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APPLE POLLINATION STUDIES
IN THE
ANNAPOLIS VALLEY, N.S.
CANADA
1928-1932
UNDER THE DIRECTION OF
W. H. BRITTAIN
PROPERTY OF LIBRARY
DEPARTMENT OF AGRICULTURE, OTTAWA
AL32 25169-ISM-5fea^
PLEASE RETURN
DOMINION OF CANADA
DEPARTMENT OF AGRICULTURE
BULLETIN No. 162— NEW SERIES
630.4
C212
B /£2
new ser.
Published by direction of the Hon. Robert Weir, Minister of Agriculture.
May, 1933
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CONTENTS
Page
Popular Summary 5
Foreword 11
Acknowledgments and List of Workers 12
I. Introduction 13
(a) The Apple Industry in Nova Scotia 13
(b) Factors Other Than Pollination Affecting Fruit Production 18
II. Pollination and Fruitfulness in Apples. . 24
(a) The Process of Pollination and Fertilization (Definitions) 24
(b) The Pollination Problem 25
(c) Causes of Unfruitfulness 26
(d) Percentage of Fruit to Flowers Required to Give an Economic Yield 29
III. Experimental Studies in Apple Pollination 31
(a) Conditions for Cross-Pollination 31
(b) Previous Work with Bees as Pollinators under Controlled Conditions 31
(c) Experiments in Bees and Pollination (Tent Studies) 32
(d) Studies in the Inter-fruitfulness of Standard Varieties 37
(e) Pollination Tests with Blenheim and Stark 74
(f) Planning the Orchard 82
(g) Relation of Fruit Set on Entire Tree to that on Individual Limbs or Spurs 86
(h) Over-pollination 86
(i) Temporary Provision of Pollen 87
(j) Inhibiting Effect of Unfruitful Pollen 89
(k) Variation in Self-Fruitfulness 90
IV. Field Studies in the Use of Insects as Orchard^Pollinators 91
(a) Introduction 91
(b) General : : 91
(c) Insects Concerned 91
(d) Relative Value of Insect Pollinators 100
(e) Utilization of Hive Bees as Orchard Pollinators 134
V. Studies in Bee Poisoning as a Phase of Orchard Pollination Studies 158
(a) Introduction 158
(b) Historical 158
(c) Development of Problem 161
(d) Experiments in Bee Poisoning 163
VI. Literature Cited 190
Index 195
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ERRATA
Page 5, line 23, for " anthers discharge their pollen shortly before the stigmas
are receptive " read the stigmas become receptive shortly before the
anthers dehisce.
Page 8, line 19, for " apple " read pollen, and in line 26, for " later" read earlier
and for " earlier " read later
Page 12, line 23, for " C. A. Ativood " read C. E. Atwood.
Page 13, linel$h for " south " read north.
Page 14, fig. 2, for " 7 mile— I inch " read -26"=1 mile.
Page 19, line 39, for " 7332" read J0SJ.
Page 29, line 22, for " in the case " read is the case.
Page 44, line 16, for " aberation " read aberration.
Page 46. fig. 11, for top percentage figure " 85 " read 90.
Page 48, line 3, for " varied " read varies.
Page 50, line 5 and 6, for " as in the case of the " read due to certain.
Page 86. line 21, for " each year/' read each alternate year.
Page 102, fig. 40, for " Scale 4"—l m^e " read scale -66"=1 mile.
Page 104, fig. 42, for u 4" = 1 mile" read -55"— 1 mile.
Page 104, fig. 43, for "Scale 4"—l mile" read scale -oo" = l mile.
Page 108, line 6, for " over winter" read overwinter and in line 33, for " 1928-
31 " read 1928-1930.
Page 116, line 1, for " 5300A " read 5300A and in line 3. " 5530A " read 5530A.
Page 120, line 4, for " falls " read falling.
Page 129, line 1, for " 22." read 22y
Page 144, line 47, for " result " read results.
Page 153, line 20, for " 1.23" read 1.94, and in line 40, for " 1.27" read 1.94.
Page 155, line 26, omit comma after " may."
Page 159, line 30, for " the bees were found to 6c", read it was found that thi
bees wen .
Page 160, line 18, for " data " read date.
Page 167, line 14, for " e.g." read i.e.
Page 168, line 6, for " sprat/ dust " read spray and dust and in line 33, for
" arsenical and " read arsenicals and.
Page 173, heading table No. 34, for " 1920" read 1929.
Page 175, last line, for " 1 928-1931 " rend 1928 and 1929.
Page 176, line 29, for "orchard" read orchard being available.
Page 188, line 39, for " .0008" read .00008.
Page 190, under Darlington, C. D., and Moffatt, A. A., delete 1926 citation.
APPLE POLLINATION STUDIES IN THE
ANNAPOLIS VALLEY
BY W. H. BRITTAIN
POPULAR SUMMARY
GENERAL
The investigations described in the following pages grew out of a request
of the Department of Agriculture of Nova Scotia and of various horticultural
organizations, that a study be undertaken to determine whether the alleged
destruction of pollinating insects by poison dusts and sprays was adversely affect-
ing the set of fruit in commercial apple orchards.
As a result of the initial survey, the work quickly broadened out into a
study of the entire pollination problem. As indicated in the evidence presented,
it was found that the hive bees of the Annapolis valley had indeed suffered
great losses as a result of prevailing spraying and dusting practices. However,
it was found that wild solitary bees were sufficiently abundant in most orchards
during the period of the investigation, alone to effect pollination under favour-
able conditions. The results secured emphasized that the proper interplanting
of cross-fruitful varieties was a crucial factor in the production of commercial
crops.
THE PROCESS OF POLLINATION AND FERTILIZATION IN APPLES
The apple blossom is provided with five sepals, which persist at the " blos-
som end " of the apple, five petals, which are soon shed, twenty to twenty-five
stamens, each with an anther containing pollen surmounting the filament and
surrounding the five stigmas, which unite in a common style that leads to the
ovary, these parts constituting the pistil of the flower. The stamens and pistil
are the essential organs of the flower representing, respectively, the male and
female parts.
The ovary is divided into five compartments each containing two egg cells,
or four in the case of Northern Spy. As the anthers discharge their pollen shortly
before the stigmas are receptive, this renders it difficult for pollen from a flower
to reach the stigmas of the same flower. There may be, however, a considerable
number of blossoms on the tree that receive pollen from their own or neighbour-
ing flowers.
The mere transfer of the pollen from anther to stigma constitutes pollination
and is usually effected by the aid of insects. The transfer of pollen from the
anther of one flower to the stigma of another of the same variety is known
as self-pollination. The transfer to the stigma of the flower of another variety
is cross-pollination. Following pollination with the pollen of a suitable variety,
the pollen tube develops, grows down the style through the tissue and finally
reaches the ovary, where, upon penetration, the sperm is discharged into the
embryo sac, where it unites with the egg cell, thus accomplishing fertilization,
this process usually resulting in the formation of seed. This initiates the growth
and development of the fruit and is requisite to setting. Where the ovules fail
of fertilization, or where, for any reason development is checked the blossoms
are soon shed.
It is not, of course, necessary for the entire complement of seeds to be pro-
duced in order for normal apples to develop, but the larger the number of seeds
that do develop in a fruit the better chance is there for that fruit to succeed in
the competition for nutrients and to remain on the tree until the harvest. Apples
with one or more compartments devoid of seed are likely to be one sided or
otherwise abnormal. While it is true that a certain amount of fruit may develop
without seed in some varieties, especially in Gravenstein, this has little commer-
cial significance as the percentage so produced is small.
From the standpoint of their requirements for pollination apples may be
either (1) self -fruitful or (2) self -unfruitful, i.e., they are capable of producing
mature fruit when pollinated with their own pollen or (2) they require the
pollen from another variety in order to produce fruit. We shall see later that
few, if any, varieties are completely self-unfruitful, and hence the expression
" partially self-fruitful " largely loses its meaning. In fact, self-fruitfulness varies
from varieties that yield little or no fruit when self-pollinated to others that
produce a set little short of that obtained from favourable cross-pollinations.
When the pollen from one variety results in fruit production when placed
on the stigma of another variety, the first variety is said to be cross-fruitful
with the second variety. Just as few apple varieties are completely self-unfruit-
ful, so there are few cases in which the pollen from one variety is completely
useless for another variety, though there are many combinations that give very
poor results commercially. Therefore, the expressions " commercially self- or
cross-fruitful " would be more accurate.
THE PROBLEM OF POLLINATION
In order for apple orchards to be pollinated there must be present in the
orchard (1) a suitable pollen supply in the form of varieties capable of pro-
ducing fruit when the pollen is carried to the stigmas of other varieties present
and (2) an adequate supply of insect pollinators in the form of either hive or
wild bees, to ensure that cross-pollination occurs. This is because all varieties
of apples produce better crops when cross-pollinated by another suitable variety
and some of them ordinarily set very little when self-pollinated. The admix-
ture of varieties is important, because some varieties yield pollen which, when
appli d to the stigmas of certain others, results in low yields, sometimes even less
than when the same variety is self-pollinated. All varieties require the work of
insect pollinators, even the most self-fruitful, since wind is a negligible factor
in the pollination of the apple.
The problem of apple pollination is rendered much less acute than it might
otherwise be by the fact that only a small amount of pollination is necessary. If
one out of twenty of the original blossoms develops into fruit a commercial crop
will result, provided there is a good bloom, whereas, in the cherry, for example, a
much larger set is required. Again, self- and cross-unfruitfulness are much less
pronounced in the apple than in the cherry. It may also be noted that since the
cherry has but a single seed, if that seed fails to be fertilized the fruit drops.
Whereas, in the apple with its complement of ten or twenty seeds, the fertilization
of but a small proportion is necessary for setting and even seniles apples may
be produced by some varieties.
In one variety studied, viz., the Baldwin, selfing may resull in a commercial
crop, though not as high a yield as is produced from the most fruitful crosses. In
view of these facts, it is only to be expected that less difficulty would be experi-
enced in ensuring cross-pollination of apple varieties than would occur in the
cherry, where pronounced self-unfruitfulness and cross-unfruitfulness may occur.
On the other hand, cases of over-pollination, resulting in biennial bearing, appear
to occur in some varieties. Nevertheless it should be emphasized that, with the
possible exception of Baldwin all varieties must be regarded as commercially
self-unfruitful and that all, including Baldwin, benefit from cross-pollination. A
definite problem results when (1) large blocks of highly self-unfruitful varieties
are planted together or (2) when cross-unfruitful varieties are mixed or (3)
when insect pollinators are insufficient in number. The question of the inter-
fruitfulness of varieties should be given consideration in connection with all
grafting-out operations and also when new plantings of commercially desirable
sorts are to be made.
To elaborate further upon this point it may be said that with respect to
the two fundamentals for successful pollination, viz., (1) pollen supply and
(2) insect pollinators, the following conditions may exist in commercial orchards:
1. There may be a suitable intermixture of inter-fruitful varieties and an
adequate population of insect pollinators.
2. Cross-unfruitful varieties may be inter-planted, though insect pollinators
are sufficiently abundant.
3. Varieties may be planted together in too large blocks to permit of effect-
ive cross-pollination, even though an abundance of insect pollinators may be
present.
4. A similar condition to number 3, but without a sufficient number of insect
pollinators.
5. Similar to number 1, but with an inadequate number of insect pollinators.
To simulate under experimental control, the foregoing conditions, trees of
the Gravenstein, King, Baldwin, and Spy varieties were covered with tents and
the following treatments given: —
1. Supplied with " bouquets," i.e., blossoming limbs of the desired variety
placed iri tubs of water, of an effective pollinizer and a hive of bees.
2. Supplied with " bouquets " of an ineffective pollinizer and a hive of
bees.
3. Not supplied with " bouquets " of any kind but with a hive of bees.
4. Not supplied with " bouquets " of any kind nor with a hive of bees.
5. Supplied with " bouquets " of an effective pollinizer but no bees.
6. Un-tented trees left to open pollination for comparison.
TABLE No. 1.— RESULTS OF TENT EXPERIMENTS, 1929-1932
Variety
Effective
pollinizer
and bees
Ineffec-
tive
pollinizer
and bees
No
pollinizer
and bees
(selfed)
No
pollinizer
and
no bees
Effective
pollinizer
but
no bees
Open
polli-
nation
Gravenstein
King
Baldwin
Spy
10-90
5-42
8-17
10 05
1-14
3-58
4-96
2-70
2-12
3-32
7-77
200
0-67
103
3-49
0-85
0-47
1-81
5-05*
1-20
9-91
4-74
10-40
8-83
*Abnormally high per cent set in 1932 due to small number of blossoms on tree, has raised the general
average for this treatment.
The results indicated in the accompanying table summarizing four years
work, justify the following conclusions: —
1. Insect pollinators are required by all varieties, wind pollination alone
giving unsatisfactory results.
2. All varieties give best results when crossed with an effective pollinizer.
3. Only the Baldwin yields a commercial crop when self-pollinated and
even the Baldwin gives better results when crossed with an effective pollinizer.
STUDIES IN INTER-FRUITFULNESS OF APPLE VARIETIES
During the past four years very many extensive crosses and self-pollina-
tions have been made with standard varieties grown in Nova Scotia and much
information with respect to the value of varieties from the standpoint of self-
fruitfulness and of cross-fruitfulness have been obtained. It is not necessary
8
to detail the results of these experiments, but rather to point out the practical
significance to the grower of the results secured.
A point of prime importance brought out in these studies was that from
the standpoint of their value as pollen parents, i.e., as pollinizers for other
varieties, apple varieties may be sharply divided into two groups, namely, (1)
good pollen varieties and (2) poor pollen varieties. The former may be usually
depended upon to work well as pollinizers with other varieties that blossom at
the same time. The latter ordinarily have little value as pollen parents, some
of them producing in the variety pollinated even less fruit than when the variety
on which this pollen is used is self-pollinated. Poor pollen producers may
themselves be highly fruitful, when pollinated by one of the group of good pollen
producers. The poor pollen producers are known not only by the small quan-
tity of pollen produced of low germinability and inferior value for crossing
purposes, but by their relatively low seed content as compared with good pollen
producers. This point is of the utmost importance to the grower who has a
pollination problem in his orchard or who desires to make new plantings. The
practical results of our studies can best be appreciated by a study of the follow-
ing table in which some of the common varieties are listed as good or poor
apple producers. By consulting the blossoming chart in connection therewith,
also the chart showing the inter-fruitfulness of some standard varieties and a
third chart showing the results of hand-pollination experiments, together with
the accompanying table of good and poor pollen producers, the grower can
decide which varieties " go well " together and avoid those combinations that
are sure to give inferior results. In providing pollinizers for varieties that have
given poor results due to lack of pollination, it is preferable to choose a variety
that blossoms a little later rather than a little earlier, because, in the first case,
the pollen of the pollinizing variety will be liberated before that of the other
is shed, thus facilitating cross-pollination. The blossoming chart shows only
average blooming periods, but, in some seasons, there is much less overlapping
than others, and the more long drawn out the bloom the greater likelihood of a
pollination problem arising, unless adequate provision has been made.
TABLE No. 2.— CLASSIFICATION OF APPLE VARIETIES
Poor pollen producers
( rood pollen producers
Baldwin
Alexander
Blenheim
Ben Davis
Bramley Seedling
Hough Sweet
Gravenstein
( Portland
King
( Ox Orange
Mann
Crimson Beauty
Nonpareil (Roxbury Russet)
Duchess
Ribston
Dudley
Rhode Island Greening
Delicious
Stark
Fameuse
Gano
( rolden Russel
(J rimes G olden
Jonathan
Mcintosh
Rome Beauty
Tolman Sweet
Wagener
Wealthy
Wellington
Winter Banana
Wolf River
Yellow Bellflower
Yellow Transparent
York Imperial
FIELD STUDIES IN INSECT POLLINATORS
As already clearly shown in the foregoing experiments, apple pollination
is effected by insects, and it is usually claimed that the hive bee is the main
agent in apple pollination. Unfortunately, our studies show that as a result of
widespread poisoning from the use of poisoned sprays and dusts, the hive bee
has ceased to be a factor in apple pollination in the Annapolis valley of Nova
Scotia. The danger of poisoning hive bees may be reduced, though not entirely
eliminated, by refraining from spraying and dusting during the blossoming
period and by moving the bees into the orchard only when the early apples
have come into bloom and removing them before the after-blossom sprays are
applied. Dusting is usually more fatal than spraying, but severe losses may
follow either practice when poisons are applied to apple bloom, or to the blossoms
of other plants growing in or near the orchard.
Careful investigations have shown that pollination at present is mainly
effected by various small, solitary bees that nest in the ground in the neighbour-
hood of orchards, especially along roadsides, pastures, dykes and similar situa-
tions. They have been reasonably plentiful in at least most orchards during the
years 1928 to 1931 inclusive. In 1932, there was an apparent general decrease
and this, combined with unfavourable weather for bee activity during the
blossoming period, had a noticeable effect on fruit setting. Bumble bees, while
sometimes abundant locally, were of minor importance in most orchards during
the course of our studies.
While, therefore, under favourable conditions, solitary bees may alone be
able to satisfactorily pollinate the apple crop, conditions may arise when it is
desirable to supplement their efforts. This can only be done by supplying hive
bees for the purpose.
It should be emphasized, however, that a few colonies of bees placed in an
orchard surrounded by large acreages devoid of bees is of little or no value. In
such situations it may be necessary to have a concentration of from 35 to 50
colonies in order to ensure the pollination of the particular orchard in which
the bees are placed. In districts where beekeeping is general, however, and
neighbouring orchards are similarly supplied, one colony to the acre or even
one colony to four acres may be sufficient. Owing to the many factors involved
more exact figures cannot be given. It must suffice to point out that the pro-
vision of as many colonies as practicable is a useful measure of insurance against
unfavourable weather, and a scarcity of wild pollinators, since it is only the hive
bees that can be increased in numbers at will and placed where needed in the
orchards. Unfortunately, at the present time, there is no adequate local supply;
inexperience in beekeeping and the danger of poisoning prevents many from
adopting this practice who would otherwise do so.
ARRANGEMENT OF POLLINIZERS
In orchard planning, the mixture of self-unfruitful varieties should be
avoided, and this includes practically all varieties, save Baldwin. A great deal
of trouble is experienced with Blenheims planted in solid blocks. Not all Blen-
heims even in mixed orchards are fruitful, but more of them are, whereas we
do not know of large unmixed blocks bearing regular crops. The same may
be said of Starks. Large blocks of a single variety are uncommon in Nova
Scotia and this has greatly reduced the trouble due to lack of pollination, but
lack of bearing due to too many trees in a block has been noted, not only in
the foregoing varieties, but also, though less commonly, in certain other varie-
ties, including Golden Russet, Spy and Gravenstein.
Bad combinations of cross-unfruitful sorts are unfortunately more common
and are especially to be avoided. Thus a combination of Blenheim and Baldwin
is bad, because though the Baldwin may give fair crops in its bearing years,
10
though probably less than in a block by itself, the Blenheim is entirely without
a suitable supply of pollen, and, being very self-unfruitful, is likely to give very
inferior results. Stark and Baldwin or Stark and Blenheim is another bad
combination and, worse still, a combination of all three. With King the pollen
variety seems to make less difference than with most others. This variety
typically producing a low percentage of fruit, no matter what pollen parent
is used, nevertheless is commercially fruitful because of its heavy blossoming
habit, large size and annual bearing habit. However, even King responds by
increased yields to an effective pollinizer, but is itself of little use as a pollen
parent. Therefore, where King occurs in planting, a suitable pollinizer must
be provided and the same may be said of Gravenstein and other poor pollen
producers.
Furthermore, it must be borne in mind that, when supplying a pollinizer
for a variety that itself is a poor pollen producer, a third variety must be used
that is cross-fruitful with the first pollinizer.
The accompanying plans showing method of setting out a four-variety
block and for grafting-out a solid block of one variety will be suggestive of
many similar combinations that may be used.
OTHER CAUSES OF UNFRUITFULNESS
It should be emphasized that lack of pollination is but one of the causes
of unfruitfulness ; lack of adequate attention to fertilizer requirements and
damage caused by insect or fungous pests being of most importance. Further-
more, vigorous fruit-spurs are more likely to set fruit with less pollination than
weak spurs. Pollination alone, therefore, cannot ensure regular cropping, which
can only be effected by attention to all the necessary details of good orchard
practice.
APPLE POLLINATION STUDIES IN THE
ANNAPOLIS VALLEY
FOREWORD
The investigations described in the following pages were undertaken as a
result of resolutions received by the Honourable the Minister of Agriculture,
from the Canadian Horticultural Council, the Nova Scotia Fruit Growers' Asso-
ciation and other organizations, requesting that an investigation be undertaken
into the whole pollination problem in Nova Scotia and whether the alleged
destruction of pollinating insects as a result of poison dusts had adversely
influenced the setting of fruit during the past few years. Upon receipt of these
resolutions a committee was appointed by the Deputy Minister to consider and
report upon the advisability of initiating such an investigation. This committee
was as follows:
Arthur Gibson, Dominion Entomologist (Chairman)
W. T. Macoun, Dominion Horticulturist
C. B. Gooderham, Dominion Apiarist (Secretary)
H. G. Crawford, Chief, Division of Field Crop and Garden Insects, Ento-
mological Branch
F. A. Herman, Division of Chemistry, Central Experimental Farm
H. Groh, Division of Botany, Central Experimental Farm
As a result of the deliberations of this committee a report was prepared for
the Deputy Minister approving the carrying out of the proposed investigation,
but recognizing that factors affecting the set of fruit other than insects,
would have to be taken into consideration in the course of such studies, they
expressed the opinion that such an investigation could not be completed in less
time than five years and drew up a tentative scheme for the conduct of the
experiments. They further recommended that Dr. W. H. Brittain, Professor of
Entomology, Macdonald College, be asked to take over the general supervision
of the experiments, working in co-operation with the officials of the Dominion
Department of Agriculture, whose work had a direct bearing on the problem
involved. It was understood that the problem would not come under any one
Branch, but that the officer in charge would attempt to co-ordinate the work of
the different agencies concerned. The Department of Agriculture for Nova
Scotia took an active interest in planning the work, and the Deputy Minister,
Col. R. Innes, placed an assistant and office facilities at the disposal of the com-
mittee.
The foregoing plan having received the approval of the Deputy Minister
and the sanction of the Minister, was proceeded with and an effort made to devote
as much attention as possible to the significant factors involved in apple pollina-
tion. The study falls naturally into two parts: first, a study of the inter-fruit-
fulness of some of the chief commercial varieties grown in Nova Scotia and,
second, a study of the insects involved in the pollinizing process. While the study
dealt primarily with local varieties and problems an attempt was made to pay
particular attention to a study of factors and principles applicable to all work
of this sort.
11
12
Considerations of space have forbidden the publication of a great deal of
data secured during the course of these investigations, some of which have an
important bearing on the work. For this reason much tabular matter, weather
records, results of analyses and other matter has had to be excluded, while
detailed accounts of other phases of the work will be published in separate
papers.
The five-year period has proved sufficient to elucidate most of the problems
dealing with the inter-fruitfulness of the apple varieties studied, and to throw
some light upon the general problem of apple pollination. A number of points
of considerable theoretical importance, as indicated in the following pages, still
awaits attention. It is to be regretted that lack of time, the necessity of develop-
ing a suitable technique, want of suitable equipment, poisoning of our experi-
mental apiaries and other causes have not permitted us to bring the entomological
phases of the investigation to the same degree of completeness. Consequently
many of the conclusions must be regarded as tentative.
ACKNOWLEDGMENTS
Grateful acknowledgment is due from the officer in charge of these investiga-
tions to colleagues and assistants who have helped him in securing the data
contained herein. The names of several appear as joint authors of sections of
this report, while the assistance of others is acknowledged elsewhere.
Mr. F. A. Herman was associated in the poisoning investigations; Mr. C. B.
Gooderham in the utilization of hive bees in orchards; Mr. Don Blair in studies
of inter-fruitfulness of apple varieties; Mr. J. M. Cameron in studies of the
activities of hive and wild bees and Mr. C. A. At wood in studies of the biology
and classification of insect pollinators.
At the outset of the investigation it was necessary to proceed with impro-
vised methods and a temporary staff and through the course of the work this
occasioned many difficulties. Nevertheless, the smoothness with which the work
proceeded after the first year, speaks very well indeed for the industry and
initiative of the various workers. It would be difficult to imagine a temporary
organization working together more smoothly in carrying out the work for
which each was responsible in connection with this complicated problem.
In addition to those who have been solely or jointly responsible for definite
parts of the investigation, it would be impossible to mention by name all those
whose efforts have been placed freely at our disposal in the course of these
studies. Dr. W. S. Blair, Superintendent of the Experimental Station, Kentville,
took a keen personal interest in the work and without his continuous assistance
an important phase of our studies could never have been carried out. His efforts
were ably seconded in many ways by those of his assistant, Mr. C. C. Eidt.
Special thanks are also due to Mr. F. H. Johnson for invaluable assistance during
four years of the investigation; to Mr. R. D. L. Bligh for direction of pollination
crew during 1928; to Mr. Evan Craig and Mr. H. G. Payne for essential advice
and assistance in connection with apicultural problems; to Messrs. Robert Long-
ley, John Leefe, and Robert Ward, who assisted at various times in connection
with certain phases of the problem. Mr. A. Hill gave invaluable assistance and
advice in the initial vear of the investigations. Various members of the staff
of Acadia University, 'including Dr. H. G. Perry, Dr. H. W. Harkness, Dr. D. V.
hnl, assisted with equipment or advice, while Dr. Muriel V. Roscoe carried out
essential cytological studies in connection with the chromosome count oi apple
varieties. Permission to use unpublished data secured in these studies was
kindly furnished by Dr. Roscoe. Mr. J. F. Hockey of the Dominion Laboratory
of Plant Pathology extended co-operation in the form of the use of equipment,
laboratory space and personal assistance. Mr. M. B. Davis, the Dominion De-
partment of Agriculture, and Dr. C. L. Huskins, oi McGill University, read and
13
criticized parts of the report. In the studies to determine sources of bee poison-
ing the assistance of Mr. H. Groh was invaluable. Mr. J. Patterson assisted us
with the loan of the solar radiation apparatus used in our experiments and Dr.
W. J. Rowles of Macdonald College designed and prepared the photoelectric bee
counter. Mr. W. E. Whitehead is responsible for most of the illustrations used
in the report. To all members of the Committee, especially those who actively
assisted in the investigation, the officer in charge extends his sincere thanks.
I. INTRODUCTION
W. H. BRITTAIN
A. THE APPLE INDUSTRY IN NOVA SCOTIA
1. GEOGRAPHICAL POSITION
The province of Nova Scotia consists of a peninsula projecting into the
Atlantic ocean, together with the island of Cape Breton. It lies in a north-
easterly and southwesterly direction and is nearly 400 miles in length. The
forty-fifth parallel of north latitude divides the province into two nearly equal
parts. The " fruit belt " lies in the western part, mostly south of this parallel,
Fig. 1. — Map of Nova Scotia showing fruit belt (original).
in what is generally called the " Annapolis valley," though this district really
comprises the valleys of several streams emptying into the bay of Fundy, includ-
ing the Annapolis, Cornwallis, Gaspereaux and Avon rivers. A range of hills
500 to 700 feet in height called the North Mountain, protects the Valley from
the north and northeast winds and forms the northern boundary of the Valley,
14
15
while a corresponding range of hills, called the South Mountain, shuts it in on
the south. The extreme eastern and western limits are marked by the towns
of Annapolis Royal on the west and Windsor on the east. Of course there are
apples grown outside of this area, but, in the main, fruit growing on a large
commercial scale is largely confined to this territory. Here we have concen-
trated in a valley about 100 miles long and varying in width from five to ten
miles, an acreage in apple trees of approximately 38,000 acres.
2. CLIMATE
Fraser (1924), in discussing the situation of important apple growing regions
of North America, states as follows: —
" The variation between the day and night temperatures in New Jersey,
Delaware and the eastern part of Maryland and Virginia is about the same
as that along the shores of lake Ontario. In both instances we find fruit
regions of the highest rank. The Annapolis valley in Nova Scotia, alongside
the bay of Fundy, the eastern shore of lake Michigan and the Pacific coast
states are all fruit regions because of their climate."
Writing regarding general climatic conditions of Nova Scotia, W. A.
Middleton, Provincial Horticulturist, states: —
" Extreme heat or cold is not experienced in the commercial apple area of
the province. The summer temperature occasionally rises to about 90 degrees,
while that of the winter seldom falls below zero. The average summer tem-
perature is 62 degrees, that of the winter about 25 degrees, and the mean annual
temperature about 43 degrees. The annual rainfall ranges from 40 to 45 inches
and is generally well spread over each month of the year."
Further details regarding climate are given elsewhere.
The soil varies from a light sandy loam to clay loam. Along the North
Mountain range and at the east and west ends of the Valley the heavier soils
predominate, while elsewhere lighter soils are more in evidence, some of the
lightest soils being in the centre of the Valley.
3. VARIETIES GROWN
Comeau (23) gives the following partial list of apple varieties grown in
the Valley :-
"Alexander (Emperor)
Ailing ton Pippin
Arabka
Arkansas Beauty-
Baldwin
Baxter
Ben Davis
Bethel
Bietigheimer
Bismark
Blenheim Orange Pippin
Bottle Greening
Borkins
Bough Sweet
Bramley Seedling
Calkin Pippin
Canada Baldwin
Canada Red
Chenango Strawberry
Clayton
Clyde Beauty
Charles Ross
Colvert
Cooper's Market
Cornish Aromatic
Cortland
Cox Orange
Cranberry Pippin
Crimson Beauty
Duchess
Dudle}'
Danvers Sweet
Delicious
Early Harvest
Esopus Spitzenburg
Fall Pippin
Fallawater
Fameuse (Snow)
Gano
Gilliflower
Gideon
Gloria Mundi
Golden Pippin
Golden Russet (American)
Golden Russet (English)
Golden Sweet
Gravenstein
Grimes Golden
Haas (Fall Queen)
Honey Sweet (Winter Sweet
Paradise)
Hubbardston
Hublon
Hunt Russet
Hurlbut
Ingram
Jacob Sweet
Jenneting
Jersey Sweet
Jewett Red
Jonathan
Jones
Kent Pippin
Keswick Codlin
Kitchener
King
Lady Finger
Lady Sweet
Late Strawberry
Longfield
Longworth
Louise (Princess Louise)
16
3. VARIETIES GROWN— Concluded
Mcintosh
McMahon
Maiden Blush
Mann
Mother
Xewtown Pippin (X.Y.
Pippin)
Nonpareil (Roxbury Russet)
Northern Spy
North West Greening
Ohio Pippin
Ontario
Orange (of New Jersey)
Patten Greening
Pewaukee
Peck Pleasant
Pennock
Pine Apple
Porter Pippin
Pound Sweet
Pumpkin Sweet
Red Streak
Red Sweet Pippin (Moore
Sweet)
Red Russet
R.I. Greening
Ribston Pippin
Rolfe
Rome Beauty
Rose Red
Salome
Scarlet Pippin
Scott Winter
Seek-no-further (Westfield)
Shackleford
Shiawassee
Smokehouse
Stark
Sutton Beauty
Swaar
Swazie
Sweet Greening
Thompson
Tolman Sweet
Twenty Ounce (Cayuga Red
Streak)
Twenty Ounce Pippin
Vandevere (Newton Spitz-
enburg)
Victoria
Wagener
Wealthy
Wellington
Western Beauty
White Apple
White Craft
Winesap
Williams' Favorite
Wilson's Red June
Winter Banana
Winter Bough
Winter Pippin
Wolf River
Yellow Bellflower
(Bishop Pippin)
York Imperial"
" Of these varieties, the following, arranged approximately in the order of
ripening, are of commercial importance in the fruit district of Nova Scotia:
Wolf River R. I. Greening
Mcintosh Baldwin
Blenheim Stark
Ribston Northern Spy
King Fallawater
Bishop Pippin Golden Russet
Wagener Nonpareil
Cox Orange Ben Davis "
Wellington
Crimson Beauty
Yellow Transparent
Red Astrachan
Duchess of Oldenburg
Williams' Favorite
Wealthy
Gravenstein
Dudley
Alexander
" The following varieties are important in the export trade of the province
Gravenstein Cox Orange Northern Spy
Blenheim Wellington Fallawater
Ribston R. I. Greening Golden Russet
King Baldwin Nonpareil
Wagener Stark Ben Davis "
"The ten best commercial varieties for export are as follows:
Golden Russel
Nonpareil "'
for commercial plantings are as
Spy (Red)
Baldwin
but mainly for local demand-.
Gravenstein Wagener
Blenheim R. I. Greening
Ribston Baldwin
King Northern Spy
The officially recommended varieties
follows :
Gravenstein (Crimson) Golden Russet
Cox Orange King (Red)
Mcintosh is favoured by some authorities,
The standard varieties that are recommended to be retained, but not recom-
mended for future planting are as follows:
Ribston Pippin Nonpareil Wolf River
Blenheim Orange Wellington Gano
Stark Wealthy Ben Davis
Greening Bramley Seedling
Of the foregoing Wagener is favoured as a filler owing to the small >'\ze of
the tree and the fact that it is a short lived tree. It has an additional advantage
in being an effective pollinizer for the early varieties
17
4. QUANTITY GROWN
The following tabulation taken from official sources indicates the growth
of the apple industry for the past half century:
Barrels
1880-85 — Annual Average 30,320
1885-90— " " . . . 83,356
1890-95— " " 118,556
1895-1900— " " 261,879
1900-05— " " 377,225
1905-10— " " 496.655
1910-15— " " 786,633
1915-20— " " 932,957
1920-28— " " 1,056,057
1929— " " 2,134,100
1930— " " 1,172,443
1931— " " 1,611,273
In this connection a tabulation of the actual produced crop of the different
varieties grown in the Valley is of interest: —
PERCENTAGE CROP OF VARIETIES OF APPLES OF THE TOTAL CROP PRODUCED
IN NOVA SCOTIA (FIGURES BY UNITED FRUIT CO.)
Gravenstein 13
Baldwin 13
Stark 10
Ben Davis 10
Odd varieties 9
Ribston 8
King 6.5
Northern Spy 6
Nonpareil (Roxbury Russet) 5
Blenheim 5
Golden Russet 5
Fallawater •.. .. 2.5
Wagener 2
Gano 1.6
Greening 1.5
Wolf River 0.8
Wealthy 0.7
Bishop Pippin (Yellow Bellflower) 0.4
100.0
On examination of these figures, it is apparent that approximately 25 per
cent of the crop is Gravenstein, Ribston and King; 25 per cent Blenheim,
Northern Spy, Nonpareil, Golden Russet, Fallawater and Wagener; 35 per cent
Baldwin, Ben Davis, Gano and Stark, and 15 per cent other sorts. This shows
that 85 per cent of the crop is made up of what we consider 13 standard sorts.
From the foregoing data it is seen that a very large number of varieties
are grown in Nova Scotia. One of the chief problems of the fruit industry is
to reduce the number of unprofitable varieties, but it is only within recent years
that the movement to cut down the number of varieties planted and to graft
out the non-commercial and unprofitable sorts has gained headway. In connec-
tion with this movement it is of interest to note that 85 per cent of the crop is
made up of what may be considered standard varieties.
5. AVERAGE YIELDS
It has been estimated that in the period 1900-1905 the average yield of
apples in Nova Scotia was 16 barrels per acre; in the period 1910-1915 it was
24^ barrels per acre, while the average annual yield in the years 1920-1926
was 30 barrels per acre. Included in these figures there is, of course, a large
acreage of small, non-commercial orchards, though, even with all allowances, the
average crop must be regarded as small. The figures for a number of typical
orchards from central Kings county, which is the most typical orchard section,
60796—2
18
including both poorly cared for and well cared for orchards, indicate that in
really commercial orchards the crop is much more satisfactory.
An examination of the figures shows that, in the period under study, the
yield per acre varied from 26 to 172 barrels, while the average for all these
orchards was considerably higher than the average yield for the province, viz.,
66-6 barrels. Average yields of from 80 to 100 barrels per acre are considered
necessary for profitable fruit growing and several orchardists have attained
this figure, but the number that fall below this amount materially lowers the
average figures.
B. FACTORS OTHER THAN POLLINATION AFFECTING
FRUIT PRODUCTION
1. GENERAL
Since this report is concerned with the problem of pollination, it is not
necessary to deal exhaustively with other factors involved in the setting or
production of apples. Nevertheless, a brief discussion of certain of the more
important factors involved in this process, may enable us better to appreciate
the relative importance of the pollination factor and the phenomena associated
therewith, and the better to evaluate the results of the pollination studies
described herein.
It is well known to all students of the subject that the production of
profitable crops of marketable fruit is the end result of a long series of factors.
Pollination is but a link, though a very important link, in the chain. Some of
these factors are at least partially under the control of the grower; many are
not. The proper procedure for every fruit-grower should be to keep all condi-
tions as favourable as possible for the production of large crops of quality fruit,
so that, through neglect to attend to a single factor, he may not lose not only his
crop, but also the money spent in attempting to produce it. The proper atten-
tion to all factors within his power to control may enable him to reduce or
minimize the losses resulting from unfavourable conditions not directly con-
trollable.
In order to secure dependable data with regard to all measurable and
relevant factors we have tabulated the weather records for the growing season
over a period of years and have attempted to analyze these data from the stand-
point of the possible effect upon fruit setting and fruit production. An intensive
study of 16 representative orchards situated in central Kings county has also
been made over a three-year period in an attempt to determine, if possible, the
effect of various cultural practices. In addition, the crop returns of 34 growers
for a period of six years were compiled and studied in connection with their
expenditure for spray material, fertilizer, etc.. as obtained from the records of
a local fruit company. Furthermore, an economic survey of approximately one
hundred orchards in the same district was made. In this survey special atten-
tion was again given to the question of fertilizer and spraying practices, as these
factors lent themselves well to statistical treatment and gave indication of being
of considerable importance in connection with the quantity of apples produced.
These surveys were carried out by Mr. Robert Longley of the Provincial staff
and only the more outstanding and general conclusions are referred to in this
report. The results obtained are in general agreement with the more prolonged
studies conducted by the Economics Branch of the Dominion Department of
Agriculture and reported by Coke (1931).
19
2. CLIMATIC FACTORS
The most important factor, or rather complex of factors not under the
control of man is that conveniently summarized under the heading of " climate ".
The effect of certain climatic factors is easy to observe, but, in the main, these
factors are difficult to measure and hard to evaluate.
The effect of climate can best be discussed with reference to (1) its direct
effect upon the blossoms, or (2) its indirect effect upon the insect pollinators.
Of these the second is probably more important, but since this problem is dis-
cussed at great length elsewhere, it is merely referred to at this point.
(a) WEATHER CONDITIONS DURING BLOOM
Careful records of weather during the blossoming period have been kept
for a number of years, but it is difficult to establish significant correlations
between such conditions and the set of fruit, probably because conditions at
a certain critical period such as the period of stigma receptivity may be the
crucial factor and our methods have not achieved a sufficient degree of refine-
ment to demonstrate this. However, certain facts are sufficiently clear to
deserve mention.
Frost during the bloom may result in the destruction of the stigmatic
surfaces of the pistil followed by the subsequent drop of the blossoms. Such
frosts are of comparatively rare occurrence in most parts of the Valley. Since
the inception of this investigation, no such losses have occurred in a series of
orchards in which observations have been made, except in one case in 1932
in an orchard known to be in a " frost belt ". Such conditions do occasion-
ally occur, particularly in certain sections in the centre of the Valley. It has
been pointed out (Murneek, 1930) that frosty weather at bloom, even where
it does not kill, may prevent the growth of the pollen tube.
Hedrick (1908) contends that a temperature slightly above the average is
usually most favourable for fruit setting. On the other hand, a very high tem-
perature, especially if accompanied by wind, may bring about the drying up of
the stigmas, so that they remain receptive for but a short time. It was note-
worthy that in the season of 1930 the blossoming period was coincident with
a very high temperature and a short period of stigma receptivity was noted by
all workers, whereas, during the cooler, more humid season of 1931, the period of
stigma receptivity was longer. Knowlton (1929) states that, " it is an estab-
lished horticultural fact that a larger set of fruit occurs on selfed varieties in
seasons when the temperatures are most favourable for pollen tube growth."
When we study the wide range of self-fruitfulness that may occur in the same
variety from year to year, we are forced to believe that this must be the case.
This was particularly noticeable in Blenheim in the favourable blooming period
of 1931. We had become accustomed to regard this variety as almost com-
pletely self-unfruitful, but in 1932 selfing produced a fruit set of up to five per
cent.
Excessive humidity and driving rains during bloom appear to have an
adverse effect upon the pollen, which may be washed away or deteriorate while
still on the anthers, or they may even wash off pollen already deposited on the
stigma. Low yields from certain varieties have been observed to follow periods
of rainy weather during the blossoming periods of such varieties. The occur-
rence of high winds during bloom, often mentioned as a factor detrimental to
fruit setting, has been a negligible factor during the course of these studies in
four out of the five years, but in 1932 it appeared to be of importance in certain
sections.
The fact that it may not be necessary for more than one blossom in twenty
to develop into a marketable apple in order to secure a commercial crop, gives
60796— 2 J
20
a considerable margin of safety in apple growing, since, even though a large
proportion of blossoms may be destroyed, the set may be sufficiently large, and,
in many cases, larger than necessary for a commercial crop. This fact is brought
out by the records of fruit setting for four standard varieties in sixteen orchards
for the years 1928-1930 inclusive, taken together with the weather records for
the same period.
TABLE No. 1.— RECORD OF PER CENT FRUIT OBTAINED IN SIXTEEN KINGS COUNTY
ORCHARDS, 1928-1930
Variety
1928
1929
1930
Average
Gravenstein
3-98
510
6-90
7-08
5-64
4-49
11-32
9-13
7 05
7-79
10-20
10-65
5-86
King
5-68
9-92
Spy
10-12
5-76
7-64
8-92
7-64
Note. — "Per cent fruit" refers to the percentage of blossoms that produced fruit which remained
after the "July drop". Figures based on counts of approximately 1,000 blossoms of each variety each
year.
The figures would seem to indicate that in these orchards during the period
studied the average set obtained was at least reasonably satisfactory. Unfor-
tunately, this period does not include a season similar to 1932. when conditions
for pollination were very unfavourable owing to the very broken weather. It
would be expected that under such conditions failure to set through lack of a
proper distribution of pollinizing varieties and an inadequate force of insect
pollinators would be accentuated.
(6) WEATHER CONDITIONS AT OTHER PERIODvS
Winter injury to trees of the ordinary commercial varieties is not common
in the fruit belt of Nova Scotia, but freezing weather that occurs after the buds
have started in the spring but before the blossoms open, may act directly on
the blossoms, destroying the essential parts of the flower. Indirect injury result-
ing in a reduced crop may be caused by frost injury to the developing leaves.
Such injury results in a dwarfing and curling of the leaf, which is inclined to be
brittle and, not infrequently, the lower epidermis separates from the overlying
cells. Such a condition was quite widespread in 1928 and occurred locally in
1932. It should be noted that the destruction of even a considerable proportion
of blossom buds by frost, does not necessarily reduce the final crop, since suffi-
cient may set from the uninjured buds to produce a commercial yield. The injury
to the primary leaves is sometimes more serious and sometimes appears to result
in an abnormal drop.
The climate of the Annapolis valley is ordinarily characterized by an ade-
quate supply of moisture throughout the growing season, and protracted droughts
resulting in dwarfing and even drop of leaves and fruit are comparatively rare.
They are, however, not entirely unknown, as, for example, in the seasons of 1921
and 1928, where orchards on dry land suffered badly, in some cases, and again
in 1930, when a dry period of about eight weeks during the autumn months
resulted in considerable dwarfing of the fruit.
Prolonged periods of rainy weather have rarely been mentioned as a cause
of crop reduction. It would appear, however, on the basis of data secured during
these investigations that the effect of excessive rainfall during the growing season
had a detrimental effect on crop production, whereas the greater the sunlight
during the months May to July inclusive, the more favourable the condition for
fruit production. An extended discussion of this problem, however, is beyond
the scope of this paper.
21
All the preceding discussion has had to do with the effect of weather con-
ditions on the crop of the corresponding year. That the climatic complex also
has an effect upon the crop of subsequent seasons is equally true, though the
relative importance of the different factors is hard to evaluate. The fact that,
in certain seasons, apple trees everywhere, even wild or uncared-for trees, bloom
heavily, as in 1929 and in 1931, is indicative of the effect of little understood
climatic factors in fruit-bud formation and vigour.
Significant weather records are presented in table 2, together with crop
ngures for the corresponding years.
TABLE No. 2.— WEATHER CONDITIONS FOR GROWING SEASON
Per cent
May-July (inclusive) and April-October (inclusive)
possible
Year
Barrels
bloom
Mean
Total
Total
Mean
Total
Total
(esti-
tem-
ram
sunlight
tem-
rain
sunlight
mated)
perature
(ins.)
(hrs.)
perature
(ins.)
(hrs.)
1915
613,882
9
55-73
12-05
593-5
54-5
23-09
1,271-9
1916
631,470
60
55-79
6-67
611-9
54-6
28-04
1,403-5
1917
774,730
80
56-65
8-90
513-2
53-0
27-35
1,230-4
1918
827,693
45
59-11
7-85
667-0
54-8
21-94
1,434-6
1919
1 , 600, 000
90
58-17
6-44
688-8
54-4
16-09
1,357-8
1920
1,167,000
65
56-20
6-00
792-1
54-73
17-03
1,528-1
1921
2,000,000
85
58-17
5-34
700-4
55-92
13-98
1,511-3
1922
1,800,000
80
57-82
9-14
599-4
56-14
21-37
1,255-5
1923
2,021,177
90
55-64
7-26
625-6
53-30
20-92
1,350-4
1924
1,976,340
85
59-07
5-55
762-6
54-80
18-55
1,492-7
1925
1,447,401
75
58-88
10-77
652-7
53-53
22-88
1,378-7
1926
1,033,021
65
55-17
9-73
668-9
52-18
19-93
1,420-4
1927
1,086,932
85
56-67
10-37
665-3
54-24
30-11
1,405-7
1928
1,244,987
45
58-70
7-44
631-2
55-50
18-33
1,310-3
1929
2,134,100
95
59-34
9-26
775-5
55-57
19-89
1,459-0
1930
1,172,443
65
61-66
6-33
658-1
56 05
13-58
1,509-6
1931
1,611,273
95
59-75
7-73
620-3
56-23
21-64
1,321-5
1932
60
1
3. NUTRITIONAL FACTORS
The question of the nutritional factors that affect fruiting is too technical
for extended treatment in a paper dealing with pollination and is neither
necessary nor desirable. Nevertheless, it is evident that the set of fruit may
be influenced jointly by pollination and a number of these other factors.
Trees lacking in vigour are incapable of setting large crops whether pollinated
or not, and it is not surprising that many workers have stressed tree vigour,
and, more especially, fruit-spur vigour, as a factor in fruit setting. This factor
is important because vigorous spurs can better supply an abundance of water
and organic nutrients to the developing fruit. MacDaniels and Heinicke (1929)
present evidence to show that there may be greater need for cross-pollina-
tion, which is usually a requisite for seed formation, when the trees have produced
a large proportion of weak spurs, or when they are growing under conditions
which otherwise limit the sap and nutrient supply to flowers and young fruits.
The maintenance of a high level of nutrition may partially compensate for
imperfect pollination or for irregularities in chromosome behaviour at megasporo-
genesis as Howlett (1932) contends.
Lattimer (1931) noted in pollination experiments conducted by him, that,
in less vigorous trees there is a greater difference in relative effectiveness
between the better pollinizers. On more vigorous trees there was little difference
between the several good pollinizers used. The conclusion is drawn that when
low-vigour trees are to be pollinated one should choose only an effective pollin-
izer. The different results obtained on various trees and between different limbs
of the same tree have been brought out repeatedly in our tests.
22
Sandsten (1909) has recorded that the condition of the tree may have an
important bearing on the quality of the pollen, it being inferior from orchards in
poor cultural condition. Tree and fruit-spur vigour is the result of proper
nutrition and this has to do with cultural practices and the maintenance of a
suitable supply of moisture and nutrients. The importance of an adequate
supply of nitrogen and the question of maintaining a correct proportion between
the nitrogen and carbohydrates in the plant, is a matter to which much attention
has been given during the past few years. The varying results obtained from
tests with the same pollen on different limbs and even on different spurs
emphasize the importance of the factor of vigour.
Anything that upsets this balance in the tree has a tendency to reduce fruit
setting, though judicious pruning may increase it. Excessive applications of
nitrogenous fertilizer, if ever given, appear to be rare. Our surveys indicate that
applications of from 500 to 600 pounds per acre not only tend to increase setting,
but are commercially profitable. The coefficient of correlation existing between
the applications of commercial nitrogenous fertilizer, mainly in the form of
nitrate of soda, and crop produced was -4844 ± -0527 for the orchards used
in our economic survey. It is believed that this correlation would have been
much higher, if allowance could have been made for the effect of previous crops.
All data secured tend to emphasize the value of an adequate supply of readily
available nitrogen. Our figures indicated no value as far as crop was concerned
for nitrogen applied in the form of barnyard manure, though the presence of an
adequate supply of organic matter in the soil is undoubtedly beneficial and
should by no means be neglected in actual orchard practice. Otherwise, the
beneficial effect of commercial nitrogenous fertilizer may not be experienced.
Regarding the value of other types of fertilizers we do not have sufficient infor-
mation from our own studies, though the advantage of using a balanced fertilizer
has been insisted upon by certain investigators. That low phosphorus may be
an important limiting factor has been demonstrated in other tests.
Our survey indicates that good crops are possible both under conditions
of sod mulch or clean culture, if properly carried out, and any system of treat-
ment that results in a strong growth of spurs and provides for an accumulation
of stored food materials in the spur, is considered to favour fruit setting. Best
crops are secured where the trees produce a good growth of leaves, terminal
growth and trunk.
