TIiKS IS
On
A STUDY OP THE FRUIT SPURS OP REGULAR BEARING
AN]) OP ALTERNATE BEARING APPLE TREES
Submitted to the
In Partial Fulfillment of the Requirements
For the Degree of
MASTER 2. Sc IENOE
In
SCHOOL OF AGRICULTURE
BY
John Yates MoDonald
*

APPROVED:
Professor of In Charge of Major
Eead of Department
Dean of School of
-
Chairman, Committee on (rath.ate
Students and. &d.vanoed. Degrees

INTRODUCT ION
Unfavorable weather conditions make the apple crop uncertain in many sections.
The habit of alternate bearing seems to be a limiting factor, even more important in other seotions.
This is particularly true of certain varieties.
It was thought that perhaps the physloal charaeter of the fruit spurs cause alternate bearing.
The cause of this malady having been found, the remedy might
8UggeSt itself.
REVIEW O TBE LITERATURE
In his thesis of 1916, A. P. Yeager reports a statistical study of the apple fruit spur.
He finds that as spurs grow older, they bear much less fruit on a given num ber of terminals, the blossoms on the older spurs being lees productive than those on younger ones.
A correlation exists between the rate of growth of a spur and. its productivity.
Successive crops on the same spur cause a decrease in its rate of growth.
Spurs of large diameter produce larger fruit than do small spurs.
Old vigorous spurs are more productive than young ones owing chiefly to the increased number of terminals,
"On the Cause of
Alternate Bearing in the
Apple", is the title of an article by 0. Butler in Bulletin
44 of

the Porrey Botanical Club. He repota that alternate bearing is most common in the apple and pear; but that it is also characteristic, at times, of the plum and cherry.
The habit once acquired seems to be fixed.
Spurs normally do not bear before their third year.
Regular pruning to produce a steady supply of new spurs is the best cure for alternate bearing.
The tree should be kept growing at a rate approximately uniform each season.
OBJECT OP THIS WOIX
An attempt was made to find, certain physical obaracteriatios which would enable one to distinguish spurs of regular bearing from those of alternate bearing apples.
Is there any fundamental difference between spurs of the two types of apples?
Does the same spur bear two or more consecutive years or do different spurs bear their crops in rotation?
What is the normal behavior of spurs of each type?
These are some of the questions to which answers are here sought.
DEPINIT IONS
As used, here, the term apur designates a short growth, lateral to the main branch, growing not over four inches a season.
In the Ben Davis spurs, a seasonal growth of aix inches is allowed.
Longer growths are termed

branches.
The age of a spur includes its first season's growth as one year of its age.
Thus spurs starting one spring are considered. a year old. the following winter.
Pruiting spurs are those which hold. their fruit to maturity or thereabouts.
A barren terminal is one which neither blossoms nor bears fruits during the season considered.
MLT3RI.AL8 A&D METHOD8
Two trees each, of four different varieties, were selected as sources of material.
Shiawassee and Pameuae were chosen as examples of alternate bearers.
Ben Davis was selected. as a regular bearer.
York Imperial was Belooted as an alternate bearing tree, but was found to blossom and. bear so regularly that It was classified as a regular bearer.
Al]. of the trees seleoted. were approxiinately twenty-five years old.
The Ben Davis trees had been badly neglected until the last year.
The other trees bad. received. good. average attention and.
are in the college instructional orchard. at Corvallis.
The Pameuse and. York
Imperial trees are in rather crowded locations; the Shiawassee trees are in the edge of the orchard and are quite vigorous.
Approximately 600 spurs were taken from each tree, the latter being divided into ten sections.
The upper and.
lower portions were each divided. into an east, south, west, and north section; the top and center were kept as separate

sections.
A proportional number of spurs was taken from each part of the tree; thus from a dense top more spurs were taken than from a center having very few originally.
Spurs from each section of the tree were kept separate and labeled.
After being taken to the laboratory, the life
each spur was worked out.
In recording the life history, each spur, or branch of a spur, was recorded on a separate line.
Below is given the life history of a typical spur from Fameuse tree mimber 8.
Section of tree
Upper-west
Performance
1911 1912 1913 1914 1915 1916
0 B 0 B 0
0.
o 0 C o o B
T0fl stands for no bloom, "B" for bloom,
This spur is a
for
alternate bearer, although thus far it has borne but one season.
It i8 but fair to state that one carmot always read, the life history of the spur aoourately from the marks thereon.
The older the spur grows, the more slow is its growth and the more difficult it is to read its life history.
In reading these life histories, doubtless some errors crept in.
These, however,
be compensating, and. the general average should be quite accurate.

