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Bulletin 412

July, 1938

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A SURVEY OF DISEASES AND DEFECTS
IN CONNECTICUT FORESTS

Raymond Kienholz and C. B. Bidwell

(Uomtettftut
(Agrtotlitfrai ^xptxbmxd JStatum

CONTENTS

Introduction 493

Methods 493

Description of Forests Examined 498

Area Covered 498

Species Composition 498

Frequency Distribution of Species 507

Results 508

Nectria canker 509

In relation to host species 510

Frequency distribution 515

Location of cankers 518

Number per tree 520

Fruiting 523

Avenues of entrance 523

Effect on host 524

In relation to age of trees 525

In relation to diameter of trees 527

In relation to crown class of trees 528

In relation to origin of trees 529

In relation to forest type 529

In relation to density of stand 529

In relation to age of stand 531

In relation to plot exposure 531

In relation to site quality 531

Discussion 532

Control measures 534

Strumella canker 535

Decay of living trees 538

Frost cracks 543

Top Damage 549

Mechanical Injuries 550

Miscellaneous Lesions 550

Borer Injury 550

Fire Scars 550

Discussion 551

Summary 554

Literature References 559

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A SURVEY OF DISEASES AND DEFECTS
IN CONNECTICUT FORESTS

Raymond Kienholz and C. B. Bidwell

The present condition of the forest stands of Connecticut is the result
of hundreds of years of misuse. Successive clear cuttings for charcoal
and fire wood have caused deterioration of both the stand and the site.
Logging has been carried on with little regard for the future stand. The
desirable trees have been cut, taking everything if the stand was good,
or, if poor, leaving the undesirable species and the deformed and rotten
trees. The added disaster of chestnut blight has further depleted the
growing stock. As a result the stands are understocked and contain
many undesirable trees.

Since most of the state owned forests have been planted with conifers
wherever there were open areas, the chief silvicultural problem facing the
Civilian Conservation Corps in 1933 was that of improving existing stands.
These are largely composed of hardwoods or hardwoods in mixture with
softwoods in the younger age classes. The task of choosing crop trees
brought to light the prevalence of Nectria cankers and other diseases and
defects.

In the winter of 1934-35 a survey of disease conditions in Connecticut
forests was started. The purpose of this survey was to determine (1) the
kind, abundance and distribution of diseases and defects in the forests of
the State and (2) the effect of species, composition, age and other stand
and site characteristics on the prevalence of diseases and defect* The
results indicate the present condition of the stands examined and should
serve as a basis for determining (a) the best method for reducing damage
from diseases and defects in the present stands and (b) by comparison with
future studies, the degree of effectiveness of present treatments in lessen-
ing damage.

METHODS

A type map of each of the four forests examined served as the basis for
the survey. (Figure 86). Roads, trails and boundary lines were used as
rough base lines from which at intervals of about 700 feet cruise lines were
run out at right angles. At intervals of about 700 feet along these cruise
lines tenth-acre plots were laid out. No attempt was made to locate these
cruise lines or these plots exactly 700 feet apart but the object was rather
to include the different forest types in the same proportion in which they

* Dr. Kienholz was formerly a member of the Forestry Department at the Experiment Station at
New Haven. The investigations reported here, however, were carried on under State Forester A. F. Hawes.
Since the State and Station departments work together on many projects, Dr. Kienholz retains an office
at the Station and cooperates in several problems

494

Connecticut Experiment Station

Bulletin 412

existed in the forest as shown by the type map. (Figure 87). The success
with which this was done is shown in Table I in which the percentage of
plots located in the different forest types is shown in comparison with the
acreage (percent) actually in those types as determined from the type
map.

Figure 87. Type map of compartment 8, Hartland Hollow Block, Tunxis Forest.
Type symbols and location of plots shown by number (434-441 and 449-457). The
percent below each plot represents the number of trees bearing one or more Nectria
cankers.

Acknowledgments: The Survey was started late in 1934 by R. C. Lorenz, technician E. C. W. Divi-
sion of Forest Pathology, and Thad J. Parr, then project superintendent E. C. W., Connecticut. It was
taken over in March, 1935, by the senior author who gave the project general supervision, worked up the
data and wrote the manuscript. The junior author supervised the field work and assisted wth the manu-
script. The entire work was carried out as a project of the Emergency Conservation Work and Civilian
Conservation Corps. Perley Spaulding, Division of Forest Pathology, identified fungi and read the manu-
script. T. J. Grant, E. C W. Division of Forest Pathology, was very helpful in criticizing the manuscript,
particularly regarding Nectria. State Forester A. F. Hawes, Connecticut, and J. S. Boyce, Yale University,
criticized the manuscript. W. G. Mayer, D. J. Falvey, A. J. Hunyadi and W. C Spellman carried out the
field work. W. C Spellman and O. A. Kelsey did very effective work in the field and in the laborious task
of summarizing the data. The authors are under the deepest obligation to these men, without whom the
survey would have been impossible. To W. L. Slate, director, and W. O. Filley, forester, Connecticut
Agricultural Experiment Station, and A. F. Hawes, State forester, grateful acknowledgment for permission
to publish.

Methods 495

Table I. Plots Laid Out Compared with Acreage by Forest Types

Designation

Old
Field

(percent)

Swamp
(percent)

Oak

Ridge

(percent)

Mixed

Hardwoods

(percent)

Softwood-
Hardwood
(percent)

Softwood
(percent)

Planta-
tions
(percent)

Total
(percent)

Plots

4.3

3.4

4.0

73.1

14.5

0.7

0

100

Acreage

7.5

3.5

2.3

65.3

12.9

0.2

8.3

100

Deviation

-3.2

-0.1

+1.7

+7.8

+1.6

+0.5

-8.3

0

The forest types were sampled in practically the same proportion in
which they existed in the forest. This was true for each one of the four
forests sampled as well as the average of the four forests. There was a
tendency to lay out proportionately fewer plots in the old field type and
in the plantations than exist in nature. This was due to the small value
and transient character of the old field type and the lack of sizeable trees
in the plantations. Conversely, a larger proportion of plots was laid out
in the mixed hardwoods type.

A comparison of the proportion of plots laid out in each age class also
showed a very close agreement with the actual acreage found in the forests.

Although no hard and fast system of cruise lines and plot locations was
followed, the authors are convinced that the results give as true a picture
of the conditions in the areas sampled as time limitations permitted.

A typical portion of a type map with the plot locations is shown in
Figure 87.

Forest Types

The forest types as recognized in Connecticut State Forests are as
follows :

DESCRIPTION

chiefly gray birch or red cedar with other species
coming in on abandoned fields or pastures.

chiefly red maple and yellow birch on wet soil.

chiefly scarlet and chestnut oaks on dry shallow-
soiled ridges.

either "northern hardwoods"; beech, birch and
maple, or "southern hardwoods"; red oak, ash,
maples, basswood, birches, tulip, oaks and
hickories — a frequent and abundant forest type.

SYMBOL

NAME

OF

Old Field

S

Hardwood Swamp

o

Oak Ridge

MH Mixed Hardwoods

SH

Softwood — Hardwood

SW Softwood

a mixture of softwood and hardwood species
ranging from 20 percent of the one and 80 per-
cent of the other, to 80 percent of the one and
20 percent of the other.

chiefly hemlock, pine or southern white cedar
making up over 80 percent of the stand with
or without hardwoods in mixture.

496 Connecticut Experiment Station Bulletin 412

SYMBOL NAME DESCRIPTION

P Plantation chiefly coniferous planting — most of it done in

recent years.

AGE CLASSES

I— 0—20 years

' 11—21—40 years

III — 41 — 60 years

IV— 61— 80 years

A — All ages

YIELDS PER ACRE:

1— 0—2000 Board Feet
2—2000—5000 Board Feet
3— 5000— plus Board Feet

CROWN DENSITY

0 . 0 — 1 . 0 from open to a complete canopy.

A symbol, l' , , means that the stand is of the mixed hardwoods

type, with a yield of from 0 to 2000 board feet per acre, is 21 to 40 years
old and has a crown density of 0.7 of complete canopy.

All plots were .1 acre in area, 66 feet square and were laid out at the
rate of one plot for each 11 acres sampled. Quarter-inch rope with knots
at 66-foot intervals was used to determine the bounds of the plot. The
angles were laid out with a hand compass. Corner trees were marked with
a band of white paint and on one of them the plot number was painted for
possible future relocation. Rope was then trailed back and forth across
the plot dividing it into lanes 15 to 20 feet wide. These narrow lanes
made possible the tallying and examination of each tree on the plot without
the 'danger of duplication or omission. All stems one inch D.B.H. and
larger were carefully examined for disease and defect and the diameter
breast high, crown class and species of all trees were recorded. The age
and height of one tree from each of the dominant, codominant and inter-
mediate crown classes were obtained. A form sheet was filled out for
each plot giving general as well as specific information. (Figure 88).

The field work was carried out by foremen trained in forestry, using
one or two crews of two or three men each. At intervals the work of each
foreman was checked in the field by the junior author for accuracy and
completeness of both field work and records. This supervision assured
a uniformly high quality of work, particularly on the four forests inten-
sively surveyed: Tunxis, Pachaug, Meshomasic and Cockaponset. At
the close of the field work the data sheets and maps from each forest were
assembled, and the tabulation of the data and the preparation of the
manuscript was done at one central office.

Some of the earlier work was not sufficiently detailed to be used in
all tabulations. The species composition and the percentage Nectria
cankered was determined on 12 forests (Figure 86), 20,460 acres being
sampled with 1852 plots. All other results are based on data from 1256
plots, covering 13,780 acres on the four forests, or on only one of these
forests.

Methods

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498 Connecticut Experiment Station Bulletin 412

DESCRIPTION OF FORESTS EXAMINED

AREA COVERED

The four forests intensively examined are located over the State in such
a way that they are fairly representative of the State as a whole. (Figure
86) . About 75 percent of the Tunxis and Meshomasic forests was covered
by the survey and about 25 percent of the Pachaug and Cockaponset
forests. One plot was laid out for each 11 acres of area examined. The
total number of trees examined was 98,420, on 1256 tenth-acre plots.
(Table II).

Table II. Area Covered by the Disease Survey

Forest

Area Examined
(acres)

One plot per
(acres)

Number plots
examined

Number trees
examined

Tunxis

4480

12

376

29,421

Pachaug

2500

12

214

19,419

Meshomasic

4300

10

419

32,356

Cockaponset

2500

10

247

17,224

TOTALS— AVERAGE

13,780

11

1,256

98,420

SPECIES COMPOSITION

The number of trees one inch D.B.H. and over, found on the plots ex-
amined, averaged 784 per acre. There was some variation among the
different forests:

Pachaug 907 per acre Meshomasic 772 per acre

Tunxis 782 per acre Cockaponset 697 per acre

The statement is made (Hawes 1933) that there are no fully stocked
natural forests in Connecticut due in most cases to the death of the chest-
nut. Just what is full stocking in Connecticut forests is difficult to deter-
mine, since it varies with age, species and site quality. The figures given
above are based on all forest types and age classes, hence they represent
the average condition found on the state forests sampled. Although the
older age classes may be understocked, the outlook for better stocking in
the future is good. The average basal area per acre for all forests was 81.1
square feet with the four forests ranging as follows :

Tunxis 106 . 8 sq. feet per acre Meshomasic 66 . 8 sq. feet per acre

Cockaponset 87 . 4 sq. feet per acre Pachaug 56 . 8 sq. feet per acre

The average D.B.H. of all trees examined, determined by the basal
area method, was 4.4 inches. The average for each forest was:

Tunxis 5 . 0 inches Meshomasic 4 . 0 inches

Cockaponset 4 . 8 inches Pachaug 3 . 4 inches

Heights are discussed under site quality, and age under Nectria canker
in relation to age.

Description of Forests Examined 499

By Basal Area

The species composition of the stands examined on the four forests is
shown in Table III. The average of the four forests indicates that red
maple is the species having the greatest basal area, forming 17.1 percent of
the stand. It is followed by red oak with 11.0 percent, hemlock 10.3 per-
cent, and white oak 10.0 percent. (Figure 89). Red maple, however, is
not the most abundant species on any single forest; hemlock, scarlet oak,
red oak, and white oak being most abundant on the Tunxis, Pachaug,
Meshomasic and Cockaponset forests respectively. The species have been
divided into two groups: Large Tree Species which grow to large size
and most of which are of lumber or cordwood value ; Small Tree Species
which are small trees of little or no lumber or cordwood value, many of
which are considered as weed trees.

The basal area of that part of the population eight inches D.B.H. and
over, expressed as percent of the total basal area for that species, is given
in Table III and in Figure 89. This varies from 59.2 percent on the Tunxis
with its abundance of large hemlock to 34.2 percent on the Pachaug. The
average for the four forests was 51.2 percent. The Small Tree Species
form a small proportion of the stands in each forest and they naturally
have few or no trees in the eight-inch and over D.B.H. class.

The oaks form a large part of the stands in the three southern forests,
while maples, birches and softwoods form a large part of the stands in the
northern forest (Tunxis). On the four forests 36.1 percent of the basal
area of the stands was formed by oaks, with maples 19.6 percent, birches
15.3 percent and softwoods 12.7 percent in the order named. These four
groups form 83.7 percent of all the stands examined.

2The common names and scientific names of trees and shrubs as they are used in this Bulletin are
listed on page 558. The authorities for these names are according to Sargent's "Manual of the Trees of
North America," 2nd edition, 1921, for the trees; and Gray's "New Manual of Botany," 7th edition, 1908,
for the shrubs.

500

Connecticut Experiment Station

Bulletin 412

PER CENT

5 PECIES

2 4 6 6 10 12 14 It IB

RED MAPLE
RED OAK
HEMLOCK
WHITE OAK
SCARLET OAK
BLACK BIRCH
BEECH
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Figure 89. Species composition of the four forests — Basal Area. The entire bar
represents the percentage of the population made up of the species indicated. The black
part of the bar represents the proportion (percent) of the basal area in trees under
8 inches D.B.H. The white part of the bar and the figure in it represents the pro-
portion (percent) of the basal area in trees 8 inches and over D.B.H.