4. PATHOLOGICAL FACTORS
Under this heading we consider the injuries caused by insects and fungous
pests. These may influence the crop indirectly by injuring the leaves, resulting
in dwarfing or even drop of fruit, or they directly injure the blossoms or the
fruit itself. The apple scab organism (Venturia inaequalis (Cook) Winter), is
one of the most important orchard pests. Not only do heavy infestations result
in leaf-injury, causing, in seven1 cases, dwarfing and partial defoliation, but
early infection causes drop of blossoms or young fruit by its development upon
the flower stalks.
Of the insects responsible for reducing fruit setting the green apple bug
(Lygus communis Knight), is of most interest from our standpoint, because,
owing to its small size, it is often overlooked and its injury attributed to other
causes, including lack of pollination. The bud-moth (Tmctoccra occllana
iSchiff.), also deserves special mention. Many other pests might be mentioned
in this connection, but those already indicated are sufficient for purposes of
illustration.
A study of the yield records from sprayed and unsprayed orchards over a
long period of years, shows a decided advantage in yield as well as in quality
of fruit, in favour of the sprayed orchards. The result of our economic survey
23
showed a significant correlation between spray costs and yield, there being an
upward trend of crops as the amount of spray materials used was increased.
Confirmation of these results is obtained from a similar survey carried out by
the Agricultural Economics Branch of the Department of Agriculture (Coke,
1931), in which it is likewise shown that crops and financial returns per acre
increase with the amount expended upon pest control.
Against the beneficial effects of spraying and dusting must be set the injury
that occasionally results from the use of certain spray schedules, but an examina-
tion of our figures proves that even those materials reputed to be most danger-
ous, show, over a period of years, a significant increase in crop over untreated
trees.
The indirect effect of poison applications to bloom upon insect pollinators is
discussed at length elsewhere, but the effect of the not uncommon practice of
applying a fungicide dust during bloom, especially in seasons when the blossom-
ing period has been prolonged, may be conveniently referred to at this point. The
apparent injurious effect upon stigmas and anthers of applications of various
fungicidal and insecticidal preparations has long been noted. In 1930 an applica-
tion of sulphur dust to Golden Russet in our experiments reduced the original
set by about 10 per cent but did not lower the final fruit yield. Since apple
trees do not bloom evenly, only a certain proportion of blossoms are in a con-
dition to be injured at any one time. Therefore, the destruction of a certain pro-
portion of blossoms may even be beneficial in imparting greater vigour to those
that remain, as shown by MacDaniels and Furr (1931) in the case of sulphur
dust. If, on the other hand, the application is made early, before many blos-
soms are pollinated, or before the pollen tube has penetrated the style sufficiently
to be beyond the effect of the sulphur, an injurious effect upon set may result
on certain varieties. Also with varieties that tend to produce only one or two
fruits to the spur such as King, the result may be more serious than on varieties
that tend to set in clusters, as Wagener, Baldwin, etc.
II. POLLINATION AND FRUITFULNESS IN APPLES
W. H. BRITTAIN
A. THE PROCESS OF POLLINATION AND FERTILIZATION
(Definitions)
Since there has been some lack of uniformity in the nomenclature used in
connection with pollination work the following definitions of terms, as employed
throughout this paper, are given:
Pollination. — The mere transfer of the pollen from anther to stigma con-
stitutes pollination and is usually effected by the aid of insects. The transfer of
pollen from the anther of one flower of one variety to the stigma of another of
the same variety is known as self-pollination. The transfer from the anther of
one flower of one variety to the stigma of another is cross-pollination.
Pollinizer. — The male parent, that is, the plant that furnishes the pollen.
Pollinator. — The agent for distribution of the pollen.
As all investigators have shown, the chief agents in the transfer of pollen
from one flower to the other, are insects. A certain amount of apple pollen is, it
is true, carried by wind, as will be discussed at greater length elsewhere, but wind
pollination as far as the apple is concerned, is negligible. In the absence of the
hive bee over wide areas of our fruit belt, this role is performed largely by wild
bees, mostly of the genera Halictus and Andrena, though certain species of flies
and certain other insects play a minor part.
Fertilization. — Following pollination with the pollen of a suitable variety,
the pollen tube develops, grows down the style through the tissue and finally
reaches the ovary, where, upon penetration of the ovule, the sperm is discharged
into the embryo sac, where it unites with the egg cell, thus accomplishing fer-
tilization, this process usually resulting in the formation of seed. This initiates
growth and development of the fruit and is requisite to setting. Where the ovules
fail of fertilization, or where, for any reason development is checked the blossoms
are usually shed.
Fruitful. — A plant which produces mature fruit is said to be fruitful. As
ordinarily used it means sufficient to produce a commercial crop.
Self -fruitful and Self -unfruitful. — From the standpoint of their requirement-
for pollination apples may be either (1) self -fruitful or (2) self -unfruitful, i.e.
(1) they are capable of producing mature fruit when pollinated with their own
pollen or (2) they require the pollen from another variety in order to produce
fruit. We shall see later that few, if any, varieties are completely self-unfruitful,
and hence the expression " partially self-fruitful " largely loses its meaning. In
fact, self-unfruitfulness is rarely completely, expressed in the apple, as pointed
out by Crane and Lawrence, varying from varieties that yield little or no fruit
when self-pollinated to others that produce a set little short of that obtained
from favourable cross-pollination.
Cross-fruitful and Cross-unfruitful. — When the pollen from one variety
results in fruit production when placed on the stigma of another variety, the
first variety is said to be cross-fruitful with the second variety. On the' other
24
25
hand, if fruit does not result the condition is known as cross-unfruitful. Just as
few apple varieties are completely self-unfruitful, so there will be few cases in
which thp pollen from one variety is completely useless for another variety,
though there are many combinations that give very poor results commercially.
Therefore, the expressions " commercially self- or cross-fruitful " would be more
accurate.
Sterility. — The condition in which there is failure to set fruit with viable
seed.
Self-sterile and Self-fertile. — The terms self-sterile and self-fertile, often
used synonymously with self-unfruitful and self-fruitful respectively, are more
properly applied to the ability or inability of the plant to produce fruit with
viable seeds when self-pollinated. Since fruits may be obtained which produce
no viable seeds in the case of certain apple varieties, such a variety may be
self-fruitful and, at the same time self-sterile, at least theoretically. The pro-
duction of viable seedlings is, of course, an all-important factor in breeding work,
but is not of direct interest in connection with pollination experiments, except in
so far as the production of viable seeds is to be correlated with the value of cer-
tain varieties as pollinizers for other varieties.
B. THE POLLINATION PROBLEM
It will be clear from the foregoing that the pollination problem in commer-
cial orchards consists (1) in planting together varieties that are inter-fruitful,
i.e., in which each variety has another blooming at the same time that can be
depended upon to pollinate it, or (2) in " working over " a sufficient number
of trees in blocks of self-unfruitful or cross-unfruitful varieties to secure adequate
pollination, or (3) in supplying insect pollinators where they are not present in
adequate numbers.
It has been shown that, in Nova Scotia, a great many varieties are grown
and most of the older orchards are planted to a large number of varieties. While
this has been a very serious drawback from a commercial standpoint, it has
resulted in the pollination problem being less serious than in many other districts,
where the exclusive growth of a few commercially desirable sorts has been the
rule. In many of these orchards, for practically all varieties there are present
others with which they are cross-fruitful. In other cases, the mixture of
varieties, from the standpoint of pollination, has been unsuitable and has
undoubtedly resulted in subnormal crops, especially in years in which conditions
for cross-pollination were unfavourable. Such subnormal crops over a long
period of years may well result in a large aggregate loss to the grower. In a
few cases large blocks of self-unfruitful varieties have been set out. A good
example is Blenheim, which is one of the most self-unfruitful of locally grown
apple varieties. Owing to its resistance to apple scab, numbers of growers set
out blocks of this variety, with the result of poor and infrequent crops. Con-
siderable difficulty has also been experienced with Stark, Ben Davis and, to
a lesser extent, certain other varieties. With the recent movement to restrict
new planting to a few of the more profitable varieties and to graft out unprofit-
able ones, comes the need for closer attention to the question of pollination.
One object of these studies is to determine the inter-fruitfulness of the varieties
that are now recommended for planting in the Annapolis valley. Two other
varieties, viz., Blenheim and Stark, frequently reported as unfruitful, have also
been given special attention. Furthermore, it has been considered desirable to
make a thorough study of insect pollinators, to determine whether the natural
supply is sufficient or whether means should be taken to increase their number.
In this connection a study of poisoning among hive bees as a result of orchard
spraying and dusting practices has been made.
26
C. CAUSES OF UNFRUITFULNESS
According to Crane and Lawrence (1929 & 1930), unfruitfulness in apples is
associated with (1) generational sterility, i.e., the failure of any of the processes
concerned in the normal alternation of generations, viz., development of pollen,
embryo sac, embryo, endosperm and the relation of these with one another,
regardless of the cross made; (2) morphological sterility due to the suppression
or abortion of the sex organs; (3) incompatibility , which is found in cases where
both ovules and pollen are functional, the failure to set fruit being due to the
fact that the pollen tube becomes arrested in the stylar tissue, whereas, in a
compatible cross, with the same pollen and ovules taking part, the pollen tube
travels the full length of the style, the male and female nuclei fuse and the
fertilized ovule develops into a fruit. The term incompatibility has been often
misused in horticultural literature, being applied to various forms of unfruitful-
ness in addition to that indicated; (4) parthenocarpy or the development of
fruit without seed; (5) number of seeds per ovary.
Without embarking upon a complete discussion of the genetic constitution
of apple varieties, it may serve to clarify future discussion to refer briefly to
certain facts in connection therewith. We owe to several workers our present
knowledge of chromosome behaviour in the apple (vide Kobel 1 1930, 1930a, &
1931), Rybin (1926), Nebel (1930), Darlington and Moffet (1930), Moffet
(1931), Roscoe (unpublished data)). Darlington and Moffet (loc. cit.) show that
the basic chromosome number in the Pomoideae is 17 and that diploid, triploid
and tetraploid forms occur. These writers find, however, that the chromosome
constitution of apples is complex. Thus so-called diploids with 2n=34 are, in
reality, secondary polyploids being hexasomic in respect to three chromosomes
and tetrasomic in respect to four chromosomes. Triploids are partly hexasomic
and partly nonasomic. Varieties with intermediate numbers are found, the
highest frequency in triploid x diploid seedlings being 41. Among the com-
mercial apples classified as diploids may be listed Cox Orange, Ben Davis, Spy.
Mcintosh, Duchess, Red Astrachan, Rome Beauty and Bishop Pippin; while
Gravenstein, King, Baldwin, Blenheim and R. I. Greening are triploids, as indi-
cated in the accompanying list. Consideration of the foregoing facts will shed
considerable light on the results outlined in the following page-.
TABLE No. 3.— CHROMOSOME NUMBERS OF APPLE VARIETIES
Variety
Rybin
Kobel
Nebel
Darlington
and
Moffet t
•M.V.
Roscoe
Aderslebener Calville
6\
Allington Pippin.. . .
34
34
Annie Elizabeth
Apfel aus Lunow
34
51
51
Arkansas
Baldwin
48-49
51
34
Beauty of Bath
Belle de Boskoop
46
51
34
51
Ben Davis
Blenheim Orange . .
51
Bobnapfel. .
46-49
51
Calville Grand Duke of Asden
34
Carlisle Pippin
34
Charlamowsky (Duchess of Oldenburg).
34
34
Cox Orange Pippin
34
Crimson Beauty
34
Crimson Bramley .
51
Damason Reinette
45-47
Deacon Jones
34
Der Boehmer
34
Delicious
34
27
TABLE No. 3— CHROMOSOME NUMBERS OF APPLE VARIETIES— Concluded
Variety
Rybin
Kobel
Nebel
Darlington
and
Moffett
*M.V.
Roscoe
Dolgo
34
Doucin (Mailing Type II)
34
34
Earlv Victoria
Eden
34
34
34
34
Geheimrat Dr. Oldenburg
General von Hammerstein
Genet Movie
51
Golden Russet
34
46-46
51
51
34
34
Horbert's Reinette
45
Irish Peach
34
49-51
34
34
Kentish
34
34
Keswick Codlin
Kola
68
34
34
Lane's Prince Albert
34
Lord Derby
34
42
Mcintosh
34
34
Manx Codlin
34
Manks Kiichenapfel
34
34
34
Medina
Minister von Hammerstein
34
Nonpareil (Roxbury Russet)
*51
Nonsuch (Mailing Type VI)
34
34
34
34
Northern Spy
Odlins
Old English Broadleaf. . .
Ontario
34
Paradise (Mailing Stock Type I)
34
34
34
Red Siberian Crab....
Red Winter Reinette
34
Reinette du Canada
51
38-40
51
Reinette Zucoamaglio.
34
51
34
Ribston Pippin .
42
51
R.I. Greening
51
34
Roter Eiserapfel
47
Roter Jumpfernapfel. .
34
51
34
34
Sommerrambour
48-49
Stark
*51
Tompkins King
51
34
34
Twenty Ounce
Wagener
*34
Warner's King
42
Waidners Goldrenette
34
41 + 1
34
34
Winter Magetin .
34
48-49
Worcester Pearmain .
34
Wolf River
34
Yellow Bellflower
34
34
*Unpublished data, used by permission.
28
1. GENERATIONAL STERILITY
In the first group of factors mentioned by Crane and Lawrence {loc. cit.)
as a cause of unfruitfulness, pollen sterility, or the production of a large
percentage of pollen of low germinability with a high percentage of aborted or
shrivelled grains, is very common. Among the varieties that, in our tests, proved
to have relatively poor pollen, were Blenheim, Baldwin, Gravenstein and King.
It will be noted that all these varieties are triploids, which indicates that triploid
varieties should not be depended upon as male parents, as all have given
generally inferior results over a period of years. On the other hand, varieties
that give relatively large amounts of pollen of good quality, such as Cox Orange,
Northern Spy, etc., are diploids. The correlation that exists between pollen
viability and chromosome constitution noted by Kobel (1926) is very evident in
our tests and strongly supports the view that low pollen germination may be
considered as an indication of triploidy. The low pollen germination alone does
not account for the low value of triploids as pollinizers. Irregular chromosome
behaviour, followed by abortion in the embryos is also a factor. It may be
noted that ovule abortion resulting in a low average seed count is another
characteristic of triploid varieties.
2. MORPHOLOGICAL STERILITY
Detjen (1926) finds that fruits whose ovules have not been fertilized are
generally shed soon after the blooming period, but that the last wave of
abscission, i.e., the " July drop " is due mainly to factors which cause embryo
abortion. In studies of the Stayman Winesap, Howlett (1931) has shown that
an important factor in fruit setting is irregularity in chromosome behaviour
during megasporogenesis which would cause early dropping. It would appear
that most cases of so-called incompatibility are, in reality, cases of embryo
abortion due to irregular chromosome distribution.
3. INCOMPATIBILITY
As stated by Crane and Lawrence (1930), among cultivated apples, sterility
and incompatibility differ in several respects from the same phenomena in
plums and cherries. A salient difference is that incompatibility is rarely, if ever,
completely expressed in apples. These workers are writing from a breeding
standpoint and with special reference to the production of viable seed, but this
fact also applies, to a certain degree, to fruit fulness. A high degree of self-
incompatibility has been claimed for many varieties, including Gravenstein, Spy,
Cox Orange and Blenheim. With such varieties, even when the pollen is removed
from the anthers and matured under ideal conditions, it practically never
produces a satisfactory set of fruit in self-pollination tests. At the other extreme
is Baldwin, which, though producing pollen of low value for crossing purposes,
may yield satisfactory crops when selfed, though not as large crops as when
pollinated with pollen from a diploid variety.
Cross-incompatibility has also been claimed for various combinations of
apple varieties, though some workers question this. Howlett (1927) in experi-
ments in Ohio, found no evidence of cross-incompatibility and considered
apparent oases of this phenomenon to be examples of " cross-sterility, inter-
sexualism, due to impotence of pollen." Einset (1930) tested a number of eases
of alleged cross-incompatibility. Only in the case of Arkansas and Grimes was
there indication of true cross-incompatibility in the sense employed by East and
Manglesdorf (1925), and Crane and Lawrence (1929). The remainder of their
tests showed not incompatibility but sterility, which they consider to be due
to the effects of zygotic abortion caused by irregularities in the reduction
division in the generative cells.
29
4. PARTHENOCARPY
Several varieties of apples have been reported as showing a tendency to set
fruit with few or no seeds. Gravenstein is the most important of our local
varieties to ©how this tendency. Ribston Pippin, not studied by us, is another.
Among other reported varieties are Antonovka, Alexander, Crimson Bramley
and Longfield. Kobel (1930 & 1931) noted the tendency of varieties with
low pollen germination and irregular chromosome distribution to set few or no
seeds. He designates as " false parthenocarpy," those cases in which fertiliza-
tion has actually taken place, but, owing to the irregular chromosome distribu-
tion, seed development does not take place. Even in Gravenstein, which shows
the greatest tendency to produce seedless or few seeded fruit, there is strong
evidence that seed formation is a decided advantage in fruit setting, and Einset
(1930) has even found a correlation between seed content and weight, though
such a correlation was not obtained by us.
Extensive counts from various standard varieties always reveal a higher
average seed count in apples that remain on the tree than in those that come off
in the July drop. Individual fruits may vary, but the foregoing was true for
averages. Numerous workers have held that such production is so intimately
associated with the physiological processes of the fruit, that apples with
developed seeds have an advantage in the competition for water and organic
nutrients over those that have fewer or no seeds and this is confirmed by our
results. It is, however, true that triploid varieties are able to set fruit with a
lower content of developed seed than in the case in diploids. Data with respect
to the relation between fruitfulness and the production of seeds and seedlings
are presented later.
In connection with the production of seedlings resulting from various crosses,
the difference between diploids and triploids is very pronounced, the latter, as a
group, giving a very low percentage of seedlings. The number of seeds and
seedlings resulting from different crosses on any given female parent should
therefore, be a useful index of the value of the male parent as a pollinizer for
that variety. But within the triploid group those crosses that give the larger
number of seed are more fruitful than those that yield a smaller number, though
the average number of seed for the group is much less than in diploids. Data
bearing on this point are presented in another section.
D. PERCENTAGE OF FRUIT TO FLOWERS REQUIRED TO GIVE
AN ECONOMIC YIELD
This problem is discussed only from the standpoint of commercial orchards
in the Annapolis valley. As previously noted the per cent of blossoms, which,
in the apple, is required to develop into mature fruit is small compared with
stone fruits. The percentage that actually sets fruit varies with different factors
already discussed, according to the amount of bloom present on the tree, and
with the variety. With a small bloom, as many as fifteen, twenty or even
a higher percentage may be obtained; but, with a full bloom, five per cent is
the figure ordinarily given as representing a satisfactory commercial set. This
is a convenient, though arbitrary figure, since, of course, varieties differ in
regard to the number of apples necessary to produce a crop that can be called
commercial. A number of workers (vide MacDaniels, 1930) stress the advis-
ability of taking into consideration the number of fruiting centres. Howlett
(1929), for example, finds that in Stayman Winesap one apple to every third
flowering spur is sufficient for a commercial crop. Lattimer (1931) contends
that more attention should be given to expressing fruit-set on the basis of
spurs rather than individual flowers, pointing out that if more than one fruit
per spur sets it should be thinned. The foregoing is undoubtedly true and,
under orchard conditions, it is often advisable to thin a tree that is bearing
less than a normal crop, because of clustering on a portion of the spurs.
30
Nevertheless, where natural pollination occurs there is no way of avoiding
uneven setting.
Some varieties are poor female parents, i.e., they shed a higher proportion
of blossom and fruit than others, having a tendency to thin down to one fruit
to the spur; others have a tendency to set in clusters. The fruiting habits
of a number of standard varieties are shown in the accompanying table, in
which the year 1929 is taken as the basis for comparison with the three-year
average for 1928-1930 inclusive. In this year all trees blossomed heavily and
the set was unusually good.
TABLE No. 4.— BLOSSOMING AND FRUITING HABITS OF FOUR STANDARD VARIETIES
(Average of 16 Orchards)
Variety
Per cent
fruit
(1929)
Crop per
tree 1929
(bbls.)
Average
crop
in bbls.
(1928-30)
Average
number
apples per
tree
(1929)
Average Calcu-
number lated.
apples per number
bbl. blossoms
(1929) per tree
(1929)
Gravenstein
King
Baldwin
Spy
5-68
4-49
11-32
9-13
2-67
4-10
3-73
4-11
3 00
3-02
501
4-26
1,291
1,640
2,051
2,053
430
543
681
482
22,720
36,525
18,122
22,508
From these figures it will be seen that though the King trees included
in this survey have a larger average number of blossoms than the other varieties,
the percentage of fruit is lower. Nevertheless, since the King apples are large.
the final number of barrels produced is short only of the Spies. In the case
of Baldwin, which has a decided tendency to set in clusters, the percentage set
is heaviest, but, since the number of blossoms per tree is the smallest and the
fruit size is also the smallest, the total crop in barrels is less than that of
King or Spy. The heavier set obtained with this variety may be a factor in
its biennial bearing habit in so many orchards.
Comparing the foregoing figures with the average result of hand pollina-
tions carried out for the three-year period 1928-1930, we find that Baldwin
has given an average per cent fruit of 11-07; Cox Orange, 7-64; Golden Russet.
4-40; Gravenstein, 6-16; King, 4-0; Spy, 7-63. The massed results showing
average figures for the four varieties from 16 commercial orchards may be of
some interest in this connection and are given for comparison.
TABLE No. 5.— FRUITING HABITS OF FOUR STANDARD VARIETIES,
FOUR FOR 1928-1930
AVERAGE OF
Orchard
Total
blooming
spurs
counted
Average
per cctn
with
bloom
Average
blossoms
per
blooming
spur
Average
per cent
fruit
A
3, 54(5
2,870
3,439
2,031
3,089
2.094
3.096
2,861
2,619
2.S5I
2,541
2,558
3.344
3,252
3,009
3,329
55-50
44-25
44-74
34-51
44-69
62 03
42-97
54-13
47-32
60-69
73 16
59-39
55-81
54-68
.-,1-ss
49-4S
508
5 07
5 17
5-39
4-90
4-83
4 ■ 75
4-63
4-91
4-70
4-85
502
4-64
4-89
4 70
4-56
11-44
B
9-79
c
6-23
CA
7-26
D
2 07
E
F
S01
6-64
G
6-46
H
I ; ....
731
5-76
K
6-49
L
10-59
M
8-74
N
7-19
O
B- 17
P
III. EXPERIMENTAL STUDIES IN APPLE
POLLINATION
W. H. BRITTAIN and DONALD S. BLAIR
A. CONDITIONS FOR CROSS-POLLINATION
In considering the pollination question for commercial orchards two
questions must be kept in mind, viz., (1) the necessity of an abundant supply
of effective pollinizers for each variety planted in the orchard and (2) the
presence of an adequate force of pollinating insects to insure that cross-pollina-
tion is effected.
The conditions that may be found within a commercial planting are as
follows: —
1. The orchard may be planted with a suitable mixture of cross-fruitful
varieties.
2. The orchard may be set out with cross-unfruitful varieties, e.g., Graven-
stein, Blenheim and Stark planted together.
3. Varieties may be planted together in such a way that one variety is
not supplied with an effective pollinizer, e.g., Cox Orange planted with Blen-
heim. In this case Cox Orange is a suitable pollinizer for Blenheim, but the
Blenheim (an ineffective pollinizer) is incapable of cross-pollinating the self-
unfruitful Cox Orange.
4. Self-unfruitful varieties may be planted in such large blocks that
cross-pollination is impossible.
5. For any one of the above conditions an effective population of pollinators
may be lacking, which would be a limiting factor in each case.
B. PREVIOUS WORK WITH BEES AS POLLINATORS UNDER
CONTROLLED CONDITIONS
Several workers have tested the value of bees in experiments in which
hives are introduced beneath tents covering the trees. In some of these cases the
necessity for cross-pollination is apparently ignored as no source of compatible
pollen was supplied, resulting in selfing and a low set of fruit, as might be
expected. Morris (1921) found no advantage from having Jonathan and Rome
Beauty trees selfed by bees. Macoun (1923) found that Mcintosh set a satis-
factory crop when supplied with bees and a source of compatible pollen or
when wild bees were allowed access to the flowers under the same conditions,
but a very low yield was obtained when all bees were excluded. Hutson (1926)
tented two trees each of Wealthy and Jonathan, one each with bees and one
without. The Wealthy gave a set of 17 per cent with bees and 4-02 per cent
without; the Jonathan gave 8-4 per cent with bees and -80 without. Many
workers have noted that caged trees or bagged limbs from which bees are
excluded yield little or no fruit and much similar information is available from
experiments in inter-fruitfulness of varieties carried out under tents, to which
reference is made elsewhere.
31
32
C. EXPERIMENTS IN BEES AND POLLINATION
(Tent Studies)
1. OUTLINE OF EXPERIMENTS
In order to determine the effect of the different treatments outlined under
the heading " Conditions for Cross-pollination," there was initiated in 1929 a
series of experiments in which bearing trees of four standard varieties were
enclosed in tents and subjected to conditions in simulation of those referred to in
the foregoing. The trees then were seventeen years old, in excellent condition
and grown under similar conditions of culture. All these experiments were
carried on at the Experimental Station orchard at Kentville.
The following were the treatments accorded to the trees in the different
tents :
(a) Supplied with pollinizing bouquets of an effective pollinizer and with
a colony of bees, thus furnishing the tree both with a proper pollen supply and
with insect pollinators.
(6) Supplied with pollinizing bouquets of an ineffective pollinizer arid with
a colony of bees, thus furnishing the tree with adequate provision for cross-
pollination, but with a supply of unsuitable pollen.
(c) Supplied with a colony of bees, but with no pollinizing bouquets of any
kind, thus ensuring that the tree would be self-pollinated by the bees.
(d) Supplied with neither bees nor bouquets of any kind, thus preventing
pollination except such self-pollination as would occur through the agency of
wind or gravity.
(e) Supplied with bouquets of an effective pollinizer but with no bees.
This test was started in 1930. This tree, therefore, while having a supply of
suitable pollen provided, was deprived of the normal agency of cross-pollination,
except in so far as wind may be effective in this regard. In 1931 and 1932 a
current of air from an orchard duster was blown very thoroughly through the
bouquets and over the trees. It was only in 1932 that there was any evidence
that any appreciable pollination was achieved by this method. This is
accounted for by improvement in technique in the latter year. About half an
hour was taken at each tree and the air current directed through the bouquet
in all directions. It is highly improbable, however, that ordinary wind could
produce the same effect as a current of air produced in the foregoing manner.
(/) The results from the foregoing trees were compared with records from
neighbouring untented trees grown under similar conditions. Since the orchard
was well laid out from the standpoint of the intermixture of cross-fruitful
varieties and, since colonies of bees were placed throughout the orchard, this
series was provided both with an adequate supply of suitable pollen and with
insect pollinators sufficient to ensure cross-pollination. In 1931, owing to a
certain amount of poisoning among the bees and probably other factors, the
bee population was lower than in other seasons.
As a further check on the foregoing experiments three limbs of as nearly
as possible uniform size and condition were selected in each tent and treated
as follows:
1. On trees with bees and bouquets, (i.e. on trees (a) and (b)):
(i) Enclosed one limb with a cheesecloth bag and allowed it to remain
untouched.
(ii) Bagged one limb and selj '-pollinated the blossoms.
(iii) Bagged one limb and pollinated blossoms, with the same variety of
pollen used in the bouquets — an effective pollinizer in (a) treatment
and an ineffective pollinizer in (b) treatment.
33
60796—3
34
2. On trees with no bouquets {i.e. (c) and (d) and trees with no bees
(i.e. (e) ) and on the untented tree {i.e. (/) ) :
(i) Bagged one limb and left it untouched.
(ii) Bagged one limb and self -pollinated blossoms.
(iii) Bagged one limb and pollinated the blossoms ivith pollen from a cross-
fruitful variety.
Thus, in each case we have for comparison individual hand pollinated or
untouched limbs to check against the results from pollination with bees, or
with blossoms unpollinated except by wind.
The varieties chosen for these tests were Gravenstein, King, Baldwin,
and Spy, a range covering the blossoming season. Included are two varieties
which may be numbered among the most self-unfruitful of commercial sorts,
viz., Gravenstein and Spy. The former is a triploid form having a tendency
to produce a certain number of seedless or few-seeded fruits, especially under
some conditions. Intermediate in position is the King, which, in some seasons,
has appeared as self-unfruitful as any variety, but in others has given a fair
set when selfed, though never as large a set as when crossed with a cross-fruitful
variety. Baldwin is a striking exception in that it is uniformly self-fruitful
to a larger extent than any variety tested. This variety, though a triploid
form, with pollen of low germinability and possessing a high proportion
of aborted grains, very inferior for crossing, is yet highly self-compatible.
Gravenstein, though varying considerably from year to year is markedly
inferior for crossing purposes to such varieties as Cox Orange, Wagener, Golden
Russet, etc., which, with Northern Spy, are among the most effective pollinizers
among commercial sorts grown in the Annapolis valley.
For pollinizing bouquets, limbs of the desired varieties well covered with
bloom were removed and placed in large cans of water. The first year, only a
single bouquet was used per tent, but it was found that the set on the side
next the bouquet was much greater than that on the opposite side. Therefore, in
following years two bouquets, one on each side of the tree, were employed. In
the very hot blossoming season of 1930 there was a decided tendency to wilt
on the part of the bouquets, which made them less attractive to the bees and
had an adverse effect on setting. This was avoided in 1931 by frequent chang-
ing of the bouquets whenever it became necessary.
For ineffective pollinizers Blenheim was generally used for Gravenstein
and King. For Baldwin and Spy, Nonpareil was employed. As effective pol-
linizers we used Wagener for Gravenstein, Wagener or Golden Russet for King,
Cox Orange for Baldwin and the same variety or Ben Davis for Spy.
Package colonies of bees were used as pollinators and in 1928-1931 proved
quite satisfactory. In 1932 overwintered colonies were used.
The results of tent experiments have been discounted by certain workers
on account of the supposedly " unnatural conditions " but we were unable to
secure any evidence to indicate that our results were affected by artificial con-
ditions inside the tent. Hygrograph and thermograph charts herein presented
show a remarkably slight variation between inside and outside condition-.
2. GENERAL RESULTS OF TENT EXPERIMENTS
The accompanying table summarizes the results obtained from this Beries.
These results bring out clearly the necessity of proper attention being given
to the right admixture of varieties in orchard plantings and equally the impor-
tance of the presence of pollinating insects in order to obtain a commercial
crop.
All varieties respond by increased sets of fruit to the application of the
pollen by cross-fruitful varieties to their stigmas and all bnt Baldwin give
35
decidedly inferior results when selfed. This is less true of King than the other
varieties tested, which, from the standpoint of per cent fruit obtained, may be
considered a poor female parent, and shows less difference than other varieties
between effective and ineffective male parents. The abundant bloom of this
variety, coupled with the large size of the fruit and its annual bearing habits
compensates, in a measure, for the low percentage fruit obtained with all
crosses, so that King may be regarded as a commercially fruitful variety.
■=*TtT
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r "
June 9, 1932 (original)
we record® inside and outside tents, Kentville, N.S. (1)
24- June 6, ; (2) May 24- June 3, 1931; (3) May 28- June 9, 1932; (4) May 28-
The average seed per fruit for each treatment in tent series was taken
in 1932. This figure proved to be a very reliable index as to fruitfulness. For
each variety tested, either diploid or triploid, the seed content per apple
increased proportionally to the pollination provided, i.e., the more perfect the
conditions for pollination the greater the number of seeds per fruit. The 1932
tented figures are in agreement with those obtained in the standard varieties,
during the period 1928-1932.
In order to avoid repetition a discussion of the detailed results of these
experiments is included in the next section.
60796— 3 1
36
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37
D. STUDIES IN THE INTER-FRUITFULNESS OF STANDARD
VARIETIES
1. OBJECT OF EXPERIMENTS
The fact has been brought out in the preceding experiments that all varieties
benefit by cross-pollination. Furthermore, it is clear that it is not sufficient
merely to plant together varieties that blossom at the same time, since some
varieties give poor results when used to pollinate others. Some that are good
pollinizers for other varieties are themselves highly self-unfruitful and some,
that yield good results when pollinated with pollen from a suitable variety, are
themselves deficient as pollinizers. A study of the results obtained in hand-
pollination tests gives useful information as to the inter-fruitfulness of the
varieties tested and also makes clear certain general principles applicable to all
work of this kind.
The varieties chosen for these standard tests were as follows: —
Gravenstein Baldwin i
King Cox Orange i
Golden Russet Northern Spy
Certain other varieties were used as pollinizers as opportunity offered.
Mcintosh might well have been added to the list, but so much information is
available regarding this variety from other sources that it was not considered
necessary. Special tests with the varieties Blenheim and Stark are described in
another section.
2. TECHNIQUE OF PROCEDURE AND DEFINITIONS OF TERMS USED
Vigorous trees of the same age and growing under similar cultural conditions
at the Experimental Station, Kentville, were selected. In a few cases, where
the desired variety did not happen to be available through lack of sufficient
bloom, resort to other orchards was made, since in all cases, only trees in good
bloom were used.
During the first year of our work as many crosses as possible were placed
on a single limb, in order to give each cross an even chance with others. In 1929,
■/ / /
/
/
/
/
/
/j/V/i//va//v/\///:
a ~\ J ~
A
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•A
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/w v yj v r v ° n
3D 1
si
sy
\
J
I 1 »
Sfai/ 26 - June 9. /AX?
Sfai/23-June//. /028
Fig. 5. — Thermograph records during blooming period, 1928-30, Kentville, N.S. (original).
however, six trees of each variety were selected and in 1930-1932, ten trees. A
different limb was selected on each, for each cross that it was desired to make.
In order to reduce to a minimum any error resulting from differences in limbs
from different sides of the tree a rotation of the different hand pollinated limbs
was practised. This method was carried out throughout the experiment.
38
—
o
M
g3
e
p.
39
Owing to nutritional variation between trees and even between limbs on
the same tree, a certain number of laterals in all limbs used in the crossing work
were selected to be self-pollinated, to establish a uniform basis for comparison
and to reduce error to a minimum. Owing to the fact that this method tended
to complicate record taking this practice was discontinued in 1932 and individual
limbs were also used for selfing tests.
During the first year paper bags were used, but it was found much more
convenient and equally effective to use cheese cloth bags covering the entire
limb. The large sets obtained from suitable crosses under these conditions do
not indicate that the normal process of pollination and fertilization was inter-
fered with by this treatment.
When the majority of stigmas for any variety were receptive they were
brushed with the appropriate pollen, applied by means of a camel's hair brush,
all blossoms that had not reached or had passed the receptive stage being removed.
After the stigmas commenced to wither the bags were taken off.
In these studies emasculation was neglected in order to eliminate work and
to make it possible to perform a very large number of pollinations. A word of
explanation will make clear the reason for this practice. The object of these
investigations was not to secure seed from various crosses for breeding work,
but to test the value of the pollen of one variety as a means of improving the
set of the variety considered as a female parent. As tests of self-fruitfulness
were conducted in the manner already described, the per cent of self-fruitfulness
obtained may be compared with the result of each cross on each limb. While
emasculation might provide better control, as far as contamination from its own
pollen is concerned, it reduces the number of pollinations possible and provides
a further source of error due to emasculation injury.
The low, and, in many cases, almost negligible set obtained from most self-
pollinations under bags, further reduces the chances of error and, when it is
considered that all pollinations were made with previously prepared pollen applied
to the stigma of the flower as far as possible before their own anthers had
dehisced, it will be seen that this source of error is greatly reduced. Further-
more, a study of the characteristics of seedlings obtained from the seed saved
from the various crosses, indicates that selfing could not have taken place to
such an extent as to prevent the results of these tests from being very significant.
In the case of Baldwin considerable selfing undoubtedly occurred, this variety
showing a high degree of self-fruitfulness in all years, but, this fact being clearly
recognized, it does not affect the nature of the results from a pollination
standpoint.
Our conclusions with respect to the different crosses are based upon a
consideration of (1) the count of fruit as obtained after the unfertilized blossoms
have been shed, and (2) the percentage fruit that remains after the "July drop"
and (3) upon the fruit obtained at picking time. The term "set," as used in
this report, applies to the first of these, i.e. the count made before the "July
drop." This, by some workers, is considered the best criterion of the value of
different crosses, as they consider that nutritional factors play a large part in
the later drop. The term "per cent fruit," as used in this report, refers to the
percentage fruit that remains after the "July drop."
After a careful study of all relevant data it would appear that this figure
affords the best index of cross-fruitfulness or unfruitfulness. In the case of some
varieties there is little difference between the "per cent set" and "per cent
fruit." Gravenstein may be cited as an example of such a variety. In other
cases the original set for all male parents may be much the same, but, after the
"July drop," a wide difference becomes apparent between diploid and triploid
male parents. An example of the foregoing is Stark. The percentage that
remains on the tree at picking time is usually little different, except for abnormal
40
conditions, or for purely accidental causes, as high winds, which, when they occur,
considerably reduce the value of this figure. Another point that has been con-
sidered in weighing the value of various crosses is the question of seed production.
The term "per cent seed" refers to the seed produced from the original number
of blossoms pollinated and the term "per cent seedlings" refers to seedlings
produced from the original number of blossoms pollinated. The average num-
ber of seed per fruit was also found to be significant.
In these experiments we have not recorded the number of fruits borne on
a spur. While it might doubtless be advantageous to take into account the
number of fruiting centres in expressing results, the large number of pollina-
tions made, the fact that only normally blossoming limbs were selected, and the
length of time over which the work has been carried out, are considered to have
evened out spur differences and to give a valuable figure on which to base
comparisons.
Two practices are commonly followed in expressing results of pollination
studies. One is to use only the per cent fruit obtained from the original number
of blossoms pollinated, the other (2) is to express results as "percentage of a
commercial crop." It is pointed out by those who follow the latter practice
that to express results only in terms of blossoms that set fruit is to ignore
important factors which influence the set of fruit, particularly in view of the fact
that a percentage of fruit that might be ample with a heavy bloom, would be
very inadequate when the bloom was light. Furthermore, the same percentage
may be obtained in cases in which widely varying distribution of the fruit on
the limbs may be obtained. Whatever method is followed is arbitrary and
it seems to be just as difficult to lay down a definite rule as to what consitutes
a commercial crop, as to interpret results on the basis of percentage fruit
obtained, which, at least, forms a basis of comparison between varieties. In
our work, therefore, we have chosen to use the figure showing the percentage
blossoms that develop into fruit. Taking into account the normal bearing
habits of the different varieties concerned and bearing in mind the fact that the
practice followed was to select for pollination only limbs in good bloom, it is
considered that this method meets the needs of the case and renders intelligent
comparisons possible. The figure of five per cent, selected by some workers
as representing a commercial set, is a useful one, though, as indicated elsewhere,
the bearing habits of varieties differ and the proportion of blossoming spurs
would have an important influence.
3. POLLEN TESTS
(a) METHOD
In order to keep a careful check upon the results of hand pollinations, all
pollen used in the work was tested for germination. Blossoms were gathered
from trees of the required varieties before fully opened, the stamens stripped
of their anthers by means of forceps, and dried in the sun or on the top of
an electric oven running at 50°C. Ordinarily the pollen was stored in small
open petrie dishes in desiccators or in a large chamber used as a desiccator.
Wherever possible mixed samples from the different trees were secured, to
eliminate error due to differences in vigour in the pollen tree.
Each petrie dish was labelled with the name of the variety of pollen, and
the date gathered. Vials for use in the orchard were correspondingly labelled.
As the pollinators went out each morning the pollen was transferred from the
petrie dish to the vial with duplicate label.
The daily germination tests were run as follows: The medium 15 per
cent cane sugar solution with -5 per cent agar added, was sterilized and run
into a number of test tubes, which were kept plugged, a fresh one being used
for each day's tests, thus eliminating all possibility of contamination of the
medium.
41
Three slides were put up with each variety of pollen, the pollen being
stirred with a needle into the agar on a cover slip, which was then inverted
over the cavity of a well slide, the edge of the well being coated with vaseline
to make it airtight. After 24 hours germination at room temperature the
cover slips were transferred to ordinary slides on each of which was a drop of 5
per cent lactic acid. The acid acted as a killing agent, enabling each slide to be
kept for several days and read at leisure.
Three fields containing 100-150 grains were read on each slide giving a
total of approximately 1,000 grains for each variety. At the beginning of the
investigation tests were run on various germinative media, but finally 15
per cent sugar agar was selected as being most satisfactory. The tests were
run at approximately 68°F.
(b) RESULTS
The accompanying tables indicate the results by years and show the actual
per cent germination obtained from the pollen samples used in our studies.
TABLE No. 7— GERMINATION OF APPLE POLLEN (1928-1932)
Variety
1928
1929
1930
1931
1932
Annie Elizabeth (d)
(3)53-75
(3) 21-00
(2) 45-27
(2) 52-64
(2) 21-75
(3) 44-44
(2)53-42
(i)37-ll
(3) 15-00
(i) 60-00
(2) 48-05
(2) 10 00
(2) 61-51
(ii)38-40
(2) 10-55
(4) 33-94
Baldwin (t)
(4) 0-22
(3)56-60
(2)85-18
(2) 87-50
(2) 52-20
(2)47-61
(«) 24-77
(2) 92-50
(3j 88-75
(2)31-00
(2) 46-75
(i) 85-50
(2) 46-75
(2)80-12
(2) 92-03
(2) 93-00
(2) 27-67
(3) 10-67
(4) 2-04
(5) 3-67
(i) 25-04
(5) 2-31
(3) 13-00
(3) 53-95
(4) 72-40
Ben Davis (d)
Bishop Pippin (Yellow Bellflower) (d)
(4) 68-00
/3) 5-60
(2) 76-00
(3) 38-90
Blenheim (t)
700
(<) 15-07
(5) 2-66
(8) 16-70
(5) 20-00
Chas. Ross
Cox Orange (d;
29-50
(3) 23-53
(4) 54-25
(<9 52-46
(3) 56-29
Crimson Beauty (t)
Crimson Bramley (t)
(3) 30-00
(3) 27-24
(3) 57-91
(2) 80-83
Delicious (d)
Duchess (d)
Emilie
Fallawater
Fameuse (d)
Golden Russet (d)
1=) 25-51
(3) 14-76
(3) 76-25
(7) 33-78
(4) 46-10
(6) 25-38
(7) 35-69
(5) 47.44
(3) 44-29
(4) 27-41
(») 24-00
(4) 13-65
(7) 17-21
(i) 21-63
(2) 18-56
Gravenstein (t)
200
Grimes Golden (d)
Hubbardston
Jonathan (d)
(3) 36-22
(3) 1-66
(3) 70-83
(2)49-73
(") 3-00
(3) 70-62
(3) 33-33
(4) 74-40
(3)58-27
(3)51-00
King (t)
15 00
(5) 15-57
Kinkead
(s) 9-33
(7) 1-20
(3) 11-06
Lane's Prince Albert
Lipton
Lobo
(2) 70-67
Longley Pippin
42
TABLE No. 7— GERMINATION OF APPLE POLLEN (1928-1932)— Cone.
Variety
1928 1929 1930 1931
1932
Melba
Maiden's Blush. .
Mam. Blacktwig.
Mcintosh
(2) 38-67
12 00
(3) 14-67
(4) 35-15
Milwaukee
Nonpareil (Roxbury Russet) (t),
Opalescent
Ontario (d)
Ortley
Red Astrachan
R. R. Beauty
R. W. Reinette
R. I. Greening (t)
Rome Beauty
Ribston (t)
Salome
Stark (t)
(3) 15-44
(») 77-65
(o 66-00
(3) 32-11
(2) 53-33
(2) 40-20
(2) 29-20
(10) 36-25
(2)89-86
(U 15-76
(3) 69-27
(3) 0-59
(-) 74-39
Spy (d).
Seek-no-Further. . .
Stayman Winesap.
St. Lawrence
Wagener (d)
(3) 24-00
(3) 72-26
41 00
(») 5211
(3) 69-41
(3) 50-00
(i)48-36
(«) 55-80
(l0) 30-07
(2) 0-00
0) 40-53
(2) 19-62
(3) 64-82
(3) 14-00
0) 39-11
(3) 68-40
(2) 42-70
Wellington (d)
Winter Banana
Wolf River (d)
Worcester Pearmain (d)
Yellow Transparent
York Imperial
(M 74-34
57-00
(3) 71-83
(3) 100-0
96-00
(3) 90-00
(>) 48-66
(7) 33-53
(2) 83-97
(2) 48-00
(*) 20-13
(3) 70-00
(2) 61-25
(2) 36-66
(3) 57-00
(3) 25-22
0) 86-89
(2) 26-22
(2) 62-20
, , 55
(2)87-00
- .-,:■;,
(2)89-ll
i 92-tO
(*) 58-03
(0 57-05
(2) 48-34
(3) 38-59
(3) 21-62
(*) 19-23
(») 18-31
(*) 23-32
(3) 54-76
(*) 68-35
0)48-04
(*) 73-28
(3) 58-43
{*) 60-56
(*) 63-13
Note (!)— In 1928-1929. 10' „ sugar was the medium used.
" 1930-32, 15% sugar-agar was employed.
Note (2) — Figures in brackets indicate age of pollen in daws.
Note (»)— t=triploid; (d)=diploid.
Considerable error is to be expected in germination tests in spite of every
possible precaution and the making of much larger counts than usually con-
sidered necessary. Neither should it be supposed that germination teste made
under artificial conditions arc exactly indicative of the fertilization capacity of
pollen, for many other factors are involved. It will be noted, however, that
some varieties show a uniformly higher germination than others. Although no
direct correlation between germination and set has been arrived at. it is generally
observed that a pollen with high germination will give a better set than a pollen
with low germination; sometimes higher than would be expected, sometimes
lower. Those with a generally low percentage germination and a high percentage
of aborted and shrivelled grains include Blenheim. Crimson Bramley, Baldwin.
R. I. Greening, Gravenstein, Bramley, King and Ribston which are triploids,
to which might be added Nonpareil and Stark, and several others which, judging
from their behaviour in this and other respects will probably be found to be
triploids; while of the known diploids. Spy. Delicious, Ben Davis. Jonathan.
Yellow Transparent, Ontario, Red Astrachan and others have a relatively higher
germination and a lower proportion of aborted grains.
In this connection Einset (1930) states: " In view of the eytologiea!
evidence, it seems apparent that the low pollen germination is not directly
responsible for the ineffectiveness of the triploid varieties. Gravenstein and
43
Baldwin, as pollinizers. Even though the percentage of viable pollen is low,
there should remain a sufficient supply in many cases to insure fertilization and
subsequent seed development. It seems obvious, however, that the irregular
chromosome distribution, which has supposedly cut down the percentage of
#
*
Af
w*
4
•
0 i ' ■» «
ft
#
«r
p *
•
** *
«*
% ."*
jj o
»i-j®t^
4
5 K ■ 6
Fig. 7. — Germinating pollen from certain apple varieties:
(1) pollen of Baldwin; (2) King; (3) Wagener; (4)
Golden Russet; (5) Spy; (6) Gravenstein (original).
viable pollen, is now causing further abortion in the zygotes." This agrees with
the observations of Kobel (1930 and 1931) that a high pollen germination is
characteristic of diploid varieties -and a low germination of triploid varieties.
The results of all our tests are in agreement with the foregoing conclusions.
44
An interesting feature brought out by our tables is the variability of the
results of germination tests. There is undoubtedly a large factor of error in
this work, but it is apparent that in diploid varieties the pollen is generally
good, in triploids generally poor. Furthermore, in some seasons the germination
is proportionally better than in other seasons. As already indicated the pollen
tests carried out in connection with the foregoing studies were undertaken solely
as a check on the germination of the samples used and, as such, appear to be
reasonably adequate. Heilborn (1932) rightly points out that most germina-
tion percentages are based on too few counts. He further contends that a
proper comparison between the pollen of different varieties cannot be based upon
percentage figures of germination, determined without due regard to the amount
of empty pollen grains characteristic of each variety and without a very strict
control of the conditions prevailing during germination experiments. He con-
siders that percentage germination figures bring out one thing only, viz., the
profound difference between diploid and triploid sorts. He contends that all
differences in pollen morphology are not due to chromosome aberation and that
triploid and diploid varieties must be treated separately. In evaluating diploid
varieties he considers it essential to use viability figures i.e. germinability instead
of germination percentage. He divides diploid varieties into three categories on
this basis and concludes that in such varieties there is a sharp distinction
between wholly fertile and partially sterile varieties, of which only the first
mentioned should be regarded as perfect pollen producers. He presents evidence
to show that the sterility has a genetical basis and is, to a high degree at least.
independent of climatic or metabolic conditions, being caused by lethal gene
combinations1.
(i) Other Data. — Experiments to determine the optimum temperature for
pollen germination under artificial conditions, showed considerable apparent
difference between varieties, the point varying between 17.8° C. and 25.6° C,
Germination occurred from all temperatures above freezing to about 57° C, but
IO 15 SO 25 SO
sd?<? o/ /h//e/? //? Dat/s I 3&/aW//7
Fig. 8.- -Influence of age on germinability of Baldwin pollen
under different conditions of storage (original).
at the lower temperatures pollen-tube growth was very slow, finally, however,
attaining the length characteristic of the variety. Pollen retains its viability
best when stored in open petrie dishes in desiccators, especially in damp weather.
Under these conditions good germination is obtained for several days. Northern
Spy showed greatest longevity under the conditions of the test, germinating up
to 29 per cent when 10 days old, 3.06 per cent at 23 days, but no germination
at 30 days. Germination at 3 days was 70 per cent. Where stigmas of apple
45
Open tnroom
Open /n cfess/cafor
//7 via/ incfessica/or"
o *-■
5 "10 15 20 25
s4/?e o/Po//es? /n Days E Grare/7s/e//?
so
Fig. 9. — Influence of age on germinability of Gravenstein pollen under different
conditions of storage (original).
Open /r? room
Oper? m afess/cafor
//? ria/ //? cfess/ca/or
Fig. 10.
