of the fruiting-body is corky and yellowish
brown.
Cause.
The pecky heartwood-rot of bald cypress is caused by Fomes
geotropus. The spores from the tubes on the under side of the
fruiting-body infect broken branches in the top of the tree.
From these points of entrance, the mycelium grows downward
into the heartwood. The mycelium becomes abundant in cer-
tain centers. At these places the yellow areas appear and finally
the pockets are formed. From the first formed yellow areas,
strands of the mycelium penetrate the normal wood in all direc-
tions without destroying it. At some distance from the original
yellow areas, new centers of luxuriant mycelial growth originate
and pockets are formed. In this way the wood may become
pecky in older trees throughout the entire length of the trunk.
Pecky cypress is peculiar in the fungus usually ceasing its
activity with the formation of the pockets. The cells imme-
diately surrounding the pockets are filled with a brown humus
compound, which is believed to inhibit the further development
of the mycelium. The wood between the pockets is normal and
no further decay takes place when the pecky timber is placed
under the various extreme conditions conducive to decay.
Normal cypress and pecky cypress timbers are equally resist-
ant to decay and are the longest lived of the timbers of this
country. |
100 MANUAL OF TREE DISEASES
For further details concerning the general life history and
control of the wood-rot fungi, see page 64.
REFERENCE
Schrenk, Hermann von. A disease of Taxodium distichum known as
peckiness, also a similar disease of Libocedrus decurrens known
as pin-rot. Missouri Bot. Gard. Ann. Rept. 11: 23-77, pls. 1-6.
1900.
‘
CHAPTER IX
BASSWOOD DISEASES
THE several species of basswood or linden (Tilia) are
common in eastern and central United States. These trees,
as well as several European basswoods, are extensively used as
shade and ornamental trees in the same region.
No serious diseases affect the basswood. Several leaf-spots
and one powdery mildew affect the leaves occasionally. The
sapwood may be destroyed and the trees killed where wood-
peckers damage the bark and allow fungi to enter. In the
South the roots of the basswood are often decayed by a fungus
which is common in heavy soils.
PowpErRY MILDEW
Caused by Uncinula Clintonii Peck
This powdery mildew fungus attacks the leaves of basswood
in northeastern and north central United States. The myce-
lium is visible on both sides of the leaf, causing diffused
powdery white patches. Small black fruiting-bodies which are
just visible to the unaided eye are scattered over the whitish
area. This species, although indistinguishable from other pow-
dery mildew fungi, except by microscopic characters, is so far
the only one reported on basswood leaves. The life histories
and methods of control of powdery mildew fungi are discussed
on page 37.
101
102 MANUAL OF TREE DISEASES
LEAF-SporT
Caused by Cercospora tilie Peck
The leaves of the basswood are often affected by this disease.
Large brown dead areas are formed at the tip or along the mar-
gin of the leaf (Fig. 10). A broad yellowish border surrounds
Fic. 10.— Leaf-spot of basswood.
the spot. The fruiting bodies of the causal pathogene are in-
conspicuous. For the general life history and control of leaf-
spot fungi, see page 30.
‘
BASSWOOD DISEASES 103
WuitrE Sapwoop-Rot
Caused by Collybia velutipes Curtis
This sapwood-rot is occasionally found in basswood, horse-
chestnut and other deciduous trees. The sapwood becomes
soft and decayed, and the decline and death of the tree gradually
results. Injuries in the bark caused by woodpeckers and other
birds are often found to predispose the trees to attack. The
sporophores of the causal fungus emerge in clusters from
wounds in the bark. They are small toadstools, with yellow
or brownish tops and gills. The bases of the stems are coy-
ered with a dark brown velvety growth of hairs. For the gen-
eral life history and control of the wood-rot fungi, see page 64.
REFERENCE
Stewart, F.C. Trunk rot. ?Collybia velutipes Curt. (Horse chest-
nut). In Notes on New York plant diseases, 1. New York Agr.
Exp. Sta. Bul. 328: 361. 1910.
SOUTHERN Root-Rot
Caused by Ozonium sp.
A great variety of plants in the South, including many trees,
are attacked by a root parasite, which is peculiar in that no
spores of any type have been found and it is known only by the
mycelium. Cotton and sweet potatoes are among the field
crops seriously affected. Several kinds of trees, especially bass-
wood, elm, cottonwood (poplars) and mulberry, are known to
be attacked and the roots killed. Plum trees and closely re-
lated species and varieties are more or less immune. The second-
ary symptoms are those which accompany any root-rot. The
leaves wilt and die when the roots are no longer able to function
in furnishing sufficient water and food materials. The roots
are invaded by the mycelium and the living tissues are killed.
104 MANUAL OF TREE DISEASES
Abundant growths of the sterile mycelium, which is coarse,
loosely matted and reddish brown, cover the affected roots. It
also grows over decaying sticks and other matter on the surface
of the ground. The mycelial growth has the appearance of a
quantity of tangled hair.
The mycelium spreads through the soil and is transported in
various ways by cultivating tools. It is said to display excep-
tionally destructive tendenciés in wet, badly drained soils and
during rainy periods. Loosening the soil, deep plowing and
drainage are said to reduce losses by retarding the spread of the
mycelium in the soil.
REFERENCE
Galloway, B. T., and Woods, A. F. Southern root-rot. Jn Diseases
of shade and ornamental trees. U.S. Dept. Agr. Yearbook 1896:
248-249. 1897.
CHAPTER X
BEECH DISEASES
THE beech (Fagus) is a common tree throughout eastern and
central United States. The American and different varieties
of the European beech are often used as ornamentals.
No serious diseases of the leaves of beech are known. Several
fungi cause leaf-spots occasionally and a sooty mold fungus often
occurs on the leaves (see pages 27 and 41). The beech is
subject, however, to several wood-rot diseases. The yellowish
sapwood-rot and common white wood-rot are very destructive
in the forest. The roots are parasitized by the flowering plant
commonly known as beech-drop. This parasite, however, does
not cause any damage.
YELLOWISH SAPWooD-RoT
Caused by Fomes fomentarius Fries
This sapwood-rot is common on beech, yellow birch and to
a lesser extent on other deciduous trees of northeastern and
north central United States. The fungus causing the decay is
also an important and rapid timber-destroyer throughout its
range. Where beech or birch is predominant and any unusual
amount of injury has occurred because of fire or limb breakage,
this sapwood-rot is found in great abundance and causes large
losses in timber values. It is also a common disease in Europe.
Symptoms.
The decay produced is distinctly a sapwood-rot at first,
starting in the outer layers next to the bark. As a result of
; 105
106 MANUAL OF TREE DISEASES
the activities of the fungus, the wood is reduced to a soft, light
yellowish punk. Black lines are formed between the decayed
and unaffected wood in places, or they may persist in the com-
pletely decayed portion. The rot extends into the heartwood
toward the center of the tree. Where splits or checks occur in
the decayed portion, a chamois-
like sheet of closely woven yel-
lowish mycelium is formed
which fills the space and can
with care be removed in large
pieces. Trees are usually first
affected in the upper half.
The sporophores or punks of
this fungus, which are formed
on the trunks of affected trees,
usually occur in large numbers
on each tree, the number vary-
ing with the extent of the de-
cay. The sporophores are not
confined to old branch wounds
as usually is the case with
heartwood-rotting fungi, but
emerge from apparently unin-
jured bark of the trunk. They
are easily recognized, being dis-
tinctly hoof-shaped and light to
dark gray on top. The lower
surface is light brown, with
rather large regularly arranged circular pores. Both surfaces
are smooth and velvety when young. A new layer of tubes is
added each year, which extends beyond the previous year’s
growth, producing an arched ridge (Fig. 11). The margin
of the sporophore is rather thin and the tube-surface is some-
what concave.
Fig. 11.— Fruiting-body of Fomes
fomentarius.
BEECH DISEASES 107
Cause.
The common yellowish sapwood-rot of beech and yellow birch
is caused by Fomes fomentarius. Spores drop out of the tubes
on the under side of the sporophores and are blown away. Any
wound in the bark exposing the sapwood furnishes a suitable
place for these spores to germinate and start a new mycelium.
The elements of the wood are largely destroyed, leaving a loose
mass of easily crumbled fibers. The effect of such a sapwood-
rot on the life of the tree is more serious and quickly destructive
than when equally extensive areas of the heartwood are de-
stroyed. The decay of the sapwood interferes with the trans-
portation of food materials and water, and thus produces the
same effect as mechanical girdling. After the tree dies, the
fungus works very rapidly as a saprophyte and destroys the re-
maining wood. For further details concerning the life history
and control of the wood-rotting fungi of living trees, see page 64.
REFERENCE
Schrenk, Hermann von, and Spaulding, P. Decay caused by Fomes
fomentarius. Jn Diseases of deciduous forest trees. U.S. Dept.
Agr. Bur. Pl. Ind. Bul. 149: 50-51. 1909.
Common WuitEeE Woop-Rot
Caused by Fomes igniarius Fries
This white wood-rot is a common and destructive disease of
beech. Many other kinds of deciduous trees are subject to the
same disease, principally poplar, oak and maple. In the Adiron-
dack Mountains as much as ninety per cent of the second growth
is sometimes made worthless for timber by this wood-rot. The
decay may extend outward into the sapwood and cause the death
of the parts above. The characteristics of the sporophores and
the decay are similar for all kinds of trees affected and are de-
scribed more fully under poplar diseases, page 305.
108 MANUAL OF TREE DISEASES
Unirorm WHITE Sapwoop-Rot
Caused by Hydnum septentrionale Fries
This sapwood-rot is sometimes found in beech and maple.
The affected wood is white, soft and uniformly rotted. Brown
zones border the decayed area. § Sometimes. single and double
black lines are irregularly distributed in the white rotted wood.
Large, heavy, fleshy fruiting-bodies are formed on the side of
the tree. A thick sheet of mycelium grows over the bark and
from this project numerous small brackets with the under sur-
face covered with teeth. The entire structure is white or yel-
lowish. For further details concerning this sapwood-rot, see
under maple diseases, page 234.
Waitt Butt-Ror
Caused by Fomes applanatus Fries
The heartwood of the roots and base of the trunk of beech is
occasionally destroyed by this rot. The decayed wood becomes
a little lighter in color than the normal wood. It is solid and
when split longitudinally numerous sinuous whitish tunnels are
apparent (Fig. 12). The decayed area is bordered by a broad
discolored zone. The sporophores of the causal fungus are
woody shelf-like bodies with a brownish or gray, smooth upper
surface and a white under surface. For further details concern-
ing this wood-rot, see under poplar diseases, on page 310.
PARASITIZED Roots
Caused by Epiphegus virginiana Barton
The roots of beech are parasitized by a peculiar flowering
plant, beech-drop (Epiphegus virginiana). This plant belongs
to the family Orobanchaceee, which comprises about one hun-
dred and fifty species, all of which are parasitic on roots of other
BEECH DISEASES 109
plants. The beech-drop is confined to America and is found
throughout the range of the beech. The plants grow abun-
dantly under beech trees in the woods but it is doubtful whether
much appreciable damage is done to the tree. In this respect
they may be compared
with the mycorhizas
of tree-roots (see page
82). The — beech-
drop plant is much
branched, leafless,
purplish-brown and
stands from four to
twelve inches high.
Small purplish flowers
are borne on_ the
stems inracemes. In
the soil the stem
ends in a white bulb-
like or elongate
rhizome which is coy-
ered with numerous
twisted, stiff out-
growths known as
grapplers. They serve
for support and may
absorb) water and
mineral nutriment. 3
All beech-drop plants, Fig. 12.— Beech wood decayed by Fomes
however, if carefully GP Pianonae:
dug, will be found to be attached to small beech roots. The
tissues of the rhizome of the parasite are fused with those
of the beech root so completely that at the point of attach-
ment it cannot be definitely recognized to which plant they
belong. The beech root is enlarged for some distance each way
110 MANUAL OF TREE DISEASES
from the point of attachment and often the end of the parasi-
tized root dies, leaving the beech-drop apparently attached to
the end of a root. Food material for the development of the
beech-drop is drawn from the beech root, and a large amount of
starch is formed and stored in the underground rhizome. The
entire plant dies during the fall and winter and apparently is
propagated as an annual by over-wintering seed. When de-
sired, the plants may be eradicated by pulling. This should be
done before the seeds are formed so as to prevent a crop the next
season.
REFERENCE
Schrenk, Hermann. Parasitism of Epiphegus virginiana. Amer.
Micros. Soc. Proc. 15: 91-128, pls. 1-10. 1894. (Bibliography
given.)
CHAPTER XI
BIRCH DISEASES
Many species of birch (Betula) occur as forest-trees in the
United States, especially in the northern parts. The native
species and imported varieties from Europe and Asia are
used extensively as ornamentals.
The leaf-rust is destructive when birch and larch are grown
close together. The leaf-blister diseases and the several leaf-
spot diseases (see page 29) are not common and do very little
damage. Birch is, however, commonly affected by several
wood-rots, the most important of these being the powdery
sapwood-rot and common white wood-rot. The other wood-
rots are not so common and are restricted more or less to certain
species of birch.
Lear-Rust
Caused by Melampsoridium betule (Schum.) Arthur
The leaves of various species of birch are sometimes affected
by this rust disease. It has been found in Massachusetts,
New York, Indiana and Washington and, therefore, probably
may appear in the northern states wherever birches and the
alternate larch hosts occur in proximity to one another. The
leaf-rust is not known to cause any great damage.
Symptoms.
Small, round, reddish-yellow pustules appear on the under
sides of the leaves in the summer. Later in the season a
second kind of pustule appears on the same leaves. ‘These are
lil
ie MANUAL OF TREE DISEASES
waxy-yellow and finally become brown and almost black. ‘They
may be abundant and thickly cover the under side of the leaves.
Cause.
The rust of birch leaves is caused by Melampsoridium betule.
This fungus occurs also in Europe, where it is known that the
basidiospores produced from the over-wintering teliospores on
the birch leaves cause the infection of the young needles of
larch and produce a blister-rust. The stage on larch has been
found rarely in this country but very probably exists more
generally and has been confused with the other rusts of larch
(see page 212).
YELLOW LEAF-BLISTER
Caused by Magnusiella flava (Farlow) Sadebeck
This leaf-blister disease occurs on white and paper birch in
northeastern United States. Small light yellow blisters are
formed on the leaves. The mycelium of the pathogene enters
the tissue of the leaf and causes a stimulus which results in an .
increase in number and size of the cells. The increased size
of the affected tissue results in the bulging blisters in the
leaf. The fungus produces asci containing ascospores on the
surface of the blisters.
For the control of this disease, the same methods used for
peach leaf-curl should give equally good results (Hesler, L. R.,
and Whetzel, H. H., Manual of fruit diseases, p. 277).
Rep LEAF-BLISTER
Caused by Ezxoascus bacteriospermus (Johanson) Sadebeck and Ta-
phrina carnea Johanson
Two species of the leaf-blister fungi are found on Betula
nant. The first mentioned has also been found on Betula
glandulosa. Although these pathogenes have been described
BIRCH DISEASES 113
only briefly from a few collections in northeastern United States,
Canada and Greenland, they may be more generally distrib-
uted and common on other species of birch. The lesions
are confined to the leaves and consist of large reddish brown
blistered areas, which may cause the leaf to curl. The mycelium
is confined to the space which it makes for itself between the
cuticle and the epidermal cells. Due to the parasitic activities
of these fungi, the tissues of the leaf are stimulated to an in-
crease both in number and size of the cells. This results in the
bulging and curling of the leaf between the more rigid veins.
For the control of these diseases, the same methods that are
used for peach leaf-curl should give results (Hesler, L. R., and
Whetzel, H. H., Manual of fruit diseases, p. 277).
PowpErRY Sapwoop-Rot
Caused by Polyporus betulinus Fries
Many species of birch are subject to this sapwood-rot through-
out the northern hemisphere. Yellow, white and paper birch
are commonly affected in the United States. Although the
fungus causing this rot is very common on injured and dead
birch trees, its importance in causing serious damage to healthy
trees is questioned. The fungus does not enter through branch
wounds and other injuries where heartwood is exposed and,
therefore, never causes a heartwood-rot of the living tree. This
rot is similar to the yellowish sapwood-rot caused by Fomes
fomentarius. In the case of both of these fungi, badly injured
or weakened trees are attacked and the sapwood is the first
part of the trunk decayed. Later, the fungi extend their
activities into the heartwood and the entire woody cylinder
of the trunk is destroyed. These wood-rots are nevertheless
important in the forest since the timber value of the species
they affect rapidly deteriorates as soon as the trees become
mature or injured.
I
114 MANUAL OF TREE DISEASES
Symptoms.
The decayed wood is yellowish and cracks radially and tangen-
tially. The rot is uniform and in the final stages it is very
light in weight and easily crushed to a powder.
The sporophores of the causal fungus are very common on
birch. They are corky annual bodies and are quickly destroyed
by insects. From the point of attachment to the trunk, they
Fig. 13.— Fruiting-body of Polyporus betulinus.
hang as bell-shaped bodies varying from three to ten or more
inches across. The outer surface of the sporophore is smooth
and light to dark mottled gray in color (Fig. 13). The margin
is incurved and projects below the under surface. The lower
surface is white or yellowish and roughened by ragged projec-
tions. The pores are small and the entire layer of tubes
separates easily from the fruiting-body.
BIRCH DISEASES 15
Cause.
The powdery sapwood-rot of birch is caused by Polyporus
betulinus. ‘The spores borne in the tubes on the under side
of the sporophore cause infection in wounds where the sapwood
isexposed. For a fuller discussion of the life history and control
of wood-rot fungi, see page 64.
REFERENCES
Sehrenk, Hermann von, and Spaulding, P. Decay caused by Poly-
porus betulinus. Jn Diseases of deciduous forest trees. U. S.
Dept. Agr. Bur. Pl. Ind. Bul. 149: 51-52, pl. 9. 1909.
Mayr, H. Zwei Parasiten der Birke, Polyporus betulinus, Bull.,
and Polyporus levigatus, Fries. Bot. Centralbl. 19: 22-29, 51-
57, pl. 1-2. 1884.
YELLOWISH SAPWooD-RotT
Caused by Fomes fomeniarius Fries
Yellow birch and beech are commonly affected by this sap-
wood-rot. Other kinds of deciduous trees are sometimes
attacked. The sporophores are perennial, light or dark gray
above, smooth and hoof-shaped with a concave, brown, velvety
tube-layer. The sapwood is decayed and only an easily
crumbled mass of fibers is left. A more complete description
of the symptoms of this wood-rot is given under beech
diseases, page 105.
Common WuitE Woop-Rot
Caused by Fomes igniarius Fries
The common and destructive white wood-rot of poplar,
beech, oak, maple and other deciduous trees affects the yellow
and paper birch. Although not as prevalent on birch as on
many other kinds of trees, it is often found, especially when
the birches are growing in mixture with the more susceptible
116 MANUAL OF TREE DISEASES
host species. The characteristics of the rot and the sporophores
of the causal fungus are described under poplar diseases, page
305. The hoof-shaped type of sporophore is more common on
birch. The sapwood of birch is invaded and the trees die. For
a general discussion of the life history, dissemination of the.
spores, mode of infection and control of the wood-rotting fungi,
see page 64.
Brown HeEArtTwoop-Rot
Caused by Fomes fulvus Fries
This heartwood-rot has been found common in river birch
in Missouri and Arkansas. Other trees are affected by the
same rot, especially species of Prunus. It is common also in
fruit-trees of the genus Prunus and in the olive in Europe.
But little information is available on the rot as it occurs in this
country. The decayed wood is brown for several feet upward
and downward from the point where the sporophores are
formed. In the final stages of the decay the rotted wood
crumbles easily. Plate-like sheets of mycelium which are
common in the brown checked wood-rot are lacking in the
case of this disease.
The sporophores are formed at wounds. They are perennial,
hard, woody and more or less hoof-shaped. The tops of the
older sporophores are smooth and very hard. Fine concentric
fissures are present but the top does not become roughened.
The lower surface is reddish brown and covered with minute
pores.
For the general life history and control of wood-rotting
fungi, see page 64.
REFERENCE
Schrenk, Hermann von, and Spaulding, P. Red heart-rot of birch
caused by Fomes fulvus. Jn Diseases of deciduous forest trees.
U. 8. Dept. Agr. Bur. Pl. Ind. Bul. 149: 47. 1909.
BIRCH DISEASES iS Ly/
WuitE Butt-Ror
Caused by Fomes applanatus Fries
The heartwood of the base of the trunk and the roots of birch
is sometimes destroyed by this rot. The decayed wood is
marked by numerous sinuous, white-stuffed tunnels which run
in the horizontal direction (see Fig. 12, page 109). The sporo-
phores of the causal fungus are woody, shelf-like bodies with a
brownish, smooth upper surface and a white under surface.
This heartwood-rot is more fully described under poplar diseases,
on page 310.
CHAPTER XII
BUCKEYE DISEASES
Tue four species of buckeye or A‘sculus native in the United
States are not important forest-trees. The Ohio and yellow
buckeye grow to be large trees in the river-bottom lands in
the central and southern states. A closely related European
species, the horse-chestnut, is extensively used as an orna-
mental.
Leaf-blotch is the most destructive disease affecting buckeye
and horse-chestnut. This disease occurs every year through-
out the range of the Ohio and yellow buckeye. The horse-
chestnut is often severely affected and defoliated in the north-
eastern states. A powdery mildew is also common on these
trees. The California buckeye is subject to a leaf-blight and
witches’-broom disease. ‘The wood and roots of the buckeye
are rarely diseased.
LEAF-BLoTCH
Caused by Guignardia esculi (Peck) Stewart
Throughout central, southern and eastern United States,
Ohio and yellow buckeye and the horse-chestnut are commonly
affected by this leaf-blotch. The disease is also known in
southern Europe. It is probable that the disease is present to
some extent on the other species of buckeye. A large percentage
of the foliage of horse-chestnut trees in parks and along streets
is affected every year. In the nursery this disease interferes
seriously with the growing of horse-chestnut stock. Repeated
118
BUCKEYE DISEASES 119
defoliation results in retarding the growth of the trees and
making them more susceptible to winter-injury.
Symptoms.
The lesions develop on the leaflets and petiole. When
first evident, the spots are irregular in outline, slightly dis-
colored and water-soaked in appearance. Later the center
of the spot becomes red-
dish brown and is sur-
rounded by a_ yellowish
zone which blends into
the green of the healthy
part of the leaf. Finally,
the entire affected area
turns brown and becomes
dried and brittle (Fig. 14).
The spots may be small
or may involve large areas
and cause a curling of
the leaflet. Small black
specks, the fruiting-bodies
of the pathogene, develop
either in the lighter colored
center of the brown blotch
or may be found distrib-
uted sparingly over the
entire dead area. Small
reddish brown lesions are
also sometimes formed on
the petioles.
Fig. 14.— Leaf-blotch of horse-chestnut.
Cause.
The leaf-blotch of horse-chestnut and buckeye is caused
by the fungus Guignardia e@sculi. Fruiting-bodies containing
120 MANUAL OF TREE DISEASES
ascospores are formed in the dead leaves after they fall to the
ground. ‘These spores mature at about the time the new leaves
appear in the spring and are disseminated by the wind and
spattering drops of rain. The lower leaves of young trees and
sometimes of older ones are the first to show infections in the
spring, because they are closer to the source of spore-production.
The first lesions soon develop the other type of fruiting-bodies
on the dead areas mentioned above. These appear as minute
black dots. In this stage the fungus is known as Phyllosticta
spheropsoidea. The spores are extruded from the fruiting-
body and are mainly distributed to healthy foliage by wind and
rain. By repeated generations of this kind of spores, all the
leaves on a tree may become infected in a short time. Con-
tinued or periodically rainy seasons are especially favorable for
an epiphytotic, since moisture conditions necessary for germina-
tion are furnished for each new crop of spores. At such times
the foliage from a distance appears as if scorched by fire and
considerable defoliation may result.
Control of leaf-blotch.
In the nursery it has proved beneficial, in preventing to some
extent the amount of primary infection, to plow under or rake
together and burn all dead leaves around the trees. This
practice can be. applied to shade-trees and thus eliminate to a
large degree the source of early infections. Even when such
measures are taken, a slight amount of infection may result
from bits of leaves left on the ground or from early infections on
trees in the vicinity. It is, therefore, necessary to supplement
these measures by coating the leaves with some efficient
fungicide at the time weather conditions and the development
of the leaves are conducive to infection. Spraying with lime-sul-
fur (1-50) or bordeaux mixture (5—5-50) will prevent infection.
The foliage is so dense, however, that thorough spraying cannot
be done without drenching the foliage. This may lead to
BUCKEYE DISEASES 121
unsatisfactory results for two reasons: spray mixtures do not
act as efficiently if the foliage is drenched, and lime-sulfur
may cause burning. Dusting nursery trees with a mixture of
finely ground sulfur and powdered arsenate of lead, in the pro-
portion of ninety parts of sulfur to ten of lead powder, has
proved effective in controlling this disease. It may, therefore,
be assumed that dusting shade and ornamental trees will be
equally effective. For further directions on spraying and
dusting for the control of leaf-diseases, see page 357.
REFERENCES
Stewart, V. B. The leaf blotch of horse-chestnut. Cornell Univ.
Agr. Exp. Sta. Bul. 371: 411-419, pl. 10, figs. 85-92. 1916.
Stewart, V. B. The leaf blotch disease of horse-chestnut. Phyto-
pathology 6: 5-19, pls. 2-4, fig. 1. 1916.
PowpEerY MILpEWw
Caused by Uncinula flerwosa Peck
The leaves of the buckeye and horse-chestnut are affected
by a powdery mildew, in eastern, southern and central United
States. The powdery white mycelium usually occurs only on
the under surface of the leaf in diffused spots. The black
fruiting-bodies of the fungus are just visible to the unaided eye
and are found scattered over the mildewed areas late in the
summer. For a discussion of the general life history and methods
of control of powdery mildew fungi, see page 37.
CurLED LEAr-BLiGHT AND WrtTcHEs’-BROoM
Caused by Exoascus esculi (Ell. and Ev.) Patterson
This disease is described on the California buckeye. It
occurs in several localities in California. The most noticeable
symptom is the production of many large witches’-brooms.
The leaves which are borne on the twigs composing the broom
[22 MANUAL OF TREE DISEASES
are killed before they mature and appear as frost-injured.
The mycelium is perennial in the twigs. The leaves of the
normal branches also become spotted and curled. Small
yellowish blisters. are formed which later turn to a dull red.
The fungus causing this disease is a close relative of the leaf-
blister fungus on oak (see page 239). Thedisease on the buckeye
does not cause very much damage to the trees, since the leaves
naturally remain on the tree only from April to early summer.
REFERENCE
Harkness, H. W. The eurled leaf (Ascomyces deformans). Zoe 1:
87-88. 1890.
Wuitr Sapwoop-Ror
Caused by Collybia velutipes Curtis
The sapwood of horse-chestnut is sometimes destroyed by
this toadstool. The wood becomes whitish and soft. The
spores of the fungus find entrance through wounds in the bark.
The fruiting-bodies of the causal fungus are toadstools with
yellow or brownish tops and gills. The bases of the stalks are
covered with a brown or black velvety growth of hairs. A
fuller discussion of this disease will be found under basswood
diseases, on page 103.
CHAPTER XIII
BUTTERNUT DISEASES
Tue butternut (Juglans cinerea) throughout its range in
eastern and central United States is subject to a few diseases
only. The most important of
these is the leaf-spot, which
also affects walnut and hickory.
This disease often causes a part
or all of the leaves to fall from
the tree in midsummer. Oc-
easionally the brown checked
wood-rot and common white
wood-rot are found in butter-
nut.
LEAF-SPOT
Caused by Marssonia juglandis
(Lib.) P. Magnus
This is the common leaf-
spot of butternut and walnut.
Irregular dark brown spots ap-
pear on the leaflets in early
summer. When infection is
abundant, a large amount of
the leaf-tissue is killed and the
leaves fall from the tree. The illustration shows a single
leaflet affected by this disease (Fig. 15).
The parasitic fungus causing the spots forms inconspicuous
123
Fig. 15.— Leaf-spot of butternut.
124 MANUAL OF TREE DISEASES
fruiting-structures on the under sides of the dead areas. Spores
from these structures are produced in abundance during wet
weather and are disseminated by rain. After the leaves fall,
perithecia are formed and from these ascospores are available
in the spring for primary infection. The name applied to the
perithecial stage is Gnomonia leptostyla (Fries) Ces. and De
Not. For a further discussion of leaf-spots and their control,
see page 27.
Common Wuite Woop-Rot
Caused by Fomes igniarius Fries
The butternut is sometimes affected by the common white
wood-rot, which occurs in many kinds of deciduous trees,
especially poplar, beech, oak and maple. The sporophores
of the fungus and the characteristics of the rot are similar for
all the kinds of trees affected and are described under poplar
diseases, page 305.
Brown CueckeD Woop-Rot
Caused by Polyporus sulphureus Fries
Butternut is occasionally affected by the brown checked
wood-rot, caused by the sulfur fungus. Many other kinds
of trees are affected by the same disease. The sulfur-yellow,
annual fruiting-bodies of the fungus together with the brown
powdery character of the rotted wood make it easy to identify
this disease. The tops of trees and large limbs may be killed
by the invasion of the sapwood and bark. A more complete
discussion of this wood-rot will be found under oak diseases,
page 247.
/
CHAPTER XIV
CATALPA DISEASES
THE two species of catalpa grow naturally in southeastern
and central United States. Both species are used as orna-
mentals. A few leaf-spot diseases cause some damage to
catalpa according to the locality and the season (see page 30).
Otherwise the tree is not subject to serious diseases, except
in plantations where the yellow wood-rot is destructive. The
predisposing of the catalpa to this wood-rot, by planting the
trees closely, illustrates the importance of branch wounds
as infection courts for the heartwood-rotting fungi. The
rapidity with which this rot progresses in the living tree com-
pared with the well-known durability of catalpa timber points
to the existence of some condition within the tree which favors
the development of the causal fungus.
YELLOWISH Woop-Rot
Caused by Polystictus versicolor Fries
This destructive heartwood-rot of the hardy catalpa may
be found wherever the trees grow. The disease is not common
in trees growing in the open. In close stands, however, the
limbs are killed by shading and after they break away, holes
are left which soon become infected by the spores of the fungus
causing this rot. The causal fungus is a very common sapro-
phyte, which grows everywhere on the wood of deciduous
trees. It may often occur as a semi-parasite in the bark and
125
126 MANUAL OF TREE DISEASES
sapwood of deciduous trees when they have been severely
injured. Otherwise the catalpa is the only tree in which this
fungus is known. to cause a distinctive heartwood decay.
Symptoms.
The affected trees may be recognized by the holes in the
trunk where the old branch stubs have rotted. Insects and
birds remove the decayed wood and use the hollowed-out areas
in the trunk for habitations. In cross-sections of the trunk,
the first indications of the decay show as pale colored areas.
The spring-wood of the annual rings becomes reddish with small
whitish areas. Later both the spring- and summer-wood of
the annual rings are similarly affected. The decayed wood then
becomes straw-yellow and is very soft and brittle. The de-
cayed area enlarges rapidly and eventually the sapwood may
be invaded. The decay may extend into the branches and
roots. Coppice is usually affected if the wood of the stump is
decayed.
The fruiting-bodies of the causal fungus are formed where
the bark is dead or on the affected wood when it is cut from
the tree. They are thin, tough shelving structures, hairy on
top and marked with variable yellowish and brown shiny zones.
The under surface is yellowish or white and covered with small
pores. The fruiting-structures are annual bodies but they
persist through the winter and may revive and shed spores in
the spring.
Cause.
The yellowish soft wood-rot of hardy catalpa is caused by
the fungus Polystictus versicolor. The spores from the tubes
on the under surface of the fruiting-bodies are wind-borne
and cause infection when they lodge in branch wounds. When
the trees are planted close together, the lower shaded branches
die and remain attached to the tree for some time. When
CATALPA DISEASES 127
they are broken off, a hole is left in the trunk which serves as
an excellent infection court. The mycelium progresses rapidly
in the wood. For further details concerning the life history
and control of the wood-rotting fungi, see page 64.
Control.
As a means of preventing loss from this rot in plantations,
it is advised that the lower limbs should be pruned off and the
wounds treated with a dressing. Directions for these opera-
tions will be found on page 345.
REFERENCES
Sehrenk, Hermann von. II Diseases of the hardy ecatalpa. Jn The
hardy catalpa. U.S. Dept. Agr. Bur. Forestry Bul. 37 : 49-58,
pls. 23-30, figs. 1-2. 1902.