Description of Forests Examined

501

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Red Oak
Hemlock
White Oak
Scarlet Oak
Black Birch
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Chestnut Oak
Black Oak
Hickory
Sugar Maple
White Ash
White Birch
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White Pine
Tulip
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White Cedar
Pin Oak

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Connecticut Experiment Station

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Alder
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Pin Cherry
Miscellaneous
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Description of Forests Examined 503

By Number of Steins

Although forest composition by basal area gives one a clearer picture
of the size and number of the different species, the number of stems is of
greater importance from the standpoint of incidence of disease and defect.
Considering the number of stems one inch D.B.H. and larger of each
species, red maple is definitely the most abundant, forming 20.6 percent of
all the stems examined. (Figure 90). Moreover it leads in each forest
except the Pachaug, where white oak is somewhat more abundant, due to
a large number of small white oak stems even in older stands. The Small
Tree species form a larger proportion of the forests, in number 4.0 per-
cent, than in basal area, 1.2 percent.

The actual number of stems examined of each species is also given in
Table IV as a basis for comparing one forest with another, but chiefly so
one may have a basis for judging the value of observations concerning
any given species. In every case in this bulletin where any information
about a species is given, whether it be the number of Nectria cankers, the
number of frost cracks, the number of broken tops or the number of de-
cayed trees, the number of trees examined to secure that information is
given in Table IV. Thus, for example, any information based on the
examination of 20,309 stems of red maple is of more value than that based
on the examination of 36 black ash or 17 mountain maple. Similarly any
statement based on 277 white oak examined on the Tunxis is less reliable
than one based on the examination of 4,874 white oak on the Pachaug.
The number of stems examined will not be repeated in subsequent tables
but unless otherwise stated these figures will apply to data throughout the
bulletin.

504

Connecticut Experiment Station

Bulletin 412

5 P ECIES

%

PERr CENT

5 10 IS 20 25 30
.... i .... 1 .... i .... I .... i .... 1 ... .

RED MAPLE
WHITE OAK
RED OAK
BLACK BIRCH
SCARLET OAK
GRAY BIRCH
HEMLOCK
HICKORY
YELLOW BIRCH
BEECH
SUGAR MAPLE
WHITE ASH
CHESTNUT OAK

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S PECIES

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PER CENT

Figure 90. Species composition of the four forests — Number of stems; also percent
of total population Nectria cankered. The entire bar represents the percent of the
total population made up of the species indicated. The black part of the bar and
the figure to the left represent, the percentage of the total population made up of the
Nectria cankered individuals of the species indicated. The asterisk means less than
0.1 percent.

Description of Forests Examined

505

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506

Connecticut Experiment Station

Bulletin 412

9

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Percent
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Small tree species :

Hop Hornbeam
Blue Beech
Scrub Oak
Dogwood
Striped Maple
Alder
Shadbush
Pin Cherry
Mountain Maple
Misc. Hardwoods

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Oaks
Maples
Birches
Softwoods

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Description of Forests Examined 507

There was considerable variation between the different forests, partic-
ularly the Tunxis Forest and the Pachaug Forest. The Tunxis had a
large proportion of maples, 34.3 percent, birches 20.9 percent and soft-
woods 16.6 percent, characteristic of the northern hardwood, beech-birch-
maple forest with a mixture of hemlock. The other three forests, partic-
ularly the Pachaug, are characteristic of the southern hardwood type with
an abundance of oaks, 52.5 percent, and a small number of maples, 18.6 per-
cent, birches 11.5 percent and softwoods 4.0 percent. Hickory likewise was
scarce on the Tunxis, 0.2, compared with the Pachaug, 4.6. Beech was
abundant on the Tunxis, 8.2, and not on the Pachaug, 1.4. Striped maple
and mountain maple were restricted to the Tunxis. It must be borne in
mind that the absence of a species or a disease or defect from any of the
forests is not necessarily indicative of the fact that it does not exist in that
forest, but only that it has not been encountered on the plots examined,
which are but a small proportion of the total area covered in the survey.
However, since the number of plots on each forest was quite large and
they are distributed uniformly over the area sampled, the distribution
given is indicative of the actual abundance of all but the rarer species.

This variation in species composition from forest to forest must be con-
sidered in determining the amount of Nectria and Strumella infection and
the treatment that can best be applied.

The species composition of the twelve forests examined was tabulated
and found to be so similar to that of the four forests presented in Table IV
that it has been omitted. This similarity indicated that the averages for
the four forests are quite representative of the State as a whole.

FREQUENCY DISTRIBUTION OF SPECIES

The number of plots, out of the total of 1256 examined, on which each
species occurred, was determined and expressed as a percentage frequency
figure. This percentage frequency is shown in Table V. A high percent-
age means wide general distribution throughout the forest.

Red maple was present on the greatest number of plots, 91 percent,
followed by red oak with 71 percent, white oak 67 percent, black birch
with 65 percent and hickory, 47 percent. White ash, 42 percent, was
present on a larger number of plots than might have been expected from
its relative scarcity. It is, however, widely and generally distributed,
though not in quantity.

At the other end of the scale, occurring on only a few plots, were elm
3 percent, butternut 4 percent, red cedar 6 percent, and white pine 8 per-
cent.

508 Connecticut Experiment Station Bulletin 412

Table V. Percent Frequency of Occurrence of Species

Number

Per-

Number

Per-

plots

cent

plots

cent

SPECIES

species

of

SPECIES

species

of

occurred on

total

occurred on

total

Large tree species:

Red Maple

1149

91

Pepperidge

100

8

Red Oak .

891

71

Basswood

99

8

White Oak

840

67

White Pine

95

8

Rlack Birch

813

65

Red Cedar

74

6

Hickory

594

47

Butternut

49

4

White Ash

524

42

Elm

40

3

Yellow Birch

490

39

Pitch Pine

32

3

Scarlet Oak

472

38

Miscellaneous

12

1

Gray Birch

441

35

Black Oak

429

34

Small tree species:

Sugar Maple

338

27

Hop Hornbeam

163

13

Beech

337

27

Blue Beech

136

11

Hemlock

320

26

Dogwood

127

10

Black Cherry

290

23

Striped Maple

85

7

Chestnut Oak

221

18

Shadbush

54

4

Sassafras

213

17

Scrub Oak

45

4

Aspen

209

17

Alder

43

3

White Birch

196

16

Miscellaneous

24

2

Tulip

157

13

Pin Cherry

13

1

Miscellaneous Large Tree Species are black ash, pin oak, white cedar and spruce.
Miscellaneous Small Tree Species are mountain maple, sumac, witch hazel, willow, apple, black
walnut and sycamore.

RESULTS

The result of examining 98,420 trees in four forests of the State was a
fuller knoAvledge of the kind, abundance and species incidence of the vari-
ous diseases and defects found in the forest than has ever been available
heretofore. Since Nectria cankers were so abundant, on 5721 living trees,
particular attention was paid to this disease and its characteristics. Its
relation to its hosts, its relation to the stand and to the site were studied.
It was found on a larger number of trees than any other disease or defect.

Strumella cankers, decay, frost cracks, top damage due to ice storms
and drought, mechanical injuries due to logging and rubbing, miscellaneous
lesions, borer injury, fire scars and other minor types of injury were found
and are discussed in the following pages.

All diseases and defects that could be noted by observation of the living
trees were recorded. No cultures nor dissections were made, hence some
of the obscure and non-typical cases of Nectria or Strumella may have
been overlooked. Likewise the extent of decay could only be judged from
outward appearance. Probably much decay was not visible from the out-
side and could only have been detected by dissection. Such a dissection
study would be desirable. No defects in the form of the bole, such as lean,
crook, sweep, limbiness or crotch were recorded.

Particular emphasis has been placed on the relation of disease or defect
to species. Data referring to the abundance of a disease or defect on a
given forest is chiefly of limited and local value. Data referring to species,

Results 509

however, is of more general value and application since it can be used in
Connecticut or in nearby localities in proportion as that species occurs in
the forest under consideration.

In tabulating the data, an individual tree was recorded as having
Nectria but once even though it had more than one Nectria canker on it.
But if it had Nectria and also a broken top, it was recorded under each
defect. Thus the summation of all diseases and defects will be too high
because of the duplications recorded. The amount of this duplication was
not great, however, averaging 3.0 percent for all the forests. That is, on
the 17,665 trees having defects, there were 21,727 diseases or defects re-
corded. Most of the trees had but one defect while a small number had
two, three or even four.

The results here recorded are based on large numbers of trees examined
and large numbers of defects encountered. Their chief value lies in giving
a dependable picture of average conditions over a wide area in the several
forest types and age classes as they exist in the forests of Connecticut.
As the tabulation of results progressed, it was often evident that if only
one forest had been examined some very plausible and attractive theories
could have been formulated. With a larger amount of information, ap-
parently good explanations for conditions in one forest were exploded by
data from another. Hence if the conclusions here given are sometimes
tentative and qualified, it is because the abundance of data makes a cau-
tious statement advisable rather than too small an amount making it
necessary.

Averages in all cases are based on the actual numbers involved and are
never the average of averages. That is, all averages are weighted averages.
Hence, in a table such as Table XVI, the average for the four forests for
black oak, as an example, is based on the actual percent of that species
examined, which were diseased, rather than on a straight average of the
sum of 2.3, 0.3 and 3.2.

Unless otherwise stated in the legends and captions, all figures and tables
are based on data from 1256 plots on four forests.

NECTRIA CANKER

The cankers on various hardwood species caused by Nectria coccinea
and other species of Nectria vary widely in appearance. The typical ap-
pearance is a round or oval sunken pit with flaring edges of broken bark
and rolls of callus tissue. The bare wood exposed in the middle of the
canker usually shows concentric ridges or layers where the cambium has
been killed back by the slow and intermittent advance of the fungus.
These ridges are concentric around a central area which is usually the re-
mains of a dead branch stub through which the fungus probably gained
entrance to the stem. The shape of the cankers varies from greatly elon-
gated forms sometimes occurring on maple, through oval forms on bass-
wood, to forms which are much wider than high and resemble wire fence
injury. This last is characteristic of scarlet oak. Sometimes the cankers
are covered either by callus growth (Grant 1936) as often happens in sugar

The scientific names and authorities for the various species of fungi rrentiend in 1 his Ful.'clin ere
according to Boyce, J. S., Forest Pathology, McGraw-Hill, New York, 1938, atd will ret he listed here.

510 Connecticut Experiment Station Bulletin 412

maple, or by dead bark as in black and yellow birch. The fruiting bodies,
when present, are reddish, rounded structures the size of a pinhead, scat-
tered around the edges of the canker. The presence of fruiting bodies
positively identifies the canker as Nectria, but in most cases fruiting
bodies are not present. Many cases were encountered in the field where
no fruiting bodies were found. If these cases looked like Nectria cankers,
based on the experience of the foreman in charge of the crew and also of
the supervising technician, they were so classified.

Nectria Canker in Relation to Host Species
Percentage of Species Cankered

The frequency with which various hardwood species are infected with
Nectria canker varies with the locality. Welch (1934) reports heavy in-
fections of basswood in parts of New York, yellow and black birch in Ver-
mont, paper birch in New Hampshire and red and black oak in Connecticut.
Black walnut is frequently infected in Virginia, Ashcroft (1932). Spaulding
et. at. (1936) list as commonly cankered in New England: red maple,
yellow birch, sweet (black) birch, and to a lesser extent gray birch, paper
(white) birch, sugar maple, mountain maple, red oak, black oak and large-
toothed aspen. He lists the following species as not commonly cankered:
white ash, white oak, American elm, hickory, basswood and scarlet oak.

The number of trees of each species infected with Nectria cankers found
in the four forests is given in Table VI and Figure 91. There is some
variation within a species between the different forests but if the relative
ranking of the species in each forest is observed it will be seen that the
average for the four is fairly consistent. Thus pepperidge ranks 1, 3, 4, 1
on the four forests, black birch 3, 1, 1, 5, and sassafras 8, 4, 2, 2. Here, as
elsewhere in this bulletin, the average for the four forests is a weighted
average.

Red maple, 5.7 percent, does not appear to be cankered as frequently as
Spaulding (1936) suggests. It should be moved down in the list next to
sugar maple. Its abundance in the stand, hence the frequency with which
its cankers are encountered, as discussed under Percent Total Stand Can-
kered, probably accounts for its being considered so heavily infected.
Mountain maple, 58.8 percent, was found on the Tunxis only and in small
numbers, hence its high percentage of Nectria infection may not be char-
acteristic of the species farther north. Black birch is heavily infected,
15.4 percent, in all forests. Scarlet oak is frequently cankered, 9.6 per-
cent, in the three forests in which it occurs. It ranks close to black oak,

9.1 percent, and should be moved up next to it. Red oak, on the other
hand, is not frequently cankered, 2.3 percent, and ranks near white oak,

1.2 percent. Rasswood is moderately cankered, 5.4 percent. Variations
among the four forests in amount of infection of the different species are
evident, but for Connecticut the ranking of the species given in Table VI
is believed to be representative of the State as a whole.

Nectria Canker

511

5 PEC IE S

PER/0CENT ZQ 3Q 4Q SQ

......... i 1....1....1 .,..i.... i — i ... . r.

K

PEPPERIDGE
BLACK BIRCH
SASSAFRAS
GRAY BIRCH
BLACK CHERRY
SCARLET OAK
BLACK OAK
YELLOW BIRCH
WHITE BIRCH
ASPEN
RED MAPLE
SUGAR MAPLE
BAS S WOOD
BLACK ASH
HICKORY
ELM

RED OAK
WHITE OAK
WHITE ASH
BEECH
TULIP

CHESTNUT OAK
PIN OA K
BUTTERNUT

1
I
1

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MT. MAPLE
DOGWOOD
STRIPED MAPLE
ALDER
SHADBUSH
PIN CHERRY
BLUE BEECH
HOP HORNBEAM
SCRUB OAK
MISCELLANEOUS

1

I

I

a.