PRSE'LTATION OF THE DATA
In selecting tables for pre8entatioll, it seems desirable to omit maiy for the sake of brevity, coneequent1y typical tables are selected. which are representative.
It is difficult to know which tables will be of most value to the reader.
LIFE HISTORIES
Complete life histories of spurs of several different ages are given in Tables I to IV inclusive. A study of these tables shows that spurs seldom bear their first year and. usually decline in fruitfulness as they get old.
As would be expected, the old, spurs are much fewer in number.
Chart I shows how confirmed. these spurs are in their habit of alternate bearing.
Table III, however, shows that the Shiawassee variety formerly bore coneiderable fruit in the "off" years.
It is apparent that the trees studied have been bearing most of their fruit during the even years.
The crops were more evenly distributed some years ago, therefore the habit of alternate bearing seems to be getting more pronounced: this is especially true of the Shiawassee.
Chart II shows that the York
Imperial also has considerable tendency towards alternate bearing.
In 1911, 1912, and 1913 there was little variation in the number of fruits borne by this variety.

ITo.
No.
0
1916 1915 1914
BC
0
BC
0 B C
1 148 23 60 66 148 0 0 122 1 13
2 92 3 50 39 92 0 0 86 6 0
3
4
5
125
56
102 14 17 126 5 2 125 0 0
580
0
530
4
560
0
48 11 36 1 41 7 0 48 0 0
6
Pameuse
7
8
84 12 71 2 73 11 0 83 1 0
186 10 130 47 187 0 0 165 20 0
126 28 78 21 126 0 0 120 6 0
864 247 439 192 846 23 6 805 46 13

Table II, Giving Comp].ete
Performance Records of all Spurs Six Years Old
Tree No.
Variety No.
of
Spurs
Performance
0
27
1916
BC
0
1915 1914
BC
0
BC
40 43 107 0 1 2 26
13.
Shiawassee 1 87
Shiawassee 2 125 29 96 58 180 2 0 16 70 72
Ben Davis
Ben Davis
York Imp.
York Imp.
Pameuse
Pa3neuse
Totals
3
4
5
6
7
8
70
67
153
152
47
772
77 16 11
7].
18
].
81 4 7
86 6
90 87
5
9
63.
21
102 76
9 77 4 1
4 54 103 10
60 114 11 119 57 1 73 86 4
10 33 16 55 1 0 14 28 12
40 51 7 96 0 0 30 56 4
419 443 160 791 175 28 347 377 181
97
1913 1912 1911
00
91958
81 0 0
153 0 0 7 55 63 125 0 0
41 19 14 65 3 2 69 1 0
47 18 10 67 2 66 1
135 18
9 95 52 15 153 0 0
144 10
1 84 59 9 152
0 0
-
45 3 0
81
-
0
-
0
-
4 32 11 47
53.
1$
-
70
-
0
1
0
0
-
743
68 34 343 273
171 769 4 0
0

Table III, Giving Complete Performance Records of Spurs Nine Years Old
Tree No.
No.
1916
Shiawasseel 1
1915 1914 1913
OBO OBO OBO OBO
010 100 001 100
Shiawaaeee 2 16 30 10 3
3].
5 5 33 1 1 20 8 6
3
9
1832165322101641
419
61533923557525532
Yorklinp.
Pameuse
5
Yorklmp.
6
7
8
2
6
1
5
771 530
1000 00
8
130400
252 900 540 900
020
200 110 200
10510
69 128
27 10 112 36 1 127 16 4 112 16
9
oBe
1911
1910
001 001 100
1909 1908
1100
27 1 2 23 3 0 11 8 5
1320 1110
14 4 2 15 1 0
442 811 900
44
2 1 22 6 1 13 5 6 19 3 0 19
012 300110
052 700
010
03
0 0
101 200
600 510
100001100100
8
1.2..
7210 3 342118
53 9 5 57 2 0