Stevens, Neil E. Polystictus versicolor as a wound parasite of
eatalpa. Mycologia 4: 263-270, pls. 74-75. 1912.
Stevens, Neil E. Wood rots of the hardy catalpa. Phytopathology
2: 114-119, pl. 10. 1912.
Brown Butt-Ror
Caused by Polyporus (Poria) catalpe Schrenk
The heartwood and sapwood of the base of the hardy catalpa
is sometimes affected by this brownish wood-rot. The wood
becomes reddish brown and crumbly. It cracks along the
annual rings and at times across them, leaving spaces which
are filled by felts of mycelium. The fruiting-bodies of the
causal fungus are described as thin sheets of mycelium which
lie closely appressed to the diseased wood. The surface is
covered with small pores which are the openings of perpen-
dicular tubes in which the spores are borne. The fruiting-
structures are at first whitish, but later become yellowish and
brown. This fungus enters the tree through the branch wounds
in the same way as described under the yellowish wood-rot
128 MANUAL OF TREE DISEASES
(see page 125). The control is the same for both of these dis-
eases.
REFERENCE
Schrenk, Hermann von. II Diseases of the hardy catalpa. Jn The
hardy catalpa. U. S. Dept. Agv. Bur. Forestry Bul. 37: 49-58,
pls. 23-30, figs. 1-2. 1902.
CHAPTER XV
CEDAR DISEASES
Tue white cedar of the Atlantic Coast and incense cedar of
the Pacific Coast are affected by several destructive diseases.
These two trees belong to different genera (Chameecyparis
and Libocedrus). The diseases affecting the white cedar do
not occur on the incense cedar and vice versa. They are dis-
cussed together in this chapter merely for the convenience of
grouping them under the name common to both.
The two rust diseases (witches’-broom and branch-swellings)
on the white cedar cause serious deformation of the trees and
even death when they occur. The incense cedar is also af-
fected by a rust-fungus which causes witches’-brooms. ‘The in-
cense cedar is subject to a destructive heartwood-rot, which
is similar in appearance to the pecky heartwood-rot of bald
cypress. The brown felt-blight of incense cedar is important
at high altitudes.
Eastern LeEar-Rust
Caused by Gymnosporangium fraternum Kern
The white cedar is sometimes affected by this leaf-rust,
along the Atlantic Coast from Massachusetts to New Jersey.
No damage is done to the trees. The symptoms are confined
to the spore-masses of the pathogene which break through the
epidermis of the affected leaves. These spore-masses appear
in the spring and are small brown cushion-shaped pustules
about an eighth of an inch in diameter. The life history of
the causal pathogene is completed on the leaves of chokeberry
L 129
130 MANUAL OF TREE DISEASES
(Pyrus). The teliospores borne on the brown cushions ger-
minate and the basidiospores which are formed in this process
are blown away and cause the infection of the chokeberry
leaves. Alciospores produced on this host plant then cause
infection of the cedar leaves later in the season if they
chance to lodge on them. A more detailed explanation of
the life history and control of the rust-fungi belonging to the
same genus as this pathogene will be found under juniper dis-
eases, on page 192.
WestTERN LEAF-Rust
Caused by Gymnosporangium nootkatensis (Trelease) Arthur
Along the Pacific Coast in the Northwest, the yellow cedar
is affected by this leaf-rust. The symptoms are similar to the
eastern leaf-rust described above. The life history of the causal
pathogene is completed on the leaves of species of apple and
mountain ash. For a more detailed description of the habits
and control of the rust-fungi of this genus, see under eastern
leaf-rust, above, and juniper diseases, on page 192. The life
history of this rust-fungus differs, however, from all of the
other species of the genus Gymnosporangium, in that uredinio-
spores are formed on the cedar leaves. The teliospore-cushions
have not been found but undoubtedly occur on the cedar
leaves associated with the urediniospores.
Brown FE.tT-BuicHtT
Caused by Herpotrichia nigra Hartig
Incense cedar is one of the many conifers subject to this
disease in the Northwest. The leaves and twigs are covered
with a dark brown mat of mycelium (Fig. 16). The mycelium
also enters the leaf-tissues. Young trees and the lower branches
of older ones are killed and under conditions favorable for the
development of the causal fungus, the trees appear as scorched
CEDAR DISEASES iaul
by a ground fire. The same disease affects similarly spruce,
fir, juniper, arbor-vite and hemlock. It is described under
spruce diseases, on page 317.
Fic. 16.— Brown felt-blight on incense cedar.
EAsTERN WITCHES’-BROOM
Caused by Gymnosporangium myricatum (Schw.) Fromme
Witches’-brooms are found on white cedar along the At-
lantic Coast from Massachusetts to Delaware and in northern
Florida and southern Alabama. The witches’-broom and
branch-swelling diseases, both caused by similar rust-fungi,
132 MANUAL OF TREE DISEASES
are the most important diseases of white cedar. As in the case
of the other rust-fungi of cedar and juniper, an alternate host
is necessary for the completion of the life history of the fungus.
The witches’-brooms are never formed unless bayberry, sweet-
fern or wax myrtle shrubs (Myrica) are in close proximity to
the cedars. .
Symptoms.
The infected branches of the cedar become slightly swollen
and produce many short laterals which form a compact broom-
like growth. In the early spring, orange spore-horns about an
eighth or a quarter of an inch long project from the bark of
the distorted branches.
Cause.
The witches’-brooms of white cedar are caused by the rust-
fungus, Gymnosporangium myricatum. The life history of
this fungus is similar to that of the other cedar and juniper
rusts except that the alternate stage is developed on species
of Myrica. With this exception the life history described on
page 192 will apply in general to this species.
Control.
Since this rust-fungus requires the presence of both the
white cedar and species of Myrica in close proximity in order
to carry out its life history, a simple means of protecting the
cedars is afforded by destroying the bayberry, sweet-fern or
wax myrtle shrubs. If these plants can be eliminated for a
distance of several hundred feet or a mile from the white cedars,
no further exchange of spores will be likely and the cedars will
be safe from infection.
REFERENCES
Harshberger, J. W. Two fungous diseases of the white cedar. Proc.
Aead. Nat. Sei. Phila. 1902: 461-504. 1902.
Fromme, F. D. A new Gymnosporangial connection. Mycologia
6: 226-230. 1914.
CEDAR DISEASES 133
WESTERN Twic-BLicHt AND WircHEs’-BRoomM
Caused by Gymnosporangium Blasdaleanum (Diet. and Holw.) Kern
The incense cedar is attacked by this rust disease and con-
siderable damage is caused in some regions. The other trees
attacked by the same rust, in the other stage of its life history,
are cultivated apple, pear, quince, mountain ash and wild
species of apple, haw and service-berry. It is most destruc-
tive on the cultivated pear. The relation between the stages
of this fungus on the two types of hosts, one the incense cedar
and the other the plants of the apple family, is explained on
page 192, where the life history of these rusts is discussed.
Symptoms.
Two different effects are produced by this rust. When the
smaller twigs are infected, the first symptoms in early spring
are the small reddish brown spore-cushions which appear on
the surface of the scale-like leaves. During rainy weather
these cushions gelatinize and coalesce, forming yellowish masses
over the leaves. The leaves of the infected twig then turn
yellow and the twig dies.
When larger branches are infected, dense clusters of upright
branches are produced. The fungus fruits in the manner
described above on the younger twigs of the brooms and the
twigs are killed. Most of the damage caused by this rust on
the incense cedar is due to the development of the witches’-
brooms which at times seriously deform the tree.
Cause.
The twig-blight and witches’-broom of incense cedar are
caused by. the rust-fungus, Gymnosporangium Blasdaleanum.
The teliospores formed on the spore-cushions on the cedar ger-
minate and produce basidiospores, which when blown to the
134 MANUAL OF TREE DISEASES
apple host cause infection of the leaves. The zeciospores formed
sometime later infect the cedar leaves in the summer and au-
tumn. The fungus over-winters as mycelium in the cedar
leaves. Further details concerning the life history of rusts of
this type will be found under juniper diseases, on page 192.
REFERENCES
Jackson, H. S. A Pacific Coast rust attacking pear, quince, ete.
Second Biennial Crop Pest and Horticultural Report (Oregon
Agr. Exp. Sta.) 1913-1914: 204-212. 1915.
Jackson, H. S. A new pomaceous rust of economic importance,
Gymnosporangium Blasdaleanum. Phytopathology 4: 261-269,
pls. 12-13. 1914.
BRANCH-SWELLING
Caused by Gymnosporangium botryapites (Sehw.) Kern
The white cedar on the Atlantic Coast from Massachusetts |
to New Jersey and Pennsylvania and in southern Alabama
is often affected by this disease. The branch-swelling and
witches’-broom diseases of white cedar are the most serious
to this tree. Because, however, of the peculiar life history
of the rust-fungi which cause them, they are not generally
prevalent. The spores formed on the cedar branch-swellings
cause the infection of the leaves of the service-berry and an-
other type of spores formed on these leaves in turn causes
infection of the branches of the white cedar. Thus it is seen
that this fungus cannot exist unless the service-berry is in close
proximity to the cedars.
Symptoms.
The infected branches become swollen to two or three times
the normal size. The swellings are spindle-shaped and may be
several inches long. In the spring, brown pustules about an
eighth by a quarter of an inch burst through the bark of the
CEDAR DISEASES 135
swellings. These pustules become gelatinous and sometimes
may become confluent.
Cause.
The branch-swellings of white cedar are caused by the rust-
fungus, Gymnosporangium botryapites. The teliospores pro-
duced on the brown pustules on the cedar bark germinate and
form basidiospores which are innocuous to the cedar and can
infect only the leaves of the common service-berry. Here,
after a few weeks’ growth, eciospores are formed which, if
they find their way to the white cedar, cause the infection of
the branches and the swellings result after a year or two. For
further details concerning the life history of this type of rust,
see page 192.
Control.
Since the fungus can only exist in a region where the white
cedar and service-berry stand within a relatively short distance
of each other, the eradication of the service-berry serves as a
simple method of control. A separation of these two kinds of
trees by a few hundred feet may prove effective, although for
similar rusts of the juniper, a mile has been found to be a more
desirable distance.
REFERENCE
Harshberger, J. W. Two fungous diseases of the white cedar. Proc.
Acad. Nat. Sci. Phila. 1902 : 461-504. 1902.
Precky Hrartwoop-Rot
Caused by Polyporus amarus Hedgecock
The heartwood-rot of incense cedar, known as pin-rot, pecki-
ness, dry-rot or pin-disease, does great damage to this tree in
California and Oregon. All of the trees in a given area are
sometimes found to be affected, the middle portion of the
136 MANUAL OF TREE DISEASES
trunk being most often decayed. ‘Trees less than one or two
feet in diameter are not usually attacked.
Symptoms.
The appearance of the affected wood is very similar to the
pecky heartwood-rot of cypress (see page 97). Long lens-
shaped pockets are formed parallel with the grain of the wood.
The pockets are filled with a brittle brown mass of decayed
wood. The surface of the pockets is smooth and the wood
immediately surrounding is sound. The first evidence of
the decay is the darkened color of certain areas varying from
one to ten inches long and from one-fourth to one inch wide.
The affected wood in these areas is quickly reduced to a brown
charcoal-like mass. The pockets vary in arrangement and
number much as in the pecky heartwood-rot of cypress, and
a similar brown humus-like powder is found in the cells around
the margin. The sporophores of the causal fungus are hoof- or
bell-shaped bodies appearing at knot-holes in affected trees.
They are large bodies, several inches across, soft and spongy
when young and later becoming tough and chalky. The upper
surface is at-first light brown in color but soon becomes darker
brown, especially around the margin. The under surface is
yellow or yellow-green and turns brown with age. The pores
are small. The fruiting-bodies are soon destroyed by insects.
Cause.
The pecky heartwood-rot of incense cedar has been showr.
to be associated with the fruiting-bodies of the polypore, named
Polyporus amarus. This fungus was previously called Poly-
porus Libocedrus von Schrenk. The spores borne in the tubes
on the under surface of the fruiting-body cause infection of the
heartwood of the cedar at branch wounds. The sapwood is
not affected. For the details of the general life history and
control of wood-rots, see page 64,
CEDAR DISEASES 137
The pecky rots of incense cedar and cypress are, as pointed
out above, very similar in many respects but are now known
to be caused by different species of fungi.
REFERENCES
Schrenk, Hermann von. A disease of Taxodium distichum known as
peckiness, also a similar disease of Libocedrus decurrens known
as pin-rot. Missouri Bot. Gard. Rept. 11: 28-77, pls. 1-6. 1900.
Hedgeock, G. G. A new polypore on incense cedar. Mycologia 2:
155-156. 1910.
CHAPTER XVI
CHESTNUT DISEASES
Tue chestnut was until recently one of the important forest-
trees of New York, Connecticut, Pennsylvania and the Alle-
ghany Mountain region southward to’ Alabama. Besides its
commercial value as timber, the chestnut was important also
in its natural range as a much-favored ornamental. As an
orchard-tree, the varieties of the American and foreign species
are of relatively less importance.
Fifteen years ago the chestnut was not subject to any very
destructive diseases. With the appearance of the Endothia
canker or blight, however, the very existence of the species
seemed threatened. During the first ten years of the spread
of the fungus causing this disease, all the chestnut trees over
hundreds of square miles were killed. The disease is now
prevalent over practically the entire range of the chestnut
and apparently only a negligible number will escape destruction.
Itis unusual fora parasite to beso adapted that all the individuals
are equally susceptible to its attack. Many limiting factors
of resistance, temperature, moisture, seasonal conditions, dis-
seminating agents and the like serve to hold parasitic fungi
in check. The fungus causing the canker, however, is the
extreme example of an introduced parasite which is perfectly
adapted to the host and the environmental conditions of eastern
United States.
With the passing of the chestnut, it is scarcely necessary to
consider other less important diseases of this tree. Several
leaf-spot diseases are common on chestnut. In the North
138
CHESTNUT DISEASES 139
the one caused by Septoria ochroleuca is important. The large
leaf-spot is common in the South. Powdery mildews are
also common on chestnut leaves. The wood of the trunk is
decayed by several fungi and the shoe-string root-rot is very
destructive to chestnut (see page 78).
LarGeE LEAF-SPOT
Caused by Monochetia Desmazierii Sace.
Chestnut leaves are commonly affected by leaf-spot diseases.
The one here designated as the large leaf-spot is known to occur
in the southern Appalachian region in Virginia, North Carolina
and Georgia. It is often abundant, and causes some damage
by decreasing the functioning leaf-surface. Red oak leaves are
affected by the same disease.
Symptoms.
The symptoms are similar on the chestnut and red oak.
Small circular spots appear which are a quarter to one-half
inch in diameter, with a pale center and darker surrounding
zones, varying in color from yellow and gray to red-brown.
These spots enlarge rapidly and sometimes extend entirely
across the width of the leaf. Two or three such spots cause
the death of most of the leaf-tissue. The bands of colors as
described above are present in the older and larger spots. On
the under side of the leaf there is less evidence of the colored
zones and superficial mycelium of the fungus at the margin of
the spot causes a mildewed appearance. Early in the develop-
ment of the spots, numerous densely crowded black dots appear
on the dead leaf-tissue.
Cause.
Large leaf-spot of chestnut and red oak is caused by the
conidial stage of a fungus known as Monochetia Desmazierit.
140 MANUAL OF TREE DISEASES
But little is known of the life history of this parasite. The
spores produced in the black dot-like fruiting-bodies on the
spots have been proved to infect other healthy chestnut leaves.
In this way the fungus is probably disseminated by the rain
washing and spattering the spores. A perithecial stage of the
fungus is probably developed in the dead leaves on the ground
from which primary infection may be brought about in the
spring. This point is, however, undetermined.
Control.
Apparently no attempts have been made to control this
disease. General suggestions for the control of leaf-spot dis-
eases are given on page 33 and may be of some application to
this disease.
REFERENCE
Graves, A. H. The large leaf spot of chestnut and oak. Mycologia
4: 170-174, pl. 69, fig. 1. 1912.
Twic-BLIGHT
Caused by Spheropsis malorum Berkeley (= Physalospora cydonie
Arnaud)
This twig-blight is more common and destructive on chestnut
oak. It occurs occasionally on chestnut in central eastern
United States. Cankers are formed on the small branches
and twigs. The leaves wilt and turn brown in midsummer.
A fuller description of this disease and its control will be found
under oak diseases, on page 244.
ENDOTHIA CANKER
Caused by Endothia parasitica (Murr.) Ander. and Ander.
All the species of the genus Castanea are susceptible to this
destructive fungus. The trees included in this group are:
the common American chestnut, the eastern chinquapin, the
CHESTNUT DISEASES 141
European and the Japanese chestnut and the western chin-
quapin (genus Castanopsis). Pure strains of the Japanese
varieties are resistant while all the other species are very sus-
ceptible. From an economic standpoint, the American chest-
nut is by far the most important species.
The Endothia canker has also been known by the common
names, chestnut-blight and chestnut bark-disease. It was
first noticed in the New York Zoological Park in 1904. Since
that time it has spread for hundreds of miles, north, west and
south. It has proved to be the most destructive and rapidly
spreading tree disease known. The areas which have been
swept by the epiphytotic so far, are left apparently without a
single living chestnut tree. After many years of speculation as
to the past history of this disease, it was discovered in northern
China in 1913 and later in Japan. It is of slight importance in
its native home. There is little doubt now that the Japanese
chestnuts imported into this country brought with them this
unnoticed disease of the Orient. The increased destructiveness
of the disease in this country is due to the greater susceptibility
of the American chestnut. Many examples of epiphytotics due
to newly imported pathogenes are now a matter of record and
make the regulation of the interchange of plant products one
of the important phases of plant disease control.
Symptoms.
The tissues of the bark, including the cambium, are invaded
and killed. ‘The dead areas of bark, or cankers, are especially
conspicuous on the younger limbs where the normal bark is
smooth and green. They may be seen at a distance because
of the reddish color of the dead bark in contrast to the healthy
green bark. Usually the cankered area is slightly sunken,
due to the killing and drying of the tissues. On young rapidly
growing coppice, however, swollen areas (hypertrophy cankers)
with the bark split open lengthwise are commonly found. Dur-
142 MANUAL OF TREE DISEASES
ing midsummer the cankers enlarge at the rate of about one-
half inch in diameter each week. The usual shape of the canker
Fic. 17.— Endothia canker
of chestnut.
is ellipsoidal (Fig. 17). The margin of
the canker is usually regular and some-
what raised. On smooth bark, the thin
cork-layer is wrinkled, forming concen-
tric rings about the central point of
the canker. As the canker becomes
larger, the bark splits and after a time
falls away in shreds, leaving the wood
bare.
When the fungus is working in the
living tissues under the rough bark, there
are no outward indications of its pres-
ence until the fruiting-structures are pro-
duced in crevices of the bark. If the
bark is peeled from the edge of a canker,
the tawny mycelial fans are readily seen
(Fig. 18). The invaded tissues are
changed to a light brown in contrast to
the normal light colored healthy tissue
of the bark. The thick bark is reduced
to a mass of shreds which are a uniform
dark brown. The first layers of wood
under the cankered areas also become
brown.
The effects of the disease on the
general appearance of the tree are most
noticeable during the summer when the
trees are in leaf. In localities in which
the disease is common, large numbers
of the newly affected branches and twigs
are girdled by the cankers during the late summer and the
brown shriveled leaves hang to the limbs. This most striking
CHESTNUT DISEASES 143
symptom is common in July and August. The dead leaves
remain clinging to the limbs during the winter. If the girdling
of the limb is completed at a time when the burs are matur-
ing, these also remain on the tree over winter. In case the
girdling of the limb takes place in late autumn or early spring,
after the leaves and burs are shed, the new leaves never attain
their full size but remain pale green and distorted. This is a
common symp-
tom in May and
June. Cankers
on the trunk, es-
pecially if at the
base, cause the
development of
clumps of water-
sprouts or suckers
below the can-
kered area. Such
clumps of suckers
do not constitute
infallible signs of
the Endothia
canker, however,
since girdling
caused by any
agency will re-
sult in such out-
growths. After a tree has become thoroughly diseased — and
this may take only three or four years after the first ap-
pearance in the top of the tree — the brown fruiting-pustules
of the fungus cover the dead bark of the trunk and branches,
giving the tree a distinctive red-brown hue. The fungus con-
tinues to live saprophytically on the dead bark, as long as any
remains.
Fic. 18.— Mycelial fans between the bark and wood.
144 MANUAL OF TREE DISEASES
Cause of Endothia canker.
The canker of chestnut is caused by the perithecium-forming
fungus E’ndothia parasitica, formerly called Diaporthe parasitica.
The mycelium may grow parasitically in the bark, cambium
and sapwood of all parts of the chestnut tree above ground or
saprophytically on bark, twigs and dead parts of chestnut
and other trees. In the northern states new cankers may
originate at any time of the year from March to October. The
dissemination of the fungus to healthy trees or healthy parts
of the same tree is accomplished by many different agencies.
The spores or the mycelium itself may be carried by the wind,
water, birds, quadrupeds, insects and often by man. The
spores and mycelium live through the winter uninjured and
are ready for dissemination in the spring when many primary
infections are started. The agency most largely concerned in
the rapid spread of this fungus from tree to tree is the wind,
while water is important in washing the spores from a canker
in the top of a tree to other parts of the same tree and to others
close by. A few of the millions of spores produced on a single
canker find lodgment on the bark of other chestnut trees after
a shorter or longer journey from the place where they were
produced. Bringing the spores into contact with the healthy
bark is not all that is sufficient, however, for the spores must
find a wound of some kind to accomplish infection. The
spores germinate during periods of moist weather and the short
germ-tubes enter the soft tissue of the bark through the wound.
If there is no wound in the cork-layer, the germ-tubes of the
spores are unable to penetrate. An abundant growth of my-
celium rapidly develops from the germ-tube and in a few days
thin fan-like plates composed of thousands of threads of my-
celium, growing side by side, push out into the soft tissues of
the bark which lie between hard fibrous layers (Fig. 18). The
cells are killed a little in advance of the mycelium by certain
poisons which are excreted. Therefore, as these mycelial fans
CHESTNUT DISEASES 145
grow out from the point of infection in all directions, the tissues
of the bark are killed and soon a rapidly enlarging canker be-
comes apparent.
About a month after infection is accomplished, the surface
of the small canker becomes covered with numerous small
blisters (Fig. 19). These blisters are produced by balls of
mycelium formed under the cork-layer. Within these balls
are formed one of the types of spores (the conidia). During
moist conditions, following rains, .
long, twisted, yellow tendrils are
pushed out from the ruptured bark
over each blister (Fig. 19). The
tendrils are a mass of the very
small spores dried into this shape
after being squeezed through a
small opening. The next rain or
dew causes these tendrils to sepa-
rate into the thousands of spores
in each and they then may be
washed or spattered about by the
water or carried by animate agents.
Any one of these spores germinat-
ing where the germ-tube may enter
: Be Ohio Fic. 19.— Spore-horns of chest-
wounded bark-tissue may initiate rine eanicenetain ue:
a new canker.
On older and larger cankers, the blisters and yellow tendrils
of spores are confined to the margin, while nearer the center,
reddish brown pustules of mycelium are pushed out through
the bark. They measure when fully developed one-sixteenth
of an inch or more in diameter and have numerous papille on
the upper surface, each with a black dot in the tip (Fig. 20).
Within the brown pustules, buried below the surface of the
bark, are formed thirty or more cavities (perithecia), within
each of which are produced in great abundance another type
L
146 MANUAL OF TREE DISEASES
of spore (the ascospores). These spores are confined in small
delicate sacs, eight spores in each sac or ascus. During rainy
periods, these sacs swell and a certain number are forced up
through a tube leading from each
cavity to the black mouths at the
tips of the papillae. Once out-
side, the sacs burst and the eight
spores in each are shot into the
air where they are carried away
by the wind to great distances.
It is these wind-blown ascospores
which account for the extreme
rapidity of spread of this fungus
and make certain the infection of
all trees in the vicinity.
The living tissues of the bark
and the cambium are killed and
the mycelium enters the first layer
or two of the sapwood. The
indirect effect, when these tissues
are killed entirely around a limb,
is the withering and dying of the
parts above. The tree is thus
killed by the successive girdling
of the limbs and finally by cankers
developing on the trunk.
Control of Endothia canker.
Fig. 20.— Perithecial stage of After the chestnut canker had
eae a developed into a_ destructive
epiphytotic in Connecticut, New York, New Jersey and Penn-
sylvania, many investigations were begun to determine the
facts with regard to the disease and especially with a view
toward its control. A method was proposed of eliminating
CHESTNUT DISEASES 147
all diseased trees in spot infections somewhat distant from the
generally infested areas and the surrounding of the area already
invaded, by a zone from which all chestnut trees were to be cut
and removed. Much effort was expended in 1911 and 1912
to locate and map the regions in which this method would be
put into effect. Trial areas were located and all diseased trees
were cut, the timber peeled and the refuse burned. The
enormous effort involved in carrying out such a plan to control
the disease seemed far too expensive and the results too prob-
lematical to warrant their continuance. Pennsylvania, how-
ever, by the appointment of a special commission, attempted
to carry out the eradication methods in that state, but discon-
tinued the work in 1913 after two years’ trial. Since that time
the canker has continued its destruction and is gradually ex-
tending its range into the northern limits of the chestnut in
the New England states, western New York and Ohio and into
the southern Appalachians, threatening the total extinction of
the tree.
The attempt to control chestnut canker in individual trees,
when the expense of surgical methods is warranted, may be
successful. By the ordinary methods of canker eradication,
the diseased areas may be removed. Especial care is necessary
in order completely to remove the fungus. The bark should
be cut away at least an inch beyond the apparent edge of the
canker and the wood beneath the area of bark thus removed
must be chiseled out to a depth of an inch. Coal-tar dressing
then should be applied to the exposed wood and bark. After
all the cankers are removed, careful watch must be kept for
the appearance of new cankers. If the tree is large and has
rough bark, the chances of discovering all the diseased areas
in time are small.
The Japanese varieties are sufficiently resistant, if pure stock
and not grafted on American roots, to warrant their use as
orchard-trees. The crossing of the Japanese and Chinese with
148 MANUAL OF TREE DISEASES
the American chestnut may yield a resistant variety which
can be grown with relative immunity to this disease. The
advertisements of resistant chestnuts at this time, however,
are misleading, since none has been developed.
REFERENCES
Anderson, P. J., and Rankin, W. H. Endothia canker of. chestnut.
Cornell Univ. Agr. Exp. Sta. Bul. 347: 531-618, pls. 36—40,
figs. 77-101. 1914.
Anderson, P. J., and Babeock, D.C. Field studies on the dissemination
and growth of the chestnut tree blight fungus. Pennsylvania
Chestnut Tree Blight Com. Bul. 3: 1-32. 1913.
. Clinton, G. P. Chestnut bark disease. Connecticut Agr. Exp.
Sta. Rept. 36: 359-453, pls. 21-28. 1913.
Giddings, N. J. The chestnut bark disease. West Virginia Agr.
Exp. Sta. Bul. 187: 209-225, figs. 1-12. 1912.
Heald, F. D. The symptoms of chestnut tree blight and a brief de-
seription of the blight fungus. Pennsylvania Chestnut Tree
Blight Com. Bul. 5: 1-15, pls. 1-16. 1913.
' Metealf, H., and Collins, J. F. The control of the chestnut bark dis-
ease. U.S. Dept. Agr. Farmers’ Bul. 467 : 1-24, figs. 1-4. 1911.
Rankin, W. H., Field studies on the Endothia canker of chestnut in
New York State. Phytopath 4: 233-260, pl. 11, figs. 1-2. 1914.
Anonymous. Treatment of ornamental chestnut trees affected with
the blight disease. Pennsylvania Chestnut Tree Blight Com. Bul.
2:1-7. 1912.
STRUMELLA CANKER
Caused by Strumella coryneoidea Sace. and Winter
This canker occurs on chestnut but is more destructive on
various species of oak. On chestnut the sunken cankers are
distinguishable from the Endothia canker or blight, but in
general the tree is very similarly affected. The first signs of
the developing canker on smooth-barked trees appear as yellow-
ish or brownish slightly raised areas around a branch stub.
Many black nodules an eighth of an inch in diameter are
formed on the surface of the affected bark. When the bark
is peeled from the cankers, sheets of pure white or only
CHESTNUT DISEASES 149
slightly tan-colored mycelium are exposed. No indications
of mycelial fans are found as in the Endothia canker. The
cankers soon girdle the trunk and the parts above die. Large
elliptical conspicuous cankers with depressed centers surrounded
by concentric calluses are also formed on chestnut but not so
commonly as on the red and black oak. These cankers and
the fungus causing them are described on page 245.
Brown CHECKED Woop-Rort
Caused by Polyporus sulphureus Fries
The heartwood and sapwood of chestnut are often decayed
by the sulfur fungus. The same rot is common in oak, maple,
walnut, butternut, locust, alder and other trees. The wood
is reduced to a red-brown, powdery mass which separates into
cubes. The sporophores are conspicuous, annual, orange and
sulfur-yellow colored bodies which form at wounds or on the
bark where the fungus has decayed the sapwood. The tops
of the trees or large limbs may be killed by the girdling action
of the mycelium in destroying the sapwood and bark. A fuller
description of the symptoms and cause of brown checked wood-
rot which are similar for all the trees affected is given under oak
diseases, page 247.
Straw-CoLorED HEARTWOOD-RotT
Caused by Polyporus frondosus Fries
This heartwood-rot may be found in the base of the trunks
of chestnut. The trees do not become hollow. The advancing
decay first shows as long, slender, white streaks. Later the
wood becomes tan- or straw-colored and is held together by
the less affected medullary-rays. The sporophores of the causal
fungus arise from the ground around the affected tree. They
are large, fleshy, globose structures with many overlapping
150 MANUAL OF TREE DISEASES
shelves borne on branches arising from a single central stalk.
For further details concerning this heartwood-rot, see under
oak diseases, page 259.
Waite Pieep Burtr-Rotr
Caused by Polyporus croceus Fries
(= P. Pilote Schw.)
The heartwood of the base of chestnut and oak is often
attacked by this white piped-rot. It is also occasionally
found in the tops of the trees. The rot extends into the roots
and is one of the most destructive wood-rots of the butts of
oak in the Ozark Mountains. This disease has been found in
chestnut and oak in various localities in eastern and central
United States and probably is generally distributed over this
area. When chestnut trees have dead limbs in the top, the
decay may be found in the upper portion of the trunk. The
coppice method of reproduction of the chestnut is responsible
for the prevalence of this rot in the base of the trees.
Symptoms.
The affected wood is at first brownish and water-soaked.
Later white areas appear between the spring- and summer-
wood. These areas become larger and the wood between is
firm and dark brown. Finally the white areas enlarge and
become hollow cavities with white margins. The brown wood
between the pockets at this stage is brittle and breaks apart
easily into concentric layers. The sporophores of the causal
fungus are buff- or orange-colored and are found sometimes on
living trees or on fallen trees and old logs. They are soft and
watery annual shelf-like bodies, three to six inches across.
Cause.
The white piped butt-rot of chestnut and oak is caused by
Polyporus croceus or Polyporus Pilote. Infection usually
CHESTNUT DISEASES 151
occurs at the base of the tree through the connection of the
coppice sprouts with the old stumps. For further details
concerning the life history of wood-rotting fungi and the nature
of the decay process caused by these fungi, see page 64.
REFERENCES
Long, W. H. Three undescribed heart-rots of hardwood trees, es-
pecially of oak. Jour. Agr. Res. 1: 109-128, pls. 7-8. 1913.
Schrenk, Hermann von, and Spaulding, P. Piped-rot of oak and
chestnut. Jn Diseases of deciduous forest trees. U. S. Dept.
Agr. Bur. Pl. Ind. Bul. 149: 39-40, pl. 5. 1909. (Note: The
piped-rot of oak described is due to P. Rheades and of chestnut
to P. croceus.)
CHAPTER XVII
ELM DISEASES
Fig. 21.— Leaf-spot of elm.
152
Tue elms (Ulmus) are
common forest and orna-
mental trees east of the
Rocky Mountains. They
are exceptionally free from
specific diseases caused
by parasites. Wound-rots
and slime-flux are common
in the crotches of the large
limbs. Chaining is often
necessary to prevent split-
ting at the crotches.
LEAF-SPoT
Caused by Gnomonia ulmea
(Sace.) Thiim.