^?<?e ofPo//e/7 //? £&*/& M /C/>??
-Influence of age on germinability of King pollen under different conditions of storage
(original) .
46
varieties were introduced into the germinative media there was no evidence of
any effect on germination. Where foreign stigmas were introduced some of them
produced a lethal effect.
In experiments in carriage of pollen by wind, glass slides were smeared with
liquid petrolatum and placed in spore traps of the weather vane type at the edge
of the orchards at varying distances from the trees. Apple pollen was found on
all the slides up to 200 ft., the counts running as follows: 25 ft., 325 grains; 50
ft., 267 grains; 75 ft., 169 grains; 100 ft., 80 grains; 150 ft., 46 grains; and 200^
ai
80
,
70
J
V V 1
1
|60
V\ ,1
\
\
\
KP-^
^
V
\
\
Open //? roo/r
?
k
\
\
{ \
\ \ y\
Operr //7 tfess
.
§50
vc&ror
\ X/ \
//7ria///7 cfess/crerror
t
\ \
t\
V \
1
\ \
^40
\ \
<5
^"u
I
\
ft
u
>30
//
1 1
\
$
I
J\i 1
\
fc
\
\
/ \\ 1
\
*
f w
\
\
\
?fl
1 \
in
\
\
•' : \
\
\
^■>»
^s
.>
5 IO 15 20 25
30
Fig. 11. — Influence of age on germinabilits of Spy pollen under different conditions of storage
(original I .
47
ft., 38 grains. This confirms the observations of Hockey and Harrison (1930)
carried out under identical conditions. Not all the pollen, however, was wind
carried. In fact, more pollen was placed on the slide by insects as indicated by
its occurrence in clumps of 35 to 50 grains, while hairs and pieces of insects legs
and wings were found on the slides. In other cases the scattered nature of the
pollen did seem to indicate carriage by wind. In 1932 also, an experiment was
conducted in which a current of air from an orchard duster was blown thoroughly
through a large bouquet of blossoming apple limbs adjacent to a tree also in
bloom. The large set obtained on this side of the tree, equivalent to that obtained
on hand pollinated limbs, indicated that the pollen had been well distributed by
this method. In spite of the foregoing, it appears that under normal conditions
the effect of wind carriage of pollen is very local and is not an important factor
in the pollination of the apple.
Experiments in the rate of pollen tube growth were made by pollinating Spy
blossoms with pollen of different varieties and clipping the stigmas at definite
intervals thereafter, and noting the set. Considerable differences were noted in
the time required to effect fertilization, as measured by the set secured, between
the results obtained in 1928 and those obtained in 1931, this difference being
apparently correlated with weather conditions. In 1931 maximum sets were
obtained in 48 hours, whereas in 1928, the 60-hour interval gave optimum results.
Little consistent difference was noted between the different pollen varieties, except
when Spy itself was used, in which case fertilization was delayed, but these
selling tests only gave a set of -37 per cent, which is too small a number upon
which to base conclusions.
4. EXPERIMENTAL RESULTS OF POLLINATION EXPERIMENTS
WITH STANDARD VARIETIES
The results of all experiments with standard varieties are summarized in
the following tables and discussion. In view of the importance of chromosome
constitution in the behaviour of varieties, it has been considered advisable to
classify the crosses as, (1) diploid x diploid, (2) triploid x diploid, (3) diploid x
triploid and (4) triploid x triploid.
Each variety is then discussed in detail from the following standpoints: —
(i) Results obtained by other workers.
(ii) Value from the standpoint of self-fruitfulness as determined by "set "
and " fruit " secured.
(iii) Value as a female parent, using the same criteria.
(iv) Value as a male parent considering " set," " fruit " and " seeds " pro-
duced. The " per cent seeds " in our tables is calculated from the 1930 and 1931
figures only, as indicated below: —
Variety
Total
blossoms
Total
seeds
Baldwin
18,985
22,388
21,584
16,613
22,742
4,767
1,410
Cox Orange
11,548
Golden Russet
11,972
Gravenstein
3,117
King 7.
2,820
Spy
2,578
(v) Evidence from tent series,
(vi) Summary of results with all varieties,
(vii) Other data, if any.
(viii) General summary for variety.
Finally, a general summary based on the results of tent and hand pollination
studies, with special emphasis upon findings of a fundamental nature, is presented.
48
(a) BALDWIN
(i) Results of Other Workers. — MacDaniels (1927) in a summary of pollina-
tion studies with this variety, illustrates that self-fruitfulness is not a fixed factor
in that or any variety, but varied greatly according to differences in environ-
mental or other conditions. Other workers, Overholser, (1927), Morris (1921),
MacDaniels and Heinicke (1929) and Howlett (1927) all record this variety as
either self-fruitful or partially self-fruitful. Furthermore, all workers record
Baldwin as an excellent female parent, but poor, or at best, only fair as a male
parent.
(ii) Results of Selfing Tests on Baldwin (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
6,856
1,711
24-96
437
6-37
The results of hand pollination tests at the Experimental Station with this
variety, indicate that it is very self-fruitful compared with all other varieties
tested. The selfing tests over a period of five years show a percentage " set " of
24-96 and of "fruit" 6-37. It should be emphasized, however, that, though
Baldwin is very self-fruitful and gives, when selfed, a better yield than with
many other varieties, it does not give as good results as when crossed with highly
cross-fruitful varieties such as Cox Orange.
(iii) Results from Baldwin
as Female Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
28,178
11,672
41-42
3,232
11-47
Its value as a female parent is high, as indicated in the above table, giving
a percentage "set" of 41-42 and a percentage "fruit" of 11-47. All diploids
tested on Baldwin, such as Cox Orange, Golden Russet, and Spy, proved to be
effective pollinizers for the variety. Mcintosh and Wagener were tested in 1932
only, and gave every indication of being equally as effective as the other diploids
tested over the longer period.
(iv) Results from Baldwin as Male Parent (1928-1932).
Total
blossoms
Total
set
Per cent
set
Total
fruit
Per cent
fruit
Per cent
seeds
26,841
2,974
11-08
681 2-54
7-43
By all criteria used Baldwin gives relatively poor results as a male parent,
the per cent "set" for the five-year period being 11-08, the per cent "fruit"
2-54, and the per cent seed 7-43.
(v) Evidence from Tented Series. — Additional evidence from tent studies
shows that self-fruitfulness takes place to a very marked degree, the tented trees
(with bees and no bouquets) over a four-year period (1929-1932) giving an
average percentage fruit of 7-77. The untouched tree (no bees and no bouquets),
over the same period, only gave a percentage fruit of 3-49, indicating that selfing
cannot take place to a satisfactory degree without the aid of pollinating insects.
The open pollinated tree, representing results from a mixture of various pollens,
Fig. 12. — Photographs illustrating results of experimental pol-
linations: (1) Baldwin selfed; (2) Baldwin x Cox Orange;
(3) Baldwin x King (original).
60796—4
50
gave 10-40 per cent fruit over a four-year average, while the tree with bees and
Blenheim bouquets, over the same period, resulted in 4-96 per cent, indicating
cross-unfruitfulness between these two varieties. On hand pollinated limbs used
in the tent studies, we find an effective pollinizer like Cox Orange to give an
extremely high percentage, where the yield over the whole tree is reduced as in
the case of the treatments, e.g., the trees with no bees and no bouquets. Limbs
hand pollinated with an ineffective pollinizer in the tented series gave a low per-
centage fruit, indicating similar results to that of whole trees tented and treated
in a similar manner.
(vi) Summary of Results with all Varieties on Baldwin (1928-1932).
Cox Orange
G. Russet
Graven stein
King
Spy
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
5,718
14-64
5,761
12-25
5,186
8-93
5,436
8-65
6,077
12-44
The above tests show that the triploicl varieties, mainly Gravenstein and
King, gave satisfactory results when used as male parents on Baldwin. However,
the possibility that a percentage of this is due to selfing cannot be excluded, and,
if emasculation tests were practised, the results from these sorts might have been
lower. That selfing may not be the entire explanation is indicated by the fact
that the pollen of certain triploids when used on Baldwin gave a percentage fruit
considerably in excess of those obtained by selfing, as indicated elsewhere.
This brings forth the necessity of further work under emasculated condi-
tions to determine the true value of these male parents. All the diploids tested,
Cox Orange, Golden Russet and Spy gave slightly higher results than the men-
tioned triploids and may be readily termed as excellent pollinizers for Baldwin.
(vii) Other Data.- A considerable number of blossoms were pollinated with
R. I. Greening pollen during the season of 1932 to determine its value as a male
parent. The results from this triploid were very unusual, a percentage fruit of
14-86 being obtained from a population of 1,521 blossoms. Other triploids such
as Nonpareil and Blenheim gave depressing effects when used as bouquets in
tented trees with bees.
(viii) General Summary for Variety. — This variety exhibits a high degree
of self-fruitfulness, 24-96 per cent " set" and 6-37 per cent " fruit" over five-
year period, the highest for any variety tested. The bagged and untouched blos-
soms gave a very low per cent fruit, ranging from 3-70 on the open pollinated
trees, to 1-01 on the tented trees supplied with bees and no bouquets, i.e. selfed,
over a four-year period. As a female parent Baldwin stands high, giving an
average of 11-47 per cent for the varieties tested over a period of five years, this
figure being larger than the open pollinated average of 10-40 per cent for a four-
year period. Baldwin, being classified as a triploid, might be expected to. and
actually does, give relatively poor results as a male parent, 2-54 per cent being
obtained on the varieties tested.
It should be understood that Baldwin is a markedly biennial bearer and
that our tests had, therefore, to be made on different tree- each year, trees being-
selected that had not blossomed or had not blossomed heavily the previous year.
This habit markedly diminishes its commercial value. It is known, however, as
a reliable cropper every other year, almost invariably bearing crops when bloom
is obtained, whereas, certain other varieties are notably uncertain. The high
degree of self-fruitfulness exhibited by this variety is. no doubt, associated with
this habit.
51
(b) COX ORANGE
(i) Results of Other Workers. — Crane (1926) lists this variety as partially
self-fruitful, and points out that the trees bear early. Only moderate crops
result from selfing and full crops when crossed. Auchter (1921) of Maryland
classifies Cox Orange as self-fruitful, while on the other hand, Corrie (1916),
Sutton (1919) and Hooper (1921) place it as self-sterile or self-unfruitful. Crane
and Lawrence (1930) classify it as a diploid, thus indicating its value as an
effective male parent.
(ii) Results of Selfing Tests on Cox Orange (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
9,016
1,136
12-60
163
1-81
The hand pollinated results at Kentville indicate that this variety gave a
low percentage " set " and " fruit " in selfing tests, the average for five years
being 12-60 and 1-81 respectively. The latter figure indicates a low value from
the standpoint of self-fruitfulness and the necessity of the provision of cross-
fruitful varieties in order to secure commercial crops.
(iii) Results from Cox Orange as Female Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
37,091
10,526
28-38
2,869
7-74
As a female parent the average figure over a five-year period was 7-74,
this result being obtained by using pollen from standard varieties. This figure is
higher than that obtained from open pollinated trees, which gave a percentage
fruit of 6-74, over a four-year period. All diploids tested, Golden Russet,
Mcintosh and Wagener, proved effective pollinizers on Cox, excellent results being
evident in each case.
(iv) Result
s from Cox
Orange as Male Parent (1928-1932)
Total
blossoms
Total
set
Per cent
set
Total
fruit
Per cent
fruit
Per cent
seeds
27,890
9,638
34-56
3,202
11-48
51-58
As a male parent this variety proved excellent in all cases, the five-year
average being 11-48 per cent fruit. This result is in line with that obtained with
all diploid varieties tested and enhances the value of this variety in commercial
plantings. The high percentage seed obtained by the use of this variety is con-
firmatory of the " set " and " fruit " figures.
(v) Evidence from Tented Series. — This variety was not included in the
tented series, thus our information, pertaining to self-fruitfulness, is confined
entirely to hand pollination tests.
60796—41
52
dhk \*^.±2*~
**YTr.i7?
Ftg. 13. — Photographs illustrating results of experimental pollina-
tions: (1) Cox Orange selfed; (2) Cox Orange x Golden Russet;
(3) Cox Orange x King (original).
53
(vi) Summary of Results with All Varieties on Cox Orange (1928-1932).
Baldwin
Graven stein
Golden Russet
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
6,376
2-51
6,586
4-97
6,190
13-99
King
Mcintosh
Wagener
6,887
2-47
5,186
10-99
5,866
13-23
The triploid varieties, namely, Baldwin, Gravenstein, and King, gave uni-
formly poor results on Cox. The diploids, Golden Russet, Mcintosh and Wagener.
on the other hand, gave excellent results throughout, indicating clearly that onl>
such sorts should be used to pollinate Cox Orange.
(vii) Other Data. — To illustrate the value of cross-pollination, where solid
blocks of one variety are planted, several limbs were hand pollinated with Cox
Orange pollen in a ten-acre block of solid Blenheim at Lakeville. The results
were very significant, since, in all cases where Cox was used, a heavy percentage
fruit, varying from 20 to 75, resulted, this being an extreme contrast to the
remainder of the block in which the set was light and scattering, in most cases
below one per cent. This experiment was repeated on a small scale in a large
number of orchards where Blenheim were reported to be giving poor returns.
In all cases, the results were marked and, in many, very spectacular; the hand
pollinated limb being laden with fruit in contrast to the other limbs with few
or none. Similar, but less spectacular results were obtained on Stark.
(viii) General Summary for Variety. — This variety may be considered
to be commercially self-unfruitful on the basis of a five-year average, although a
low percentage of fruit was obtained in most selfing tests. It is an excellent male
parent, giving satisfactory results for all varieties that blossom at approximately
the same time and, being somewhat irregular in its blossoming habits, it is useful
on an unusually large range of varieties. As female parent in hand pollinated
tests, Cox has given a high average percentage fruit, the figure averaging higher
than the open pollinated results.
(c) GOLDEN RUSSET
(i) Results of Other Workers. — Sax (1922) states, that, for practical pur-
poses, all Maine apples are " self sterile " from the commercial standpoint.
Ben Davis, Baldwin, Golden Russet, R. I. Greening, Northern Spy are all men-
tioned as " interfertile," with the exception of Greening and Baldwin, as pollen
parents.
(ii) Results
of Selfing Tests
on Golden Russet (1928-1932)
Total blossoms
Total set
Per sent set
Total fruit
Per cent fruit
8,016
1,009
12-59
139
1-73
Golden Russet shows a fair degree of self-fruitfulness under the conditions
of these experiments. This variety is rather variable in its bearing habits, and
when grown on the heavier soils appears to be more fruitful. The average figure
from selfing over five years is 12-59 per cent " set " and 1-73 " fruit," indicating ?
low average value from the standpoint of self-fruitfulness.
54
.* V
Fig 14.— Photographs illustrating results of experimental pollinations: (1) Golden
Russet self ed; (2) Golden Russet x Mcintosh; (3-10) Golden Russet x Baldwin;
(3-11) Golden Russet selfed (original).
55
(iii) Results from Golden Russet as Female Parent (1928-1932)
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
25,377
5,335
21-02
1,042
411
Our results show Russet to be rather poor as a female parent, the average
being 21-02 per cent " set " and 4-11 "fruit" (1928-1932). Mcintosh and Cox
Orange were the only diploids tested on this variety, both proving very satis-
factory pollinizers. As indicated previously, the percentage fruit to bloom is
considerably lower on the light sandy soil at Kentville than appears to be the case
on the heavier types of soil, such as are found in Lakeville and similar districts.
Thus, the value of Golden Russet as a female parent may vary to a marked
degree, depending upon the locality in which the tests are made and the con-
ditions under which it is grown.
(iv) Results from Golden Russet as Male Parent (1928-1932).
Total
blossoms
Total
set
Per cent
set
Total
fruit
Per cent
fruit
Per cent
seeds
28,341
10,993
38-79
3,185
11-24
55-47
As a male parent Golden Russet is in the front rank giving an average per
cent "set" and "fruit" and "seed" of 38-79, 11-24 and 55-47 respectively.
Being a desirable commercial variety it is particularly valuable as a poilinizer in
any scheme of orchard planting.
(v) Evidence from Tent Series. — Tented tests were not conducted with
this variety, thus all information available as to its self-fruitfulness is limited to
the hand pollinated tests.
(vi) Summary of Results with All Varieties on Golden Russet (1928-1932).
Baldwin
Cox Orange
Gravenstein
King
Mcintosh
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
Total
blossoms
Per cent
fruit
5,333
2-33
5,355
7-51
4,995 2-28
5,767
2-15
3,927
7-08
Baldwin, Gravenstein and King varieties gave poor results throughout, as one
might well expect, these varieties being triploids. Cox Orange and Mcintosh, as
pointed out previously, produced excellent results and one may reasonably
assume, on the basis of similar tests, that any diploid, with suitable overlapping
of the blossoming periods, would prove satisfactory as a poilinizer for Golden
Russet.
(vii) Other Data. — To illustrate further the point regarding the varying
degrees of self-fruitfulness in relation to locality, we find that the hand pollinated
tests conducted in a Golden Russet orchard on a heavy loam soil at Wolfville
gave a percentage fruit of 6-34 as a female parent. This figure is over two per
cent higher than the five-year average. This is in line with the current opinion
with respect to this variety, though the possibility of other factors influencing
the foregoing result is not excluded.
56
(viii) General Summary for Variety. — Although Golden Russet is listed
as " self sterile " in Maine, our selfing results indicate a rather low degree of
self-fruitfulness, with considerable variation from year to year. As a male
parent, it is very effective, being equally as good as Cox Orange and Spy in this
respect. Its value as a female parent has been elaborated in the foregoing dis-
cussion and may be considered of variable nature, tending to be poor on the
lighter types of soil. Mcintosh and Cox Orange are the only satisfactory pol-
linizers tested.
(d) GRAVENSTEIN
(i) Results of Other Workers. Overholser (1927) states that this variety
is self-unfruitful, giving a per cent set of -09. His work further showed that
Gravenstein was an ineffective pollinizer for R. I. Greening, Jonathan, Delicious
and Baldwin. He found Delicious to be an effective pollinizer for the variety.
Morris (1921) lists Gravenstein as a partially self-fruitful variety, as also does
Vincent (1915). However, we find the latter cases to be the only exceptions to
the general belief that Gravenstein is highly self-unfruitful. Wellington, Stout,
et at. (1929), working in New York state, obtained no set where selfing was
practised. The majority of writers record Gravenstein as a good female parent
and wherever diploid varieties are used as male parents, good yields are obtained.
On the other hand, due to the fact that it is a triploid, we find it giving poor
results wherever used as a male parent.
(ii) Results
of Selfing Tests on Gravenstein (1928-1932).
Total blossoms
T otal set
Per cent set
Total fruit
Per cent fruit
7944
193
2-43
91
115
In the hand pollinated selfing tests at Kentville. Gravenstein has proven
to be the most self-unfruitful of the six standard varieties under test, the average
for five years being 2-43 per cent " set" and 1-15 per cent " fruit," the figures
based on a count of nearly 8,000 blossoms.
(iii) Results from Gravenstein as Female Parent (1928-1932).
Total blossoms
Total set
Per cent se1
Total fruit
Per cent fruit
32,225
6,876
21-31
3,048
9-46
As a female parent, Gravenstein may be considered good, giving average
per cent "set" of 21-34 and "fruit" 9:46. Cox Orange, Mcintosh, Golden
Russet and Wagener, all diploids, are excellent pollinizers for the variety and
when interplanted should give maximum results.
(iv) Results from Gravenstein as Male Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
Per rein seeds
21,911
4,729
21-58
1.114
5-08
18-76
As a male parent, although not as poor as Baldwin and King, it has not
been at all satisfactory. The results show an average percentage of 21-58
"set," 5-08 "fruit" and 18-76 seeds. The latter figures are higher" than might
be expected, keeping in mind the fact that this variety is a triploid form. Of all
this group it has given in our tests the highest value as a male parent.
57
FlG. 15.— Photographs illustrating results of experimental pol-
linations: (1) Gravenstein selfed; (2) Gravenstein x Wag-
ener; (3) Gravenstein x King (original).
5S
(v) Evidence from Tented Series. — It is interesting to note the degree of
self- fruit f illness which occurs in the tented series over a period of four years.
The tented tree with bees and no bouquets (selfed) gave an average of 2-12 per
cent fruit. This figure would tend to make one believe that Gravenstein is more
self-fruitful than hand pollination tests would appear to indicate. The cutting
back of the trees in order to put the tents in place appeared to increase the
number of seedless fruit, which Gravenstein has a tendency to produce. On the
other hand the trees with no bees and no bouquets gave an average of 0-67 per
cent fruit. This indicates clearly that natural selfing in the absence of bees is
exhibited only to a very limited degree. Open pollinated trees showed the high
percentage fruit of 9-91 and, where an effective pollinizer, viz., Wagener, was
used, 10-90 per cent of fruit was obtained. In the cases where B-lenheim
bouquets were introduced we find the average over the four years reduced to
1-14 per cent fruit, the latter figure being less than that of the self-pollinated
trees. The hand pollinated results in the tented series show Wagener to be an
excellent male parent and a percentage fruit of 47-11 was obtained from indi-
vidual hand pollinated limbs on the untouched trees (i.e. no bees and no
bouquets) over the four-year period. On the open pollinated tree, the limb
hand pollinated with Wagener only gave a percentage fruit of 11-21. This
illustrates the fact that the results obtained on hand pollinated limbs are in
direct proportion to the total crop borne by all limbs over the entire tree.
(vi) Summary of Results with All Varieties
on
Gravenstein (1928-1932).
Baldwin
Cox Orange
Golden Russet
Total blossoms 1 Per cent fruit
Total blossoms | Per cent fruit
Total blossoms 1 Per cent fruit
4,854
0-87
5,441 15-25
5,104 12-72
King
Mcintosh
Wagener
5,857
I 1-52
I
5,030 12 01
5,876 14 06
The triploid varieties, namely Baldwin and King, tested on GravensteiD
gave uniformly poor results throughout, indicating the inadvisability of inter-
planting Gravenstein orchards with such varieties. All diploids tested on this
variety gave excellent results, as the above table indicates, and the varieties
chosen to inter-plant with Gravenstein depend largely on individual preference,
location, soil type, and market demand.
(vii) Other Data. — Unfavourable weather prevailed during the 1931 sea-
son. Three of the hand pollinated limbs in the tented series were pollinated on
May 23, the remaining three on May 25. The former gave an average per-
centage fruit of 27-85, the latter 8-60 per cent. The preceding figures indicate
that a higher yield is obtained if pollination is carried out when the stigmas
are first receptive rather than near the end of stigma receptivity. That is to
say, pollination results appear to be more favourable when the blossom first
opens. This result was consistent with other varieties observed.
(viii) General Summary for Variety. — Gravenstein is the most self-unfruit-
ful of the standard varieties grown in the Annapolis valley. In view of the
fact that it is a triploid, it makes a rather poor male parent. As a female
parent, this variety may be considered good and when such pollinizers as Cox
Orange, Golden Russet, Mcintosh and Wagener, all diploids, are present, excel-
lent results are obtained.
(e) KING
(i) Results of Other Workers. — Overholser (1927 1 in studies in California
found King to be self-unfruitful. Furthermore, he found it to be a very unsatis-
factory male parent, being similar to Baldwin in this respect. He found King
59
Fig. 16. — Photographs illustrating results of experimental pollinations: (1) King
selfed; (2) King x Wagener; (3) King x Baldwin (original).
60
to be a fair female parent, with Jonathan proving the most effective pollinizer.
Crane and Lawrence (1929), in experiments conducted at Merton, England, find
King to be partially self-fruitful, a percentage set of 1-9 being obtained. Wel-
lington, Stout, et at. (1929), found this variety to be also partially self-fruitful
in New York state, while Auchter (1921) lists it as self-fruitful in Maryland.
Other workers, e.g., Morris (1921); Chittenden (1926), and Lewis and Vin-
cent (1909) place King as a self-unfruitful variety. As a male parent the above
writers find it poor. Wellington, Stout, et at. (1929) found Delicious to be an
effective pollinizer for King, good commercial sets resulting.
(ii) Results
of Selfing Tests
on King (1928-
1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
7,221
1,072
14-85
257
3-56
The results over five years indicate that King is fairly self-fruitful, selfing
tests giving an average percentage "set" of 14-85 and "fruit" 3-56. This
figure may even be considered self-fruitful for the variety, because of the fact
that the open pollinated trees over the period tested gave only 4-74 per cent
fruit. In this connection also should be considered the large number of blos-
soms produced by this variety, the large size of the fruit and the annual bearing
habit of the King in many commercial orchards.
(iii) Results from King as Female Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
32,148
6,648
20-68
1,549
4-82
King as a female parent may be considered good, a "set" of 20-68 and
" fruit" of 4-82 per cent, being obtained over the five-year period. The above
figure is extremely good when one takes into consideration the fact that between
3-5 and 4 per cent fruit on a heavy blossoming tree will result in a good com-
mercial crop, with this variety. The diploids tested, Cox Orange, Golden Rus-
set, Mcintosh and Wagener, all increased the "set" and "fruit" percentage
above that of selfing and above that obtained where triploids were used. It
should be noted that a small increase of one half of one per cent is of great
economic importance in this variety, because of the low percentage fruit neces-
sary to give a satisfactory crop.
(iv) Results from King as Male Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per rent fruit
Per cent seeds
29,941
3,458
11-55
1,068
3-57
11' -40
This variety may be considered very unsatisfactory as a male parent,
being similar to Baldwin in this respect. The results for the pasl live year-
show a percentage "set" of 11-55, "fruit" of 3-57 and seed, 12-40. which is
quite in line with the results of other triploid varieties.
(v) Evidence from Tented Series. — The tent studies indicate that King is
commercially fairly self-fruitful. The "untouched" tests, that is. the tented
trees with no bees and no bouquets, gave a percentage fruit of only 1-03. The
61
open pollinated, with a percentage fruit of 4-74, exceeds the selfed trees by a
little over one per cent, the latter having an average of 3-32 per cent fruit
for the past four years. In the cases where Wagener bouquets were introduced
as a means of cross-pollination, the per cent fruit was increased nearly one per
cent, the average figure being 5-42. On the other hand, in those trees where
Blenheim was used, the per cent fruit closely approached that of selfing, namely
3-58. It might be well to state that King shows less difference between different
male parents than any variety tested, a habit associated with the very low per-
centage fruit to spur area. Even though the original set may show consider-
able differences, dropping takes place until the margin between crossing and
selfing results is greatly reduced.
(vi) Summary of Results with All
Varieties on
King (1928-1932).
Baldwin
Cox Orange
Golden Russet
Total blossoms
Per cent fruit
Total blossoms
Per cent fruit
Total blossoms
Per cent fruit
5,790
4-27
5,530
5-08
5,084
4-33
Gravenstein
Mcintosh
Wagener
5,144
4-08
4,565 | 5-56
1
6,035 | 5-58
I
The triploids, namely, Baldwin and Gravenstein, gave much better results
on this variety than one might expect, both showing an increase of one-half
of one per cent over the selfing tests. All the diploids, Cox Orange, Golden
Russet, Mcintosh and Wagener, gave an increase of one per cent over the
selfed tests and from one-half to one per cent over the triploids used. This
increase might appear of little importance in some varieties, but in the case
of King, with its normally low per cent of set to bloom, it is significant.
(vii) Other Data. — The results obtained during 1931 in a King orchard at
Wolfville, were uniformly lower than those obtained at Kentville in 1928, 1929,
1930 and 1932. This may be explained by the fact that the trees in the Wolf-
ville orchard are in an annual-bearing habit, whereas those used in Kentville
were decidedly biennial.
(viii) General Summary for Variety. — In summarizing the results from this
variety it may be stated that King is fairly self-fruitful from a commercial
standpoint. As a male parent it is rather poor, being next in line to Baldwin;
as a female parent it is good, when one takes into consideration its blossoming
and bearing habits, together with the large size of individual fruits. Triploid
crosses such as Baldwin and Gravenstein do not depress fruitfulness, as was
found to be the case when used with most other varieties tested, and all the
diploids tested showed their value as pollinizers by increasing the percentage
fruit to bloom, to the extent of one per cent in most cases.
(/) NORTHERN SPY
(i) MacDaniels (1928) in experiments in New York, reports Northern Spy
as self-unfruitful and found that, where pollen was not applied by hand, total
crop failure followed. Much greater variation in response to pollination is found
in trees of low vigour than in those growing under better conditions. MacDaniels
(loc. cit.) lists the suitable pollinizers for Northern Spy as Wealthy, Golden
Delicious, Rome Beauty, N.W. Greening, Tolman Sweet, and Delicious. How-
ever, because of the late blooming habit of Spy, Rome is the only dependable
source of pollen. Marshall, Johnson, et al. (1929), in Michigan, find Spy self-
unfruitful, but place it as an effective pollinizer and as a good female parent.
62
Fig. 17- Photographs illustrating results of experimental pol-
linations: (1) Spy self ed; (2) Spy x Golden Russet; (3) Spy
x Baldwin (original ) .
63
With one exception, viz., Gowen (1920), who obtained results indicating partial
self-fruitfulness, all investigators term Northern Spy self-unfruitful, but record
the variety as an excellent male and female parent.
(ii) Results of Selfing Tests on Spij (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
5,862
249
4-25
78
1 • 33
The hand pollinated results at Kentville during the years 1928-1931, inclu-
sive, proved the variety to be quite self-unfruitful, yielding an average of 4-25
per cent "set" and 1-33 per cent "fruit". This figure approaches that
secured in Gravenstein selfing tests, and may be considered the second lowest,
in regard to self-unfruitfulness, among the six standard varieties under test.
(iii) Results from Spy as Female Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
27,252
7,467
27-40
2,673
9-81
Spy is an excellent female parent, 27-40 per cent "set" and 9-81 per
cent " fruit " being obtained over the period. The diploid sorts gave very
satisfactory results on this variety, Ben Davis being especially good. Triploids
proved, on the other hand, to be unsatisfactory as male parents for Spy, and
in many cases no fruit was obtained. Other varieties tested at the Kentville
station, but not reported in this paper, are Delicious, Golden Delicious and
Red Rome Beauty, all of which gave good results and all overlap the Spy in
bloom to a satisfactory extent.
(iv) Results from Spy
as Male Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cen t fruit
Per cent seeds
6,077
2,838
46-70
756
12-44
54-08
The above results, as to the value of Spy as a male parent, are based entirely
on pollinations made on the Baldwin variety, and from these it may be con-
sidered an excellent pollinizer for the late blooming varieties. Spy was also
used in 1928 and 1929 as a male parent for Cox Orange and Golden Russet, a
per cent "fruit" of 14-44 and 10-60 respectively being obtained.
(v) Evidence from Tented Series.— The results from the tented series indi-
cate that Spy is quite self-unfruitful, a percentage "fruit" of 2-00 being
obtained from the selfed trees (bees and no bouquets) in the past four years.
The untouched trees (no bees and no bouquets) gave a percentage fruit of 0-85,
for the same period, which is nearly one per cent lower than the selfed trees, and
shows that natural selfing in the absence of bees is very low. In the case of open
pollination, we find a relatively high percentage fruit of 8-83 and, where an
effective pollinizer was used, the per cent fruit was 10-05. In contrast to this,
64
where an ineffective pollinizer was tried, the fruit was reduced to 2-70 per cent,
almost as low as the selfed trees. The fact that triploids- were used as ineffective
pollinizers in this case explains the low fruit percentage.
(vi) Summary of Results with All Varieties on Spy (1928-1932).
Bald
win
Ben Davis
CoxC
> range
G. Russet
King
Total
blos-
soms
Per
cent
fruit
Total
blos-
soms
Per
cenfc
fruit
Total
blos-
soms
Per
cent
fruit
Total
blos-
soms
Per
cent
fruit
Total
blos-
soms
Per
cent
fruit
4,488
2-41
4,785
15-92
5,843
14-58
6,142
11-98
5,994
3-59
The triploids, Baldwin and King, when used as male parents give very
unsatisfactory results, a very low per cent fruit resulting. Ben Davis, Cox Orange
and Golden Russet are effective pollinizers ; the first of these is most outstanding,
the blooming periods overlapping satisfactorily, but Cox Orange gives fair
results.
(vii) Other Data. — Tests conducted in an orchard at Greenwich, as to rate
of pollen tube growth within this variety, incidentally showed Ben Davis, Cox
Orange and Golden Russet to be the outstanding pollinizers under test.
(viii) General Summary for Variety. — We may consider Spy quite self-
unfruitful, being like Gravenstein in this respect. It is excellent as a male and
female parent; our figures show it to be superior in the former respect. Ben Davis
and Cox Orange are the only suitable pollinizers reported on. Rome Beauty is an
excellent male parent for the variety, and being a late blossoming variety is thus
a dependable source of pollen, but, in view of the fact that it has little economic
importance as yet in the Annapolis valley, no tests have been conducted to
ascertain its value under our conditions.
The summarized results from the standpoint of " set " and " fruit " are
included in table 8 and the result by groups, including also seed data in table 9.
TABLE No. 8.
-TOTAL RESULTS OF APPLE CROSSES WITH STANDARD VARIETIES
(1928-1932)
Male Parents
Female Parent
Baldwin
( 'ox
Orange
G raven-
stein
Golden
Russet
King
Spy
Per
cent
set
Per
cent
fruit
Per
cent
set
Per
cent
fruit
Per
cent
set
Per
cent
fruit
Per
cent
set
Per
cent
fruit
Per
cent
set
Per
cent
fruit
Per
cent
set
Per
cent
fruit.
Baldwin
Cox Orange
24-96
1619
8-42
2-33
18-89
6-37
6-37
2-51
233
0-87
4-27
2-41
48-46
12-60
37-67
28-95
18-26
38-75
14 -64
1-81
7-51
15-25
5-08
14-58
37-54
19-86
12-69
2-43
16-33
8-93
1-97
2-28
115
408
46 00
49-39
12-59
32-86
23-94
38-62
12-25
13-99
173
12-72
4-33
11-98
26-97
11-72
9-57
2-78
1 \ 85
7-84
8-65
2-47
215
l 52
3-56
3-59
46-70
12-44
Golden Russet
Gravenstein
King
Spy
4-25
1-33
65
TABLE No. 9.— THE FRUITFULNESS OF DIFFERENT TYPES OF CROSSES (1928-1932)
Cross
Total
blossoms
Total
set
Per
cent
set
Total
fruit
Per
cent
fruit
Seeds"
Per
cent
Aver-
age
number
per fruit
Diploid x Diploid
Diploid x Triploid
Diploid Selfed
Triploid x Diploid
Triploid x Triploid
Triploid x Triploid (without Baldwin as
Female Parent)
Triploid Selfed
43,294
46,426
22,894
60,284
32,267
21,645
22,021
17,790
5,538
2,394
19,573
5,623
2,210
2,976
41-09
11-93
10-46
32-47
17-43
10-21
13-51
5,242
1,342
380
6,308
1,521
588
785
12-11
2-89
1-66
10-46
4-71
2-72
3-56
75-70
9-93
6-38
36-79
13-49
6-81
9 04
"Seed counts made on basis of actual number of fruit harvested.
(h) SEED CONTENT IN RELATION TO FRUITFULNESS
Pollen of high germinability and good quality for crossing together with
relatively high seed content is associated with diploidy in apples, the reverse with
triploidy. Diploid varieties, as female parents, have consistently given a higher
seed content than triploid varieties and within the variety the seed content is
affected by the male parent, diploids giving more seeds than triploids in this
respect. Although diploid x diploid and triploid x diploid crosses are of approx-
imately equal value as to fruitfulness, the latter has a much lower average seed
content. Furthermore, though triploid crosses often exceed diploid x diploid in
fruitfulness, the latter produced a higher average seed content in these tests.
Percentage fruitfulness is generally proportional to seed content but is not neces-
sarily directly so, as explained above.
In seed germination, triploids as a group show a much lower germination
than diploids, i.e., when used as females; on the other hand the male parent has
no measurable effect on germination.
The results from the standpoint of viable seedlings resulting from the fore-
going types of crosses, are consistent with those obtained with seed. The order
of seedling production was the same, viz.: (1) diploid x diploid, (2) triploid x
diploid, (3) diploid x triploid and (4) triploid x triploid. Details are discussed
in another paper.
(0 RELATION OF SEED CONTENT TO WEIGHT
As already indicated, many workers have claimed a correlation between
weight and seed content in the apple. The fact that one-sided apples show some
of the carpels empty on the corresponding side is a matter of general observa-
tion. Samples picked at random offer little evidence in this connection, since
many factors influence size and weight of fruit, and a disturbing factor is intro-
duced in the utilization of fruits resulting from mixed pollination. On the other
hand, trees with a very low set due to an unfruitful cross produce few apples,
and those that do set may grow abnormally large due to favourable nutritional
conditions. For this reason, it appears desirable that the samples selected should
be produced under uniform and normal conditions. For the foregoing reason in
1931 we selected two varieties, Gravenstein, as representative of a triploid
variety with very low seed content, and Northern Spy, representative of a diploid
variety with an exceptionally high seed content. For our study we selected a
tented tree of each variety which had been provided with a hive of bees and an
effective pollinizer, Wagener in the case of Gravenstein, Ben Davis in the case of
60796—5
66
Spy. All the apples on each tree were taken, 500 in the case of Gravenstein
and 1 ,596 in the case of Spy. By thus providing optimum conditions for pollina-
tion we naturally reduced the production of abnormal apples likely to result from
imperfect fertilization, which undoubtedly affected the results, but gave a value
for the effect of seed content.
Fig. 18. — Studies in premature drop and open "blossom end"
of Gravenstein: (l)-(5) closed "blossom end", no mouldy
core; (6) -(10) open blossom end, mouldy core; (1) 8
seeds; (2) 6 developed and 2 undeveloped seeds; (3) 5
developed and 2 undeveloped seeds; (4) 5 seeds; (6) 1
seed; (7) 3 seeds; (8) 3 seeds; (9) 2 developed and 1
undeveloped seed; (10) no seeds (original).
67
The coefficient of correlation using all seeds, whether filled or not, was, in
the case of Gravenstein -055± -0366, which is not significant; and for Spy,
•3467± -0148, which is statistically just significant. Since results with Graven-
stein are not in line with those obtained by Einset Hoc. cit.) and since the
correlation in the case of Spy is not as great nor as striking as might have
been expected, it was decided to duplicate the work with Gravenstein and Spy
and, in addition, to run similar correlations with King pollinated with Wagener
and Baldwin pollinated with Cox Orange. The following numbers of fruits
examined were: Gravenstein, 1,100; Spy, 1,000; King, 314, and Baldwin, 1,000.
8
Fig.
19.- — Outlines of "blossom end" of Gravenstein apples showing gradation in open
condition (original).
The coefficients of correlation obtained in 1932 are as follows: Gravenstein,
•0025± -0302; King, -1103± -0557; Baldwin, -2723± -0293; Spy, -3069±
•0286. In the Gravenstein, King and Baldwin varieties, no significant correla-
tion was obtained, but in the case of the Spy the result may be considered just
significant.
In order to determine whether chromosome constitution had a bearing on
this phenomenon, another diploid, viz., Wagener was selected and a correlation
calculated on one thousand apples from open pollinated trees. The correlation
obtained was -07304 and -0315, which was not significant. It may be noted
that the average number of seeds obtained for Wagener, viz., 5-58, is no greater
than for Baldwin and certain other triploid varieties.
60796—51
68
\j) MORPHOLOGICAL ABNORMALITIES ASSOCIATED WITH SEED CONTENT
In varieties with a normally high seed content the failure of seed on one side
to develop results in the fruit being flattened on the corresponding side. Deter-
minations of seed content from normal and one-sided apples of the same variety
show a higher average seed content and a correspondingly greater weight in the
former. Varieties in which this condition was commonly observed are: Spy,
Yellow Bellflower and Ben Davis. This type of distortion seems to be somewhat
more common in apples of an elongate form than in those that are more flattened
at the extremities. In certain other varieties, apples with few or no seeds may
be found, which are almost cylindrical in shape. Such was the case with Deacon
Jones, in which type the number of seeds is twenty, the average from mixed
samples being 9-36.
On the other hand, apples with a relatively low average seed content may
show no distortion whatever. In the Wageners examined by us in our studies of
weight in relation to seed content, no one-sided specimens were found. The
same is true of all the triploid varieties studied, viz., King, Baldwin and
Gravenstein.
/m?/arfr
CoxChwye
£i/ssef
/f//7#
J/art
£/e/7few
/kr/afa//?
Fig. 20. — Outline of "blossom end" of standard varieties (original).
69
It has already been noted in preceding sections that few-seeded and even
seedless Gravensteins may be normal in size, weight and outer form. How-
ever, such apples may be characterized by abnormalities at the calyx end, which
result in an open core condition, resulting in the invasion of this region by
saprophytic fungi, producing what is known as " mouldy core." The late
summer drop of Gravenstein, which occurs in some seasons, is also correlated
with this condition. In experiments under tents it was found that trees sup-
plied with a suitable source of cross-fruitful pollen and an adequate force of
insect pollinators gave approximately one half the amount of premature dropped
fruit. Furthermore, along with a higher seed content, effectively pollinated
apples developed a negligible percentage of open calyx end and " mouldy core."
Ineffectively pollinated trees produced fruit with a relatively low seed content
and high percentage of open calyx end and " mouldy core." On the other hand,
the open pollinated trees, where a measure of effective pollination had taken
place, were intermediate in position.
This open blossom-end condition has also been noted in two other varieties,
viz., Boskoop and Bramley Seedling. The average seed content of these varieties
is low, approximating that of Gravenstein. In addition, a single tree of an
unnamed variety, probably a seedling, was discovered in which few apples
containing seeds could be found. On cutting open these apples, practically all
exhibited this condition. The foregoing observations are based mainly upon
preliminary studies made in 1932. No extensive survey of apple varieties to
determine the nature and distribution of the foregoing abnormalities has been
made, and much further research is needed before definite conclusions can be
drawn.
5. SUMMARY, INTER-FRUITFULNESS OF APPLE VARIETIES
(a) POLLEN STUDIES
1. Technique followed in pollen tests: —
(a) All pollen was gathered from nondehisced anthers.
(b) It was matured under ideal artificial conditions.
(c) It was tested in sugar-agar germinative media.
2. The original medium was a 10 per cent cane sugar solution. However, it
was found more effective to use a medium containing 15 per cent cane sugar
and -5 per cent agar.
3. Counts of approximately 1,000 pollen grains were made for each variety.
4. Pollen germination tests were conducted on all available varieties.
5. The results obtained with the different varieties from year to year were
not entirely consistent, but, in considering each year's germination tests, the
effective pollinizers gave consistently higher germination than the ineffective
pollinizers.
6. An exception to the above was Stayman Winesap which, although germ-
inating well proved ineffective as a pollinizer, due to an agglomeration of pollen
grains.
7. All pollen used on the hand pollinated series was tested for effective
germination before use.
(b) TENT STUDIES
1. In tent studies, cages were erected over trees of four varieties, viz., Bald-
win, Gravenstein, King, and Spy, each being subdivided into the following
series: —
1. Tented, with bees and an effective pollinizer.
2. Tented, with bees and an ineffective pollinizer.
3. Tented, with bees and no pollinizer.
70
4. Tented, with no bees and no pollinizer.
5. Tented, with no bees but with effective pollinizer.
6. Check tree, untented and left open pollinated, abundance of pollin-
ating insects being present.
2. The method followed was to place bees and bouquets in required tents,
without emasculation of the blossoms. Results in emasculation tests show that
this method of procedure was warranted.
Se/feaf /7jf.
\A'//7a2/sf°
I Graves7.5/ie//7 2 28%
\3a/aW//7 233%
\/fc//7/as/? 706%
I Cox Orar?ae 7f/f»
\5e/fea '6J7f*
\/<mo 86S7>
Orarens/e//? & 9J%
Go/cSe/7 Xusse/ /2 ZS%
\Spi/ /Z4-*Y.
I Cox Ora/?ae /464
'/g/fc
\/</S7(? 24? 'X
\£a/a*'/r//r 2S/%"
I Crarerts/e/sr -4 ' 97jC
Se/fea'JSO'f*
Crarff/vs/e/s? -403^
3/e/?/?e//7? -40d%
3a/a,/r//?427f<,
Cox Orar??* SOd%
SfcMos/r SS6/0
/099/.
Oo/e/e/7 rfvsse/ '/J 99^
Cox On7s7<?e X4 S8%
fiesr^ar/s /S92%
Fig. 21. — Diagram showing value of different pollens on
standard varieties (original).
3. Bagged limbs used as checks on effectiveness of treatment gave con-
sistent results, which further verifies the foregoing point.
4. The exclusion of pollinating insects reduced the crop produced to an
unprofitable level in all cases.
5. In all cases, the use of an effective pollinizer has given a higher percent-
age fruit than where ineffective pollinizers were used.
6. The introduction of an effective pollinizer in Baldwin, Gravenstein, King
and Spy has given an increase in yields over selfed trees.
7. In the case of Baldwin, a good commercial crop can be obtained by
selfing.
8. Gravenstein and Spy are self-unfruitful, i.e. commercial crops cannot be
obtained through selfing.
9. King is quite self-fruitful, giving in some years satisfactory results through
selfing.
10. Wind pollination within tented trees is practically nil.
(c) HAND POLLINATION STUDIES
1. To secure a large population the limb unit method was followed
2. Emasculation was not practised, but large populations and ext inane care
in pollinating before the anthers had dehisced, more than compensated for the
small population that would have been necessitated had emasculation tech-
nique been practised.
o
series
4
5
71
General results with this series are in agreement with those of the tented
Baldwin and King are self-fruitful, the former to a greater degree.
No one variety was found to be absolutely self-unfruitful. Cox Orange,
Golden Russet, Gravenstein and Spy all exhibited self-fruitfulness to a slight
degree. The former two varieties were superior in this respect to the latter two.
P<ssu//s of£>o///na//o/T
w/tf? D/enhe/m
1930 1931 1932 J928 1923 1930
Percent frv/f Od/a/nea 'ty y&airs
Fig. 22. — Graphs showing value of different pollens on Spy,
Blenheim. Stark and Gravenstein (original).
6. As male parents, the diploids, namely, Cox Orange, Golden Russet and
Spy proved excellent. On the other hand, the triploids, viz., Baldwin, Graven-
stein and King gave uniformly poor results, Gravenstein being superior in this
respect to the other triploids.
7. As female parents, Baldwin, Cox Orange, Gravenstein, King and Spy are
good. Golden Russet's value is of a variable nature, tending to be poor on the
lighter types of soils and good on the heavier.
72
8. The following classification of the standard varieties shows the com-
binations found suitable for interplanting in the Annapolis valley: —
Female Male
Baldwin x Cox Orange or Spy.
Cox Orange x Golden Russet, Mcintosh and Wagener.
Golden Russet x Cox Orange or Mcintosh.
Gravenstein x Cox Orange, Golden Russet, Mcintosh and Wagener
King x Cox Orange, Golden Russet, Mcintosh and Wagener
Spy x Ben Davis and Cox Orange.
Resu/fc of ' Po////?a//o/7
fte$u/te of ' Po////?af/o/? /y///?
f<//?a
6rayes?s/e//7
Cox Orange
— — Oo/aes? ftusser
■ 6raye/75fe//t
*Cox Orange
Oo/o'en Ki/sse/
rv///? 3a/jjv//?
■ Gra ye/75 /<?//?
— ^6o/o/e/7 Kusset
^Cox Orange
- 3a/aW/A
/<//7t?
rfesu/f? 0/ ' Po////7af/o/7
jy/f/7 Cox Orange \
Gra/ensfe/n X/ng
Cox Orange . -Ba/arr//?
1929 1930 1931 193a 1926 1929 1930 1931 1932
Percent fnt/r 06fa//7ect 6y Years
Fig. 23.— Graphs showing value of different pollens on Golden Russet, King, Baldwin ami Cox Oi
(original).
73
6. GENERAL RESULTS AND CONCLUSIONS FROM STUDIES IN
INTER-FRUITFULNESS
(a) Owing to the mixed condition of Nova Scotia orchards the pollination
problem is not as acute as in some fruitgrowing districts. Nevertheless, clear
evidence of unfruitfulness from the practice of (1) planting self-unfruitful varieties-
in blocks, (2) planting cross-unfruitful varieties together or (3) making inade-
quate provision for c^oss-pollination, has been obtained. With the modern
movement to restrict new plantings to a smaller number of commercially desir-
able sorts and to cut down the number of existing varieties by " grafting-out "
operations, a consideration of the pollination situation becomes increasingly
important.
(b) The detailed results of hand pollination tests with standard varieties
are shown in table 8, and the group results for the different types of crosses in
table 9. A study of the results which are based on very large populations, indi-
cates that the pollination problem is, in essence, a simple one.
(c) The value of a variety as a male parent is closely associated with the
chromosome constitution of the variety. All diploid varieties tested gave good
results as male parents for other varieties, whether diploids or triploids, while
triploid varieties gave relatively poor results. When large averages are con-
sidered, there is little significant difference between the different diploids tested,
and, provided there is the proper degree of synchronization between pollen libera-
tion and stigma receptivity in the varieties concerned, all diploids may be
expected, on the basis of these tests, to do about equally well, but triploids
appear to be of unequal, though inferior, value. Exceptions to this general rule
may occur as a result of certain mechanical factors, but the foregoing appears
to be true for the varieties tested by us. Correlated with their production of a.
relatively large percentage of fruit when used as a male parent, a relatively high
percentage pollen germination is characteristic of diploid varieties. On the other
hand, a relatively low pollen germination is characteristic of triploid sorts, but
pollen germination alone does not account for the results secured. They a,re
the result of irregular chromosome distribution, which may show its effect either
in preventing germination or in causing faulty development or abortion later.
(d) On the basis of results obtained with the varieties tested, there would
appear to be little significant difference between the diploid x diploid type of cross
and the triploid x diploid, both being, to a high degree, fruitful. On the other
hand, diploid x triploid and triploid x triploid crosses, excluding Baldwin as a.
female parent owing to possible selfing, are both very unfruitful, the difference
between these two groups in our tests being insignificant.