Table IV
Variety
Giving Complete Performance Records of Spurs Twe].e Years Old
No.
of
Spurs
Performance
Shiawassee 1
Shiawassee 2
Ben.Davia
York Imp.
Pameuse
Pameuse
3
4
5
6
7
8
1916
OBO
0 1 2 3
1915
OBO
1914 1913
OBCOBC
0 0 0 2 1 3 0 0
3 3 1 7 0 0 0 3 4 7 0 0
1813191215101221.
500311 500500
511 340 700700
8 11 1 16 2 0 12 5 1 14 1 0
320 500 140500
1330 1600 41201600
5522
8 72 8 3 4427 669
3 1
1912 19Th 1910
OBO OBO OBO
003 300 012
141 500 103
12 1 0 8 2 0 4 3 1
600 600 030
051 510 112
0 10 0 0 6 7 2 7 1
,0 5 0 4 1 0 0 3 1 i__ _ii_
12 29 10 23 34 8 57 3
1909 1908 1907 1906
3 0 0 0 0 3 3 4 3 10 0 0
4 0 0 0 0 3 23 1 3 22 2
5 0 1 4 1 0 1312
2 19 6 0
3 0 0 2 1 0 16 5 0 21 0 0
300 111 600 014
900 261 800 114
400 004 470 560
3
1905
055
20 0 1
19 6 0
1].
5 16 0
600
600
0 0
45 0 1 14 17 12 89 30 8 81 29 13
81 27 5

PRODUCTION OF SPURS ACCORDING TO AG3
Table V gives the performance record for all spurs during 1916.
It will be observed that most spurs bear best when from three to aix years old.
The percentage of Ben Davis and York Imperial terminals which fruited during this year was much lower than that of the alternate bearing varieties.
This is but natural since the former varieties had borne more the preceding year.
The older spurs have more terminals and hence more possibilities of bearing.
The very old spurs furnished a strikingly low percentage of fruitful terminals.
The youngest spurs also showed a low production.
Shiawassee spurs here appear to have been the moat productive: this is doubtless due to the favorable location and healthy condition of those trees.

U
Pameuse
Pameuse
1 2
0 35 44
345
44 36
6
39
7
23
8
24 1
2 0 26 42 44 38 32 14 32
6
3 0 10 14 13 9 11 5 12
40
0 0 9
552
34
5016
212
9 5 3
9
0 5 2 9 5 6 7 6
7 2
8
16 26 32 15 28 19 0
0 6 17 17 17 7 2 0
14 19 2 17 22 22 11 2
9 10 11 12 13 14 15 16
'7
25 0 0 0 0 0 0 0
0 58 0 0 0 0 0 0 0
9 0
8400
0 0
00
4 6 8 27 0 0 0 0 0
0 6 6 0 8 0 0 0 2
22 0
0 25
7 0 0 0 0 3 0
0 0 0 0 11 0 9
515
4830313

NUIItIBER OF FRUIT SPURS
It was thought that some varieties fail to produce many fruit spurs on alternate years and. thts cause the tree to bear alternately.
Table TI ind.ioatee that this is not the case.
Although there is considerable variation in the number of new spurs produced each year, this variation does not seem to be correlated with the amount of fruit borne.
For some reason the Ben Davia seems to have very few young spurs.
This is probably due to the run down condition of those trees.