This is the most com-
mon of the leaf-spot dis-
eases of elm. In wet
seasons, the spots become
so abundant that defolia-
tion results. The fungus
causing this disease usu-
ally occurs abundantly
ELM DISEASES 153
every season on the leaves in late autumn just before the
leaves fall.
The first indications of the spots are seen on the upper surface
of the leaf. The dead leaf-tissue is grayish, and either scat-
tered over the spot or
grouped in the center are
one or more black pustules
(Fig. 21). The under sur-
face of the leaf shows no
evidence of the spot until
later in the season, when
brown dead areas appear
with a few raised pustules.
After the leaves fall to
the ground, fruiting-bodies
containing ascospores de-
velop which are the source
of primary infection the
following spring. The
pyenidia of many species
of fungi are found on elm
leaves and it is not known
which one of these is con-
nected with the Gnomonia.
For a further discussion of
leaf-spots and their con-
trol, see page 27. Fic. 22.— Powdery mildew of elm.
PowpEery MILpEws
Caused by Uncinula macrospora Peck, Microsphera alni (Wallr.)
Salmon and Phyllactinia corylea (Pers.) Karst.
Three species of the powdery mildew fungi attack the leaves
of elms in the United States. In the case of all three species
the characteristics, so far as visible to the unaided eye, are
154 MANUAL OF TREE DISEASES
similar. The first two species mentioned above occur on both
sides of the leaf, while the last usually affects only the under
side. The spots are usually not distinct and the mycelium may
be only slightly noticeable (Fig. 22). The black fruiting-
bodies are formed in patches or scattered over the leaf in all three
species but require microscopic examination to determine their
specific characters. The life histories and methods of control
of the powdery mildew fungi are discussed on page 37.
Brown Woop-Rot
Caused by Pleurotus ulmarius Bull.
The white elm is often affected by this brown wood-rot. The
toadstool fruiting-bodies of the causal fungus are commonly
seen in the autumn projecting from pruning wounds and crotches
between limbs. The heartwood is first affected and later the
decay extends into the sapwood. The wood becomes brown
and is easily separated into its respective annual rings. The
cell-walls of many of the fibers of the wood are destroyed or
partially delignified.
The sporophores of the fungus are large, fleshy annual struc-
tures attached to the wood of the tree by a long and more or
less eccentric stalk. The top is convex, smooth, and varies
from white to yellow or brown. On the under surface are
many radiating gills or pendent plates which are notched at
the point of attachment to the stalk. It is on these gills that
the spores are formed.
REFERENCE
Learn, C. D. Studies on Pleurotus ostreatus Jacqu. and Pleurotus
ulmarius Bull. Annales Mycol. 10: 542-556, pls. 16-18. 1912.
CHAPTER XVIII
FIR DISEASES
Tue firs are important forest-trees of western and north-
eastern United States. The balsam and Fraser fir are the only
native species in the East. Several species are common in the .
West. The Douglasspruce or fir of western United States is also
considered in this chapter for convenience. Many native and
exotic species of fir are extensively used as ornamentals through-
out the country.
The word “fir” is properly restricted to the genus Abies,
with erect cones and flattish leaves, and the word “spruce”
to the genus Picea with cones mostly becoming pendulous
and keeled leaves. The red fir or Douglas spruce is of the
genus Pseudotsuga.
Fir is particularly subject to diseases of the wood. Many
of the wood-rotting fungi which attack fir are also equally de-
structive to pine, spruce, larch and hemlock. The root-rots
common to conifers also cause considerable damage to fir
wherever it grows. In western United States the dwarf mistle-
toes seriously deform the fir. Besides these important dis-
eases, the fir is occasionally affected by leaf blister-rusts, leaf-
cast, rust witches’-broom and the gray mold twig-blight. These
diseases are limited in their distribution by various environ-
mental and host relations.
Lear Buister-Rusts
Caused by species of Uredinopsis, Pucciniastrum and Calyptospora
Several very similar blister-rust diseases of the needles of
fir (Abies and Pseudotsuga) are found in the United States.
155
156 MANUAL OF TREE DISEASES
In all these diseases the general symptom is the production
from the under surface of the needles in early summer of white
bladdery pustules or blisters. Although found rather commonly
throughout the range of the firs, none of these diseases is known
to cause any great damage. A yellowing of the foliage and
defoliation may occur at times. The different species of rust-
fungi causing these diseases require certain other kinds of
plants on which to complete their life history. In all the species
the spores (zciospores) developed in the white blisters on the
* fir cause the infection of the other host plant if it is in the close
vicinity. On this second host urediniospores are formed in
small reddish or yellowish spots in midsummer and in the
autumn the teliospores develop either within the epidermal cells
or on the outside of the leaf or stem. The teliospores over-
winter and germinate in the spring, producing basidiospores
which when blown to the fir infect the young needles.
Fern rust.
The most common and generally prevalent of the blister-
rust fungi of fir needles have alternate stages on species of ferns
and belong to the genus of fungi known as Uredinopsis. The
blister-stage on the fir needles is known as Peridermium balsa-
meum Peck and P. pseudo-balsameum (D. and H.) Arthur and
Kern. These rusts occur on balsam fir in the northeastern
states and on Alpine, grand and noble fir in the Northwest.
Recent investigations have shown that these blister-rusts are
the alternate stages of five previously recognized species of
Uredinopsis on ferns as follows : —
U. osmunde Magn. on species of Osmunda ;
U. mirabilis (Peck) Magn. on species of Lorinseria and Onoclea ;
U. struthiopteridis Strémer on species of Anchistea and Matteuccia ;
U. phegopteridis Arthur on species of Phegopteris ; ;
U. Atkinsonii Magn. on species of Asplenium and Dryopteris.
These rusts are not distinguishable from one another in the
ecial stage on the fir needles, and further investigation may
FIR DISEASES 157
prove that they should be reduced to one species with racial
differences as to the fern hosts preferred.
A very similar blister-rust of the second-year needles occurs
in the northwestern states on Alpine and grand fir and has
been found to be due to Uredinopsis pteridis Weir and Hubert
on species of Pteridium. The life history of this species is
different from those above mentioned in that the teliospores
do not over-winter. The basidiospores form in late summer
but the fir needles infected in the autumn do not show the
white blisters until early the following spring.
In the other species the young newly formed needles are
infected in the spring by basidiospores from over-wintered
teliospores, and the white blisters are formed later in the same
season. On the fern leaves the urediniospores show as yellow
or brownish rust-spots.
Fireweed rust.
Another of the white blister-rusts occurring to some extent
on fir needles in this country as well as in Europe is caused by
Pucciniastrum pustulatum (Pers.) Dietel. This pathogene
has its uredinial and telial stages on species of Epilobium, es-
pecially E. angustifolium, the great willow-herb or fireweed.
Although the fungus occurs on several species of Epilobium,
teliospores are known certainly to occur only on E. angusti-
folium.
Blueberry rust.
A common blister-rust of fir needles in Europe is caused by
Calyptospora columnaris (Alb. and Schw.) Kiihn. It has its
alternate stages on species of Vaccinium. On these latter
plants the stems are attacked and become swollen. The in-
fected stems grow erect and become much taller than sur-
rounding bushes. The stems are at first reddish and later
become brown or black. The teliospores are formed in the
158 MANUAL OF TREE DISEASES
epidermal cells of the stems and over-winter there. The
germ-tubes bearing basidiospores are pushed out the fol-
lowing spring and infection of the fir needles is accomplished
when the basidiospores are blown to them. The white blisters
appear on the needles in late spring. The affected needles
may appear yellowish and usually drop off in late summer. The
blister-stage on the fir is known as Peridermium columnare
Schmidt and Kuntze. This fungus is common throughout the
United States on blueberry but is rarely found on firs.
Unconnected rusts.
Two blister-rust fungi attacking fir needles (Abies) in north-
western United States have been named provisionally Peri-
dermium ornamentale Arthur and P. Holwayi Sydow. These
two forms may represent only a single species, however, as
they are very similar microscopically. The alternate stages
of these rusts are as yet unknown.
REFERENCES
Weir, J. R., and Hubert, E. E. Observations on forest tree rusts.
Amer. Jour. Bot. 4: 327-335, figs. 1-2. 1917.
Clinton, G. P. Hetercecious rusts of Connecticut having a perider-
mium for their ecial stage. Connecticut Agr. Exp. Sta. Ann.
Rept. 1907-1908 : 369-396, pls. 25-382. 1908.
Arthur, J. C., and Kern, F. D. North American species of Perider-
mium. Bul. Torrey Bot. Club 33: 403-438. 1906.
Fraser, W. P. Cultures of some hetercecious rusts. Mycologia 3:
67-74. 1911.
Fraser, W. P. Cultures of hetercecious rusts. Mycologia 4: 175-
1954 LOU:
Fraser, W. P. Further cultures of hetercecious rusts. Mycologia 5:
233-239. 1913.
Fraser, W. P. Notes on Uredinopsis mirabilis and other rusts. My-
ecologia 6: 25-28. 1914.
Hedgecock, G. G. Notes on some western Uredineew which attack
forest trees. Mycologia 4: 141-147. 1912.
FIR DISEASES 159
Lrear-Rusts
Caused by Melampsora arctica Rostrup and M., albertensis Arthur
Two species of rust-fungi cause pale yellowish or white
pustules on fir needles. These rusts are very similar to the
blister-rusts described above except that no bladder-like cov-
ering 1s developed over the pustules.
Willow rust.
Arust of balsam fir needles similar to the blister-rusts above
mentioned is found in eastern Canada and may occur in the
extreme northeastern part of the United States. This disease
is caused by Melampsora arctica Restrup. The uredinial and
telial stages are formed on arctic species of willow. The ba-
sidicspores are formed in the spring from over-wintering telio-
spores and infect the new fir needles. White pustules are
preduced on the under surface of the fir needles in. midsummer.
Poplar rust.
A rust of poplar leaves in northwestern United States and
the adjacent parts of Canada has its alternate stage on fir
(Pseudotsuga) needles causing white pustules. This fungus is
known as Melampsora albertensis Arthur and was previously
called Ceoma occidentalis Arthur on Pseudotsuga mucronata.
LEaF-Cast
Caused by Lophodermium nervisequum Fries
The needles of balsam fir are often killed by this disease.
Trees of all ages are affected and complete defoliation may
result. This is especially true of small trees. The leaves be-
come yellow and brown during the summer and autumn. The
fruiting-bodies of the causal fungus break through the epi-
dermis of the brown needles in long black lines. The spores are
mature the following spring and infection may occur during
160 MANUAL OF TREE DISEASES
any prolonged wet period until the spores are all disseminated.
For further details concerning the leaf-cast diseases of conifers,
see page 38.
REFERENCE
Spaulding, P. Notes upon tree diseases in the eastern states. My-
cologia 4: 148-151. 1912.
Rust WrtcHeEs’-Broom
Caused by Melampsorella elatina (Alb. and Schw.) Arthur
This rust disease causes witches’-brooms on various species
of fir (Abies) throughout their range in the United States. It
also occurs commonly in Canada, Mexico and Europe. The
young affected twigs are dwarfed and develop numerous up-
right laterals forming a broom-like growth. If the twigs are —
infected at a place where no buds are present, only gall-like
enlargements of the bark are formed. The fungus grows out
into the branches and leaves of the broom. The leaves re-
main small and yellowish. There develop in midsummer
from the under surface of these dwarfed leaves two rows of white
blisters. The leaves then fall, leaving the broom bare during
the winter. New growth of the twigs and new infected leaves
are formed the following season. In this manner the broom
develops for several years and produces a crop of spores each
season.
The spores (eeciospores) from the fir needles infect species
of. Alsine and Cerastium. On these plants very small orange-
red or yellowish pustules are formed in late summer. Ure-
diniospores are produced in these pustules which may infect
other plants of the same species. Teliospores are formed later
in whitish or pale reddish spots on the under surface of the leaf.
They germinate the following spring producing basidiospores
which may infect the fir twigs. The mycelium is perennial in
both sorts of hosts.
FIR DISEASES 161
Control.
This witches’-broom of fir may be controlled by eradicating
all sandwort and chickweed (Alsine and Cerastium) from the
immediate vicinity of the firs.
REFERENCE
Hartig, R. Aicidium (Peridermium) elatinum. Jn Text-book of
the diseases of trees, pp. 179-182, figs. 109-112. 1894.
Gray Moxitp Twic-Buicut
Caused by Botrytis cinerea Fries
This disease of the current season’s twigs is most important
on Douglas fir, although other firs, pine, spruce, larch and hem-
lock may be affected. The disease is common in certain lo-
ealities in Europe and North America, both in nurseries and
in the forest. It has been reported as destructive, especially
to Douglas fir in nurseries, forest plantings and to some degree
on the older trees, in several countries of Europe. In the
forests of northwestern United States it occurs on Douglas fir,
grand fir, western larch and western hemlock. It has not as-
sumed great importance in any area but causes considerable
cumulative damage.
Symptoms.
The most obvious general symptom of this disease is the
withering, curling and dying of young twigs of the season.
Seedlings and young trees may be killed. Late in the season
black bodies the size of a pin-head are formed on the affected
twigs and on the leaves, especially at the base of the season’s
growth. The twigs of young pine may be dwarfed, the needles
remaining short and the twig becoming twisted. Under moist
conditions, a more or less luxuriant mycelial growth occurs,
forming a gray mold over the affected leaves and twigs.
M
162 MANUAL OF TREE DISEASES
Cause.
The gray mold twig-blight of conifers is caused by the fungus
Botrytis cinerea. The name first given to this fungus on conifers
was Botrytis Douglas Tubeuf. In some publications this
fungus is erroneously called Sclerotinia Fuckeliana (De Bary)
Fuckel, due to a suspected connection of the Botrytis with this
ascomycete. Spores are borne in abundance on the gray mold-
like growth of mycelium over the affected parts. These spores
are wind-disseminated and serve to distribute the fungus dur-
ing the summer. ‘The small black, more or less globose bodies
formed on the twigs and needles are called sclerotia. They are
resting structures composed of mycelium which is rich in re-
serve food material and covered by a black rind-tissue of
mycelium. The fungus over-winters in this way and many
upright branches bearing spores are sent out from the sclerotia
in the spring.
The mycelium within the needles and twigs causes at first
an enlargement of some of the tissues and later their death.
Abundant atmospheric moisture is required for the general and
destructive distribution of the fungus in a given region. Fogs
are conducive to epiphytotics. This is due to atmospheric
moisture stimulating an abundant growth of superficial my-
celium which is necessary for the formation of the spores. Also
these same conditions insure that a larger percentage of the
spores can germinate and cause infection.
Control.
Since the severity of attack is largely dependent on a con-
tinuously humid atmosphere, any measures which will lead to
a greater circulation of the air will serve in a measure to control
this disease. Damp soil and close planting should be avoided
for the more susceptible trees. In the nursery and in young
plantations weeds and any plants or artificial structures which
shade the trees should be removed.
FIR DISEASES 163
REFERENCES ON Gray Moup Twic-Buicut
Weir, J. R. A Botrytis on conifers in the northwest. Phytopathology
221d, 1912:
Smith, R. E. Botrytis and Selerotinia: their relation to certain
plant diseases and to each other. Bot. Gaz. 29: 369-407, pls.
1-3, figs. 1-3. 1900. ;
Tubeuf, C. F. von. Botrytis Douglasii. Eine neue Krankheit der
Douglastanne. Beitriage zur Kenntniss der Baumkrankheiten,
pp. 4-8, pl. 1. 1888.
MistLeTorE Buri AND WITcHES’-BRooM
Caused by Razowmofskya Douglasii (Englem.) Kuntze
Douglas fir is seriously damaged in northwestern United
States by this species of dwarf mistletoe. The roots of the
germinating mistletoe seeds enter the bark through wounds.
Swellings of the stem and enormous brooms are formed by
the abnormal branching from the affected parts. Burls are pro-
duced on the larger limbs and the trunk. The general effect
of the deformed growths is a diversion of the growth energies
of the trees to these parts. A dwarfing of the tops and a de-
creased amount of foliage results. Large trees are not directly
killed by the mistletoe infestation, but the trees are suppressed
to the degree that insects and fungi cause a higher mortality
than in stands of normal trees. A general discussion of the
mistletoe parasites on trees will be found on page 54.
REFERENCE
Weir, J. R. Mistletoe injury to conifers in the northwest. U. S.
Dept. Agr. Bul. 360: 1-38, pls. 1-4, figs. 1-27. 1916.
Precky Woop-Ror
Caused by Trametes pini Fries
This wood-rot is commonly known as red-rot, ring-shake and
peckiness, and is the most destructive wood-rot of fir, spruce,
164 MANUAL OF TREE DISEASES
larch and pine in the United States. The symptoms in fir are
similar to those in spruce which are described on page 324. The
pockets are larger than those found in spruce and the wood is
thab @eyoect ce
Fia. 23.— Pecky wood-
rot; early stage in Doug- Fig. 24.— Pecky wood-rot in
las fir. Douglas fir.
largely destroyed. In Douglas fir the pockets are at first cir-
cular white areas (Fig. 23). Later the pockets increase greatly
in number and finally the wood is honeycombed (Fig. 24).
Somewhat different symptoms are shown in larch and pine and
are described on pages 215 and 291 respectively.
The life-history, dissemination of the spores and mode of in-
fection of the wood-rotting fungi are treated in a general discus-
sion on page 64.
FIR DISEASES 165
RepD-BRowNn Sapwoop-Ror
Caused by Fomes pinicola Fries
The red-brown sapwood-rot is one of the most common dis-
eases of spruce, pine, fir, larch and hemlock, wherever these trees
grow. ‘The fungus causing this wood-rot occurs less frequently
in living trees than it does on dead standing trees and logs. It
is thought that the fungus usually attacks living trees which
are badly wounded or in generally poor health. Vigorous
healthy trees are more rarely affected. The decay progresses
very rapidly and the wood is reduced to a light easily pulver-
ized mass. The wood of beech, birch, maple and other de-
- clduous trees is also destroyed by this fungus.
Symptoms.
In longitudinal section, the first evidence of the decay shows
as whitish spots or streaks irregularly placed. The white spots
have reddish brown centers. At this stage the wood is punky
and brittle. The spread of the mycelium from these centers
soon results in a uniform red-brown, easily pulverized mass of
loose fibers. The decayed wood shrinks in all directions, leav-
ing numerous cracks which are filled with white mycelial felts.
These felts are largely responsible for holding the decayed wood
from falling to pieces.
The fruiting-bodies of the fungus are formed abundantly
and are the most conspicuous of the various shelf-fungi in
coniferous forests. When growing from wounds on_ living
trees, they are usually hoof-shaped. On logs and dead wood
they are broader and thinner. The upper surface is marked
by broad rounded concentric folds, each representing the re-
sult of a year’s growth. From the center of the top to the
margin, the color varies from black to brown and reddish brown.
The rounded margin is yellowish in the early summer and later
becomes reddish yellow or deep red. The surface of this bright
166 MANUAL OF TREE DISEASES
colored. zone appears as if varnished. The under surface is
yellowish brown and covered with minute pores.
Cause.
The red-brown sapwood-rot of conifers is caused by the
fungus Fomes pinicola. Infection occurs in wounds which ex-
pose the sapwood of the tree. The wood fibers are not de-
stroyed completely but are reduced to weak thin-walled struc-
tures with numerous cracks and fissures. The life history and
control of wood-rotting fungi is more fully discussed on page 64.
REFERENCES
Schrenk, Hermann von. Polyporus pinicola (Swartz) Fr. In Some
diseases of New England conifers. U.S. Dept. Agr. Div. Veg.
Phys. and Path. Bul. 25: 24-31, pls. 3-5, fig. 2. 1900.
Atkinson, G. F. Polyporus pinicola. Jn Studies of some shade tree
and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bul.
193 : 222-297, figs. 80-81. 1901.
Hedgecock, G. G. Notes on some diseases of trees in our national
forests. IV. Phytopathology 4: 181-188. 1914.
Srrincy Rep-Brown HEARTWoop-RotT
Caused by Echinodontium tinctorium Ellis and Everhart
The destructive stringy red-brown heartwood-rot of fir,
spruce and western hemlock is a common disease of these trees
in western United States. White, Alpine, grand, noble and
Douglas fir, Engelmann spruce and western hemlock are known
to be affected by this wood-rot. The older stands of firs in the
northwestern forests are so badly damaged by this rot that
they are practically worthless.
Symptoms.
The first indication of this heartwood-rot is noticeable in the
branch stubs through which the fungus finds entrance to the
heartwood. The wood of the branch stubs is a rusty brown
FIR DISEASES 167
and from the exterior this rot is identified by the rusty knots.
In the heartwood there are three distinct stages in the progress
of the decay. As the rot advances, the newly affected wood
is discolored and spongy, with occasional light brown spots.
This advance rot, as it is called, extends from two to six feet
beyond the distinctly red-brown disorganized wood. In more
Fie. 25.— Fruiting-body of Echinodoniium tinctorium.
advanced stages, the wood turns red-brown and is soggy. The
annual rings are separated into sheets which appear as brown
cylinders one inside the other. Soon, however, the wood of
these partially destroyed rings is dissolved and the tree be-
comes hollow. The decay may proceed until only a thin shell
of sapwood remains.
168 MANUAL OF TREE DISEASES
The sporophores of the causal fungus are formed at the
rusty knots and are large hoof-shaped bodies, gray or black
above and with numerous large and firm straw-colored or gray
spines on the under surface (Fig. 25). The inner substance of
the bodies is bright rusty red. The American Indian used the
red fungous material for making war paint and thus this
fungus has been named the Indian paint-fungus. .
Cause.
The stringy red-brown heartwood-rot of. western conifers
is caused by Hchinodontium tinctorium, a member of the toothed
fungi (Hydnaceee). The spores are borne on the outer surface
of the teeth on the under side of the fruiting-body. Infection
occurs when the spores lodge on the exposed wood of broken
branch stubs. For further details concerning the life history
and control of the wood-rotting fungi, see page 64.
REFERENCE
Meinecke, E. P. Forest tree diseases common in California and Ne-
vada. U.S. Dept. Agr. Forest Service. Unnumbered publica-
tion, pp. 1-67, pls. 1-24. 1914.
Brown Pocker HEartwoop-Rot
Caused by Fomes roseus Fries
The heartwood of fir is frequently destroyed by the brown
pocket-rot. This disease occurs also in juniper, larch, spruce,
pine and hemlock and occasionally in arbor-vite, beech and
maple. Long, cylindrical and pointed pockets of brown char-
coal-like decayed wood are formed. The fruiting-bodies of the
causal fungus are either thin and shelf-like or thick and hoof-
shaped. The under surface of the fruiting-body is rose-colored.
This heartwood-rot is more fully described under juniper dis-
eases, page 204.
FIR DISEASES 169
Brown Heartwoop-Ror
Caused by Fomes officinalis Fries (= Fomes laricis (Jacq.) Murrill)
Douglas fir is often severely damaged by this heartwood-rot
in the Northwest. Larch, pine and other conifers are affected
by the same disease throughout western United States. The
decayed wood re-
sembles the brown
checked wood-rot
caused by Poly-
porus sulphureus
(see page 247). In
the final stages of
decay, the heart-
wood is brownish
or red-brown.
Felts of mycelium
form in checks in
the brown wood
(Fig. 26). The
fruiting-bodies of
the causal fungus
are large hoof-
- shaped or globose,
with a rough
chalky upper surface. The inner substance of the sporophore
has a bitter taste. A more complete discussion of this heart-
wood-rot will be found under larch diseases, page 216.
Fig. 26.— Brown heartwood-rot of Douglas fir.
Brown Root- anv Burr-Ror
Caused by Fomes annosus Fries
This rot of the wood of the roots and lower part of the
trunk of fir is occasionally found in the forests of the North-
170 MANUAL OF TREE DISEASES
west. Pine, spruce and other conifers are also sometimes
affected wherever these trees grow. The wood is discolored
and changes from bluish to yellowish and finally becomes
red-brown. V/hite pockets with black centers appear in the
spring-wood of the rings. Later the pockets coalesce and the
brown summer-wood is left in separated sheets. The peren-
nial sporophores are shelving or resupinate and are found
attached to the diseased roots. The upper surface of the
shelving form is light brown and the under yellowish. For
further details concerning this root-disease, see under spruce
diseases on page 329.
Rep-Brown Root- anp Burt-Rot
Caused by Polyporus Schweinitzii Fries
This root-rot occurs also on pine, larch, spruce, hemlock and
arbor-vitee throughout the range of these trees. It is next in
importance to the pecky wood-rot of conifers caused by Tra-
metes pint. The heartwood of the roots and lower part of the
trunk becomes at first yellowish and cheesy and later is red-
brown and brittle, resembling charcoal in structure. This
wood-rot is more fully discussed under pine diseases, on page 294.
YELLOW Root-Rotr
Caused by Sparassis radicata Weir
This yellow or brownish root-rot of fir, spruce, pine and larch
has been recently described as common in northwestern United
States.. It seems to be equally as important in that region as
the shoe-string and brown root-rots, caused by Armillaria
mellea and Fomes annosus. The fungus causing the yellow rot
is peculiar in having a long perennial root-like attachment of
fungous mycelium which arises from the diseased roots. Other
species of the same group of fungi have been suspected of caus=")
FIR DISEASES 171
ing root-rots of various conifers and hardwood trees but have
never been accurately studied.
Symptoms.
Lateral roots are attacked even to considerable depths in the
soil. The mycelium from the point of infection spreads out
in the cambium and bark in yellowish fan-like plates. The
root is girdled and killed. The mycelium then penetrates the
sapwood, destroying first the medullary-rays. The affected
region 1s bordered by a reddish zone and at times by a jet-
black line. The heartwood at first is not penetrated because of
its highresin-content. Certain areas of heartwood are attacked,
however, and long pits formed by the complete destruction
of the tissues. At other times the inner layers of heartwood
may be largely destroyed, leaving a resinous layer of unaffected
wood between the decayed region and the sapwood. The
decayed heartwood is brownish or yellowish. Numerous
delicate brown strands of mycelium penetrate the wood where
openings have been formed. The cambium region is replaced
by a thick felt of mycelium.
The fruiting-bodies of the causal fungus are formed on the
surface of the ground. A long, fleshy, tuber-like body at-
tached to the diseased root pushes upward through the soil and
bears the upright fruiting-body on its tip. This fruiting-body
is a large, fleshy, compact, whitish, much branched structure,
often as much as ten inches across and equally as high. The
branches terminate as thin leaf-like but much crumpled plates
which stand upright or horizontally. The perennial tuber-
like attachment to the roots is often fifteen or more inches
long and a new fruiting-body is formed from its tip each year.
Cause.
The yellow root-rot of conifers is caused by the fungus
Sparassis radicata of the family Clavariacese. The spores are
72 MANUAL OF TREE DISEASES
borne over the surface of the leaf-like plates of the fruiting-
body. For further details concerning the life history and con-
trol of wood-rotting fungi, see page 64.
REFERENCE
Weir, J. R. Sparassis radicata, an undescribed fungus on the roots
of conifers. Phytopathology 7: 166-177, figs. 1-5. 1917.
CHAPTER XIX
HACKBERRY DISEASES
Two species of hackberry (Celtis) occur in eastern and central
United States. These trees are not important forest species
and in many sections they are shrub-like. West of the Missis-
sippi River, the hackberry is commonly used for shade and
ornament. The most important disease of this tree is the
witches’-broom. Several leaf-spot fungi and powdery mil-
dews are common on hackberry. Although no wood- or root-
rots have been recorded as affecting the hackberry, doubtless
some of the more common wood diseases of other deciduous
trees may also be found in them. The small amount of atten-
tion that has been given to the diseases of the hackberry is
due to its unimportance as a timber-tree.
Powpery MILDEWS
Caused by Uncinula parvula Cooke and Peck, and Uncinula polycheta
(Berk. and Curt.) ex Ellis
Besides the powdery mildew fungus which is associated with
the formation of the prominent knots and witches’-brooms,
two other species of the same group attack the leaves of the
hackberry. The one, Uncinula parvula, is reported through-
out the United States, while the other species, Uncinula
polycheta, is apparently confined to the southeastern states.
The former species causes inconspicuous powdery growths on
both sides of the leaf. The black fruiting-bodies are very
small and usually confined to the under surface of the leaf,
173
174 MANUAL OF TREE DISEASES
while in the latter species dense irregular white patches are
formed on the under sides of the leaves, and the black fruiting-
bodies are large in comparison with those of the former species.
The life histories and methods of control of powdery mildew
fungi are discussed on page 37.
WITcHEs’-BRooM
Caused by a gall-mite and Spherotheca phytoptophila Kellerman and
Swingle
The hackberry is affected, in central United States, by an
important witches’-broom disease. Although mainly impor-
tant because of the unsightly appearance of affected orna-
mentals, some damage to the tree must result from the loss of
energy spent in the development of the brooms. Also due to
the death of the branches or their breakage, wounds are formed
which allow wood-rot fungi to enter. The lower branches are
most commonly affected, although at times brooms are found
throughout the crown. Hundreds of brooms are sometimes
found on a single tree, causing serious deformation.
Symptoms.
Two general types of brooms are formed. The open type
consists of irregular swellings or knots at the base of a branch
from which many short stubby twigs arise. The leader remains
healthy, however, and grows to its normal length and other
knots with diseased laterals are formed on it at intervals. A
closed type of broom results when the leader is diseased and
fails to develop normally. For several years, after the first
knot with its diseased laterals is formed, the new laterals from
the base of those of the previous year cause a compact broom
of many deformed and dwarfed branches all arising from a
large irregular mass of gall-tissue. Smaller galls may be de-
veloped also further out on the diseased laterals.
HACKBERRY DISEASES 175
The first indication of the diseased condition can be detected
by examining the buds in the winter. Diseased buds are
found on wood one year or more old. They are larger in diame-
ter than healthy buds of the same length, grayish in color and
more open and hairy. When closely examined, it is seen that
the scales and inner bud-parts are distorted and enlarged,
causing the scales to stand open, exposing the inner parts.
Inside of the scales small mites are found. The mycelium of
the mildew fungus covers the outsides of the scales and the
small black fruiting-bodies of the mildew may be found within
the bud on the inner scales and young leaves. The buds of
the diseased laterals are more numerous than is normal and they
are usually all diseased. Many diseased buds are formed at
the bases of these laterals from which develop a new knot
with stubby dwarfed branches. The mycelium of the powdery
mildew fungus covers the buds and twigs early in the spring
and even at times is found on the under sides of the leaves of
diseased branches. This causes a whitish powdery appear-
ance of these parts.
Cause.
Two causal agents are always associated with the diseased
buds which develop the knots and broom-like growths. One
is a gall-mite, a species of Phytoptus, and the other a powdery
mildew fungus, Spherotheca phytoptophila. It has never
been definitely determined which of these two agents is the
more responsible in producing the abnormal growths. The
gall-mites are known to cause galls and warts of leaves and
twigs and in some instances other powdery mildews have been
found growing on the diseased areas produced by these insects.
Since, however, the mildew fungus is found growing over and
within the diseased buds and the fruiting-bodies are already
fully formed within the unopened buds, it seems reasonable to
believe that the fungus is present from the very initiation of
176 MANUAL OF TREE DISEASES
the diseased condition and may be jointly responsible for the
deformation. ‘Two such intimately associated agents, one an
insect and the other a fungus, are unusual and deserve more
careful study than has been given them. Practically nothing
is known concerning the life history of these two parasites and
their interrelations, more than has been discussed under symp-
toms. Both conidia and perithecia are formed by the mil-
dew fungus. The structure, life history and control of the
powdery mildew fungi are more fully discussed on page 34.
In the case of this disease, control measures seemingly would
be confined to cutting out the diseased twigs and brooms.
Spraying or dusting could not be expected to yield satisfactory
results.
REFERENCES
Kellerman, W. A., and Swingle, W. T. Branch knot of the hackberry.
In Report of the Botanical Department. Kansas Agr. Exp. Sta.
Ann. Rept. 1: 302-315, pls. 4-6. 1889.
Halsted, B. D. Notes upon Spherotheca phytoptophila Kell. and
Swingle. Jour. Mycology 5: 85-86. 1889.
Salmon, E. 8S. Sphewrotheeca phytoptophila Kellerm. and Swingle.
In A monograph of the Erysiphacee. Mem. Torrey Bot. Club.
9: 76-79. 1900.
CHAPTER XX
HEMLOCK DISEASES
Four species of hemlock or Tsuga occur in the forests of the
United States. The two eastern hemlocks are important trees,
especially in the northeastern states. The western species are
confined to the northwestern states and are large trees. All
four species are frequently used as ornamentals.