(e) It is by no means certain, however, that the higher average fruitfulness-
obtained by the triploid x triploid crosses when results from Baldwin are included,
are due to selfing in the latter variety. All triploids, with the exception of Blen-
heim, when used as pollen parents for this variety gave average results superior
to selfing, R. I. Greening conspicuously so. They are also higher than diploid
x triploid crosses which may be due to the triploid x triploid cross allowing;
an opportunity lacking in diploid x triploid crosses for the union of diploid or
near diploid gametes.
(/) Diploid varieties, as female parents, have a consistently higher seed con-
tent than triploid varieties. With diploid varieties the seed content is affected by
the chromosome constitution of the male parent, diploids, as male parents, giving
a consistently higher seed content than triploids.
(g) The value of the different varieties as female parents, or from the stand-
point of selfing, is not so clearly associated with the chromosome number. Fruit-
ful and relatively unfruitful sorts are found among both diploids and triploids.
Self-fruitfulness is found in varying degrees in both groups. Of all the varieties
74
tested, Baldwin is the most self-fruitful. King is fairly self-fruitful, but such
triploid varieties as Gravenstein and Blenheim are, ordinarily, conspicuously self-
unfruitful. The results indicate the variable character of self-fruitfulness from
year to vear and under different conditions.
(h) Not only is the value of the male parents indicated by the seed con-
tent of the female parent upon which their pollen is used, but the percentage
of seedlings resulting when such seed is planted, affords evidence in the same
direction, which is presented in another paper published elsewhere.
(i) No correlation between seed content and weight could be demonstrated
for Gravenstein, King, Baldwin and Wagener. Spy showed a slight correlation.
(;) Malformation of fruit in the form of one-sided or cylindrically-shaped
apples results from imperfect fertilization in certain varieties, chiefly those with
a relatively high average seed content.
{k) In certain other varieties with a low average seed content, a condition
known as " open blossom end " results when the seed content is below normal
as a result of poor pollination. In Gravenstein, imperfect pollination, " open
blossom end " and " mouldy core " were found to be associated.
7. POLLINATION TESTS WITH BLENHEIM AND STARK
(a) THE PROBLEM
Of all the varieties grown in the Annapolis valley, the most frequent com-
plaints of lack of fruitfulness are heard regarding Blenheim and Stark. The
complaint regarding Blenheim comes mainly from Kings county where many
growers report unsatisfactory yields. Attempts to correlate this failure with
cultural or nutritional factors, gave inconclusive results. The type of soil was
thought to have an influence, since in some cases plantings on the same farm
on light and on heavy soil, seemed to favour the latter, but important excep-
tions were noted. The greatest trouble appeared to exist where large blocks
were planted together or where there were indications that cross-unfruitful
varieties might be responsible. In some cases where satisfactory crops were
obtained, it appeared to be generally true that they were mixed with other
varieties, but under very similar conditions other trees did not bear. In one
orchard where Cox Orange had been grafted into the tops of the trees no benefit
resulted.
Many hand pollinations were made on individual limbs on such non-bearing
trees, and in all cases the results were striking and even spectacular where
diploids were used as male parents. In one orchard at Lakeville in 1929, limbs
crossed with Cox Orange gave a percentage fruit of 23, 20, 36, 28 and 21 respec-
tively, as compared with 2-25, 1-09, 0-44 and 0 when selfed, and 1-3, 2-52.
0-55, 0-52 and 2-09 when open pollinated. Many similar results were secured.
From these it would seem that pollination might be a factor, though it did not
appear to be the sole factor in all cases.
Complaints regarding Stark were only less frequent than those regarding
Blenheim and the trouble appeared to be even more widespread. In the case
of Stark the chief complaint was of its erratic and unreliable bearing habits.
As with Blenheim the most trouble came from solid plantings of the variety, or
when it was mixed with triploid sorts. Hand pollination tests with cross-fruitful
varieties gave similar though perhaps, less spectacular results than in the case
of Blenheim. There likewise seemed to be an indication that lack of pollination
might be responsible for at least a great deal of the trouble with this variety.
It was therefore decided to make extensive tests using a large number of
varieties, mainly to determine what were the most effective pollinizers for these
two varieties. The results of 1928-1930, which were obtained by the spur unit
method, were averaged with those of the year 1931, in which the limb unit
method was used.
Fig. 24. — Photographs illustrating results of experimental pollinations:
(1) Blenheim selfed; (2) Blenheim x Wagener; (3) Blenheim x
Stark (original).
76
(6) BLENHEIM
(i) Results of Other Workers. — Little information appears to be available*
regarding this variety. It has been recorded as self-unfruitful by Harper (1921)
and as partially self-fruitful, yielding 0-93 per cent fruit when selfed, by Crane-
and Lawrence (1929). The latter authors classify this variety as a triploid.
(ii) Results of Selfing Tests on Blenheim (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
5,279
124
2-35
49
0-93
The results of selfing tests at Kentville over the 1928-1932 period, show a
percentage " set " of 2-35 and a percentage " fruit " of 0-93, indicating definite
self-unf rait fulness. In 1931, the average per cent " fruit " on the selfed limbs
was 5-23, which is a remarkable increase and further illustrates the fact that
self-fruitfulness is not a fixed character, but varies with the factors affecting
fruit-bud formation, spur vigour, pollen germination, pollen tube growth and
possibly other factors. On the whole, it would appear that this variety is one
of the most self-unfruitful sorts, and good results should not be expected in
ordinary seasons from planting solid blocks of this variety.
(iii) Results of Blenheim as Female Parent (1928-1932).
Total blossoms.
Total set
Per cent set
Total fruit
Per cent fruit
30,255
5,788
1913
2,573
8-50
Our figures represent a very large total of blossoms, viz., 30,255. used in
crossing tests with this variety and with many different male parents. The
majority of these, however, were selected on the basis of their high pollen germ-
ination, as reported by other workers, and uniformly good results might, on
the basis of results of other work, be expected. The foregoing tests, over a
five-year period, gave a percentage "set" of 19-13 and a percentage " fruit ■ "'
of 8-50, which indicates that Blenheim is very fruitful as a female parent, where
effective pollinizers are used. The open pollinated trees (three-year average,
1930-1932) gave a percentage " fruit " of 7-92 for this variety, which show-
clearly that the value indicated may be a little higher than average.
(iv) Result
s of Blenheim as Male Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
Per cent Beeds.
2,808
259
9-22
82
2-92
19-25
Our figures for this variety as a male parent are based only on 2.808 blos-
soms, and confined to tests on Stark. The above tests -how a percentage
" fruit " of 2-92, and " set " of 9-22, which is lower than Stark selfed, indicating
cross-unfruitfulness and may be taken as indicative of its low value as a male
parent, a fact that is substantiated by other tests.
77
(v) Summary of Results of All Varieties on Blenheim (1928-1932)
Male Parent
Baldwin
Ben Davis
Bishop Pippin
Bough Sweet
fox Orange
Crimson Beauty —
Delicious
Duchess
Fallawater
Fameuse
Golden Russet
Gravenstein
Grimes Golden
Hubbardston
Jonathan
King
Mcintosh
Melba
Nonpareil
Ontario
Red Astrachan
R. I. Greening
Ribston
Rome Beauty
Spy
Stark
Stayman Winesap.. .
Wagener
Wealthy
Wellington
Winter Banana
Wolf River
Yellow Transparent
York Imperial
Total
blossoms
371
566
431
101
4,280
220
993
614
375
344
2,000
2,345
323
366
885
2,437
895
634
491
441
637
405
541
127
144
1,900
630
2,783
1,302
326
343
597
1,040
440
Per cent
set
10-78
27-56
33-64
2-97
24-69
15-91
25-28
28-34
6-93
19-48
26-30
10-70
26-32
1612
20-90
4-60
19-66
21-61
6-31
26-30
2418
8-15
9-61
71-65
22-92
4-42
11-75
20 01
15-75
34-66
29-15
29-98
35-48
29-55
Per cent
fruit
It is hardly necessary to point out that where crosses represent a very small
blossom population, irregularities due to limb vigour, pollen germination, etc.,
greatly increase the probability of error in the results.
(vi) Other Data. — As already indicated, data from commercial orchards
and hand pollination tests seem to show that, where effectively pollinated, Blen-
heim is capable of producing good crops, though it would seem that some other
factor must be involved in at least some cases of non-bearing, or that the variety
experiences more difficulty in becoming cross-pollinated than many others. Its
pollen has a low value for crossing purposes and its self-unfruitfulness is most
pronounced. In 1931 it gave a high percentage " fruit " in selfing tests and this
coincided with a heavy yield of Blenheims all over the valley. Many, though
not all, plantings that had yielded poor crops before, gave good yields in 1931.
Nothing could better illustrate the variable character of the factor of self-
fruitfulness.
This point is well illustrated by an experiment conducted at Watervillc.
There was a block of Blenheim that the owner in 1919 decided to graft into
Cox Orange, but only the tops of the trees were completed. The Cox Orange
came into bearing in a few years and bore satisfactory crops, but there was no
benefit to the Blenheims, which continued to bear little or nothing.
In 1931, one of these trees was tented and a hive of bees introduced. The set
of fruit obtained was very high, viz., 13-72 per cent, but the open pollinated trees
yielded 9 • 83 per cent, which is also very high and the difference between the two
is not particularly significant. Any other year the results might have been very
different, and the danger of drawing conclusions from one year's results is thereby
emphasized.
78
An interesting result obtained in this experiment is the low percentage fruit
produced by the Cox Orange limbs inside the tent, as a result of selfing or Blen-
heim crosses, as compared with the much higher percentage fruit on open pol-
linated limbs, where cross-fruitful pollen was evidently available. Table No. 10
gives the results.
TABLE No. 10.— TABLE SHOWING FRUIT, ETC., ON TENTED AND UNTENTED
BLENHEIM— COX ORANGE TREES
Location of station
Variety
Number
blooming
spurs
counted
Average
number
blossoms
per
blooming
spur
Per cent
fruit to
bloom
In tent
In tent
Blenheim
Cox Orange
502
501
720
516
4-85
400
5-18
4-29
13-72
4-71
Outside tent
Blenheim
10-97
Cox Orange. . .
9-83
Note: These trees were Blenheim with top of tree top- worked to Cox Orange.
(vii) General Summary jor Variety. — Blenheim under most conditions is
highly self-unfruitful, but may occasionally give reasonable yields even when
selfed. It is very fruitful as a female parent when pollinated with an effective
pollinizer, but is a particularly poor male parent.
(c) STARK
(i) Results of Other Workers. — Very little information is forthcoming as to
the fruiting habits of Stark. Ballard (1914) reports no set when pollinated with
Red Astrachan in Maryland. As a male parent it is reported to have given 3-5
per cent fruit on Northern Spy, by Marshall, Johnston, et al. (1929) ; no set is
reported as having been obtained when used on Mcintosh in Washington by
Morris (1920) and the same result was obtained by Ballard (1916) on Yellow
Transparent.
(ii) Results
of Selfing Tests
on Stark (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
3,073
280
911
106
3-45
Hand pollination tests at Kentville indicate a degree of self-fruitfulness for
the variety, viz., 9-11 per cent "set" and 3-45 "fruit". However, the latter
figure may not be considered sufficiently high to produce a commercial crop for
this variety, and the planting of solid blocks should be avoided. The open
pollinated trees over a three-year average (1930-1932), gave a percentage fruit
of 7-73, which may be considered a good commercial crop for the variety.
(iii) Results of Stark as a Female Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit Per cent fruit
27,234
9,453
34-71
2154 7-91
Stark, from our results, may be termed a good female parent, a percentage
" set " of 34-71 and " fruit " 7-91 being obtained over a five-year average (1928-
1932). Our figures represent the massed results of some thirty-five male parents
79
Fig. 25. — Photographs illustrating results of experimental pollina-
tions: (1) Stark selfed; (2) Stark x Wagener; (3) Stark x
Gravenstein (original).
80
on this variety, the larger number of which were selected because of their high
pollen germination ability, and a fairly high percentage " fruit " might be
expected. Its value as a female parent in these tests, however, is only slightly
higher than that of the open pollinated trees and indicates that the variety is
fruitful when effectively pollinated.
(iv) Results of Stark as
a Male Parent (1928-1932).
Total blossoms
Total set
Per cent set
Total fruit
Per cent fruit
Per cent seeds
1,900
84
4-42
49
2-58
14-73
As a male parent, Stark has given inferior results, being similar to Blenheim
in this respect. The tests over the five-vear period show a percentage " set " of
4-42 and "fruit "2-58.
(v) Summary of Results of All Varieties on Stark (1928-1932).
Male Parent
Total
blossoms
Per cent
set
Per cent
fruit
Baldwin
603
410
537
2,808
86
2,451
630
672
638
530
414
2,164
2,062
663
241
791
2.547
670
199
407
213
523
337
568
154
229
488
2,221
717
255
383
610
536
477
23-38
59-76
60-71
9-22
10-47
33-66
42-86
70-39
36-36
20 00
53-38
36-88
14-35
41-78
52-28
60-18
22-26
67-31
57-79
23-34
6714
49-33
28-49
19-54
81-82
55-90
7-79
40-84
37-80
59-61
50-91
59-34
504
69-39
4-64
Ben Davis
13 17
Bishop Pippin
6- 15
Blenheim
2-92
8-14
Cox Orange
9-83
Crimson Beauty
9-52
7-89
Duchess
7-84
7-36
Fameuse
8-94
Golden Russet. . . .
11-88
Gravenstein
5-63
Grimes Golden
513
Hubbardston
7 05
Jonathan
8-47
King
6-60
Mcintosh
12-24
Melba
4 • 02
Nonpareil
7-62
Ontario
704
Red Astrachan
10-71
R. I. Greening
7-41
Ribston
8-63
Rome Beauty
714
Spy
10-92
Stayman Winesap
2-46
Wagener
11-35
Wealthy. . .
614
Wellington
10-20
Winter Banana
809
Wolf River
15-25
Yellow Transparent
1-87
York Imperial
8-60
(vi) General Summary for Variety. — Starks are more self-fruitful than
Blenheims, but not to the extent of yielding commercial crops when planted in
solid blocks. They are very fruitful when pollinated with diploids and give a
low percentage " fruit " when used as male parents.
81
TABLE No. 11.— THE FRUITFULNESS OF DIFFERENT TYPES OF BLENHEIM AND
STARK CROSSES (1928-1932)
Total
blossoms
Total
set
Per cent
set
Total
fruit
Per cent
fruit
Seeds*
Cross
Per cent
Average
number
per apple
Bleinheim x Diploids
Blenheim x Triploids
15,141
8,490
6,624
5,279
11,599
9,332
6,303
3,073
3,623
603
1,562
124
5,183
1,565
2,705
280
23-93
7-10
23-58
2-35
44-68
16-77
42-92
9-11
1,689
276
608
49
1,173
499
482
106
1116
3-25
9-18
0-93
1011
5-35
7-64
3-45
36-47
9-31
35 06
2-66
37-18
10-38
23-56
6-80
4-56
3-41
Blenheim x Others
4-47
Blenheim Selfed. . . .
2-73
Stark x Diploids. . . .
4-23
Stark x Triploids
Stark x Others
2-76
3-44
Stark Selfed
2-90
* Seed counts made on basis of actual number of fruit harvested.
{d) GENERAL RESULTS AND CONCLUSIONS
1. The general results obtained by the various tests on Blenheim and Stark
lead to general conclusions similar to those obtained with standard varieties.
The behaviour of the two varieties, both triploids, is very similar. Stark is,
however, more self-fruitful than Blenheim. Both varieties are fruitful when
pollinated by diploid varieties and both give inferior results as male parents
on all varieties tested.
2. Blenheim is ordinarily one of the most self-unfruitful varieties grown in
the Province, giving an average of 0-93 per cent over a five-year period when
self-pollinated. The fact that self-fruitfulness is not a fixed character is, how-
ever, well exemplified in our studies of this variety, which in 1931 gave a per-
centage " fruit" of 5-23 when selfed. Stark gives more uniform results over this
period with an average of 3*45 per cent in selfing tests.
d/e/7/?e/mZ.92%
345%
Oraye/7s/e/s7 S63%
| CoxOras?<?<? S83j£
1 /Yafener //JS/C
| G<?/afe/7#t/sse///.88^
S/ar/: 2.53'/
Grayens/e/s? 3.88£
~ 3a/a</r/f7 5./S^
Warner 8 Od^
Sfc/s7/os/z8./6/{
Y*)fJr)*^fcsl
Cox Orar7$d>/j.69%
Fig. 26.— Effect of various male parents on Stark and Blen-
heim— per cent of fruit after July drop (average for five
years, 1928-32) (original).
3. Both varieties appear to require greater provision for suitable cross-
pollination than most others and this fact must be taken into account in all
new plantings or in grafting-out operations. Furthermore, wherever these varie-
ties occur in mixed plantings the fact that both give very inferior results as
male parents, even to the extent of inhibiting selfing in some cases (see results
of tent experiments), must also be recognized.
60796—6
82
4. Among commercial varieties, the early blossoming sorts such as Wagener
and Golden Russet are excellent pollen parents for both varieties. Cox Orange
gives good results in hand pollinations, but, if depended upon exclusively, it
may be somewhat late in blossoming in some seasons. The value of these male
parents is indicated in the seed counts, as was found to be the case with the
standard varieties.
5. Detailed results are presented in the accompanying table and chart.
8. PLANNING THE ORCHARD
In considering the question of setting out new orchards or grafting our old
ones several points require consideration:
1. The planting of blocks of self-unfruitful varieties, which includes all the
varieties listed by us except Baldwin, should be avoided.
2. The proper admixture of cross-fruitful varieties, of which the bloom
overlaps sufficiently to permit cross-pollination, should be given consideration.
3. If the bloom does not exactly coincide, it is preferable for that of the
variety introduced as a pollinizer to be a little earlier rather than a little later
than that of the variety it is desired to pollinate.
4. The varieties used as pollinizers must themselves be provided with pollin-
izers, as many varieties that produce excellent pollen for crossing purposes are
themselves quite self-unfruitful.
The best supply of pollen is that provided by effective pollinizers planted
at suitable intervals in the orchard. Authorities differ as to how many are
required, some advising at least every fourth tree in every fourth row, others
claiming that a full row of the pollinizer every second or third row is not too
great. It is difficult to give definite recommendations from the evidence avail-
able, especially when the effect of over-pollination is considered, but, from a
study of all the factors involved it would appear that the provision of a full
row every fourth row would represent the minimum provision for pollination
where only diploid varieties such as Golden Russet, Wagener, Cox Orange or
Northern Spy occur in the block concerned. The evidence at hand indicates that
in certain seasons pollination is very local and that, in order to provide against
such conditions, even closer planting than that indicated would be advantageous.
The need for special provision of abundant pollinizers is most acute in the case
of such varieties as Blenheim and Stark, and is of importance wherever triploid
varieties form a large proportion of the planting. Full rows seem to be prefer-
able to scattered trees under these conditions. The habit of bees of working a
limited locality is an important consideration.
The blossoming period of Gravenstein and King, for example, sufficiently
overlaps that of Golden Russet or Wagener to enable the former to be pollinated
by the latter, but neither King nor Gravenstein will give besl results as pollin-
izers for other varieties. Gravenstein, however, is superior to King in this
respect. Golden Russet and Wagener are inter-fruitful, and air sufficiently over-
lapped by Cox Orange to give fairly satisfactory results. Cox Orange i- also an
excellent pollinizer for Baldwin, and Golden Russet also overlap> sufficiently to be
of service, especially to the earlier bloom. Spy presents the greatest problem of
our commercial sorts. Cox Orange overlaps to a sufficient extent in most years
to give a good crop, but in seasons where the bloom is more prolonged Ben
Davis gives better results. However. Ben Davis is no longer recommended for
new plantings. Rome Beauty has given good results elsewhere, but there
appears to be some difference of opinion as to the commercial value of Rome
Beauty in the Valley, owing mainly to the poor growth habits of the tree. In
a season like 1930 when the bloom came and went practicably within a week.
there is not the same problem as regards overlapping of bloom, but in some
seasons the unevenness of bloom of the different varieties constitutes a difficulty.
83
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r96—6i
84
However, Cox Orange can be depended upon to give at least fair results on Spyr
and owing to the fact that this variety blossoms very unevenly, it is suitable for
pollinating a wider range of varieties than almost any other. When the pollen
of Golden Russet or Wagener is dried and properly stored it gives excellent
results on Spy, but under orchard conditions the difference in the blooming period
is too great to make them dependable pollinizers for the latter variety. If
Mcintosh is used, it works well with the medium blooming varieties, including
Golden Russet.
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Fig. 28. — Suggested plan for a five-variety orchard with fillers (original).
For Blenheim, Golden Russet and Wagener provide suitable pollinizers and
Mcintosh works fairly well. Cox Orange, in some seasons, is late for best
results. The same varieties are satisfactory for Stark. In providing pollinizers
for Blenheim and Stark it would seem to be advisable to do so in greater
abundance than for the standard varieties, in order to make pollination more
certain. It is suggested, in setting out poor pollen-producing varieties, that not
more than two rows be placed together, followed by a row or two of a pollinizing
variety, which, in turn, should be followed by one or two rows of a variety
cross-fruitful with the latter. Whether one or two rows would be used would
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Flg. 29. — Possible plan for top-working
solid block of Blenheim to give mini-
mum number of pollinizers. Golden
Russet used to pollinate Blenheim
and Cox Orange to pollinate Golden
Russet (original).
85
depend upon the proportion of each that it is desired to have in the orchard.
Where it is necessary to top-work a block of a self-unfruitful variety, such as
Blenheim, for the purpose of improving the set, every third row should be worked
over, one half with a variety introduced primarily to pollinate Blenheim and
one half with a variety introduced primarily to pollinate the pollinizer of the
Blenheim. In introducing varieties for pollinizing purposes, the most desirable
commercial sorts should be selected.
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Fig. 30. — Suggested plan for a four-variety orchard (orginal).
The accompanying charts showing (1) average blossoming periods of varie-
ties (2) the cross-fruitfulness of varieties and (3) typical combinations of varie-
ties, will illustrate the application of the results of the foregoing investigations..
(jrarensfe.
/V&<?/?er
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Fig. 31.— Chart showing inter-fruitfulness of some standard1
varieties. Arrows indicate direction of cross (original).
Ben Davis is added, though not a recommended variety, because of abundance
in commercial planting and superior results on Northern Spy..
86
9. RELATION OF FRUIT SET ON ENTIRE TREE TO THAT ON
INDIVIDUAL LIMBS OR SPURS
It has already been indicated elsewhere that where the whole tree is exposed
to effective cross-pollination, individually pollinated limbs give lower yields than
when the remainder of the tree is ineffectively pollinated or not pollinated at all.
This is most clearly brought out in tented trees of such self-unfruitful
varieties as Gravenstein and Spy. The figures in the accompanying table show
that, as a rule, the lower the set on the tree, the higher the set on the individual
limb pollinated, and vice versa, though not, of course, in direct proportion.
TABLE No. 12.— EFFECT OF NUTRITIONAL COMPETITION ON TENTED TREES (1928-32)
Variety
Treatment
Whole trees
Per cent Per cent
set fruit
Limb hand
pollinated
with an
effective
pollinizer
Per cent Per cent
set fruit
Gravenstein
King
Baldwin. . . .
Spy
No bees and no bouquets
Bees and effective bouquets
No bees and no bouquets
Bees and effective bouquets
No bees and no bouquets. . . .
Bees and effective bouquets
No bees and no bouquets. . .
Bees and effective bouquets
0-90
21-18
413
30 11
8-23
3111
1-09
49-21
0-67
10-90
103
5-42
3-49
8-17
0-85
10 05
70-66
34-80
37-63
29-28
43 05
45-41
66-90
83-09
4711
18-38
11-87
7-32
19-15
12-69
26-34
18-18
10. OVER-POLLINATION
MacDaniels (1931) has emphasized the factor of over-pollination in con-
nection with biennial bearing. It was noted in our tented series, especially in the
Gravenstein variety, that trees supplied with bees and an effective pollinizer and
yielding heavy crops, failed to give a crop the following year. On the other hand
where blossoming trees were prevented from bearing through lack of insect pol-
linators, there was a strong tendency to bear abnormally large crops the follow-
ing year. In other words, what amounted to defloration took place. Where bees
and ineffective bouquets were used in tented series, and only a small crop resulted,
the trees in the following years tended to approach an annual habit. The above
data tend to indicate that the amount of pollination that occurs in any given
year has an influence on succeeding crops.
Baldwin is the one variety under test that is most outstanding in its bien-
nial bearing habit in the Valley orchards, a high percentage of spurs blossoming
each year. It is also our most self-fruitful variety. It is a well known fact that,
when Baldwin blossoms it, unlike some other varietur, almost invariably fruits.
Pollination of this variety is seldom lacking owing to its self-fruitful habits.
With little cross-pollination, it tends to bear heavy crops, so as usually to require
thinning. This is ordinarily followed by a pronounced " off year ".
At the opposite extreme is the King variety, which, in our tests, rarely gave a
large percentage of fruit from a given number of blossoms. Even where the
original set was heavy, abscission was correspondingly heavy, so that there was
less difference than is ordinarily the case between selfing, good pollinizers and
poor pollinizers. Coincident with this we have the annual bearing habit more
pronounced in this variety in the average Valley orchard.
87
11. TEMPORARY PROVISION OF POLLEN
(a) POLLINIZING BOUQUETS
As a temporary means of supplying suitable pollen, before grafting operations
can become effective, the use of bouquets has been advocated. These consist of
blossoming limbs of the desired varieties placed in tubs of water in the orchard
or hung in the branches. Results from such methods are apt to be disappointing,
as indicated elsewhere. It is difficult to furnish a sufficient mass of bloom to be
effective over the much greater proportion of ineffective pollen present. It also is
difficult to keep such bloom fresh or in good condition, especially in hot dry
weather. Bouquets are ordinarily not as freely visited by bees as the greater
masses of bloom provided by whole trees and, if allowed to wilt, may become
quite unattractive. Furthermore, it is a method that is not generally popular
with growers.
(b) HAND POLLINATION
As an alternative to the temporary use of bouquets, MacDaniels (1930) has
suggested the hand pollination of the orchard. He claims that, hand pollination
of apples when the weather is unfavourable for natural cross-pollination gives
very successful results, the blossoms to be picked just before opening, the un-
opened anthers pulled off and spread on paper trays in a warm room to dry ; the
pollen should then be placed in small unstoppered bottles and applied to the trees
with a camel's hair brush as soon as possible. On a heavy blossoming tree he
states that it would only be necessary to pollinate 20 to 25 per cent of the blos-
soming spurs to get a full crop, nor should all the flowers in a cluster be treated.
With experience it is said that a tree 15 years old capable of bearing 10-15 bushels
can be pollinated in an hour and a half. Another method described is to cut
branches of a good pollinizing variety when pollen is being shed and to brush the
mother trees with these.
(c) THE " BEE POLLEN-COATER "
Yet another method of furnishing a temporary supply of pollen has been
experimented with by Burrell and King (1931) and consists of a device known as
a " pollen-coater ". Its purpose is to force the bees to walk through a quantity
of pollen on entering or leaving the hive.
The bee pollen-coater is a modification of what is known to beekeepers as
a winter hive entrance block. The latter is essentially a diagonal horizontal
tunnel about 6 inches long, 3 inches wide and ^-inch high, attached to the front
of the hive. Its ordinary use is to permit free passage of the bees in and out
of the hive at will, but at the same time, to check air currents that would chill
the colony.
For the present purpose the roof of the tunnel is removed. Two wooden
strips each ^-inch high are nailed across the floor of the tunnel, thus forming an
enclosure to contain the pollen. A glass plate is substituted for the original
roof of the tunnel so that one may observe the bees and determine readily when
the pollen supply needs replenishment. A piece of wood is laid on the glass
plate in sunny weather to prevent excessive heating of the pollen. The workers
referred to above consider that this device holds promise of successfully solving
the problem of pollen distribution in the absence of suitable pollinizers in the
orchard.
(d) USE OF ORCHARD DUSTER WITH BOUQUETS
Still another method has been tried by us with good results during the
season of 1932, and it has much to commend it over either hand pollination or
the use of bouquets. It consisted in placing a bouquet of a cross-fruitful variety
adjacent to the tree to be pollinated, and blowing through it a current of air
from an ordinary orchard duster. The work must be done very thoroughly and
88
the draft directed through the bouquet in all directions. Provided the anthers
are in the proper condition the pollen may be blown right out of the anthers and
results obtained similar to those secured in hand pollinations. The results as
set forth in the accompanying table may be compared with those from the tented
series or with those secured through hand pollinations. The air velocity
obtained at different distances from the outlet is given in another table.
TABLE No. 13.— RESULTS OF TESTS IN FORCED DRAFT POLLINATION, 1932
Variety
Gravenstein
King
Baldwin. . . .
Spy
Total
Total
Per cent
Total
blossoms
set
set
fruit
2,540
95
3-74
86
1,841
399
21-67
132
2,411
472
19-58
242
2,792
340
12 18
198
Per cent
fruit
3-39
7-17
10 04
7-09
The foregoing results indicate clearly that effective pollination can be
effected by this method. In the Gravenstein tent Wagener bouquets were used,
and the increase over that of the selfed tree was three per cent. Wagener
bouquets were again introduced into the King tent and here we find an increase
of four per cent over that of selfing, which is very significant, especially in the
case of such a variety as King. Cox Orange was used as bouquets for the
Baldwin tree and Ben Davis for the Spy, and again a gain of three and two per
cent respectively, over that of corresponding selfed trees was obtained. Its use
from a practical standpoint is questionable, but it certainly offers a means by
which a fruit grower can increase yields, where blocks of self- or cross-unfruit-
ful varieties occur and it requires less detailed work than hand pollination.
It may be noted that the open pollinated trees in the same set of tests,
proved only slightly better in the case of each variety.
Table 13 (a) showing the velocity of the wind inside and outside the
tent is given for purposes of record and because of its bearing on wind pollina-
tion on tented trees. Considerable irregularity is noted, but the difference
between tented and untented trees is very apparent.
The measured air velocity at different distances from the mouth of the pipe
is given in table 14.
89
TABLE No. 13 (a)— COMPARISON OF WIND VELOCITY INSIDE AND OUTSIDE TENT,
WOLFVILLE, N.S.
Wind in feet
Wind in feet
per minute
per minute
Date
Time
Date
Time
In
Outside
In
Outside
tent
tent
tent
tent
Sept. 2
2-30
4-6
179-0
Sept. 7
2-45
22-8
3170
2-35
1-6
42-3
2-50
2-6
497-0
2-40
2-4
253-5
2-55
11-2
950
3-30
0
740
315
140
264-0
3-35
0
15-8
3-20
3-6
1160
3-40
0
42-3
3-25
0-8
179-0
Sept. 5
4-45
0
137-2
3-45
0-4
232-0
4-50
0
950
3-50
10-2
190-0
4-55
0
102-0
3-55
18-8
273-0
5-00
0
1270
415
2-2
157 0
505
0
1270
4-20
0-4
1570
510
0
1790
4-25
1-2
52-8
Sept. 6
9-30
2-8
338-0
4-45
1-4
52-8
9-35
9-6
3170
4-50
0-6
126-8
9-40
0
158-5
4-55
0-6
105-5
9-45
33-6
1900
Sept. 9
200
107-6
410-2
9-50
57-4
433 0
205
800
422-0
9-55
28-6
102-0
210
142-4
455-0
1015
10-8
179-0
3 00
101-8
380-5
10-20
10
214-3
3 05
97-4
296-0
10-25
2-4
296-0
310
800
322-0
2-50
12-4
1790
3-30
170-5
518-0
2-55
250
243-0
3-35
142-0
423-0
300
170
296-0
3-40
184-1
465-0
3-35
490
3170
400
211-6
475-0
3-40
47-4
357-0
4 05
2150
581-0
3-45
43-2
348-0
4-10
201-8
5180
4-35
19-4
264-0
4-30
189-0
496 0
4-40
1-8
116-0
4-35
163-6
538-0
4-45
24-2
158-0
4-40
126-0
581-0
TABLE No. 14.— VELOCITY OF CURRENT FROM ORCHARD DUSTER IN RELATION
TO DISTANCE FROM MOUTH OF PIPE
Distance from mouth of pipe
M.P.H.
Distance from mouth of pipe
M.P.H.
i'
77-86
63-12
48-30
36-42
26-55
21-41
18-41
15-74
13-68
9
11-98
1
10
10-82
2
11
9-85
3
12
904
4. .
13
8-39
5
14
7-81
6
15
7-36
7
16
6-98
8
12. INHIBITING EFFECT OF UNFRUITFUL POLLEN
In some cases, though not in all, there is an indication that pollen from a
cross-unfruitful variety actually inhibits selfing. This may be true even in
varieties that normally give very little fruit when selfed, but more particularly
in a comparatively self-fruitful variety such as Baldwin.
Several examples of the foregoing may be cited. On Gravenstein tented:
trees supplied with bees and bouquets of an ineffective pollinizer, viz., Blenheim,
over a four-year period gave an average percentage " fruit " of 1 • 14, and the
tented selfed Gravenstein trees (bees and no bouquets), gave 2-12 per cent
" fruit " over the same period, in other words an inhibiting effect of nearly 1
per cent. Baldwin, tented trees supplied with bees and ineffective bouquets
(Nonpareil) yielded an average percentage " fruit" of 4-96. The same variety
90
when selfed (i.e. bees and no bouquets) produced 7-77 per cent " fruit," i.e. sl
decrease of nearly three per cent fruit, which means the difference between a
good and a fair commercial crop.
13. VARIATION IN SELF-FRUITFULNESS
(a) SEASONAL
Self-fruitfulness in the apple appears to be influenced by the climatic con-
ditions especially during its period of stigma receptivity. This fact is well estab-
lished in our selfing records throughout the period of our studies. One striking-
example of this variation became evident in 1932. Spy in the tented series
showed an average percentage "fruit" of -93 on selfed trees (i.e. bees and no
bouquets) during the 1929-1931 period, which strongly indicates self-unfruit-
fulness. However, in the season of 1932 the tented selfed tree gave a percentage
" fruit" of 4-84, or in other words, a commercial crop was produced by selfing.
In 1932, the selfed limbs in the hand pollinated tests on Gravenstein showed a
percentage " fruit " of 2-79, this figure being 1-64 per cent higher than the five-
year average. On the other hand selfing tests on Baldwin in 1932 gave a per-
centage " fruit " of 3-01, which was 3-36 per cent less than the five-year average
and a low percentage fruit for such a comparatively self-fruitful variety. In
1930, the latter variety showed a percentage " fruit " of 9*50 on the hand selfed
limbs.
Hand pollination tests in 1932 indicate that King is very self-fruitful, a
percentage "fruit" of 6-11 being obtained. The average for the five-year
period was 3-56. All data cited indicate clearly that there is a wide fluctuation
in self-fruitfulness from year to year, and a true value for any one variety can
only be obtained over a period of years. These differences are usually attributed
to " climate," though it is not always possible to state what particular item or
items in the complex are responsible.
(b) DUE TO TECHNIQUE
Self-fruitfulness in apples varies in relation to the experimental technique
used as is clearly portrayed in the accompanying table. The bagged series
includes the limbs self-pollinated by hand under cheesecloth bags. The tented
series is made up, first, of those limbs self-pollinated by hand under cheesecloth
bags within the tent and, second, of the whole tree, exclusive of the individual
limb, selfed by bees and enclosed in a cheesecloth tent. All varieties when self-
pollinated by bees under tents, showed a higher degree of self-fruitfulness than
where selfed by hand on the same tree. The hand self-pollinated limbs under
cheesecloth bags in the open, gave uniformly higher percentages than those hand
selfed within the tents. On the other hand, selfed limbs under cheesecloth bags
in the open gave, in every variety except King, slightly lower percentages than
those selfed by bees in the tents. In the case of King the percentages were
practically the same.
TABLE NO. 15
Variety
Bagged
series
1928-1932
Selfed
by hand
Tented series,
1929-1932
Selfed
by hand
Selfed
l>v bees
Baldwin. . . .
Gravenstein
King
Spy
6-37
115
3-56
1 33
2-22
0-50
2-55
0-73
3-32
2 00
The necessity of taking into account the technique used by various workers
in considering their results, is very plainly indicated by the foregoing.
IV. FIELD STUDIES IN THE ROLE OF INSECTS IN
APPLE POLLINATION
W. H, BRITTAIN
A. INTRODUCTION
The following studies were conducted as a part of the general investigation
of apple pollination in the Annapolis valley, Nova Scotia. In view of the efforts
that have been and are being expended by various extension organizations with
a view to increasing the use of hive bees as orchard pollinators, and in view of
the absence of any adequate supply of hive bees in the territory concerned, it
seemed advisable to make a careful study, not only of the role of hive bees in
orchard pollination, but also of the native insect fauna to which most of the
pollination that actually takes place must be due. In this connection, it was
thought best to conduct our studies from the comparative standpoint, using the
hive bee as the standard of comparison, since the behaviour of this species has
been much more fully studied. The main object of these studies was to determine
the abundance and distribution of the wild bee fauna, their relative value as
pollinators as compared with hive bees, the necessity or otherwise of supple-
menting their activities by introducing hive bees and the problems connected
therewith. Though considerable information has been accumulated, much still
remains to be accomplished before all the points dealt with are finally elucidated.
Throughout the course of these studies the writer has received continuous
assistance from Mr. J. M. Cameron, not only in carrying out the experimental
work in the field, but in tabulating and analyzing the data secured. Mr. C. B.
Gooderham, who appears as joint author of one section of this report, has con-
tributed invaluable assistance in very many ways. Mr. C. E. Atwood has taken
part in the field studies at various times. Mr. John Leefe also performed useful
service during the season of 1932.
B. GENERAL
The apple depends almost entirely upon insects for pollination. While our
experiments show that a certain amount of pollen may be carried by wind, our
results are in agreement with other workers, who find that wind pollination is
negligible in apple pollination. The fact must not be lost sight of that a suit-
able pollen supply is of equal importance to the work of bees in order to insure
proper pollination, since, without effective pollinizers, the activities of bees would
result only in selfing, or in unfruitful crosses. This fact is emphasized because
it has been the practice of a number of growers, when confronted with a pollina-
tion problem, to endeavour to remedy the situation by introducing bees into the
orchard, disregarding the primary necessity of ensuring a proper pollen supply.
C. INSECTS CONCERNED
1. HISTORICAL
Many workers have studied the role of insects in the pollination of apples
and a great deal of valuable information is available as a result of these studies.
Some of the more recent studies are worthy of consideration at this point. Among
those who have paid attention to the insect visitors of apple bloom, the observa-
tions of Britton and Viereck (1906) are of interest.
91
92
These authors quote several writers who have found that honey bees are the
most important insects engaged in pollinating fruit flowers, but their own find-
ings are to the contrary, as honey bees were exceedingly scarce in comparison
with other insects. Their observations were made at New Haven and Branford,.
where bee hives were less than two miles away, and wild honey bees present..
Two hundred and twenty-nine insects of 52 species were collected from the apple..
These included 9 species of Halictus; 5 species of Andrena) 3 of Trachandrena'y.
4 of Bombus; and Apis mellifica; besides other bees and wasps — in all, 32 species,
of Hymenoptera. Osmia lignaria was the commonest single species, 34 individuals
being collected out of a total of 197 Hymenoptera; 65 Halicitus, 31 Apis, and 28.
Andrena were also taken. Apis was comparatively more abundant on apple-
than on other fruit trees. The authors believe that most Diptera are of no.
importance as pollinators, although a few may be considered beneficial. They
also conclude that on account of their great numbers, the small bees belonging
to the Halictidae and Andrenidae were of far greater importance in pollinating
the flowers of the plants from which they were taken than were the honey bees„
during the seasons of 1905 and 1906.
Rawes and Wilson (1922) have also studied this question and agree with
other workers that wind plays no part in the pollination of apple trees. Insects-
are the only efficient pollinators, and although honey bees are active agents in
carrying pollen, this work may be most efficiently performed by other insects.
Among insects other than hive bees, bumble bees take the foremost place, and!
are not kept from their work by dark weather. Andrena and allied species are-
next. Eristalis, Syrphus and other small flies are considered to play a consider-
able part in apple pollination. In regard to apples and pears, hive bees and flies
are more frequent visitors than wild bees or other insects.
Observations were made by Hooper (1929 and 1931) over several years on
the numbers of various insects visiting apple blossoms, and the numbers added
up. The district contained many cherry, apple and other fruit plantations and
numbers of hive bees were kept. The land not in orchard was either ploughed
land or sheep pasture, not very suitable for pollinating insects. The counts on.
apple were as follows:
Hive bees 374 Beetles 104
Bumble bees 37 Ants 51
Halicti, etc 21 Earwigs 3
Flies 23 Thrips 2
Fox- Wilson (1929) has also made a careful study of this question. This:
author gives a description of Wisley gardens, which are near rough land and
pasture. Various factors besides pollination which affect fruit setting are dis-
cussed. Most common fruit flowers are shown to be entomophilous. In order
to determine the cause of attraction of insects to flowers, some apple blossoms
had the petals removed. Hive bees, Syrphids and Anthomyids, visited these
blossoms. Bumble bees ignored them. Artificial blossoms without nectar
attracted bumble bees, but hive bees ignored them, until nectar was placed in
them. Sight is considered more highly developed in Bombus, smell in Apis.
The various types of pollinating insects were discussed briefly. Honey
bees were considered to be the most efficient because of their industrious habits,
etc. Bumble bees were less deterred by unfavourable weather than hive beesv
and under the conditions occurring in 1920, various wild insects secured a good
crop with no hive bees present. Andrenidae were found very subject to changes
in weather. They showed greatest activity from 11 to 1 p.m. and from 2 to
4 p.m., resting from 1 to 2 p.m. Various other Hymenoptera and Diptera were
mentioned as visitors to fruit blossoms. Gnats of the family Mycetophilidae
were found to surpass all other insect visitors to apple, etc.; but owing to their
small size, are usually overlooked. They carry considerable pollen. Coleoptera.
93
were found of practically no use as pollinators, although frequent visitors. The
number of visitors to apple during a total period of 40 hours, 45 minutes, com-
prising observations in 1920, 1921, 1922, 1923 and 1924 is given as follows:—
Hive bees 222 Other Kvmenoptera 44
Bumble bees 337 Diptera 488
Wild bees 106 Miscellaneous 132
"The author does not state on what quantities of bloom his observations were
:made.
Hutson (1926) quotes the work of various investigators in regard to insects
other than the honey bees concerned in pollination of fruits. Calculations of
insects visiting bloom between 12 noon and 1 p.m. for three years are given in
this paper. These include Chironomidae, Muscidae, Bombidae, Syrphidae and
Scarabaeidae. Honey bees also were found to work differently in different
varieties. There was also a variation from year to year, e.g., 9 per minute in
1923 and 6 in 1924, a variation of from 5 to 90 seconds having been observed
in length of time spent on apple bloom when collecting nectar. The main point
brought out by the collections was the small number of insects found in apples
during bloom. There was a marked difference in the numbers found in the
one orchard surrounded by tilled land and the planting surrounded by over-
grown land, especially in the greater number of bumble bees found in the latter.
A brief discussion of the relative importance of the various groups con-
cerned as determined by our studies follows. Owing to limitations of time,
equipment, personnel, and to constant trouble from poisoning, much of the work
could not be carried out as originally conceived and some of our conclusions
•must be regarded as tentative.
2. HIVE BEES
It may be pointed out at the outset that the question of orchard pollination
by hive bees in the Annapolis valley is at present largely an academic one. Due
to the widespread effect of poisoning from orchard dusts and sprays, which is
■discussed in detail elsewhere, the hive bee population, over square miles of the
main orchard area is practically nil, and this area must depend upon wild forms
for pollination.
In 1931 there was an aggregate of 493 colonies in the whole of Kings
county, distributed among 46 owners. Of these 198 were the property of owners
who practiced migratory beekeeping; 188 were the property of the Experiment
Station and the Pollination Project and used for experimental purposes; and
about 25 were in towns or outside the fruit belt, leaving only about 102 colonies
to pollinate about 30,000 acres of orchard. Obviously the hive bee at the present
time and for several years past has had little influence in fruit pollination in
the area studied.
3. BUMBLE BEES
Bumble bees are a variable quantity. They are more numerous in the
region of the North Mountain, and especially in certain seasons, as in 1930,
were a decided factor in pollination of an orchard at Blomidon, but, in 1931 were
much less numerous. In 1932 there was an apparent increase at some points,
but, taking the area as a whole, they cannot be considered an important factor
in apple pollination. There is considerable testimony to the effect that the
bumble bee population has declined in recent years. Formerly, it is said that
they were common in more or less damp meadows where hand mowing had
to be resorted to, but are now much less frequently found, especially in the
Yalley proper. Whether this is actually the case, and whether, if true, it is
•due to limitation of breeding places, poisoning, or some other factor, cannot now
be determined.
94
The following is a list of the species taken at apple bloom: —
Br emus vagans Smith Br emus fervidus Fab.
" terricola Kirby " ternarius Say
" borealis Kirbv
4. SOLITARY BEES
By far the greatest number of visitors to apple bloom in the area studied
belong to the genera Halictus and Andrena. The following is a partial list of the
species taken: —
Halictus smilacince Robt. Andrena carlini Ckll
" era terus Low " wilkella Kirfcy
" lerouxiiLeP. " cratcegi Robt.
" arcuatus Robt. " rugosa Robt.
" cressoni Robt " milwaukeensis Graen.
" provancheriD.T. " bradleyi Vier.
" pilosus Smith " weedi Vier.
" planatusljov. " miranda Sm.
" /ozwRobt. " vicina Smith
" pectoralis Smith " thaspii Graen.
li coriaceus Smith
" versans Lov.
Of the foregoing the first three species are probably most generally abundant
and of these H. smilacince Robt. far outnumbers all others and is probably more
important in apple pollination in the Annapolis valley than all others combined.
Next to these in numbers observed on bloom would come Andrena carlini Ckll.
and Andrena wilkella Kirby, the latter common everywhere, but particularly so
on Long island.
It has been confidently stated by many writers that modern methods of
culture have reduced the nesting places for bees, which fact is said to account
for their scarcity. It is of interest to examine this statement in the light of the
information gained during this investigation regarding the habits of the species
concerned. All are ground-nesting species, living in tunnels which they dig in the
earth and provision with pellets of pollen mixed with nectar, on which the eggs
are laid and upon which the young feed and develop. In the case of Halicti
studied the males occur in the late summer and autumn and only the fertilized
female winters over. With the Andrena? studied, the males occur in the spring.
The males, however, are of little significance in pollination.
In the case of H. smilacince Robt., the most abundant and widespread of all
the species taken, the holes may be found scattered in various places. Some are
found on exposed surfaces; in other cases the holes arc partly covered with
vegetation. In favoured situations they may be grouped together in considerable
numbers as on roadside banks. They are common along orchard roads if not too
much shaded. They seem to prefer for this purpose a sandy loam containing a
considerable intermixture of silt and clay.
The nests of H. craterus Lov. are found in many different types of situations,
but are particularly abundant in sparsely covered pastures, drier part of dyke
lands, etc. H. lerouxii LeP. nests are also very widespread, but were found in
thousands in the " running dyke " at Grand Pre. The nesting habits of H.
arcuatus Robt. arc particularly interesting. It was found nesting only in one
location, but here it occurred in countless thousands. This community was
found on the steep slope of a pasture on the side of the North Mountain
near Centreville. The soil was classified as sandy loam but contained a con-
siderable intermixture of clay. The site was overgrown with wild grasses, asters,
golden-rods, thistles and other plants common to such situations. These plants
grew largely in clumps, leaving patches of bare ground between and small
95
(» 5b
^%
It- '■'•II
\/8L
o 0
96
boulders up tcKhe size of a football were scattered over and through the ground.
A shovelful of earth from this area might contain scores of adult bees, larvae
and pellets, and on a hot day when activity was at its height the face of the bank
was reminiscent of the front of a bee-hive.
Other species are also associated more or less with a certain type of location.
For example, Andrena wilkella Kirby though widely abundant, is particularly
associated with dvke lands.
Fig. 33.
Running dyke" at Grand Pre. A favourite nesting place of Halictus lerou.rii
LeP. and other bees (original).
Without pursuing this subject further, it may be pointed out that roadside
banks, pastures and dykes do not represent exactly wild conditions, but are the
product of human activity. However, neither are such locations intensively
cultivated. Cultivated land and certain soil types, such as light sand or gravel,
are not suited to nesting, which is one reason that the solitary bees are more
numerous in such places as Long island and along the North Mountain, thai:
they are at many points situated in the middle of the Valley.
The results of a more extensive study of the biology and classification of the
solitary bees concerned in apple pollination, carried out in connection with this
investigation by Mr. C. E. Atwood, will appear elsewhere.
5. FLIES AND OTHER INSECTS
Large numbers of Diptera, particularly Syrphidae, have been taken from
apple bloom, in numbers intermediate between those of solitary bees and bumble
bees, but neither their structure nor habits lend themselves, to the same extent
as bees, for cross-pollination purposes. We are convinced that, outside the two
97
; '...."*.■
HHBr
Fig. 34. — Bank by roadside containing numerous nests of Ealictus smilacinae Robt.
(original).
fi
60796—7
Fig. 35. — Well trodden foot path. Ealictus foxii Robt. was nesting here (original).
Fig. 36.— A past
ith bare patches between tufts of sen
of Halictug craterus Low (original
nesting place
m *
#~
-*)»**
.*§:
r
*a»* y?
e?
JtiRMhtfBW
ated by Halictus arcuatua Robt. (original
99
4
I
W
m
HOT
f
8
^mar
r
.V
10
Fig. 38. — Some species of bees involved in pollina
tion of the apple: (1) Halictus smilacinae Robt.
(2) H. provancheri D.T.; (3) H. arcuntus Robt.
(4) Andrena crataegi Robt.; (5) A. earlini Ckll.