Table VI, Giving the Number of Pruit
Spurs According to Their Ages
'Variety
Shiawassee
Ben Davis
Ben Davis
York Imp.
York Imp.
Pameuae
Pameuse
Totals
No.
of
Tree
1
Age of Spur
1 2 3 4 5 6 7 8 9 10
5'?
78 148 99 72 87 19 20 16 3
44
117 92 117 32 126 7 11 1 6 2
3
4
5
12 130 125 113 86 70 30 19
6
61
9
15
32 56 92 106 67 13 28 19 10
44 48
66 98 153 46 5 2 6
6
7
8
48 64 84 46 80 152 38 21 1 1
208 153 185 120 60 47 20 1 6 1
84 149 126 91 68 71 36 1 5 7
520 767 864 744 602 772 209 106 59 49
11 12 13 14 15 16 17 & over
1 31 0 0 00
0 2 0 0 0 0 0
10 5 3 0 0 0 0
15 1 2 0 0 0 0
5 3 7 2 8 2 8
9 8 7 2 5 8 £
1 3 2
4 12 0
6 6 1
0 0 0
45 37 22 10 19 11 16
2
0

Table VII ahowe that the older spurs gradually become more branched and therefore have more terminals,
There is no appreciable amount of branching until spurs are three years old.
The Pameuse shows somewhat lees branching than the other varieties.

Table VII, Giving Niunber of Terminals :tor
Spurs of Different Ages, in 1916
Variety
Shiawassee
Bhiawaseee
Ben Davis
Ben Davis
York Imp.
York Imp.
Pameuse
Pameuse
No. of
Tree
1
1
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
3.
1
1
1
1
3.
1
2
1
Age of 3pur
3 4 5 6
3.
1.1 1.1 1.2
1.4
1.9
2.?
2.6
1 1.].
1.5 1.5
2
7 8
2.3 1
9 10
1.1
3.
1.2
1.3
1.5
2 2.3 2.5
2.6
1 1.1
1.3
1.5 2.4 2.8 3.6
4.6
11.11.21.21.42.24
3
1 1.3
1.3
1.2 1.9
1.9
2 1
1 1.1
1.3
1.3 1.4
3.
1.5
4
1 1.1
1.4 1.4
1.1
1 2 2.3
11 12 13 14 15 16 17 & over
71
3 0 0 0 0
0
2.4
3.6
0 0 0 0
4j4 3.30
0 0 0
0
4.3
5 5 0 0 0 0
3.2
2.3
2.6
6 3.6
3.5
6.2
3.1
2.5
3.1
3 5.6
4.5 10.2
1 1.6
2
1.2
3.
0
2.6
0
1.6
8
0 0
4.5
0

LOCATION AS A FACTOR I1 PRODUCTION
As a means of studying the influence of location on the productivity of fruit spurs, those from the various sections of each tree were grouped together and compared.
The upper and. lower portions of each tree were divided into an east, south, west, and north sections; the top and oenter spurs were also kept separate.
In Tables VIII and
IX, a study is made of the comparative productivity of spurs from each section.
The lower eastern part of these trees appears less productive, but doubtless this variation is within the range of experimental error.
Young spurs of the 1Tqrk Imperial and Ben Davis are less productive than those of the other varieties.
Although great variation is to be noted. in this table, it is doubtless due to the small number in ech group and hence the chance for a large experimental error.

Table VIII, Showing Peroentage of Pruiting Terminals in 1916, in Different Parts of the Tree:
AU Spurs Listed are Three Years Old.
Variety
Shiawaeeee
Ben Davis 3
Ben Davis
Pameuse
Painenee
Average
4
5
6
7
8
1
2
No.
Looat ion
Upper
B.
S.
W.
N.
33 55 48 50
--58 26
Lower
B.
S.
W.
N.
20 50 46 25
0 50 50 50
20
50 0 5 0 0 0 44 50
-
0
0 0 0
--
0 0 000
16-.
0 0
0 0 0 0 0 0 0 0
32 36 36 16 25 17 57
18 22 22 25 11 0 0 25
21 18 15 13 8 16 19 23
Top
38
41
16
0
0
4
22
Center
43
50
--
0
0
0
27
16 15

Table IX, Showing
Fruiting Terminals in 1916, in
are Five Years Old
Variety
Shiawassee
Shiawassee
Ben Davis
York Imp.
Tree
Upper
B.
3.
W.
N.
Location
Lower
1
B.
8.
W.
N.
48 50 40
2
3
4
16 40 27 0
50 0
6
0 86
6 17 9
0 0 25 0
20 -
00
0 50
-
8
8
17 0 0
0
0
7 5
6
0
7 33 16 8
9000
40 33 33
9 16 0
Pemeuse
Pamenee
Average
7
8 18 40 36 0
13 20 30 6
0
11 20
10
8
9 0
8 12 16
20 10 9
Top Center
50 40
33 80
25
0
0
0
0
0
0
0
7 0
16 18