Although several fungous diseases are occasionally found on
hemlock, it is less severely affected in general than pine, spruce
and fir. In the Northwest, the young trees are killed by a
root-rot and the older ones are often affected by the stringy
red-brown heartwood-rot. In the East, the leaf-blight, rusts
and wood-rots cause but little damage.
SEEDLING Root-Ror
Caused by Rhizina undulata Fries
The roots of three- to five-year-old seedlings of species of
hemlock, pine, larch and fir are frequently attacked in the
forests of the Northwest by Rhizina undulata. The fungus
has been found in several eastern states attached to roots of
conifers but its connection with any root disease is not definitely
established. The same disease is common in Europe on seed-
lings of various conifers and has been known for many years.
Symptoms.
The fruiting-bodies of the fungus are formed annually and
grow on the surface of the ground. They are variable in size,
measuring often two or three inches across, irregular in shape,
N 177
178 MANUAL OF TREE DISEASES
with an undulating, rich brown upper surface bordered at the
margin by a narrow white zone (Fig. 27). In wet weather the
upper surface becomes mucilaginous. The under surface is
more or less fused with the soil. Long white strands of my-
celium, arising from the under surface, can be traced to diseased
roots. Affected seedlings growing in nursery-beds or in the
forest are killed in isolated groups. On pulling the trees, the
roots are found to be closely matted with white mycelium.
This characteristic, together with the soil being held together
by the matted mycelium and the roots being more or less
resinous, make this root disease practically indistinguishable
Fig. 27.— Fruiting-bodies of Rhizina undulata.
from the common shoe-string root-rot caused by Armillaria
mellea. This latter fungus is common as a root-rotting fungus
of both conifers and deciduous trees and sometimes attacks
young seedlings (see page 78). Often, however, the fruiting-
bodies of the Rhizina occur plentifully around and envelop we
stems of affected seedlings.
Cause.
The pathogene causing this seedling root-rot is an ascomy-
cetous fungus which forms spores in closely packed asci. These
stand upright and form the brown upper surface of the fruiting-
body. The spores are forcibly shot upward into the air and are
blown away. Falling on the ground, they germinate and the
abundant white mycelium that is formed penetrates the root-
tissues and causes the seedling to die.
HEMLOCK DISEASES 179
Control.
No specific measures of control have been tried, so far as
known. The control measures given on page 81 for the shoe-
string root-rot may be applied to this disease as well.
REFERENCES
Weir, J. R. Observations on Rhizina inflata. Jour. Agr. Res. 4:
93-95, pl. 8. 1915.
Hartig, R. Rhizina undulata Fr. the root fungus. Jn Text-book
of the diseases of trees, pp. 123-129, figs. 61-70. 1894.
LeAF-BLIGHT
Caused by Keithia tsuge (Farlow) Durand
The leaves of the eastern hemlock are at times killed by this
leaf-blight. Instances are reported in which several trees
were almost defoliated. This disease is definitely reported
only from New Hampshire, Massachusetts and Wisconsin.
It may, however, be found at other places in the range of the
hemlock. The leaves that are affected turn brown and fall from
the twigs. These symptoms occur in the late summer. The
fruiting-bodies of the pathogene form during the summer on the
affected leaves. They appear as small black pustules bursting
through the leaf-epidermis. Ascospores are forcibly ejected
from these fruiting-bodies during moist weather. Additional
facts concerning the life history of this fungus will be found
on page 90, where a similar disease of western arbor-vit is
discussed.
REFERENCES
Durand, E.J. The genus Keithia. Mycologia 6: 6-11, pl. 81. 1913.
Farlow, W.G. Notes on the cryptogamic flora of the White mountains.
Appalachia 3 : 245-246. 1883.
Spaulding, P. Diseases of the eastern hemlock. Proce. Soe. Amer.
Foresters 9: 245-256. 1914.
180 MANUAL OF TREE DISEASES
Brown-Mo.up L&AF-BLIGHT
Caused by Rosellinia sp. ?
The importance and prevalence of this disease of hemlock
is so far not known. It has been found in North Carolina.
The needles of the lower branches become yellow. The af-
fected twigs show a growth of yellowish-brown or grayish
mycelium covering the bark and investing the bases of the
yellow needles. The dead needles either fall off or are held
by the tangle of mycelium. Small dome-shaped fruiting-
bodies of the fungus are found slightly sunken in the mycelium.
Although not definitely determined, this fungus apparently
belongs to the genus Rosellinia. It has not yet been definitely
established that the brown mycelium is directly responsible
for the diseased condition.
REFERENCE
Graves, A. H. Notes on the diseases of trees in the southern Appa-
lachians III. Phytopathology 4: 63-72, pl. 5, fig. 1-10. 1914.
LEAF AND CoNneE BLIstTER-Rvusts
Caused by Pucciniastrum minimum (Sehw.) Arthur, and P. myrtilli
(Schum.) Arthur
Two species of the blister-rust fungi attack the green parts
of the eastern and Carolina hemlock. These rusts are very
similar in appearance and have been found in widely separated
localities throughout the range of the two eastern hemlocks.
The leaves and cones may be at times so heavily infected
that the leaves fall and the cones fail to mature viable seeds.
This happens only in the case of individual trees which stand
close to the alternate host plants which these fungi require for
the completion of their life history.
F
HEMLOCK DISEASES 181
Symptoms.
Although these two species of fungi differ sufficiently so
they can be recognized by their microscopical characters, the
general appearance of fruiting-structures and the effect on
the tree is very similar. The leaves of young trees or of
the lower limbs of older trees are much oftener affected than
the tops of older trees. Sometimes one-half of the cones
may be affected. The most conspicuous symptom of these
diseases is the production, on the leaves or cones of golden-
yellow or reddish colored blisters in June and July. These
blisters burst through the epidermis of the affected parts and
when abundant their color stands out prominently against the
dark green of the healthy foliage. The spores borne in the
blisters sift out as a fine powder and are blown away by the
wind.
Cause.
Two species of the rust-fungi are known to cause the blister-
rust of the leaves and cones of hemlock. The life history
of these species varies slightly in that different kinds of
shrubs are required for their further development.
The first species mentioned, Pucciniastrum minimum, occurs
on the leaves and cones. This fungus was known on
the hemlock previously as Peridermiwm Peckii Thiimen.
The spores from the blisters on the leaves cause the in-
fection of the leaves of species of Rhododendron. On
this host plant, very small yellowish spots are developed on
the under sides of the leaves. The spores produced in early
spring on the rhododendron leaves infect the newly developed
leaves and cones of the hemlock.
The second species, Pucciniastrum myrtilli, is known to occur
only on the leaves. This fungus was also previously known as
Peridermium Peckii. The blisters on the hemlock leaves
are more reddish than those of the other species. The
182 MANUAL OF TREE DISEASES
spores from the blisters infect the leaves of species of blue-
berry. On this host plant are formed small yellowish spots
on the under sides of the leaves. Later light brown spots
appear in the same areas. The spores produced the following
spring from the brown spots cause the infection of the young
hemlock leaves.
Control.
By keeping rhododendrons and blueberry bushes away from
hemlock trees, these blister-rusts can be prevented. The
heaviest infection of the hemlock occurs when one of these
alternate host plants stands within a few feet.
REFERENCE
Spaulding, P. Diseases of the eastern hemlock. Proce. Soe. Amer. For-
esters 9: 245-256. 1914. (Bibliography given.)
Lear-, Cone- AND Twic-Rusts
Caused by Melampsora abietis-canadensis (Farl.) Ludwig, and Neciwm
Farlowit Arthur
In addition to the two blister-rusts of hemlock (page 180)
two other rust-diseases occur on these trees. In Nova Scotia
instances have been noted in which the leaves and twigs of
the entire top of the tree were killed by the later fungus.
Symptoms.
The first species, M. abietis-canadensis, causes a rust on the
leaves, cones and twigs similar in appearance to the blister-
rusts. This fungus was known on the hemlock previously
as Caoma abietis-canadensis on the leaves and as Peri-
dermium fructigenum on the cones. The spores from the
pustules produced in early summer on the affected parts
of the hemlock cause the infection of the leaves of the large-
tooth aspen. On this second host small orange or brown-
HEMLOCK DISEASES 183
ish spots are produced on the leaves. Later reddish brown
pustules are formed (see page 298). Spores formed on the
dead aspen leaves the following spring, when blown to the
hemlock, cause the infection of the young green parts.
The leaves and twigs affected by the second species, Necium
Farlowii, may die in midsummer, the leaves falling off. When
defoliation does not take place, the infected leaves and twigs
bear reddish, swollen, velvety pustules in early spring. The
cones may show the same reddish bodies.
Cause.
These rust-fungi are close relatives of the hemlock blister-
rusts. The first species produces eciospores in open pustules
which do not have a bladdery covering, as in the blister-rusts.
The second species does not produce sciospores but forms
teliospores as its only spore-stage. These over-winter and
burst the epidermis, producing reddish waxy pustules in the
spring. The basidiospores produced by the germination of
the teliospores reinfect the young green parts of the hemlock.
Thus this rust-fungus requires no alternate host and occurs
only on the hemlock.
Control.
The rust having its alternate stage on poplar leaves may
be controlled by keeping poplars separated from hemlocks by
a few hundred feet. In the case of the second fungus, which
occurs only on hemlock, the affected twigs should be pruned off
in the winter and burned, thus destroying the spores of the
fungus and preventing further infection.
REFERENCE
Ludwig, C.A. Notes on some North American rusts with Czoma-like
sori. Phytopathology 5: 273-281. 1915.
184 MANUAL OF TREE DISEASES
ReEpb-Brown Sapwoop-Ror
Caused by Fomes pinicola Fries
Hemlock is sometimes affected by this sapwood-rot. It
occurs also in spruce, pine, fir and larch. Coniferous wood of
all kinds is destroyed by the fungus causing this rot, and the
sporophores are very abundant on fallen logs and dead stand-
ing trees. The wood is reduced to a red-brown powdery mass
held together by numerous plates of mycelium. The sporo-
phores have a red varnished margin and a cream-colored under
surface. Further details concerning this wood-rot will be
found under fir diseases, page 165.
Strincy Rep-Brown HEArRtTWoop-Rot
Caused by Echinodontium tinctorium Ellis and Everhart
The western hemlock is destructively affected by this heart-
wood-rot. Firs and spruce are also commonly decayed by the
same fungus. In the first stage of decay, the wood is discolored
and spongy. The wood then becomes red-brown and the
spring-wood of the annual ring is dissolved, leaving the summer-
wood in separated cylinders one inside of the other. Later
these sheets of summer-wood are destroyed and the tree be-
comes hollow. For further details concerning this heartwood-
rot, see under fir diseases, page 166.
Brown Pocket HEARTWOOD-RoT
Caused by Fomes roseus Fries
The eastern and western hemlock are sometimes affected
by this heartwood-rot, which is also found in juniper, fir, larch,
spruce, pine and occasionally in arbor-vite. It occurs prac-
tically throughout the entire country wherever conifers are
important forest-trees. Long, cylindrical and pointed pockets
HEMLOCK DISEASES 185
of brown charcoal-like rotted wood are formed in the heart-
wood. The fruiting-bodies of the causal fungus vary from small
thin shelves to larger hoof-shaped bodies. The upper surface
is black in the older fruiting-bodies, while the new layer of
tubes on the under surface. is rose-colored. For further details
concerning this heartwood-rot, see under juniper diseases,
page 204. The fungus continues to grow in fallen trees and
the fruiting-bodies are more commonly found on dead wood
than on living individuals. The sapwood is also decayed in
dead trees and logs.
CusoiwAL Woop-Rot
Caused by Polyporus borealis Fries
This heartwood-rot does not seem to occur abundantly,
since but little mention of it is found in literature. It is re-
ported in New York but no definite statements on its importance
and range are available. Red spruce is also known to be
affected by this wood-rot.
Symptoms.
In the early stages of the decay, long parallel strands or cords
of white mycelium, lying close together, push their way through
the wood in the radial and tangential directions. The white
strands then disappear, leaving channels in the wood. Because
of these perforations and the shrinkage of the wood, it breaks
into minute cubes. On the border of the affected wood, the
mycelium reaches out into the normal wood in very fine strands.
These then develop into the thicker white cords described
above (Fig. 28).
The fruiting-bodies are formed on the trunk or at the base
of the tree. Usually several shelf-like bodies one above the
other occur together, forming a cluster. The upper surfaces
of the shelves are white and shaggy. The under surfaces are
186 MANUAL OF TREE DISEASES
covered with small roundish or sinuous openings. The entire
fruiting-body is white or yellowish and soft and spongy.
Cause.
The cuboidal wood-rot of hemlock and spruce is caused
by the fungus, Polyporus borealis. The spores from the tubes
opening on the under side of the fruiting-body are blown about
by the wind. Infection takes place at wounds. The heart-
Fig. 28.— Cuboidal wood-rot of hemlock.
wood may be affected from the top to the base of the tree.
The sapwood is decayed and the smaller limbs killed at the top
of the tree. For further details concerning the life history and
control of wood-rotting fungi, see page 64.
REFERENCES
Atkinson, G. F. Polyporus borealis. In Studies of some shade tree
and timber destroying fungi. Cornell Univ. Agr. Exp. Sta. Bul.
193 : 202-208, figs. 56-63. 1901.
Hartig, R. Polyporus borealis Fr. In Die Zersetzungserscheinungen
des Holzes ete., pp. 54-58, pl. 10. 1878.
HEMLOCK DISEASES 187
Rep-Brown Root- anp Butt-Ror
Caused by Polyporus Schweinitzii Fries
In addition to hemlock, this root- and butt-rot occurs in
fir, pine, larch, spruce and arbor-vite. It is a destructive
root-disease of these trees throughout their range. The affected
wood is first yellowish and cheesy, later changing to a red-
brown, uniform rot. The completely decayed wood is brittle,
and is similar in appearance to charcoal. For a more complete
description of this disease, see page 294.
CHAPTER XXI
HICKORY DISEASES
SEVERAL species of hickory (Carya or Hicoria) occur as com-
mon trees in eastern United States. Several fungi cause leaf-
spots of hickory (page 30). Besides these, the leaf-mildew,
witches’-broom and common white wood-rot are the only dis-
eases of importance of these trees. Although these diseases —
and probably others are common on hickory practically no
mention of them is made in literature.
Lear-MILpEw AND WitcHES’-BROOoM
Caused by Microstroma juglandis (Bereng.) Sace.
The leaves of hickory and walnut in eastern United States are
often affected by this disease. Early in the summer the leaflets
show a white powdery mildew on the under side. The invaded
area of the leaflet is yellowish and defoliation may result. Re-
cently the formation of witches’-brooms on shag-bark hickory
has been shown to be another symptom of this disease. Brooms
are sometimes numerous on the trees and are as much as a yard
across. The leaves which appear on the brooms in the spring
are yellowish green above and covered with the white powdery
growth of the fungus below. The leaflets are smaller than nor-
mal and curled. They fall prematurely and leave the brooms
bare in midsummer. The fungus causing this disease is sup-
posed to be a simple basidiomycete forming numerous short
stalks bearing spores on the under sides of the leaf.
188
HICKORY DISEASES 189
REFERENCE ON LEAF-MILDEW AND WITCHES’-BROOM
Stewart, F. C. Witches-brooms on hickory trees. Phytopathology
7: 185-187, fig. 1. 1917.
Common WuitE Woop-Ror
Caused by Fomes igniarius Fries
The heartwood of hickory is sometimes reduced to a white
soft punk by the false-tinder fungus. This rot is more common
and destructive to beech, poplar, oak and maple. The sporo-
phores and appearance of the white rotted wood are described
under poplar diseases, page 305.
CHAPTER XXII
JUNIPER DISEASES
SEVERAL species of juniper (Juniperus) occur as important
forest-trees over the entire United States. These trees and the
horticultural varieties of the native and exotic species are the
most common conifers used for ornament. In the genus
Juniperus are included the low junipers.
The juniper is subject to several important wood-rots and
rust-diseases. Several destructive heartwood-rots of juni-
per are especially common in the Southwest. The rust-
diseases of juniper are important both from the economic
and ornamental standpoint. Many of the rust-fungi be-
longing to the genus Gymnosporangium grow parasiti-
cally in the leaves, branches or trunk of juniper. Several
types of over-growth occur in the affected tissues. These
diseases are interesting because of the complicated life history
of the different species requiring various other plants as alter-
nate hosts. As certain of these fungi cause the rust-diseases of
apple, pear and quince, their control is an orchard as well as an
ornamental tree problem.
SEEDLING Twi1G-BLIGHT
Caused by Phoma sp.
Junipers grown in nursery-beds are subject to a twig-blight
which has been destructive in certain seasons in Kansas, Ne-
braska, Iowa, Illinois and Pennsylvania and may be expected
in other localities. By artificial inoculation with the causal
190
JUNIPER DISEASES 191
fungus, the same disease has been found to affect several
species of juniper, arbor-vite and cedar. Wet seasons are
conducive to epiphytotics of this disease, but it seems never
to affect trees more than three or four years old.
Symptoms.
This twig-blight may appear at any time and continue to
spread throughout the growing season on nursery stock less
than four years old. When severe, entire beds of stock may be
destroyed. The general appearance of the trees is not unlike
that produced by sun-scorch, except that the trees of a given
bed are not affected uniformly but die in spots, which are ir-
regular in outline and gradually increase in size. The small
lateral branches are affected first and soon are killed. The
mycelium then extends its growth into the main stem and
spreads more rapidly upward than downward. Other lateral
twigs may thus become affected and killed before the main stem
is girdled. Recently killed laterals show bleached lesions of a
purplish or grayish cast at the base where they branch from the
main stem. When the main stem is affected and it is cut length-
wise witha knife, the cambium and wood are seen to be discolored.
Girdling is sometimes not accomplished and the long sunken
cankers heal over, leaving a flattened stem. ‘The terminal is
often killed directly by the mycelium spreading upward into it
before girdling has taken place. Minute black fruiting-bodies
break through the epidermis of the leaves and bark even before
any outward discoloration is apparent. In moist weather,
prominent hair-like twisted tendrils composed of hundreds of
the spores of the fungus are pushed out from these fruiting-
bodies.
Cause.
The twig-blight of seedling junipers and other conifers is
caused by a fungus of the genus Phoma. Only the one type of
192 MANUAL OF TREE DISEASES
fruiting-stage, as described under symptoms, is known. Spores
are produced in abundance from the fruiting-bodies (pyenidia)
during wet weather and may be washed or spattered by rain to
neighboring trees. The first infections take place in the lateral
twigs, which are quickly killed. The mycelium then spreads
into the main stem and proceeds upward, killing the outer wood-
tissues and cambium on one side of the tree and running out
into other laterals.
Control.
Experiments so far tried in spraying with lime-sulfur and bor-
deaux mixture for the control of this disease have not been suc-
cessful. The period of infection extending throughout the grow-
ing-season and the nature of the scale-like leaves and the twigs
preclude much hope of good results from spraying. Careful
eradication of all diseased and neighboring trees may, to some
extent, reduce losses by stopping the enlargement of the spots
in the beds.
REFERENCE
Hahn, G. G., Hartley, Carl, and Pierce, R. G. A nursery blight of
eedars. Jour. Agr. Res. 10: 533-539, pls. 60-61. 1917.
LEAF- AND STEM-Rusts (GENERAL)
Caused by species of Gymnosporangium
Several species of the rust-fungi belonging to the genus Gym-
nosporangium cause more or less important diseases of juniper
and cedar. These fungi are strictly parasitic and never grow
except in the living tissue of some plant. They are, therefore,
confined to the range of the species of juniper and cedar, which
are found in the north temperate zone in North America,
Europe, Asia and northern Africa. Another important pe-
culiarity of these fungi which further restricts the range of each
species is that they each require certain kinds of broad-leaf trees
JUNIPER DISEASES 193
and shrubs as alternate hosts. Unless the necessary alternate
host is present in close proximity to the juniper or cedar, the
rust cannot exist, since the life history of the fungus cannot be
completed. Trees and shrubs of the order Rosales, family
Pomacee, are the most common alternate hosts of these fungi.
The life history of all the Gymnosporangium rusts is similar
and is described here to avoid repetition below. As stated, these
fungi are parasitic throughout their life. They live for a time
on a certain species of juniper or cedar and produce spores
(basidiospores) which can only cause infection of the leaf, twig
or fruit of a certain few or perhaps only a single species of the
wild or cultivated apple-like trees, such as apple, pear, quince,
haw, mountain ash and service-berry. Here the fungus lives
only for a short time and produces spores (seciospores) which
do not reinfect other trees of the same kind but can only infect
the required juniper or cedar. Thus it is seen that the spores
produced on each of the two kinds of hosts are innocuous to the
same host and must find lodgment on trees of the other type in
order to continue the life history.
These rust-fungi over-winter as mycelium in the juniper or
cedar leaves or stems. The next season after infection occurs,
most of these fungi cause some type of over-growth of the tissues.
Such abnormalities are brought about as long swellings or glo-
bose galls on the stems, witches’-brooms and leaves transformed
into brown globose growths known as cedar-apples. A few of
the species cause no abnormal growth and are evident only by
the fruiting-structures. The fungi form spores (teliospores) in
the early spring on masses of mycelium pushed out from the bark
of the twig or epidermis of the leaf. These spore-masses may
be in the form of cushions or ridges in the crevices of affected
bark or, in the case of the cedar-apples, they consist of long
horn-like projections, sometimes an inch or more in length.
They appear at first dark brown, due to the color of the telio-
spores on the surface. In wet weather the spore-masses become
Co)
194 MANUAL OF TREE DISEASES
jelly-like and the individual spores germinate, each producing
several secondary spores (basidiospores) which are shot off into
the air. These spores are carried away by the wind and may
find lodgment on the leaves, twigs or fruit of the proper alternate
host. Under favorable conditions of moisture, the basidiospores
germinate and the tissue of the pomaceous host is penetrated
and a new growth of mycelium started. The area of tissue
invaded is limited
to a small spot
which becomes
somewhat swollen
and light yellow in
color (Fig. 29). A
short time after
these symptoms
become apparent,
long whitish tubes
of fungous tissue
are pushed out all
over the affected
areas (Fig. 30).
These tubes some-
times split and
form a fringe
around cup-like depressions in the leaf, twig or fruit, in which
are formed powdery masses of yellow spores (sciospores).
These dust out, are borne by the wind and may continue the
life history of the fungus if they lodge on the leaves or twigs
of the proper species of juniper or cedar.
These rust-fungi are important because they deform the tree
when galls, witches’-brooms or cedar-apples are formed in abun-
dance. The tissues of the affected branches die eventually and
leave dead areas where wood-rot fungi may enter. On the
apple-like hosts, which include not only many important cul-
Fic. 29.— Cedar-apple fungus on wild apple leaves.
JUNIPER DISEASES 195
tivated fruits but also many valued ornamentals, much damage
is caused by defoliation when infection is heavy.
Control.
The control of these fungi is simple if one or the other of the
alternate hosts is eliminated. Although cases have been noted
in which a sepa-
ration of one to
several miles did
not totally pre-
vent the exchange
of spores, a dis-
tance of one mile
between the two
required kinds of
trees reduces the
amount of infec-
tion to a mini-
mum. Spraying
either the conifer
or pomaceous
host has not been
successful. In
some states where
junipers are a
menace to or-
chards because of
the rusts, laws are
in force requiring the destruction of all specimens within
one mile of orchards.
Fic. 30.— Cedar-apple fungus on haw leaf.
REFERENCE
Kern, Frank Dunn. A biologic and taxonomic study of the genus
Gymnosporanguim. Bul. N. Y. Bot. Gard. 7: 391-483, pls. 151-
161, figs. 1-36. 1911,
196 MANUAL OF TREE DISEASES
LEAF- AND Twic-Rusts
Caused by species of Gymnosporangium
A few species of the rust-fungi belonging to the genus Gym-
nosporangium attack the green twigs and leaves of various jJuni-
pers without causing any over-growth of the affected parts.
The symptoms of these diseases are confined to the brown spore-
masses developed either on the leaf or between the leaves. The
life history of these forms is similar to the other species of the
same genus and is discussed on page 192. Below are given the
hosts and characteristics, in brief, of these diseases.
In Colorado, Utah and New Mexico, the Utah juniper is at-
tacked by G. inconspicuum Kern. A yellowing of the leaves
on the affected twigs may be noticed and in early spring small
brown cushion-like spore-masses, the size of a pin-head, are
formed from between and around the margins of the appressed
scale-like leaves. The alternate stage occurs on species of
service-berry.
In Colorado a similar appearing species, G. multiporum Kern,
attacks the Utah and one-seed juniper. The alternate hosts
are not known.
In Texas several species of juniper are attacked by G. exiguum
Kern. Short brown conical spore-masses, a sixteenth of an inch
long, are pushed out from the affected leaves. The alternate
host is Crategus Tracyt.
In northeastern and north central United States, Juniperus
sibirica is attacked by G. Davisii Kern. Spore-masses appear
as small brown pustules on the leaves or at the base of leaves on
the twig. The alternate stage occurs on species of mountain ash.
A foreign species, G. koreaense (P. Henn.) Jackson, recently
has been found established in Oregon on an imported juniper,
Juniperus chinensis. Spore-masses form on the leaves of the
juniper. The alternate stage occurs on cultivated quince and
introduced Asiatic species of quince and pear.
JUNIPER DISEASES 197
CEDAR-APPLES
Caused by Gymnosporangium juniperi-virginiane Schw. and
G. globosum Farlow
The two diseases of the red
juniper known as cedar-apples or
cedar-flowers are similar in nature
and are found commonly in eastern
and central United States. The
first pathogene mentioned above
has its alternate stage on the culti-
vated apple and other species of
Malus, while the latter pathogene
occurs on various species of haw,
mountain ash and the cultivated
Fig. 31.— Cedar-apples, early
apple, and pear. The junipers EBSD Oa oute Shes a0:
are often covered with hundreds of the brown, globose galls
Fic. 32.— Cedar-apple in late
autumn, one year after infection.
which spoil the appearance of
ornamental trees and result in
more or less damage to the twigs
and general vigor of the tree. The
two pathogenes are the cause of ap-
ple and pear rust respectively and
cause serious losses in yield when
they cause defoliation. Climatic
conditions and the proximity and
abundance of the two kinds of hosts
In the same locality are the deter-
mining factors which influence the
severity of these diseases on both
hosts.
Symptoms.
Brown-colored bodies called
cedar-apples or cedar-flowers are
198 MANUAL OF TREE DISEASES
produced on the small twigs of the red juniper. When very
young, the galls can be seen to start as outgrowths of the juniper
leaves (Fig. 31). The tissues of the leaf are stimulated to over-
growth and finally form, in a single season, the large cedar-
apples, which are often an inch in diameter (Fig. 32). In this
Fig. 33.— Cedar-apple in spring of second year,
showing expanded spore-horns.
condition they pass the winter, and the following spring brown
horns of spores are pushed out from the surface of the cedar-
apples (Fig. 33). In the former species these horns are about
one inch long and cylindrical, while in the latter fungus they —
are about one-half inch long and are flattened or wedge-shaped.
JUNIPER DISEASES 199
Cause.
Cedar-apples on juniper are caused by two different species
of the rust-fungi, Gymnosporangium juniperi-virginiane and
G. globosum. ‘The life history of these fungi is described on page
192 in the general discussion of several species of the same genus.
In the case of the two cedar-apple rusts, the leaves of the juniper
are infected by eciospores formed on the apple, pear, haw or
other pomaceous host. This takes place during midsummer or
in the fall and no symptoms on the juniper are apparent until
late spring of the next season. At that time the infected leaf
shows a small greenish outgrowth, and in the summer from this
small beginning the large cedar-apple develops (Fig. 32). The
tissue inside the gall is made up of a mixture of large host-cells
and intercellular mycelium. The outer layers of the gall are
eorky and reddish or chocolate-brown. Scattered over the sur-
face, in late autumn, are numerous depressions from each of
which a bundle of hyphe grow out the following spring and
form the horns covered with teliospores.
REFERENCES
Hesler, L. R., and Whetzel, H. H. Manual of fruit diseases, pp. 63-
71, 341-344, figs. 17-19, 94. 1917.
Weimer, J. L. Three cedar rust fungi, their life histories and the
diseases they produce. Cornell Univ. Agr. Exp. Sta. Bul. 390:
507-549, figs. 136-157. 1917.
Heald, F. D. The life history of the cedar rust fungus Gymno-
sporangium Juniperi-virginiane Schw. Nebraska Agr. Exp. Sta.
Ann. Rept. 22: 105-113, pls. 1-18. 1909.
Reed, H.S., and Crabill,C. H. The cedar rust disease of apples caused
by Gymnosporangium Juniperi-virginiane Schw. Virginia Agr.
Exp. Sta. Tech. Bul. 9: 3-106, figs. 1-23. 1915.
Giddings, N. J., and Berg, A. Apple rust. West Virginia Agr. Exp.
Stas Bull 154275—73, piss 1-10) £95:
Coons, G. H. Some investigations of the cedar rust fungus. Nebraska
Agr. Exp. Sta. Ann. Rept. 25: 217-246. 1912.
Pammel, L. H. The cedar apple fungi and apple rust in lowa. Iowa
Agr. Exp. Sta. Bul. 84: 1-386, figs. 1-11. 1905.
200 MANUAL OF TREE DISEASES
Rust WircHes’-Brooms
Caused by Gymnosporangium Nidus-avis Thaxter, G. jwvenescens Kern
and G. Kernianum Bethel
Three witches’-broom diseases are caused by species of
rust-fungi on different junipers. The first species mentioned
above causes witches’-brooms of the red juniper in eastern and
central United States. The brooms are simply tufts of many
branches which are formed from the part of the parent branch
affected by the rust-fungus. The leaves of the brooms are usu-
ally of the pointed, awl-shaped, juvenile type. The second
species causes large brooms on the red and Rocky Mountain
juniper in the Rocky Mountains and in northwestern and north
central United States. The leaves of these brooms also are of
the juvenile type. The third species causes globose, compact
brooms on the Utah juniper in western Colorado. The leaves
on the brooms on this tree are scale-like.
The life history of all three species is similar to the other rusts
of this type occurring on junipers and is discussed on page 192.
The spore-masses in the first species appear as linear cushion-like
brown masses bursting the bark of the affected branches, while
in the other two species they are small hemispherical brown
bodies, the size of a pin-head or smaller and arise from between
the leaves or in the leaf-axils. Various species of service-berry
are the alternate hosts for these three species. The first species
is known to infect the quince also.
BRANCH-GALLS
Caused by several species of Gymnosporangium
Abrupt swellings of the stems of the various species of juniper
are often caused by species of the rust-fungi belonging to the
genus Gymnosporangium. Other species of the same group of
rusts cause cedar-apples and long fusiform “branch-swellings,
JUNIPER DISEASES 201
and a few produce spore-cushions on the normal green twigs and
scale-like leaves. ‘The life history of these fungi is described on
page 192. The main characteristics of the forms causing abrupt
swellings are given below.
The red juniper is affected in southeastern and south central
United States by Gymnosporangium trachysorum Kern. Small
knots or galls as large as an inch in diameter and an inch and a
half long are formed on the small branches. The spore-horns are
pushed out from these galls and are wedge-shaped and less than
a half inch long. The alternate stage occurs on species of haw.
In the same region the red juniper is attacked by Gymnospo-
rangium floriforme Thaxter. Small gall-like excrescences as
large as one-half inch across and occasionally globose swellings
an inch in diameter are formed on the branches. The horns of
spores are cylindrical and pointed and vary from an eighth to
one-half inch in length. One species of haw (Crategus spathu-
lata) is known to be the alternate host for this rust.
Along the coast of the Gulf of Mexico from Mississippi to
Florida, several species of juniper often show reddish brown
globose galls, a quarter to one-half inch in diameter. The fungus
causing this gall is Gymnosporangium bermudianum (Farlow)
Earle. This species is peculiar and is different from all others
of this group in that no alternate host is required for its develop-
ment. Both the teliospores and eciospores are formed on the
same galls on the juniper. The cluster-cup stage is followed
by teliospore masses smaller than a pin-head.
In northwestern United States and adjacent Canada, the
dwarf juniper and Juniperus sibirica are attacked by Gymnospo-
rangium juniperinum (L.) Mart. Hemispherical swellings half
an inch to two inches long are formed on the larger branches
and more or less globose galls an inch in diameter appear on
the smaller branches. The spore-masses are flat and cover large
areas of the galls. The alternate hosts are species of mountain
ash.