(6) Halictus lerouxii LeP; (7) H. coriaceous
Smith, (8) Andrena wilkella Kirby; (9) Bremus
ternarius Say; (10) Andrena mihvaukeensis
Graen.; ((11) A. vicina Smith; (12) Bremus fer-
vidus Fab. (original).
genera mentioned, other insects play a minor role, and for this reason they have
received little attention in these studies. The following are among the Diptera*
taken on apple bloom: —
Bombylius pygmatus Fab. Syrphus torvus 0. S.
B. major L. Cartosyrphus slossonae Shann.
Eristalis arbustorum L. Sphecomyia vittata Wied.
E. bastardi Macq. Sericomyia militaris Walk.
E. compactus W. Odontomyia interrupta Oliv.
Rhingia nasica Say Hylemya sp.
Melanostoma pictipes Big. Brachyopa perplexa Curran
Syrphus wiedemanni Johns. Pollenia rudis F.
S. rectus 0. S. Mericia ampelus Walk.
S. amalopis O. S. Criorhina badia Walk.
In addition to the foregoing, insects of other families and orders, as noted
by other workers quoted, were also observed by us. Since their practical im-
portance as pollinators of the orchard is quite insignificant, they have, however,
been given no special attention.
* Determined by Mr. C. H. Curran.
60796—71
100
D. RELATIVE VALUE OF INSECT POLLINATORS
1. GENERAL
In view of the situation that exists in the area studied, it was important to
determine whether the wild bee population was adequate to ensure pollination
under all conditions. This involved the working out of a method of determining
the bee population or, at least, the effective pollinating population; and it also
involved a comparison of the various wild bee pollinators with the hive bee with
respect to the various factors affecting their value as pollinators of the apple.
In this connection it was not considered necessary to embark upon a study of
the very complicated problems dealing with the response of the species con-
cerned to colour, odour, form, etc. Since only a single plant species was involved
the problem was considerably simplified, and the limitations of time and expert
assistance precluded any particular attention being given to many lines of work,
which, while of great scientific interest, were not strictly necessary to the main
project. Similar limitations compelled us to lump together all solitary bees under
a single heading and treat them as if they represented a single component. While
it is recognized that differences exist among the species concerned, with respect
to habit and value as apple pollinators, no other course was possible, nor is it
likely that it would have affected the practical results of our studies.
2. METHOD OF STUDY
One of the most important practical difficulties was in devising a ready
method, applicable to work in the field, for estimating what we have called
" effective population," that is, the bee population available for pollinating pur-
poses.
(a) ESTIMATION OF EFFECTIVE POPULATION
In order to estimate the relative numbers of different insects present in the
bloom, a definite plan was adopted and carried out throughout the entire series
of investigations. Workers were stationed at different points in the orchard and
made ten minute counts of the numbers visiting the bloom during that period;
250 blossoms representing the unit of observation. The observations were then
recorded, together with the records of temperature, humidity, wind velocity, sun-
light, etc., prevailing at that time. When studies of distribution were being made,
for example, a certain number of counters were placed at suitable intervals
throughout the orchard and left there throughout the day, while others " scouted "
the outskirts to secure the limits of the flight. (Each counter took up 6 different
points during the hour so as to equalize variations from more or less favourably
situated limbs.) At Kentville one man was kept at this work throughout the
entire blooming period each year, taking observations on different varieties as
they became attractive.
In utilizing the figures obtained in these counts as a basis for calculation, we
determined the average number of blossoms present per acre of bearing trees in
full bloom, by first tagging a representative number of limbs, determining the
percentage that set fruit, securing the total crop obtained and, from this, com-
puting the number of blossoms that must have been present to produce this crop.
From this it was possible to calculate the approximate number of bees per tree
or per acre represented by any count. Thus one bee taken at a single count
would represent approximately 4,000 bees per acre present in an orchard with
trees all in full bloom at one time.
These figures approach accuracy in so far as the stations chosen represent
typical conditions existing throughout the entire orchard. Naturally, it would
be difficult to ensure that the stations chosen were absolutely representative.
but the comparative results for hive and wild bees are based on identical con-
101
102
ditions and should be indicative. Furthermore, the consistency of the results
obtained, when checked by various methods, indicates that in estimating the
effective population the foregoing method is decidedly useful for comparative
purposes and the results should be regarded mainly from this standpoint.
(b) OBSERVATION STATIONS
Observation " stations " from which our studies of bee activity could be
carried out were selected in most cases, with a view to their geographical isola-
tion. Complete isolation could not be obtained, though, in one case, practical
isolation was secured. Most of the orchards were chosen from positions near
the North Mountain, where " coves " running into the mountain offered partial
isolation and at least prevented the bees from flying northward. Nine such
sites were selected, but our main observations were carried out at four of these
stations, with a fifth in 1932. Brief descriptions of these are given, which with
accompanying maps and photographs should give a reasonably clear idea of the
situation of the orchard and the character of the territory concerned.
Station No. 1, Experimental Station.— Including a small adjacent orchard,
there is available here about 70 acres of orchard practically in a block. It is
partially isolated as far as effective bee flight is concerned, from other apple
bloom by ravines, belts of trees, etc., on all sides except the north, where the
bees can fly across the Cornwallis river, to the large orchards on the other side,
distant about a mile. That they actually do this when the bees are placed at
the north of the property adjacent to the post road, has been repeatedly
observed. Until 1931, colonies were distributed through the orchards, about 50
being available, and these were weakened with poison. Instead of being placed
one in a place as in former years, in 1931 and 1932 they were placed in groups
in such a way as to secure optimum distribution, and the number was reduced
to 37.
Station No. 2, Lakeville. — Here the colonies were placed in a solid ten-acre
block of Blenheim, immediately surrounded by orchards, amounting in all to
about 90 acres, about half the area being in orchard within an area enclosed
by a line drawn at one-quarter mile around the orchard on all sides.
Fig. 40. — Map of Long- island district. Total area. 640 acres. Area in orchard. 96 acres.
Figures represent stations at which apiaries are situated: letters indicate intermedi-
ate points at which counters were placed (original).
Station No. 3, Pereaux. — Within a quarter of a mile radius from the colonies
at this station we have 30 acres of orchard in a territory of about 200 acres.
The North Mountain at the back of the orchard prevents flight in this direction.
This orchard is more or less typical of several others used in these investigations.
103
.fflF"7
>-.%"
I X
f
WU
:^J
a
W
104
Fig. 42.— Map of Lakeville district. Total area 223-6 acres; area in orchard 93-7 acres-
scale 4" = 1 mile (original).
Fig. 43.— Map of Pereaux district. Total area 220 acres, area in
orchard 30 acres; scale: 4" = 1 mile (original).
105
Station No. 4, Long Island — This is not now an island being connected with
the mainland by two miles of dyke land, which however, affords little bee
pasturage until the clover flow. It is two miles long and about J mile wide at
the crossroad, bearing about 90 acres of orchard, and with a total area of 640
acres. In 1928, 1929 and 1930 there was available at the east end of the island
an apiary of 25 strong colonies situated just north of the east orchard, with a
belt of trees between it and the beach. In 1931, colonies were placed on the
island at the equivalent of about one per acre divided into three lots, one at
each end and one near the centre. In 1932, these were divided into six equal
lots placed equidistant from each other. The period of apple bloom is normally
several days later than on the mainland and we could never find that, at this
particular period, there was any flight off the island.
Station 5, Somerset. — This orchard was selected for certain studies of inter-
fruitfulness, using bees as pollinators. They were placed in an orchard of
If acres, with an acreage of 44 within a one-quarter mile radius, and 137-72
//ay
//aa mxu/s, ope/7 f/e/a^e/c.
/ 37.72 acre 5 ftear/aa a/vfara'
W///7//7 yz/77/7e raa'/as afap/ary
■44-4/ acres />ear//7& arc/paraf
W/S/7//7 fesn//e raa'/us o/ap/ary.
/■ 72 arc res <?rc/7ara7 tr/rere ap/trrt/
/s S/Sua/ea'.
Fig. 44. — Map of Somerset area (original).
acres enclosed in a half mile radius. Fifty colonies in good condition were placed
in this orchard and counts were made in and around the orchard for the two
days of maximum bloom.
106
107
108
3. RELATIVE ABUNDANCE OF HIVE BEES AND WILD BEES
DURING BLOOM
The following important advantage is claimed for hive bees and may here
be discussed in the light of our own observations and those of other workers.
The hive bee is the only species in which the workers winter over, and hence
more individuals are available for pollination than in the case of wild bees in
which only the queens hibernate.
The fact that only the hive bees over winter their workers is, of course,
true; and in view of the fact that only queens among the wild species hibernate,
the number of individuals sometimes present in the spring is nothing short of
surprising. Various workers, as already noted, have made observations on this
point, but only a few have attempted actually quantitative determinations.
Therefore the results of our own detailed studies on this point are of interest.
Some useful calculations as to the relative abundance of hive bees and wild
bees under known conditions may be based on our work on Long island, Kings
county, N.S. At this station we had an excellent opportunity to make com-
parative studies of the bee population, both of the hive and the wild species.
Owing to the isolation of this area and the fact that it came into bloom a little
later than the mainland, there was apparently no flight off the island. At the
time of apple blossoming there was also available a certain amount of blue-
berry, rhododendron, dandelion, and other wild flowers, though of course apple
predominated.
In 1931 and 1932 when bees were placed on Long island at the rate of one
colony per acre, we obtained an average 10-minute count of 1-94 bees in the
first year and 3-05 in the second. Since, in 1932, there was only about 60 per
cent of the bloom of the previous year, this would indicate little difference in
the effective population, assuming that there would occur a greater concentra-
tion of bees on the smaller number of blossoms. The solitary bees in the same
area were present in greater numbers in 1931, i.e., they were present in the
bloom in greater numbers than a field force released by one strong overwintered
colony of hive bees per acre. In 1932 the number was less, corresponding to
an apparent decrease in the solitary bee fauna from all stations. This observa-
tion may be correlated with a heavy mortality occurring among the solitary
bees in the summer of 1931, apparently due to drowning in the nests following
wet weather. The dry summers of 1928-1931 may have been particularly
favourable for the numerical increase of solitary bees. The average number
of wild bees taken at all stations for all years would indicate an effective popu-
lation equal to that released by a concentration of one hive bee colony per
acre. If our blossom counts truly represent the facts, they would indicate that
about one-third* the field force of the colonies was available for pollination pur-
poses during apple bloom and, if we are to assume that every solitary bee found
is potentially a pollinator, then the " effective " population is even greater, for
not all hive bees carry pollen. Counts of 7,000 bees made during apple bloom
at Ottawa, showed that less than 25 per cent were pollen gatherers and even
if we consider double the number are effective pollinators, these figures would
appear to indicate that under favourable conditions for pollination, the solitary
bee population available during the period under review is sufficient alone to
effect the pollination of the fruit crop.
Records of activity from Ottawa, Ontario, and Abbotsford, Quebec, sup-
plied by Mr. C. B. Gooderham, while based on too small counts to permit of
generalization, indicate that, while hive bees are present in great abundance
owing to the greater prevalence of beekeeping, wild bees, while less numerous,
were present in sufficient force to accomplish pollination under normal conditions.
* Measurements made by C. B. Gooderham at Ottawa on 3 colonies showed 61%, 38% and
48% respectively, as the percentage of the total force going into the fields during apple bloom.
109
The fact should be strongly emphasized that our studies of wild bees have
been carried on for too short a time to enable us definitely to state that they
can always be depended upon to pollinate the orchards in the area studied. It
is of interest, however, to note that over a period of four years our counts of
hive bees from orchards where they were placed in supposedly adequate num-
bers to effect pollination, averaged 2-34 per count; and wild bees 1-42 per count,
which, even allowing a much greater proportion of effective pollinators for the
hive bee than our counts indicate, still leaves a comfortable margin in favour
of the solitary bees so far as mere numbers of pollinators are concerned. That
each solitary bee will pollinate as many blossoms as a hive bee, however, can-
not be definitely stated, but is discussed in another section.
TABLE No. 16— AVERAGE NUMBER OF HIVE AND WILD BEES PER 10-MINUTE COUNT UNDER
CONDITIONS PERMITTING FLIGHT
Locality
1929
1930
1931
1932
Remarks
Hive
Wild*
Hive
Wild
Hive
Wild
Hive
Wild
Long island
Kentville
9-25
1-28
2-75
1-40
1-47
3-51
1-15
2-26
1-66
1-21
1-94
0-77
106
3-01
1-87
1-87
3-05
1-58
1-38
0-14
Hive bee counts not comparable
in different years, due to varying
number of colonies used. In
1931 and 1932 equivalent to one
colony per acre. More effective
distribution in 1932.
Counts omitted first four days and
last two days of bloom in 1931.
Thirty-seven colonies for 70
acres of orchard in 1931 and 1932,
all weakened by poison, especi-
ally in 1931.
Forty colonies placed in a 40-acre
Blenheim orchard in 1931. Only
16 colonies available in 1930.
Fifty colonies placed in a lf-acre
orchard with 137 acres of orchard
available within one half-mile.
5-52
2-83
5-05
1-40
0-66
1-36
of orchard within one quarter
mile. Other bloom scanty.
and one-half acres.
*"Wild" bees refers only to solitary bees, not to bumble bees.
4. ARTIFICIAL INCREASE AND DISTRIBUTION
Another advantage claimed for the hive bee as a pollinator is as follows: —
Hive bees only can be artificially increased and evenly distributed in the
orchards. This is a decided point for the hive bee as an orchard pollinator.
There is no method of artificially increasing the population of wild solitary bees
such as Halicti and Andrenae should their numbers become depleted from any
cause, and, while investigators have succeeded in " domesticating " bumble bees,
no one has ever suggested a method of carrying it out on a commercial scale.
On the other hand, bee colonies can be obtained by rental or purchase and
furnish a ready method of providing orchard pollinators, where observation
indicates a shortage of wild species. Furthermore, they can be so placed as
to secure efficient distribution. In addition they can be moved about at will
as needed.
5. COMPARATIVE EFFECT OF CLIMATIC FACTORS ON WILD AND
HIVE BEES
A number of workers have discussed the general effects of climate, only a
few of which can be noted at this point.
In discussing the effects of temperature on bees, Phillips (1927) points out
that body temperature is the same as or slightly higher than that of the sur-
110
rounding air, though in flight it is considered that it is a few degrees higher.
During the active season bees may remain away from the hive all night, a fact
also noted in our studies.
Studies were made by Hutson (1926) as to the activity of honey bees in
orchards at blossoming time and the factors influencing it, especially with refer-
ence to the effect of hive placing and weather. The factors directly affecting
honey bee flight were said to be (1) temperature, (2) sunlight, (3) moisture and
(4) air movement. Temperature was stated not to have been a large factor in
honeybee flight in these studies. Little influence was exerted by humidity, short
of actual precipitation, which stopped flight. Sunlight was said to favourably
affect flight, but did not urge bees into the air if other conditions were unfavour-
able. Wind proved an important factor in honeybee flight in these studies, little
flight taking place when the wind was above 20 miles per hour. This worker
and most others have given the major part of their attention to the activity of
the hive bee.
According to Phillips (1930) the flight of bees is limited by temperature,
wind and moisture. He states that, at 60° short flights are possible, free flight
taking place at 65° and full flight at 70° F., while some wild bees, especially
bumble bees, fly at a lower temperature. He notes that a wind of 25 miles
per hour stops bee flight, lower velocities greatly retard it. Sunshine is not
necessary for flight, but cloudy weather keeps the bees near the hive by con-
fining them to short flights. He also states that, even in summer, a sudden
shower will reduce the day's flight by 10 per cent or more, while rain or mist
stops flight.
DeOng (1925) gives tables to show that rain stops the flight of honey bees,
even at temperatures of 52° to 70° F., while on clear days the bees work at all
temperatures above 48° F. He believes that these figures probably apply to
all bees.
Marshall, Johnson, et al. (1929) state that bees are most active on bright
warm days, that they do not fly readily at temperatures below 52-56° F.. and
that a wind velocity of 20 miles or more per hour is unfavourable to their
activity. They state that bees prefer to fly against the wind when moving to
the field, and with the wind when returning with their load. Though they may
travel a considerable distance in good weather, their flight is limited to a few
hundred yards during bad weather, according to these workers.
Lundie (1925) in a survey of the total daily exits and returns for the period
of the observations, found that a factor or group of factors can reduce the total
number of possible exits by an amount varying from total prohibition of flight
to a fraction of 1 per cent. A threatening storm, for instance, of but one hour's
duration, reduced the possible flight on one day in the honey flow by 7-41 to
9-67 per cent.
Comparatively few data were obtained by this investigator on the effect
of wind on the flights. On one day, however, a wind velocity of 16 to 21 miles
per hour, during the hours 9 a.m. to 6 p.m., reduced the possible maximum flight
by 28-53 per cent.
Under a particular set of conditions, the temperature at which the day's
flight commences was found to be uniformly near a certain definite temperature;
but this definite temperature is not always the same. In April it was from 12°
to 14° C. and in May from 16° to 18° C. On dull days this temperature was
usually 2° higher. The internal conditions of the colony govern this temperature
somewhat, a strong colony commencing flight at a lower temperature than does
a weak one.
There was a considerable variation in the hour and temperature at which
the peak of the flight in the honey flow occurs. No conclusive evidence has
been obtained that under similar conditions a good honey flow induces the bees
to go out in large numbers at a lower temperature than they would if no nectar
Ill
were available. The temperature at which the flights in the evening began
to slacken was, without exception, from 1° to 9° C. higher than the tempera-
ture at which flight began in the morning. Days which appear to be similar
in every respect, but which show a variation of as much as from 10 to 25 per
cent in their total flights, are found to differ on account of a lower temperature
in the early part of the day.
Observations by Woodrow (1932) during apple bloom, indicate that the
temperature of greatest activity may differ in different types of colonies. Flight
began at lower temperatures and was proportionally much heavier in the lower
temperature ranges from the stronger colonies; but, at the higher temperature
ranges, there was a proportionally heavier flight from the weaker colonies. The
point of greatest activity was reached at 76-78 degrees F. for a colony containing
1-63 pounds of adult bees; at 82-84 degrees F. for an 8-25-pound colony
but there was little significant difference in this colony from 76-78 degrees
upward. Indeed, from 62-64 degrees upward there is considerable overlapping
in the number of workers leaving the hive. For example, the average flight
at this range was 206-25 bees per minute, compared with 202-67 at 78-80
degrees F. This would seem to indicate that the maximum flights should occur
in strong colonies from 60° F. upward, but in weak colonies such flights would
not be expected until over 72° F.
MacDaniels (1930) considers wind velocity the greatest limiting factor of
pollination in western New York. Park (1923) notes that bees make little
progress against a wind of more than 15 miles per hour.
The period of apple bloom occurs at a time of uncertain weather. Low
temperature, rains, cloudy weather, and such conditions are sometimes respon-
sible for low crop yields, through inhibiting the flight of insect pollinators, as
well as creating generally conditions unsuitable for pollination. The following
data collected during apple bloom, represent observations over such a short
period that they should be studied in connection with the supplementary data
obtained during the golden-rod flow later in the season.
(a) TEMPERATURE
With respect to temperature, the following claim has been made on behalf
of the hive bee:
Hive bees work at lower temperatures than do wild solitary bees. It should
be understood that our data relate entirely to bee activity in apple bloom.
Frequently, bees were noticed working on dandelions and other low growing
plants when none could be detected in the trees.
» 3i 52 35 54 S3 56 57 58 59 60 61 62 65 64 65 66 67 66 69 70 71 7E75 74737677T»79808I8E85*48586 87»
Fig. 47. — Relation of hive bee activity in apple bloom to temperature, 1929-1932 (original)
So far as this factor influences activity in apple bloom, the optimum for
both the hive and the wild species, confining the latter term to Halictus and
Andrena and not including bumble bees, on the basis of our observations,
appears to be nearly the same, viz., about 68° F. for wild bees and about 67° F.
for hive bees. It should be noted that in our counts a greater number of observa-
tions were made at the lower ranges of temperature. Hence our averages for
112
these ranges are based on a larger number of counts and this no doubt affected
the point of apparent optimum activity. Had higher temperatures throughout
the bloom been the rule rather than the exception, the point of apparent optimum
activity might have been higher. The results of other workers already noted,
and of supplementary observations made on this point, and presented later in
this report, indicate that this is the case. At the same time it should be borne
in mind that the temperature of greatest activity may be lower early in the sea-
son, as noted by Lundie (1925). Observations made throughout the entire day
indicate that the hive bees begin to work earlier in the morning and usually
persist later in the day.
Above the temperature indicated they worked well up to 80° F., but the
number found at work over 90° F. was insignificant. It should be said, how-
ever, that such high temperatures very seldom occur during apple bloom.
Small numbers were found at work at temperatures as low as 50° F., i.e., actual
orchard temperature, and rarely at lower temperatures; and, with all other
conditions favourable, fair activity was observed at temperatures as low as
57° F. A temperature of 65° F. is usually given as the minimum effective
temperature, but we would be inclined to place this figure somewhat lower, pro-
vided other factors were favourable. With reference to the effect of temperature
on the distance of flight from the colonies, the statement of other workers that
only short flights are made during the lower temperature ranges, as is also the
case with other unfavourable factors, would appear to be well substantiated. At
65° F., however, there appears to be no evidence of flight limitation, and at
70° F. maximum flights are to be expected.
Hive bees do not appear to be as sensitive to slight changes :n temperature as
do many of the wild species, and a larger proportion is found at the
lower temperatures. They also seem to be more erratic in their response to
temperature during their work in the bloom than do the wild species. This is
brought out in the accompanying figure which shows the curve for wild bee
activity more consistent than that for hive bees. This is not believed to be due
entirely to errors in methods of sampling, since the same method was
used for both wild and hive bees. It may be that hive bees are more
sensitive to other influences which modify temperature effects. They appear, for
example, to show a greater tendency to concentrate in locations where bloom is in
a particularly favourable condition. Another factor that appears to make the
temperature response somewhat erratic is the fact that the sudden breaking
away of clouds, clearing up of a fog or similar condition, causes the hive bees
to come out with a rush, thus giving what appear to be abnormally high
counts for those periods. The modifying effect of light conditions is discussed in
the next section. It is clear from these observations that our counts fall off
rapidly as the lower light readings are recorded in the late afternoon, even though
temperature conditions remain constant or recede at a much less rapid rate. In
fact, in some cases we have reductions in numbers of bees even with a tempera-
ture rising to an apparently more favourable point. Our records show an appar-
ent difference in temperature response between morning and afternoon, higher
values being indicated in the morning readings, which indicate that the effect of
each degree of temperature, within a giveD range, is of varying value, depending
on light conditions. Temperature — conditioned by light and modified also by
wind, nectar secretion, pollen availability, colony strength and similar condi-
tions— is a crucial factor in bee activity during apple bloom.
It should be emphasized, therefore, that the response to temperature cannot
be considered apart from light, wind and other factors. Hence, we can only si ate
in a general way what the optimum temperature range for bee activity is. The
temperature at which the highest average number of bees is taken, might be very
different in different localities, different seasons, different times of the same season.
different days, or even different periods of the day. owing to the modifying
113
influence of light, wind and other effects. The peak of the activity curve, there-
fore, represents the largest average number taken at that particular temperature
during apple bloom over a four-year period, but it does not necessarily represent
the true optimum temperature for general bee activity. Also, the apparent
falling off in activity after the peak may be attributed to the comparatively small
number of observations made at the higher temperatures. During golden-rod
flow, which occurred at a time when higher temperatures were the rule, there was
a steady increase in activity up to 84° F., which was the highest observed temper-
ature.
Lundie's (1925) statement that the temperature at which flight begins to
slacken in the afternoon is from 1° to 9° C. higher than that at which flight
begins in the morning, seems, in general, to be substantiated by our figures and is
true for both hive and wild bees. This would appear to be a light effect, as brought
out in another section.
(b) SUNDIGHT AND SOLAR RADIATION
Sunlight is an important factor in influencing the activity of bees, but sur-
light alone will not cause them to work provided the temperature is too low.
An interesting effect of lack of sunlight is noticed on shaded limbs, the blossoms
on which fail to be pollinated to a much greater extent than on limbs exposed
to sunlight. Bees respond to sunlight very rapidly, as can readily be observed in
weather that is partly cloudy. It was noted that counts made, even at optimum
temperatures, showed fewer bees present in hazy weather, even without definite
cloud banks, than when the sky was clear. The rapidity with which bees return
to the bloom following bursts of sunlight is noteworthy.
RELATIVE RESPONSE OF CELL AHD FILTERS
3.26/77.777. RED ~ 2.4-3 )
3. 78 777. 777. GREEN* 401 I CORNING GLASS CO.
3.29/77.777. BLUE ~ 554 \
4.7.1mm. U-V ^9B6J
AND WESTON "PHOTRON/C CELL WITH QUARTZ COVER
Fig. 48.— Relative response of cell and niters of solar radiation apparatus (original)
60796—8
114
The stimulative effect of ultra-violet light on insects has been demonstrated
by a number of workers who have investigated the " colour sense " in this class,
and several of these have used the hive bee in their experiments. This work
has mainly concerned the attraction of different coloured flowers for the insects.
It was thought that something might be learned from studying the distribution
of solar radiation throughout the day in relation to the activity of hive bees and
solitary bees in the bloom, as might be expected from the results of Bertholf
(1931 and 1931a) and others.
Through the kindness of Mr. J. Patterson, Director of the Meteorological
Service of Canada, who provided us with the necessary equipment for this work
and assisted us by means of advice, we were enabled to give this problem some
attention during the period of apple bloom in 1932.
The accompanying figure illustrates the relative response of the cell and
filters, and the following table shows the percentage radiation falling within
the indicated bands, which is effective in producing the galvanometer deflection,
the shunt for which was adjusted to about i of 1 per cent, the filters calibrated
to within 2 per cent:
Filter
Band
Band, per cent
Maximum
per cent at
U- V
2800-3900
6600-7800
6600-7800
3400-4200
3550-4950
4750-6150
6080-7800
110
1-8
1-6
2-5
19-0
70
190
17
3
2
4
32
8
52
3460
U-V
R + U-V
7000
7000
B + U-V
3700
Blue
4600
Green
Red
5100-5400
6250
As the ultra-violet filter had also a transmission band in the red and infra-
red, it was considered desirable to take a reading with both the red and ultra-
violet filters on the instrument, as well as with each of the filters singly. The
ultra-violet radiation was then given by the following formula:
Ultra-violet=U-V— 1 • 14 (R+U-V I .
This constant has been evaluated on the assumption that there is a uniform dis-
tribution of radiation between 6600 and 7800A. As the distribution on any occa-
sion is unknown, this assumption was necessary, but the resulting error would
be small. The combination of blue and ultra-violet filters was also used, as this
isolates a rather narrow band in the vicinity of 3750A.
Half hourly readings were taken on a number of typical days throughout
the bloom and curves drawn to show the distribution of solar radiation throughout
those particular days, together with temperature. Curves have also been plotted
for bee activity, based on average counts over the same period. In order to allow
all values to be placed on a single graph, arbitrary factors have been assigned to
each, as indicated.
Furthermore, in order to facilitate inspection of graphs indicating bee activity,
the ultra-violet and clear values are indicated on a single chart together with
temperature, while the other values art1 placed on another chart. Since all the
observations could' not be taken simultaneously, it was not possible to secure
exact synchronization of the different readings, and certain irregularities, there-
fore, resulted.
It will be seen, however, that there is a general trend upward of bee activity.
corresponding with increasing light values, and a corresponding decrease when
light readings normally fall off in the afternoon; or, from the effects of clouds.
haze or fog, at any time during the day. It will be observed, also, that within
the tempera t urc range of bee activity, light apparently has a more important
influence than slight changes in temperature. It will be observed that the bee
counts fall off' much more rapidly than temperature in many cases. In others
115
they fall off with receding light values at a nearly stationary temperature and,
in still others, there is actually a falling off in activity as light values recede,
even with a slightly rising temperature.
We were unable by this method, however, to secure any clear indication
that any particular wave length had any greater stimulative effect than any
other. In this connection it has been determined by Bertholf (loc. cit.) that the
9.00 KUDO 11.00 12.00 1.00 2.00 300 400 500
Fig. 49. — Distribution of solar radiation, June 3. 1932 (original).
&30 900 930 ia00 1050 1100 1130 K00 12.30 100 1.50 EDO 230 300 330 400 430 5.00 5.50 6.00 630 700 730
Fig. 50. — Distribution of solar radiation, June 4, 1932 (original).
maximum stimulative efficiency for the honey bee in the non-visible or ultra-
violet portion of the spectrum is at 36oOA, and the values for stimulative effi-
ciency fall away rapidly on receding from these values. The greater part of
the response of our ultra-violet filter No. 986 lies in the region of 3450A. The
same applies to the green filter No. 401, where the maximum response is in the
60796— 8J
116
region of 5300A, while the maximum stimulative efficiency of light in the visible
spectrum (though this has only about % the stimulative effect of the ultra-
violet) is at 5530A. Even though it were possible to isolate narrower bands
in the region of maximum stimulative efficiency by means of this apparatus,
it is not certain that we would secure any further information in regard to this
particular point, because of the tendency for all readings to follow the same
general trend throughout the day. Without an automatic recording device for
light values and bee numbers, the difficulty of properly synchronizing the two sets
of observations is difficult to overcome.
4.30
5.50 6.50 750 8.50 9.50 10.50 11.50 IE30
Fig. 51. — Distribution of solar radiation, June 5, 1932 (original).
10
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Fig. 52. — Bee activity in relation to temperature and light (original),
117
With respect to the differential response of hive bees and solitary bees it is
again difficult to make comparisons, especially as there are unequal numbers
of each available. There is a definite indication, however, based on numerous
individual observations, that hive bees actually do work more readily at lower
light values than do the solitary bees taken as a group.
(c) WIND
Wind is an important factor in governing the activity of bees, as indicated
by the observations of other workers already quoted. Winds likewise limit the
length of flight of bees in the same way as unfavourable temperature conditions,
so that they will be found nearer the hives in sheltered areas during such periods.
In our counts, the maximum wind velocity recorded up to and including 1931
was only 13 miles per hour, and even at this velocity there was considerable
activity. The observation was made, however, that on the eastern end of Long
island, where belts of wood at the north of the colonies sheltered them from
the open basin, the bees worked in greatest numbers.
i
K£-V
/five Se. ?s
/Y//o/3ees-
/V//7t/Kf/0C//t/ //? /77//<?S
SS t 65"
13 2 2.5 3 3.5 4 45 5
7 75 6 8.5 9 95 10 10.5 I 11.5 12 125
Fig. 53. — Bee activity in relation to wind velocity
(original).
It would appear, however, that in the average year during the period of
apple bloom and in the situations where the observations were made, wind was
not as important an inhibiting factor as reported from certain other areas. In
1932, however, apparent cases of flight inhibition due to wind were observed.
A tabulation of the numbers taken at the different wind velocities was made,
which, allowing for the usual large number of apparent irregularities resulting
from errors in sampling, and from the widely different number of observations
at different velocities, seems to indicate a decided influence for even very low
velocities. This can best be observed by reference to the preceding graph which
has been smoothed by the method of moving averages.
There is no indication of interference with flight in the case of hive bees
up to 1 m.p.h. and for wild bees up to 3 m.p.h., after which the counts began
to fall off. From the foregoing it would seem that, in locations where high
winds are frequent, this factor may be of the utmost importance in pollination,
but our own records are inadequate to allow of any more definite statement.
118
Our records would also seem to show that wild bees during the same period
appeared to be somewhat less profoundly affected by changes in wind velocity
than are the hive bees. The number of observations taken, however, are insuffi-
cient to enable us to state with certainty that this is the case.
(d) HUMIDITY
Humidity, short of actual rainfall which checks flight, is generally regarded
as having little influence on bee activity. Bees have been noted gathering
moisture from a nearby spruce hedge during a light rain and, in one case, bees
in front of a large apiary composed of particularly strong colonies were noted
working on rhododendron bloom during a drizzling rain at a temperature of
60° F., but no bees were noted on trees or from weak colonies under such
conditions. Water collectors appear to come out on their short flight even
during a light rain and during intervals between rains, when other bees remain
in the hive, and this has been observed to be a factor in poisoning, such bees
gathering poisoned water from leaves on sprayed trees or from herbage growing
in sprayed orchards.
The numbers of bees taken at the different relative humidities experienced
during the course of these investigations have been tabulated and studied with-
out our being able to detect any direct effect of relative humidity on activity
of either hive or wild bees, up to the point of actual precipitation.
(e) INFLUENCE OF TIME OF DAY
The curve of activity throughout the day is of interest because it represents
the combined effects of temperature, light, and possibly other factors such as
__80_3.
__70_2
■KE-Y"
///re Sees
M/af -
_ 7e/7?pera/£/rb /="_
— //um/a///y .
— 3P-
//our o/ flat/
%- J>600- 6.30- 700- 730- d&O- 850- 900- 950- 10.00- 1130- II 00- 11.30- 12 00- 1230- 1.00- 130- 2 00- 2.50" 300- 330- 4.00- 43(1- 5.00- 530-
^ ^630 700 730 fiOO ft30 900 930 10.00 1030 MOO 11.30 12.00 1230 100 1.30 2.00 230 500 330 400 430 5.00 550 600
If
IN
Fig. 54. — Average bee activity at different diurnal periods in connection with humidity
and temperature, 1929-32 (original).
the possible exhaustion of nectar and pollen supplies. As indicated in the fore-
going chart (smoothed by the method of moving averages), it will be seen that
this follows a fairly regular curve reaching a maximum for hive bees at 12-12.30
p.m. and for solitary bees at 11-11.30 a.m. Temperature and humidity have
been shown for comparison.
119
TABLE NO. 17.— TABLE SHOWING AVERAGE BEE ACTIVITY AT DIFFERENT DIURN\L
PERIODS IN CONNECTION WITH TEMPERATURE AND HUMIDITY*
HiV€
bees
Wild bees
Temperature
Humidity
Time
Average
number
Number
of obser-
vations
Average
number
Number
of obser-
vations
Average
Number
of obser-
vations
Average
Number
of obser-
vations
6 00-6 30
0
0-4
0-23
0-55
1-29
2-34
2-27
2-35
2-70
2-69
2-47
3-46
300
1-43
3-01
2-27
1-84
1-95
1-42
1-95
1-94
1-89
1-65
1-67
0
16
15
22
11
102
163
227
218
252
220
244
161
10
23
213
255
279
237
293
212
223
151
96
6
2
0
0
005
009
0-40
106
1-37
1-50
1-84
1-47
1-61
1-58
4-60
1-91
161
1-47
1-30
1-56
1-20
113
0-93
0-74
0-60
0
0
16
15
22
11
102
163
227
218
252
220
244
161
10
23
213
255
279
237
293
212
223
151
96
6
2
54-5
61-75
60-2
61-0
59-24
59-81
63-96
62-73
65-44
64-28
66-31
66-27
63-38
72-3
68-56
67-74
68-13
67-20
67-38
66-83
65 02
63-63
65-79
60-67
73-0
4
4
9
1
37
3 J
52
45
59
46
58
33
8
10
57
54
76
56
77
53
64
41
24
3
1
6o-5
69-0
62-0
550
61-24
62-08
59-0
60-3
59-96
62-08
60-76
63-81
61-14
51-5
54-98
59-67
58-30
58-16
57-58
58-65
58-72
62 12
60-84
67-0
420
2
6 30-7 00...
3
7 00-7.30
7
7 30-8.00
2
8 00-8.30
34
8 30-9.00
26
9 00-9.30
45
9 30-10.00
40
10.00-10.30
10.30-11.00
11.00-11.30
11.30-12.00
12.00-12.30
12 30-1.00
50
40
49
32
7
4
1 00-1.30
46
1 30-2 00
45
2 00-2 30
66
2.30-3.00
51
3 00-3.30
67
3 30-4.00
49
4 00-4.30
61
4 30-5 00...
42
5.00-5.30
25
5.30-6.00
3
6.00-6.30
1
*Actual figures.
Supplementary data on the influence of the various climatic factors are pre-
sented in the following pages by Mr. J. M. Cameron, following which a sum-
mary of the general effect of these factors is given.
(/) SUPPLEMENTARY DATA ON CLIMATIC FACTORS
(J. M. Cameron)
(i) General. — Desiring to obtain further information with regard to the
effect of climatic factors on bees at periods other than apple bloom, further
data were secured in August and September during the period of maximum
golden-rod bloom, many other flowers such as fall dandelion, Canada thistle,
fireweed, buckwheat, white clover, etc., being also available. Instead of attempt-
ing to count visitors to the flowers, however, as was done during apple bloom (1)
the bees were trapped for short periods after the manner described by Farrar
(1931); (2) counts were made using a photoelectric apparatus; (3) a tripping
device was used to register and record automatically the insects leaving the
hive. By following the latter two methods we did not, of course, secure counts
from the entire hive, but only for a small area in the centre of the brood chamber.
It would have been preferable to have securrd counts for the entire colony,
but, as the necessary apparatus was not available, it wras considered that the
figures obtained in this way would indicate the comparative activity through-
out the day, as influenced by various climatic factors. After experimenting
with the other methods, the photoelectric device was retained as giving the most
satisfactory and accurate results.
Mr. J. S. Leefe assisted in taking all the records and in compiling the data
obtained.
(ii) Apparatus and Its Manipulation. — Figures 1, 2 and 3 show the essen-
tial details of the counting device. Figure 1 is a diagram of the wiring system
120
used. There are four different circuits in the hook-up. The primary circuit is
that of the photron cell. This is connected with a Weston Model 30 relay
(fig. 1, C). As the bee passes through the tunnel (fig. 2, K) it interrupts the
light beam passing through the slits Q and R and falls on the cell B. This
interruption varies the potential in the circuit and operates relay C. Operation
of this relay causes completion of the secondary circuit, a 4^-volt direct current
supplied by three dry cells (fig. 1, H). This current in turn operates a second
relay (fig. 1, D), which acts as a switch in the 110-volt alternating current
line, and operates the counter (fig. 1, E). The fourth circuit has an eight- volt,
alternating current obtained through a transformer from the 110-volt line. This
supplies the power to a 32 candle-power bulb, such as is used in the ordinary
automobile headlight.
Fig. 55. — Diagram of photo-electric bee counter. (A) 8-volt, 32-candle power bulb; (B)
Weston photron cell; (C) Weston model 30 relay; (D) secondary relay; (E) elec-
trical counter; (F) transformer; (G) knife switch; (H) battery of three dry cells:
(I) cone-shaped lamp box; (J) Abbe condenser; (K) tunnel (exit) ; (L) tunnel
(entrance); (M) landing board; (N) bracket supporting light; (0) adjustable bracket
for light socket; (P) concave mirror; (Q) slit in roof of tunnel; (R) cover slip over
hole in floor of tunnel; (S) celluloid trap door at mouth of tunnel (original).
Figures 2 and 3 show the essential details of the hive unit. Figure 3 is a
front view, and figure 2, a cross-section. The landing board is cut off flush with
the inner face of the front of the hive, and the unit substituted. The entrance
is divided into a number of tunnels about three-eighths of an inch square, and
approximately three inches long. These are closed at alternate ends by a
trap-door, so that passage is possible in only one direction. The material used for
the trap was ordinary photographic film hung on two narrow hinges of cello-
phane. These hinges had to be renewed quite frequently, as the bees often
gnawed them off. The light was enclosed in a cone-shaped guard directly over
121
a slit through one of the exit tunnels, and the centre of the photoelectric cell
was placed immediately beneath. This arrangement did not provide a suffi-
ciently strong light to actuate the cell, so an Abbe condenser from a compound
microscope was inserted in the beam to concentrate it. This made a great
improvement, and the addition of a concave mirror above the bulb gave a
sufficiently strong light on the cell to cause very rapid reactions. The instru-
ment as built was quite crude, and by adding refinements, such as the use of a
point-light bulb, could be greatly improved.
To operate the instrument, the hive unit was placed on the front of the
hive, making it necessary for the bees to enter and leave through the tunnels.
The counter was then plugged into the 110-volt current, causing the light to
come on, and the knife-switch (fig. 1, G) was closed. This prepared all the
circuits, and each time a bee passed out through the tunnel, interrupting the
light beam, it was recorded by the counter. Records were taken every quarter
hour, and the counter set back to zero.
Light intensity records were taken by means of a photoelectric solar radia-
tion instrument already described. Wind velocities were obtained by the use
of a cup type anemometer, and temperatures and humidities by thermographs
and hygrographs respectively.
(iii) Temperature. — Exits were recorded at the lowest temperature obtained,
viz., 52° F. While fairly high counts were obtained between this and 60° F., it
is believed that these represent mainly " play flights/' as the bees, in many
cases, did not leave the immediate vicinity of the hive. Little increase in flight
activity was observed until a temperature of 62° F. was reached. From this
point until the highest recorded temperature, viz., 84° F., was reached, flight
activity showed a steady and almost uniform increase.
Fig. 56. — Bee activity in relation to temperature during golden-rod honey flow (original).
That the effect of temperature is modified by other factors is clearly
brought out by the fact that activity is higher at practically all recorded tem-
peratures in the morning than in the afternoon. Few " work flights " occurred
in the afternoon below 68° F., and from this temperature to 58° F. activity
remained practically constant and consisted mainly of " play flights." From
58° F. to 56° F. recorded flights dropped rapidly to zero (fig. 60).
(iv) Light. — Within the range of conditions permitting free flight, light is
the most important factor influencing activity. It is very noticeable that if, on
a bright day, a cloud suddenly obscures the sun, outgoing flight immediately
drops, while the bees wThich are out return in large numbers almost at once.
This observation was made on several occasions, but unfortunately we had no
means of measuring such inward flight.
122
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Flight after about 2.30 p.m. drops off with increasing rapidity. Our counts
obtained after about 4 to 5 p.m. cannot be taken as indicative of the actual
activity of the colony, as observation seemed to indicate that the flights taking
place at this time were largely what are known as " play flights." For the
same reason early morning flights, up until about eight o'clock, cannot be taken
as indicating working activity. From this standpoint the method of counting
bees visiting blossoms, as was done during apple bloom, is a more accurate
criterion of field activity than counting the bees as they leave the hive.
The curve of average flight throughout the day, as shown in the chart, fol-
lows more closely the changes in light values, and particularly the ultra-violet,
than those in temperature. This fact was borne out by calculating simple cor-
relations of the average temperature, intensity of clear light and intensity of ultra-
violet light, with number of bees, at different periods throughout the day. The
correlations were found to be: for temperature, 0-6686± 0-0520; for intensity
of clear light, 0-8429±0-0305; and for intensity of ultra-violet light, 0-9156dt
0-0141. From these results it would appear that ultra-violet light intensity is
the most important factor influencing the trend of flight throughout the day.
That all three conditions acting together probably decide the content of activity
is shown by the multiple correlation of 0-9332 which was found to exist.
The importance of ultra-violet light is further shown by the beta-values
calculated. These were, for ultra-violet light, clear light and temperature,
1-2972, — -1709 and —-2584, respectively. Of these, only the value for ultra-
violet is significant. The other values are negative and unimportant. This
indicates that the high, positive, simple correlation obtained for these two factors
was due to their being so closely associated with ultra-violet.
There is considerable variation in individual observations, and these do
not show as close correlation as is found in the averages. Individual counts seem
to be somewhat more dependent on temperature than on light, the simple cor-
relations of temperature, clear light and ultra-violet light with activity being
0-6179 ± -0203, 0-5003 ± -0245, and 0-5346 ± -0263, respectively. The
multiple correlation of these factors, using the 415 observations made, was
found to be 0-6517. The beta-values in this case show temperature to be the
most important factor. Ultra-violet light is also a highly significant factor,
while clear light has a significant bearing on activity, but is not as important
as are the other factors mentioned.
Taken at their face value, the above results indicate that the average trend
of flight throughout the day is more dependent on the intensity of ultra-violet
light than on the other factors studied; while any individual count of flight is
influenced to a greater degree by temperature. This last condition is probably
due to the circumstance that there is a threshold temperature, below which
flight will not take place no matter how favorable the light conditions, while
above this temperature, even with the light intensities registering practically
nil, there is nearly always some flight. The relative unimportance of the clear
light factor is hard to understand.
In order to determine further the importance of light in influencing bee
activity, records were taken during the partial (93%) solar eclipse of August
31, 1932. Conditions for observation at this time were practically perfect.
After the first few observations there was a dead calm. With the exception of
one period of about ten minutes no clouds interfered with the light conditions
and the maximum drop in temperature was seven degrees F. A glance at the
accompanying graph will show the close relation between the light intensities
and the bee activity. While the lowest bee count was obtained at the period
of lowest temperature, the fact that temperature was not of prime importance
is shown when it is remembered that the counts obtained, viz., eight bees, was
only a mere fraction of the average count obtained at this temperature.
124
500 510
Fig. 58. — Distribution of green, red and blue during partial solar eclipse, August 31, 1932
(original) .
The rise in activity as the sun again came into view was not as regular as
the decrease, partly due to the fact that it was quite late in the afternoon, when
flight normally falls off fairly rapidly and tends to become more irregular.
310 3?0 330 340 350 40 410 420' 430 440 450 5M 311
Fig. 59/ — Solar radiation in relation to bee activity during partial solar eclipse,
August 31, 1932 (original).
(v) Wind. — No wind velocities exceeding 4-4 miles per hour were obtained
and owing to varying light and temperature conditions it is impossible to draw
definite conclusions as to the effect of this factor on activity.
(vi) Humidity. — A study of the data revealed little direct connection between
bee activity, as measured in flights from the hive, and varying degrees of relative
humidity. While it has generally been stated that actual precipitation com-
125
pletely stops all flight, on numerous occasions flight was noted during light rains.
This activity represented mainly " play flights " and flights of water carriers.
(vii) Activity Throughout the Day. — The combined effects of the different
factors already discussed are indicated in the trend of flight activity throughout
the day, as will be seen by a glance at fig. 57. The figures for periods earlier
than 8.30 a.m. have only limited value, since they represent the records of two
days only.
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Fig. 60. — Comparison of flight of bees in morning and afternoon (original)
6. NUMBER OF VISITS OF HIVE AND WILD BEES
There is a considerable amount of scattered observation available as to
the number of trips made by bees and the number of individual visJts to blossoms
made in a given time. Most of these observations relate to hive bees. It seems
very difficult, however, to arrive at any average figure on the basis of these data
or on those secured during the course of our own observations.
Lundie (1925) has observed that the morning and evening flights are very
much shorter than those that take place in the main period of the day's flight, a
variation of from 15 minutes to as much as 1 hour and 43 minutes occurring in
one day. Taking all the days for which the average duration of the trips was
determined, it is found that this duration varies from 8 minutes to as much as
1 hour and 54 minutes. In the honey flow the trips are much shorter than they
are in a dearth. On the day on which maximum flight occurred it was found that
20-74 trips per bee was the largest possible number that could be made provided
each bee entered and left the hive immediately ; while the figures available seemed
to show that even in a heavy honey flow the bees spent more time in the hive
between trips than they did on the trip itself.
Parks (1928) found that one hour was ample time for a nectar carrier, and,
under favourable conditions, ten trips a day was considered a fair average.
Round trips for pollen may be made in 15 minutes or less, but no conclusion is
reached as to the number of trips per day. Water carriers can make a round
trip in 5 minutes and may make 100 trips per day.
Dyce (1927) states that the average number of blossoms visited by a colony
of bees in a single day is around 21,600,000 or the total number of blossoms on
126
20 acres if all are in bloom at once. A low estimate of the average number of
blossoms visited by a single bee in a day is about 720. McCulloch (1914)
records observations in which one bee was observed visiting 61 blossoms, another
53 and several 25 to 40, and many similar observations have been made by us.
If a pollen carrier made only ten trips a day, which, on the basis of Park's
figures would mean 2\ hours in the field, it would only have to visit 72 blossoms
on each trip in order to attain the figure mentioned by Dyce (loc. cit.). The
figures given, however, would seem to indicate a field force of 30,000 bees which
is considerably stronger than the average colonies obtained by us at this time
of year. Moreover, allowance would again have to be made for the proportion
of bees not carrying pollen.
On the other hand, not all, and probably not more than half the blossoms
on mixed plantings are available in the proper condition for the bees at any one
time. If we reduce the field force indicated above by one half and consider
that only 25 per cent carry pollen, this would give us an effective force of
3,750 per colony. If each of these pollinated a total of 720 blossoms throughout
the entire bloom, it would mean the pollination of 2,700,000 blossoms or the
total blossoms on 2-7 acres. Provided that an adequate supply of effective
pollen is available, and even allowing for the maximum number of duplicate
visits, it would seem, on the most conservative estimate, that the force liberated
by a single colony of bees, should be capable of visiting a sufficient proportion
of the bloom to pollinate effectively several acres of orchard, the exact amount
depending upon the duration of favourable flight conditions. It should be noted
that only a small proportion of the bloom needs to be pollinated, which gives a
wide margin for failures to be visited, for ineffective pollinations and for duplicate
visits.
When we come to the question of bumble bees, still less information is avail-
able; though a number of workers have noted that these work more rapidly and
cover more blossoms in a given time than do hive bees, a fact which our own
observations substantiate. Owing to the small size and rapid movements of
our chief pollinator, Halictus smilacince Robt., however, it was not possible to
secure any data of sufficient accuracy to be worthy of record. Hive bees and
bumble bees will sometimes be observed following a limb and covering a large
percentage of the blossoms before passing on to another, whereas the solitary
bees seem to be less consistent in their movements. Though we have no reliable
data as to the mixtures of blossoms individual solitary bees may visit in a
given period, the observations made in another section, with respect to the
actual number present in the bloom, gives useful information as to the relative
value of hive and solitary bees.
7. POLLEN GATHERING HABITS
Certain pollen gathering habits may affect the evaluation of hive and wild
bees as orchard pollinators. The division of labour among worker bees into
pollen carriers, nectar carriers, etc., means that the force available for pollina-
tion is reduced in proportion to the numbers devoted to their special tasks.