SUCC1SSIVE BLOOMING
Terminal8 which have bloomed or fruited two or more consecutive years are listed in Table X.
Whether a bloom or fruit was followed by a bloom or fruit the sueoeeding year, it is listed here.
It is obvious that the
York Imperial "repeats" far more than any other variety.
The Ben Davis does this rarely, the Pameuse and 8hiawaaeee almost never.
Occasionally one terminal of a York Imperial spur will bloom five consecutive year.
Very rarely a
Pameuse terminal will bloom two consecutive years.

Table X, Showing the Number of Terminals Whioh have Blossome& Two or More Consecutive
Teara on Spurs o:f
Ages
No.
of
Tree
Variety
Shiawasseel
Shiawaasee2
3
4
5
6
'7
Fameuse 8
Age of
Spur
1 2 3
Years of
Conaeoutive2 3 3 2 3 3 2 3 3
Blooming
0
000 00 00 00
0 0 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0
0
0
0
0 0
0 0
0
0 0
0
0 0 0
0 0 0
0
0
0
0
0 0
0
0
0 0 0
3
9
0
1
0
0
0 0 0 0 1 0 0
0 0 0 0
5 6
'7
8 9 4
233233 233 233 233 233
000 000000000000000
2070201242632918133 430 210
000 000000100100 900
1].
10 12
233 233 233
000000 000
000 0 00 000
000 000 000
000000000
000 410 620
000 000000

MORPHOLOGICAL VARIATIONS
Accurate measurements were not taken, but it was apparent that most spurs grow nore during the season in which they bloom than d.uring a barren season.
During exceptional years a barren terminal will grow four inches, a bearing terminal usually grows less than one inoh during a season.
Prequently during an "off" season a terminal will grow lees than one-fourth of an inch.
Shiawassee and. Pameuse spurs are much alike; neither live to be very old and their growth is quite irregular.
York Imperial spurs live to be the oldest of those studied; they usually grow at a very slow but steady rate.
is very conmion in these.
Consecutive blooming
Owing to their stubby scarred nature, these spurs are easily distinguished from the others studied.
Large knobs where the fruits were borne are the most striking features of the Ben Davis spurs.
Their growth is long, but irregular, and they can be easily distinguished from the others.
DISCUSSION OP RESULTS
Alternate bearing is plainly evident in the life histories here recorded.
This habit is much lees marked in the York Imperial and Ben Davis varieties.
Blossoming on consecutive years is normal in the York Imperial, but

not found at all in the Shiawassee.
A Pameuse spur which
:fails to bloom during the year when most of the apurs bloom, will very rarely bloom the following "off" year.
Thus the condition causing alternate bearing is not limited to the spur.
Zven the York Imperial and Ben Davis trees tend to this habit.
There is a constant supply of new spurs each year; their lack, therefore, is not the cause of alternate bearing.
Although varying with the age of the tree, the habit seems to be not correlated with the age of the spur.
That some varieties bear most of their fruit on alternate years does not appear to be because their spurs are different from other varieties.
Some spurs may bloom but once in six or more years, yet this bloom will usually ocme during the productive year.
This study confirms the belief that the habit of alternate bearing becomes more pronounced as the trees grow older.
As spurs grow older, they develop new terminals, but gradually become less produotive.
GFRAL OBS1RVATIONS
The writer was raised in the
Shenandoah Valley in
West Virginia.
There the York Imperial is the moat impor-.
tan.t apple.
There this variety is notorious for its habit of alternate bearing.
At Corvallis this variety was found to be the moat regular bearing one examined.
Therefore it is obvious that some varieties bear regularly in some see-