202 MANUAL OF TREE DISEASES
In the same region as above, the Rocky Mountain juniper is
attacked by Gymnosporangium Bethel: Ikern. Irregular gall-
like knots are produced which are two or three times the
diameter of the normal branch. Several knots breaking out ad-
jacent to each other form galls similar to the black knots com-
mon on plum and cherry. Short wedge-shaped spore-horns
about an eighth of an inch long are pushed out from the bark of
the galls. Several species of haw are known to be the alternate
hosts for this rust.
In northwestern and southwestern United States, the Rocky »
Mountain, Utah and one-seed junipers are attacked by Gym-
nosporangium Nelsoni Arthur. Hard woody globose galls as
large as two and one-half inches are formed. ‘The spore-masses
are flattened and about an eighth of an inch high. ‘The alter-
nate hosts of this species are the quince, pear and species of
service-berry.
The red juniper in northeastern and north central United
States is attacked by Gymnosporangium corniculans Kern.
Irregularly lobed excrescences as large as an inch in diameter
are produced. The spore-horns are conical and about one-
eighth of an inch high. The alternate hosts are species of serv-
ice-berry.
FustrorM BRANCH-SWELLINGS
Caused by species of Gymnosporangium
In addition to cedar-apples and galls or knots, several species
of the rust-fungi cause long spindle-shaped swellings of the
branches of species of juniper. The life history of these fungi
is discussed on page 192 and only the hosts and outstanding
characteristics of the diseases are given below.
In eastern, southeastern and central United States, the red
and dwarf juniper and J. sibirica are commonly affected by
Gymnosporangium germinale (Schw.) Kern. The branches are
slightly enlarged, often for several inches in length. The spore-
JUNIPER DISEASES 203
masses break through the bark as orange-yellow hemispherical
pustules about an eighth of an inch high. The alternate hosts
are quince, apple and species of service-berry and haw.
In northeastern United States and westward to Wyoming and
Colorado, the dwarf juniper, and Juniperus sibirica are affected
by Gymnosporangium clavarieforme (Jacq.) DC. The branches
of all sizes are attacked and slightly swollen for several inches.
Spore-horns are produced in abundance in the spring from
the swellings. They are brownish yellow and about one-half
inch long. The alternate stage of this rust is produced on
quince and species of service-berry.
Along the Atlantic Coast the red juniper is attacked by Gym-
nosporangium effusum Kern. Long slender enlargements of
the smaller branches less than an inch in diameter are pro-
duced. This fungus also causes swellings on the trunks.
The spore-masses are wedge-shaped and often as large as one-
half inch high by a quarter of an inch long at the base. The
alternate host for this species is unknown.
Several species of juniper in Colorado, New Mexico and Ari-
zona are attacked by Gymnosporangium gracilens (Peck) Kern
and Bethel. Long spindle-shaped swellings of the branches are
formed. The spore-masses break through the bark in long rows
and are about an eighth of an inch high. Species of Fendlera
and Philadelphus are alternate hosts of this rust.
In the region extending from northeastern United States to
Colorado and Wyoming, the red juniper and Juniperus sibirica
are attacked by Gymnosporangium cornutum (Pers.) Arthur.
The smaller woody branches are slightly enlarged. ‘The spore-
masses are flat or cushion-like and not extensive. Mountain
ash is the alternate host.
In a restricted region in Kentucky and Missouri, the red
juniper is attacked by Gymnosporangium exteruwm Arthur and
Kern. Short spindle-shaped swellings are produced and the spore-
masses in the spring are flat and anastomosing. ‘The alternate
204 MANUAL OF TREE DISEASES
host for this species is Porteranthus (Gillenia) stipulatus (Muhl.)
Britton.
Waitt Bark
Caused by Cyanospora albicedre Heald and Wolf
This disease is common on the mountain juniper throughout
its range in Texas. White patches, either small or extensive,
occur on the bark of the young twigs and larger branches of
young trees. The twigs are killed after the white areas have
encircled them. Many of the branches, or the entire tree, may
be killed in this manner. Shading seems to make the twigs and
branches more susceptible. Upon the whitened areas of the
bark numerous: grayish pustules are formed, containing the
fruiting-bodies of the fungus. After the bark is decayed, the
pustules stand out prominently. Projecting from the upper
surface of the grayish pustules are one to three short beaks which
represent the openings of the fruiting-bodies buried in the pus-
tules. Ascospores are formed in these fruiting-bodies and ooze
out through the openings during moist weather.
REFERENCE
Heald, F. D., and Wolf, F. A. The whitening of the mountain cedar,
Sabina sabinoides (H. B. K.) Small. Mycologia 2: 205-212,
pl. 31, figs. 1-3. 1910.
Brown Pocket HEARTWooD-RotT
Caused by Fomes roseus Fries
This heartwood-rot was first described as a disease of juniper,
but recently has been found commonly in fir, larch, spruce, pine,
hemlock and occasionally in arbor-vite, birch and maple, over
practically the entire United States wherever conifers are im-
portant forest-trees. It may be confused in some trees with the
red-brown root- and butt-rot caused by Polyporus Schweinitzir (see
page 294), unless the fruiting-bodies are present to identify it.
JUNIPER DISEASES 205
Symptoms.
The wood of the juniper is characteristically affected. Long
cylindrical and pointed pockets of brown charcoal-like decayed
wood are formed. At first these pockets are more or less sepa-
rated and vary from one to several feet in length. Later they
may increase in diameter
and merge with neighboring
pockets, forming large irregu-
lar decayed areas. The de-
ecayed’ wood in juniper is
dark brown but in other
trees may be lighter if the
normal wood is light colored. |
It breaks into cubes and is
easily powdered. With a
knife blade the charcoal-like
cubes may be scraped from
the cavity, leaving it smooth.
The wood around these cavi-
ties is normal and of the
natural color.
The fruiting-bodies of the
causal fungus on juniper are
produced in the holes in the
trunk where branch stubs are
inclosed. They conform to
the size and shape of the Fic. 34.— Fruiting-bodies of Fomes
hole. When formed on logs, athe
they vary from thin shelves to thick hoof-shaped rose-
colored bodies which are usually small (Fig. 34). The
upper surface may become black with age while the mar-
gin and under surface of newly formed pores is pinkish
red. The internal structure is flesh-colored or pinkish.
206 MANUAL OF TREE DISEASES
The pores in the under surface are minute and the tubes
very short.
Cause.
The brown pocket-rot of conifers is caused by the fungus
Fomes roseus (formerly called Polyporus carneus Nees). The
fruiting-bodies described above are perennial and are formed
from dead areas on living trees or on the dead trees after they
fall. Infection seems to take place mostly near the base of the
tree and the rot is confined to the lower part of the trunk. The
wood is destroyed in the pockets by the extraction of the cellu-
lose. The lignin remains and the fibers retain their entirety,
although the walls are much thinner than normal. For a fuller
description of the life history and control of wood-rotting fungi,
see page 64.
REFERENCES
Schrenk, Hermann von. Red rot, or pecky cedar (Polyporus carneus).
In Two diseases of red cedar, caused by Polyporus juniperinus
n. sp. and Polyporus carneus Nees. U.S. Dept. Agr. Div. Veg.
Phys. and Path. Bul. 21: 16—20, pls. 5-7, fig. 3. 1900.
Hedgecock, G. G. Notes on some diseases of trees in our national
forests. IV. Phytopathology 4: 181-188. 1914.
Wuite Pocket HEartwoop-Rot
Caused by Fomes juniperinus Schrenk
Junipers are affected by this destructive heartwood-rot in
central United States. At times, the trees are made hollow
for several feet up and down the trunk. Trees more than
twenty-five years old are more often attacked than younger
individuals.
Symptoms.
Varying with the stage to which the decay has progressed, the
affected trees show one or more large holes at the center or are
JUNIPER DISEASES 207
hollow. At first the decayed areas are a few inches in length
and pure white and are separated from one another by several
inches of sound wood which appears normal except that it is
somewhat brownish. Soon the white areas become holes with
their inner surfaces lined with white fibers mixed with a reddish
yellow felt of mycelium. The wood around the holes is brown-
ish and shades off gradually to the deep red normal wood. The
amount of soft white fibers around the edges of the large hole is
considerable and very striking in appearance when compared
with the normal red wood. When the holes become large, they
often fuse and cause hollow trunks. In very large trees there
may be several holes parallel to each other.
The fruiting-bodies of the causal fungus are very rare and
appear at branch wounds. ‘They are woody and usually hoof-
shaped. The upper surface is at first yellowish orange and later
turns to black with a yellowish margin. When young the top
is smooth but with age it becomes fissured. The lower surface
is yellowish brown. The inner substance of the fruiting-body
is reddish orange. A new layer of tubes is formed each year.
Cause.
White pocket heartwood-rot or white rot of junipers is caused
by Fomes juniperinus. The fruiting-bodies described above
are very rarely found. Infection is initiated by spores which
lodge on a broken stub of a branch. ‘The mycelium penetrates
into the center of the heartwood of the trunk where the first evi-
dence of decay is the turning white of the normally red wood.
Later new areas of decay originate a few inches above and below.
The lignin is abstracted from the cell-walls and the primary
layers of the walls are dissolved. These two actions leave the
remainder of the walls pure white and unattached to one an-
other, so that they fall apart leaving a hole in the wood. ‘The
life history and control of the wood-rot fungi are more fully
discussed on page 64.
208 MANUAL OF TREE DISEASES
REFERENCES ON WHITE Pocket HrArRtTwoop-RoT
Schrenk, Hermann von. White rot of the red cedar (Polyporus juni-
perinus n. sp.). In Two diseases of red cedar, caused by Poly-
porus juniperinus n. sp. and Polyporus carneus Nees. U. S.
Dept. Agr. Div. Veg. Phys. and Path. Bul. 21: 9-16, pls. 1-4,
figs. 1-2. 1900.
Hedgecock, G. G., and Long, W. H. Preliminary notes on three rots
of juniper. Mycologia 4: 109-114, pls. 64-65. 1912.
YELLOW Woop-Rot
Caused by Fomes Earlei (Murrill) Sace. (? = Fomes juniperinus
Schrenk)
This wood-rot is similar in appearance to the white heartwood-
rot of the red juniper. The yellow wood-rot occurs more or less
commonly in Arizona, New Mexico, Texas and Colorado in
mountain, one-seed and Utah juniper. The rot is most de-
structive in New Mexico, and at times the tree is so weakened
that it breaks over.
Symptoms.
Long longitudinal holes several inches in diameter are formed
in the heartwood. The holes are partially filled with decayed
wood matted together with light brown mycelium. The wood
around the holes is yellowish or light brown in color. Both the
heartwood and sapwood may be invaded and destroyed, al-
though the holes are usually confined to the heartwood.
The sporophores of the causal fungus are attached to the
affected tree. They emerge from the furrows or depressions
in the bark, usually within ten feet of the ground. They are
hoof-shaped to cylindrical, woody bodies, brownish to black
and deeply checked on top and yellowish beneath. The
inner substance of the sporophore is brownish or orange-
yellow. The pores on the under surface are rather large and
circular.
JUNIPER DISEASES 209
Cause.
The yellow wood-rot of the species of juniper found in the
Southwest is caused by a fungus named Fomes Earlei. There
is but little difference between this fungus and Fomes juni-
perinus, causing the white pocket heartwood-rot of red juniper
in eastern United States. Very few sporophores of Fomes
juniperinus have been found, although the rot caused in red
juniper is common. Sporophores of Fomes Earle: are common
where the trees are affected. It is believed by some that the
two species are identical but because very few specimens of
Fomes juniperinus are available for comparison, this has not
been fully determined. The rots are somewhat different al-
though similar in many respects. These differences may be
due, however, to the host and do not necessarily indicate that
the fungi causing them are different species. Further details
concerning the life history and control of wood-rot fungi will
be found on page 64.
REFERENCE
Hedgecock, G. G., and Long, W. H. Preliminary notes on three rots
of juniper. - Mycologia 4: 109-114, pls. 64-65. 1912.
Strincy Brown Woop-Ror
Caused by Fomes texanus (Murrill) Hedgecock and Long
This wood-rot affects both the heartwood and sapwood of
mountain, Utah and one-seed juniper. The rot is very destruc-
tive and common in Texas and New Mexico.
Symptoms.
The first signs of the decay are evident as small pockets of
light brown tissue in the spring-wood of the annual rings.
These pockets soon merge and the spring-wood becomes reddish
_ brown and is partially or entirely destroyed. This action leaves
concentric zones of badly rotted and apparently sound wood
P
210 MANUAL OF TREE DISEASES
which is characteristic of this wood-rot. Hollow trunks are
not formed. The less affected summer-wood of the rings and
the wood bordering the decayed area are yellowish brown. The
sapwood and bark are affected and permeated by the reddish
yellow mycelium.
The sporophores of the causal fungus appear from crevices in
the bark where the fungus has emerged from the sapwood and
inner bark. They are hoof-shaped or cylindrical woody bodies
with a light yellowish or brown to black checked upper surface.
The yearly growth of the sporophore is apparent in the concen-
tric furrows on the upper surface. The under surface is light
yellowish and the pores are very small. The inner structure is
yellowish.
Cause.
The stringy brown wood-rot of junipers in the Southwest is
caused by the fungus Fomes texanus. No definite studies are
reported on the method of infection. The general life history
and control of the wood-rot fungi are discussed on page 64.
REFERENCE
Hedgecock, G. G., and Long, W. H. Preliminary notes on three rots
of juniper. Mycologia 4: 109-114, pls. 64-65. 1912.
BasaLt Hrartwoop-Rot
Caused by Poria Weirii Murrill
This heartwood-rot is the most important basal decay of the
western red cedar throughout northwestern United States.
After the tree falls, the heartwood and sapwood of the entire
tree are soon destroyed by the same fungus. In the first stages
of decay, the wood is uniformly split into its separate annual
rings. The affected wood is brown and brittle.
The causal fungus forms fruiting-bodies on the fallen trunks
of the affected trees. These fruiting-bodies are brown and
JUNIPER DISEASES 2
rather soft sheets of fungous material spread over extensive
areas on the sides and bottom of the log. A single fruiting-body
may extend for several feet along the log. The surface of the
fruiting-body is covered with very fine pores. Two or three
layers of tubes may be found representing as many years of
successive growth and spore production.
REFERENCE
Murrill, W. A. An enemy of the western red cedar. Mycologia
6: 93-94, pl. 122. 1914.
CHAPTER XXIII
LARCH DISEASES
Tue three native species of larch or Larix are important
forest-trees in northeastern and northwestern United States.
The eastern and European larch are frequently used as orna-
mentals. The eastern larch is commonly affected by several
wood- and root-rots. Of these, the pecky wood-rot and red-
brown sapwood-rot are most destructive. The leaf-rusts are
rare. In the Northwest, the larch is not only subject to sev-
eral wood- and root-rots but is also seriously damaged by a
dwarf mistletoe which causes large swellings and witches’-
brooms. The seedlings are often killed by a fungus which
causes a root-rot.
SEEDLING Root-Rot
Caused by Rhizina undulata Fries
Seedlings of the western larch are killed by this root-rot
in northwestern United States. It may be found also in some
northeastern states since the fungus is known to occur in this
region. The diseased roots of seedlings from three to six years
old are matted together by an abundant growth of white my-
celium. The fruiting-bodies of the pathogene are formed on
the surface of the ground. They are dark brownish, undulat-
ing structures with a light colored margin when young. A
fuller description of this disease is given under hemlock diseases,
page 177.
Lear-Rusts
Caused by Melampsora Bigelowii Thiim. and M. Meduse Thiim.
The needles of larch are sometimes affected by two similar
rusts. These diseases have been found in various localities
212
LARCH DISEASES 213
and may be expected throughout the northern states from
the Atlantic to the Pacific. The fungi causing these two dis-
eases are closely related to the several other rust fungi of
pine, spruce, fir and hemlock.
Symptoms.
The rusts of larch are so similar that they cannot be
identified without the use of a microscope. The affected
needles in early spring show small whitish pustules bursting
through the epidermis. The epidermis of the leaf covering of
the pustules breaks open and the spores within are blown
away by the wind as a fine dust. The needles then turn yellow
and may fall off.
Cause.
The rust diseases of larch are caused by Melampsora
Bigelow and M. Meduse. Besides the stage produced on
the larch leaves, each of these fungi requires a period of growth
on other kinds of plants. The spores (aciospores) from the
pustules caused by the first mentioned species infect the leaves
of several kinds of willows. In the latter named _ species
the xciospores infect the leaves of certain poplars. On the
willows and poplars other spores (urediniospores) are produced
which continue the life history of the fungi. Over-wintering
teliospores on these two hosts germinate in the spring and pro-
duce basidiospores which infect the young leaves of the larch.
These facts in the life history of the two rust fungi make it
evident that the appearance of the diseases on the larch is de-
pendent on the presence of poplars or willows in close proximity.
A blister-rust of larch needles which also occurs rarely in
this country is caused by Melampsoridium betule (Schum)
Arthur. This fungus attacks birch in the United States but
the stage on larch does not seem to be common. It is known
on both birch and larch in Europe.
214 MANUAL OF TREE DISEASES
MISTLETOE Burt AND WItTCHES’-BROOM
Caused by Razoumofskya laricis Piper
The mistletoe disease of larch is common and destructive
in northwestern United States. It is especially abundant in
open stands and causes but little damage in the dense forests.
In moist and fertile areas, the larch attains full development
and is only rarely deformed by the mistletoe. On the other
hand in regions of light rainfall, variable temperature, low
humidity, dry soil and especially in open stands, the growth of
the mistletoe is favored and the tree suppressed. Measure-
ments made of unaffected and badly infested trees show that
the rate of growth of the larch may be reduced to one-half the
normal.
Symptoms.
Young and old larches are affected. The seeds of the mistle-
toe produce infection if they fall on the green twigs. Burls
are produced in the trunk and larger branches due to the irri-
tation caused by the roots of the mistletoe. Infected younger
branches are stimulated to produce abnormal twigs, forming
witches’-brooms. The foliage area of the tree is reduced by
the deforming of the branches and the general development
of the tree is suppressed.
Cause.
This burl and witches’-broom disease is caused by one of
the species of dwarf mistletoe, Razowmofskya laricis. The
roots of the parasite penetrate the bark and wood and grow
down the branch for some distance, sometimes entering larger
branches or the trunk. The irritation caused by the roots
of the parasite results in an increased growth of the affected
parts. The parasitic plants are inconspicuous, never being
more than about four inches tall. A cluster of yellowish
LARCH DISEASES 215
leafless stems growing out from the bark is all that can be seen.
A general discussion of mistletoe diseases will be found on page
54,
REFERENCES
Weir, J. R. Larch mistletoe: some economic considerations of its
injurious effects. U. S. Dept. Agr. Bul. 317: 1-25, figs. 1-13.
1916.
Weir, J.R. Mistletoe injury to conifers in the northwest. U.S. Dept.
Agr. Bul. 360: 1-38, pls. 1—4, figs. 1-27. 1916.
Precky Woop-Rot
Caused by Trametes pini Fries
Red-rot, ring-shake, peckiness or pecky wood-rot is the
most destructive wood-rot of conifers in the United States.
It is common in larch. The characteristics of the rot in larch
are similar to those produced in spruce, with the exception that
the action in the formation of pockets is less localized. The
spring-wood of the affected annual rings is largely destroyed,
leaving the denser summer-wood partially decayed and red
in color. Black lines are formed at irregular places. The
wood of the larch is thus more completely destroyed than that
of the other conifers. The sapwood and bark are readily in-
vaded and the living tissues killed, thus causing the death of
the parts of the tree above, as in the spruce and fir. A
more complete description of this wood-rot is given under
spruce diseases, page 324.
Rep-Brown SApwoop-Ror
Caused by Fomes pinicola Fries
Larch wherever it grows is commonly affected by this wood-
rot. Spruce, pine, fir and hemlock are also affected. The
wood is reduced to a red-brown powdery mass held together
by numerous plates of whitish mycelium. The sporophores
216 MANUAL OF TREE DISEASES
of the causal fungus are formed abundantly on the diseased
trees and on fallen logs. They have a red varnished margin
and a cream-colored under surface. Fuller details concerning
this heartwood-rot will be found under fir diseases, page 165.
Brown Heartwoop-Rot
Caused by Fomes officinalis Fries (= Fomes laricis (Jaeq.) Murrill)
This brown heartwood-rot is common and very destructive
in western United States in larch, pine, Douglas fir and other
conifers. In California and Nevada, sugar pines are the most
destructively attacked. In the Northwest, Douglas fir, western
larch, lodge-pole and western yellow pine are often seriously
affected. The rot resembles to some extent the brown checked
wood-rot caused by Polyporus sulphureus (see page 247).
Symptoms.
The affected heartwood is brownish or red-brown in color.
Felts of the mycelium of the fungus form in cracks in the wood.
The sporophores of the causal fungus are not formed abun-
dantly on the affected trees. They are large hoof-shaped or
globose bodies with a white, roughened, chalky upper surface.
The white material will rub off like powdered chalk. The
fruiting-bodies when young are soft and watery but become
very brittle when old. The inner structure is white, bitter to
the taste and has a distinct mealy odor. The under surface is
convex, whitish and covered with small pores.
Cause.
The brown heartwood-rot of conifers in the western forests
is caused by Fomes officinalis. This fungus also is known by
the name Fomes laricis. Infection takes place when the spores
from the tubes on the under side of the fruiting-body lodge in
open wounds where heartwood is exposed. For further detail
LARCH DISEASES DAW
concerning the general life history and control of the wood-
rotting fungi, see page 64.
REFERENCE
Meinecke, E. P. Forest tree diseases common in California and
Nevada. U.S. Dept. Agr. Forest Service. Unnumbered pub-
lication, pp. 1-67, pls. 1-24. 1914. ©
Brown Pocket HEARTWOOD-RotT
Caused by Fomes roseus Fries
This heartwood-rot is common in larch as well as in fir, spruce,
pine and hemlock, in almost every section of the country where
these trees grow. The rot may be confused at times with the
red-brown root- and butt-rot caused by Polyporus Schweinitzir
(see page 294). The decayed wood is brown, easily powdered
and looks like charcoal. At first long cylindrical or pointed
pockets of decayed wood are formed. Later these pockets
may join and large areas of the heartwood are uniformly brown
rotted. The fruiting-bodies of the causal fungus are produced
at branch stubs on affected trees or on the sides of fallen timber.
They may be either small and thin structures or large hoof-
shaped bodies. The under surface is rose-colored. For further
details concerning this heartwood-rot, see under juniper diseases,
page 204.
Rep-Brown Root- anp Burtt-Rot
Caused by Polyporus Schweinitzii Fries
Fir, pine, spruce, hemlock and arbor-vite in addition to,
the larch are affected by this wood-rot wherever these kinds of
trees grow. It 1s next in importance to the pecky wood-rot
of these trees. The affected heartwood of the roots and lower
part of the trunk is at first yellowish and cheesy but later be-
comes red-brown and brittle. This wood-rot is more fully
described under pine diseases, page 294.
218 MANUAL OF TREE DISEASES
YELLOW Root-Ror
Caused by Sparassis radicata Weir
In the Northwest the roots of larch are often destroyed by
this root-rot. Fir, spruce and pine are affected by the same
disease. The bark and sapwood of the roots are killed. Yel-
lowish fan-shaped plates of mycelium are found in the bark.
The medullary-rays and heartwood are also decayed and be-
come yellow or brown. The fruiting-bodies of the causal
fungus are peculiar. They are attached to the diseased roots
by long, fleshy stalks. New fruiting-bodies are formed each
year from the tip of the stalk. They are large, white, compact,
fleshy structures covered with curled and lacerated leaf-like
plates. These thin plates stand upright on the upper portion
of the fruiting-body or horizontally from the sides. The spores
of this fungus are borne over the entire exposed surface of the
fruiting-body. For further details concerning this root-rot,
see under fir diseases, page 170.
CHAPTER XXIV
LOCUST DISEASES
Tue native species of locust are unimportant forest-trees.
The common locust of eastern United States (Robinia Pseuda-
cacia) was more frequently used as an ornamental in previous
years than at present. Insect damage has made the tree
difficult to grow. The only fungous diseases of the locust that
have considerable importance are the yellow and brown checked
wood-rots. The yellow wood-rot is caused by a fungus that
grows only in the wood of the locust. This rot is common in
ornamental trees and often causes their death.
YELLOW Woop-Rot
Caused by Fomes rimosus Berkeley
The yellow wood-rot of the trunk and branches of the locust
is common throughout the range of this tree. Young trees
less than six inches in diameter are rarely affected.
Symptoms.
The central portion of the heartwood is reduced to a soft
yellow spongy mass for several feet up and down the trunk or
limb. From this central decayed area, as seen in cross-section,
several V-shaped bands reach out radially toward the sapwood.
When the wood is split lengthwise, these bands of decay are
seen to be one or two inches wide. At the center of each band
is a small reddish core and extending upward and downward
from this core the partially decayed wood varies from orange-
219
220 MANUAL OF TREE DISEASES
yellow to light straw-yellow at the edge of the band. When
the bands have reached the cambium and bark, compact red-
brown felts of mycelium replace the destroyed tissues. In
tangential section the narrow bands show as yellow lens-shaped
areas with red centers. The radial bands of decay become
more numerous and finally coalesce, and in this way all the
heartwood and sapwood is decayed.
The sporophores of the pathogene appear at various places
on the bark where the mycelium has penetrated the sapwood
Fig. 35.— Upper surface of fruiting-body of Fomes rimosus.
and bark. They are at first small, red-brown, hard knobs.
Each year a new layer of pores is added to the under surface.
After several years’ growth large brackets or hoof-shaped bodies
are formed. The upper surface is dark brown or black and
much roughened by numerous fissures which divide the surface
into irregular squares (Fig. 35). The under surface is dull
red-brown and extends upward over the edge of the sporophore
LOCUST DISEASES 221
in a smooth roll. The pores on the under surface are barely
visible.
Cause.
The yellow wood-rot of locust is caused by the fungus Fomes
rimosus. It is similar in appearance to Fomes igniarius except
when it is broken open the older layers of tubes do not show
the white filling. The spores from the tubes on the under
surface of the sporophore infect the locust at branch stubs or
through the tunnels made by the locust borer. The mycelium,
after destroying the central portion of the heartwood, reaches
out along the medullary-rays and initiates the bands of decay.
The yellow wood-rot fungus is not known to continue growing
in dead wood and timber made from affected wood is said to
last as long as sound timber. For further details concerning
the life history and control of wood-rotting fungi, see page 64.
REFERENCES
Schrenk, Hermann von. A disease of the black locust (Robinia
pseudacacia L.). Missouri Bot. Gard. Ann. Rept. 12: 21-31,
pls. 1-3. 1901.
Schrenk, Hermann von, and Spaulding, P. Black locust disease
eaused by Fomes rimosus. . Jn Diseases of deciduous forest trees.
U. S. Dept. Agr. Bur. Pl. Ind. Bul. 149: 45-46. 1909.
Brown CuHeckeD Woop-Rot
Caused by Polyporus sulphureus Fries
The heartwood and sapwood of locust is often reduced to a
red powdery mass by the sulfur fungus. Oak, chestnut, walnut,
butternut, maple and alder are the other principal kinds of
trees commonly affected by the same rot. The sapwood and
bark may be invaded and the tops of the trees or large limbs
are thus killed. The sulfur-yellow and orange-colored fruiting-
bodies of the causal fungus are produced in late summer from
wounds or from the bark where the mycelium has invaded the
222 MANUAL OF TREE DISEASES
sapwood. The reddish colored decayed wood splits into small
cubes with plate-like sheets of mycelium filling up the cracks
between. This wood-rot is similar in its effect on the different
kinds of trees and is more fully described under oak diseases,
page 247. |
Root-TUBERCLES
Caused by Bacillus radicicola Beijerinek
Locust roots often show small globose swellings. These
structures are abnormal lateral rootlets which are inhabited
by the nitrogen-fixing bacterium. The bacteria gain entrance
to the root through the root-hairs. They multiply in the cortex
cells and stimulate the tissues to over-growth. A discussion
of the relation between the host and parasite will be found
under alder diseases, on page 88.
CHAPTER XXV
MAPLE DISEASES
Many species of maple occur in all parts of the United States.
They are important forest-trees in the eastern and central states.
Several of the native and a few exotic species are the most
widely used of any trees for shade and ornament. The maples
are of the genus Acer (including Negundo).
In the forest the maple is seriously affected by the common
white wood-rot. Other wood-rots are also occasionally found.
Outside the forest, maples are subject toemany diseases which
at times are important. Several species of fungi cause diseases
of the leaves which may result in defoliation (see page 30).
Maples are also commonly affected by sun-scorch (see page 22).
The wilt disease has not been thoroughly investigated but is
known to have caused the rapid death of trees in several iso-
lated places. These diseases, together with the several wood-
rots, account to some degree for the commonly noted poor
condition of maples.
Tar Lear-Spot
Caused by Rhytisma acerinum Fries
The large tar-like blotches on maple foliage are very con-
spicuous. The leaves which develop several spots are often
shed prematurely, and young nursery trees may suffer per-
manent injury from defoliation. In eastern United States
the red and silver maple are often attacked. In Europe the
Norway and Sycamore maple are commonly affected by the
same disease. In this country the Norway and Sycamore
223
224 MANUAL OF TREE DISEASES
maple are rarely if ever affected, even when growing among
red and silver maples which are severely infected. This sub-
stantiates the results of investigations in Europe which show
that there are various strains of the tar-spot fungus. These
strains show preference for certain species of maples, but in
other respects are indistinguishable from one another.
Symptoms.
The first evidence of the developing spots on the maple leaves
are light green or yellowish areas. In the summer the spots
become black on the upper surface of the leaf due to the
black mycelium of the fungus. The surface of the tar-like
spots is wrinkled
with anastomos-
ing furrows and
somewhat raised
above the surface
of the leaf. The
spots are usually
a quarter or half
inch across (Fig.
36).
Cause.
The tar leaf-
spot of maples is
caused by the
fungus Rhytisma
acerinum. Spores are borne free on the upper surface of the
black mass of fungous tissue as it develops on the leaf. It is
not known whether these spores infect other leaves or not.
But from the number of leaves affected on some trees, it
seems certain that these spores must account for the general
prevalence of the infections. When the spotted leaves fall .
Fic. 36.— Tar leaf-spot of maple.
MAPLE DISEASES 225
to the ground, the mycelium inside the black spots develops
ascospores. ‘These are mature in the spring. With the return
of warm weather, the black layer of fungous tissue cracks
open and the edges fold back, exposing the fruiting-layers
within. The spores are probably shot into the air as are most
ascospores. The young maple leaves are infected by the
ascospores which lodge upon them and germinate.
Control.
Very little trouble will be experienced from this disease if
the affected leaves are destroyed by burning in the autumn.
Unless this is carefully done and all the affected leaves under
and around the trees are destroyed, the few remaining ones
may cause some infection in the spring. In exceptional cases,
as in nurseries, spraying with bordeaux mixture as the leaves
develop may be desirable. For general directions on spraying,
see page 357.
REFERENCES
Stewart, F. C. Black spot, Rhytisma acerinum (Pers.) Fr. Jn
Notes on New York plant diseases, 1. New York Agr. Exp.
Sta. (Geneva) Bul. 328: 364. 1910.
Schrenk, Hermann von, and Spaulding, P. Tar-spot. Jn Diseases of
deciduous forest trees. U. S. Dept. Agr. Bur. Pl. Ind. Bul.
149:19. 1909.
BLACK-SPECKED LEAF-SPOT
Caused by Rhytisma punctatum Fries
The silver maple of eastern United States (Acer saccharinum)
and the broad-leaf maple (A. macrophyllum) of the Pacific
Coast are occasionally affected by this leaf-spot. It does not
seem to be as abundant as the tar leaf-spot. During the
summer light green or yellowish areas about a half inch in
diameter appear in the leaf. Later several isolated black
spots the size of a pin-head develop on the upper surface of
the spot. In the autumn the affected area remains yellowish
Q
226 MANUAL OF TREE DISEASES
green after the remainder of the leaf has faded or turned
bright colored. The fungus causing this leaf-spot is a near rela-
tive of the tar leaf-spot fungus (see page 223). Spores are de-
veloped in the same manner and control measures are the same
for both diseases.
LEAF-SPOTS
Caused by Phyllosticta minima (B. and C.) E. and E., Gleosporium
apocryptum KE. and E., and other fungi
The leaves of maple are subject to a number of leaf-spot
diseases (see page 30). The two fungi named above are com-
mon in eastern United States and may be found every year.
Fic. 37.— Leaf-spot of maple caused by Phyllosticta minima.