Nectar carriers may carry little pollen and certainly have less value for this
purpose than pollen gatherers. They have been observed on many visit- to
insert their mouth parts into the nectaries from the side, without covering the
blossom in such a way as to insure pollination. The relative number of bees
which collect pollen and those which collect nectar is. therefore, of considerable
importance in connection with this study. Some plants are visited entirely
for pollen, some for nectar and some for both pollen and nectar. According to
Parker (1926) when a bee is collecting from a purely pollen plant it carries
honey to moisten the pollen and, when gathering from a plant that produces
both nectar and pollen it invariably obtains nectar from the plant with which
127
to moisten the pollen. In our work it was found that on some days collections
from apple bloom showed a comparatively high percentage of nectar carriers
and, on others, a much lower percentage. Studies in nectar secretion showed
that during some days in which there was a certain amount of activity of bees,
the nectaries were empty or nearly so, and all bees present were gathering pollen.
It was, therefore, very difficult to arrive at any average percentage of pollen and
nectar collectors for the blossoming period. In regard to this problem Simmins
(1904) states as follows:
" It is but seldom a bee gathers a large load of both pollen and honey on
one and the same journey. A pollen gatherer will have little honey, while
those carrying the most honey will seldom stay for a particle of pollen, more
than what may be brushed into honey as collected. The pellets are brought in
most freely up to 11 a.m. while everything is moist from the dew of night; or
at any time, immediately after a shower, if warm. The honey sources of the
day are about dried up by three p.m. and the bees do not often work actively
after that time. As in the early morning, they then carry in much water to
FlG. 61. — Some pollinators of the apple showing method of carrying pollen. (1) Halictus
smilacinae Robt.; (2) Halictus craterus Lov.; (3) Halictus coriaceous Smith; (4)
Temnostroma veuustum Will. — Syrphidae — (original ) .
128
help in preparing the food for the young." Filmer (1932) finds great irregu-
larity in the proportional number of pollen carriers during fruit bloom, which
bears no relation to the total field force, the average percentage for six 3-pound,
overwintered colonies being 39-6; for four 3-pound packages established on
drawn comb 24-7, and for four 3-pound packages established on foundation
15-7.
Parker (loc.cit.) in studies of a number of selected plants records a count
of 45 hive bees collecting pollen only, 24 collecting both pollen and nectar and
Fig. 62. — Hive and bumble bees showing characteristic methods of carrying pollen: i I) Apis
mellifica L.. showing pollen attached to hairs of body; (2) Apis mellifica L... with pollen
baskets full; (3) Bremus temarius Say. showing pollen attached to hairs of body:
(4) Bremus ferritins Fab., with pollen baskets full (original).
129
31 collecting nectar only, on western crab apple. On apple this count was 22-9
and 69 respectively.
During the period of apple bloom at Ottawa in 1932, Mr. A. H. W. Birch,
of the Division of Apiculture, made observations on approximately 7,000 bees
entering the hives, of which only 23-57 per cent were pollen gatherers. Full
,:\
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Fig. 63. — Pollen mixtures from bees: (1) Apis mellifica L. from
Pyrus malus L., pollen P. mains and Taraxacum; (2) A.
mellifica L. from P. malus L., pollen P. malus L. and Cara-
gana; (3) A. mellifica L. from P. malus L., pollen P. malus L.
and V actinium; (4) A. mellifica L. from Taraxacum, pollen
Taraxacum and Tulipa; (5) Br emus fervidus Fab. from P.
malus L., pollen P. malus L. and Daucus Carota L.; (6)
Br emus vagans Smith from Garagana, pollen Caragana and
Tulipa; (7) A. mellifica L. from Taraxacum, pollen Taraxa-
cum, Tulipa and V actinium; (8) A. mellifica L. from Spiraea,
pollen P. malus L. and Spiraea; (9) A. mellifica L. from
Taraxacum, pollen Taraxacum and Tulipa; (10) Awdrewa
carlini Ckll. from P. malus L., pollen P. malus L. and !ZVt-
folium (original).
details of this work are given elsewhere. A more careful examination of large
numbers of nectar gatherers to determine what proportion of them are of value
as pollinators for apple bloom would appear to be indicated.
It would not appear that we would be justified in considering more than 50
per cent of the hive bees present in the apple bloom as effective pollinators;
whereas, in the solitary bees where this division of labour does not obtain, it
would seem that all females captured should be counted as potential pollinators,
solitary bees being mainly interested in pollen to prepare the pellets for their
60796—9
130
, , , 4p/5/??e///f/ca
Fig. 64.— Pollen collecting apparatus of insect pollinators oi the apple (original),
131
brood. In the case of Andrena?, a certain proportion taken were males which
are of inferior value as pollinators, but, since this proportion is small and
most of our apple visitors were Halicti, this would be of little importance.
Though more erratic in their flights, wild bees work the bloom with thorough-
ness and persistence. The pollen carrying apparatus of the hive bee, while
more efficient, does not favour this species in comparison with solitary bees from
the standpoint of pollination. With the latter the pollen appears to be, in
general, more loosely adherent and consequently more likely to be brushed off
during visits to the bloom. The pollen packed in the baskets of the hive bee
is of no significance in pollination, only those grains held by the dense covering
of branched hairs on all parts of the body being available. As previously
indicated, solitary bees do not appear to work the same limb or tree so per-
sistently, but it may be that this habit results in more cross-pollinations than
would otherwise be the case.
8. INFLUENCE OF NECTAR SECRETION AND AVAILABILITY
OF POLLEN
(a) GENERAL
The availability of food in the form of either nectar or pollen is recognized
as having a profound effect upon the activity of bees, exhaustion of supplies being
followed by a slackening off in flight. In the case of certain plants which secrete
only at certain times of the day, it is possible to note a close correlation between
nectar secretion and activity. In large orchard areas there would rarely be a
sufficient supply of bees to exhaust the supply of nectar, and during the blossom-
ing period, in weather favourable for flight, pollen supplies are always abundant.
On several days when practically no nectar was available a considerable number
of bees were noted gathering pollen. Varietal preferences of bees based on
differences in nectar secretion and production of odour no doubt occur, as noted
by MacDaniels (1931). The concentration of bees on varieties at optimum con-
ditions of secretion and concentration has also been noted. Other varieties are
preferred for the comparatively large quantities of free pollen available, as in
Golden Russet or Northern Spy.
Since nectar secretion was capable of measurement, however, careful records
were taken over a period of several days on several varieties of apples, at Kent-
ville, Blomidon and Scott's bay, N.S., to determine, if possible, the factors
influencing nectar secretion and the influence of the latter on bee activity. So
far as hive bees are concerned, nectar secretion would be expected to influence
mainly the nectar gatherers, but it was considered advisable to study the secre-
tion of nectar in relation to general bee activity and, particularly, to that of
solitary bees. Unfortunately, we had no facilities for determining sugar con-
centration, which may well have an important bearing on attractiveness.
The records regarding nectar secretion were taken and the necessary tabula-
tions made by Mr. Robert Ward, to whom the writer is especially indebted for
his faithful attention to the details of the work.
(b) RESULTS AND CONCLUSIONS
A complete tabulation of all the data secured in this study would be out of
place at this point. Neither is it possible to draw too definite conclusions on the
basis of a partial season's work. Since the results from the different stations
are in general agreement it will be sufficient for our purpose to consider in detail
the results from one station only and on one variety only; viz., Northern Spy
at Scott's bay.
It was found that the period of greatest secretion during the daylight hours
was approximately 9 a.m., from which point there is a gradual decrease until
60796— 9 i
132
late in the afternoon. It would appear that the nectar does not accumulate
during the day, but ceases after a definite amount has been deposited in the
nectary, the processes of secretion and reabsorption being apparently in equilib-
rium.
The results obtained from a study of secretion during the night varied some-
what, depending upon whether successive readings were made from different
blossoms or from repeated records from all the blossoms in the same clusters,
the former giving the maximum results at midnight and the latter at from 8.30 to
10.50 p.m. This would seem to indicate that nectar accumulates during the
night up to a certain point, which may be determined by the evaporation rate.
There appears to be a positive correlation between relative humidity and nectar
secretion, but in some cases this is slight. This correlation is most apparent in
the night readings.
Bee activity is so contingent upon a complex of factors operating simul-
taneously, that it is difficult to evaluate any one of them. It is not apparent from
the data secured that the activity of either wild or hive bees is closely con-
nected with nectar secretion. The fact that, with temperature and light condi-
tions favourable, bees show greatest activity during the morning hours may be
governed partly by the greater quantity of nectar available at that time. Con-
sidering the fact that different varieties in a mixed orchard are in their optimum
condition at different periods and considering also the amount of nectar avail-
able during apple bloom in proportion to the number of bees present, and the
importance of temperature, light and wind factors, it is only to be expected that
any effect due to variations in nectar availability might be effectively disguised.
9. COMPARATIVE CONSTANCY OF HIVE AND WILD BEES
The following important advantage has been claimed for the hive bee: —
That the hive bees show greater "flower fidelity," that is, they tend to visit
only one species of flower at a time for pollen or nectar, whereas ivild species
tend to visit a larger number of species.
Kt^L
A?e/a,//i4f //urn/*///? //? /&r £■&/?/
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7 8 9 ID II 12 lam Z 3 4 5 6 7
/IhCTARyT-CRHIOATt-APf-RARIRh AUAIDITY/WF- &V1LD Btt/
Fig. 65. — Bee activity iri relation to nectar secretion (original)
133
Though constancy of the hive bee in visiting blossoms of a single species
has been a matter of comment since very early times, our figures based on pollen
loads of all species concerned do not permit us to conclude with any degree of
certainty that any of the species studied whether hive bees, Halicti, Andrense or
Bremi, show any decided advantage over the other in regard to constancy except
that, where there is a great variety of species in bloom without any one pre-
dominating, the Andrenae observed showed least. Where a large acreage of
apple is available, all forms showed a considerable degree of constancy, exceeding
in all cases 50 per cent and often reaching 100 per cent, but, when abundant
bloom of many different species was available, without the predominance of any
one plant species, the constancy exhibited was very much less. Based on apple
bloom alone, Apis took first place with 80 per cent of pure loads, followed by
Halictus with 72 per cent, Bremus with 65 per cent and Andrena 57 per cent.
Based on all species of bloom, Halictus appeared to lead Apis in constancy, but
the difference indicated was not sufficiently great to be significant. If it were
possible to express the proportion of pollen in the loads, the degree of constancy
would appear greater than in percentage of pure and mixed loads, since a large
proportion of the loads classified as " mixed " were made up of a great prepon-
derance of one kind of pollen.
10. DISTRIBUTION AND CONCENTRATION
As indicated in other sections hive bees are more specialized in their
habits than are wild bees, and this affects their value as pollinators, sometimes
favourably, sometimes unfavourably. It has been shown by a number of
investigators that hive bees possess " scouts " and that these " scouts " are
able to make known to other workers the presence of food in the form of nectar
or pollen. Hive bees have been repeatedly observed to ignore apple bloom
near their hive to seek other more attractive bloom farther afield and, on
occasion, to concentrate on favoured varieties or on varieties in a favourable
condition of nectar secretion or pollen availability. Wild bees are not con-
sidered to have anything in the nature of " scouts " and hence would not be
expected to have the same tendency to concentrate as hive bees, though they
are certainly able to recognize and select bloom in its optimum state of
attractiveness. In the orchard, however, our counts are more consistent with
wild bees, even where colony distribution has been such as to secure maximum
evenness of distribution of the insects. Sudden concentrations of hive bees,
however, examples of which are discussed elsewhere, have occurred on a num-
ber of occasions in the course of our observations. Considerable unevenness
of distribution has, however, been noted with solitary bees, the exact reason
for which was hard to determine.
11. GENERAL SUMMARY
(i) The great present scarcity of hive bees in the Annapolis valley accen-
tuates the importance of a knowledge of the native fauna concerned in apple
pollination. It was found that the most important agents at the present time
in apple pollination were various species of solitary bees. These bees are
found everywhere nesting in the ground in roadside banks, pastures sparsely
covered with vegetation, the drier parts of dyke lands, in " running dykes "
and similar situations. They avoid sandy or gravelly soil in nesting and,
hence, are more numerous in places near the North Mountain, Long island,
etc., than in many other sections.
(ii) Observations made during the past four years indicate that in the
average orchard the number of solitary bees present during bloom was about
equal to the force of hive bees that would be released from one strong colony
134
per acre. Nevertheless, there was evidence of a shortage of bees in certain
individual orchards, and during 1932 there was an apparent general decline of
about 50 per cent in the population of solitary bees. It should be noted that
the three years previous to 1932 were exceptionally favourable for the increase
of the solitary bee population.
(iii) Our observations indicate that, with little other bloom available, one-
third of the total field force of hive bees may be found at one time in the apple
blossoms. Of these not all are of equal value in pollination, since a large propor-
tion are nectar gatherers. Solitary bees visit the blossoms mainly for the purpose'
of collecting pollen, which they mix with a little nectar and use for brood rearing
purposes. Therefore, practically the entire solitary bee population would be
expected to be potential pollinators.
(iv) The fact that hive bees only can be artificially increased and intro-
duced at will into the orchards is a decided point for the use of hive bees. No
other provision is possible against seasonal fluctuations in the normal popula-
tion of solitary bees.
(v) Hive and wild bees react similarly to temperature, light, wind,
humidity, etc.; but hive bees appear to work longer hours, and, while the
optimum temperature for both is about the same, a larger proportion of hive
bees are found at the lower temperature ranges and lower light intensities.
Furthermore, the fact that hive bees will work actively near the hive during
brief bursts of favourable weather, gives an advantage to orchards so supplied
in years of uncertain and changeable weather during bloom.
(vi) Definite figures as to numbers of visits of wild bees are not available;
but, placing the lowest possible estimate on the number of visits made by
either hive or wild bees, it is apparent that a force equal to that liberated from
a single, strong, overwintered colony would be theoretically capable of effectively
pollinating a number of blossoms, representative of the entire complement of
an acre of bearing trees, in a comparatively short period of favourable weather.
(vii) In pollen gathering habits the solitary bees are equally well adapted
for pollination purposes, and, in some respects, appear to have an advantage.
( viii) Many workers have claimed a superior value for hive bees with respect
to their greater constancy to the flowers visited, but we were not able to confirm
this observation in our studies, the difference between Halictus and Apis not being
significant.
(ix) Owing to limitations already noted, much further work must be done
before many of the points raised in the foregoing pages can be regarded as
satisfactorily settled.
E. UTILIZATION OF HIVE BEES AS ORCHARD POLLINATORS
W. H. Brittaix and C. B. Gooderham
1. HISTORICAL REVIEW
Many workers have published data and opinions regarding the actual
commercial value of hive bees for the purpose of pollinating apple orchards. A
number of typical examples is therefore included, in order to give a represent-
ative picture of the present status of opinion regarding this matter.
Gates (1917) states that bees are of more value to the fruit-grower than to
the apiculturist, because of their work in pollinating fruits. Many cases are cited
in which absence of bees, or weather which prevented their working, resulted in
poor crops. In one case, a high south wind prevailed during the blooming period,
and as a result the north sides of the trees alone had a good set. as the bees
worked in the shelter.
The case is cited by Weed (1918) of two orchards in Wayne county. N.Y.,
kept under observation at blooming time. Both had fair bloom— one had many
135
hive bees working in it, the other practically none. The crops were about equal
in the two orchards. Other wild bees, as Bombi, Andrenidae, Halictidae, etc., were
considered to be responsible for the pollination of the orchard which had no hive
bees in it.
Sax (1922) states that good crops have been obtained in New England,
where bumble bees were apparently the only pollinating agents. However, honey
bees are desirable and in some cases indispensable.
According to Haseman (1922) the hive bee is the best agent for the pol-
lination of deciduous fruit trees. Hive bees are more valuable in cool weather
than at any other time because the supply of other pollinating insects is then at
its lowest.
Bercaw (1924) describes experiments sponsored by the University of Cali-
fornia at the instance of the prune growers, showing that honey bees were the
chief pollinators of deciduous fruits in California. Citrus fruits are in the same
class.
DeOng (1925) emphasizes the danger of relying upon self-fertilization, partic-
ularly when a single type is grown in large areas; and states that under most
conditions, dependence must be placed on the aid of insects, and1 especially the
honey bee, for pollination. Bees are said to be better adapted for pollen carrying
than other insects, but some are of greater value than others. He notes that
bumble bees, carpenter bees, etc., are not active early in the spring, or if so, are in
such small numbers that they are comparatively ineffective as pollinators, and
during the summer they have only one to six brood cycles; whereas the honey
bee has twelve to fifteen broods in a summer. He points out that the workers
survive the winter also, while all except the queens of the native species succumb.
Another advantage of hive bees noted by this worker is that their numbers can
be distributed as desired in the orchards, while the numbers of wild bees depend
on the natural surroundings.
Because bees are present in large numbers in the spring, and work from
morning until night and from early spring until late fall, they are regarded as the
most efficient pollinators of deciduous fruits, by Davis (1926). A few instances
of the value of honey bees to orchardists are given. Two hundred hives of bees
were placed at one end of an 80-acre cherry orchard at Belleview, Ohio. The crop
grew lighter in proportion to the distance from the hives. In another orchard
the bees were all killed by foul brood, except one colony which was placed
in the centre of the orchard. There was a definite fruit area about this hive, while
the other trees had no crop. Orchardists are advised to have one colony for every
fifty trees, and to avoid spraying at blooming time.
The importance of bees to the fruit-grower is emphasized by Hendrickson
(1927) and the causes of decreased numbers of wild and tame bees are ascribed
to intensive cultivation and lack of skill in beekeeping respectively on the part
of fruit-growers. With regard to the distribution of bees in orchards, a case is
cited in which fifteen colonies were placed on each side of a thirty-acre prune
orchard. A heavy crop was borne along the edges, but in the centre the crop was
very light.
According to Barclay (1928) the orchard districts in New Jersey are sur-
rounded by an extensive trucking area, and as a result wild bees of all kinds are
scarce. He states that, since 1918, the use of bees for pollinating purposes has
increased steadily. One hundred colonies were rented in 1918; 1,600 were rented in
1927. Prices ranged from $5 to $8 per colony. Blueberry and cranberry growers
are faced with a problem similar to that confronting the orchardists.
Marshall, Johnson, Hootman, and Wells (1929) present evidence which is
considered to indicate the value of bees in orchard pollination. An 11-acre Spy
orchard had never produced more than 1,500 bushels in any season from 1918 to
1926, even though it contained an apiary of 40 colonies. In 1927 pollinizing
bouquets were distributed throughout the orchard, which, in that vear produced
136
a crop of 5,200 bushels. Other examples are given. The commercial fruit grower
is said to be almost entirely dependent upon the hive bee to insure pollination
of his fruit, and it is stated that there are not enough bees in many orchards at
blossoming time to insure adequate cross-pollination during certain seasons when
the weather is unfavourable for insect activity. It is claimed that small orchards
and those adjacent to uncultivated fields, woods or swamps, where wild bees
can winter in satisfactory numbers, may produce crops without the addition
of bees, but in most commercial orchards the chances of a good crop are increased
by the addition of one colony per acre in mature orchards, or one to four acres
in orchards 10 to 15 years old.
Lundie (1927) states that out of the 119 varieties of apple commonly grown
in South Africa, 77 are self -sterile and the others give bigger crops when cross-
pollinated. He points out that honey bees in South Africa are able to rear several
brood cycles before the fruit bloom appears, and for this reason are the most
valuable pollinating insects. He regards wild swarms as having some value, but
not comparable to that of tended hives, because such swarms are usually weak in
the spring. He contends that non-social insects are not numerous enough to be of
importance in large orchards, but do some good work.
In a popular bulletin by Phillips (1930) the place of the honey bee in the
orchard is discussed. Due to cultivation, destruction of both honey bees and wild
bees by dusting and spraying, and to the natural scarcity of wild bees in spring,
honey bees are considered to be the most satisfactory pollinating agents.
(a) EXPERIMENTAL USE OF HIVE BEES
During the entire course of our work, poisoning from sprays and dusts con-
stituted a disturbing factor and rendered abortive much of the work attempted.
This and other causes limited the scope of the work. Only those projects that we
were able to carry to completion are reported herein.
(i) Tent Experiments. The best indication of the necessity for bees in
order to ensure proper pollination of the apple is obtained from a study of the
results of trees enclosed in tents, both with and without bees, because it is pos-
sible to control the conditions of the experiment. These experiments have been
discussed in detail elsewhere, but the following tabulation is of interest in con-
nection with the present discussion, since it emphasizes, for all varieties, the
necessity of bees for pollination, as well as the primary need for a suitable supply
of pollen for them to carry. It will be noted that even such a highly self-
fruitful variety as Baldwin gives improved results when supplied with bees
and the pollen of a self-fruitful variety. The " bouquets " used in these tests
were blossoming limbs of the desired varieties placed in tubs of water inside
the tents; bees were placed in the orchard to provide for the open pollinated
trees and abundant sources of suitable pollen were present.
TABLE No. J8.— RESULTS OF TENT EXPERIMENTS, 1929-1932
Per cent fruit
Variety
Effective
polli-
nizer
and bees
In-
effective
polli-
nizer
and bees
No
polli-
nizer
and bees
(selfed)
No
polli-
nizer
and
no bees
Effective
polli-
nizer
but
no bees
Open
polli-
nation
Gravenstein
10-90
5-42
817
10 05
114
3-58
4-96
2-70
212
3-32
7 • 77
200
0-67
103
3-49
0-85
0-47
1-81
5 05*
1-20
9-91
4 74
10-40
Spy
i -
* Abnormally high percentage fruit obtained in 1932, due to small number of blossoms on tree used
bas raised the general average for this treatment.
137
The velocity of the wind inside and outside the tent was taken for pur-
poses of record and because of its bearing on wind pollination on tented trees.
Considerable irregularity was noted, but the difference between tented and non-
tented trees was very apparent. In order to equalize results, therefore, a draft
from an orchard duster was blown through the bouquets and over the tree, the
velocity being 30 miles per hour at six feet from the nozzle.
(ii) Field Experiments. — To secure comparable results under uncontrolled
orchard conditions is impossible, because fruitfulness is due to too many factors
not under the control of the experimenter. The possibilities of selfing, unfruit-
ful crosses, poisoning of bees and many other factors, render this type of work
very uncertain and unsatisfactory. Many reports of spectacular results from
the use of bees are of doubtful value, as they indicate a single years' observa-
tions only and data regarding succeeding crops are rarely forthcoming. Sudden
increases in the crop of individual orchards have been repeatedly observed,
under conditions sometimes difficult to explain, but which were certainly not
due to this particular factor. It was apparent throughout the work that the
presence of an adequate supply of effective pollinizers was of prime importance
and that, unless a fair proportion of the bloom present was of this kind, unfruit-
ful crossing or selfing negatived the results of bee introduction.
Where such effective pollinizers have not been provided when the orchard
was planted, they should be introduced as speedily as possible by top-working
the desired number of trees. The temporary expedient of pollinizing "bouquets"
consisting of limbs of the desired bloom placed in tubs throughout the orchard,
has been recommended by a number of workers, but there are several disad-
vantages attending the practice even as a temporary measure. A great deal of
labour is involved in securing the bouquets and in keeping them fresh. It is
very difficult to procure bloom in such a quantity as would compare with the
required number of trees in full bloom, and the chances of selfing or unfruitful
crossing are greater than for fruitful crosses. Furthermore, such bouquets
appear to be much less attractive than full trees. Nevertheless, in experimental
work it was impossible to wait for " grafting out " operations and, for this reason
bouquets were employed.
In numerous experiments with bouquets we were never able to secure suffi-
cient to utilize them in an orchard of any size without undue cutting of the
trees used as the source of the bouquets. Even when bouquets were obtained
as large as possible, kept fresh and placed on small stands surrounding the
trees, we could, in many cases, get little definite evidence of value from the
use of such bouquets in orchards. Furthermore, counts made at the bouquets
often showed few bees visiting them when masses of other bloom were available,
though bouquets in full bloom, obtained from a later district and placed in
orchards just out of bloom, were heavily visited. In the same orchard where
negative or inconclusive results were obtained from the use of bouquets, hand
pollinations with the same variety of pollen as that provided by the bouquet
gave a heavy set of fruit. Our experiments were done mainly with Blenheim,
a variety in which pollination difficulties are frequently experienced. By
placing rings of bouquets around a group of trees, or by enclosing a row of trees
with a row of bouquets, we were able, in one case, to double the set on that par-
ticular row. In most cases, however, the results were not significant and we
were unable to get the spectacular results obtained by certain other workers.
The result of only one such experiment under the optimum conditions for
securing such results, will be reported in detail. The experiment was conducted
in an orchard of Blenheim, Stark and Mann, cross-unfruitful and self-unfruit-
ful varieties, consisting of 17, 41 and 29 trees respectively. Hand pollination
tests in 1931 indicated that a pollination problem was involved and, even in
that year when Blenheim everywhere gave a crop, this orchard failed to pro-
138
duce. A ring of bouquets was placed about the trees so as to enclose several
of each variety. Bouquets of cross-fruitful varieties were used, mainly Wagener
and Red Astrachan. Owing to the weather there was no difficulty in keeping
the bouquets fresh; they were visited freely by bees and, though wTeather con-
ditions during the bloom were unfavourable, there was sufficient time during
bloom to ensure pollination, since 50 hives of bees were placed in the orchard.
5
3
3
3
5
JY
5
IV
3
S
S"
5
5"
S
5"
5
5
S
5
3"
3
3
0
3
3
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S
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FlG. 66. — Diagram of C. Bishop orchard.
Somerset. X.S. (original).
Blenheim and Mann blossomed well; but Stark, which bore a heavy crop
the year before, had little bloom. The results obtained from typical trees inside
and outside the ring of bouquets are indicated in the accompanying table. They
indicate a commercial set on the Blenheim and a less than commercial set on
Mann which, however, were in a particularly poor condition from a nutritional
standpoint. The fact that the crop decreased as the distance from the bouquets
increased was plainly evident.
TABLE No. 20
Variety
Position
Number
blossoms
used
Per cent
fruit
Blenheim
Within bouquets
Outside
9,918
10,000
8,060
8,077
6-47
«
}•:;:;
Mann
Within "
2-30
"
Outside
1-58
According to the owners of the orchard, the crop obtained under these con-
ditions on Blenheim which had a full bloom, is over double that of previous
years. Considering the large amount of unfruitful pollen available and the
comparatively poor nutritional condition of the orchard, the results are as good as
could be expected. Other experiments in solid blocks of Blenheim gave similar
results on trees immediately adjacent to the bouquets, in one case doubling
it as compared with the general average for the orchard.
139
140
(6) WHEN HIVE BEES SHOULD BE USED
It must be admitted that, whereas the opinions of most of those who have
written on the subject of the value of hive bees in orchards, appear to be strongly
in favour of this practice, the tangible evidence as to their value is, as has
already been indicated, rather meagre so far as apple orchards are concerned.
Again it is often assumed, on the basis of little actual observation, that wild
bees are "scarce." Many of the species concerned are small and inconspicuous,
and we have repeatedly checked the statement " There isn't a bee in the whole
orchard," only to find solitary bees present in considerable numbers.
Obviously, a survey should be made to determine the extent of the wild bee
population before it can be confidently stated that they are " scarce." Unfor-
tunately, investigations have never been carried on for a sufficient length of time
in one place to determine the fluctuations in such populations that may occur
from year to year; and whether, even in favoured locations, they may not, occa-
sionally become very scarce. Generally speaking, territory with considerable
waste land, rough pasture, dykes, etc., will support a considerable bee popula-
tion. The difference between certain stations in the middle of the Valley and
others near the North Mountain is quite marked. Even in orchards wholly or
partly in sod, there are sometimes places favourable to the nesting of wild species.
On the other hand, certain soil types and intensive clean cultivation, with an
absence of rough land or other favoured nesting places may possibly result
in an actual scarcity in all years, as has been claimed by some workers. In
other cases, unfavourable weather, natural enemies or other factors may deplete
the native fauna. Under such conditions there would be no alternative to sup-
plying the necessary number of hive bees as a matter of orchard routine. Our
own observations in four years out of five, indicate that there was an adequate
population of wild bees to produce a satisfactory set in most orchards studied.
However, in the fifth year, there were extremely unfavourable conditions pre-
vailing during the bloom of certain varieties. Under these conditions, a much
heavier population of pollinators than would be necessary in a normal year, would
be a decided advantage. Fruit setting on many varieties was very light, but
very satisfactory sets were obtained even with short periods of exposure, where
hive bees had been properly distributed in adequate numbers. The tendency
of the bees to exhibit greatly increased activity, especially near the colonies,
during a warm, sunny period following one of confinement, helped to bring this
about. The provision of hive bees, therefore, in any commercial orchard is a
measure of insurance against such a condition, and should be so regarded. When
general unfavourable conditions prevail, this must be compensated for by a force
capable of effecting pollination in limited periods of favourable weather. The
question of whether or not such provision shall be made, resolves itself into a
question of whether the cost of the operation will be more than compensated for
by the expected benefits.
2. PROBLEMS INVOLVED IN COLONY DISTRIBUTION AND NUMBER
(a) THE TIME NECESSARY FOR POLLINATION
The amount of pollination that takes place varies with the strength of the
colonies and with the length of time available for them to do their work. With
favourable weather, a relatively small population may accomplish the same
result as that obtained by a much larger force in a short period. In considering
this question, the amount of pollination secured in definite periods of time by a
population of given strength is of value.
At Kentville in 1931 we attempted a small experiment to determine the
length of time actually required for the pollination of three Northern Spy tree-.
141
covering them with tents and opening one side of the tent for 1 hour, 5 hours and
for one day respectively. Unfortunately, the bee population at this station
during the period in question was very low, viz., only -028 per minute — much
too low on which to base any calculations. In view of this fact it is not to be
expected that the results would be very consistent. However, as indicated by
the accompanying table there is a great difference 'between the tree that was
exposed during bloom and those exposed only for a few hours. In interpreting
results from work of this kind it must be borne in mind that the set of fruit
obtained is by no means an accurate gauge of the effective bee population,
because double visits, unfruitful crosses, and selfing must be taken into account.
There is also a very definite limit to the number of blossoms that can set fruit and
many blossoms that are pollinated can never produce mature fruit. Therefore,
figures showing the set obtained from a given number of blossoms exposed to
pollination for a definite time can have but limited value, though it is of interest
to study the results obtained, particularly from exposures of short duration,
since, in these cases, the blossoms pollinated were not in excess of the number
that could set under normal conditions.
TABLE No. 21.— EFFECT OF LENGTH OF EXPOSURE ON POLLINATION
Tree
Time of exposure
Number of
blossoms
counted
Per cent
fruit
1 hour
5 hours
All day
Throughout bloom .
2,553
2,641
2,938
2,552
0-35
0 15
1-29
5-72
Note. — Total acreage of orchard 70; number of colonies 37.
It will be noted that the tree exposed throughout the day shows a higher per-
centage than the other two, but the tree with a five-hour exposure shows a lower
percentage set than the one exposed for only an hour. These numbers were so low
that individual differences in the tree, its location, number of blossoms and the
error inherent in such a small scale experiment, might easily account for the
differences. The experiment shows that, under these particular conditions, ade-
quate pollination was far from being obtained from a full day's exposure.
During 1932 further work was projected in which it was planned to expose
whole trees and individual limbs to pollination by bees for varying periods of
time, viz., 1 hour, 3 hours, 1 day, 2 days, 3 days, etc. Unfortunately, weather
conditions interfered seriously with the experiments. In some cases the short
exposures were carried out under ideal conditions, but the weather then became
wet and cold and all activity ceased for days at a time. The result was that
an intended one-day exposure ran into several days, during which no bees were
present. When conditions again became suitable for flight, they were in some
cases more and in some less favourable than for the shorter exposures, with the
result that, during the longer exposures, there were in some cases actually a
lower number of bees available than during the shorter periods. Interpretation
of results therefore becomes very difficult. Bearing in mind these points, the
results as indicated in the accompanying table, show no more irregularity than
would be expected from the nature of such tests. In this tabulation we have
calculated the number of " effective hours " that the blossoms were exposed.
This was arrived at by taking the total number of ten-minute periods during
the time of exposure of that particular bloom, when any number of bees, how-
ever small, was found at work in that particular orchard. This figure, in turn,
was divided by six. Since, however, the number present during the period of
exposure was an equally important factor, we have also calculated the average
number of bees taken per ten-minute count over the same period.
142
Allowing for the irregularities inherent in such tests, and without attempt-
ing to carry conclusions from such figures too far, we find that the set obtained
in as short a period as one hour was sufficient to give a commercial crop in the
case of Gravenstein, and that the set obtained in five hours and upwards of
effective exposure, with suitable conditions for good activity of the bees, in
Gravenstein and King was great enough to require thinning. Had the entire
tree been exposed in Mcintosh, greater sets undoubtedly would have been
obtained on the tented trees, since these showed a set on the exposed side notice-
ably in excess of that obtained on the unexposed side. The comparatively low
sets of fruit on all exposures in the case of Blenheim were obtained in an orchard
in which cross-unfruitful and self-unfruitful varieties were mixed, viz., Stark,
Mann and Blenheim, and was one in which poor crops were the general rule.
Wagener and other bouquets were supplied, but this, undoubtedly, did not prevent
a great deal of unfruitful cross- and self-pollination.
Allowing for the proportion of nectar carriers, duplicate visits, unsuccessful
crosses, etc., these figures do not appear inconsistent with the information
obtained from other sources.
TABLE No. 22.
-TABLE SHOWING INFLUENCE OF LENGTH OF EXPOSURE ON
POLLINATION
Variety
Number of
blossoms
used
Number of
effective
hours (*)
of exposure
Average
activity
per 10
minutes
during
period of
effective
exposure
Per cent
set
obtained
Per cent
fruit after
July drop
1,599
2,267
2,312
2,382
2,547
2,658
2,141
909
1,556
1,631
1,363
2,086
1,247
1,393
3,325
2,496
2,881
2,311
1,174
1,007
1,268
1,401
1,870
nil
1
5
HI
23§
Duration of
bloom,
nil
4|
Hi
22|
23$
Duration of
bloom.
5
I
21
4|
Duration of
bloom .
nil
1
4
5*
Duration of
bloom.
11-69(2)
9-97
18-47
11-92
20-77
18-59
26-86
1-36
5-98
27-16
25-61
39-26
28-63
19 02
4-69
6-86
6-98
13-85
0 085
119
0-47
0-21
7-54
1-63
16-78
15-97
12-35
801
5-31
3-97
et
7 01
«
6-76
u
10-91
«
9-63
u
10-28
0-25
204
103
2-79
5-38
5 05
1-99
«
6-72
«
10-93
"
7-19
u
9-70
a
11-84
Mcintosh (0
200
3-44
3-29
3 91
5-61
it
5-73
a
8-57
0 085
131
2- 12
1-98
010
»
008
a
0-21
u
ti-L'li
(*) An effective hour represents 6 ten-minute counts, during which the blossoms were exposed and
during which some bee activity was actually observed in the orchard.
0) Intent.
(2) High original set probably produced by selfing from rubbing about inside the bag.
(b) TYPE OF COLONY REQUIRED
(i) Historical. Most writers favour the use of strong overwintered colonies
for pollination purposes. Some, however, recommend the use of package bees
when others are not available, while a few go so far as to claim that certain
types of packages are preferable and have a larger field force than overwintered
colonies. The following recommendations may be regarded as typical:
143
DeOng (1925) recommends that bees which are to be used for pollination
should be in good condition and strong in numbers in the spring, though, for
purely honey producing hives, large numbers in early spring are not so necessary.
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Philp and Vansell (1932) in connection with the use of bees for pollination,
point out that only strong colonies will prove of much value during the early
spring, when a large number of bees are required in the hive to maintain the
brood nest temperature at 95° F.
144
Phillips (1930) advises that strong colonies only should be used in the
orchard, since a hive with twelve frames of brood is four times as valuable as
one with six frames of brood. For this reason he considers that the colony
should be in two hive bodies. The strength of the colonies is regarded as more
important than their number by this worker, since powerful colonies send out
proportionately far more bees than weak ones, and also start flight sooner.
While no hard and fast rule is laid down, the author suggests one twelve-frame
colony to each four acres, or one six-frame colony per acre.
Murneek (1930) considers that a good colony should contain at least five
pounds of bees, or approximately 25,000.
A comparison was made by Hutson (1928) between the numerical strengths
of package bees and overwintered colonies by weighing the entire colony, remov-
ing the bees, then weighing the empty hive — ten being used in each case. On the
basis of 5,000 bees to the pound, the bees in ten hives were said to comprise
108,750 individuals as compared with 150,000 for ten 3-pound packages — an
advantage of 40,000 over the overwintered colonies. It was also shown that over-
wintered colonies were very unequal in strength. On the basis of the foregoing, it
was concluded that 3-pound package bees were superior to overwintered colonies
on the score of strength and uniformity, thus giving the orchardist an opportunity
to secure better distribution in his orchard.
Other New Jersey experiments (1929 and 1930) showed that combless
packages, regardless of size, were not comparable in value to overwintered colon-
ies; and that the orchard packages, while superior to combless packages, were
also inferior to overwintered colonies.
Filmer (1931 and 1932) has presented some evidence regarding the value
of different types of colonies. The packages used were established three weeks
before the counts were made, which were carried out, presumably, during fruit
bloom. Packages established on foundation were fed 40 pounds of "one to one"
sugar syrup. From a study of the data presented in this paper the following
may be gathered: —
,1. Total bees show no correlation with total pollen gatherers which vary
greatly in different types of colonies.
2. Total bees for overwintered colonies and for package^ supplied with
foundation only, is the same; for 3-pound packages on drawn comb it is less.
3. Considering the different weights of colonies in relation to total activity.
2- and 3-pound packages seem little, if any, inferior to 6-pound packages of
the same type. In fact the 6-pound package on drawn comb shows less activity
than the corresponding 2-pound package. The wrapped 3-pound package showed
only 50 per cent of the activity of packages supplied with drawn comb, and 43
per cent of 3-pound overwintered colonies.
4. The average pollen gatherers liberated from 2-, 3- and 6-pound packages,
whether those supplied with drawn comb or with foundation alone, showed little
significant difference, but were decidedly less efficient than overwintered colonies;
while wrapped packages showed negligible efficiency.
5. Total pollen carriers are greatest, in all cases, from the overwintered
colonies; for 3-pound packages the count strongly favour- the packages supplied
with drawn comb in one case, with result about the same in the other.
6. On the basis of the data secured, the author considered that there was a
relation between the brood content and total activity in colonies of the same
weight, with bees on foundation showing a greater activity in relation to brood
area than those on drawn combs. He considered that the figure for total bees
was of more value than that of pollen carriers alone, owing to the great van-
ability in numbers of pollen carriers.
145
Farrar (1931) has brought forward evidence bearing on the question of the
relative value of overwintered colonies as compared with package bees. He notes
that considerable emphasis has been placed upon the necessity of designing a
" colony unit " that the fruit grower can use without a knowledge of bees and
with a minimum of handling. He points out that, upon this development,
depends the question of whether to stimulate practical beekeeping or to depend
upon packages. He considers that the orchard yield is the result, of too great a
complex of factors to be a suitable criterion of the colony's efficiency in pol-
lination, but the degree of pollination should be proportional to the number of
bees visiting the blossoms. He assumes that the colony unit furnishing the
greatest number of field bees per minute will provide visits to the greatest
number of blossoms, and therefore, accomplish the greatest results in pollination.
He describes the results of two years experiments at Amherst, Mass., on the
number of bees furnished during bloom by (1) package bees, (2) nuclei, and (3)
overwintering colonies, which indicate a pronounced advantage in favour of the
last. In a normal season (1929) the overwintered colonies furnished 8 to 20 times
as many bees per minute as 3-pound packages or 3-frame nuclei, when the bees
were allowed to fly from their shipping package. In 1930, under abnormally
favourable conditions, normal overwintered colonies showed a decided advantage
over 5-pound packages, and these in turn over smaller packages. The writer
concludes that where colonies cannot be secured, strong packages should be
obtained a week in advance of expected blooming date, installed in hives — prefer-
ably on drawn comb — and fed, in order to insure immediate establishment of the
brood nest.
Woodrow (1932) has presented some valuable data respecting the relative
value of different types of colonies using the method of Farrar (loc. cit.), the
counts being made during apple bloom. Records were based on the number of
bees leaving the hive, made up of 3 pounds of adult bees, one 3-pound package
on comb foundation, and one 3-pound package in its shipping cage. The second
was similar to the first, but consisted of 5-pound units. The third group
consisted of unmodified overwintered colonies, one with 3 frames of brood and
1-63 pounds of bees; one with 7 frames of brood and 4-38 pounds of bees; and one
of 16 frames of brood and 8-25 pounds of bees.
Flight from 5-pound units exceeded those from 3-pound units, though not in
proportion to the strength of the colonies. A study of the flight figures showed
that, in general, at any given temperature, the flight of any colony wTas roughly
proportional to its strength ; but the weaker colonies flew less freely at the lower
temperatures and more freely at the higher temperatures. It is concluded from
the results of these studies, that strong overwintered colonies are superior to
package bees, but that if only weak colonies are available, 3- or 5-pound
packages are more desirable, since these can be obtained for the same price. In
this work the total number of bees issuing from the hive was used with no dis-
tinction between pollen and nectar gatherers.
(ii) Observations on Strength of Different Types of Colonies. — At Ottawa in
1931, four overwintered colonies of average strength were measured for brood,
potential force in bees, and total force. The results are indicated in the following
table:
TABLE No. 23.— STRENGTH OF OVERWINTERED COLONIES MAY 6, 1931
Colony number
Brood in
square
inches
Potential
force of
bees (*)
Weight
of bees
Total
force
in bees
313
650-52
805-38
890-03
725-90
16,260
20,134
22,250
18 147
lbs. oz.
3 11
5 11
5 12
4 4
18,437
316
28,437
327
28,750
320
21,250
(*) The potential force refers to the number of bees that would emerge from their cells within the
next 21 days.
60796—10
146
The above table shows that all overwintered colonies contained a stronger-
force of bees than did the 2-pound or 3-pound packages which arrived
May 5, though definite figures for the latter are not available. Furthermore, all
were stronger than 3-pound packages, and two of them stronger than 5-
pound packages, and in addition all contained brood, which the packages
received did not. The total force and the field force of the same colonies were
taken during apple bloom as indicated in table No. 24.
TABLE No. 24.
-STRENGTH OF OVERWINTERED COLONIES DURING FRUIT BLOOM,
1931
Colony number
Brood in
square
inches
Potential
force of
of bees
Total
force
in bees
Field
force
313
1246 • 18
1279-56
1262-88
1130-76
31,154
31,989
31,572
28,269
25,937
31,875
28,750
21,875
16,875
316
14,062
327
18,750
320
10,937
The above were actually measured by weight and the figures based on 5,000
to a pound.
It will be noted that the field force of each of the overwintered colonies
alone, exceeded the total force of bees in a 2-pound package while two of them
exceeded a 3-pound package.
The colony strength, and more particularly the strength of the field force,
is a most important consideration in the use of hive bees for pollination pur-
poses. Our own information indicated that the working force is much greater,
both actually and proportionally, in a strong colony than in a weak one. It
appears that not only do more bees leave the hive, but they make longer flights
and will work when weather conditions are less favourable. These facts were
very apparent throughout the entire investigation. Furthermore, anything that
tended to weaken the colony, such as persistent unfavourable weather and lack
of stores resulting in a break in brood rearing, or cases of poisoning from sprays
or dusts, quickly reduced the activity noted in the orchard. Beekeepers ordi-
narily do not depend upon apple bloom for a surplus of honey, but are content
to have their colonies at the peak in time for the clover flow. For apple pollina-
tion purposes this is not sufficient and special means must be taken to get the
colonies into optimum condition by the time the apples blossom.
(iii) Experimental. — In 1932, it was decided to make a comparison of the
performance, during pollination, of the different types of colonies. Unfortunately
the overwintered colonies were extremely weak and, owing to unfavourable
weather, the packages, instead of increasino- in strength, actually dwindled in
numbers of individuals. In the test there were four overwintered colonies and
two each of 2-pound, 3-pound and 5-pound packages. The latter were received
on April 26 in excellent condition.
They were released on drawn combs as soon as they arrived, the weather
being very cool, and some rain mixed with snow was falling. The queen accom-
panying one of the 3-pound packages was found dead, but was immediately
replaced with a queen from another package. The overwintered colonies that
were to be used as checks against the packages were still packed in their winter
cases. Therefore, the package bees were released into protected hives to make
conditions comparable.
On April 29, the force of bees in each of the overwintered colonic- was
weighed and calculated on the basis of 5,000 bees to the pound. The results were
as follows: —
147
Colony number
Weight of
bees
Total
force
Colony number
Weight of
bees
Total
force
241
287
lbs. oz.
2 14
1 7
14,375
7,187
240
257
lbs. oz.
2 7
2 4|
12,187
11,406
Although the colonies selected were of good average strength for the season,
the above figures show that they were very little stronger in bees than normal
2-pound packages, and weaker than the 5-pound packages. The colonies, how-
ever, already had brood in their hives, some of which would emerge before the
apple bloom opened, while the packages had none.
On April 30, this brood was measured and found to be as follows: —
Colonv numbers 241 287 240 257
Square inches of brood 417-02 270-37 441-77 408-37
Potential force in bees (*) 10.425 6,759 11,066 10,209
(*) The potential force in bees represents the number that would emerge within the next 21 days.
On May 19, two apple trees in the bee yard were in bloom but none had
opened in the main orchards. Another measurement in bees and brood was
made on this date and this is shown in table 25. The field force of the colonies
was not determined at this time.
The figures in table 25 show that all four overwintered colonies had
gained in strength both in bees and brood since the counts of April 29 and 30;
but the gain in bees in colonies 240 and 257 was very slight. It will also be seen
that all packages were reduced in strength of bees, the greatest reduction in
each group equalled 46-88 per cent for the 2-pound packages, 47-92 for the
3-pound packages and 36-25 for the 5-pound packages. Even with this loss
the 5-pound packages still had a larger force of bees than the overwintered
colonies, at the commencement of apple bloom. It should be pointed out here,
however, that because of poor wintering and heavy dwindling during the early
spring, the overwintered colonies were much weaker in 1932 than they had
been for the past 16 years. On the same date in 1931 four average colonies
contained an average of 5 pounds 6| ounces or approximately 27,109 bees. It
will be seen, therefore, that the comparison was made under abnormal condi-
tions, affecting the overwintered colonies particularly, though as noted already
the packages were considerably weaker than their designated strength.
On May 20, the day after the measurements shown in table 25 were
taken, it was estimated that about 5 per cent bloom was open in the main
orchards.
TABLE No. 25.— TABLE SHOWING THE APPROXIMATE NUMBER OF BEES AND
THE AMOUNT OF BROOD IN OVERWINTERED COLONIES AND PACKAGES
ON MAY 18-19, 1932.
Colony number
Overwintered colonies
2-pound
packages
3-pound
packages
5-pound
packages
241
287
240
257
305
319
211
309
333
334
1,090-50
27,262
16,250
610-64
15,266
9,062
878-47
21,962
12,812
829-74
20.743
11,562
541-14
13,528
6,250
466-50
11,662
5,312
738-85
18,471
7,812
727-67
18,192
11,562
768-67
19.217
19,062
736-66
18,416
Total force of bees in colonies
15,937
The apple bloom lasted for about 12 days, as it was practically all gone on
May 31. No further measurements of bees or brood were made, but counts of
bees returning to the hives were made for 2 and 4 minute periods whenever
weather conditions permitted during the time of bloom, according to the trapping
method devised by Farrar (1931). During the period under review records
60796—10*
148
of the activity of over 7,000 bees were made. The results were averaged to show
the comparative number per minute of total bees and pollen gatherers liberated
by each type of colony. These data are presented in table 26.
TABLE No. 26.— NUMBER OF BEES LIBERATED PER MINUTE FROM DIFFERENT
TYPES OF COLONIES
Type of colony
Average
pollen
gatherers
liberated
per minute
Average
total
liberated
per
minute
Average
total force
in bees
Average
potential
force in
bees
Overwintered . . .
2-pound package
3-pound package
5-pound package
8-46
2-11
8-51
5-56
35-89
6-52
31-56
38-20
12,421-5
5,781
9,687
17,499-5
21,308-25
12,595
18,663
18,816-5
This table indicates little significant difference between the different types of
colonies, except that the 2-pound packages are much inferior on all counts. The
fact that the 5-pound packages, though stronger in field force and in total numbers
liberated, are lower in pollen gatherers, may or may not be significant. That the
potential force of the 5-pound packages is little different from that of 3-pound
packages, in spite of their greater force of bees at this time, is worthy of note.
The obvious weakness of the overwintered colonies, averaging only about 2^
pounds, makes the data worthless as an indication of the performance of strong
colonies. Nevertheless, the figures are presented for what they may be worth.
Since, for both 2-pound and 3-pound packages the total force was less than the
field force for a good overwintered colony, the superior value of the latter, for
pollination purposes, would appear to be obvious.
(c) FLIGHT AND CONCENTRATION OF BEES
(i) General. — A great deal has been written regarding the distance of bee
flight and the problems involved in the point at which maximum concentration
occurs. It is usually stated that bees will fly a mile or two from the hive for
nectar or pollen and even much greater distances have been recorded. The
maximum distance bees will fly is determined by many factors, <ome of which
are considered in the following pages.
Certain workers appear to believe that there is a point located at a definite
distance from the hives, at which the greatest concentration of bees will take
place. Hutson (1926) considers that this point is 15 feet from the hives, gradually
diminishing as the distance increases, and that this, at least in certain cases, car.
be definitely correlated with the set of fruit obtained. On the other hand, many
workers contend that bees tend to concentrate at a much greater distance than
stated by Hutson. For example, MacDaniels (1931) describes experiments in
which it is shown that bees working out of the hive do not stop close to the hive,
but rather go directly to some distant spot. It was further concluded by this
worker that the placing of colonies of bees with relation to the varieties to be
pollinated is of less importance than the position of the pollen source in relation
to the trees to be pollinated. Our counts and observation- gave no encouragement
to the belief that there is a definite mathematical point at any certain distance
from the colonies at which maximum concentration will occur. There is. how-
ever, considerable evidence supporting the contention that the optimum working
distance is not necessarily close to the hives. In this connection, observations
made at Coaldale, Alberta, are of interest. On a fine bright day. in an apiary
located on the edge of an alfalfa field, with nectar secretion abundant and meat
activity at the hives, the bees were going some distance for their supplies and a
search of the particular field in which the hives were located showed only an
occasional bee in the blossoms, though more distant fields were freely visite
149
It would appear that, while the bees are, in general, found in greatest
numbers near the hives, the distance of flight and the point of maximum con-
centration are variable and are conditioned by a number of factors of which (i)
the condition of bloom, (ii) varying varietal attractiveness, (iii) the amount and
mass of bloom available in relation to the bee population, (iv) the availability of
other kinds of bloom, (v) the physical features of the area concerned, (vi) the
prevailing weather conditions, (vii) the position of the colonies, and (viii) the
habit of bees of working in a limited area, are a few of those that must be taken
into account. These are discussed in the following sections.