BIRCHES
MA PLES
OA KS

Figure 91. Number of trees of each species (in percent) infected with Nectria canker.

512

Connecticut Experiment Station

Bulletin 412

6

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514 Connecticut Experiment Station Bulletin 412

A most striking fact is brought out in Figure 91. The so-called weed
species such as mountain maple, dogwood and striped maple are frequently
infected and, although they make up only a small proportion of the total
stand, they can form a source of inoculum which may help to infect more
valuable species. Hence they should, wherever practicable, be removed
in the course of improvement cuttings.

Considering the species groups, the birches are most frequently infected,
12.5 percent, ranking in the order black, gray, yellow and white. Maples
are less frequently infected, 6.1 percent, ranking in the order mountain,
striped, red and sugar; while oaks are least infected, 3.6 percent, ranking
in the order scarlet, black, red, white, scrub, chestnut and pin. Softwoods
are not attacked.

In addition to the list of genera infected by Nectria given by Welch
(1934) the present study has added Cornus, Alnus, Hamamelis, Salix and
Platanus.

Percentage of Total Stand Cankered

In the above paragraphs the number, in percent, of the individual trees
of each species which had one or more cankers was discussed. This varied,
for example, from 58.8 percent in the case of mountain maple with 10
cankered trees out of 17 individuals examined, to 5.7 percent in the case of
red maple with 1157 cankered trees out of 20,309 individuals examined.
Because of the extreme variation in the abundance of the different tree
species, which variation has no relation to how frequently they are can-
kered, a truer picture of the actual abundance of the cankered trees in
relation to the total population, or stand, examined can be obtained by
determining the "percentage of the total stand cankered". Thus red
maple with 1157 cankered trees out of a total population of 98,420 trees
examined has a percent total stand cankered of 1.2 percent, whereas moun-
tain maple with 10 cankered trees out of a total population of 98,420 has
less than 0.1 percent total stand cankered. This total is recorded in Table
VI and the averages are shown graphically in Figure 90.

Cankered trees of red maple form 1.2 percent of the entire number of
trees examined (total stand) while cankered black birch forms 1.1 percent,
followed by gray birch 0.7 percent, scarlet oak 0.5 percent, yellow birch
0.4 percent, sassafras 0.2 percent, black oak 0.2 percent, sugar maple 0.2
percent, red oak 0.2 percent, and white oak 0.2 percent.

The Small Tree Species are usually present in such small numbers
that although they are heavily infected they usually form less than 0.1
percent of the cankered trees encountered. Dogwood 0.2 and striped
maple 0.1 are somewhat higher.

Therefore the Nectria cankers most frequently encountered in the
average forest are on red maple and black birch. That is, out of 100
cankered trees encountered in the average Connecticut forest 20 would
be red maple and 18 would be black birch; the remainder would be scat-
tered among several species.

The cankered birches made up 2.3 percent of the total stand, maples
1.5 percent and oaks 1.1 percent, or 4.9 percent out of the total of 5.8 per-
cent for all species.

Nectria Canker

515

Frequency Distribution of Nectria Canker

By Plots

Almost every article on Nectria canker stresses the fact that its dis-
tribution is very irregular. That is, certain stands, no matter what their
species composition, are heavily cankered while other closely adjacent
stands of the same species composition may have little or no canker. This
was found to be true of the forests examined in this survey. Figure 87
indicates how variable may be the amount of Nectria infection. The per-
centage figures indicate the number of cankered trees on each plot. Plots
closely adjacent to each other have such percentages as: 1, 8, 15, 8, 11,
25, 22, 17, 8, 16, 20, 1 etc.

FOREST

NO- OF
PLOTS

PER C ENT
25 SO 75 100

MOHAWK
PACHAUG
MESH OM ASIC

T U/VX 1 S
MATTA TUCK
NATCH AUG
COCK A PONSET
N EH A NT/ C
PEO PLE S
HOUSATON IC
PA U G N UT
POOTATUCK

TOTAL AND A VE.

9
%2I 6

*4 7 7

*3 7 6

4 9

8 4

*J 2 0

14 1

4 1

2 8

1 2 4

1 7

1 852

1 1 1 1 1 1 . 1 1 1 1 1 1 I 1 I 1 1 | 1 1

| 10 0
| 91

1 76
■//

|* 8

J/^36

|j 3

1 6

1 7 1

ii i i 1 i i i i 1 i i i i 1 i i i i 1

Figure 92. Number of plots examined (in percent) which have one or more Nectria
cankers — by forests.

The fact remains, however, that Nectria cankered trees are very widely
and very generally distributed throughout a stand, even though they are
not uniformly distributed. Figure 92 shows, for example, that of 216 plots

516

Connecticut Experiment Station

Bulletin 412

laid out at random in all forest types and age classes over an area of 2500
acres at Pachaug alone, 91 percent had one or more Nectria cankered trees
on them. Similarly the Meshomasic had cankers on 82 percent of the plots,
Tunxis 76 percent and Cockaponset 68 percent. Any disease which can
be found on from 91 to 68 out of 100 plots laid out at random must be
quite generally distributed.

I PLOTS
\CANKERED TREES

H

S- 9 10-14 15-19 20-24 25-29 30-34

DEGREE OF INFECTION (PER CENT)

n

— n -j=i _n

Figure 93. Frequency distribution of plots (in percent) of different degrees of
Nectria infection in relation to number of Nectria cankered trees on those plots. Black
bar — percent of plots. White bar — percent of Nectria cankered trees.

Frequency distribution based on whether a plot has or has not Nectria
cankered trees on it (Figure 92) gives little idea of the distribution of
different amounts of Nectria cankers. Figure 93 shows that the percentage
of infection by Nectria cankers has a very skewed distribution. That is,
58.1 percent of the plots have only 16.2 percent of the Nectria cankered
trees, or roughly 80 percent of the plots have 40 percent of the cankered
trees. (Table VII). On the other end of the scale, 2.4 percent of the plots
have 14.8 percent of the cankered trees.

Nectria Canker

517

Table VII. Percent Frequency of Occurrence of Different Degrees of

Infection by Nectria

Total

Degree
of infection

Plots examined

cankered trees

Total trees
per plot

No. cankered
trees per plot

(percent class)

number

percent

number

percent

(average)

(average)

0— 4

730

58.1

927

16.2

78

1.3

5— 9

270

21.5

1413

24.7

85

5.4

10—14

118

9.4

1036

18.1

77

9.1

15—19

57

4.5

721

12.6

81

13.2

20—24

38

3.0

561

9.8

60

15.3

25—29

14

1.1

217

3.8

66

16.4

30—34

14

1.1

423

7.4

99

31.6

35—39

7

0.6

177

3.1

73

26.6

40—44

4

0.3

92

1.6

72

24.3

45—49

2

0.2

51

0.9

61

26.5

50—54

2

0.2

103

1.8

101

53.0

TOTALS &
AVERAGES

1256

100 0

5721

100 0

79

4.7

By Species:

Some species are cankered on many of the plots on which they occur. This
was true of mountain maple 100 percent, dogwood 80 percent, scarlet oak

Table VIII. Percent Frequency of Occurrence of Nectria Cankers by Species

Plots

Plots

on

Plots

on

Plots

which

on

which

on

SPECIES

species

which

SPECIES

species

which

specie*

species

red

were cankered

red

were cankered

Large tree species

No.

No.

percent

No.

No.

percent

Scarlet Oak

472

205

43

Tulip

157

0

0

Black Birch

813

314

39

Butternut

49

0

0

White Birch

196

64

33

Pin Oak

1

0

0

Gray Birch

441

140

32

Bed Maple

1149

358

31

Small tree species:

Black Oak

429

130

30

Mountain Maple

1

1

100

Pepperidge

100

30

30

Dogwood

127

102

80

Sassafras

213

61

29

Striped Maple

85

34

40

Yellow Birch

490

139

28

Alder

43

10

23

Black Ash

9

2

22

Pin Cherry

13

3

23

Black Cherry

290

62

21

Shadbush

54

5

9

Sugar Maple

338

67

20

Scrub Oak

45

3

7

Aspen

209

34

16

Blue Beech

136

0

4

Hickory

594

94

16

Hop Hornbeam

163

5

3

Red Oak

891

129

14

Miscellaneous

23

6

26

Basswood

99

12

12

White Oak

840

89

11

Species groups:

Beech

337

21

6

Birches

1940

657

34

White Ash

524

25

5

Maples

1573

460

29

Elm

40

2

5

Oaks

2899

561

19

Chestnut Oak

221

5

2

Softwoods

523

0

0

Miscellaneous specie6 are sumac, witch hazel, willow, black walnut, apple, sycamore and spruce.

518 Connecticut Experiment Station Bulletin 412

43 percent, striped maple 40 percent, and black birch 39 percent. (Table
VIII). On the other hand, chestnut oak 2 percent, hop hornbeam 3 per-
cent, blue beech 4 percent, elm 5 percent, and white ash 5 percent, are not
usually cankered on the plots on which they occur. The species groups
show a frequency of occurrence of Nectria canker of birches 34 percent,
maples 29 percent and oaks 19 percent.

Location of Nectria Cankers
Height on the Trunk

Most Nectria cankers are located on the main trunk of the tree not far above
the ground. The location varies greatly with the different species groups.
In the oaks 97 percent of the cankers were located within 8 feet of the
ground, in the maples 86 percent and in the birches 51 percent. Further-
more, in oaks practically 100 percent of the cankers were located within
16 feet of the ground, maples 99 percent and birches 82 percent. (Figure
94). This location of the cankers affects the value of the butt log.

In oaks the cankers are often located so close to the ground that they
are within stump height, hence do not cause any cull unless decay has
entered and gone up the bole. In sugar maple most of the Nectria cankers
are located at the base of the tree, while in red maple their location is more
variable. Beech 99 percent, hickory 92 percent, and white ash 91 per-
cent have most of their cankers located within four feet of the ground,
like the oak. Pepperidge66 percent, aspen 76 percent, sassafras 67 percent,
black cherry 82 percent, pin cherry 60 percent and basswood 78 percent
have a smaller proportion of their cankers within four feet of the ground
and resemble the maples and birches in that respect. The location of
cankers on the different species of oaks examined was very similar. The
same was true of the birches.

Andrews (1935) reported 75 percent of the cankers within the first 5
feet of bole, 90-97 percent in the first 10 feet, and 96-99 percent in the
first 20 feet. He claimed that this data held constant within a species
regardless of crown class and height and from this concluded that canker-
ing occurred early in the life of the tree.

In the birches the dominant trees apparently continued to develop
cankers at higher levels later in life. Aside from these cankers at higher
levels most of them appear to start early in the life of the tree.

Plot exposure had no effect on the height of occurrence of the cankers.

Branch Cankers

Cankers were found on the branches of only 4.8 percent of those trees
which had one or more cankers. This is a small number considering that
the branch cankers are usually few and small. The cankers noted were
those which could be seen from the ground and some may have been
missed. Branch cankers were seen on only half of the species on which
cankers were found. (Table IX).

Nectria Canker 519

49-52

1

45-46

1

41-44

37-40

1

33-36

1

29-J2

J

25-28

]

21-24

3

k>

^17-20

3

Q

*
i

Q./J-/5

"■■■■■■

<J

9

kj
^.
O
«j 9-12

T
(-.

*:

Z S-B

WtM 8IRCHCS
1 l mapi f;

1

B

1

0-4

•

stA

0 10

20 30

*0 JO tfO

^ 50

P £ R

C£N T

Figure 94. Location of Nectria cankers — height above ground.

520

Connecticut Experiment Station
Table IX. Species Having Branch Cankers

Bulletin 412

SPECIES

Number

Trees with branch cankers

trees

number

percent

24

3

12.5

1202

128

10.6

22

2

91

416

37

8.9

150

8

5.3

691

35

5.1

61

3

4.9

188

8

4.3

50

2

4.0

159

3

19

85

1

12

1037

13

1.2

478

2

0.4

21

7

33.3

172

26

15.1

12

1

8.4

863

_

0.6

1574

—

3.0

2459

—

8.5

Large tree species:

White Ash
Black Birch
Pepperidge
Yellow Birch
White Birch
Gray Birch
Aspen

Sugar Maple
Black Cherry
Bed Oak
Black Oak
Bed Maple
Scarlet Oak

Small tree species

Dogwood
Striped Maple
Mountain Maple

Species groups

Oaks

Maples

Birches

AVERAGE FOR SPECIES GROUPS

4.8

Of all cankered trees observed 1.1 percent had branch cankers only,
3.7 percent had both branch and trunk cankers and 95.2 percent had
trunk cankers only. Those species which are most frequently cankered
(Table VI) also most frequently have branch cankers. The birches are
by far the most frequently infected in the branches of any of the species
groups. Birches accounted for 18 percent of all trees examined, 42 percent
of the cankered trees and 75 percent of the branch cankers. This location
of the cankers may be a contributing factor in the death of birches by
Nectria canker. The smaller branches are more easily girdled and killed.
By gradual loss of the crown the tree is weakened and finally killed. Field
observation indicates that dying yellow and black birches often have part
of their crown killed by girdling, and dead birches often stand up as stubs
with their entire crown gone.

Number of Nectria Cankers Per Tree by Species

The number of cankers per tree varies pom one to many, the average j or all
species cankered being 2.9. In general those species which have the largest
proportion of their individuals infected are also the species which have the
greatest number of cankers per tree. There are some exceptions such as
scarlet oak and aspen. Among the Large Tree Species black birch has
4.6, sassafras 4.6 and pepperidge 3.7, the largest number of cankers per
tree. Next comes yellow birch with 3.3, gray birch with 3.3 and white
birch with 2.8 (Table X). Mountain maple has 3.7 and striped maple 3.2,
the largest number per tree among the Small Tree Species.

Nectria Canker

521

Of the species groups, birches have the greatest number of cankers per
tree, 3.9, followed by maples, 2.2, and oaks, 2.0, in the same order as the
percentage of trees infected (Table VI) .