MAPLE DISEASES Pipaih
Tn wet seasons defoliation may result. The illustrations show
the effect of these diseases on the leaf (Figs. 37 and 38). Many
of the other leaf-spots of maple appear similar to these, however,
and no accurate
determination can
be made without
a microscopic ex-
-amination of the
fungus.
The leaf-spot
caused by Phyllo-
sticta minima is
characterized by
light brown cir-
cular spots with
numerous — black
dot-like fruiting-
bodies near the
center (Fig. 37).
The general char-
acters of leaf-
spots, and the life history of the fungi causing them, are more
fully discussed on page 27.
Fic. 38.— Leaf-spot of maple caused by Gleosporium
apocryptum.
PowpeEery MILpEws
Caused by Uncinula circinata Cooke and Peck and Phyllactinia
corylea (Pers.) Karst.
Two species of the powdery mildew fungi are known on
maple leaves in the United States, Uncinula circinata and
Phyllactinia corylea (see page 35). The former has been
reported from northeastern and central United States and
the latter, which occurs on all kinds of trees, is distributed
throughout the country. These two diseases cannot be dis-
228 MANUAL OF TREE DISEASES
tinguished from one another except by the microscopic char-
acters of the black fruiting-bodies which are just visible to the
unaided eye. The mycelium of both fungi causes powdery
white, more or less definite spots on the under sides of the
leaves. The life histories and control of powdery mildew fungi
are discussed on page 37.
LeraFr-BLIGHT
Caused by Gloeosporium sp.
This leaf-blight has been observed on Norway maple (Acer
platanoides) in Connecticut, New York and Virginia. No
studies have been made on the disease and but little is known
Fic. 39.— Leaf-blight of maple caused by Gloeosporium sp.
concerning it. The leaves show yellowish and brown dead
areas along the main veins (Fig. 39). Later the leaves wilt
and fall from the tree. Minute brown spots form along the
veins. These are the fruiting-bodies (acervuli) of the causal
MAPLE DISEASES 229
fungus. The spores from these structures are disseminated by
the rain. It is to be expected that perithecia with ascospores
are formed in the leaves on the ground during the winter.
The twigs have not been found affected. This disease is
similar to the leaf- and twig-blight
of sycamores described on page 333.
The control measures are the same
for both of these diseases.
CANKER
Caused by Nectria cinnabarina Fries
Maples are commonly affected by
this canker. Other deciduous trees
may also be attacked by this disease
but it never assumes great impor-
tance owing to the causal fungus being
only weakly parasitic. Twigs, small
branches and young trees may be
killed by the girdling action of the
fungus.
Symptoms.
Small depressed dead areas of bark
around wounds or branch stubs are
the first evidences of the developing
canker (Fig. 40). Flesh-colored or Fie. 40.— Nectria canker on
pink hemispherical bodies are pro- a
duced on the dead bark. Later the same pustules become
chocolate-brown. If the fungus continues to spread, rolls of
callus are formed around the affected area each year, until an
open canker is produced which may girdle the limb. The
mycelium grows most luxuriantly in the sapwood, causing a
dark greenish discoloration (Fig. 41). The bark adjacent to the
230 MANUAL OF TREE DISEASES
affected sapwood dies and the mycelium invades the dead bark,
forming its fruiting-bodies on the outside. The canker develops
Fria. 41. — Cross and longitudi-
nal sections through a Nectria
canker on maple.
slowly and may at any time cease
to enlarge. The exposed wood is
then finally overgrown by the callus.
This canker is especially common
in severely wounded or recently
pruned trees.
Cause.
The canker of maples is caused
by the fungus Nectria cinnabarina.
Spores are borne over the outside of
the flesh-colored pustules during the
summer. After the pustules be-
come chocolate-brown, perithecia
are formed which produce asco-
spores. These spores are matured
over winter and produce infection
in wounds in the spring.
Control.
The cankers can be removed by
surgery (see page 351). All dead
bark and twigs should be cut away
at the same time, since the causal
fungus occurs everywhere as a com-
mon saprophyte. Pruning wounds should be at once protected
by a wound dressing (see page 348).
REFERENCE
Schrenk, Hermann von, and Spaulding, P. Nectria cinnabarina. In
Diseases of deciduous forest trees. U.S. Dept. Agr. Bur. Pl.
Ind. Bul. 149: 21-22.
1909.
MAPLE DISEASES 231
WILT
Caused by Verticillium sp.
Wilt is a recently discovered and little known disease of
silver, Norway and sugar maples. It has been found in New
York, Virginia and Ontario, Canada, and is probably more
widely distributed. Several trees have been observed which
were dying or had been killed by this disease. It seems
probable that a part of the common sun-scorch of maples-
may be found to be another symptom of this disease.
Symptoms.
In the few observations made on this disease, the common
and only external symptom is the blanching and sudden wilt-
ing of the foliage in midsum-
mer. The leaves of an entire
branch or side of the tree wilt
and become dry and wrinkled
at the same time. On cut-
ting into the sapwood of the
affected branch or trunk, the
outer layers will be found more
or less streaked with greenish
colored longitudinal lines. No
external fruiting-bodies have
been found on the bark. The green discoloration extends up-
ward and downward in the branches and trunk and may
enter the roots (Fig. 42).
Fic. 42.— Sections through the trunk
of a small maple affected by wilt.
Cause.
The wilt of maples is due to an unnamed fungus of the genus
Verticillium. Closely related species cause a similar disease,
usually confined to the roots, in barberry, eggplant and numer-
ous other plants. Other species of the same genus cause wilts
232, MANUAL OF TREE DISEASES
of cotton, potato and various field crop plants. The fungus
is known to form spores on branches of the mycelium but the
manner and place of fruiting and method of infection in the
maple is unknown.
Control.
Surgical methods are advised when this disease is to be con-
trolled (see page 345). Several diseased trees in a group have
been observed and the destruction of badly affected individuals
is necessary to prevent the fungus spreading to healthy trees
near by.
Common WuitE Woop-Rot
Caused by Fomes igniarius Fries
Silver and striped maple are more commonly affected by
this white wood-rot than the red and sugar maple. Poplar,
beech and oak are the most seriously affected of the many
species of deciduous trees which are susceptible to this fungus.
Beech and maple in mixture in the Adirondack Mountains are
often diseased to the extent that the stands will never be worth
cutting. Outside the forest, this disease is not so common.
The sapwood may be invaded and the tops of the trees or
large limbs killed. The sporophores and decay are similar for
all kinds of trees and are described under poplar diseases,
page 305.
Brown CHECKED Woop-Ror
Caused by Polyporus sulphureus Fries
Maples are at times affected by the sulfur fungus which
causes the brown checked wood-rot. Oak, chestnut, walnut,
butternut, locust and alder are also frequently affected by
the same rot. The wood is reduced to a reddish powdery mass
which splits in cubes, separated by sheets of mycelium. The
sporophores of the causal fungus are orange and sulfur-yellow
in color. They form from branch wounds or directly from the
MAPLE DISEASES 233
bark in late summer. The sapwood and bark are often invaded
and destroyed, causing the tops of the trees or large limbs to
die. The symptoms of the brown checked wood-rot are simi-
lar for all kinds of trees and are described under oak diseases,
page 247.
WuitE Strand Woop-Ror
Caused by Polyporus squamosus Fries
Many kinds of deciduous trees are reported as seriously
damaged by this white rot in Europe. Those specially men-
tioned are. maple, oak, elm, walnut, basswood, willow, ash,
birch, horse-chestnut and beech. In the United States, no
‘authentic information is available on this wood-rot, except
that the fungus is found in some cases growing from wounds
in living trees.
Symptoms.
The heartwood and sometimes the sapwood of the trees are
decayed. Trees in which the rot has affected the conduction
tissue of the sapwood show marked decline and are often
killed. The wood is characteristically rotted. It is almost
white and marked with pure white narrow strands of mycelium
running in the radial, tangential and longitudinal directions,
causing the wood to be split into small cubes. In general this
character is similar to the rot produced by Polyporus borealis
in the wood of conifers (see page 185).
The annual fruiting-bodies are easily recognized. They
are soft and watery and almost circular with a short stout stem
at one side attaching them to the tree. The top is slightly
convex and is covered with overlapping brown scales, while
the under surface is white and honeycombed.
Cause.
The white strand wood-rot of maples is caused by the
fungus Polyporus squamosus; so named because of the scales
234 MANUAL OF TREE DISEASES
on the top of the fruiting-bodies. It is commonly known as
the scaly or saddle-back fungus. Infection is effected by the
spores, which are wind-blown, lodging and germinating on
exposed wood, especially at broken or pruned branch stubs.
The less lignified elements of the wood-tissue are destroyed
and strands of mycelium fill the long channels thus opened up
in the wood. These strands run through the wood, replacing
the medullary-rays and spring-wood, thus causing the white
bordered cubes which are seen in cross and longitudinal sec-
tions. The life history and control of the wood-rot fungi will
be found discussed on page 64.
REFERENCES
Sechrenk, Hermann von, and Spaulding, P. White-rot caused by
Polyporus squamosus. Jn Diseases of deciduous forest trees.
U.S. Dept. Agr. Bur. Pl. Ind. Bul. 149: 48-49. 1909.
Buller, A. H. R. The biology of Polyporus squamosus, Huds., a
timber destroying fungus. Jour. Econ. Biology. 1: 101-138,
pls. 5-9, figs. A-F. 1906.
Untrorm WuHitrt Sapwoop-Rot
Caused by Hydnum septentrionale Fries
A white sapwood-rot of maple and beech is occasionally
found in eastern and central United States. This rot has not
been studied and described and is not very important. The
affected wood is soft and uniformly white. Brown zones
separate the affected area from the normal wood. Black
lines are sometimes found running in various directions in the
rotted wood.
The white fruiting-bodies of the fungus are very conspicuous.
They are large, flat, fleshy structures often a foot or two long
and a foot across. They are composed of a thick sheet of
mycelium adhering to the side of the tree with numerous
closely overlapping projecting shelves. The individual shelves
MAPLE DISEASES 230
are three or four inches long and project two or three inches
from the tree. The under surface of the shelves is composed
of pendent bristles or teeth (Fig. 43). The spores are borne
Sl 0
Fig. 43. — Lengthwise section through a fruiting-body of
Hydnum septentrionale.
over the surface of the teeth. The life history and control of
the wood-rotting fungi are more fully discussed on page 64.
WHITE STREAKED SApwoop-Ror
Caused by Pleurotus ostreatus Jacqu.
Maples and other deciduous trees, such as basswood, elm
and oak, are sometimes found affected by this sapwood-rot.
Infection takes place in open wounds caused by various agents.
The decayed area of wood is lighter in color than the normal
wood and is bounded by a narrow brown zone. The medullary-
236 MANUAL OF TREE DISEASES
rays are destroyed and the porous portion of the annual rings
is delignified and partially dissolved. The denser summer-
wood of the rings is least affected. The result of this action
is that the affected wood is light in weight and breaks easily
into flakes.
The sporophores of the causal fungus are fleshy, annual,
shelving structures with radiating plates or gills on the under
surface. ‘The sporophores are more or less sessile and appear
in clusters at wounds where the affected wood is exposed.
They are often found at the junction between two limbs. The
upper surface is smooth, slightly rounding and white or gray-
ish in color. The gills on the under surface extend on to the
stalk-like attachment to the wood. For more complete details
concerning the life history and control of the wood-rotting
fungi, see page 64.
REFERENCE
Learn, C. D. Studies on Pleurotus ostreatus Jacqu. and Pleurotus
ulmarius Bul. Annales Mycol. 10: 542-556, pls. 16-18. 1912.
Waite Burt-Ror
Caused by Fomes applanatus Fries
The heartwood of the lower part of the trunk and roots of
maple is sometimes destroyed by this rot. The decayed
wood is whitish, light in weight and has many white-stuffed
tunnels running in the horizontal direction. The sporophores
of the causal fungus are shelf-like, woody bodies, with a smooth
brownish upper surface and a white under surface. Further
details concerning this heartwood-rot will be found under
poplar diseases, on page 310.
CHAPTER XXVI
OAK DISEASES
Over fifty species of oak (Quercus) are native in the United
States. Many of these are important timber-trees. No region
is without one or more species of oak, except the northern Rocky
Mountains and the treeless plains. Although many kinds of
oak occur on the Pacific Coast and in the Southwest, the most
important forest-species grow in eastern and central United
States. Many oaks are used for shade and ornament.
The oak is more destructively affected by wood- and root-
rots than any other important deciduous timber-tree. These
diseases are also common in oaks used for ornament. Many
species of fungi cause leaf-spots and powdery mildews. White
oak, especially in the East, is more or less seriously affected by
leaf-blight caused by the same fungus which occurs on syca-
more (see page 333). This disease often results in defoliation.
In the South the leaf-blister is very common and often de-
structive. The twig-blight and Strumella canker described
below cause the death of many oaks in the East.
L&eaAFr-BLIGHT
Caused by Gnomonia veneta (Sace. and Speg.) Klebahn
Several kinds of oaks, especially the white oak, are attacked
commonly by this leaf-blight. Sycamores (or plane-trees) are
more seriously affected by the same disease. The spots de-
veloped on the leaves may vary from small isolated light
brown areas to large coalescing spots which involve a large
portion of the leaf (Fig. 44). When the spots occur on the
237
238 MANUAL OF TREE DISEASES
veins, large areas are killed and the tip of the leaf frequently
dies. The dead areas become light brown and very much
wrinkled. Minute darker brown pustules the size of a pin-
head or smaller are scattered over the dead area. Small
globules of sticky spores are developed from these pustules
in rainy weather and the spores may be washed to all parts
Fic. 44. — Leaf-blight of oak.
of the tree, causing the infection of other leaves. The twigs
are sometimes affected, but this symptom is less frequent in
oak than in sycamore. The life history of the causal fungus
is imperfectly known and is discussed under sycamore dis-
eases, page 333. Control measures are also the same as for
this disease on sycamore.
OAK DISEASES 239
Lrar-BLISTER
Caused by Taphrina cerulescens (Mont. and Desm.) Tulasne
Practically all species of oak seem to be affected by leaf-
blister. It is found throughout the United States and Europe.
Although occurring commonly in this range it does no par-
ticular damage except in southern United States, where it
is epiphytotic in
favorable seasons
and defoliation
results. It is re-
ported that the
growth of the tree
is seriously im-
paired and the
individual is
sometimes killed
by repeated de-
foliation.
Symptoms.
The blisters
make their ap-
pearance on the
leaves before they
are full grown.
The spots are at
first grayish or
bluish on the un-
der surface and
yellowish above.
A bulging of the leaf is soon apparent, the convex side of the
spot usually being on the upper side of the leaf (Fig. 45). The
blisters vary from a quarter to a half inch or more in diameter
Fic. 45.— Leaf-blister of oak.
240 MANUAL OF TREE DISEASES
and often become confluent, causing the leaf to curl. So far
as is known, there is only the one period of infection and no
subsequent spread to the other leaves of the tree occurs.
Practically all the leaves of the tree may be infected, however,
and where the blisters are numerous the leaves fall.
Cause.
Leaf-blister of oak is caused by the fungus Taphrina ceru-
lescens. This fungus belongs to the family Exoascacee, all the
members of which are parasitic and cause leaf-curls, leaf-blisters,
plum-pockets, witches’-brooms and other types of over-growths.
The common orchard disease, peach leaf-curl, is caused by a
closely related form and is similar to oak leaf-blister in many
ways. There are no fruiting-bodies formed by these fungi.
The spores are borne in asci which stand free on the surface of
the blistered or curled area. From the production of the spores
which takes place as the blisters are forming, until infection
occurs the next season, nothing is known concerning the life
history of this entire group of fungi. No other stage of de-
velopment is suspected but it is thought that the spores simply
rest until the next spring and are present in some way so that
they can infect the unfolding leaves. In the case of peach
leaf-curl, cold wet weather following a warm period, at the time
the buds are bursting, causes epiphytotics. Similar weather
conditions may result in more extensive infection in the case
of oak leaf-blister, but no observations are recorded on this
point. |
The mycelium does not enter the tissue of the oak leaf. It
simply penetrates the cuticle of the lower epidermis and lies
in contact with the outer walls of the epidermal cells. The
enzymes of the fungus diffuse into the leaf and cause a marked
reaction on the part of the leaf-tissues. The lower epidermal
and spongy mesophy] cells increase in number and the palisade
and upper epidermal cells increase greatly in size, causing the
OAK DISEASES 241
leaf at the infected point to become much thicker. The ex-
pansion of the affected area laterally, due to the increased
number and size of the cells, causes it to bulge and thus the
blister is formed. All the cells of the mycelium then increase
greatly in size and push the cuticle off. Within each mycelial
cell which is now an ascus, the spores are formed.
Control.
Apparently no spraying experiments of value have ever been
made for the control of leaf-blister of oaks. The method used
to control peach leaf-curl should be tried. It is, therefore,
suggested that the trees be sprayed with bordeaux mixture
4—4-50 or lime-sulfur 1-8 at any time after the leaves fall
and before the buds swell. The spraying should be thorough,
since the solution must coat every twig and bud to accomplish
the desired results. Peach leaf-curl is easily controlled by a
single application of any good fungicide in this way. The
spores must, therefore, in some way be present on the outside
of the twig or bud scales and the spray mixture kills them.
(See Hesler, L. R., and Whetzel, H. H. Manual of fruit dis-
eases, pp.'277-283.. 1917.)
REFERENCE
Wilcox, E. M. A leaf-curl disease of oaks. Alabama Agr. Exp.
Sta. Bul. 126: 171-187, pl. 1, figs. 1-38. 1903. (Bibliography
given.)
PowpEery MILpEws
Caused by Microsphera alni (Wallr.) Salmon, M. alni var. extensa
(Cooke and Peck) Salmon, Phyllactinia corylea (Pers.) Karst.
and Erysiphe trina Harkness
Four species of powdery mildew fungi (besides the brown
mildew, see page 243) are known to attack the leaves of oaks
in the United States. The first and third species mentioned
above occur commonly throughout the country on the leaves
R
242 MANUAL OF TREE DISEASES
of many kinds of trees (Fig. 46). The second species is a variety
of the first, seemingly confined to eastern, southern and central
United States, while the fourth is so far reported only from
California. All of these fungi cause powdery white patches on
Fic. 46.— Powdery mildew on oak leaf.
both sides of leaves, but do little damage. The black or brown-
ish fruiting-bodies can be seen scattered or in clusters over the
affected area of the leaf. The life history and methods of con-
trol of powdery mildew fungi are discussed on page 37.
OAK DISEASES 243
Brown MILDEW
Caused by Spherotheca lanestris Harkness
The leaves and twigs of several species of oak are often at-
tacked by this powdery mildew fungus in southern, central
western and extreme western United States. The mycelium
grows externally on the under sides of the leaf, the spots at
first being white and mealy but later appearing as a dark brown
felt due to a color change in the mycelium. The entire under
surface of the leaf may be covered as well as the growing twigs.
When infection occurs early in the season, the brown felt may
completely cover the young leaves and twigs, causing the leaves
to cease growth and remain dwarfed. The black fruiting-
bodies are buried in the mycelium on the under sides of affected
leaves. For a fuller discussion of the life history and control
of the powdery mildews, see page 37.
Larce LEAF-Spot
Caused by Monochetia Desmazierii Sace.
The leaves of red oak are affected by the large leaf-spot in
the southern Appalachians. The same disease affects chestnut
leaves in that region. The spots when fully developed are
very large, often being from one to two inches or more in di-
ameter. ‘Two or three such spots cause the death of most of
the leaf-tissue. The center of the spot is pale green or yellow
and is surrounded by concentric bands of red and brown.
The colored bands are less distinct on the under surface of the
leaf. Small black fruiting-bodies, arranged in clusters, dot
the affected area. The spores from these fruiting-bodies cause
the infection of other leaves. Fuller details concerning this
disease are given under chestnut diseases, page 139. Many
other leaf-spots occur on oak. A general discussion of the
leaf-spots will be found on page 27.
244 MANUAL OF TREE DISEASES
Twic-BLIGHT
Caused by Spheropsis malorum Berkeley (= Physalospora cydonie
Arnaud)
This twig-blight is common on chestnut oak in central
eastern United States. White oak and chestnut are also oc-
casionally affected by the same disease. The
smaller branches and twigs of trees of all ages
may be killed.
Symptoms.
The leaves wither and turn brown. The
mycelium of the causal pathogene grows in the
bark and sapwood. The diseased bark becomes
sunken and wrinkled (Fig. 47). Small black
fruiting-bodies break through the outer bark.
Under the dead bark, the sapwood is dark
colored. The mycelium extends for several
inches in the sapwood above and below the
bark-lesion. This is evident to the unaided eye
as a black streak when the bark is peeled from
the twig.
Cause.
The fungus causing this twig-blight is known
as Spheropsis malorum. It occurs as a weak
Twig-cankeron Parasite or saprophyte on the bark and twigs of
oak caused by many kinds of woody plants. The New York
plas ™ apple canker, black-rot and frog-eye leaf-spot of
apple are caused by this fungus. Spores ooze
from the black fruiting-bodies produced on the dead bark and
may be washed by the rain to other parts of the tree. The
fungus also rarely produces a perithecial stage which is known
as Physalospora cydome.
OAK DISEASES 245
Control.
The diseased twigs and branches should be pruned from the
tree. This may be done most efficiently in midsummer, as the
dead leaves show more plainly. Early the next spring after
the new leaves appear, all leafless twigs and branches should be
removed. If these measures are not taken, large trees may
often be killed after a few years. Care should be exercised to
prune the twigs at least six inches below the cankered area,
since the mycelium which spreads in the sapwood must all be
removed (see under symptoms).
REFERENCE
Ingram, Della E. A twig blight of Quercus prinus and related species.
Jour. Agr. Res. 1: 339-346, pl. 38, figs. 1-7. 1914.
STRUMELLA CANKER
Caused by Strumella coryneoidea Sace. and Winter
This canker of oak has been found to be common and de-
structive in Pennsylvania. Although not definitely reported
elsewhere, the fungus is known to occur in Missouri, Massa-
chusetts and New York. Its range may thus be supposed to
include northeastern United States. In Pennsylvania the
canker is found on white, scarlet, red, yellow and chestnut oak.
It also occurs destructively on the American chestnut. The
most damage is reported on red and yellow oak.
Symptoms.
Two types of cankers with intermediate gradations are de-
scribed. The most conspicuous form is found on red and
yellow oak and resembles the European apple-tree canker,
caused by Nectria galligena. The development of the cankers
of this type is slow. They are elliptical in outline and consist
of a depressed decayed center surrounded by concentric folds
246 MANUAL OF TREE DISEASES
of callus. The tissue around the canker is irregularly swollen,
causing badly deformed trunks.
The cankers gradually girdle the trunk and the trees are
either blown over or die. Suckers are formed in abundance
just below the cankers. On young smooth-barked trunks,
another type of canker is formed which is at first a light yellow-
ish raised area of bark and later develops into a sunken dead
surface which quickly girdles the stem. When the bark is
peeled from these cankers, thin sheets of white or pale brownish
mycelium are exposed.
On the surface of the affected bark of both types of cankers
are numerous small black nodules which are the fruiting-bodies
of the causal fungus.
Cause.
This canker of oaks and chestnut is caused by the fungus
Strumella coryneoidea. No ascus stage has been found con-
nected with this species and it is known only by the conidial
fruiting-bodies. Inoculations have not been made with this
fungus to determine fully its pathogenicity. The fungus is found
invariably associated with the cankers and has been isolated
and grown in pure culture. The black nodules on the cankers
which have not girdled the trunk do not produce spores and
are abortive. As soon as the trunk is girdled, however, nu-
merous brownish powdery pustules burst through the bark. °
The spores of the fungus are borne free on the surface of these
pustules and are believed to be carried by the wind. The
mycelium penetrates the wood deeply and causes a weakening
of the trunk. Infection usually occurs through a small branch
stub and from this center the mycelium spreads in all directions.
Control.
No definite control measures are suggested for this canker.
The ordinary surgical methods of canker treatment, however,
OAK DISEASES 247
will apply (see page 351). Care must be taken to remove the
affected wood beneath the cankered area or the mycelium may
spread into the healthy bark.
REFERENCES
Heald, F. D., and Studhalter, R. A. The Strumella disease of oak
and chestnut trees. Pennsylvania Dept. Forestry Bul. 10: 1-15,
pls. 1-12.. 1914.
Buckhout, W. A. The undesirability of red and black oak because of
fungus disease. Pennsylvania Agr. Exp. Sta. Ann. Rept. 1899:
250-252. 1900.
Brown CHECKED Woop-Rot
Caused by Polyporus sulphureus Fries
This important wood-rot is commonly found throughout the
United States in oak, chestnut, maple, walnut, butternut, lo-
cust and alder. It has also been reported in white spruce in
Maine. In Europe this disease is important in certain conifer
as well as deciduous trees. Although not as destructive in the
forests of the Northeast as some other diseases, it is the most
common wood-rot of shade and ornamental oaks. The sap-
wood and bark are affected and the tops of trees and large
limbs are killed when thus girdled. The causal fungus lives
saprophytically in all kinds of timber.
Symptoms.
The characters of the decay caused by the sulfur fungus
serve readily to identify it, even in the absence of the yellow
sporophores. The heartwood is usually first to be decayed.
Gradually, however, the sapwood and bark are invaded and
the living cells of these tissues are killed. The more com-
pletely decayed wood is often bordered by a wide slightly dis-
colored zone. The decayed wood becomes reddish brown and
has the appearance of charcoal except in color. It is easily re-
duced to powder by a blow. In the process of shrinkage which
248 MANUAL OF TREE DISEASES
accompanies the decay, the affected wood splits into cubes by
radial and circumferential cracks. The mycelium then grows
into and fills the cracks and forms tightly woven sheets (Fig. 48).
Fic. 48.— Brown checked wood-rot in oak.
The sporophores of the sulfur fungus are easily recognized.
They emerge in late summer from old branch wounds or di-
rectly from the bark where the mycelium has decayed the
sapwood. At first they appear as one large or several small
sulfur-yellow, soft and watery knobs of mycelium. These
OAK DISEASES 249
quickly grow larger and form a number of individual or closely
over-lapping shelves, from one to several inches wide (Fig. 49).
The upper surface of the shelves is bright orange-yellow marked
with redder areas, while the under
surfaces are sulfur-yellow and ap-
pear honeycombed. Thesubstance
of this mature fruiting-body is
tough but very watery. Insects
rapidly invade it and_ through
their work and decay caused by
bacteria and possibly other fungi,
the fruiting-body is quickly de-
stroyed. What remains of it soon
dries and becomes white and brit-
tle. The mycelium in the wood
lives from year to year and pro-
duces these yellow sporophores
annually. The young sporophores,
collected before the shelves are
fully matured, are among the best
of the edible fungi.
Cause.
Brown checked wood-rot is
caused by the fungus known as
Polyporus sulphureus. The spores
from the tubes on the under sur-
face of the sporophores are wind-
blown and infect the exposed
heartwood at branch wounds.
of Sie 2 Beles os
Fia. 49.— Fruiting-bodies of Poly-
porus sulphureus on an oak.
Certain deposits left by the mycelium of the fungus cause
the reddish brown discoloration.
For further details con-
cerning the life history and control of the wood-rot fungi,
see page 64.
250 MANUAL OF TREE DISEASES
REFERENCES ON Brown CHECKED Woop-Rot
Schrenk, Hermann von, and Spaulding, P. Red heart-rot caused by
Polyporus sulphureus. Jn Diseases of deciduous forest trees.
U.S. Dept. Agr. Bur. Pl. Ind. Bul. 149: 37-39. 1909.
Schrenk, Hermann von. Polyporus sulphureus (Bull.) Fr. Jn Some
diseases of New England conifers. U.S. Dept. Agr. Div. Veg.
Phys. and Path. Bul. 25: 40-44. 1900.
Atkinson, G. F. Polyporus sulphureus. Jn Studies of some shade
tree and timber destroying fungi. Cornell Univ. Agr. Exp. Sta.
Bul. 193: 208-214, figs. 64-70. 1901.
Hartig, R. Polyporus sulphureus Fr. Jn Die Zersetzungserschei-
nungen des Holzes ete., pp. 109-113, pl. 14. 1878.
Common Wuite Woop-Rot
Caused by Fomes igniarius Fries
Oaks, especially those species belonging to the black oak
group, often are found with the heartwood reduced to a white
punk. Beech and poplars, especially the aspen and balm of
Gilead, are the most destructively and commonly affected of
the various kinds of deciduous trees attacked by this fungus.
In Europe this is the most important of the wood-rots of the
oak in the forest. In the United States, the brown checked
wood-rot of oak seems to be more destructive. This is es-
pecially true outside the forest, where shade and ornamental
oaks are concerned. The sapwood of oak is more commonly
invaded than is the sapwood of the other trees affected, re-
sulting in stag-head and dead limbs. The sporophores and
nature of the rot which are similar for all kinds of trees are
described under poplar diseases, on page 305.
Wuite Pocker HEartwoop-Rot
Caused by Polyporus Rheades Fries (= Polyporus dryophilus Berkeley)
The heartwood of many species of oaks and sometimes of
poplars, is destroyed by this disease. Although found in oaks
practically over the entire United States, this rot is particu-
OAK DISEASES DAS
larly destructive and common in the Southwest and along the
Pacific Coast. In poplar it is found rarely and then often fol-
lowing the common white wood-rot caused by F. igniarius. The
white pocketed rot of the heartwood of oaks is confined largely
to the upper portions of the larger and older trees.
Symptoms.
The first evidence of this rot in oaks is a discolored water-
soaked area in the heartwood. Later delignification results in
the medullary-rays turning white. In longitudinal section
this produces a mottled appearance of white irregular lines
running lengthwise and broader white areas joining these at
intervals. The wood between these white areas is slightly dis-
colored. In more advanced stages, the white areas involve
adjacent tissues and become more extensive and less definitely
linear. The small amount of discolored wood between the
white areas remains firm. Irregularly distributed in the de-
cayed wood are brown areas varying from an eighth to a half
inch across. The wood surrounding the white pocketed surface
is discolored and water-soaked. In some species the symptoms
vary slightly from those described above. In chestnut oak
the spring-wood of the annual rings is yellowish white ‘and the
tissue between these concentric zones is light brown. In
poplar the rot as seen in cross-section produces alternate zones
of whitish and yellow tissue. ‘The same brown areas are present
as in the oak.
The sporophores formed at branch wounds on the oaks are
flat and shelf-like or hoof-shaped, but when formed directly
from the bark they are almost globose. A peculiar diagnostic
character of these sporophores consists in a hard, granular
sandstone-like core with radiating white mycelial strands run-
ning through it. This core extends back into the rotted wood
of the tree for a short distance. The upper surface is rusty
yellow or brown and at first is hairy but later becomes smooth.
252 MANUAL OF TREE DISEASES
The under surface is brown as is the inside structure, including
the granular core.
Cause.
The white pocketed rot of oaks and poplars is caused by the
fungus Polyporus Rheades which is also known by the name
P. dryophilus. The sporophores described above are annual.
The rot may be confined largely to the branches and upper
part of the trunk or the tree may be rotted from the base to top.
Infection occurs most commonly in broken branches, from
which the mycelium extends down into the trunk. When in-
fection takes place through dead side branches or at the base
of the tree, through fire scars, the rot may extend the entire
length of the trunk. For fuller details concerning the life
history of wood-rot fungi and the nature of the decay caused
by them, see page 64.
REFERENCES
Hedgecock, G. G., and Long, W. H. Heart-rot of oaks and poplars
caused by Polyporus dryophilus. Jour. Agr. Res. 3: 65-80, pls.
8-10. 1914.
Schrenk, Hermann von, and Spaulding, P. Piped-rot of oak and
chestnut. Jn Diseases of deciduous forest trees. U. 8. Dept.
Agr. Bur. Pl. Ind. Bul. 149: 39-40, pl. 5. 1909. (Note: The
piped-rot of oak described is due to P. Rheades and that of chest-
nut to P. croceus.)
Hartig, R. Polyporus dryadeus Fr. Jn Die Zersetzungserschei-
nungen des Holzes ete., pp. 125-128, pl. 17. 1878. (This is a
discussion of the rot due to P. Rheades and not P. dryadeus.)
Strinc AND Ray Burt-Rot
Caused by Polyporus Berkeleyi Fries
This heartwood-rot of the base of oak trees is found through-
out eastern and central United States. It is not known to be
as common or destructive as several of the other wood-rots of
oaks. Mature and over-mature trees are affected. It is never
found in the tops of trees but is limited to the base of the trunk
OAK DISEASES 253
and the larger roots. The decay extends from the surface of
the ground upward in the heartwood for a distance of one to a
few feet and in its final stages leaves a large hollow cavity.