(ii) Condition of Bloom. — The condition of the bloom, particularly with
regard to nectar secretion and the availability of free pollen, evidently has an
influence on the activity of bees on that particular variety. This was very
noticeable throughout the course of our observations. What appears to be a good
example of this fact is recorded in our notes for 1930. The observation was made
on Long island where an apiary of 25 strong colonies was placed just north of an
orchard in full bloom. Other orchards, to an extent of about ninety acres,
extended westward for a distance of two miles, there being no orchards on the
east. Four men stationed in the orchard adjoining the colonies took observations
throughout the day, but recorded only a negligible number of bees. During the
afternoon two men scouted the entire island examining, besides apple, the blos-
soms of oak, rhododendron, blueberry, horse chestnut, dandelion, clover, Siberian
pea, star of Bethlehem, plum, Labrador tea, lilac, mountain ash, etc., without
finding any bees. Returning to the apiary, where the bees were still working
actively, a flight of bees could be seen flying westward. This line of flight
led to a back orchard of Ben Davis trees in full bloom, on an adjoining farm
about \ mile distant from the colonies.
Upon approaching this orchard a strong aroma of apple blossoms and a
distinct hum of bees could be detected, at a considerable distance from
the trees. The first two counts, begun at 4.20 and 4.30, gave counts of 39 and
23 respectively, and the blossoms were obviously swarming with bees. This
appeared the more remarkable as the sky had become overcast with heavy
clouds, though the temperature registered about 76° F. In the intervening
rough pasture between the apiary and this orchard, bees were observed on
rhododendron and blueberry.
The next day bees were still abundant in this orchard, but, unlike the day
before, were much more evenly distributed, and also in the orchard contiguous
to the apiary. They were even found in measurable numbers in an orchard
| mile west, and small numbers were taken on buttercup, dandelion, oak, and
chokeberry, the weather, like that of the previous day, being generally quite
favourable for flight and activity.
(iii) Varietal Attractiveness. — A serious attempt was made to determine
whether or not different varieties of bloom vary in their attractiveness to bees.
Certain varieties that show few bee visitors on certain days, at others will be
found to have many such visitors for reasons indicated in the preceding section.
It is, therefore, dangerous to draw too sweeping conclusions without a great many
careful observations extending over the entire blossoming period. We are satisfied
that some varieties are more attractive than others; but definite proof is difficult,
owing to the fact that varieties cannot be compared on an equal basis — no two
being in exactly the same condition of attractiveness with respect to nectar
secretion, etc., when counts are taken — and varying weather conditions make
observations under identical conditions impossible. At the same time, certain
varieties are outstanding in this respect, notably Gravenstein, which always
gave large counts when in proper condition. The fact that few other varieties
are open when Gravenstein is in bloom would tend toward a greater concentration
on this variety. Gravenstein has also a showy blossom, comparatively good
150
nectar secretion and more pollen than most triploid varieties. Golden Russet
is another variety that seems to be favoured by both wild and hive bees and,
with both these varieties, blossom visitors seem to persist throughout the bloom
to a greater extent than with some others. Though Golden Russet has a much
less showy blossom than Gravenstein it produces an abundance of pollen and,
hence, is popular with pollen gatherers. Without much more careful work, how-
ever, it is not possible to be more definite regarding attractiveness of varieties.
It is worthy of note that certain varieties, e.g., Blenheim and Stark, seem to have
greater difficulty in getting cross-pollinated than other equally self-unfruitful
varieties, e.g., Spy and Cox Orange, under very similar conditions. The former
two varieties furnish comparatively small quantities of pollen, while the latter
are notable for the comparatively large amounts that they produce; this may
affect the number of insect visitors.
(iv) Effect of Masses of Bloom. — The foregoing sections emphasize the
important effect of the condition and nature of bloom in attracting bees. The
attractiveness, at certain periods of bloom of an orchard of Ben Davis trees was
particularly mentioned. Other Ben Davis trees, as well as those of other
varieties in a similar condition of bloom, were present in the orchard contiguous
to the apiary in question, though not massed to the same extent. The effect of
masses of bloom in a correct condition to attract bees has been noted on other
occasions. One orchard in which bees were placed for two different years was
situated at the base of the North Mountain and consisted of moderate sized
trees, mostly Baldwin, Stark and Blenheim. This orchard had been heavily
pruned and there was not present any great mass of bloom at any one time.
Seven colonies were present in the orchard which was of seven acres in extent
and, though we now know that this was insufficient for an area otherwise totally
devoid of bees, the fact that on many visits wre could rarely find any bees what-
ever in the bloom, was somewhat puzzling. During one of these visits in which
no bees could be detected, though considerable activity was observable at the
hives, an orchard J of a mile away was found to contain considerable numbers.
The second orchard was below the level of the first, was unpruned and generally
uncared for, but presented dense masses of bloom which gave off an aroma
distinctly noticeable to one passing along the adjoining road. Varietal attrac-
tiveness may also have been a factor in this particular case. The greater
attractiveness of larger masses is also evident in the difficulty, sometimes experi-
enced, of getting bees to visit orchard bouquets, since they definitely prefer to
go to the greater masses of bloom, other things being equal.
(v) Availability of Other Bloom. — Fortunately, since apples do not appear
to be as attractive to bees as many other species of plants, there are not usually
available at blossom time, other large sources of pollen or nectar. However,
there are a number of species of plants present in smaller numbers. On many
occasions, when it was difficult to find bees in the apple bloom, their presence
in large numbers on strawberries, Siberian pea, dandelions, etc., could be readily
detected. On one occasion, when careful search failed to reveal bees in appreci-
able numbers more than a quarter of a mile from the apiary on apple bloom,
they were counted in large numbers on a clump of rhododendrons one-half mile
away. In this connection another observation is of interest. An apiarist at
McBride, B.C., was the only one keeping bees in the district. Bees from this
apiary were noted working in a field of sweet clover four miles from the apiary,
though an abundance of alsike and Dutch clover was available in the intervening
territory. In districts in which little but apple bloom was present, the same
number of colonies should obviously give a greater field force for apple pollina-
tion than in districts in which a variety of attractive bloom was present. Apple
is certainly not the most-favoured plant; dandelions, rhododendrons and other
plants available during apple bloom being apparently preferred under ordinary
151
conditions. Hence, the more of such bloom in a given locality, the less bees
would there be available for apple pollination.
(vi) Physical Features. — The presence of hills, ravines, strips of woods,
etc., frequently affect the flight and concentration of bees used for pollination
purposes. One apiary, situated at the north of a large orchard, has a steep
bank at the rear. The result is that the greatest numbers of the field force from
this apiary fly due north across a meadow and a stream and work on the apple
bloom in the orchards about a mile away. It is difficult to predict how bees
will work in broken territory, but the influence of factors similar to those men-
tioned above, must be taken into account in deciding how bees are to be placed
in the orchard.
(vii) Weather Conditions. — The effect of weather conditions on flight and
concentration have been discussed at length elsewhere. Inasmuch as unfavour-
able weather limits the length and duration of flights, it is obvious that the
hives should be so distributed about the orchard as to ensure proper pollination
of all trees in times of unfavourable weather. Observations, made in 1932
particularly, substantiate the observations of other workers that, at such periods,
there is greater activity near the hives ; and that in brief periods of fine weather
there is a tendency to restrict flight and activity to points not far distant from
the colonies.
(viii) Area of Activity. — A factor that deserves consideration at this point
is the habit of bees of working in a limited locality. It is the testimony of a
number of careful students that pollen- or nectar-gathering over an area is not
indiscriminate ; but that bees tend to go to the same place and return to it, trip
after trip, until supplies are exhausted. The fact that pollination is usually
heaviest on the side of a tree next the pollinizer and that the effect is lost a
very few rows away has been often noted.
Minderhoud (1931) reviews the observations of other workers in this field
and presents his own experiments with marked bees on the flowers of Taraxacum
officinale Weber, Trijolium sp., Cruciferce, etc. He considers that his data
warrant the following conclusions: In visiting low growing plants and in the
absence of a strong wind the honey bee will for a long time visit one particular
place, the area of which does not ordinarily exceed 10 by 10 metres. Under
such circumstances, its successive visits are to flowers not farther apart gener-
ally, than one metre. He concludes that one can only expect to get full benefit
from bees, when different pollens are available to them, within a small radius.
Why this should be so is suggested by studies by Von Frisch (1924), which
indicate that odour from the scent glands of the workers of a given colony,
impregnating the spot visited, acts as a lure to other workers from the same
colony, but not for workers from another hive. Bonnier (1906), for example,
marked all the bees he found visiting a five-metre strip of buckwheat, and the
next day found only marked bees visiting the strip.
On several occasions during our experiments, certain colonies have shown
very severe poisoning, while others have shown little or none. A good example
of this was in 1929, when no severe poisoning could be detected in 49 colonies
placed in an orchard, but one colony showed poisoning of the most severe type.
It seems difficult to explain this fact other than on the assumption that the
bees from this particular colony secured poison from a common source. As a
matter of fact, a small plot not far from this hive had been dusted with sulphur
lead arsenate dust which may have furnished the source of the poisoning.
Similar evidence, with respect to the gathering of certain kinds of nectar bv
particular hives, will occur to any experienced beekeeper.
(ix) Amount of Bloom Available in Relation to Population Present.— The
amount of bee pasturage available in a given area, relative to the population
152
present, has a very important bearing on the distance of flight and the point
of maximum concentration. Thus, in a territory with small scattered orchards
and little other bloom available, we would expect them to go farther afield
than in a densely orcharded area during the period of bloom. Evidence is
available from Fort Vermilion, Alberta, vouched for by the Superintendent of
the Experimental Station and a Hudson Bay Company official at the place,
that bees from the Experimental Station, the only hive bees in the entire area,
were taken seven miles away at the Hudson Bay Company office. This, how-
ever, represents a condition quite different from that in the territory in which
our studies were made, where large blocks of orchard were everywhere present.
Our counts indicate that, up to a certain point, when the apiary strength is
increased, the bees range farther afield, as was the case in Somerset in 1932,
when 50 strong colonies were placed in an orchard with 44J acres of orchard
within a quarter-mile radius and 137 acres within a half-mile radius. Here, bees
were readily detected in appreciable numbers a mile away. Flight and concen-
tration are, therefore, affected by the number and strength of the individual
colonies and by the number of colonies available in any one place. This fact
is important when considering the number of colonies required to secure pollina-
tion in any given fruit growing area.
Various recommendations are made as to the number of colonies per acre
required to ensure adequate pollination of apple orchards. The majority of
these vary, from one colony to each four acres of young bearing orchards, to
one colony per acre for large trees. A few typical references at this point will
suffice for our purpose.
Hooper (1929) recommends one hive of bees to each acre of fruit trees,
especially in a district unsuitable for wild bees. DeOng (1925) considers one
strong hive to the acre as a sufficient pollinating force. Murneek (1930) believes
that one colony to every three or five acres will be sufficient for a young orchard
that has just come into bearing, but that older orchards mayNneed a hive per
acre. It is contended by Philp and Vansell (1932) that the usual recommenda-
tion of one hive per acre is more than necessary under some conditions, but
weather conditions so affect results that more would often be justified.
Certain recommendations would seem to assume either that bees stay in
the orchards in which they are placed, or else that all the orchards in the
immediate neighbourhood will have colonies at an equal rate. If we assume
that hives with an average field force of 15,000 bees are placed at the rate of
one to the acre in a ten-acre orchard of large bearing trees with contiguous
orchards surrounding it, aggregating 125 acres and that, under these conditions,
the bees spread out only in a quarter-mile radius from the colonies and also
assuming for the purpose of illustration that all trees are in bloom at once,
there should be present one bee for each 833 blossoms. If, however, we assume
that the total field force from the ten colonies was evenly distributed over
the ten acres, the figure would be one bee for each 66 blossoms. It is, of course,
realized that all blossoms are not out at once, that the distribution is not even
and that the bees may fly considerably farther than one quarter of a mile,
but the illustration will serve to stress the point that the bee population
of the surrounding area is an important factor in the utilization of bees in
orchards. The situation is quite different, in cases where contiguous orchards
are similarly supplied, from that created by the entire absence of bees in the
surrounding area. This fact was repeatedly observed during the course oi our
studies.
The writer, on one occasion in 1930, counted for two entire days in a ten-
acre orchard in which ten strong colonies were placed, without observing a
single bee working the bloom, conditions for flight and bee activity being i *
lent. Within a one-quarter mile radius there was a total of about 90 acres of
153
orchard spread over approximately 200 acres of land. The point selected was
225 yards from the colonies. Six counters, placed in the orchard at intervals of
from 3 to 225 yards from the hives, secured only an average of 0-37 bees per
10-minute count during the same period. In 1931, forty strong colonies were
placed in the same orchard equally divided between the two ends of the orchard,
the average counts giving a total of 0-62 per 10-minute count under very
similar conditions. It was thus necessary to use four times as many colonies
to get less than double the population in the bloom. Similar, or even more
pronounced results were obtained elsewhere when colonies were placed one to
the acre. The entire area in which our work has been done is heavily covered
with orchard and at most stations the number of bees determined by counts
was negligible. At Blomidon, in a fourteen-acre orchard with one colony per
acre, we obtained, in 1930, only an average of -22 bees per count. In this case
the bees were placed at the north end of the orchard, with a mountain at the
back covered by forest, while south and east of the colonies, stretched a solid
block of orchard surrounding the one in which the observations were made.
On the other hand, on Long island where we had approximately 90 acres
geographically isolated from other orchards and situated on a total land area
of 640 acres, and with colonies present at the same rate, we had an average
of 1-23 bees per count in 1931. In 1932, with stronger colonies and not more
than 60 per cent of the bloom, our average count was 3-05 bees. Thus, on
Long island, with one colony per acre of orchard, there were many more bees
available for pollination than at Lakeville with four colonies per acre, since in
the latter location the contiguous orchard area was unprovided with bees. In
1932, immediately before using them on Long island, 50 strong colonies were
placed in an orchard at Somerset where 92 acres of orchard, within a half-mile
radius, were at their maximum bloom. Here, in the orchard immediately con-
tiguous to the hive, we secured an average count of 5-53 bees. This average
is based on a 2-day count of optimum flight, whereas the Long island count
is based on the period of bloom. The foregoing clearly indicates that, in making
recommendations for placing hive bees in an orchard, it is necessary to consider
not only the acreage of the particular orchard in which" the bees are placed, but
also the area of surrounding orchards and whether or not they are provided with
bees. In other words, the district and not the orchard must be considered the
unit for calculating the force necessary.
Our observations indicate that there must be a certain minimum popula-
tion present under such conditions before a sufficient concentration of bees, in
the particular orchard in which they are placed, can be assured. This minimum
on the basis of our observation is about fifty colonies in an area solidly planted
to fruit trees. In other words, if ten colonies are used to pollinate an orchard
of ten acres, surrounded by 90 acres without bees, this would not necessarily
ensure the pollination of that particular orchard which would require in the
neighborhood of fifty colonies in order to ensure results.
With a population sufficient to give an average of one bee per 10-minute
count, it has been estimated that each bee would be required to pollinate 250
blossoms in order that every blossom in the orchard, in a year of maximum bloom,
should be visited. Coming again to Long island where conditions were more
under control, we find that the counts taken over the whole island in 1931, a
year of maximum bloom, amounted to 1-27 per count during several days of
bloom and in 1932, with approximately 60 per cent of the previous year's bloom,
3-05 per count. Placing the lowest possible estimate on the number of blossoms
that a colony of bees is capable of visiting, it would appear that one colony
per acre, under conditions of isolation, would represent a population much
greater than the number theoretically necessary. If our record of 3-05 bees
per count, representing the force liberated by a strong colony with a field force
of 15,000 bees or upward, is representative, even supposing that only 25 to 50
154
per cent were effective pollinators, it is obvious that each bee would have
to visit only a comparatively small number of blossoms in order to pollinate the
whole orchard. In considering this problem, allowance must be made for dupli-
cate visits, proportion of nectar gatherers to pollen gatherers, etc. Though, in
order to ensure pollination under unfavourable conditions, it is necessary to
supply a much larger force than is theoretically necessary, it would appear that
one hive to the acre of bearing trees should be quite adequate, even after all
allowances are made.
In recommending a certain force per acre it should be emphasized that
such recommendations only apply, in the case of areas heavily planted to
orchard, where neighbouring orchards are similarly supplied. Colonies, set out
at this rate in small blocks of orchard surrounded by hundreds of acres destitute
of bees, spread out so thinly as to make them of doubtful value for pollination
purposes. This point is particularly emphasized, because many growers in dis-
tricts where no hive bees at all are present, consider it sufficient to use only a
very few colonies, sometimes no more than one or two in a large orchard.
(x) Method of Placing. — Most studies that have been made with respect
to the method of placing colonies in or about orchards, have had to do mainly
with the problem of the best method of placement to follow in order to secure
uniform distribution. There appears to be a wide difference of opinion between
different workers as to the proper method of distributing the colonies.
Data secured by Hutson (1926) were said to indicate that the bees worked
most freely near the hives and that by placing hives singly 210 feet apart
each way and 15 feet from pollinizing bouquets, maximum results were secured
and there was a uniform distribution of bees in the orchard. Counts show con-
centration about hives placed in groups, and the numbers diminish as distance
from the hive group increases. Haseman (1932) states that colonies should be
scattered through the orchard since, in cool weather, bees will not fly far.
Marshall, Johnson, et at. (1929) emphasize the point that colonies should be
placed near effective pollinizers. Murneek (1930) recommends that the hives
should be distributed throughout the orchard and not kept in one sheltered
corner. Within a heavily bearing orchard the greatest service will be secured
when the colonies are placed 200 feet apart.
Philp and Vansell (1931) have a different idea as to the proper placing of
colonies. They state that under ordinary conditions bees should be left in
orchards in groups of 10 colonies. They point out that sunshine, wind, temper-
ature, rain, and other factors outside the hive, affect the flight of bees and there-
fore general recommendations regarding placement are useless. If the weather
is fair, bees can fly far enough to cover 100 acres of orchard, or more, from one
location; but in cold weather flight is limited. They state that, under average
conditions, bees in groups of 10 to 20 colonies, for as many acres surrounding
them, have been found very satisfactory. Accessible situations should be chosen
to facilitate placement and removal.
It was determined in our tests that, in a densely orcharded area supplied
with colonies in groups, but at the rate of one per acre, little consistent differ-
ence occurred up to about 660 feet from the colonies; but after double this dis-
tance had been reached counts became definitely lower and beyond one quarter
of a mile few bees were found. Since it is sometimes more convenient, both in
placing and removing colonies, to distribute them in groups rather than singly
throughout the orchard, it would appear to be satisfactory to have the colonies
placed in groups one-quarter mile apart, having regard to the contour of the
land and the other factors already discussed.
After experimenting for three seasons on methods of distributing colonies
without being able to distinguish any great difference between colonies distributed
singly and in groups, we arranged to carry out this latter plan on Long island
155
in 1932. The island being 2 miles long, the extreme colonies were placed approx-
imately one-quarter of a mile from each end, and the remainder at approximately
one-quarter mile intervals, there being 3 apiaries of 15 colonies and 3 apiaries of
16 colonies, or approximately one per acre of orchard. As there was a different
number of counts on certain of the days, the data for June 2, June 3 and for the
average count for June 4, 5, and 9 taken together, are presented. Counters were
placed at the extreme ends of the island and midway between each of the apiaries,
also at the two extreme apiaries and the centre apiary. While the error due to
the human element in these counts may be large, it was apparent that the greatest
number of bees was rarely present in the orchard adjacent to the apiary, and at
all times the large number present at station " Y " was noticed by all observers.
It would not appear, therefore, that the placing of colonies singly and evenly
through the orchards could ensure an even distribution of bees, when the foregoing
facts are considered. It would seem to be equally effective to place the colonies
in groups at suitable intervals, with due regard to the position of orchards and
the surrounding physical features, as good, or even better, distribution was
obtained by placing groups of colonies at one-quarter mile intervals as by
placing them singly in the orchard, though nothing like perfect distribution was
ever obtained by either method. The habit of the bees of working nearer the
hives during unfavourable conditions would render it inadvisable to place the
colonies at greater intervals than that indicated. The accompanying table shows
the results of counts made at the various stations on Long island.
TABLE 27.— AVERAGE COUNTS OF BEES FROM DIFFERENT STATIONS ON LONG ISLAND, 1932
Average for June 2
Average for June 3
Average for June 4
5 and 9
Station
Hive
bees
Wild
bees
Number
of obser-
vations
Hive
bees
Wild
bees
Number
of obser-
vations
Hive
bees
Wild
bees
Number
of obser-
vations
Z
9-09
4-78
13-85
9-35
6-54
0
0-33
7-25
10-90
8-28
5-93
1-34
3-OG
7-27
2-39
2-85
0-29
0-5
5-71
2-56
1-27
1 61
*
41
41
41
41
13
7
6
41
41
41
41
0-59
0-88
0-76
0-61
0-22
0-08
0
0-45
0-59
0-26
0-82
2-76
0-85
0-78
1-93
0-29
0-30
0-08
0
2-64
0-66
0-18
0-62
0-92
85
1
85
A..
1-46
2-62
5-54
0
0-31
0-08
13
13
13
85
B...
85
C
27
12
12
4
85
D
16-75
4-61
015
0
13
13
85
E
85
6
85
Y....
*
*
*
85
*No regular count on these dates but observations indicated bees to be abundant.
Where the apiary is situated near the orchard and permanent in position, it
should be located with reference to the contour of the land so that the maximum
number of bees will work in the orchard and not fly out of it. Steep banks in the
neighbourhood of the orchard, or intervening belts of trees may, deflect the usual
line of flight as already explained. With the apiary in a permanent location
near the orchard the distribution of colonies throughout the orchard occasions
loss. At the Experimental Station, Kentville, it was found that the colonies
were much weakened by bees returning to the original stand, though a few weak
colonies left behind to catch " drifters " was of benefit. When the colonies were
returned to the original stand, bees that had emerged during the interval spent
in the orchard, returned to the spot where their hive had rested, clustering on
the spot for days, stinging all who approached. On the other hand, no such
trouble was experienced from two apiaries each distant about a mile from the
original stand.
(d) TIME OF PLACING
As regards time of placing, most workers state that best results can be
expected when the bees are placed in the orchard only when the trees come into
bloom and removed when the majority of the petals have fallen. There is an
156
added reason for doing this when danger of poisoning is to be anticipated. Our
experience has been that this danger is materially lessened, though not necessarily
eliminated, if the practice outlined above is followed, and it appears to be a
sound one from every point of view.
(e) SOURCE OF POLLEN SUPPLY
Bees are useless in the orchard without a suitable pollen supply, a fact
which appears to be often overlooked by growers. In fact it is quite conceivable
that some harm may result. Bees placed in a block of self-unfruitful varieties
may only result in rapidly selfing that variety, thus inhibiting a certain amount
of crossing that might occur through the agency of wild species of bees before
the period of stigma receptivity has passed. On the other hand, if cross-unfruit-
ful sorts are mixed together, the pollination of the varieties concerned with the
pollen of the other, may result in even less fruit than when certain varieties are
selfed. Therefore, the proper provision and distribution of effective pollinizing
varieties of apples is equally important to that of the insect pollinators and is
something that is under the control of the owner who sets out the orchard.
The problems connected with the foregoing, however, have been discussed
in detail elsewhere. In our work we have found the question of providing a
suitable pollen supply of more practical importance than the provision of bees
alone, and even using " bouquets " of fruitful varieties in connection with bees
has usually been disappointing.
3. SECURING COLONIES
Three methods of using bees are suggested by DeOng (1925), as follows: —
1. Rental from a professional beekeeper.
2. Employment of a trained beekeeper to care for bees owned or leased
by one or a group of orchardistv
3. Ownership and personal care.
The two first methods are considered best, as the orchardist usually has
neither time nor knowledge to care for the bees properly. The difficulties of
the average fruit grower are increased, under Nova Scotia conditions, on account
of the evidence of poisoning, which may cause the beekeeper, and particularly
the inexperienced beekeeper, to lose all his colonies, or to have them become
so weakened as to be worthless for pollination purposes.
At the present time there is no one in the business of renting colonies to
beekeepers in this province and there are not available a sufficient number of
colonies to supply any real demand. Packages can be obtained from the South
at the rate of from $1.75 to $2.75 for 2-pound packages, depending upon the
source and number purchased at one time. Similarly, 3-pound packages will
cost from $2.25 to $3.50; 4-pound packages from $2.75 to $4.25, and 5-pound
packages from $3.50 to $5 each. Then, transportation charges will have to be
added to the foregoing prices, and with proper care and attention, these pack-
ages can, if purchased sufficiently early, be put in condition to be of some
service during bloom. The price asked by commercial beekeepers for strong
overwintered colonies varies considerably in different fruit growing districts.
As already stated, renting bees has never been practised in Nova Scotia, except
in a few isolated areas, and accordingly few figure- are available, but the risk
of poisoning would probably force a maximum price.
Farrar (1929) states that in Massachusetts, beekeepers feel that they should
receive from $5 to $10 per colony. This writer suggests s;> ;is a fair price for
a colony covering 5-6 frames, deducting $1.50 for each frame less, and adding $1
for each frame in excess of 5 or 6 combs. Marshall, et al. (1929). in Michigan,
states that $2.50 to $3 per colony is the regular price in that state. Phillips (1930)
claims that labour and other inconveniences bring the cost to the beekeeper to at
least $5, but, at this price, beekeepers find that they cannot do the work or take
157
the necessary risk. He states that as high as $10 per colony has been charged
for rent. Philp and Vansell (1932), in California, emphasize the fact that the
rental charged will depend upon distance of moving, state of roads, rainfall, supply
and demand, etc., but that at the present time, $2 will represent about the average
price. Another possible method that has been suggested is for a group of
orchardists to co-operate in securing colonies and engaging a beekeeper to tend
them.
4. GENERAL CONCLUSIONS
While various causes prevented the complete carrying out of our studies as
originally planned, the following conclusions seem justified on the basis of our
investigations:
(a) It is generally recognized that the provision of hive bees to ensure
pollination in apple orchards is a sound practice; but the experimental evidence
in its favour is not so clear-cut as in the case of certain other fruits. In certain
seasons, in some localities at least, adequate pollination is effected by native
solitary bees.
(b) Where this condition does not obtain the provision of a suitable number
of colonies should be practised as a part of the regular orchard routine and.
even in cases where solitary bees may be adequate for pollination in favourable
years, the placing of colonies in the orchard may be regarded as a wise insurance
against seasons when conditions are unfavourable.
(c) Experimental evidence regarding the value of bees for pollination pur-
poses under controlled conditions demonstrates clearly the necessity of bees
combined with a supply of suitable pollen for all varieties. Even the most self-
fruitful varieties require bees in order to ensure adequate pollination.
(d) Many factors, including colony strength and number of colonies in
relation to the adjacent orchard area, the physical features of the area con-
cerned, weather conditions and many others that have been discussed in detail
in the foregoing pages, influence the flight, concentration and distribution of bees.
(e) The point is particularly emphasized that, in estimating the number
of colonies per acre of orchard, the surrounding district and not the individual
orchard should be considered the unit. The placing of a few colonies in an
orchard area devoid of bees does not necessarily ensure the pollination of the
particular orchard in which they are placed, since they may work mainly
in another orchard or spread out too thinly over surrounding orchards to be of
great value. The recommendation of one to the acre or one to four acres has
little meaning, unless it is known that the surrounding area is similarly pro-
vided. Under conditions of isolation, or where neighbouring orchards are also
provided with bees, one colony to an acre of mature trees should make adequate
provision for pollination, even allowing for considerable unfavourable weather.
(/) Bees should be placed throughout the orchard area in such a way as
to ensure as good distribution as possible and thus take advantage of short
flights that may occur at intervals between periods of bad weather. Placing
colonies at the rate per acre indicated, but in equidistant groups of from 5 to
15, depending upon the area in orchard, is regarded as satisfactory. Further
details are given in previous pages.
(g) It is best to place the bees in the orchards when the earliest varieties are
in full bloom and remove them before the petals have fallen from the later
varieties.
(h) The proper distribution of cross-fruitful varieties in an orchard is a
primary requisite to successfull pollination; without such provision, placing bees
in the orchard only results in unfruitful selling or crossing.
(i) Colonies may be rented from a beekeeper or they may be owned and
cared for by the orchardist; but unless the latter is skilled in the care of bees,
the former method is usually preferable. Another method suggested is for a
group of orchardists to co-operate and hire a skilled beekeeper.
V. STUDIES IN BEE POISONING AS A PHASE OF THE
ORCHARD POLLINATION STUDIES
By F. A. Herman and W. H. Brittain
A. INTRODUCTION
Owing to the importance of the evidence of poisoning among bees, in any
consideration of their use for pollination purposes, the following studies were
undertaken as an integral part of a pollination project undertaken by the
Dominion Department of Agriculture in the Annapolis valley, N.S., during the
years 1928-1932 inclusive.
In carrying out this work the writers have had invaluable assistance from
Mr. C. B. Gooderham, Dominion Apiarist, in the way of active assistance and
advice. A number of the photographs used in this report were also furnished
by him. Mr. Evan Craig, Apiarist at the Experimental Station, Kentville, has
given freely of his time, not only in caring for the bees used in the work, but
also in helping with the actual work of the investigation. Mr. H. G. Payne,
Provincial Apiarist, Truro, took an active part in the field studies and was of
great assistance through his local knowledge of the industry.
B. HISTORICAL
Ever since the dawn of modern spraying practices, complaints of losses of
bees from arsenical poisoning have been heard with increasing frequency, and
laws prohibiting the applications of sprays during bloom have been passed by
several states and provinces.
A number of chemists and entomologists have given the matter attention,
and, while a complete review of the literature would be out of the question in
the space available, a few of the more important contributions may serve to
give a picture of the present state of knowledge with respect to this problem.
A more complete review has been given by Mclndoo and Demuth (1926).
Webster (1896) was one of the earliest workers to conduct definite experi-
ments in connection with this problem. Paris green, 4 ounces to 50 gallons
of water, was sprayed on a Lombard plum tree in full bloom at 2 p.m., the
quantity of the mixture applied being just sufficient to wet thoroughly without
dripping. The tree was enclosed in canvas and mosquito netting; 5^ hours
after spraying a hive of bees which had been placed near the tree some two
wreeks previously, was moved into the tent and the bees liberated. The follow-
ing morning many dead and dying bees were found on the tent floor. The dead
bees were examined by the Marsh method for arsenic, and yielded positive
results. Further tests from washed bee- were also positive. Several days later
many more dead bees were picked up, and after washing, first with water, then
with a weak solution of ammonia, were analysed and showed the presence of
arsenic. A small apple orchard, from which the bloom had all fallen except a
belated cluster, was sprayed with Bordeaux mixture, to which had been added
Paris green at the rate of 4 ounces to each 50 gallons. A few days alter this
application, three previously strong colonies of bees located nearby suddenly
became depopulated. Analysis of dead bees and dead brood showed the presence
of arsenic. Conclusions drawn from these experiments are as follows: Bees
are liable to be poisoned by spraying the bloom oi fruit trees, the liability
158
159
increasing in proportion as the weather is favourable for the activity of the
bees, and all the bloom must have fallen from the trees before the danger will
have ceased.
Price (1920) conducted laboratory and field work to find out the amount
of soluble arsenic necessary to kill a bee, to find out if a bee working upon a
mixture of insoluble arsenic and syrup would take up the arsenic particles, and,
if the dead bees contained arsenic internally. A small amount of arsenic of
less than -0000005 grams of As205 is a fatal dose for a bee and the longevity
of bees poisoned with arsenic was found to depend upon the size of the dose.
It was also found that a bee takes up lead arsenate particles in feeding on a
sugar solution having them in suspension. An examination of dead bees from
laboratory or field experiments showed arsenic to be present both internally
and externally. It was found that bees worked freely on sprayed trees in the
open, even when there were unsprayed trees all about and that trees sprayed
while in blossom contained sufficient poison to cause a tremendous death rate.
The mortality of bees in the control cage was 19 per cent, as compared with
69 per cent in the cages containing the trees sprayed with lime sulphur and
lead arsenate, and 48 per cent in the cage containing the tree dusted with sulphur
and lead arsenate.
Doane (1923) described a number of experiments conducted at Stanford
University. An apple tree almost in full bloom was sprayed with arsenate of
lead, 3 pounds of the poison to 50 gallons of water, and applied at the rate of
8 gallons of the spray per tree at a pressure of from 150 to 200 pounds; special
effort was made to fill the calyx cups as far as possible. The tree was then
tented and two days later a moderately strong colony of bees was placed beside
the tree. Before liberating the bees on the following morning, 2 gallons more
of the spray were applied to the tree in the form of a fine mist so as to cover
the leaves and petals. Shortly after being liberated, some of the bees visited
the blossoms and by noon scores of them were feeding freely. Three days later
the colony was returned to the apiary and, on examination, the bees were found
to be working normally, that honey had been stored while working the sprayed
bloom, that the larvae were in a normal condition and that the queen had been
laying eggs. During the three days the bees had been feeding on the poisoned
bloom only a few had died which on examination showed -00000255 grams of
arsenic per bee. The bees that were collected while still living showed -000002
grams of arsenic per bee. Bees from the check tent contained -0000006 grams
of arsenic per bee.
These experiments were repeated several times with other colonies and no
abnormal effects noted. In a later experiment a tree just coming into bloom
and in which bees were feeding was sprayed with dry acid lead arsenate, 4
pounds per 50 gallons. While most of the bees were driven away by the spray,
they returned within ten minutes after spraying was stopped. The weather
was warm, favourable for the activity of the bees. No poisoning was observed.
An examination of the hive showed that the bees and brood were in good con-
dition and that the bees had stored honey during the time they fed on the treated
bloom.
The conclusion arrived at is that there is no danger of poisoning bees by
spraying fruit trees when they are in bloom, a procedure that is common in
certain parts of California.
Merrill (1924) criticises the methods employed by Doane and concludes
that the work of Price is more scientific and the results more likely to be
correct.
Tietz (1924) has studied the question of the solubility of arsenate of lead
in the digestive fluids of the honey bee. He points out, that in order that a
poison may be absorbed by the body and so cause death, it is necessary that
160
it should be in a soluble form. When arsenate of lead is taken into the alimen-
tary tract of an insect, it is very insoluble. The average arsenate of lead powder
contains about 32 per cent arsenic pentoxide, and as the insect consumes but a
small quantity of the spray, the solubility must increase when the powder comes
in contact with the digestive fluids in the alimentary tract; otherwise the quan-
tity of arsenic capable of assimilation would be so small that the insect would
be unharmed by its presence in the blood.
The solubility of arsenate of lead powder in water was taken as the unit
of solubility. The following conclusions were drawn from the experiment: (1)
The solubility of arsenate of lead does not seem to increase when the powder
is acted upon by the fluids in the oesophagus. (2) The digestive secretions of
the honey stomach and stomach render the poison at least one and one-quarter
times as soluble. (3) The action of the intestinal juices is to throw at least
three and three-quarter times as much of the powder in solution as would be
dissolved by water alone.
Mclndoo and Demuth (1926) have conducted careful and extensive experi-
ments upon the effects on honey bees of spraying fruit trees with arsenicals.
They also give an excellent review of work carried out up to the data of publica-
tion. Experiments at Winchester, Va., in 1914, in which 3 small isolated orchards
in bloom were sprayed with (a) Paris green, (b) lead arsenate and (c) lead
arsenate and lime sulphur, brought out the following points: (1) Bees work as
well on sprayed as on unsprayed bloom; (2) they do not fly away very much
from the sprayed orchard if it is well isolated; (3) they are slightly affected
when a small orchard is sprayed in full bloom; and (4) the arsenate of lead-lime
sulphur mixture was found best for experimental purposes. Larger experiments
conducted the same season in a large isolated commercial orchard at Winthrop.
Me., using the latter mixture, caused serious losses to the bees, pollen proving to
be the main source of poisoning. While never more than traces were found in the
partially ripened honey, chemical analysis of the nectaries revealed traces of
arsenic. None of the ten colonies used was killed outright, but five were
depopulated in a very short time and five were weakened. The foregoing results
were obtained by daily observations, the use of dead-bee traps and analyses
of samples. In later experiments a method was followed whereby the actual
weight of the bees could be determined daily. Experiments conducted when
the trees were sprayed at the ordinary time, i.e., when 90 per cent of the blossoms
had fallen, gave little or no poisoning. Laboratory experiments established that
a fatal dose of arsenic (As) per bee is about 0-0004 or 0-0005 milligrams.
Hilgendorff and Borchert (1926) describe observations in which the applica-
tion of arsenical compounds, by aeroplane, to forests for the control of the " fir
noctuid " moth and " nun" moth caused a serious bee mortality to the Sorauer
beekeepers and claims for damages were instituted. Chemical analysis of the
bees snowed living bees to contain -00015 mg. of arsenic; washed dead bees.
•00025 to -004 mg.; pollen, -0001 to -0005 per cent, while bees, pollen and honey
from districts not subjected to arsenical preparations contained no arsenic. The
quantities of arsenic in the pollen were quite sufficient to cause bee mortality, as
shown later by feeding experiments with sugar solutions containing arsenic in
proportion to that found in the pollen.
Bourne (1927) presents considerable experimental evidence with respect to
the poisoning of honey bees by orchard sprays. Experiments were conducted
to ascertain whether bees were attracted or repelled by common spray mixtures,
and whether the latter had any injurious effect on the bees. First, a single frame
nucleus in an observation hive was fed for a few days on dilute honey, then
on a mixture of honey, one part, and spray mixture < lead arsenate, lime sulphur
and nicotine sulphate) one part. They readily accepted the honey, but were
repelled by the mixture. Only a few fed on it and these, after being isolated.
161
died in 24 hours. When only lead arsenate was used they showed no reluctance
in feeding. The colony was exterminated after feeding on the last mixture for
nine days. A combination of lead arsenate, lime sulphur and honey was also
accepted readily; in fact, the nicotine sulphate seemed to be the only repellent,
as all combinations not containing it were eaten freely. All three substances
proved toxic, lead arsenate the most so, and the combination of all three was most
deadly. A three-frame nucleus with eggs, brood and some stores was then placed
in a greenhouse, and supplied with bloom sprayed with the regular spray com-
bination. The bees were repelled by the sprayed bloom, but still worked it in
considerable numbers. The mortality rose to about 390 per day within three
days after exposure to sprayed blossoms, whereas it had been from 7 to 63 per
day, before. A normal ten-frame colony was then placed in an orchard which
was sprayed with a combination of lead arsenate, 1\ lbs. to 50 gallons, lime sul-
phur, 1-40, and nicotine sulphate 1-1000 when the centre blossoms had just
opened. Bees which actually worked the bloom were poisoned, but owing to the
repellent action of the spray and the rapid opening of unsprayed blossoms, dam-
age to the hive was negligible. An early calyx spray gave the same result.
Another colony was placed in a tent, which was erected over a 12-year-old
peach tree. After being left for a few days and when considerable bloom had
opened, the tree was sprayed with the combined spray; another application was
made at full bloom. No high mortality was noted except following a spray of
lead arsenate alone. Unfavourable weather conditions which prevented the bees
from working may have been partly responsible.
Under conditions in Massachusetts, the orchard sprays applied nearest the
period of bloom are the " pink " and the " calyx." No sprays are scheduled to
be made when trees are in full bloom. Neither of these sprays, made when there
was considerable bloom on the trees, caused any serious mortality of colonies
located in the sprayed orchards. Following the " late pink " trees soon came into
full bloom; after the " early calyx," the bees repelled by the spray doubtless
foraged in neighbouring orchards. In both cases they found an abundance of
unpoisoned bloom upon which to work. This would indicate that improper
spraying must be carried out on a large scale visibly to affect colonies not sub-
ject to any restrictions of flight.
Borchert (1930) has investigated the action of copper compounds commonly
used, both sprays and dusts, also copper sulphate and basic copper carbonate,
on bees. The poisonous effect was found to be less, the more firmly the substance
clung to the bee's body. Poisoning was through the mouth in all cases; evidently
the bees swallow the substances in cleaning themselves, and are not so likely to
be poisoned if they cannot easily remove them. The lethal dose for a bee was
found to be equivalent to about 0-009 mg. of metallic copper. (Thus, dust or
spray substance containing one pound of metallic copper would suffice to poison
about 53,000,000 bees.)
Philp and Vansell (1932) state that spraying fruit trees results in con-
taminated nectar and pollen, as well as cover crops. Bees also drink poisoned
dew from leaves, so that even careful spraying cannot entirely eliminate poison-
ing, particularly where cover crops exist.
C. DEVELOPMENT OF PROBLEM
Previous to 1916, we have little evidence regarding the condition of the
bee industry. In that year a total of 70 apiarists were visited in the territory
to which our studies have been largely confined, i.e., the area bounded by Grand
Pre on the east and Berwick on the west. No further survey was made until
1919 when only 58 were visited, mostly those that had been visited before.
Thus, we have no records previous to 1916, and only incomplete records for
the years 1916 and 1919. We cannot now determine, therefore, all the apiaries
60796—11
162
that were in existence at that time nor the subsequent history of all of these
apiaries, but we now have accurate knowledge of the number at present exist-
ing and can trace the history of the great majority.
Of the total number of farms known to be supplied with bees in 1916-1919,
fifty-nine had none in 1930. Of the remainder, one represents the Experimental
Station apiary, which has only been kept in existence by the most assiduous
care; at least two are known to practise migratory bee-keeping and eleven are in
the towns of Wolfville and Kentville where poisoning, as would be expected, is at
a minimum. One man who formerly had twenty colonies now has three. With
these exceptions all others have disappeared. The apiaries that have been
wiped out include some that were the largest in the Valley, one having once
contained 100 colonies and one 40. The only apiarists who operate on anything
approaching a commercial scale have been obliged to adopt migratory bee-
keeping. The above would indicate a mortality much greater than would be
expected from normal causes, especially as the matter of foul brood among the
bees has been kept well in hand.
From time to time new apiaries have sprung up, and it will be interesting
to note what happened to them. Excluding the towns, the Experimental Sta-
tion and the migratory beekeepers, we find that 16 beekeepers are recorded
for the first time in 1920. Fourteen of these apiaries were out of existence
in 1930; one consisting of three colonies, was maintained at that strength; one
of twenty-five was reduced to eight and some packages had been obtained by
purchase. Figures for other years might be given, but they tell the same story.
There is, no doubt, a large mortality among bees, due to various factors
of which the most important is lack of efficient handling. The history of bee-
keeping in the Valley, however, shows large losses among the most experi-
enced apiarists; and apiaries that had been maintained successfully for many
years previous to 1919, were suddenly and completely wiped out. In the great
majority of cases the evidence points unmistakably to poisoning. The only
beekeepers retaining apiaries of commercial size have practised the removal
of their colonies throughout the danger period.
It would not appear to be a coincidence that this extermination of colonies
took place during and following the year 1919, since this was the year in which
the Valley fruit-growers suddenly adopted dusting, a large proportion of the
orchards in the Valley being dusted for the first time in that year and for sev-
eral years following. The figures of growers' purchases of such materials for a
few typical years reveal this very sudden change in practice. They also reveal
the increased quantity now being used to cover the same acreage.
It should not be assumed, however, that no trouble from poisoning existed
before that period. While it is true that we have few definite records on this
point, it is also true that many beekeepers regarded poisoning from sprays
applied in bloom as one of their greatest sources of trouble. Nevertheless, many
of them who were quickly wiped out following the widespread adoption of the
dusting method, had been able to maintain successful apiaries for many years
in spite of occasional poisoning.
The increased amount of poisoning from the dusting method has been gen-
erally attributed to three causes: —
1. The greater drift of the dust to surrounding vegetation, which thus con-
taminates other bloom such as dandelion, wild radish, etc., growing in or near
the orchard.
2. The greater amount of arsenic applied per acre when following this
method.
3. The difference in the character of the deposit. Spray quickly dries on
and is difficult to remove. Dust makes a loose layer over leave- and blossoms,
is gathered by or becomes attached to the hairs of the bee and is stored with
the pollen.
163
With the development of more efficient spray machines and nozzles deliver-
ing a greater quantity of spray per minute and the recognition of the fact that
dusting was giving inferior results against certain pests, there has come a
decided swing back to the spraying method during the past four years. As far
as can be determined there has been a sale of approximately 90 spraying out-
fits per year over this period as compared with approximately three dusters
and the latter have been used largely to supplement spraying practices in the
way of additional fungicide applications or for the application of nicotine dust.
The new types of spraying nozzles, however, deliver quite a different type of
spray from that of the old type, being more in the form of a fog, which drifts
on to surrounding vegetation to a greater extent than could occur where old
style nozzles were used. Furthermore, the greater number of gallons used and
the increased strength employed by many growers are added factors. It is
not surprising, therefore, that indications of greater poisoning of bees, clue to
spray applications have become apparent during the past few years.
The foregoing is only intended as a general outline of the situation, in order
to serve as a background for the more definite observations and experiments car-
ried out since 1928.
D. EXPERIMENTS IN BEE POISONING
1. FACTORS INVOLVED IN CARRYING OUT AND INTERPRETING
RESULTS OF POISON STUDIES
There are a number of difficulties inherent in both tent and field experiments
with bees that render it difficult properly to plan such experiments, and still
more to interpret their results.
It is a comparatively easy matter to feed bees upon definitely measured
doses of various materials in the laboratory, but to secure similar results under
tents or in the open orchard is quite a different problem. Some of the most
important difficulties are here set forth in order clearly to portray the limitations
of such work.
(a) In experiments carried out under tents covering trees, certain unnatural
conditions develop. Immediately bees are released, a large number fly to the
top of the tent and remain there in spite of all attempts to dislodge them. There,
a number may become chilled or die of starvation and keep dropping down on
the floor of the tent, interfering with the counts of dead bees. This trouble is
most apparent when periods of dull, cool weather prevail. Clustering at the
top may be partially prevented by covering the tops with a dark sheet.
Since the bees are forced to feed upon the treated bloom, the results obtained
are liable to be accentuated over those that would occur under field conditions.
At any rate, they are not strictly comparable, though, if correctly interpreted
in the light of all relevant factors, they may yield results of value. Another
disturbing factor is that during periods of rainy weather, the bees will lap up
the water that drips from the limbs or trunk and thus consume considerable
quantities of the material supplied, dissolved or suspended in the water, which
they might not do under out-of-door conditions. This results in materials not
ordinarily considered violently poisonous, sometimes causing a high mortality.
Residue from previous sprays, may, under such conditions, cause certain losses.
(6) In field experiments it is equally difficult to control the conditions of
the test. Several workers speak of their experiments being conducted in
" isolated " orchards. We have been quite unable to obtain isolated orchards
for our work, since in every case, there are other orchards sufficiently near for
bees to visit, and one could never be certain that the results noted were caused
by materials applied in the orchard in which the bees were placed or obtained
from a distance.
60796— 11 J
164
The habit of bees gathering supplies from a limited area has been clearly
brought out in these experiments. An example might be cited of a case observed
at the Experimental Station in 1929. Only one colony of the fifty showed
distinct signs of poisoning and in this case the loss was heavy. The orchard
was sprayed while there was a certain amount of bloom, mostly with lime
sulphur-calcium arsenate. However, there were a few small plots devoted to
spraying and dusting experiments, one of which had received 90-10 sulphur-lead
arsenate dust. Evidently this colony obtained its supplies from a location differ-
ent from the other bees and it may have foraged chiefly on this block. In
several cases where numbers of hives were standing together certain individual
colonies showed much worse poisoning than others, irrespective of colony strength
or other factors.
(c) In both field and tent experiments the condition of the colony is
important. It is impossible to secure colonies of identical strength and vigour.
Some were noticeably " sluggish ", worked the bloom less actively, and so
received less poison. The results of varying weather conditions profoundly
modify the results of both tent and field experiments. These are discussed at
greater length in another section. It is sufficient to point out that very erron-
eous results are obtained if this factor is ignored.
2. POISON USED, SYMPTOMS AND LETHAL DOSAGES
(a) Of the spray materials used in Nova Scotia the following are the most
important: —
(i) Food Poisons:
Calcium arsenate
Arsenate of lead
(ii) Contact Poisons:
Nicotine sulphate (liquid)
Nicotine sulphate-lime (dust)
(iii) Fungicides:
Bordeaux mixture
Lime sulphur
Sulphur dust
Copper lime dust ("Bordeaux dust").
Various combinations of these may be used, the fungicides generally having
the arsenical added, and frequently representatives of all these groups are mixed
together. Experiments under tents and in the field with these and all com-
binations used commercially were carried out.
(b) SYMPTOMS AND EFFECTS OF POISONS
(i) Arsenical Poisons. — The results of arsenical poisoning in whatever form,
are most apparent. " Crawlers " soon appear in front of the hive, their limbs
appearing to be partially paralyzed. Clumps of bees often cluster together in
bunches. The abdomen becomes distended and when subjected to pressure read-
ily bursts. A pronounced dysentery is often apparent, the hives becoming badly
spotted. This effect is most pronounced when the arsenic is contained in a
sulphur preparation. After a period of crawling, twisting and squirming, the
poisoned bees gradually become immobile and only feebly respond to stimulation
for some time before death ensues.
It was a notable fact that none of the " crawlers " taken in front of poisoned
hives had pollen in their pollen baskets. They evidently entered the hive and
came out to die after having gotten rid of their load.