The frequency of occurrence of the number of Nectria cankers per tree
(Table XI) shows a relatively greater percentage of the oaks and maples
with one to two cankers per tree than birches, and a relatively smaller
percentage with three and more cankers per tree.

Table X. Number of Nectria Cankers per Tree

Weighted

Weighted

SPECIES

average

number of

cankers

SPECIES

average

number of

cankers

per tree

per tree

Large tree species

Black Birch
Sassafras
Pepperidge
Yellow Birch

4.6

4.6
3.7
3.3

Small tree species:

Mountain Maple
Striped Maple
Dogwood
Alder

3.7
3.2
1.6
1.4

Gray Birch
White Birch
Black Cherry
White Ash

3.3
2.8
2.8
2.6

Pin Cherry
Hop Hornbeam
Shadbush
Blue Beech

1.3
1.2
1.2
1.1

Hickory
Sugar Maple
Red Oak

2.3
2.3

2.2

Scrub Oak
Miscellaneous
AVERAGE

1.0
2.4
2.1

Scarlet Oak

2.1

AVERAGE— ALL SPECIES

2.9

Red Maple

2.1
2.1

Basswood

Elm
Black Oak

2.0
1.9

Species groups:

Birches

3.9

Aspen
White Oak

1.8
1.6

Maples
Oaks

2.2

2\0

Beech

1.4

Chestnut Oak

1.0

AVERAGE

3.0

Miscellaneous species with Nectria are witch hazel, sumac, willow and apple.

Table XI. Percent Frequency of Number of Nectria Cankers per Tree

BIRCHES

MAPLES

OAKS

ALL SPECIES

Number

Percent

Percent

Percent

Percent

of

of

of

of

of

cankers

trees

trees

trees

trees

1- 2

50.4

75.0

79.0

65.7

3- 4

21.1

14.5

13.4

16.9

5- 6

10.7

5.1

4.4

7.2

7- 8

6.3

2.6

2.0

4.0

9-10

4.4

1.2

0.8

2.4

11-12

2.7

0.7

0.1

1.4

13-14

1.5

0.4

0.0

0.8

15-16

1.2

0.2

0.2

0.6

over 16

1.7

0.3

0.1

1.0

TOTALS

100.0

100.0

100.0

100.0

522

Connecticut Experiment Station

Bulletin 412

4
k 3

<*:

■

1-5 6-10 1-5 6-/0 l-S 6-10
INCHES INCHES INCHES

OAKS MAPLES BIRCHES

Figure 95. Number of Nectria cankers per tree in relation to diameter classes.
Diameter classes 1-5 inches and 6-10 inches.

5 D

OAKS

S D
MAPLES

S D

BIRCHES

Figure 96. Number of Nectria cankers per tree in relation to crown classes. S —
Suppressed — includes both suppressed and intermediate crown classes. D — Domi-
nant— includes both codominant and dominant crown classes.

Nectria Canker

523

Andrews (1935) states that the greatest number of Nectria cankers per
individual occurred in the lowest diameter and crown classes. He adds,
however, that this may be due to species differences at that stage of develop-
ment, as sugar maple was very abundant in the stand examined. It formed
60 percent of the entire population examined and an even larger percentage
of the small diameter classes.

The above statement is borne out by the data here presented as far as
the maples and oaks are concerned but not for the birches. The maples
have a decreased number of cankers per tree with increased diameter
(Figure 95) and in the upper crown classes (Figure 96). The same is true
in the case of the oaks. In birches, however, the reverse is true ; that is,
the larger, more dominant birches have a greater number of cankers per
tree than the smaller, suppressed birches. This order is exactly the same
for the number of cankers per tree as it is for the number (percentage) of
trees infected with Nectria cankers (Figures 97 and 98).

Fruiting of Nectria Cankers

During the course of the field work on the Tunxis Forest the Nectria
cankers located less than six feet from the ground were examined for
evidences of fruiting. These data (Table XII) indicate that fruiting was
greater in the spring season than at any other time, which substantiates
part of the findings of Welch (1934). Welch, however, found an increase
in fruiting in the fall also. The examinations made from September to
November, 1935, do not bear this out but a dry summer season may have
been unfavorable to fruiting. The observations were not continued over a
sufficient period of time to give conclusive results on that point. Spaulding
et al. (1936) report a very definite increase in fruiting with increased
moisture of the habitat but present no data on the seasonal fruiting of
cankers on standing trees.

Table XII. Amount of Fruiting of Nectria Cankers in Relation to Season
(Tunxis Forest 2200 Cankers)

Date

Amount of fruiting (percent)
Abundant Sparse None

Number of cankers

January-March
March-June
June— September
September-November
November-January

Averages and Total

50
13
13
10

7

11

6
6
5

7
3

5

44
81
82
83
90

84

103
157
198
812
930

2200

The amount of fruiting at any time was not large, an average of 84 per-
cent showing no fruiting whatever, while 5 percent of the cankers examined
were fruiting sparsely and 11 percent abundantly.

Avenues of Entrance of the Nectria Organism

More than 1700 Nectria cankers on the Tunxis Forest were observed to
determine the possible avenue of entrance of the organism. In many
cases it could not be determined with certainty and these were discarded.

524

Connecticut Experiment Station

Bulletin 412

Of those which could be determined, the largest number, 45 percent, had
evidences of an old branch stub apparently in the center of canker develop-
ment through which the organism seems to have entered. About 20 per-
cent were associated with borer injury, 10 percent with frost cracks, 9
percent with rubbing injuries, 8 percent with miscellaneous lesions and
8 percent with mechanical injuries. Often callus folds, dead bark or decay
of the exposed wood in the center of the canker obscures the possible point
of entry. These data agree in part with the avenues of entrance as given
by Grant (1936). He lists as causes: rubbing, 8 percent; crotches of
living branches, 15 percent; branch stubs, 56 percent; and unknown, 21
percent. Regarding branch stubs he says, "Regardless of exact point of
entrance the data show that branches were important as avenues of en-
trance for Nectria into the host."

Effect of Nectria Cankers on Host Species

Damage to the individual tree infected by one or more Nectria cankers
depends on its size, vigor, species and degree of infection. Spaulding (1936)
says, "Nectria cankers sometimes kill trees outright but far the greater
number cause weakening or crippling, leading to premature death or wind
breakage." Welch (1934) states that because the spread of fungus is slow,
often less than .5 inch a year, "the danger of killing by girdling is not
very great". He concludes that it is chiefly a menace because it opens a
wound to decay, often leading to the heartwood through a dead branch stub.
Andrews (1935) suggests that damage may be serious in small trees in
which girdling and death can be quickly brought about, and points out
that this is what happens to the side branches through which the disease
enters. He specifically states, "In larger sizes very little evidence of in-
hibition of growth by well developed cankers could be found". Sometimes
vigorous trees of certain species can overgrow the canker, but there still
remains either a defect or an area of decay which may increase in size.

No special study of the growth rate of cankered trees was made but
very frequently dead trees bearing Nectria cankers were found. The size
and species of these trees was noted. Whether the tree died because of the
presence of Nectria cankers could not, of course, be determined with
certainty in all cases, but observers were requested to list as dead with
Nectria cankers only those trees where it seemed reasonably sure that
Nectria was either the primary cause or a contributing cause of the death.

With this limitation in mind, the data is sufficiently clear cut to be of
value in comparing the species groups. (Table XIII).

Table XIII. Percent of Nectria Cankered Trees That Were Dead —

(by Species Groups)

D.B.H. class

(inches)

Oaks

Maples

Birches

1-2

9.1

13.5

10.2

. 3-4

3.1

8.6

14.1

5-6

1.3

13.5

10.6

7-8

0.6

4.8

13.6

9-10

0

0

8.7

Averages

3.2

10.7

10.3

Nectria Canker 525

The data in Table XIII was obtained by recording, for example, the
number of Nectria cankered maples in the one and two-inch D.B.H. class
(993) and the number of dead cankered maples in the same D.B.H. class
(134) and determining the percentage dead, 13.5. A very much larger
percentage of oaks was dead with Nectria cankers in the small sizes than
in the larger sizes. This tendency was not so evident in maples where the
figures were quite high in both classes. In birches the percentage dead with
Nectria was practically as large in the seven to eight and nine to ten-inch
classes as it was in the one to two-inch class. The oak group was in strik-
ing contrast with the birch group. The weighted average D.B.H. of the
cankered trees in each species group was: birches 3.7 inches, oaks 2.5
inches and maples 2.1 inches.

Most of the oaks found dead with Nectria cankers were small ; hence the
disease may act to weed out many small trees in the stand. In maples,
many small trees were dead with Nectria cankers, but there were also
some in the middle-size classes. In birch, Nectria cankers were frequently
destructive both to the small and also to the large trees. Observation in
the field indicates clearly that many large, yellow, black and white birch
are so infected by many Nectria cankers as to kill them. Observation
indicates that the maples seem to be able to overgrow the Nectria cankers,
while in birches this does not appear to occur. In oaks, although there
are many severe basal cankers on large trees, death does not seem to result
nor is breakage evident.

Nectria Canker in Relation to Age of Infected Trees

The age of the trees infected with Nectria cankers was determined in
the field by increment borings. The distribution of age classes is probably
similar for healthy and cankered trees, hence these data (Table XIV) in-
dicate what age classes were prevalent in the forests examined. The
greatest number of cankered trees were 16 to 20 years old, followed by the
11 to 15-year class and the 21 to 25-year class. Insufficient data were
available on the ages of the healthy trees on the plots, hence the percentage
of infection by age classes could not be determined.

A comparison of the species groups by 25-year age classes shows that
the younger birches are less often infected than the maples and oaks, but
that in the older classes (26 to 50 and 51 to 75) the birches are more often
infected than the maples and oaks. These results are similar to those dis-
cussed under the effect of Nectria cankers on host species. Many of the
birches become infected while young and are not able to overcome the
infections and apparently continue to develop new cankers as they become
older, hence more of the older trees are cankered and eventually they may
be killed by the disease. The maples become heavily infected while young,
and a number of them die at this time and also to some extent when older.
However, many are able to outgrow the disease, hence the older maples
are found to be less frequently infected. The oaks become heavily infected
when young and many die. Those that survive do not outgrow their
cankers nor do they apparently become more frequently infected as they
become older.

526 Connecticut Experiment Station Bulletin 412

Table XIV. Age of Trees Cankered by Nectria

Number

All

Age class

trees

species

Oaks

Maples

Birches

cankered

(percent)

(percent)

(percent)

(percent)

1- 5

52

1.0

0.4

1.0

1.0

6-10

428

8.6

5.8

10.3

6.6

11-15

951

19.1

16.8

25.1

15.5

16-20

1107

22.1

25.4

25.0

21.4

21-25

727

14.6

18.0

15.2

14.4

Sub-total

3265

65.4

66.4

76.6

58.9

26-30

486

9.7

10.0

8.9

11.0

31-35

361

7.2

8.7

4.1

8.8

36-40

283

5.7

5.7

3.4

6.9

41-45

174

3.5

2.2

3.2

4.7

46-50

133

2.7

3.3

1.3

2.9

Sub- total

1437

28.8

29.9

20 9

34 3

51-55

76

1.4

1.3

0.5

2.0

56-60

59

1.2

0.9

0.3

1.3

61-65

54

1.1

0.7

0.7

1.3

66-70

39

0.8

0.2

0.3

1.1

71-75

23

0.5

0.3

0.3

0.3

Sub-total

251

5.0

3.4

2.1

6.0

76-80

8

0.2

0.0

0.2

0.2

81-85

9

0.2

0.2

0.1

0.2

86-90

6

0.14

0.1

0.0

0.2

91-95

1

0.02

0.0

0.0

0.1

96-100

2

0.04

0.0

0.0

0.05

Sub-total

26

0.60

0.3

0.3

0.75

over 100

8

0.2

0.0

0.1

0.05

GRAND TOTAL

4987

100.0

100.0

100.0

100.00

Nectria Canker

527

Nectria Canker in Relation to Diameter of Trees

The diameter of all trees, whether healthy or diseased, was measured.
This made it possible to determine the percentage of all the trees in a given
diameter class which were infected by Nectria cankers. The number
above 10 inches D.B.H. was small ; hence the data were not used in Figure
97. In the birches there is a very definite rise in the proportion of Nectria

Figure 97. Number of Nectria cankered trees (in percent) by diameter classes.
Diameter classes 1-2 inches, 3-4 inches, 5-6 inches, 7-8 inches and 9-10 inches.

cankered trees with increase in diameter. In the maples there is as definite,
though not as great, a decrease with increase in diameter. The oaks show
a slight increase in infection with increase in diameter. These data point
to conclusions similar to those discussed under Nectria canker in relation
to age of infected trees.

528

Connecticut Experiment Station

Bulletin 412

Neclria Canker in Relation to Crown Class

The crown class of the trees infected with Nectria canker was compared
with the crown class of the healthy trees. The results are shown in Figure
98 which should be compared with Figure 97. The dominant and codomin-
ant birches are more frequently cankered than the intermediate and sup-
pressed. In the maples this is reversed; that is, the dominant and co-
dominant trees are less frequently infected than the intermediate and
suppressed. Apparently the vigorously growing trees, which are usually

m

S I C D
OAKS

S I C D

MA P L £ S

S I C D

B I R C H E S

Figure 98. Number of Nectria cankered trees (in percent) by crown classes.
S — suppressed, I — intermediate, C — codominant, D — dominant.

in a dominant position, are able to outgrow the disease. The oaks re-
semble the birches showing a larger amount of infection in the dominant
and codominant classes than in the suppressed and intermediate classes.

An examination of the data for the individual species other than oaks,
birches and maples shows that beech, hickory, alder, basswood and pep-
peridge have a greater amount of Nectria in the higher crown classes than
in the lower, resembling the birches. Aspen, black ash, sassafras and
black cherry have a lesser amount of Nectria in the higher crown classes
than in the lower, resembling the maples.