Symptoms.
When badly rotted trees are cut, they fall after the thin shell
of heartwood is cut through and the trunk carries with it the
partially rotted hollow cylinder of wood from the stump. The
odor of the freshly cut rotted wood is very strong and resembles
anise oil. The first indication of the decay is seen in longi-
tudinal section as a yellowish or whitish area from four to eight
Fie. 50.— Fruiting-body of Polyporus Berkeleyi.
inches long. The summer-wood in this region is delignified
and the individual fibers are separated by the dissolving of the
cementing layer between them. As the decay progresses the
dense whitish summer-wood is completely destroyed. This
leaves the medullary-rays and strands of porous spring-wood
intact. The interwoven rays and strings of wood are brownish
at first but soon are covered with whitish mycelium. The
strands slowly become more brittle and finally collapse, leaving
a hollow cavity. The decayed area becomes larger and is
bordered by a zone of whitish wood with the string and ray
rot stage projecting into the hollow cavity.
The sporophores arise from the exposed larger roots or may
254 MANUAL OF TREE DISEASES
appear to come from the soil near the base of the tree. In ail
cases, however, they will be found attached by mycelial strands
to the roots. The sporophores are usually large and may occur
as two to five overlapping shelves or as a single more or less
circular, expanded, toadstool-like body supported on a thick
stalk (Fig. 50). The center of the upper surface is depressed
where it is attached to the stalk. The upper surface is white
or yellowish, while the under surface is whitish and covered
with large angular honeycomb-like pores.
Cause.
The string and ray butt-rot of oaks is caused by Polyporus
Berkeleyi. The spores are borne around the inner surfaces of
the angular pores of the sporophores. Infection takes place in
wounds at the base -of the tree, such as fire-scars. The life
history and control of wood-rotting fungi are discussed more
fully on page 64.
REFERENCE
Long, W. H. Three undescribed heart-rots of hardwood trees, espe-
cially of oak. Jour. Agr. Res. 1: 109-128, pls. 7-8. 1913.
Wet Heartwoop-Ror
Caused by Hydnum erinaceus Fries
Oak and other deciduous trees are affected by this wet heart-
wood-rot. White and red oaks are most commonly affected.
The disease is common in central United States and is some-
times found in other parts of the country.
Symptoms.
In the early stages of this decay, the wood becomes lighter
in color and the woody tissue between the medullary-rays is
destroyed. Later the entire structure of the wood disappears
and there remains only a white soggy mass. Large cavities
OAK DISEASES 255
or entirely hollow trees are thus formed. The cavities are
filled or lined with yellowish mycelium.
The fruiting-bodies of the causal fungus are formed annually
at wounds or insect tunnels. They are globose and may be as
large as a foot across. The upper surface is hairy and covered
with drops of water. The under surface and the margin of the
fleshy fruiting-body are covered with numerous long pendent
spines or teeth. Insects soon destroy the fruiting-body.
Cause.
The wet heartwood-rot of oaks and other trees is caused by
Hydnum erinaceus. The spores are borne over the outer sur-
face of the teeth on the under side of the fruiting-body. They
are disseminated by the wind and infection takes place in
wounds of all sorts. Further details concerning the life history
and control of wood-rots will be found on page 64.
REFERENCE
Sehrenk, Hermann von, and Spaulding, P. Disease caused by Hydnum
erinaceus. Jn Diseases of deciduous forest trees. U. S. Dept.
Agr. Bur. Pl. Ind. Bul. 149: 44-45, pl. 7. 1909.
Honetycoms HrEartwoop-Rot
Caused by Stereum subpileatum Berkeley and Curtis
This heartwood-rot of oak is common in Arkansas, Missis-
sippi and Louisiana. It is also found in Kentucky, Ohio,
Missouri, Virginia and Florida and probably is generally dis-
tributed over southern United States. Several species of oaks
are affected. The sapwood is not destroyed and the sporophores
of the fungus occur only on dead fallen trees or on dead areas
in living trees.
Symptoms.
The affected wood is at first slightly discolored and water-
soaked. Light colored areas appear at various places in the
256 MANUAL OF TREE DISEASES
discolored region and develop into white pockets. They are
located partially in the porous spring-wood of one ring and in
the summer-wood of the adjoining ring. Later the pockets
become hollow and have a white lining. They become larger
in time until finally limited by reaching a large medullary-
ray on each side. Only a narrow layer of brownish wood
separates the adjoining pockets. In longitudinal sections, the
pockets are seen to be from three to five times as long as wide.
The discolored area extends from one to six feet beyond the
region showing the pockets. In the first stages of the decay,
this rot closely resembles the white piped butt-rot caused by
Polyporus croceus (see page 258). The latter rot usually ex-
tends its activities more rapidly upward than radially, causing
the decay of a few annual rings, while the honeycomb-rot in
white oak, at least, spreads uniformly in both directions.
Freshly cut wood affected by this rot is said to have the odor
of old honeycomb.
The sporophores are rarely available to identify this rot in
living trees, except when a large area of the affected heartwood
is exposed. Sporophores develop on the felled timber in a
year or two and continue to form for several years. They are
from a quarter of an inch to two inches wide, rather thick
shelving bodies occurring one over the other in long rows. The
upper surface is at first downy and light yellowish brown, later
becoming smooth and gray. Concentric furrows mark the
upper surface into zones which vary in color. The under
surface is light yellowish brown and smooth.
Cause.
The honeycomb heartwood-rot of oaks is caused by the
fungus, Sterewm subpileatum. The fruiting-bodies described
above are annual structures which become dry and _ persist
through the winter and may revive the following season. The
spores are borne over the entire smooth under surface of the
OAK DISEASES ALS
shelves. The fungus finds entrance into the tree where heart-
wood is exposed at fire-scars, branch wounds and the like.
While usually found in the base of the trees, it sometimes oc-
curs in the tops. The sapwood of the living tree is not affected,
but when the tree is felled the mycelium grows into the sapwood
and causes a similar decay.
Control.
In the forest this rot can be controlled by preventing fires,
which are responsible for the scars that furnish a ready en-
trance point for infection. Likewise it is essential to remove or
burn dead and diseased oaks that are standing, as well as cull
logs, for on these the sporophores will continue to form for
several years. These measures will also keep several of the
other butt-rots and heartwood-rots of oaks under control.
REFERENCE
Long, W. H. A honeycomb heart-rot of oaks caused by Stereum sub-
pileatum. Jour. Agr. Res. 5: 421-428, pl. 41. 1915.
Sorr Hrartwoop-Rot
Caused by Polyporus obtusus Berkeley
Black oaks in eastern and central United States are affected
by this heartwood-rot. Several trees are usually found affected
in a group where the disease occurs.
Symptoms.
The affected heartwood is lighter in color than the normal
wood and finally becomes almost white. The wood does not
check and retains its normal fibrous character. It, however,
is weak and breaks easily. The rot progresses rapidly and the
trunks are weakened so that they snap off during wind-storms.
The fruiting-bodies appear annually on the side of the trunk.
They are more or less hoof-shaped and at first white and spongy.
S
258 MANUAL OF TREE DISEASES
Later they become yellowish or brown. The upper surface
and the rounded edge and outer margin of the lower surface
are hairy. The remainder of the under surface is covered
with roundish or sinuous pores, the edges of which are irregular,
making the under surface rough.
Cause.
The soft heartwood-rot of black oaks is caused by Polyporus
obtusus. The spores borne within the tubes on the under sides
of the fruiting-bodies are blown about by the wind. Infection
usually takes place by the spores entering the tunnels made
in the wood by the insect, Prionoxystus robinia. From the
tunnels the mycelium spreads upward and downward in the
wood. The fruiting-bodies are usually produced at the insect
burrow where infection occurred. For further details con-
cerning the life history and control of wood-rot fungi, see
page 64.
REFERENCES
Spaulding, P. A disease of black oaks caused by Polyporus obtusus
Berk. Missouri Bot. Garden Rept. 16: 109-116, pls. 13-19.
r
eine Hermann yon, and Spaulding, P. Soft rot of oaks caused
by Polyporus obtusus. Jn Diseases of deciduous forest trees.
U.S. Dept. Agr. Bur. Pl. Ind. Bul. 149 : 41-42, fig. 5. 1909.
Waite Pirep Burr-Rotr
Caused by Polyporus croceus Fries (= P. Pilote Schw.)
This wood-rot is found in oak and chestnut. The wood of
the roots and base of the trunk is most commonly affected,
although when dead branches are common it may be found in
the upper part of the trunk. It has proved destructive in
Arkansas, Virginia and New York and probably is generally
distributed throughout eastern and central United States.
The decayed wood is at first filled with white areas which en-
OAK DISEASES 259
large and become hollow cavities with white margins. These
pockets become so abundant that the summer-wood is largely
converted into strings of white fibers leaving the wood brittle
and easily broken. Further details concerning this white
pocket- or piped-rot will be found under chestnut diseases,
page 150.
Straw-CoLoreD Butt-Ror
Caused by Polyporus frondosus Fries
This rot of the heartwood of the base of oak and probably
of chestnut is found in eastern and central United States but
does not seem to occur very commonly or destructively. It
develops only in the base of the trunk. The wood is not en-
tirely destroyed and the trees do not become hollow.
Symptoms.
In longitudinal section the upper advancing margin of the
decay is indicated by long, slender, white lines extending for
several inches upward into the sound wood. In advance of
the white lines, the wood is water-soaked and reddish in color.
The rotted wood is at first white and later tan- or straw-colored.
Most of the tissue is delignified but is firmly held together by
the less affected medullary-rays. The cut ends of the trunks of
felled trees become reddish brown after a month or two.
The sporophores of the causal fungus arise from exposed or
buried roots near the base of the tree. They are composed of
a fleshy stem which is much branched, the ends of the
branches forming small flat over-lapping shelf-like structures.
The whole fruiting-body is more or less globose. The upper
surfaces of the shelves are gray or drab and the under surfaces
white.
Cause.
The straw-colored butt-rot of oak is caused by Polyporus
frondosus. The spores from inside the tubes on the under sides
260 MANUAL OF TREE DISEASES
of the shelves of the fruiting-body cause infection in wounds at
the base of the tree. The life history and control of the wood-
rot fungi will be found discussed on page 64.
REFERENCE
Long, W. H. Three undescribed heart-rots of hardwood trees, espe-
cially of oak. Jour. Agr. Res. 1: 109-128, pls. 7-8. 1913.
Waitt Woop-Rot
Caused by Fomes Everhartii (Ellis and Gall.) Sechrenk
This wood-rot has been found common in black jack oak and
probably occurs in other species. It has not been fully de-
scribed. It is said to resemble closely the common white wood-
rot caused by Fomes igniarius. ‘The rot extends into the sap-
wood. The sporophores of the causal fungus also resemble
those of Fomes igniarius. They are shelf-like and rarely hoof-
shaped. The upper surface is at first brown, but later becomes
black and checked by many fissures. The under surface and
margin are brown. The pores in the under surface are very
small.
REFERENCE
Schrenk, Hermann von, and Spaulding, P. Heart-rot of oaks caused
by Fomes Everhartii. Jn Diseases of deciduous forest trees.
U.S. Dept. Agr. Bur. Pl. Ind. Bul. 149: 48, pl. 3. 1909.
Waite Burt-Rotr
Caused by Fomes applanatus Fries
The heartwood of the lower part of the trunk and roots of
oak is sometimes destroyed by this rot. The wood becomes
whitish and light in weight but retains its fibrous structure.
The rotted wood when split shows numerous sinuous white-
stuffed tunnels resembling the work of insects. The sporo-
phores of the causal fungus are often found at wounds near the
OAK DISEASES 261
base of the trunk. The form on oak is usually thick, with a
dark gray, rough upper surface, an acute margin and a slightly
roughened, white under surface. This heartwood-rot is more
fully described under poplar diseases, on page 310.
WuitEe Root-Ror
Caused by Polyporus dryadeus Fries
Many species of oaks are affected by a white root-rot which
occurs apparently throughout the range of the oaks in the
United States and Europe. Although not as important as
many of the other wood- and root-rotting fungi, oaks growing
under adverse conditions are often found affected. The ulti-
mate result of the attack is the death of the tree or it may be
uprooted during wind-storms.
Symptoms.
The first indication of the rot is a reddish or brownish colora-
tion of the inner bark-tissues. The adjacent sapwood then be-
comes reddish brown and watery. The discoloration advances
-into the wood and the color of the decayed areas changes to
white. The bark becomes loosened and shreds into strips.
The rot finally involves the larger roots and extends into the
butt of the tree but does not progress above the surface of the
ground. The smaller roots are completely decayed and look
like pith. They are light in weight and when twisted break
into concentric layers. Older partially decayed roots, in
longitudinal section, show the white or cream-colored rotted
bark and wood bounded by a dark brownish zone one to three
inches wide which marks the progressing area of change from
normal wood to white punk. The radial and longitudinal
whitish bands appearing in the affected wood are due to the
mycelium of the fungus which is aggregated in the porous
regions of the annual rings. White patches of mycelium ap-
262 MANUAL OF TREE DISEASES
pear on the surface of the outer bark of affected roots. The
largest roots may be rotted to the center and the decayed wood
is finally spongy and easily crushed.
The sporophores of the causal fungus form on exposed roots
when the tree is blown over or at the very base of the trunk,
arising at the surface of the ground. They are large, irregu-
larly shaped masses of a corky or woody texture (Fig. 51).
When developing, they are watery, and large drops of water
Fig. 51. — Fruiting-body of Polyporus dryadeus.
often form on the outer growing margin. These drops leave
depressions in the surface. The upper surface is uneven
and light brown, changing with age to darker brown and
black. The under part is oblique to the surface of the
ground in the thicker forms and more or less horizontal in
the thinner forms. The pores in the under surface are
soon stuffed with mycelium, making them invisible. The
outer margin of the sporophore is thick and rounded. In-
sects soon destroy the under surface and outer margin but the
OAK DISEASES 263
black partially rotted central mass may remain for years at-
tached to the root or trunk.
Cause.
The white root-rot of oaks is caused by the fungus Polyporus
dryadeus. The sporophores are rarely found but the rot is not
uncommon. The method of infection has not been described.
No fungous strands are found in the soil around the rotted
roots, as in the shoe-string root-rot, and the trees apparently
are not attacked in groups. The spores produced in the tubes
of the sporophore probably find lodgment on exposed roots
and thus initiate infection.
The mycelium grows first in the bark and then into the sap-
wood and heartwood. The brownish watery zone of the first
stage of decay is due to the production of a brownish liquid
which fills the cells. Later this disappears and the cell con-
tents and a portion of the cell-walls are dissolved. There is
little delignification, although the wood appears white. The
ease with which the wood splits into concentric rings and frac-
tures crosswise is due to the very thin walls left in the porous
part of the annual ring and medullary-rays. The tree suffers
general decline because of the destruction of the conducting
tissue of the roots and they may be killed outright when the
larger roots are attacked first.
REFERENCE
Long, W. H. Polyporus dryadeus, a root parasite on the oak. Jour.
Agr. Res. 1: 239-250, pls. 21-22. 1913.
CHAPTER XXVII
PINE DISEASES
Over thirty species of pine (Pinus) occur as forest-trees in the
United States. No region of the country where trees grow is
without representatives of this important group. A large part
of the timber of the country is made from pines. The various
native pines and many exotic species and varieties are used
for ornamentals.
Pine is subject to many destructive diseases wherever it
grows. The most important of these are root-rots, wood-rots,
blister-rusts, mistletoe injury, leaf-cast and various types of
winter-injury. The importance of these types of diseases
varies with the species and region of the country in question.
Pecky wood-rot and the different blister-rusts of the branches
and trunks probably cause the most damage. The white pine
of the northeastern states was reasonably free from important
diseases until the introduction from Europe of the blister-rust
fungus. Pines outside of the forest often suffer severely from
winter-drying and other types of injury due to extremes in
temperature.
SEEDLING Root-Ror
Caused by Rhizina undulata Fries
The seedlings of several species of pines in the forests of
northwestern United States are killed by this root-rot. The
fungus is also present in several eastern states and may cause
similar damage. The roots cf seedlings three to six years old
are killed. Examination shows the. roots and a quantity of
264
PINE DISEASES 265
soil to be matted together by white mycelium. Brown fruiting-
bodies are formed on the surface of the soil around diseased
trees. This fungus is more fully discussed under hemlock
diseases, page 177.
Lear Buister-Rvusts
Caused by fungi of the genus Coleosporium
Several species of the genus Coleosporium grow in the needles
of pines, occasionally causing defoliation. These rust-fungi
require, in addition to the pine, some other kind of plant on
which to continue their life history. Such an alternation of
hosts is not uncommon in the rust-fungi. In the case of the
Coleosporium leaf-rusts of pine, «ciospores are produced in
the yellow blisters pushed out from the pine needles. These
spores cannot reinfect the pine, but they may cause infection
of the leaves of certain near-by flowering plants. Here the
development of the fungus is continued and_ urediniospores
are formed. The urediniospores infect other plants of the
same kind and by a succession of several generations of these
spores the rust may become prevalent during the summer for
a considerable distance away from the pine which developed
the eciospores. In the autumn a brown layer of another type
of spores (teliospores) is formed on the plants which produced
the urediniospores. The teliospores germinate while they are
still attached to the host and minute basidiospores are formed.
These spores are short-lived and are blown about by the wind.
If they come into contact with the needles of the proper species
of pine, they may initiate a new infection. Thus the seasonal
life history of the fungus is completed.
By eliminating the flowering plant, which must be present
for the fungus to complete its development, the rust is incapable
of existing. The minimum distance for the successful inter-
change of spores between the pine and the alternate host is
variable. Control is sometimes accomplished when all the
266 MANUAL OF TREE DISEASES
flowering plant hosts are removed, so that none exists within
a thousand feet of the pines. A safer distance would be a
quarter or a half mile, depending on the contour of the land
and the nature of the surrounding vegetation. The elimina-
tion of all the plants of the kind required by the blister-rust
fungi is not easily accomplished. Nevertheless, it is an efficient
and sure method of control, if the eradication is thoroughly
done. For a further discussion of the factors involved in carry-
ing out eradication methods, see under blister-rust of five-
needle pines, page 274.
Many of the species of Coleosporium that are known in the
uredinial and telial stages on various weed plants have not
been connected with the blister-rust stage on pine needles.
Either this has not been found and described, or the relation
between the stages on the pine and weed host has not been
definitely proved to represent the life history of a single species.
When all the stages are known, the fungus is called by its
Coleosporium name. When only the blister-rust stage is
known on the pines, it is classified in the large form genus
Peridermium and is given a temporary specific name.
Below are given brief descriptions of the blister-rusts of the
needles of pines, with their distribution, the species of pine
affected and the alternate weed hosts, so far as these facts are
known. In most cases these blister-rusts cannot be identified
except by microscopic examination.
An inconspicuous blister-rust is known to occur in Maryland
on scrub pine. The name of the causal fungus is Coleosporium
inconspicuum (Long) Hedgeock and Long. The alternate weed-
hosts on which its life history is completed are the tickseeds
(Coreopsis verticillata and C. major).
Scotch pine needles are affected by Coleosporium sonchi-
arvensis (Persoon) Lev. This disease has been reported only
from Wisconsin. The fungus was imported from Europe.
The yellow blisters are small, being about one-sixteenth of an
PINE DISEASES 267
inch long or smaller and only project slightly above the surface
of the needle. The life history is completed on the sow thistles
(species of Sonchus).
A blister-rust of the needles of lodge-pole and western yellow
pine is caused by Peridermiwm montanum Arthur and Kern.
It is known from central Montana westward and northward.
The yellow pustules on the pine needles are about one-sixteenth
of an inch long and project only slightly above the surface of
the needle. The alternate weed hosts are probably the differ-
ent species of Arnica.
A blister-rust of the needles of short-leaf pine is caused by
Peridermium intermedium Arthur and Kern and is known from
central Missouri and Arkansas to central North Carolina.
The yellow pustules on the needles are from one-sixteenth to
one-eighth of an inch long and project above the surface of the
needle about one-sixteenth of an inch. The alternate weed
host has not been determined.
A conspicuous leaf blister-rust is known on loblolly, long-leaf,
sand, short-leaf, spruce, western yellow, pitch, pond and Cuban
pines. The causal fungus is Coleosporium vernonie B. and C.
(=C. elephantopodis (Schw.) Thiim.) and is found from Vir-
ginia to Florida and westward to central Texas. The yellow
pustules on the needles are larger than those of the other pine
leaf blister-rusts. They are about one-fourth of an inch long
and three thirty-seconds of an inch high. The alternate weed
hosts of this rust are different species of ironweed and elephant’s-
foot (Vernonia and Elephantopus).
A leaf blister-rust of pitch and Norway pine is caused by
Coleosporium solidaginis (Schw.) Thiim. and is known from
Massachusetts and central New York southward to central
North Carolina.. Although the disease has been found only
within the above indicated area, there is the possibility of its
appearance on pitch and Norway pine at almost any point in
North America, since the stages of the causal fungus on the alter-
268 MANUAL OF TREE DISEASES
nate weed hosts are found throughout the country. This rust is
similar to several other blister-rusts which affect the pitch pine.
The yellow pustules project above the surface of the needles
from one thirty-second to cne-sixteenth of an inch. The
alternate weed hosts are species of goldenrod and wild aster.
The rust is able to maintain itself on these weeds without the
presence of the pitch pine, by the wintering-over of the ure-
diniospores which reinfect the goldenrod and aster.
A prominent leaf blister-rust of pitch pine is caused by Cole-
sporium campanule (Persoon) Ley. and is known from New
Jersey and central Indiana southward to central North Caro-
lina. It differs from the other blister-rusts of pitch pine in that
the yellow pustules on the needles are much larger and tongue-
shaped. They are from one-sixteenth to one-eighth of an inch
long and project above the surface about one-sixteenth of an
inch. The alternate weed host is the tall bellflower (Cam-
panula americana).
Another blister-rust of pitch and Norway pine is caused by
Coleosporium delicatulum (Arthur and Kern) Hedgecock and Long.
It is found along the Atlantic coast from Massachusetts to
Florida. It may have a much wider range than this, since its
alternate stages on the weed host, species of Euthamia, have
been found from Maine to Kansas and southward to West
Virginia and Texas. The leaves of the pines show in the spring
very small yellow blisters, from one thirty-second to one-fourth
inch long and scarcely protruding above the epidermis of the
needle.
Short-leaf, long-leaf, pitch and loblolly pine are affected by a
needle blister-rust in central eastern and southeastern United
States, caused by Coleosporium ipomee (Schw.) Burrill. The
pustules on the pine needles are flattened, narrow and about
one-sixteenth of an inch long. The life history is completed
on many species of merning-glory (Ipomeea).
Short-leaf and loblolly pines in Georgia and North Carolina
PINE DISEASES 269
have been affected by a needle blister-rust caused by Coleo-
sporitum terebinthinacee (Schw.) Arthur. The pustules are
tongue-shaped and project about one-sixteenth of an inch from
the needles. The life history of this fungus is completed on
rosin-weed (species of Silphium).
The needles of scrub and probably of short-leaf pine from
Pennsylvania to Illinois and southward are attacked by Coleo-
sporium helianthi (Schw.) Arthur. The blisters are tongue-
shaped and project from the leaf about one-sixteenth of an inch.
The life history of the fungus is completed on sun-flower (Heli-
anthus).
The needles of long-leaf, loblolly and pitch pine are attacked
by Peridermium fragile Hedgecock and Hunt. The blisters are
narrow and inconspicuous. The alternate host for the com-
pletion of the life history of this fungus is not known.
In Florida the needles of loblolly and spruce pine are attacked
by Peridermium minutum Hedgeock and Hunt. The blisters
are low and a little narrower than long. The alternate host for
the completion of the life history of this rust is unknown.
The needles of pifon are attacked by Coleosporium ribicola
(C. and E.) Arthur, practically throughout the range of this
species in Colorado, New Mexico and Wyoming. The blisters
appear on the pine needles while snow is still present. The
alternate hosts of this fungus are species of currant and goose-
berry (Ribes). The pustules on the currant and gooseberry
leaves are larger and more prominent than the felt-rust (see
page 274).
REFERENCES
Arthur, J. C., and Kern, F. D. North American species of Perider-
mium. Bul. Torrey Bot. Club, 33: 403-488. 1906.
Arthur, J. C., and Kern, F. D. North American species of Perider-
mium on pine. Mycologia 6: 109-138. 1914.
Hedgecock, G. G., and Hunt, N. Rex. New species of Peridermium.
Mycologia 9: 239-242. 1917.
Hedgecock, G. G. Notes on some western Uredineew which attack
forest trees. Mycologia 4: 141-147. 1912.
270 MANUAL OF TREE DISEASES
Lear-Rust
Caused by Gallowaya pini (Galloway) Arthur
The leaves of scrub pine are commonly affected by this rust
throughout its range in central eastern United States. This
disease differs from the blister-rusts of pine needles in the
teliospores being borne on the pine and no alternate host being
required (see page 265). Yellow spots occur near the tips of
the leaves. On these spots are formed linear, reddish orange
pustules which burst through the epidermis. These pustules
may be a half inch long. The bright color soon fades and they
are inconspicuous. The teliospores germinate in the spring,
producing basidiospores which infect other scrub pine needles.
LeEaF-Cast oF WHITE PINE
Caused by Hypoderma strobicola Tubeuf
White pine is sometimes injured in eastern United States
by this leaf-cast. Pitch pine and hemlock are reported to be
affected by the same disease. The affected needles at first
show yellowish spots and later turn reddish yellow and brown.
The tissues of the twig may also be killed. Later in the season
several small elliptical black fruiting-bodies appear on the
outer surface of the needles. The fruiting-bodies are mature
the following spring. They split open and the spores are shot
into the air during prolonged rain periods. For further details
concerning the leaf-cast diseases, see page 38.
REFERENCES
Graves, A. H. Leaf blight. Lophodermium brachysporum Rostrup.
In Notes on diseases of trees in the southern Appalachians 1.
Phytopathology 3: 133-139, figs. 5-10. 1913.
Spaulding, P. The present status of the white-pine blights. U. S.
Dept. Agr. Bur. Pl. Ind. Cire. 35: 1-12. 1909.
PINE DISEASES PH
Brown Fer.t-Biicut
Caused by Neopeckia Coulteri (Peck) Sace.
The brown felt-blight of pine is a common disease at altitudes
from six to eleven thousand feet above sea level in northwestern
United States. The leaves and twigs are covered and matted
together by an abundant growth of brown mycelium. It is
indistinguishable from the brown felt-blight of other species of
conifers. The behavior of this disease is in every way parallel
to the similar disease of spruce which is discussed on page 317.
LeaFr-Cast AND WITCHES’-BROOM OF WESTERN YELLOW PINE
Caused by Hypoderma deformans Weir
This disease is destructive to western yellow pine in the
Northwest and on the Pacific Coast. A similar disease on
Jeffrey pine in California may be caused by the same fungus.
The needles of western yellow pine of all ages are killed. Seed-
lings and young trees may be destroyed outright. On older
trees the needles of the season become infected, gradually turn
yellow and brown and fall from the twigs. They may remain
on the tree for cne cr more years, however, and this gives the
appearance that the needles cf all ages are affected. The
mycelium enters the young twigs. The affected twigs remain
stunted and large brooms are formed. The brooms hang
from the limb. The black fruiting-bodies of the fungus
break through the epidermis of the leaves in the autumn.
They are mature the following spring and may shed their spores
throughout the summer. Further details concerning the leaf-
cast diseases will be found on page 38.
REFERENCE
Weir, J. R. Hypoderma deformans, an undescribed needle fungus of
the western yellow pine. Jour. Agr. Res. 6:277-288, pl. 32,
figs. 1-4. 1916.
DAD MANUAL OF TREE DISEASES
Twic-BLIGcHT
Caused by Cenangium ferruginosum Fries
This disease is reported as common and destructive in Europe
on Scotch, Austrian and white pines and on European silver
fir. In this country very little mention of it has been made.
It is reported on white pine in Ohio and the causal fungus has
been found on long-leaf, western yellow and Monterey pine.
On these latter trees the fungus was not shown to be parasitic.
Mature trees are more often affected than younger ones and
the disease is unknown on trees less than five years old. In
Europe this disease is said to occur in epiphytotics which sweep
over large forest areas.
Symptoms.
The terminal buds of affected twigs die in the spring. Later
the older needles turn red and die from the base to the tip.
The dead needles fall and leave the twigs bare.
Small fruiting-bodies are formed on the dead twigs and
branches. In wet weather the fruiting-bodies open and are cup-
shaped, measuring about one-eighth of an inch across. During
dry weather they close and are more or less globose. In this
condition they are dusty brown or black but when they are open
the inner surface of the cup is yellowish or dirty greenish yellow.
Cause.
This twig-blight of pine is supposed to be caused by the
fungus Cenangium ferruginosum. Asci containing ascospores
are borne on the yellowish inner surface of the fruiting-bodies.
The ascospores are forcibly ejected and borne by the wind for
long distances. Other types of fruiting-bodies, resembling
those described above, are also formed which produce simple
spores. These, however, are not known to play any important
part in the life history of the fungus. There is some question
whether this fungus is primarily responsible for this disease.
PINE DISEASES 273
It seems more probable that winter-drying and other types of
winter-injury may account for the injury and that the fungus
is secondary and only semi-parasitic.
Control.
The only measure of control known is to prune off the dead
twigs and burn these, together with all other brush and refuse
from coniferous trees that may be in the vicinity.
REFERENCES
Fink, Bruce. Injury to Pinus strobus caused by Cenangium abietis.
Phytopathology 1: 180-183, pl. 26. 1911.
Schwarz, Frank. Die Erkrankung der Kiefern durch Cenangium
Abietis, pp. 1-126, pls. 1-2. 1895.
MIstTLETOE Burits AND WITCHES’-BROOMS
Caused by Razoumofskya campylopoda (Knglem.) Piper, and R. ameri-
cana (Nutt.) Kuntze
Western yellow and lodge-pole pine are affected respectively
by these two dwarf mistletoe parasites. In northwestern .
United States much damage results from the diseased condition
they cause. The general result of burl and witches’-broom
formation is a reduction in foliage which causes slow growth
and finally death when infection is heavy. Likewise, the dis-
eased areas of bark offer ready places of entrance for insects
and wood-rotting fungi. Trees of all ages are affected. ‘Trees
with the lower branches or trunk affected early in life suffer
more severely than those infected later. The brooming of the
lower branches diverts a large part of the growth energy of the
tree and the tops are dwarfed and die, causing stag-headed or
spike-topped trees.
Symptoms.
The roots from the germinating mistletoe seeds enter the
leafy twigs or through wounds in the bark of older branches.
T
274 MANUAL OF TREE DISEASES
Swellings of the limb are first formed and later many abnormal
branches are sent out and ragged broom-like growths are pro-
duced. Burls at the base of the branches and on the side of
the trunk also develop where the roots of the parasite find a
foothold. The mistletoe plant may die but the stimulus still
continues to cause the abnormal growth. The brooms may
become so heavy when burdened with ice and snow that the
limb breaks. The needles of the old brooms are usually smaller
and shorter-lived than on healthy branches. For a general
discussion of the mistletoe diseases of trees, see page 54.
REFERENCE
Weir, J. R. Mistletoe injury to conifers in the northwest. U. S.
Dept. Agr. Bul. 360: 1-38, pls. 1-4, figs. 1-27. 1916.
Burister-Rust or FiveE-NEEDLE PINES
Caused by Cronartium ribicola Fischer de Waldheim
The fungus causing the blister-rust of five-needle pines is
native in Europe. With the extensive use of the American
white pine in western Europe for forest-planting, it became
widely distributed on this tree and was soon recognized as an
important enemy of the white pine. As early as 1890 and 1900,
it was prevalent in all the countries of western and northern
Europe and was known in Siberia and Japan. The fungus
is supposed to have been originally confined to the Swiss stone
pine of Europe, which is not very seriously affected by it. In
Germany, France, England and other countries of western
Europe the blister-rust soon became so prevalent and de-
structive that the further use of the American white pine in
reforestation was largely abandoned. Previous to this time
large numbers of white pine were grown in the forest nurseries,
and this disease was found to affect seriously a large percentage
of the trees in some regions.