tione but not in others.
Most everyone has noticed that some Ba].d.wins are notoriously shy bearers on off years, while others bear good. crops annually.
The writer has observed. that some varieties of crab apples, Yellow Transparent, and. Early Earvest apples are particularly susceptible to alternate bearing.
The habit is undoubtedly worse in neglected. orchards.
Alternate bearing is therefore due tO pbsiologica]. differences rather than anatomical or morphological differences in the fruit spurs.
Some trees are much more liable to get in this condition than others.
Since alternate bearing is due to a condition, it should be possible to remove or prevent the occurrence of this condition.
Good culture and regular pruning are apparently the best preventatives.
Thinning the fruit wil].
not correct the habit after it is once formed according to work done at the Geneva station in 11ew York.
Thousands of well oared. for orchards testify to the efficacy of the remedy suggested, by large annual crops for the owner.
8UJi1MARY
Alternate bearing is a common habit of the spur, but more particularly of the tree.
It exists in varying degrees and is much more pronounced in some cases than in others.
As trees grow old the habit appears and may become confirmed.

Old Spurs put out new branches but gradually become less productive.
A large number of new fruit spurs are formed annually on trees of both types, i.e., regular and alternate bearers.
Location of the spurs does not seem to influence their productivity.
The habit of alternate bearing appears to influence the tree rather than the spur.
It is a condition which usually can be prevented, if not cured, by good cultural methods.

Table X11 Giving the Life Histories of the S:pars
Shown in the Plates
1916 '15 '14 '13 '12 '11 '10 '09 '08 '07 '06 Pig.
No.
1.
Variety
Shlawassee 0 0 B 0 B 0
2.
Shlawasese 0
0
0
0
0
0
B 0 B 0 B 0
B 0 C 0 B 0
0 0 0
3.
0
0
0
B
0
0
0
0
0
0
0
0
0
0
0
0
B 0 B 0 0 B B
B 0 B 0 0 B B
B 0
4.Yorklmp.
0
0
B B 0 C 0 C 0 0 C B
B B 0 0 B B 0 0 B 0
6.
Pameuse
C
C
0
0
C
C
B 0
0
0
C
0
0
0
C 0 0 0
B 0 B 0
B 0
0
0
0
0
0
0
0
0
C
0
B 0 B B 0
9.
C
0
B
0
0
0
0
0
C B 0
'05 '04 '03 '02 '01 '00
0 BC 0
B 0 B 0 C 0
B B B 0
4

ACK!IOWIZDMENTS
To Professor 0. I. Lewis, Chief of the
Division of liortiou].ture, the writer wishes to express his appreciation for the permission to carry on this work.
Thaiiks are due abtandantly to Professor V. R. Gard.ner of the same division; he not only suggested the problem, but gave frequent valuable suggestions upon the details of the work.
The writer wishes to t1ank the other assistants in the laboratory for their cordial support and. valuable criticisms.

DSCRIPTIOI OP PLATES
Pig. 1.
This is a typical alternately blooming spur of a
Shiawassee.
Six years old. it bore its first fruit last summer.
This spur is of the same variety, but is fifteen
Pig. 2.
yeare old.
The short side of this s:pur is eight years old and only two inches long.
Pig. 3.
A typical spur of the York Imperial.
Although this has bloomed thirteen times, but one fruit has been
Pig. 4.
borne.
Another spur of the same variety: it has not branobed at aU although seventeen years old.
This one baa borne three fruits.
Pig. 5.
One part of this York spur grew eight inches in one season.
The email side branch is nine years old. and only two and one-half inches long.
Pig. 6.
This is a very unusual Pameuse spur.
In 1913 it blossomed after bearing fruit the previous year, on the same terminal.
This young spur has already borne four apples.
Pig. 7.
This Pameusa spur is eight years old.
After a slow and irregular growth it grew fourteen inches last summer.
Pig. 8.
Here we have a Ben Davis spur thiob shows little or no tendency to alternate bearing.
Two separate times this spur has bloomed on two consecutive years.

Fig. 9.
This is another typical Ben Davis.
After two barren years all three terminals bloomed last season and. twelve fruits were borne.

Fig. 1.
FIg. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.

hg. 7.
Pig. 8.
Pig. 9.