Nectria Canker 529

Nectria Canker in Relation to Origin of Tree

There was no relation between the origin of the tree, whether sprout or
seedling, and the amount of Nectria canker.

Nectria Canker in Relation to Forest Type

Since forest types vary in species composition and in habitat factors,
they would be expected to vary in the amount of Nectria infection. This
has been shown to be the case in Connecticut forests (Table XV). The
Hardwood Swamp type had the greatest number of infected trees, 12.1
percent, probably because of the abundance of red maple and yellow
birch,* two heavily cankered species, and poor growing conditions in the
swamp type. Observation has shown that the hardwood swamp type is
usually composed of poor quality trees having Nectria cankers as well as
decay, lesions, dead tops and other defects.

The old field type had a large amount of Nectria, 10.4 percent, because
of the abundance of gray birch and the open character of many of the old
field stands. The mixed hardwoods type, found on a variety of sites, is
composed of a large number of species, some heavily cankered, others not.
The large number of the immune softwoods cause the softwood-hardwood
type and the softwood type to have a small amount of Nectria canker.
The oak ridge type with its abundance of chestnut oak, hickory and other
oaks also ranked low in the amount of Nectria canker.

Table XV. Nectria Cankers in Relation to Forest Type

Forest type

Symbol

Trees
Examined
(Number)

Trees cankered

(Number)

(Percent)

Swamp Hardwood

s

2209

267

12.1

Old Field

OF

1130

428

10.4

Mixed Hardwoods

MH

75527

4294

5.7

Softwood-Hardwood

SH

12961

530

4.1

Oak Ridge

0

2518

90

3.6

Softwood

SW

618

20

3.2

Nectria Canker in Relation to Density of Stand

The total number of trees per plot averaged 79 but there was no con-
sistent difference in number of trees on the lightly diseased plots compared
to the heavily diseased plots. Since the average number of trees per plot
was based on all types and age classes, the number of stems would not
necessarily indicate the actual density of the stand unless the age of the
stand was known.

The same applies to a basal area per plot figure ; hence no attempt was
made to determine a correlation between basal area and percentage of
trees infected with Nectria canker.

530

Connecticut Experiment Station

Bulletin 412

The density of the canopy on each plot was judged by the observer and
rated according to the usual system of 0.1 to 1.0, from a very open canopy
(0.1) to one in which the crown cover is complete (1.0). The data for
density 0.1 and 0.2 are too few to be of any value. The number of plots
in each canopy density class and the percentage of Nectria infection follows :

Crown density class

Number of plots

Average percent
Nectria infection

1- 2

6

(plots too few)

3- 4

53

7.4

5- 6

290

6.5

7- 8

775

5.5

9-10

130

3.4

There is a slight but definite trend toward decreasing Nectria infection
with increasing density of the canopy. (Figure 99). These facts would
lend weight to Grant's (1936) suggestion that a densely stocked stand
where the side branches are small and few in number would seem to be

8

■

-

k

6

1

■

-

*

;

■

I

■

<*J

■

■

o

4

■

I

1

-

tfc

-

1

1

kj

1

'

■

0.

2

1

1

-

.3-4

.5^6

J-JB

.9-W

C R OWN

D ENS ITY

CI JSSES

Figure 99. Nectria infection in relation to crown density classes. Crown density
classes, .3-.4, .5-.6, .7-.8 and .9-1.0.

desirable from the point of view of minimizing Nectria canker formation
on young stems. The rapid healing over of small wounds left by the
early pruning of side branches would be desirable. Hence any silvicultural
practices tending to produce dense young stands would be beneficial from
the standpoint of reducing Nectria infection.

Nectria Canker 531

Nectria in Relation to Age of Stand

The amount of Nectria on plots located in different age classes of forest
stands was determined. The data varied so widely that no reliance could
be placed on averages obtained from all the forests. Previous history and
species composition of the stand, as well as other possible factors, enter in
to obscure any effect which age of the stand may have.

Likewise large numbers of the plots were in uneven aged stands with a
varied mixture of ages.

Nectria in Relation to Plot Exposure

The direction of facing of nearly 3000 Nectria cankers on the Tunxis
Forest in relation to the exposure of the plot was determined. There was
no correlation evident. About the same average number of cankers were
found on each exposure. Neither was the direction of facing of the cankers
affected by plot exposure.

Nectria in Relation to Site Quality

The field crews designated each plot examined as good (1), medium (II)
or poor (III) site. This designation was an ocular estimate based on the
height, age, vigor and appearance of the trees of the plot. The exact
height-age of a dominant and a codominant tree on each plot was obtained
in the Tunxis Forest. This data, when averaged according to site classes,
gave a height at a classification age of 50 years of:

Site I -53 feet
Site II -48 feet
Site 111-40 feet

A comparison of the four forests indicated that species composition has
a very marked effect on the relation between site and amount of Nectria
infection since oaks and hickories, comparatively lightly infected species,
are more prevalent on the poorer sites than are birches and maples.

Examination of seven frequently cankered species was made on the
Tunxis Forest. The percentage oj trees infected with Nectria cankers was
greater on the poor sites than it was on the good sites. (Figure 100).
This difference was particularly marked in the four species of birch where
Site III had 28 percent Nectria infection, Site II, 17 percent and Site I,
10 percent. Striped maple also showed a difference while sugar maple and
red maple showed little difference.

Many other factors beside site quality determine the percentage of Nec-
tria infection, chief among them being species composition of the stand
and past history of the stand. Hence care must be used to give proper
weight to the species composition of the stand under consideration, as well
as its site quality.

532

Connecticut Experiment Station

Bulletin 412

/ // ///

/ // ///

YELLOW BIRCH WHITE BIRCH

m a I ■■!

GRAY BIRCH

II III
RED MAPLE

I II III

I II III

SUGAR MAPLE STRIPED MAPLE

Figure 100. Effect of site quality on number (in percent) of Nectria cankered
trees of seven species. (Tunxis Forest-376 plots). I — good site, II — medium site,
III — poor site.

Discussion

The oaks, maples and birches constitute three-fourths of the trees found
in the four forests examined. These species groups, together with the
immune softwoods, account for most of the tree population. The oaks
form a large percentage, 32.0, of the total population, but since they are
not frequently cankered by Nectria, 3.6 percent, the cankered individuals
form only a small part of the total population, 1.1 percent, (Figure 101).
In contrast, the birches form a smaller percentage, 18.1 of the total popula-
tion, but since they are frequently cankered by Nectria, 12.5 percent, the
cankered individuals form a relatively large part of the total population,
2.3 percent. The maples are intermediate between the oaks and the birches.

The Tunxis Forest contrasts with the other three forests in having few
oaks and many maples. Several forests have more Nectria cankered oaks
than they have Nectria cankered maples.

In an effort to determine just what the conditions were on the severely
Nectria cankered plots, all plots which had 15 or more percent of Nectria
cankered trees were analyzed. The number in each forest was: Tunxis 38,
Pachaug 27, Meshomasic 40, and Cockaponset 10.

Since suppressed trees would likely drop out of the stand in the course
of time, these would probably never enter into the final crop unless man

Nectria Canker

533

SPCCIES
GROUPS

nnf fin

TtTTIfgltti

nrmtttti

illlilxttlll!

^f /? C f AT
/<? <?0 JO

SB

I
ffi

ff

33

ttifi

1 | /ȣ/<? OT/V7- 7-07/4Z. POPULATION
^^PER CENT TOTAL POPULATION CANKERED
\ffQPER CENT SPECIES CANKERED

SB

im,i?

;»»»»m;

Figure 101. Comparison of species groups with regard to species composition of
the forest: percent of species Nectria cankered and percent of total population Nec-
tria cankered. Entire white bar — percent of the total population made up of the
species group indicated. Black part of bar — percent of total population made up of
Nectria cankered trees. Cross-hatched bar — per cent of the species cankered.

534 Connecticut Experiment Station Bulletin 412

favored them in his silvicultural operations. Likewise trees such as gray
birch, aspen, dogwood, sassafras and others are of little or no value as
components of the final stand, although they may have value as trainers
and in other ways. If the suppressed Nectria cankered trees of all species,
and the cankered trees of undesirable species are deducted from the plots
having 15 or more percent Nectria cankered trees, 75 percent of these
plots drop below the 15 percent limit. This drop is particularly marked
in the old field type due largely to cankered gray birch. Such stands are
usually heavily cankered and because of their species composition they
should often be cut off and planted to conifers. In other cases sassafras
was found to be very heavily cankered.

Black birch was often very heavily cankered on these plots, not only in
the lower crown classes but also in the upper crown classes. In fact,
black birch leads all other species which were Nectria cankered in the
dominant or codominant crown classes. Dominant red maples were also
frequently cankered, especially on the PachaUg forest where, although
the forest was predominantly oak, the most severe Nectria cankering was
in stands in wet areas heavy in red maple. Dominant yellow birch and
scarlet oak were frequently cankered. All this emphasizes the importance
of species in relation to Nectria canker. •

Control Measures

The results of the survey indicate that in Connecticut forests Nectria
cankered trees are usually not so abundant but that they can be removed
from the stand without injurying it to any great extent. Many of the
cankers were found on suppressed trees which would in time pass out of
the stand. Others were found on inferior species which would never be
chosen as crop trees although they might be of value as trainers. How-
ever, in view of the fact that most Connecticut forest stands are under-
stocked, the removal of even a small number of trees may be of importance,
particularly if those trees are of good species.

Since Nectria is a wind-borne organism, it is capable of wide and rapid
spread. Therefore complete, permanent elimination of the disease from the
stand is, very likely, impossible. Certainly it is impracticable. The pres-
ence, frequently, of very small branch cankers makes the present elimination
of all cankers from the stand almost impossible. An abundance of wind-
borne spores makes future infection likely.

The cost of direct control makes it impracticable to go through a stand
solely for the purpose of girdling or cutting Nectria cankered trees. Such
work should be considered a part of regular stand improvement practice
and done at the time the stand is treated. Since the presence of cankers
causes weakening and slowing up of the growth rate, deformation, breakage
and possible death, or cull and possible decay entrance, trees with Nectria
cankers should not be chosen as crop trees. There are small spots in Con-
necticut forests where cankered trees are so numerous it is necessary to
choose some crop trees with cankers. In that case, preference should be
given to those species such as the oaks and maples which do not usually
succumb to Nectria canker, and to such individuals as have cankers

Strumella Canker 535

located high up in the tree, where they will not cause cull in the butt log
or, less desirable, near the ground where they will cause little or no cull.
Few trees with basal cankers seem to break over or die, but rot often does
enter. Hence such trees should be chosen only as a last resort.

The abundance of Nectria cankers on certain of the weed species, such
as striped and mountain maples, dogwood and alder, the inoculum from
which is capable of infecting more valuable species, Spaulding et at (1936),
make it desirable to cut these infected weed trees whenever they are en-
countered in the course of regular silvicultural work. The elimination of
these cankered weed species and as many of the cankered timber species
as practicable will lessen the amount of inoculum and thus lessen the
chances for infection of the remaining stand.

Both the present and future value of a stand, and the use to which it
will be put, determine the kind and amount of control work that should
be done (Grant 1937). If a stand is of poor quality, it is not worth expend-
ing much effort in the reduction of Nectria canker. If the stand is to
be used largely for water shed protection, wild life protection or recrea-
tion, not much time or money need be expended in the control of Nectria
canker. Stands intended primarily for timber production, particularly
saw logs, should be well cared for. Considerable time spent on Nectria
control in such stands is justifiable.

Since dense, rapidly growing stands on good sites are most apt to be free
of Nectria infection, any silvicultural practices which produce dense stands
of young trees which self-prune early in life to a considerable height on
sites favorable to healthy and rapid growth, are to be favored. If these
practices are followed by weeding and thinning to continue rapid growth,
the amount of Nectria canker should be at a minimum. In a word, good
silviculture is good Nectria control.

1. The elimination of Nectria cankered trees should be carried
out in connection with regular stand improvement work.

2. Girdle, or better cut down and utilize, all cankered trees if this
practice does not open up the stand too much. If it does, leave
some of the cankered trees as trainers.

3. Do not choose trees with Nectria cankers as crop trees.

STRUMELLA CANKER

Cankers caused by Strumella coryneoidea are very characteristic in ap-
pearance and are found chiefly on the oaks. The cankers are more elon-
gated than those caused by Nectria and have successive ridges of callus
growth making a concentric pattern around a branch stub or crotch where
entry usually occurs. The fungus kills back the callus, enlarging the
canker, and the dead, exposed wood finally decays and sloughs off. Exces-
sive growth opposite the canker gives a characteristic bulge to the tree
trunk which serves to spot the disease at a distance. The disease often
kills the tree or causes it to break off at the canker.

Strumella cankers were found sparingly on all four forests. The Tunxis
Forest had very few cankers because of the small amount of oak present.
Only 215 Strumella cankers were found, or 0.2 percent of all trees examined.
Of the 31,469 oaks examined, 194 or 0.6 percent had Strumella cankers,

536

Connecticut Experiment Station

Bulletin 412

(Table XVI). This is a relatively small number compared with the Eli
Whitney Forest in southern Connecticut where from 1 to 5 percent of the
oaks were cankered by Strumella. (Bidwell and Bramble, 1934).

Table XVI. Pebcentage of Tbees Infected by Stbtjmella Cankebs

SPECIES

Tunxis

Pachaug

Meshomasic

Cockaponset

Four Forests

Black Oak
Scarlet Oak
Scrub Oak
Red Oak
Chestnut Oak
White Oak
Hickory
Beech
Red Maple

0

2

2.3
1.1
0.8
1.8

0.5
0.1
0.4
0.3

0.3
0.1

0'3
0.3

6. 04

3.2
1.5

i'.4

0.7
0.7
0.5
0.3

1.5

0.9

0.8

0.7

0.4

0.3

0.2

0.08

0.05

AVERAGE

0.01

0.5

0.06

0.5

0.2

All Oaks

0.6

Black oak was most frequently cankered 1.5 percent, followed by scarlet
oak 0.9 percent, scrub oak 0.8 percent, red oak 0.7 percent, chestnut oak
0.4 percent and white oak 0.3 percent. The ranking was practically the
same on each of the four forests. Bidwell and Bramble (1934) give the
relative frequency of infection on one area as red and black oak 13.9 per-
cent, scarlet and pin oak 5.0 percent, and chestnut and white oak 3.1 per-
cent.