PINE DISEASES 275
Even with these facts known, no definite action was taken
in the United States to prevent the introduction of this fungus,
and in 1906 it was first found at Geneva, New York. Later,
in 1909, it was discovered in recently imported seedling stock
in New York, Vermont, New Hampshire, Massachusetts,
Connecticut, Pennsylvania, Indiana and Ohio. The demand
for white pine nursery stock both for forest and ornamental
plantings had far exceeded the amount produced in this country
at that time, and several hundred thousand trees had been im-
ported annually from Germany and France. It is, therefore,
not surprising that numerous diseased pines were found in the
different states where this stock was planted. Although at-
tempts were made to eradicate the known diseased trees, the
fungus is now generally prevalent in the New England states
and New York and is known in restricted areas in Wisconsin
and Minnesota.
All pines which have their needles in fascicles of five are ex-
pected to be susceptible. It is definitely known that the
eastern white pine, western white pine and sugar pine are
susceptible. As yet the fungus has not been found in western
United States where the two important western species of
this group grow. The damage that may result to the five-
needle pines in the forest in this country cannot be prophesied
at this time. Young trees and the younger branches of older
trees are most seriously affected. In plantations of European
stock in New York state not more than one per cent of the
trees were ever found affected. However, in several places
under actual forest conditions in northeastern United States
where the fungus has existed unnoticed for many years, a much
larger percentage of the stand is affected.
The fungus causing white pine blister-rust requires the pres-
ence of some species of gooseberry or currant for the comple-
tion of its life history. The spores developed on the pines
cannot infect other pines but must lodge on the leaves of cur-
276 MANUAL OF TREE DISEASES
rant or gooseberry bushes in order to continue the cycle of de-
velopment. Spores are then produced throughout the summer
on these plants which cause the infection of other goose-
Fic. 52. — Blister-rust on
twig of white pine.
berries and currants. In the autumn
another type of spores (teliospores) is
developed on the affected currants and
gooseberries and from these are formed
basidiospores which cause the infection
of the young branches of five-needled
pines. The distribution of this fungus
on the pines, therefore, is dependent on
the presence or absence of gooseberries
and currants, and if present the amount
of damage done is somewhat dependent
on their abundance. Unfortunately sev-
eral species of these plants occur as
common weeds practically throughout
the range of the five-needle pines in the
United States.
Symptoms.
The young leaf-bearing twigs are in-
fected and the mycelium grows in the
bark and may extend into the larger
branches and trunks. The affected bark
is usually swollen, but the tissue remains
normal and healthy in appearance for
two or three years. In the second or
third spring after infection occurs, the
prominent fruiting-pustules of the fungus
appear on the bark (Figs. 52 and 53).
These blister-like pustules are irregularly
hemispherical or elongate, one-eighth to
one-half inch across and orange-colored.
PINE DISEASES 7.
The covering of the blisters breaks and a fine yellow powder
of thousands of spores dusts out and is blown away by the
wind. The blister stage on the pine is formed in early spring
and by midsummer the white
coverings of the blisters disap-
pear and only rounded depres-
sions remain in the bark to mark
their location. The area of bark
from which the blisters are pro-
duced usually dies but the my-
celium extends into the surround-
ing healthy bark. The yellow
blisters are produced year after
year from the newly invaded
bark until on older trees cankers
several feet long are sometimes
formed. Usually the branch or
trunk is soon girdled and the
parts of the tree beyond the
girdled point die. The fungus
cannot exist except in living
tissue and, therefore, is not har-
bored after the affected part of
the tree is killed. Young trees
with the trunk affected show a
stunted and compact growth and
a slight yellowish color instead
of the normal green.
Infected currant and goose-
berry leaves show slightly yellow-
ish spots which are more distinct
on the under surface. Small
yellowish blisters are pushed out
é Fic. 53. — Blister-rust on trunk of
from the lower epidermis and young white pine.
278 MANUAL OF TREE DISEASES
when the covering is broken, a rounded mass of yellow
spores (urediniospores) is exposed (Fig. 54). Later in the
Fic. 54.— Cronartium ribicola (uredinial stage) on under side of currant leaf.
season, from the same lesions several slender brown bristle-
like structures are pushed out from the under sides of the
leaves (Fig.55). When
the affected areas of
the leaf are numerous,
these brown bristles so
completely cover the
under side of the leaf
that it appears as
coarse brown felt, and
thus the common name
for this disease on cur-
rants and gooseberries
is felt-rust. But little
damage is caused to
the affected bushes, al-
though defoliation may
occur earlier than nor-
mally when the leaves
are heavily infested.
The species of currant
Fic. 55.— Cronartium ribicola (telial stage) on
under side of currant leaf. Felt-rust. and gooseberry vary
PINE DISEASES 279
greatly in susceptibility. The cultivated black currant is
most susceptible, the under sides of the leaves being often
completely covered with the felt-stage. Gooseberries in general
are more resistant than currants.
Cause.
The blister-rust of five-needle pines and the felt-rust of cur-
rants and gooseberries are caused by the fungus, Cronartiwm
ribicola. Before the stages on the two kinds of plants were
known to be caused by the same fungus, the stage on the pine
was called Peridermium strobi. The life history of this fungus
has been indicated above. The eciospores formed in the
blisters on the pine branches infect the leaves of gooseberry
and currant. After a period of development in the leaf-tissue,
urediniospores are formed which infect other gooseberry and
currant leaves. From the same pustules the teliospores are
developed in long hair-like masses. These spores are not
disseminated but germinate and produce small, globose spores
(basidiospores) on the short germ-tubes. The basidiospores
are shot from their attachment and may cause infection of the
pine. In this way, although the pine is not infected by the
zeclospores produced in the blisters, the mycelium of the
fungus after about two months’ growth in the currant or
gooseberry produces the kind of spore which will infect the
pines.
Weather conditions in relation to the spread and severity
of attack of this fungus are not fully understood. Moisture
is necessary for the germination of the different spores and
from analogy to other similar diseases, it would be expected
that the stage on currants and gooseberries would be more
abundant in wet seasons. The distance over which the spores
are transported by the wind depends largely on prevailing
air currents and the topography of the region. In a dense
growth of underbrush in the forest the fungus would not be
280 MANUAL OF TREE DISEASES
expected to spread as rapidly in a given season as it would in
more open country.
Control.
Although repeated attempts had been made since 1896 to
secure a federal law which would prevent the entry of foreign
stock likely to harbor and introduce dangerous fungi and in-
sects, such a law was not enacted until 1912. The blister-rust
fungus had by that time become established in various locali-
ties in northeastern United States. The extermination of the
fungus was attempted where it was known. In New York
all the known areas where foreign white pine stock was planted
were inspected yearly. The diseased trees and all currant
and gooseberry bushes within five hundred feet of them were
destroyed. When the fungus was found prevalent in western
Massachusetts in the fall of 1915, more extensive surveys were
planned for 1916 and as the result, the fungus was found to be
generally prevalent throughout the territory east of the Hudson
River and Lake Champlain. In 1917 it was found practically
throughout New York state. Despite the previous attempts
at its eradication in isolated areas and any efforts that may
be made at general control in the future, the fungus is now so
well established in this country that it will continue to spread
and exist wherever conditions are favorable.
In certain regions in which the white and other five-needle
pines are important as ornamentals, the native wild species of
gooseberry and currant are very scarce. Such conditions
exist in the lower Hudson River valley and on Long Island.
In these regions this disease could easily be controlled if the
cultivated garden varieties of gooseberry and currant were
eliminated. However, when one neighbor grows one of these
plants and the next has five-needle pines to protect, no generally
satisfactory agreement will be reached in most cases. ‘The
elimination of currants and gooseberries for a distance of one-
PINE DISEASES Sil
half mile from the pines will probably control this rust. If
this distance is not possible, a separation of five hundred feet
or more will be partially beneficial.
In forested areas where wild currants and gooseberries are
common, the further growing of white pine may have to be
abandoned. The elimination of the bushes over extensive
areas will probably never prove as profitable as planting or
encouraging natural reproduction of some other species of
tree suited to the conditions. Where currants and gooseberries
are not very abundant and the experiment of eliminating them
is thought practicable, results may be obtained if the work is
vigorously prosecuted year after year. The total cost and
the possibilities of failure must influence the planning of this
kind of control when timber values alone are to be considered.
REFERENCES
Spaulding, P. The blister rust of white pine. U. S. Dept. Agr.
Bur. Pl. Ind. Bul. 206: 1-88, pls. 1-2, figs. 1-5. 1911. (Bibli-
ography given.)
Spaulding, P. The white-pine blister rust. U.S. Dept. Agr. Farmers’
Bul. 742: 1-15, pl. 1, figs. 1-5. 1916.
Spaulding, P. New facts concerning the white-pine blister rust.
U. S. Dept. Agr. Bul. 116: 1-8. 1914.
Spaulding, P. Foresters have a vital interest in the white-pine
blister rust. Proc. Soe. Am. For. 11: 40-47. 1916.
Atwood, G. G. Emergency bulletin on the blister rust of pines and
the European currant rust. New York Dept. Agr. Hort. Bul.
2: 1-15, pls. 1-2. 1909.
Paul, B. H. The pine blister. New York Conservation Com. Bul.
15: 1-18, figs. 1-8, map. 1. 1916.
SWEET-FERN Rust
Caused by Cronartium comptonie Arthur
This rust disease occurs on two- and three-needle pines in
eastern United States and is commonly known as blister-rust.
It is found on the native pitch, scrub, loblolly, western yellow,
282 MANUAL OF TREE DISEASES
jack, lodge-pole, Jeffrey, Norway and short-leaf pines and on
the imported Scotch, Austrian and mugho pines. Only very
young trees are generally affected and it is most important as a
nursery and young plantation disease. It is known to have
caused the death of a large number of the susceptible pines
in certain nurseries in Massachusetts, Connecticut, New York
and Michigan. The common weeds, sweet-fern (Comptonia
asplenifolia) or sweet-gale (Myrica Gale) must be in the vicinity
of the pines for this fungus to complete its life history. If
this plant is not present, the unaffected trees will not be en-
dangered by the diseased pines.
Symptoms.
This rust produces symptoms on two- and _ three-needle
pines very similar to the blister-rust which occurs on five-
needle pines (see page 276). Small branches and the trunks of
young trees are affected. Slight enlargements are usually
formed. On these swollen areas yellowish blisters are pushed
out in early spring. The arched covering breaks and the
orange-colored spore-mass inside dusts out as a fine powder
and is blown away.
On the sweet-fern and sweet-gale (Comptonia asplenifolia
and Myrica Gale), small yellowish pustules are formed on
the under sides of the leaves in summer, followed later by
brown bristles which project from the same spots. These
structures are similar to those formed on gooseberry and
currant leaves affected with felt-rust (see page 277).
Cause.
The sweet-fern rust of two- and three-needle pines is caused
by the fungus Cronartium comptonie (=Peridermium comp-
tonie Orton and Adams), a close relative of the blister-rust fungus
on white pine. The life history and control of this rust-fungus
is similar to the white pine blister-rust except that it has
PINE DISEASES 283
its alternate stages on sweet-fern and sweet-gale instead of on
currants and gooseberries (see page 279).
REFERENCES
Spaulding, P. Notes on Cronartium Comptonie, II. Phytopathol-
ogy 3:308-310. 1913.
Clinton, G. P. Cronartium Comptoniew Arth. (I. Peridermium pyri-
forme Pk.). Connecticut Agr. Exp. Sta. Ann. Rept. 1907—
1908 : 380-383, pl. 28. 1908.
Weir, J. R. Observations on the pathology of the jack pine. U.S.
Dept. Agr. Bul. 212: 1-10, pl. 1, figs. 1-4. 1915.
Spaulding, P. Noteson Cronartium Comptonie III. Phytopathology
7:49-51. 1917.
CoMANDRA Rust
Caused by Cronartium comandre Peck
This is one of the six blister-rust diseases of the stems of
pines in the United States. Although known commonly as
blister-rust, it is here called the Comandra rust of pines to
distinguish it from the other five similar diseases. The Co-
mandra rust occurs on pines having two or two to three needles
in a bundle and not on the three-needle pitch pines. It has
been found on lodge-pole, jack, western yellow and table-moun-
tain pine, in several eastern, north-central and western states.
A part of the life history of the causal fungus is spent on species
of Comandra and on these plants it has been found over the
entire northern and central part of the United States from the
Atlantic to the Pacific. In the western states the Comandra
rust is an Important disease of the pines which are susceptible.
In certain regions a large percentage of the younger trees
has been found affected or killed. Older trees are rarely
attacked. In Pennsylvania the disease causes the death of
many young table-mountain pines.
Symptoms.
The trunks and limbs of trees less than two or three inches
in diameter are attacked. Spindle-shaped swellings are pro-
284 MANUAL OF TREE DISEASES
duced which may be several inches long except in very young
trees where no swellings are noticeable. The trunk may
become infected by the fungus extending into it from infected
branches. The fruiting-bodies appear on the affected bark
in early spring. They are yellowish blisters, usually about
a quarter of an inch or smaller in diameter and may be longer
than broad. The covering of the blister breaks and the spores
are blown away as a fine orange-colored powder.
The spores from the yellow blisters infect the leaves and
younger stems of species of Comandra. Small yellowish or
reddish pustules are formed on light colored areas of the leaf
and a little later brown bristles project from the same spots.
The plants are dwarfed and often premature defoliation occurs
when the leaves are badly affected.
Cause.
The Comandra rust of pines is caused by the fungus Cronar-
tium comandre (=Peridermium pyriforme Peck). The ecio-
spores formed in the blisters on the pine bark cause the infection
of the leaves and young stems of Comandra. On that host
urediniospores are formed which infect other Comandra plants.
The urediniospores are closely followed by the production of
the bristle-like teliospore columns, the individual cells of which
germinate and produce the basidiospores. ‘These latter spores
are wind-borne and may cause the infection of the pines, if
they are near by. Both the pines and species of Comandra
must be present in the same locality for this fungus to exist
on the pines.
Control.
The elimination of the species of Comandra from the vicinity
of nurseries and young plantations is necessary if this disease
is to be controlled. In the forest the diseased trees may be
destroyed as a measure of protection for the young growth
PINE DISEASES 285
coming on. However, a few will always escape detection and
if the Comandra plants are abundant, several pines may be-
come infected during a season when only one existed in the
spring.
REFERENCES
Arthur, J. C., and Kern, F. D. The rediscovery of Peridermium pyri-
forme Peck. Science 38: 311-312. 1913.
Hedgecock, G. G., and Long, W. H. A disease of pines caused by Cro-
nartium pyriforme. U.S. Dept. Agr. Bul. 247: 1-20, pls. 1-2,
fe. Ie 1915:
Hedgeock, G. G., and Long, W. H. Two new hosts for Peridermium
pyriforme. Jour. Agr. Res. 5: 289-290, pl. 27. 1915.
Orton, C. R.,and Adams, J. F. Notes on Peridermium from Pennsyl-
vania. Phytopathology 4: 23-26, pl. 3. 1914.
CasTILLEJA Rust
Caused by Cronartium coleosporioides (D. and H.) Arthur
This blister-rust disease occurs from the Rocky Mountains
to the Pacific Coast Range and from Canada to Mexico. It
is exceedingly destructive to lodge-pole and western yellow
pine. Large knots and cankers are formed on lodge-pole pine
which at times are similar to the oak rust of pines (see page 287).
The trunks of many trees five inches in diameter are girdled
by the cankers, which may be from two to eight feet long. The
bark soon dies and the death of the tree or branch follows.
Fifty per cent of the stand is sometimes seriously affected.
This fungus requires the presence of the weeds, Castilleja
miniata and other species of the same genus, in the vicinity
of the pine in order to complete its development. When these
plants do not exist, this fungus cannot affect the pines.
Symptoms.
Both young and old trees are affected. Small trees in the
nursery show but little enlargement of the affected branches
or trunk. Large orange-colored blisters burst through the
286 MANUAL OF TREE DISEASES
bark, and the spores within are shed as a fine powder. The
affected limbs of older trees may show but little swelling or, as
in the case of lodge-pole pine, large knots or galls and cankers
are produced (Fig. 56). After the first
crop of blisters is formed, the bark
usually dies and the mycelium extends
its activities to the healthy bark around
the dead area. This process of en-
largement of the canker or gall con-
tinues until the limb or trunk is
girdled and death results.
On the under sides of the leaves of
species of Castilleja, small yellowish
spots appear during the summer.
Later numerous brownish bristles are
pushed out from these spots. The
appearance of the leaf is very similar
to currant and gooseberry leaves af-
fected with felt-rust (see page 277).
Cause.
The blister-rust which affects west-
ern pines and species of Castilleja is
caused by the rust-fungus Cronartium
coleosporioides (= Peridermium filamen-
tosum, the Rocky Mountain form of
Peridermium Harknessii). The life
history of this rust is similar to that
Fig. 56.—Blister-rust or of Cronartiwm ribicola described on
are rust on lodge-pole page 279. The eciospores germinate
and infect the Castilleja leaves. Ure-
diniospores propagate the fungus on this host throughout the
summer and the teliospores and basidiospores are formed in
late summer. Infection of the pine takes place in the autumn.
PINE DISEASES 287
Control.
In the western forests, the grazing animals keep the Castilleja
plants down to a minimum. Where grazing is not common,
these plants grow in large numbers and predispose the pines
to infection. All Castilleja plants should be eradicated for a
distance of a half mile around nurseries in which the species
susceptible to this rust-fungus are grown.
REFERENCES
Weir, J. R., and Hubert, E. E. A rs
s) ‘i rt 7
~ = ae
‘- ve ’
APPENDIX
ComMMON NAMES OF TREES
A usr of the common names of trees used in this manual
is given below with the scientific name opposite cach. In
most cases, the common name recommended by Sudworth * is
adopted.
Alder (general)
Alpine fir
Alpine lareh
Arbor-vite (general)
Arbor-vite (specific)
Ash (general)
Aspen
Bald cypress
Balm of Gilead
Balsam fir
Basswood (general)
Basswood (specific)
Beech
Birch (general)
Black ash
Black gum
Black jack oak
Black poplar
Black spruce
Black walnut
Box-elder
Buckeye (general)
Bur oak
Butternut
California buckeye
Carolina hemlock
Alnus sp.
Abies lasiocarpa Nutt.
Larix Lyallii Parl.
Thuja sp.
Thuja occidentalis Linn.
Fraxinus sp.
Populus tremuloides Michx.
Taxodium distichum Rich.
Populus balsamifera Linn.
Abies balsamea Mill.
Tilia sp.
Tilia americana Linn.
Fagus grandifolia Ehbrh.
Betula sp.
Frazxinus nigra Marsh.
Nyssa sylvatica Marsh.
- Quercus marilandica Muench.
Populus nigra Linn.
Picea mariana B.S. P.
Juglans nigra Linn.
Acer Negundo Linn.
Aisculus sp.
Quercus macrocarpa Michx.
Juglans cinerea Linn.
Aisculus californica Nutt.
Tsuga caroliniana Engelm.
1Sudworth, G. B. Check list of the forest trees of the United States, their
names and ranges. U.S. Dept. Agr. Div. Forestry Bul. 17: 1-144. 1898.
361
362
Catalpa (general)
Cedar (general)
Chestnut
Chestnut oak
Chinquapin °
Colorado blue spruce
Cottonwood
Coulter pine
Cuban pine
Dogwood
Douglas fir
Dwarf juniper
Eastern hemlock
Eastern larch
Elm (general)
Engelmann spruce
Kuropean chestnut
Fir (general)
Fraser fir
Grand fir
Gray pine
Green ash
Hackberry (general)
Hardy ecatalpa
Haw (general)
Hemlock (general)
Hickory (general)
Horse-chestnut
Incense cedar
Jack pine
Japanese chestnut
Jeffrey pine
Juniper (general)
Knob-cone pine
Larch (general)
Large-tooth aspen
Limber pine
Loblolly pine
Locust (general)
Locust (specific)
Lodge-pole pine
Lombardy poplar
Long-leaf pine
Maple (general)
APPENDIX
Catalpa sp.
Chamecyparis sp. and Libocedrus
sp.
Castanea dentata Borkh.
Quercus Prinus Linn.
Castanea pumila Linn.
Picea Parryana Parry
Populus deltoides Marsh.
Pinus Coulteri Lamb
Pinus heterophylla Sudw.
Cornus florida Linn.
Pseudotsuga taxifolia Brit.
Juniperus communis Linn.
Tsuga canadensis Carr.
Larix laricina (Du Roi) Koch.
Ulmus sp.
Picea Engelmanni Engel.
Castanea sativa Mill.
Abies sp. and Pseudotsuga sp.
Abies Fraseri Poir.
Abies grandis Lindl.
Pinus Sabiniana Dougl.
Fraxinus lanceolata Borkh.
Celtis sp.
Catalpa speciosa Warder
Crategus sp.
Tsuga sp.
Carya or Hicoria sp.
Aisculus Hippocastanum Linn.
Libocedrus decurrens Torr.
Pinus Banksiana Lamb.
Castanea crenata Sieb. and Zuce.
Pinus Jeffreyt
Juniperus sp.
Pinus attenuata Lemmon
Larix sp.
Populus grandidentata Michx.
Pinus flexilis James
Pinus Teda Linn.
Robinia sp.
Robinia Pseudacacia Linn.
Pinus contorta Loud.
Populus nigra italica Du Roi
Pinus palustris Mill.
Acer sp.
Monterey pine
Mountain ash (general)
Mountain juniper
Noble fir
Norway pine
Norway spruce
Nut pine
Oak (general)
Ohio buckeye
One-seed juniper
Paper bireh
Pine (general)
Pitch pine
Pond pine
Poplar (general)
Red ash
Red juniper
Red maple
Red oak
Red spruce
River birch
Rocky Mountain juniper
Sand pine
Searlet oak
Seotch pine
Serub pine
Service-berry (general)
Shasta red fir
Short-leaf pine
Silver maple
Single-leaf pine
Sitka spruce
Spruce (general)
Spruce pine
Striped maple
Sugar pine
Swiss stone pine
Sycamore
Table-mountain pine
Utah juniper
Western chinquapin
Western hemlock
Western larch
Western white pine
Western yellow pine
APPENDIX 363
Pinus radiata Don.
Sorbus sp.
Juniperus sabinoides Sarg.
Abies nobilis Lindl.
Pinus resinosa Ait.
Picea excelsa Link
Pinus edulis Engelm.
Quercus sp.
Aisculus glabra Willd.
Juniperus monosperma Sarg.
Betula papyrifera Marsh.
Pinus sp.
Pinus rigida Mill
Pinus serotina Michx.
Populus sp.
Fraxinus pennsylvanica Marsh.
Juniperus virginiana Linn.
Acer rubrum Linn.
Quercus rubra Linn.
Picea rubra Dietr.
Betula nigra Linn.
Juniperus scopulorum Sargent
Pinus clausa Sarg.
Quercus coccinea Muench.
Pinus sylvestris Linn.
Pinus virginiana Mill.
Amelanchier sp.
Abies magnifica Murr.
Pinus echinata Mill.
Acer saccharinum Linn.
Pinus monophylla Torr. and Frem.
Picea sitchensis T. and M.
Picea sp.
Pinus glabra Walt.
Acer pennsylvanicum Linn.
Pinus Lambertiana Doug}.
Pinus Cembra Linn.
Platanus occidentalis Linn.
Pinus pungens Lamb.
Juniperus utahensis Lemm.
Castanopsis chrysophylla de C.
Tsuga heterophylla Sarg.
Larix occidentalis Nutt.
Pinus monticola Dougl.
Pinus ponderosa Laws.
364
White ash
White birch
White cedar
White elm
White fir
White oak
White pine
White spruce
Yellow birch
Yellow buckeye
Yellow cedar
Yellow oak
Yellow poplar
APPENDIX
Fraxinus americana Linn.
Betula populifolia Marsh.
Chamecyparis thyoides B. 8. P.
Ulmus americana Linn.
Abies concolor Parry
Quercus alba Linn.
Pinus Strobus Linn.
Picea canadensis B. S. P.
Betula lutea Michx. f.
Zisculus octandra Marsh.
Chamecyparis nootkatensis Spach.
Quercus velutina Lam.
Liriodendron Tulipifera Linn.
SYNONYMY OF POoLYPORE NAMES
Following is a list of the polypore names used in this
manual.
Opposite each is the name applied to the same
fungus by Murrill’ in the North American Flora.
Fomes annosus Fries
Fomes applanatus Fries
Fomes Earlet (Murr.) Sace.
Fomes Everhartii (Ellis and Gall.)
Schrenk
Fomes fomentarius Fries
Fomes fraxinophilus Peek
Fomes fulvus Fries
Fomes geotropus Cooke
Fomes igniarius Fries
Fomes juniperinus Schrenk
Fomes officinalis Fries
Fomes pinicola Fries
Fomes rimosus Berkeley
Fomes roseus Fries
Fomes texanus (Murr.) Hedg. and
Long
Polyporus amarus Hedgeock
1Murrill, W. A., North American Flora, 9: 1-131.
Fomes annosus (Fries) Cooke
Elfvingia megaloma (Lev.) Murr.
Pyropolyporus Earlet Murr.
Pyropolyporus Everhartii (Ell. and
Gall.) Murr.
Elfvingia fomentaria (L.) Murr.
Fomes fraxinophilus (Peck) Sace.
Pyropolyporus fulvus (Seop.)
urr.
Pyropolyporus igniarius (L.)
Murr.
Pyropolyporus juniperinus
(Schrenk) Murr.
Fomes laricis (Jaeq.) Murr.
Fomes ungulatus (Schaeff.) Saee.
Pyropolyporus Robinie Murr.
Fomes roseus (Alb. and Sehw.)
Cooke
Pyropolyporus tecanus Murr.
1907.
APPENDIX 365
Polyporus Berkeleyi Fries Grifola Berkeleyi (Fries) Murr.
Polyporus borealis Fries Spongipellis borealis (Fries) Pat.
Polyporus betulinus Fries Piptoporus suberosus (L.) Murr.
Polyporus croceus Fries Aurantiporus Pilote (Schw.)
Murr.
Polyporus dryadeus Fries Tonotus dryadeus (Fr.) Murr.
Polyporus Ellisianus (Murr.) Long Tryomyces Ellisianus Murr.
Polyporus frondosus Fries Grifola frondosa (Dicks.) S. F.
Gray
Polyporus obtusus Berkeley Spongipellis unicolor (Schw.)
Murr.
Polyporus Rheades Fries Tonotus dryophilus (Berk.) Murr.
Polyporus Schweinttzii Fries Pheolus sistotremoides (Alb. and
Schw.) Murr.
Polyporus squamosus Fries Polyporus caudicinus (Secop.)
Murr.
Polyporus sulphureus Fries Letiporus speciosus (Batarr.)
Murr.
Trametes pint Fries Porodedalia pint (Thore) Murr.
Trametes suaveolens Fries Trametes suaveolens Fries
GLOSSARY
Acervulus (acervuli). Open, saucer-shaped, asexual fruiting-body.
fEciospore. One of the types of spores formed by the rust-fungi.
AXfciospores are produced in the blisters on conifers in the case
of the blister-rusts. The juniper and cedar rust-fungi form
zeciospores on the pomaceous host.
Ascospore. Sexually formed spores which are borne within a sac
ealled an ascus. The asci are in turn borne on or in various
types of fruiting-bodies.
Ascus (asci). Sac-like structures containing ascospores. Asci are
borne in open or closed fruiting-bodies. Perithecia contain asci.
Bacterium (bacteria). Small, microscopic plants. Plants consist
of single cells, which may be motile. Parasitic forms cause in-
fectious diseases of plants and animals.
Basidiospore. Short lived spores borne on germ-tubes of teliospores
in the rust-fungi. They are forcibly discharged and are carried
by the wind.
Cambium. Region of growth in a woody stem or root, at which wood
is formed on the inside and bark on the outside.
Canker. A dead area of bark.
Chlorophyl. The green coloring material produced in the leaves of
the higher plants. Chlorophyl is instrumental in making starch
from carbon dioxide gas and water.
366 APPENDIX
Enzyme. A complex chemical compound capable of causing the
transformation of certain organic substances into substances of
greater or less complexity without itself entering into the product.
Epiphytotic. A plant disease which assumes an unusual and generally
destructive nature in a locality. Usually called an epidemic,
which term refers only to human diseases.
Fruiting-body. Large or small, open or closed structures made of °
mycelium in which the spores of fungi are formed.
Fungus. Simple plants lacking chlorophyl. Consisting of mycelium
which may be massed to form large fruiting-bodies. Fungi
obtain food by decomposing living or dead plant and animal tissue.
Fusiform. Spindle-shaped.
Germ-tube. A short tube which grows from a viable spore. The
germ-tube then branches and a new mycelium is formed if growth-
conditions are suitable.
Gill. The pendent plates or lamella found on the under side of
toadstools. The spores of the fungus are borne on the sides of
the gills.
Haustorium (haustoria). Special branch of the mycelium which is
pushed into a cell to obtain food-materials.
Heartwood. The wood at the center of a tree, which contains no
living cells and serves only for support.
Heterecious. Said of a parasitic fungus which requires more than
one kind of host for the completion of its life history.
Host. Any plant in which a parasite grows.
Hypertrophy. Enlargement of a portion of a plant, as galls on limbs.
Hypha (hyphex). Individual branches of the mycelium of a fungus.
Infect. Said of a parasitic organism when it succeeds in establish-
ing parasitic relations with a host-plant.
Infection. The act of infecting, see above.
Infection court. Any place or area of a host-plant where infection
occurs. Also said of any place where infection is possible.
Lesion. Any definitely diseased area in which the primary cause of
the disease is present.
Mycelium (mycelia). The vegetative body of a fungus, made up of
long threads containing protoplasm.
Parasite. An organism which lives in or on another living organism
for the purpose of obtaining food-materials.
Parenchymatous. Tissue composed of thin walled cells which are
capable of further differentiation.
Pathogene. Any factor which causes disease, usually restricted to
living organisms which live parasitically.
Perithecium (perithecia). A closed globose or flask-shaped fruiting-
body containing asci and ascospores. Spores usually forcibly
discharged.
APPENDIX 367
Protoplasm. Living substance within the cells of plants and animals.
The seat of growth and many other functions which are charac-
teristic of living things.
Pycnidium (pyenidia). An ineclosed globose or flask-shaped fruit-
ing-body containing simple asexual spores.
Rhizomorph. A compact bundle of mycelium arranged parallel to
form a root-like structure. See shoe-string root-rot, page 78.
Saprophyte. A living organism which obtains its food-materials
from dead organic material. See Parasite.
Sapwood. The wood between the heartwood and bark. Sapwood
contains living cells and is the tissue which is active in translo-
eating food-materials to all parts of the tree.
Sclerotium (sclerotia). A compact, more or less globose structure
made of closely aggregated mycelium. Usually a resting body
rich in stored food.
Spore. A portion of the mycelium which is detached and serves as
a propagative or reproductive body, corresponding to the seeds
of higher plants. Spores may be formed sexually or asexually.
Stomate. Specialized structures with an opening in the center, found
on the surface of leaves. Stomates open and close and regulate
the exchange of gases and water vapor between the interior of
the leaf and the surrounding atmosphere.
Stroma (stromata). Compact aggregation of mycelium forming a
fungous layer. Fruiting-bodies may be formed imbedded in the
stroma.
Teliospore. A type of spore formed by the rust-fungi. All rust-
fungi form teliospores and basidiospores. They may omit any
one or all of the other stages. Teliospores in many species over-
winter. When they germinate they form basidiospores directly.
Urediniospore. A type of spore formed by the rust-fungi. These
spores are produced in summer and serve to distribute the fungus
rapidly during the growing season. Urediniospores are usually
produced from mycelium that originated from sciospore infec-
tion. Later teliospores are formed from the same mycelium.
GENERAL BIBLIOGRAPHY OF TREE DISEASES
AMERICAN PUBLICATIONS
Atkinson, G. F. Studies of some shade tree and timber destroying
fungi. Cornell Univ. Agr. Exp. Sta. Bul. 193: 199-235, figs.
56-94. 1901.
Cook, M. T. Diseases of shade and forest trees. Jn The planting
and care of shade trees. Forest Park Reservation Commission
of New Jersey, pp. 93-124, figs. 36-43. 1912.
368 APPENDIX
Cook, M. T. The diseases of tropical plants, pp. 1-317, figs. 1-85.
1913.
Duggar, B. M. Fungous diseases of plants, pp. 1-508, figs. 1-240.
1909.
Freeman, EK. M. Minnesota plant diseases, pp. 1-482, figs. 1-211.
1905.
Galloway, B. T., and Woods, A. F. Diseases of shade and ornamental
trees. U.S. Dept. Agr. Yearbook 1896: 237-254, figs. 53-57.
1897.
Harshberger, J. W.