Most of the cankers were located on the lower part of the bole, 69 per-
cent within 8 feet of the ground and 94 percent within 16 feet of the ground.
(Figure 102).

This location renders cull all or part of the most valuable butt log.

The cankers varied in length from one foot to eight feet, the weighted
average length being 1.8 feet.

Length (feet)

Percent

Length (feet)

Percent

1

57

5

2'

2

24

6

1

3

9

7

0.5

4

6

Average

8
1.8

0.5

Strumella Canker

537

•R-

% 17-20

w /3-/e\

S 10 IS

PER CENT

Figure 102. Location of Strumella cankers, height above the ground.

The larger trees were more frequently infected with Strumella cankers
than the smaller trees. The average of all species examined was :

D.B.H.

(inches)

Percent cankered

1- 5

0.2

6-10

0.5

11-15

0.4

This held for all species infected. The larger trees bore cankers which
were plainly older and larger than those on smaller trees. This points to
early infection accompanied by some deaths among the less vigorous,
smaller trees, resulting in a relatively greater amount of infection in the
remaining larger trees.

Infected black, scarlet and red oak apparently do not die out very freely
in the young size classes, or else infection occurs later in the life of the
tree, for we find the following percentages of Strumella cankering :

538 Connecticut Experiment Station Bulletin 412

D.B.H. Percent cankered

(inches)

1- 5 0.6

6-10 1.7

11-15 1.6

This is a three-fold increase from the first to the second size class. In
contrast, chestnut and white oaks increase very little from the one to five-
inch class, 0.3 percent, to the six to ten-inch class, 0.5 percent.

No significant difference was noted between the number of trees infected
by Strumella canker in the dominant and codominant crown classes and
the intermediate and suppressed crown classes. This was determined for
all species and all areas.

DECAY OF LIVING TREES

All external evidence of decay in the trunk or branches of the trees ex-
amined was noted by species, and the causal organism determined wher-
ever fruiting bodies were available. Out of the 98,420 trees examined,
3,063 or 3.1 percent, showed some decay. Pepperidge showed the greatest
number of stems infected with decay, 12.9 percent, followed by butternut,
black ash, pin oak, beech etc. (Table XVII). Dogwood showed consider-
able decay among the Small Tree Species. The maples had the greatest
number of stems with decay, 5.1 percent, followed by the oaks 2.5 percent,
birches 1.9 percent and softwoods 0.5 percent. Red maple is particularly
subject to decay, 5.6 percent, much more so than sugar maple, 2.5 percent.
This fact, together with the large number of red maples, put the maple
group at the top with regard to decay.

A comparison of the different species on the four forests showed con-
siderable variation in the number of trees decayed. For example, red
maple, present in all forests in large numbers, showed the following percent-
age of decayed individuals :

Tunxis 4 . 4 percent Meshomasic 4 . 2 percent

Pachaug 6.7 percent Cockaponset 11.4 percent

The same was true of many of the other species. The average of all
species on the four forests was:

Tunxis 2 . 0 percent Meshomasic 2 . 3 percent

Pachaug 4 . 2 percent Cockaponset 5 . 2 percent

Where fruiting bodies were present it was possible to identify the or-
ganism causing the decay. The fungus most frequently encountered was
Fomes connatus, causing about three-fourths of all the named decays. Red

Decay of Living Trees

539

Table XVII. Percentage of Living Trees Having Decay

SPECIES

Percent

SPECIES

Percent

Large tree species

Pepperidge

12.9

White Pine

0.7

Butternut

11.1

Pitch Pine

0.5

Black Ash

11.1

Black Cherry

0.4

Pin Oak

11.1

Hemlock

0.1

Beech
Bed Maple

5.9
5.6

Miscellaneous

10.0

Sassafras

4.0

Small tree species

Scarlet Oak

3.8

Dogwood

10.5

Hickory

3.5

Shadbush

3.8

White Ash

3.2

Blue Beech

3.6

Black Oak

3.1

Hop Hornbeam

2.3

Yellow Birch

2.7

Alder

0.7

Tulip

2.7

Scrub Oak

0.6

Sugar Maple

2.5

Striped Maple

0.2

White Oak

2,5

Pin Cherry

0.0

Black Birch

2.1

Mountain Maple

0.0

Chestnut Oak

2.0

Miscellaneous

4.2

Basswood

1.8

Aspen

1.6

AVERAGE-ALL SPECIES

3.1

Bed Cedar

1.6

Species groups

Bed Oak

1.5

Maples

5.1

Gray Birch

• 1.3

Oaks

2.5

White Birch

1.3

Birches

1.9

Elm

0.8

Softwoods

0.5

Miscellaneous species are white cedar, black walnut, spruce, sycamore, willow, sumac, witch hazel
and apple.

maple was most frequently infected by this filngus. Beech, pepperidge,
sugar maple, black and yellow birch, hickory, white, red, scarlet and black
oaks are also susceptible. The sterile form oi Fomes igniarius, (sometimes
called Fomes nigricans in the United States) was the second most abundant
fungus encountered, making up 13 percent of the named decays. Yellow
and white birch were by far the most frequently infected with F. nigricans,
followed by black birch, gray birch, red maple and beech. Other fungi
less frequently found were: Daedalia quercina, Armillaria mellia, Poly-
porus hispidus, Fomes igniarius, F. applanatus, F. fomentarius and F.
fraxinophilus.

Decay enters the tree in a large number of ways: through fire scars,
insect injuries, logging injuries etc. The longer the tree lives, the longer
it will be subjected to accidents which destroy its bark and expose its wood
to the entrance of decay organisms. All trees examined were arranged
by size classes, and the number of trees showing decay in each size class
was determined. All species showed a decided advance in the number of
trees decayed with increase in size. For all species figures were as follows :

D.B.H.

Percent decayed

D.B.H.

Percent decayed

1- 5 inches

2.5

11-15 inches

8.0

6-10 inches

5.6

over 15 inches

14.7

540

Connecticut Experiment Station

Bulletin 412

This increase for the species groups is shown in Figure 103. The data
in the 16 inches and over class are sometimes inadequate, hence there are
irregularities in the figures for maples and birches.

J

1

0.5 6-10 11-15 16+
I NCHES DBH

0-5 6-/0 11-15 ie+
INCHES DBH

^n

0-5 6-10 11-15 16 +
INCHES DBH

SOFTWOODS

Figure 103. Effect of Diameter on the number (percent) of living trees with decay.
Diameter classes 0-5 inches, 6-10 inches, 11-15 inches and 16 inches and over.

Most of the decay occurred near the ground in both small trees, one to
seven inches D.B.H., and large trees, eight inches and over D.B.H. (Figure
104) . In the small trees, of all species, 93 percent of the decay was within
8 feet of the ground and 99 percent within 16 feet. In the large trees, of all
species, the decay was located somewhat higher on the tree, 77 percent
occurring within 8 feet of the ground and 91 percent within 16 feet.

It must be kept clearly in mind that the length of the decayed area and
the cull here discussed refers to what can be seen in the standing tree.
No dissections were made to determine internal decay. Limstrom and
Kuenzel (1937) conclude that about twice as many trees in the stands are
defective as can be detected by observation of external appearance, and
that actual extent of decay is about twice what can be seen from the out-
side. They record a cull of from 8.2 percent in small poles to 31.6 percent
in trees over 9.6 inches D.B.H. of the total merchantable board foot or
cubic foot volume.

Location and extent of the visible decay determined the amount of cull
in this study. If a tree showed external evidence of decay from one to
two feet above the ground, cull was considered as one lineal foot of the

Decay of Living Trees

541

log ; six to eight feet above ground, seven feet ; nine to ten feet above the
ground as one foot, since an eight-foot log could be cut below the cull.

49.52

45.46

41.44

37.40

•

33-36

'

29-32

1
1

25-28

1
1

^21-24

I

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■Hi TREESB INCHES AND OVER

ZD

I \TREES 1 TO 7 INCHES DBH

I

I

0

10

20 30

40 SO 60 70 80

PER

CENT

Figure 104. Location of Decay — height above the ground. Black bar — trees 8
inches and over D.B.H. White bar — trees 1-7 inches D.B.H.

Considering a sound healthy tree as capable of producing a 20-foot log,
the percentage of cull was figured on that basis. That is, of 162 trees
having decay, the extent and position of this decay was such as to make
it necessary to cull 939 lineal feet of log. These same 162 trees, if healthy,
would produce 3240 lineal feet of log. The cull was therefore 29 percent.
If the average length of log produced was less than 20 feet, the cull would,
of course, be higher than 29 percent. The percentage of cull was deter-

542

Connecticut Experiment Station

Bulletin 412

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Frost Cracks 543

mined separately for the small trees, one to seven inches D.B.H., and the
large trees, eight inches D.B.H. and over, for each forest. (Table XVIII).
The large trees had more cull in every case, varying from 4 percent to
14 percent more. The average cull for the four forests was 12.6 percent
for the small trees, and 20.3 percent for the large trees, or 14.3 percent for
all trees.

No attempt was made to determine cull by species, since it was assumed
that the cull would vary according to the frequency with which the species
was decayed. (Table XVII).

The weighted average length of visible decay for all forests and all
species was 2.2 feet, while the weighted average length of cull was 2.9 feet.

This cull figure applies only to those trees showing decay, hence the
cull for the entire stand would be 14.3 percent of 3.1 percent (the percent-
age of trees with decay). For the small trees this would be .4 percent and
for the large trees .6 percent. This cull figure is for visible decay only and
does not include Nectria, Strumella or frost cracks. In comparison with
the cull due to frost cracks, the cull due to decay is greater close to the
ground. This would point to logging injuries and fire scars as points of
entrance for the fungus.

The Connecticut forests sampled would appear to be relatively free
from decay even if the amount found is doubled to take care of invisible
decay, at least in comparison with some of the Missouri forests. The
serious factor is that decay in the relatively young stands of Connecticut
will increase as the stands become older and may become much more
serious than at present.

FROST CRACKS

Radial splits in the trunk and large branches of trees, known as frost
cracks, are caused by sudden changes in temperature and especially very
severe cold. They occur in winter, chiefly during extremely cold winters
such as that of 1933-34 in Connecticut. Stone (1912) states that they
were very common during the cold winter of 1903-1904 in Massachusetts
and that elm is more liable to frost cracks than other varieties.

During the course of the survey 2,522 trees were found to have one or
more frost cracks, or 2.8 percent of all the trees examined. Scarlet oak,
black ash, black oak and red maple are most frequently frost cracked
(Table XIX) among the Large Tree Species, and striped maple, shad-
bush and dogwood among the Small Tree Species. A large number,
17 percent, of the trees which have frost cracks have more than one. Bass-
wood, blue beech, and white birch are most liable to have multiple cracks.
Considering the species groups, the oaks have the largest number, 3.9 per-
cent, with maples 3.7 percent, softwoods 2.1 percent, and birches 1.2 per-
cent having fewer trees cracked. (Figure 105).

Frost cracks range from less than one foot to as much as 45 feet in
length. The average length (weighted average) for all frost cracks was
2.7 feet. The longest cracks were found on elm, black birch and hemlock.

544

Connecticut Experiment Station

Bulletin 412

(Table XIX) . The length of the frost cracks was least in oaks and greatest
in birches, just the reverse of the percentage having frost cracks. (Figure
105). Some individual trees seem to be structurally weak and have from
5 to 15 frost cracks facing in all directions and at different heights on the
bole.

PEP CENT

12 3 4

<0

i . , . i i

1

Wnum'berW

L ENGTH

<0

1*1

i

k
O

.i.i.i.

1

FEET '

Figure 105. Length (in feet) of frost cracks and number (in percent) of trees with
frost cracks— by species groups.

Frost Cracks

545

Table XIX. Frost Cracks in Relation to Tree Species

SPECIES

Trees with

frost cracks

(percent)

Cracked trees with

multiple cracks

(percent)

Length of
cracks

(feet)

Large tree species

Scarlet Oak

5.9

17.5

2.2

Black Ash

5.6

0.0

1.0

Black Oak

4.8

15.3

2.4

Red Maple
Red Oak

3.9
3.6

18.2
16.6

2.7
2.3

White Oak

3.3

17.3

2.4

White Birch

3.3

25.8

3.0

Butternut

3.1

0.0

1.0

Basswood

2.8

30.0

1.7

Tulip
Hemlock

2.6
2.5

23 1
13.1

2.7
4.0

Pepperidge
Beech

2.5
2.1

20.0
15.9

2.4
3.4

Aspen

Sugar Maple
Hickory •
Black Birch

1.9
1.8
1.6
1.5

9.1
19.6
12.0
18.3

2.3
2.2
2^8
5.1

Chestnut Oak

1.5

22.5

3.5

Yellow Birch

1.3

17.0

3.0

Sassafras

1.1

9.1

2.1

White Ash

0.8

10.0

3.5

Elm

0.8

100.0

7.0

White Pine

0.6

0.0

2.0

Black Cherry
Pitch Pine

0.5
0.5

20.0
0.0

3.8
1.5

Gray Birch
Other species

0.3
0.0

7.1
0.0

2.4
0.0

Small tree species:

Striped Maple
Shadbush

8.9
5.5

20.0
16.7

1.3
1.4

Dogwood
Hop Hornbeam
Scrub Oak

3.9
1.4
1.2

5.6

7.7
0.0

3.2
3.0
1.8

Blue Beech

0.9

28.6

3.0

Other species

0.0

0.0

AVERAGES— ALL SPECIES

2.8

17 0

2.7

Species groups:

Oaks

3.9

17.0

2.3

Maples
Birches

3.7
1.2

18.3
17.8

2.6
3.9

Softwoods

2.1

12.5

3.9

D.B.H.

(inches)

Percent
frost cracked

11—15

10.2

over 15

13.3

546 Connecticut Experiment Station Bulletin 412

It is interesting to note that oaks are most frequently frost cracked
and birches least frequently; the oaks have the shortest cracks and birches
the longest. The oaks seem to be unable to adjust themselves to rapid
changes of temperature, hence crack often, but their wood structure is such
that the cracks are short. . The tendency to crack may be correlated with
the late leafing out of the oaks in contrast with the early leafing out of the
birches.

The larger trees were more frequently frost cracked than the smaller
ones:

D.B.H. Percent

(inches) frost cracked

1— 5 1.9

6—10 6.7

Similarly, the dominant trees were slightly more subject to frost crack-
ing than the trees in the lower crown classes. The average of all species
gave the following percentages of frost cracked trees in each crown class :

Dominant 6 . 2 percent Intermediate 4 . 6 percent

Codominant 5 . 6 percent Suppressed 2 . 9 percent

The birches showed this relation more strikingly than did the other groups.

The greater amount of cracking in the larger diameter classes and upper
crown classes seems to substantiate the findings of Busse (1910) who claims
that wind acting on the larger-crowned, more dominant trees, exerts a
tension which, coupled with tensions already present due to temperature
differences between the inside and outside of the tree, brings about the
radial splitting known as frost cracking. He claims that old, stout-rooted,
broad-crowned trees split most frequently and, in younger stands, usually
the stoutest members split.

More than 80 percent of the frost cracks on all species were located
within the first eight-foot log. The height above the ground of over 2,700
frost cracks was recorded in the four forests. This was done by tabulating
the frost cracks in each four-foot section in which they appeared; thus
a 4 to 12-foot frost crack was recorded in the three lowest sections:
0 to 4, 5 to 8 and 9 to 12. The location for all species was as follows:

0 — 4 feet above ground 61 . 8 percent 21 — 24 feet above ground 1 . 2 percent

5 — ■ 8 feet above ground 20 . 7 percent 25 — 28 feet above ground 0 . 6 percent

9 — 12 feet above ground 8.3 percent 29 — 32 feet above ground 0 . 5 percent

13 — 16 feet above ground 4.0 percent over 32 feet above ground 0 . 3 percent

17—20 feet above ground 2 . 6 percent

There were, however, marked differences between the different species
and species groups. Sugar maple has a greater number of cracks close to
the ground while red maple had them scattered more frequently at higher

Frost Cracks

547

levels. Red oak among the oaks had 95 percent located within four feet of
the ground. The oaks as a group had 81 percent within the first four feet,
compared to 43 percent in the birches. In birches a relatively larger
number of cracks were located at the higher levels than in the oaks. M aples
resemble the birches closely. This is shown graphically in Figure 106.
Hickory resembles oak, having most of its cracks close to the ground.
White ash, beech, basswood, hemlock, aspen and tulip resemble the birches.

33. 3 f ]

u

^So-

PER CENT

Figure 106. Location of frost cracks — height above the ground — by species groups .

Since frost cracks do not damage the log severely, the resulting cull is
not great and varies with the closeness of utilization and the skill of the
sawyer. Most frost cracks do not penetrate deeply. Many heal over but
nevertheless cause a defect in the wood. Most trees have but two or three
feet of the log frost cracked and. since most of these cracks are close to the
ground, the actual cull averages 3.7 lineal feet for each tree. Frost cracks
serve, however, as a point of entrance for decay organisms, and in the
field some were observed to be invaded by wood rotting fungi, chiefly
Fomes connatus.

518 Connecticut Experiment Station Bulletin 412

Stone (1912) states that frost cracks are almost always found on the
sunny side of the tree, generally toward the south. The direction of facing
of 2729 frost cracks was noted. The average of all species indicates a
distinctly greater number facing the southerly and southwesterly directions.
(Figure 107). Many trees, 6.3 percent of all, had several frost cracks
listed as facing in "all directions" and these were eliminated from the
direction count. Some frost cracks are found in each compass direction
but the greatest number face the south, west and north. The afternoon
winter sun strikes the bole and warms the trunk most on the south, south-
west and west sides of the tree. This is followed by rapid cooling at night
and, since the widest temperature changes occur on the southerly side of

Figure 107. Direction of facing of frost cracks. Number of cracks (in percent)
facing the eight compass directions indicated.

the tree, the largest number of frost cracks are found on that side. The
large number found on the north side may be partly due to the tendency
of the observer to read north, east, south and west more frequently than
the in-between directions, or they may be partly due to cold winds from
the north cooling off that side of the tree very rapidly.

The irregular character of the forest with its various slopes, exposures,
holes in the canopy and chances for reflected heat probably accounts for
the fact that many of the cracks are on the northerly, easterly and north-
westerly sides of the tree. Stone's (1912) observation that frost cracks
are almost always found on the sunny side of the tree indicates he probably
observed only open grown shade trees since he also says elm is particularly
susceptible to cracking, a fact not substantiated by our observations.

Top Damage

549

Each of the four forests had the greatest number of cracks to the south
or southwest. The different species groups also favor these directions
except the birches, which have the largest number of cracks facing the
north followed by the east, the west and the south.

The relation between number of trees with frost cracks and the exposure
of the plots on which they grew was determined for 799 trees on the Tunxis
Forest. There was no relationship; that is, there were no more frost
cracked trees on plots facing the south and southwest than on plots facing
in any other direction. Probably many other factors enter in to obscure
any effect of exposure on number of cracks.

TOP DAMAGE

Breakage within the crowns of the trees examined was usually due to
glaze or sleet storms although logging injury was also present. Most of
this damage occurred on the Tunxis Forest where a severe glaze storm on
November 26-29, 1921, occurred. This storm broke the tops out of mand
trees. The species most frequently damaged were in general weak-woodey
or slender-twigged species. Damage by top breakage averaged 1.6 percent
for all species examined. Those most frequently damaged were:

SPECIES

Black ash
Basswood
Elm

Hemlock
Bed maple
Hop hornbeam
Yellow birch
Black cherry

Percent damaged

11.1

4.4
3.9
3.6
3.4
3.4
3.0
2.9

The oaks were less frequently damaged :

SPECIES Percent damaged

Bed oak
Tulip

Chestnut oak
Gray birch
Aspen
Pepperidge
White pine

0.6
0.6
0.5
0.5
0.5
0.4
0.4

SPECIES

Percent damaged

Beech

2.7

Sugar maple
White birch

2.4
2.0

White ash

1.7

Black birch

1.4

Butternut

1.4

Striped maple 1 . 1

SPECIES

Percent damaged

Hickory
Sassafras

0.4
0.2

Dogwood
Scarlet oak

0.2
0.2

White oak

0.1

Black oak

0.1

In general, this agrees with the results of Downs (1938) except for hem-
lock which he lists as resistant to breakage. It is likely that much of the
breakage observed in hemlock on the Tunxis was due to injury received
during logging off of the overstory.

A different type of injury characterized by a dying of the tops occurred
in 0.3 percent of the trees examined. Much of this was probably caused
by drought. The oaks were most frequently affected. This dieback in
oaks was previously studied by the junior author and found occurring on
oaks in Connecticut hardwood stands. Other species such as black ash,
butternut, basswood, sugar maple, black birch, white ash, black cherry
and beech were found to have a small amount of dying back of the tops.
Black ash often dies back under Connecticut conditions.

550

Connecticut Experiment Station

Bulletin 412

MECHANICAL INJURIES

Injuries brought about through logging operations, rubbing of one tree
against another ; falling trees or other mechanical causes have been grouped
under the heading of mechanical injuries. They affect 1.7 percent of the
trees examined. They afford a means of entrance for decay organisms.
The weak-wooded, thin-barked species tend to be more frequently affected
than other species. Those most frequently injured were:

Basswood 5 . 1 percent

White pine 2 . 9 percent

Red maple 2 . 8 percent

Those less frequently injured were:

Chestnut oak 0 . 6 percent

Black oak 0 . 7 percent

Red oak 0 . 8 percent

Beech
Black birch
White birch

White oak
Scarlet oak
Hemlock

2.3 percent
1 . 9 percent
1 . 7 percent

1 . 1 percent
1 . 3 percent
0.9 percent

MISCELLANEOUS LESIONS

On many trees in the forest there are small oval lesions where the bark
has died and the dry, hard wood is exposed. They occur chiefly on the
lower part of the bole. What causes them is not known, probably there
is a variety . of causes. They are present, nevertheless, in considerable
numbers and since they all furnish a point of entrance for decay fungi they
are a potential danger. The most striking fact was their wide universal
distribution in all the forests sampled. Out of the 98,420 trees examined,
3,533 trees, or 3.6 percent, had one or more of these lesions. The second
striking fact was that hickory and red maple were by far the most fre-
quently affected, 11.0 and 8.7 percent respectively. This was true of each
of the four forests. They were followed by:

Blue beech
Beech
Scarlet oak
Aspen

6 . 8 percent Striped maple 3 . 4 percent

3 . 7 percent Red oak 3 . 1 percent

3 . 7 percent Black oak 2 . 3 percent

3 . 6 percent N Sugar maple 2 . 2 percent

BORER INJURY

Injury by borer was evident in several cases but was almost confined to
red and sugar maple which made up 95 percent of the cases. Red maple
had 4.4 percent of its number infested and sugar maple 0.8 percent. The
average for all species was 1.0 percent. Decay, Fomes connatus, was in a
few cases associated with maple borer injury.

FIRE SCARS

About 1.0 percent of the trees examined had evidence of fire scars at
their base. This number may not represent the average amount of fire
scarring in the forest, since burns on the State Forest are usually clear cut,
shortly after the fire, and planted to conifers. Such areas were not sampled.
Recent light burns which might not yet be cut were probably not sampled
by the observer. However, since the areas mentioned are small in extent,

Fire Scars

551

the figure of 1.0 percent is probably but slightly below the true average.
The figures as given do not necessarily represent the relative susceptibility
of the various species. Tlys is shown by the frequent scarring of the oaks,
1.3 percent, a much more resistant group than maples or birches. The
generally drier character of the southern and eastern forests, where oak
is abundant, probably accounts for the greater amount of fire scarring of
the oaks. Relative susceptibility could be obtained only by comparing
the various species under uniform conditions as to intensity and time of
year of the burn.

The figures do, however, represent the conditions as they exist on the
state forests at the present time.

The species most frequently fire scarred were :

SPECIES
Scarlet Oak
Aspen
Pepperidge
Red Oak
Black Oak
Red Maple
White Oak
White Ash
Pitch Pine
Gray Birch

Percent
1 . 9 percent
1 . 4 percent
1 . 4 percent
1 . 3 percent
1 3 percent
1 . 1 percent
1 . 1 percent
1.1 percent
1 . 1 percent
1 . 0 percent

SPECIES
Yellow Birch
Sassafras
Tulip

Black Birch
Hickory
Basswood
Elm

Shadbush
Chestnut Oak
Sugar Maple

Percent

1 . 0 percent
1 . 0 percent
1 . 0 percent
0 . 8 percent
0 . 8 percent
0 . 8 percent
0 . 8 percent
0 . 8 percent
0 . 6 percent
0 . 4 percent

The oaks were most frequently scarred, 1.3 percent, followed by:

Maples 1 . 0 percent Birches 0 . 8 percent

Softwoods 0 . 2 percent

Most of the fire scars were from one to two feet in length and were nearly
always located at the base of the tree.

DISCUSSION

The summation of all the diseases and defects encountered in
the survey showed 22.1 percent of the trees affected, (Table XX).
This figure included about 3 percent of duplication, where a tree had two
or more defects and was listed under each. That is, an individual tree
might have had Nectria canker and also a broken top. It would be listed
under both headings. Deducting this amount of duplication we find that
about 19 percent of the total tree population examined had one or more
defects. This does not include such bole defects as lean, crook, branchiness
or fork, which would raise the figure considerably. These defects, coupled
with an abundance of poor species present in the stands, make the problem
of picking an adequate number of crop trees per acre a difficult one.

552

Connecticut Experiment Station

Bulletin 412

The damage to the tree and to the stand varies with the dif-
ferent defects and must be borne in mind in judging their serious-
ness. The most abundant species in the forest are arranged in Table XXI
according to the prevalence of each of eight different diseases and defects.
Picking the five highest species in each defect, we find that red maple has
a considerable number of the six defects listed: decay, frost cracks, top
damage, mechanical injury, lesions and fire scars. Scarlet oak also has
an abundance of the following six: Nectria, Strumella, decay, frost crack
lesions and fire scars. Beech is next with four, and sassafras, aspen, black
oak and red oak with three each. From the standpoint of diseases and
defects only, we find that these species are undesirable, while white birch,
white ash and sugar maple are comparatively free of defects. Keeping in
mind the varying seriousness of the different defects, a general idea of the
relative value of the different species can be obtained.

Table XX. Summary of Diseases and Defects.

Disease or Defect

Number of Trees Defective

Percent

Nectria canker

5721

5.8

Miscellaneous Lesion

3533

3.6

Decay

3063

3.1

Frost Crack

2522

2.8

Top Damage

1921

2.0

Mechanical Injury

1684

1.7

Borer Injury

963

1.0

Fire Scar

935

1.0

Strumella Canker

215

0.2

Miscellaneous

1170

1.2

Total

21,727

22.1

Many factors determine the value of a species in forestry, chiefly the
utility of its wood and its reproductive ability. One of these factors is its
susceptibility to diseases and defects. Table XXI helps to evaluate the
principal species in Connecticut forests from the standpoint of this factor.

Discussion

553

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Red Maple
White Oak
Red Oak
Black Birch
Scarlet Oak
Gray Birch
Hemlock
Hickory
Yellow Birch
Beech

Sugar Maple
White Ash
Chestnut Oak
Black Oak
White Birch

Aspen

Black Cherry
Sassafras

554 Connecticut Experiment Station Bulletin 412

SUMMARY

1. A field survey of diseases and defects in Connecticut forests was made

from 1934 to 1936. The survey covered twelve forests, four of them
intensively.

2. Tenth-acre plots were laid out in practically all forest types and age

classes in the proportion in which they existed in the forests ex-
amined.

3. Nearly 14,000 acres of forest were sampled with 1256 plots, one plot

for each 11 acres. Over 98,000 trees were examined.

4. An average of 784 trees, one inch D.B.H. and over, was found per

acre of forest with an average D.B.H. of 4.4 inches, and an average
basal area of 81.1 square feet per acre.

5. On the basis of basal area, red maple, red oak, hemlock, white oak

and scarlet oak were the most abundant species. About 50 percent
of the basal area of all species was in trees eight inches and over
D.B.H.

6. On the basis of number of stems, red maple, white oak, red oak, black

birch and scarlet oak were the most abundant species.

7. The oaks formed 32 percent, maples 24 percent, birches 18 percent

and softwoods 7 percent of the number of stems present in the four
forests.

8. The northern forest (Tunxis) was heavy in maple, hemlock, birch and

beech while the southern forests (Meshomasic, Cockaponset and
Pachaug) were heavy in oaks and hickories.

9. The percent frequency distribution of red maple was highest, this

species appearing on 91 percent of the plots; red oak 71 percent,
white oak 67 percent; black birch 65 percent and hickory 47 per-
cent.

10. Cankers caused by Nectria spp. were the most abundant defect en-

countered. They occurred on 5.8 percent of all trees examined.
Pepperidge 21.9 percent, black birch 15.4 percent, sassafras 13.6
percent, gray birch 13.3 percent and black cherry 10.3 percent were
the species most frequently cankered.

11. Birches were most frequently Nectria-cankered, 12.5 percent, in the

order black, gray, yellow and white. Maples were less frequently
cankered, 6.1 percent, in the order mountain, striped, red and sugar.
Oaks were least infected, 3.6 percent, in the order scarlet, black,
red, white, scrub, chestnut and pin.

12. Several weed species, such as mountain maple, 58.8 percent, dogwood

47.9 percent and striped maple 27.6 percent, were frequently infected
with Nectria and may serve as a source of infection for more valuable
species.

Summary 555

13. Red maple 1.2 percent and black birch 1.1 percent, because they are

so abundant in the stand and are also rather heavily infected, were
the most frequently encountered Nectria-cankered species in the
forest. Out of every 100 cankered trees encountered, 20 would be
red maple and 18 would be black birch.

14. Nectria cankered trees were widely and generally distributed

throughout the forest but they were not uniformly distributed,
being very abundant in some limited areas and very sparse in others.

15. Eighty percent of the lightly Nectria cankered plots contained 40

percent of the cankered trees, while 2.4 percent of the heavily in-
fected plots contained 14.8 percent of the cankered trees.

16. Most of the Nectria cankers were located low on the bole of the tree.

In the oaks 97 percent, in the maples 86 percent and in the birches
51 percent were located within eight feet of the ground.

17. Nectria cankers seem to start early in the life of the tree except in the

birches where their location at high levels also indicates infection
later in the life of the tree.

18. Nectria cankers on the branches occurred on only 4.8 percent of the

trees which were cankered. They were most abundant on the same
species on which cankers appeared most frequently: black birch,
pepperidge and yellow, white and gray birch.

19. The number of individual Nectria cankers per tree averaged 2.9 for

all species. The birches had the greatest number per tree, 3.9,
followed by maples, 2.2 and oaks, 2.0.

20. The maples and oaks showed a greater number of trees having one

to two Nectria cankers than birches; while birches shoAved a greater
number of trees with three to many cankers than maples or oaks.

21. There is a decrease in the number of Nectria cankers per tree with

increased diameter and in the upper crown classes in the case of
maples and oaks. The reverse is true in the case of birches.

22. Eighty-four percent of the Nectria cankers examined were not fruiting

at all; 5 percent were fruiting sparsely, and 11 percent abundantly.
An increased fruiting was noticed in the spring but not in the fall.

23. Many Nectria cankers were associated with old branch stubs as a

possible avenue of entrance while others were associated with borer
injury, frost cracks, rubs and mechanical injuries. The avenue of
entrance could not be determined in many cases.

24. The number of dead trees on which there were Nectria cankers in-

dicated that, in birches particularly, Nectria may be the cause of
death. More large sized dead birch trees with cankers on them
were found than either maples or oaks. Oaks seem often to be
killed by Nectria cankers when young; maples seem to be able to
outgrow the disease while birches often die from Nectria canker
attacks.

556 Connecticut Experiment Station Bulletin 412

25. Sixty-five percent of the Nectria infected trees were under 25 years

old. A greater number of older birches were cankered than either
older oaks or older maples.

26. Birches and oaks show a greater amount of Nectria cankering with

increased diameter, whereas maples show a lesser amount.

27. Birches and oaks show a greater amount of Nectria cankering in the

higher crown classes, whereas maples show a lesser amount.

28. Origin of the tree, whether sprout or seedling, had no effect on the

amount of Nectria canker.

29. The hardwood swamp type had the greatest percentage of trees with

Nectria cankers followed by the mixed hardwood type, old field
type and the softwood-hardwood and softwood types.

30. There was a slight decrease in the amount of Nectria infection with

increased density of the crown canopy.

31. There was no relation between amount of Nectria infection and the

age of the stand.

32. There was no relation between Nectria cankering and plot exposure.

33. In the case of seven species examined there was a greater amount of

Nectria infection on poor sites than on good. This was particularly
pronounced in the birches.

34. Comparing the species groups,birches made up the smallest percentage

of the total population but the largest percentage of the species
Nectria-cankered, and also of the total population cankered. Oaks
were just the opposite, making up most of the stand but the least
of the species Nectria cankered and of the total population cank-
ered. Maples were intermediate between birches and oaks.

35. Cankers caused by Strumella coryneoidea affect 0.2 percent of the total

tree population and 0.6 percent of all oaks examined. The oaks
ranked in the order of decreasing infection: black, scarlet, scrub,
red, chestnut and white.

36. Sixty-nine percent of the Strumella cankers were located within eight

feet of the ground.

37. Strumella cankers ranged from one to eight feet in length, the weighted

average length being 1.8 feet.

38. The larger trees were more frequently infected with Strumella cankers

than the smaller trees. There was no difference in the amount of in-
fection between the upper and lower crown classes however.

39. Decay was found in 3.1 percent of the living trees examined. The

maples showed the greatest number of stems with decay, 5.2 per-
cent, followed by oaks, 2.5 percent, birches 1.9 percent, and soft-
woods, 0.5 percent.

Summary 557

40. Pepperidge, 12.9 percent, beech 5.9 percent, red maple 5.6 percent,

and sassafras 4.0 percent are particularly subject to decay.

41. Fomes connatus was the most frequently encountered fruiting decay,

attacking chiefly red maple.

42. There was an increase in percentage of trees decayed with increase in

diameter.

43. Most of the decay was close to the ground, 77 percent occurring within

eight feet of the ground in the case of the larger trees, eight inches
D.B.H. and over.

44. The cull due to visible decay was, 4 percent of the small tree population

and .6 percent of the large tree population.

45. Frost cracks were found on 2.8 percent of the trees examined. Oaks

had the largest number (percent) of trees with frost cracks but had
the shortest cracks. Birches had the smallest number (percent)
with frost cracks but the cracks were longest. The average length
of frost cracks was 2.7 feet.

46. The larger trees and those in the upper crown classes were more fre-

quently frost-cracked than the smaller, lower crown class trees.

47. Over 80 percent of the frost cracks are located within eight feet of the

ground.

48. The greatest number of the frost cracks were found on the south and

southwest sides of the trees.

49. Top damage, due to ice storms, was present in 1.6 percent of the popu-

lation. The species are listed in the order of frequency of top
damage. Die-back due to drought was also encountered.

50. Mechanical injuries due to logging operations and other causes

occurred on 1.7 percent of the stand.

51. Lesions, borer injury and fire scars were encountered in varying

numbers.

52. Red maple, scarlet oak and beech are subject to many different defects

while white birch, white ash and sugar maple are relatively free
from defects:

53. About 19 percent of the trees in the average forest had one or more

defects or diseases.

558

Connecticut Experiment Station

Bulletin 412

Common and Scientific Names of Trees Encountered in the Disease Survey

COMMON NAMES

Alder

Apple

Ash, Black

Ash, White

Aspen

Basswood

Beech

Beech, Blue

Birch, Black

Birch, Gray

Birch, White

Birch, Yellow

Black Walnut

Butternut

Cedar, Bed

Cedar, White (Southern)

Cherry, Black

Cherry, Pin

Dogwood

Elm

Hemlock

Hickory

Hop Hornbeam

Maple, Mountain

Maple, Bed

Maple, Striped

Maple, Sugar

Oak, Black

Oak, Chestnut

Oak, Pin

Oak, Bed

Oak, Scarlet

Oak, Scrub

Oak, White

Pepperidge

Pine, Pitch

Pine, White

Sassafras

Shadbush

Spruce

Sumac

Sycamore

Tulip

Willow

Witch Hazel

SCIENTIFIC NAMES

— Alnus incana

— Pyrus malus

— Fraxinus nigra

— Fraxinus americana

— Populus grandidentata and P. tremuloides

— Tilia glabra

— Fagus grandifolia

— Carpinus caroliniana

— Betula lenta

— Betula populifolia

— Betula papyrifera

— Betula lutea

— Juglans nigra

— Juglans cinerea

— Juniperus virginiana

— Chamaecyparis thyoides

— Prunus serotina

— Prunus pennsylvanica

— Cornus florida

— Ulmus americana and U. fulva
— Tsuga canadensis

— Carya spp.
— Ostrya virginiana
— Acer spicatum
— Acer rubrum
— Acer pennsylvanicum
— Acer saccharum
— Quercus velutina
— Quercus montana
— Quercus paluslris
— Quercus borealis
— Quercus coccinea
— Quercus ilicifolia
— Quercus alba

— Nyssa sylvatica
— Pinus rigida
— Pinus strobus

— Sassafras officinale

— Amelanchier spp.

— Picea spp.

— Bhus spp.

— Plantanus occidentalis

— Liriodendron tulipifera

— Salix spp.

— Hamamelis virginiana

The authority for these names is according to Sargent's "Manual of the Trees of North America,"
2nd edition, 1921 and Gray's "New Manual of Botany," 7th edition, 1908.

Literature 559

LITERATURE

Abell, C. A. Influence of glaze storms upon hardwood forests in the southern Ap-
palachians. Jour. Forestry, 32:35-37. 1934.

Andrews, S. R. The incidence of Nectria canker in the sugar maple-beech-yellow
birch type near Kane, Pennsylvania. Thesis in Library Yale School of Forestry,
New Haven, Conn. 1935.

Ano:\ Information on Nectria canker disease in relation to stand improvement.
Div. Forest Path., U. S. Bur. Plant Indus. Mimeo. February 16, 1935.

Anon. In >rmation on Strumella canker disease in relation to stand improvement.
Div. Forest Path., U. S. Bur. Plant Indus. Mimeo. February 18, 1935.

Bidwell, C. B. and Bramble, W. C. The Strumella disease in southern Connecticut.

Jour. Forestry, 32:15-23. 1934.
Boyce, J. S. Forest pathology. 600 pages. McGraw Hill Book Co., Inc., New

York. 1938.
Busse, J. Frost-, Ring- und Kernrisse. Forstwiss. Centbl. 32:74-84, 1910. Rev.

in For. Quart. 8:239-240. 1910.

Cline, A. C. Forest weeding with special reference to young natural stands in cen-
tral New England. Mass. Forestry Assoc, Boston, Mass. 1929.

Downs, A. A. Glaze damage in the birch-beech-maple-hemlock type of Pennsylvania
and New York. Jour. Forestry 36:63-70. 1938.

Forest disease control in New England. Committee Report, New England Section,
Soc. Amer. Foresters. Jour. Forestry, 33:469-473. 1935.

Grant, T. J. Nectria cankers on Northeastern hardwoods. U. S. Dept. Agr., Bur.
Plant Indus. Mimeo. May 11, 1936.

Grant, T. J. Reduction of Nectria canker in hardwood forests of the Northeast.
Northeastern Forest Exp. Sta. Occasional paper No. 6. 1937.

Hawes, A. F. The present condition of Connecticut Forests, a neglected resource,
pp. 1-78. Published by the State Forester, Hartford, Connecticut. 1933.

Hepting, G. H. Eastern forest tree diseases in relation to stand improvement.
Emergency Conservation Work, Forestry Publication 2:1-28. Revised 1934.

Hough, A. J. Why timber stand improvement? Jour. Forestry 35:813-822. 1937.

Jensen, J. S. Suggestions for weeding in northern hardwoods. Northeastern For-
est Exp. Sta. Occasional paper No. 3. Mimeo. 1935.

Limstrom, G. A. and Kuenzel, J. G. Factors affecting the extent of defect in cer-
tain upland hardwoods on the Clark Purchase Unit in Missouri. Preliminary
report. U. S. Forest Service. Mimeo. March 1937.

Spaulding, Perley. Nectria canker of hardwoods in New England. Tree pest
leaflets No. 10. Mass. Forest and Park Assoc. October 1936.

Spaulding' Perley; Grant, T. J. and Ayebs, T. T. Investigations of Nectria dis-
eases in hardwoods of New England. Jour. Forestry, 34:169-179. 1936.

Stickel, R. W. and Marco, H. F. Forest fire damage studies in the northeast.
III. Relation between fire injury and fungal infection. Jour. Forestry 34:420-423.
1936.

Stone, G. E. Frost cracks. Twenty-fourth annual report. Mass. Exp. Sta., 110-114.
1912.

Welch D. S. The range and importance of Nectria canker on hardwoods in the
Northeast. Jour. Forestry, 32:997-1002. 1934.

6772 0!»6

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