165
(ii) Nicotine. — Certain cases of nicotine poisoning under field conditions
are not available. As nicotine quickly volatilizes and, when applied as dust,
is usually used at night or early morning when no bees are flying, heavy mortal-
ity from this source would not be expected. In tents, in which heavy dust
applications were made, bees sometimes became completely covered with the
nicotine lime dusts and some poisoning developed. In some years trees sprayed
with this material also produced killing. Definite feeding experiments performed
by other workers are available. It would appear that symptoms caused by this
poison are not as violent as those produced by arsenical sprays. There is
little motion, and, where the poisoning is insufficient to cause death, quick
recovery results. Otherwise complete paralysis is followed by death.
(iii) Sulphur. — Sulphur applied in the form of sulphide sprays or elemental
sulphur in the form of dust causes pronounced dysentery. In tent experiments a
certain amount of mortality was caused, but under field conditions it was
believed that most of the bees recovered. Severe spotting of clothing hung out
to dry has resulted from the use of this material in several cases.
(iv) Copper. — Copper fungicides as yet have not been definitely proved to
cause death to bees under field conditions and the evidence would appear to
indicate that they are quite safe to use. Where fed to bees or when wet weather
prevails they may cause death. The insects become sluggish, lose their power of
movement and finally death ensues, only more slowly than with arsenical
poisons.
Repellent Action of Sprays. — Lime sulphur was the only material found
definitely repellent by Mclndoo and Demuth (1926). Bourne (1927) found
nicotine also to be repellent. Repulsion to these materials is hard to demon-
strate under field conditions and, if it exists, it would appear to have
little practical effect. In making our observations, we have repeatedly observed
the action of different materials including poisoned Bordeaux, lime sulphur
alone or in combinations with calcium arsenate, or with the latter and nicotine
sulphate, 90-10 sulphur-lead arsenate and other combinations. We have also
studied the effect of the commercial materials and combinations when applied
to bouquets and, in all cases, could obtain little consistent evidence of pro-
longed repulsion under field conditions, the bees sometimes settling quickly upon
the trees as fast as the machine passed. In few cases was the repulsion of long
duration. In one case lime sulphur-calcium arsenate appeared to repel for 17
hours. In most cases the repulsion was of only a few minutes duration and
was apparently over by the time the material had dried. Sulphur-lead arsenate
actually seemed to attract. These observations are based on definite counts of
wTild and hive bees visiting bloom treated with different materials, unsprayed
bloom being available in all cases.
(c) LETHAL DOSAGES
Data obtained from analyses of bees (package and hive) that had died
from natural causes and those dying in check tents, where no poison had been
applied, showed arsenic present, as metallic arsenic, from -00004 to -00008
milligrams of internal arsenic (As), and from -00004 to -00009 milligrams of
total arsenic (As), internal plus external, per bee. No traces of arsenic were
found in check samples of larvae, pollen or nectar, but minute quantities were
found in pupae.
From this data we may assume that when the internal arsenic found in
adult bees is greater than -00004 milligrams of metallic arsenic per bee, poison-
ing may be suspected; definitely so, when higher than -00008 milligrams of
metallic arsenic per bee are detected. Analyses of adult bees, larvae, pollen,
166
pupae and nectar from locations where no poison of any kind was used and
where no poisoning was obtained, are given for purposes of comparison with
subsequent observations in which poisoning actually occurred.
TABLE No. 28.— ANALYSES OF CHECK SAMPLES OF BEES, LARVAE, POLLEN, PUPAE
AND NECTAR
Sample
No.
Nature
of
material
From
bees
(Internal)
Mg.
Wash
water from
bees
(External)
Mg.
Total
internal
plus
external
Mg.
Average
arsenic
(As)
per bee
(Internal)
Mg.
Remarks
1
Bees
•003030
(bees not
washed)
•002500
(bees not
washed)
•004050
(bees not
washed)
•001273
•004303
•001270
•003500
•004550
•001750
•004022
•00003
•00006
•00003
•00005
•00004
•00004
nil.
•00007
nil.
nil.
nil.
nil.
nil.
100 bees used in each sample
except No. la, when 19 bees
were taken.
la
u
2
u
•001000
2a
«
3
3a
•000700
4
Larvae
5
Pupae
•00008 %; 10 pupae used.
1-5390 gs. used.
6
Pollen
7
0-9038 g. used.
8
Nectar
Nectar pipetted from combs;
9
approximately 3 grams in
each sample.
10
tt
3. TENT EXPERIMENTS IN BEE POISONING
In 1928-1929 tents were placed over entire trees, which were sprayed
during bloom, and a hive of bees placed in the tent immediately thereafter.
In 1930 and 1931 large bouquets were used instead of entire trees. In view of
the great amount of data secured and the limitations in accuracy from such
experiments, only the more outstanding results are included in the following
report.
Following the application, observations as to the reaction of the bees to the
different materials and on the daily mortality were made. The dead bees were
counted every day from the floor of the tent upon which sheets were placed,
until mortality ceased. Following 1930, " dead-bee traps " of the type used
by Mclndoo (1926) were employed, but modified so as to have a removable
bottom board from which the top could be lifted and the dead bees readily
removed. After pronounced poisoning had developed, we removed the bees
from the tents, placed the traps in place and based further counts on daily
removals of dead bees from the traps.
Chemical tests were made of dead bees and of brood available. Sufficient
pollen or nectar was rarely available from bees tented over a single tree; but
pollen and nectar from bad cases of field poisoning are reported on elsewhere.
(a) TECHNIQUE OF CHEMICAL TESTS
When the dead bees were received at the laboratory two chemical pro-
cedures were followed. In one instance, the bees were analyzed as received —
no attempt being made to remove external poison, the arsenic present in adhering
dust or other forms on the body of the bee.
In the procedure generally followed, the bees, usually 100 in number, were
placed in a suitable bottle and washed, by gentle agitation, with 4-25 ml. aliquota
167
of 2 per cent nitric acid (by volume). After each washing the liquid or wash
water was poured through a filter. The bees were then washed in the filter with
20-30 ml. of distilled water, and finally with 10 ml. of alcohol.
For destruction of organic matter, the samples of pollen, nectar, larvae,
pupae, bees as received, wash water and washed bees with filter paper were
treated with 10-15 ml. of cone, sulphuric acid and charred on the hot plate.
Concentrated nitric acid was then added, the liquid heated, and more acid
. r
Fig. 69. — (1) Modified Mclndoo trap, showing removable bottom board; (2)
modified Mclndoo trap in place (original from photo by C. B. Gooderham) .
added until finally a colourless solution was obtained. This solution was evapor-
ated to dryness, washed into a modified Gutzeit generating flask, and arsenic
determined by the Gutzeit method.
The arsenic found on analysis of the washed bees is designated internal
arsenic; that from analysis of the wash water, external arsenic — the sum of the
two, total arsenic. The total arsenic is also obtained by analyzing the bees
direct as received, e.g., not washing with nitric acid previous to analysis.
168
(b) EXPERIMENTS IN 1928
The following materials and combinations were utilized in 1928 and the
results of the tests from a standpoint of mortality and chemical analysis are
found in the accompanying tables. Only those materials that gave a greater
mortality than the checks are shown in the table. All others gave either the
same results or a lesser mortality.
The following spray dust preparations were applied to the tented trees: —
Tent No.
i
No.
'
No.
1
No.
(
No.
t
No.
t
No.
'
No.
1
No.
t
No.
Sprays
1— Bordeaux 3-10-40.
2— Nicotine sulphate (1 pt.-lOO gals.)
3 — Calcium arsenate (1-40).
4— Bordeaux (3-10-40) -Nicotine sulphate (1 pt.-lOO gals.)
5— Bordeaux (3-10-40) -Calcium arsenate (1-40).
6 — Bordeaux (3-10-40) -Nicotine sulphate (1 pt.-lOO gals.) -Calcium arsenate (1-40)
7 — Lime sulphur (1-40).
8 — Lime sulphur (1-40) -Nicotine sulphate (1 pt.-lOO gals.)
9 — Lime sulphur (l-40)-Calcium arsenate (1-40)
10 — Lime sulphur (1-40-Calcium arsenate (1-40)-Nicotine sulphate (1 pt.-lOO gals.)
Dusts
Tent No. 11— Sulphur (95-5).
" No. 12 — Nicotine-(5f/t nicotine sulphate).
" No. 13— Sulphur-Lead arsenate (90-10).
" No. 14— Poisoned Bordeaux (12-8-80).
" No. 15 — Copper carbonate-Lime-Nicotine sulphate (9-86-5).
" No. 16— Check.
" No. 17— Check.
(i) Results from Standpoint of Mortality, 1928. — The most outstanding
point in connection with these results was that all the combinations containing
nicotine showed lower mortality than the checks, except Xo. 10, which included
calcium arsenate. All Bordeaux combinations gave less than the checks, except
No. 5, which contained calcium arsenate. All mixtures containing lime sulphur,
except No. 8, which contained nicotine sulphate, and sulphur dust gave a higher
mortality than the checks, even plain lime sulphur showing some loss. Sulphur
dust caused dysentery, but less mortality than where arsenicals were present.
Sulphur-lead arsenate was particularly deadly and sudden in its action, a fact
which checks up with field data and chemical tests. Only arsenical and arsenical
combinations produced dead brood.
TABLE No. 29.
-TABLE SHOWING TOTAL MORTALITY OX 2nd, 3rd. 4th
OF COUNT
AND FINAL DAY
No.
Material
Total number Dead on Different Days
2nd.
3rd.
4th.
1- ina 1
Total
1 13
2 10
3 3
4 9
5 5
6 11
7 7
8 17
Sulphur-lead arsenate dust
Lime sulphur-Calcium arsenate- Nicotine sulphate
Calcium arsenate
Lime sulphur-( 'aleium arsenate
Bordeaux-Calcium arsenate
Sulphur dust
Lime sulphur
Check
200
0
0
0
0
242
0
52
1,900
380
698
405
304
342
349
42
,900
663
.512
819
516
384
504
4,083
3,368
3,284
2,069
1.9S1
1.773
1,483
1,230
(ii) Chemical Data, 1928.— Taking -00004 to -00008 milligrams oi metallic
arsenic as the lethal dose per bee, we find a condition of bee poisoning to exist
on May 31 and June 1, the first days' mortality, as follows: —
169
Tent No. 3 — Calcium arsenate- • 00086 milligrams per bee.
" No. 5 — Bordeaux-Calcium arsenate- -00099 milligrams per bee.
" No. 6 — Bordeaux-Calcium arsenate-Nicotine sulphate-- 00046 milligrams per bee.
" No. 9 — Lime sulphur-Calcium arsenate-. 00036 milligrams per bee.
" No. 10 — Lime sulphur-Calcium arsenate-Nicotine sulphate- -00045 milligrams per bee.
" No. 13 — Sulphur-Lead arsenate- -00106 milligrams per bee.
" No. 14— Bordeaux (12-8-80)- -00042 milligrams per bee.
It will be seen that in all cases the minimum lethal dose is greatly exceeded
in these samples. While the bees collected from the check tents in this experi-
ment showed, from -00014 to -00017 milligrams of metallic arsenic per bee, this
high figure is due to poison residue obtained from previous sprays and apparently
imbibed in drip water consumed by bees following rains. Later work has shown
that from -00004 to '00008 milligrams of metallic arsenic represents more
closely the quantity of arsenic per bee that dies from natural causes. Subse-
quent analyses of adult bees, together with larva? and pollen from certain of the
tests showing heaviest mortality, were made, and the data presented in the
following table. Owing to the comparatively small amount of forage afforded
by a single tree, it was only possible to secure larvae and pollen samples from a
few tents and no nectar samples were procurable.
TABLE No. 30.-
-ARSENIC, AS METALLIC As, FROM CHEMICAL ANALYSES OF BEES
UNDER CAGE CONDITIONS, 1928
Number
of bees
analysed
Arsenic (As)
in milligrams
Tent number and date of collection
From bees
(a)
Wash water
from bees
(b)
Total
bees plus
wash water
(c)
Average
quantity of
arsenic (As)
per bee
(d)
17 Check May 31
40
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
50
100
100
100
•00682
•01439
•08633
•11510
•04392
•10602
•12722
•09996
•04241
•10299
•04544
•03636
•10602
•04241
•04544
•21507
•10602
•17268
•04847
•15752
•08197
•00341
(e)
•01212
(e)
•05755
(f)
(f)
•04847
(f)
(f)
(f)
•04241
(e)
(f)
•09694
•06816
•08028
•03938
•05756
(e)
(f)
•01023
•01439
•09845
•11510
•10147
•00017
16 " June 1
3 " May 31
•00014
•00086
3 " May 31
3 " June 1
•00044
•00106
3 " June 7
•00127
5 " May 31
•14843
• 00099
• 00042
6 " June 4
•00103
6 " June 6. . .
■00045
9 " May 31
•07877
•10602
•00036
9 " June 1
9 " June 4..
•00042
10 " June 1
•14238
•28323
•18630
•21206
•10603
•15752
•00045
13 " May 30
•00215
13 " May 31
•00106
13 " May 31
■00345
13 " June 4
■00048
13 " June 4. . .
•00082
(a) Total quantity of arsenic (As) within the body of the bee.
(b) Arsenic (As) carried outside the body of the bee.
(c) Includes arsenic (As) within and without the body of the bee.
(d) Average quantity of arsenic (As) per bee within the body.
(e) Bees not washed previous to examination. (Internal and external (As)).
(f) Washed bees only examined. (Arsenic (As) within the body of the bee).
TABLE No. 31.— ARSENIC, AS METALLIC As, FROM LARVAE, 1928
Source of Poisoning
Number
Weight
Arsenic (As)
Per larva
No. 3 Calcium arsenate — June 8. . . .
4
15
30
gm.
0131
0-707
2-633
p.c.
•00173
•00114
•00150
mg.
• 000568
No. 9 Lime sulphur-calcium arsenate — June 6
•000529
No. 13 Sulphur-lead arsenate — June 5
•001313
170
(c) EXPERIMENTS IN 1929
Tent studies were continued in 1929 along similar lines to those of the
preceding year. It was found impossible to start all the experiments at once;
consequently it was necessary to initiate a series on two distinct dates.
Weather conditions are believed to have played a greater part in some cases
in the results secured than the actual differences between materials. Analyses
of bees from all the tents were made, as in 1928. In order to avoid repetition
and conserve space, however, the principal points brought out in the two years'
tests are shown in the accompanying table, and analyses of pupae from certain
of the poisoned colonies, in the table which follows it. Analyses of pollen col-
lected during this season are shown elsewhere.
TABLE No. 32.— SUMMARY OF RESULTS WITH ADULT BEES
No.
Material
Order of
mortality1
Average arsenic per bee,
milligrams
1928
1929
1928
1929
1
B
X
X
3
X
5
X
7
X
4
2
6
X
1
X
X
X
X
X
4
X
2
X
3
X
7
6
5
X
X
X
X
X
X
•00044-00127
X
•00042-00099
•00042-00103
X
X
•00036-00042
•00045
X
X
•00048-00215
X
X
X
X
2
N.S
X
3
C.A....
•00003- -00050
4
B. + N.S
X
5
B. + C.A
•00004- -00023
6
B. + C.A. + N.S
•00008- -00018
7
L.S
X
8
L.S. + N.S
X
9
L.S. + C.A
•00003- -00018
10
L.S. + C.A. + N.S
•00006- -00018
11
S. Dust
X
12
N.S. Dust (2%)
X
13
S. + L.A. Dust
•00011-00055
14
B. + C.A. Dust
X
15
CuC. + N.S. Dust
X
16
Check....
•00004-00008
B. = Bordeaux; N.S.
C.A. = Calcium arsenate; L.S.
L.A. = Lead arsenate; CuC.
S. - Sulphur.
irThe material showing highest mortality rate is numbered.
X. Less mortality than checks.
= Nicotine sulphate;
= Lime sulphur;
= Copper carbonate;
TABLE No. 33.— ARSENIC AS METALLIC As, FROM PUPAE, 1929
Num-
ber
Weight
Arsenic (As)
Source of Poisoning
Milli-
grams
No. 3 Calcium arsenate. . .
3
13
gms.
•0932
•9060
p.c.
•00244
•00025
per pupa
•00076
No. 16 Check
June 1 1
•00018
(d) SUMMARY AND CONCLUSIONS FROM TENT STUDIES OF BEE POISONING.
1928-1929
The inconsistent mortality from the different spray materials in the different
years indicates that we cannot draw definite deductions from one season's opera-
tions, since difference between colonies, effects of weather conditions and other
factors lead to highly irregular results. With the dust preparations, Bordeaux
dust causes some mortality, sulphur dust heavy mortality where the bees are
confined, probably due to the severe dysentery produced, but the highest mortal-
171
ity is caused by the use of sulphur-lead arsenate dust. The high mortality from
this combination whether 90-10 or 85-15 has been unquestionably demonstrated
year after year.
Owing to the situation outlined, conclusions on all points can be attempted
only with caution; but, making allowance for all irregularities and inconsistencies,
and bearing in mind the field evidence available, the following general conclusions
appear justifiable:
1. Sprays containing arsenicals are dangerous to bees when applied during
bloom.
2. Only sprays or dusts containing arsenicals caused dead brood in these
tests.
3. The combination causing the most sudden and the heaviest mortality
was sulphur-lead arsenate in dust form.
4. Generally, but not invariably, less toxicity appears to be exhibited by
sprays or dusts containing nicotine or copper sulphate as an ingredient.
5. Unpoisoned sulphur dust, in addition to causing a pronounced dysentery,
may also cause the death of bees. Just how important this may be under
orchard conditions is not clear, but apparently it is much less dangerous and
slower in action than arsenicals.
(e) REPULSION TESTS 1930-1931
Tent studies were continued in 1930-1931 mainly with the object of securing
information regarding the repellent action of different spray and dust materials.
Tests were run in duplicate, and both treated and untreated bloom were avail-
able to the bees ; tubs filled with limbs of bloom in good condition being used.
Counts were made at intervals on the different treated bouquets to determine
the number of hive and wild bees visiting each, as compared with those visiting
the untreated bouquet in the same tent. As in the poison tests, the evidence
was to some extent conflicting in the different years; and furthermore, different
colonies reacted differently to the ingredients used. Weather conditions again
had an important influence.
Careful study of the data secured, indicates a few points that appear to
be reasonably consistent. Repulsion from the regular lime sulphur-arsenate is
likely to be very temporary and appears to have little significance under field
conditions. The addition of nicotine seems to increase the repulsion. Sulphur-
lead arsenate has no appreciable repulsive action. In fact, some observations
make it appear rather attractive than otherwise. Bordeaux, whether in dust or
in liquid form, appeared to exert marked repellent action in most cases when
bouquets were used; but this was not so evident under orchard conditions.
Nicotine dust also seemed to drive the bees away and to remain repellent for
some time after application. It may be noted that this dust is usually applied
at a time of day when bees are inactive.
(/) FEEDING TESTS, 1932
In order to supplement the foregoing studies, various spray ingredients were
fed directly to two-frame nuclei, the poison being incorporated in a sugar syrup
(1-1), placed in honey can feeders and placed over the frames in the ordinary
manner. Dead-bee traps were placed on all the hives. The following materials
were used at the rate indicated: —
1. Calcium arsenate, 1 pound to 40 gallons.
2. Copper sulphate, 3 pounds to 40 gallons.
3. Sulphur dust, 25 pounds to 100 gallons.
4. Nicotine sulphate, 1 pint to 100 gallons.
5. Lime sulphur, 1 gallon to 40 gallons.
172
To summarize briefly the result of these tests, the bees refused to feed upon
the syrup contained in Nos. 2, 4 and o to any appreciable extent and showed
every evidence of repulsion. After the nicotine sulphate had been exposed on
the frames for some time, there was a limited amount of feeding; but, as only a
very few dead bees were found, it was evident that no extensive feeding took
place. There was no sign of dead brood. Though few dead bees were found
in the traps, a few larvae were found in the combs two days later, showing that
a slight amount of the poison must have been fed to the larvae. The gas
evolved from the lime sulphur solution made the bees restless at first, but caused
little, if any, mortality for several hours. Little change occurred throughout
the duration of the test; no further feeding was observed and only a few dead
bees and larvae were noted. The material was obviously strongly repellent. They
fed upon the calcium arsenate, however, so rapidly and to such effect that within
an hour almost the entire population was at the bottom of the hive in a dead
or dying condition. There was no sign of repulsion and the bees fed upon the
poisoned syrup at least as readily as upon plain syrup. So sudden and complete
was the killing, that no additional evidence as to symptoms of arsenic poisoning
was obtainable. There was no sign of recovery of any of the bees.
In the case of the sulphur dust, this was consumed quite readily by the
bees; and, far from there being any evidence of repulsion, it seemed to be more
attractive than the plain syrup. Droplets exposed on the tops of the frames
were quickly lapped up, following which the bees attempted to consume the
sulphur residue. There was, however, no pronounced mortality within five
hours of the initiation of the test; but by 9 a.m. the next day many sick and
dead bees were found in the trap, and " crawlers " were numerous in the
grass. By 2 p.m. the bees that had been sick had gathered in bunches and
were mostly dead. By 11 a.m. on the third day, sick, dying and dead bees
were numerous in the trap, the living population had dwindled to a very few
bees and some of the larvae had apparently crawled out of the cells.
To sum up: copper sulphate, lime sulphur and nicotine sulphate, incorporated
in sugar syrup in the dilution ordinarily used in spraying, and fed to bees, were
so strongly repulsive that they were refused by the bees and, as a result, little
poisoning resulted. Neither calcium arsenate nor sulphur dust gave any evi-
dence of repulsion and were readily consumed. The former brought about the
rapid extinction of the colony, but the latter was much slower in its action.
4. STUDIES FROM COMMERCIAL ORCHARDS
From time to time reports were received or cases were noted of apparent
conditions of poisoning from commercial orchards. In such cases, samples of
dead and sick bees, together with pollen and nectar, when procurable, were
secured and subjected to chemical analysis. The results of these studies are
set forth in the following pages.
(a) CHEMICAL DATA ON SAMPLES FROM COMMERCIAL ORCHARDS, 1928
A number of samples obtained from commercial orchards during the investi-
gation furnish the data presented in the following table. Though complete
analyses wTere made in most cases, only the most significant are included in
the table. Furthermore, the results of many analyses, where relevant informa-
tion is lacking, have been omitted entirely. Sufficient typical cases have been
selected to give a fair picture of the situation throughout.
173
TABLE No. 34.— RESULTS OF EXAMINATION OF FIELD SAMPLES, 1920-1930
Orchard
number
Date
Nature of
samples
% (As)
Arsenic
Ave. As.
per bee
(Internal)
mg.
1
31/5/28
4/6/28
10/6/28
20/6/28
100 bees
0-00023
100 "
100 "
0-00023
0-00043
2
3
3 lots of
100 bees
0-00029-
0-00054
4
3/6/29
100 bees
0-00032
5
3/6/29
74 "
0-00027
6
30/5/30
30/5/30
75 "
5 samples
of 100 bees
0-00006
0 00010-
0-00028
7
8
10/6/32
30/5/32
100 bees
100 "
0-00045
0-00015
9
10
27/7/32
100 "
0-00033
Remarks
Orchard sprayed with lime sulphur-calcium arsenate; poisoning
evident.
While neighbour was dusting with sulphur-lead arsenate, bees
began to arrive in front of hive in dying condition. Severe
poisoning with death of brood followed.
Very sudden and severe poisoning resulting, on examination of
trie two colonies, following application of 85-15 sulphur-
lead arsenate to neighbouring orchard. Pollen from comb
analysed -00452 % arsenic; sample of larvae -00020 arsenic.
Apples not in bloom but wild radish in bloom in dusted
orchard.
All 80 colonies showed severe poisoning of adults and brood, the
two strongest most severe. All neighbouring orchards
dusted with sulphur-lead arsenate and after each applica-
tion large numbers of dead and dying bees appeared
before hives.
All 7 colonies suffered severely, two being completely extermin-
ated following application of sulphur -lead arsenate to all
neighbouring orchards. Much dead brood present and
pollen samples showed -00237% arsenic; larvae sample,
•00237% arsenic.
Check sample of unpoisoned bees.
Bees placed in orchard May 24, before bloom appeared; 7-5 and
8-6 hours sunlight on May 24 and 25 respectively; weather
until June 1 cold and wet, temperature only once reaching
60°F. Five colonies exterminated by June 1, remaining 2
slowly died out. Poisoning took place before apple bloom.
Typical of conditions in 1930 when severe poisoning occurred
in nearly all apiaries before bloom.
Poisoning evident; no spraying done within 1 \ miles of apiary.
One colony badly poisoned; only spraying practised in neigh-
bourhood of orchard.
This late poisoning was apparently due to a neighbouring
orchard being dusted with poisoned Bordeaux dust for
apple maggot. Wild radish in bloom in the orchard;
mortality large.
(b) CONCLUSION FROM EXAMINATION OF COMMERCIAL SAMPLES OF
DEAD BEES
The data obtained from analyses of samples of dead bees showed, in general,
ponderable amounts of arsenic, from 2 to 14 times the quantity found in bees
dying from natural causes. Poisoning occurred in all seasons, but was most
pronounced following periods of dull, wet weather. Dead brood, taken from
frames of the poisoned colonies also gave large percentages of arsenic. The
results indicate that, in this orchard area, practically no period of the summer
is entirely safe for hive bees.
(c) GENERAL SURVEY OF FIELD CONDITIONS
(i) Fungicide Dusts. — Orchards treated with poisoned copper fungicides
have apparently served as the source of a certain amount of poisoning among
bees, but the evidence on this point is neither so clean-cut nor so pronounced as in
the case of sulphur-lead arsenate dust (90-10 or 85-15). In front of colonies
poisoned by this latter mixture it was quite common to see carpets of bees 6-40
feet in length and of varying width. The bees so poisoned are unable to fly, but
crawl or bunch on the ground in front of the hives. During 1929, the bloom
came out very suddenly before many growers had applied their " pink " applica-
tions, resulting in much spray and dust being applied to bloom. We have records
from nine lots of bees placed in locations widely separated from each other. In
four of these areas no dusting whatever was done. No poisoning whatever
occurred, so far as could be determined, in three of these apiaries. In the fourth,
.some poisoning did take place, but not of a type to be noticed by the casual
observer. In another orchard where spraying had been practised, but not during
174
bloom, no poisoning was evident until an adjoining orchard was dusted with
90-10 sulphur-lead arsenate. Dusting was completed at 9 a.m. Examination at
4.30 p.m. revealed many " crawlers " and other unmistakable signs of poisoning,
the colonies becoming seriously depleted as a result.
Fig. 70. — (1) Orchard dusting: (2) showing drift of dust cloud in orchard
(original from photo by C. B. Gooderham).
Two groups of colonies were placed in the same district in 1929, but over
a mile apart. All were in good condition up to May 30. Owing to rain and
cold, no flight occurred in either apiary until June 5, when 90-10 sulphur-lead
arsenate dust was applied to an orchard adjacent to one of these apiaries.
Crawlers were present in front of all hives in this apiary and, for several feet
in front of all colonies the ground was covered with dead bees, and there was
a definite break in brood rearing. Dead bees and pollen showed a high content
of arsenic. All other colonies placed in areas where sulphur-lead arsenate was
applied suffered severely, many were killed outright and only with the greatest
difficulty could the remainder be built up for overwintering.
(ii) Sulphur Dust. — Unpoisoned sulphur dust is frequently applied, especi-
ally in bloom, and is usually accompanied by dysentery among the bees. In
1929, no poison dusting was carried out about Gaspereaux, though considerable
sulphur dusting occurred. Dysentery was quite pronounced, clothing hung out
to dry being badly spotted. No positive evidence of serious mortality was
obtained, and the colonies made continuous and satisfactory gains for several
175
weeks, when slight poisoning occurred following further applications of poison
dusts, wild radish (Raphanus Raphanistrum L.) being then in bloom. Feeding
tests indicate that considerable mortality may be occasioned by unpoisoned
sulphur dust, but not comparable to that caused by arsenicals.
(iii) Nicotine. — In all the orchards where apiaries have been placed, we have
practised nicotine dusting during bloom, in order to eliminate injury from suck-
ing insects such as the green apple bug (Lygus communis Knight) to the bloom.
The applications were made at night or early morning when no bees were in
the tree. A strong dust containing double the usual strength, i.e. 4 per cent of
actual nicotine, was employed. Neither in these nor other orchards treated with
commercial nicotine dust have we been able to detect signs of marked poisoning,
though bees were noticed freely working the trees and occasionally became
dusted with lime. It would appear that if deaths from the use of this prepara-
tion ever occur under field conditions, they must be too few to be detected by
ordinary means. It has already been noted that nicotine dust is usually applied
when the bees are not in the trees, and the rapid volatilization of the nicotine
would remove the possibility of acute poisoning.
We have no field evidence of poisoning from nicotine sprays, and since this
material is almost invariably used in combination with other materials, it would
be difficult to isolate the action of this one ingredient. It is not, however, con-
sidered to be an important source of poisoning under field conditions.
(iv) Arsenical Sprays. — It is not possible to distinguish between the effects
of different spray mixtures containing arsenicals, some growers using poisoned
Bordeaux and some lime sulphur in almost every community, so that the exact
source of the poisoning could not be determined in the majority of cases. As
already noted, only one clear-cut case of poisoning from sprays occurred during
1929, but following that year such cases became increasingly frequent.
One of the best locations for making observations on bee poisoning from
sprays was Long island, where no dusting had been practised for several years
and where bees had been kept under close observation since 1928. Bees do not
appear to fly across the two miles of dyke to the mainland in any number during
bloom, though, of course, no one could say that such a flight never occurs. When
the mainland orchards are blooming, the island orchards may still be bare, or
nearly so, and, under such conditions, though flight might occur, we have failed
to demonstrate it. When orchards on the island are in bloom and the main-
land largely out of bloom we could never trace the bees to mainland orchards.
In 1928, some poisoning occurred, resulting in a loss of the field force which
affected the performance of the hives very materially. Records of honey pro-
duced by 32 colonies left on the Island during the season of 1929 when similar
conditions occurred, and 32 others kept outside during bloom and only taken to
the island for the clover flow, are available. The two lots were as nearly
similar as was practical to select them and all other conditions were equal. The
production of the first lot was 2,200 pounds of honey, of the second 3,100 pounds.
Analysis of bees from the first lot showed large amounts of arsenic in dead
bees and excreta. We cannot prove that the bees did not secure this poison from
dusted areas on the mainland, but it is noteworthy that colonies used from the
same apiary in several other orchards, in which spray was employed, were not
poisoned. Furthermore, a small apiary on the opposite mainland escaped
noticeable poisoning. Moreover, results for the following three years on the
same location, further support the belief that the poisoning was obtained on the
island as a result of sprays. Poisoned Bordeaux was the spray used up to the
time poisoning occurred. It should be said that there was little evidence of dead
brood, there being no colonies killed outright and no definite break in brood
rearing in these colonies during the years 1928-1931 inclusive.
176
The following two years similar poisoning took place. The season of 1930
was characterized by several days of cold weather in the pre-blossom period and
during early bloom. May 26 to June 3, was generally cool with the ther-
mometer not going above 62° F. at any time. The colonies were placed in
certain orchards on May 24, in anticipation of immediate bloom, which, how-
ever, was so retarded by the cold weather that Gravenstein was not in full
bloom until June 5. There was rain on May 27, 28, 29, 31 and on June 1 and 2.
On June 3, the weather cleared and became warm and bright. During this
period, May 30 was the only day when flight was possible, there being 7^ hours
of sunlight, and considerable activity was noticed. Poisoning, in many cases
severe, immediately developed. A number of colonies were wiped out, dead
brood developed, and all colonies were so weakened that they were removed
from the orchards as being useless for purposes of pollination.
In 1931, injury was particularly severe, which may at least, partially, be
accounted for by the fact that heavier spraying was done with a higher arsenic
content than ever before. Bees from a small apiary on the mainland worked
the bloom in orchards immediately opposite, which were not sprayed as heavily
as on the island. These bees showed no poisoning.
On June 2, 1932, about 100 colonies of bees were moved to Long island as
Gravenstein was coming into bloom and careful investigation failed to yield
any evidence that the bees were flying to the mainland in any numbers, and
there is much evidence that they did not. June 3 was an ideal day for flight
and the bees worked freely, but this was followed by five days of cold, damp
and changeable weather during which their flight was inhibited, while on the
6th and 7th there was no activity whatever in the bloom. On the 8th there
was a little activity and on the 9th fairly good conditions. Poisoning was
evident on June 4 and increased each day thereafter. It was not of the sudden
acute type so characteristic of poisoning from dust, though most evident after
a rain. The bees at the east end of the Island suffered worst, more orchard
and heavier spraying being done in that territory. The bees began to dwindle
until June 23, when a careful examination showed that, in order to save the
colonies, drastic uniting would have to be carried out and, accordingly, the
original 105 colonies were united to make 68 new colonies, some of these con-
sisting of little more than two or three frames covered with bees.
The foregoing case is important because we definitely know that the poison-
ing was caused by Bordeaux-arsenate spray, all growers on the Island confining
themselves to this combination. The common formula used was 3-10-40 plus
one pound of calcium arsenate, but many variations were used. In one case
some Gravenstein bloom was out when the spraying was done, which was on
the day previous to the colonies being introduced. It was noticeable that bees
in this orchard suffered worst, though all colonies showed losses, even though
no spraying had been done for five days previously. The accompanying tables
are given to show the great reduction in strength as a result of this poisoning.
TABLE No. 35.-
177
-STRENGTH OF COLONIES MAY 11,
POLLINATION WORK*
1932, BEFORE USING IN
Number
of
colony
Combs
covered
Number
of
colony
Combs
covered
Number
of
colony
Combs
covered
Number
of
colony
Combs
covered
238
50
6-0
50
50
6-5
60
50
90
8-0
50
7-5
6-0
90
60
5-5
50
60
50
70
60
4-5
60
50
100
8-0
9-5
50
267
120
264
250
273
232
279
284
257
259
77
All
211
216
201
108
240
245
224
226
123
114
260
285
159
227
288
70
9-5
4-5
8-0
6-5
60
40
5-5
60
60
5-5
8-0
90
60
90
50
90
6-5
5-0
5-5
50
4-5
90
50
4-5
70
5-0
206
A15
5-5
8-0
90
4-0
90
4-5
90
50
50
50
70
4-5
50
70
8-0
60
7-0
4-5
60
90
70
50
60
7-0
50
8-0
6-5
87
128
132
228
117
348
210
131
126
203
200
268
261
283
277
275
124
234
255
258
265
252
218
221
7 5
151
30
40
34A
154
220
39
30
214
95
100
89...
282
100
121 .
237
5-5
78
231
50
209
B4....
6-5
93...
62
7-5
249...
287
50
241
266
90
153
235
50
222
230
90
88...
102
80
158
205
60
207
248
6-5
45...
155
30
225
202
90
110 ..
157
5-5
100 ..
152...
5-5
213...
262
4-0
80 .
280
5-5
247...
204
60
239...
278
233
272...
256...
286
"There was an increase in the strength of these colonies from 3 to 5 combs from May 11 to May 26.
The latter date 50 colonies were moved to the Somerset orchard, where no poisoning occurred during the
6 days they remained. On June 2, all colonies were removed to Long Island and left there until June 10.
The following tables give the strength of the colonies on June 23, 1932,
after having been used in the pollination work: —
TABLE No. 36
A. Colonies United Because of Weakness Due to Poisoning
Numbers of the colonies
united
Number of combs
covered in each
colony united
Number of the colonies
united
Number of combs
covered in each
colony united
278,
207
1 1 1
234, Dead
264,
209
2 2
211, 88,
272
1 1 \
248,
241
2 1
158, 159,
262
1 \ \
226,
B 4
2 1
218, 233
W H
258,
200,
93
2 1 1
108, 250
l! 11
89,
220,
275
H 1 1
231, 39
u n
240,
255
H H
102, 77,
266
2 \ 2
205,
280,
34A
ii 1-1 i
221, 132,
252
H 1 U
151,
230
l i
A15, 225,
2 1
204,
214,
153
2 1 1
202, 80
H 1*
286,
224,
228
oil
100, 279,
123
i\ 1 1
258,
128,
114
ii ii i
-12 i-2 2
237, 235
2 1
201,
265
285, 131
2 1
95,*
285
8 1
152, * 157
5i 1
284,*
238
4 4
Queenless.
60796—12
178
B. Colonies Left Ununited
Number
ol
colony
Number
of combs
covered
Number
of
cofony
Number
of combs
covered
Number
of
colony
Number
of combs
covered
Number
of
colony
Number
of combs
covered
121
20
20
4-0
6-0
5-0
4-0
40
8-0
50
5-0
261
277
283
110
210
259
282
277
62
216
80
8-0
130
50
8-0
7-5
50
50
40
11-0
78
30
3-5
2-5
4-0
40
4-0
8-0
8-0
7-0
7-0
45
282
227
222
126
245
203
273
131
30
34B
155
2-5
117
249
40
All
213
50
206
87
3-5
239
247
8-0
120
124
154
90
256
8-0
260...
287
20
288
257
We have many records to show that orchards may be sprayed, even when
considerable bloom is present, with the different commercial mixtures and no
losses occur. Indeed, gains are frequently recorded in such cases; but, under
certain weather conditions, as indicated in the next section, severe poisoning
may take place. Complete loss of colonies seldom occurs and there is less loss
of brood than is found in most cases of poisoning from sulphur-lead arsenate
dust.
5. INFLUENCE OF WEATHER CONDITIONS ON BEE POISONING
One would expect that poisoning would be greatest in prolonged periods
of weather favourable for flight and activity, and several workers have definitely
stated that this is the case. It is, therefore, worthy of note that the most severe
cases recorded were those which occurred following periods of cold, dull or wet
weather, during which the bees were largely or entirely confined to the hives.
With the coming of bright sunny weather " crawlers " would suddenly appear
before the hives, and other symptoms of poisoning became evident. With the
clearing of the weather the number of " crawlers " would gradually diminish.
Though dwindling of brood might go on as a result of poison stores, no cases of
new poisoning would develop until another period of dull weather when, with
the return of flight, the condition would be repeated in more or less severity.
Least poisoning was noted in the majority of cases during warm bright weather,
even though poisons were applied to bloom.
In the Lakeville area where the conditions are definitely known, some inter-
esting observations were made in 1929. All colonies were in good condition on
May 30. Rain fell from 6 p.m. on that date, causing the growers to apply
a dust, some the same night, others early next morning. This was very general
all over the area, the dusts being sulphur-lead arsenate 90-10 and 85-15. May
31 to June 2 was cold 'and foggy, with mist and rain. On June 2, there were
brief periods of sunlight throughout the day. The most severe symptoms of
poisoning immediately became evident, and, when examined next day, some
of the colonies were already practically exterminated.
In 1930, a number of colonies were set aside for poison tests during bloom,
but heavy poisoning occurred before bloom, all colonies retained for the purpose
being poisoned, and we had available for further poison tests only a few rented
colonies which had been kept outside the sprayed area. Two were placed in an
orchard which was heavily dusted with sulphur, one in an orchard dusted with
sulphur-lead arsenate, and five in an orchard dusted with unpoisoned Bordeaux
dust (12-88). The weather turned hot and bright and continued thus from
June 3, when the hives were placed, until June 11 when they were removed. Xo
poisoning occurred even in the orchard treated with sulphur and arsenate. This
result is not necessarily conclusive, since a single colony in an area planted
heavily to orchard may do most of its work elsewhere, but at least it is con-
sistent with our other results.
179
Only two examples will be given from 1931. Bees were not placed in
orchards until bloom was well started. On Long island bees were placed on
May 29, the two preceding days being favourable for flight. No spraying had
been done for six days previous to that date anywhere on the island. May 31
was bright and warm and great activity was noted at the hives. By 9 a.m.
" crawlers " and clusters of sick bees were numerous. By noon most of the
sick bees had disappeared and few were apparent the following day. The bees
were removed to the South Mountain, out of the poison zone, and no further
poisoning was noted. After several days of very rainy weather typical poison-
ing symptoms again became evident, even worse than before, and the colonies
continued to dwindle for some time.
At Pereaux, 32 package colonies were placed in an orchard May 25 at 9 a.m.
The day was cool and showery when the colonies were placed. Flight was
limited/ but, within an hour of placing, " crawlers " were observed near hives.
At 5 p.m. as much as a cupful of dead bees was found in front of some hives.
Spraying was general in the neighbourhood, but no dusting was done within a
mile. No spray was actually on the apple blossom in the neighbouring orchards,
but heavy spray was observable on grass, dandelions, etc. On the 26th it was
foggy with frequent showers. On May 27 the day was clear and bright. There
were no " crawlers " and apparently no further poisoning.
On Long island, poisoning was noticed in apiaries, particularly at the west
and east apiaries, following rain on June 2, 1930. No spraying had been done
for six days previous to this time, but most orchards had been sprayed quite
heavily. Practically all orchardists used poisoned Bordeaux, but most of them
used double the quantity of poison recommended. One man used lime sulphur-
calcium arsenate-aluminium sulphate. Bees were noticed in early morning in
considerable numbers lapping liquid from the leaves. In the afternoon when
trees had dried, more were noticed at puddles. Bees were observed heavily
working on trees covered with Bordeaux.
On June 8 and 9 the weather was cold and cloudy with some rain. Some
bloom still remained on late varieties but most had fallen; spraying was general
from June 5. Dead bees were noted on this date in large numbers in front of
all hives. Numbers of sick bees were noted crawling over the ground in the
orchard near the east apiary, which was newly sprayed with lime sulphur-iron
sulphate mixture. The herbage was also covered with spray. Crawling bees
were also found in a pasture northwest of the apiary where blueberry bloom was
abundant. There was no dusting on the island within two miles of the apiary.
It has already been fully described in the preceding section that periods of bee
poisoning on Long island, in 1932, followed periods of dull wet weather.
Three factors may account for these results: —
1. Bees after confinement for several days appear thirsty and seek mois-
ture on leaves and elsewhere with great activity, including that from leaves
heavily coated with poison. Even during rains bees have been observed making
short trips for water.
2. Pollen supplies being depleted during confinement, bees actively gather
large quantities near the hives at the first opportunity.
3. During periods of weather favourable for flight poisoned pollen may
be collected, but little actually consumed. During confinement they may feed
on such poisoned stores, the sick or dead bees leaving or being ejected from
the hives with the advent of favourable weather.
Nothing in this section should be interpreted as indicating that no serious
poisoning ever occurs during periods of fine weather which is certainly not the
case. The fact that the most severe cases of poisoning have occurred following
periods of dull wet weather, seems, however, to be established.
60706— 12i
180
6. SOURCES OF BEE POISONING (FOOD)
There are several possible sources from which poison may be obtained by
bees; viz: —
(a) Pollen
(b) Nectar
(c) Water
(a) POLLEN AS A SOURCE OF BEE POISONING
Since pollen is eaten to a certain extent by adult bees, as well as fed to the
brood, it would be expected to be a potent source of poisoning for both stages
and actual observations and analyses show this to be the case. The following-
table shows analyses from tent experiments and field samples where definite
poisoning occurred, and from two check samples.
TABLE No.
ARSENIC, AS METALLIC As, FOUND IN POLLEN
No.
Year
1928
2
1928
3
1928
4
1928
5
1928
6
1929
7
1929
8
1929
9
1929
10
1929
11
1932
12
1932
13
1932
14
1932
Source
Lime sulphur — calcium arsenate
Lime sulphur — nicotine — calcium arsenate
Sulphur — lead arsenate
Field sample (probably sulphur — lead arsenate)...
Field sample (probably sulphur — lead arsenate) —
Calcium arsenate
Bordeaux — calcium arsenate
Bordeaux — calcium arsenate — nicotine sulphate.
Lime sulphur — calcium arsenate — nicotine sulphate
90-10
Field sample
Field sample
Field sample (check)
Field sample (check)
Weight
Arsenic
(As)
gms.
p.c.
1-5666
•00116
1-0208
•00282
1-129
•00747
2-9044
•00069
0-8720
•00452
1-2960
•00111
1-3245
•00017
1-7921
•00063
1-3870
•00060
1-9820
•00057
0-9142
•00016
0-8150
•00019
1-5390
nil.
0-9038
nil.
It may be said that in all cases where severe poisoning occurred accom-
panied by dead brood, pollen analyses, when made, invariably showed ponder-
able amounts of arsenic. That the pollen secured is an important and, in many
cases, the main cause of the poisoning would appear evident. It seems likely
that the gradual dwindling away of a poisoned colony, after having been removed
to a poison free locality, may be attributed largely to this cause. The sudden
increase in deaths after a period of forced confinement may have a similar
origin.
(6) NECTAR AS A SOURCE OF POISONING
At odd times throughout the course of this project samples of nectar have
been collected and analysed. The percentages found arc tabulated as follows: —
TABLE No. 38.— ARSENIC, AS METALLIC As, FOUND IN ANALYSES OF
SAMPLES OF NECTAR
No.
Year
Source
Method of securing sample
Arsenic
As
1
1928
1929
1931
1931
Field sample
Field sample
Apiary Hive No. 104
Shaken from frames
p.c.
•00001
2
3
Shaken from frames
Pipetted from cells in frame
•00003
nil
4
Bee Division, Ottawa
Shaken from frame
Pipetted from cells
.00005
00006
181
The small amount of poison found, even when samples were secured in such
a way as not to preclude the possibility of contamination, would indicate that
nectar is not an important source of brood poisoning which is evidently derived
mainly from other sources. Nevertheless, since young larvae may be very
susceptible, this possibility cannot be entirely eliminated without further infor-
mation.
(c) WATER AS A SOURCE OF POISONING
Bees are frequently observed consuming water that drips from limbs or
collects in drops upon leaves covered with spray. This is particularly noticeable
after they have been confined several days by dull rainy weather.
In this connection a few typical quotations from the literature as to the
use that bees make of water may be of value. Root and Root (1929, pp. 745-746)
state " The gathering of water is more noticeable in the period of early spring
brood rearing and in hot weather than at other times." Langstroth and Dadant
(1927, pp. 101-103) state "water is necessary to bees to dissolve the honey,
which sometimes granulates in the cells, to digest pollen and to prepare the
food with which they feed the larvae."
" Bees take advantage of any warm winter day to bring it to their hives,
and in the early spring may be seen busily drinking around pumps, drains, and
other moist places. Later in the season they sip the dew from grass and leaves."
" That bees cannot raise much brood without water, unless they have fresh-
gathered honey, has been known from the times of Aristotle. Buera, of Athens
(Cotton, p. 104) said in 1797, ' Bees daily supply the worms with water; should
the state of the weather be such as to prevent the bees from fetching water for
a few days, the worms would perish. These dead bees are removed out of the
hives by the worker bees if they are healthy and strong; otherwise, the stock
perishes from their putrid exhalations'."
Phillips (1928, pp. 95, 135-136) notes "Water is needed at practically
all times during the breeding season, perhaps more especially in hot weather.
The bringing of water to the hive is most noticeable in the early spring."
" The collection of water by field bees is most commonly observed in early
spring and during the hottest parts of the summer, there probably being less
need for water when the humidity within the hive is high because of the eva-
poration of nectar. Bees have been known to collect water in quantity in
extremely hot weather and to place it on the bars within the hive, from which
places it disappears by evaporation, thus reducing the temperature within the
hive."
Langstroth (1914, pp. 293-294) states regarding the necessity of water for
bees as follows: "It is absolutely indispensable when they are building comb
or raising brood. But as soon as the grass starts and the trees are covered with
leaves they prefer to sip the dew from them. As soon as the weather becomes
warm, and the bees can supply themselves from the dew on grass and leaves it
will not be worth while to give them water in their hives."
Cowan (1890, p. 7) remarks: "Water is also used, but it is not stored,
and the bees only collect it as required."
Our own observations indicate that considerable water is consumed during
apple bloom. Bees have been noted sipping it from pools in the orchard after
a rain, from spray covered herbage beneath the trees and from the foliage and
petals of the apple trees. Even in very dark weather and during light rains,
small numbers of water-collectors make their short flights from and to the hive.
In one case they were seen, under such conditions, freely sipping water from a
spruce hedge adjacent to the apiary. The foregoing may at least in part explain
why such marked poisoning occurs after each rain. Drip water from different
situations from which bees were observed to consume it was collected and
analyses performed. The results are presented in the accompanying table. The
182
samples of water were pipetted from apple petals, leaves and from blades of
grass growing beneath the trees. The liquid samples were filtered before
analysis, so that the data indicate soluble arsenic or copper, or the colloidal
state of these metals.
TABLE No. 39.— ARSENIC, AS METALLIC As, IN MG. FOUND IN RAIN WATER FROM
LEAVES, ETC., IN SPRAYED AND DUSTED ORCHARD
No.
of
sample
As. in mg.
per
litre
nil
Copper as
metallic
cop. in mg.
per litre
0-7575
1-0810
1-7201
8-5720
15-3750
18-9002
1-8040
None taken
nil
Not taken
0 027
Treatment of orchard
Check.
Sprayed with lime sulphur — calcium arsenate — aluminium sulphate
mixture. Petals and leaves.
Same as foregoing.
Bordeaux, 8-35-160 used, plus 6 lbs. calcium arsenate. Heavy rain
all morning before taking sample.
Lime sulphur — calcium arsenate — iron sulphate mixture used. Light
rain in morning before taking samples.
Same as above, but in different part of orchard.
Dusted previous day with sulphur — lead arsenate (90-10). Heavy
rain fell following application.
From blades of grass in same orchard as preceding.
Sprayed with Bordeaux, 6-18-160 on June 3 and 4. Sample taken
June 6 following heavy downpour.
7. SOURCES OF BEE POISONING (PLANTS)
It has sometimes been assumed that the apple or other fruit bloom is the
sole source of poisoning, but the role of other flowering plants growing in or
near the orchard should be emphasized. Poisoning is generally first noticed with
the dandelion bloom, and the later cases of serious poison are usually associated
with the blossoms of the wild radish (Raphanus Raphanistrum L.). Both of
these plants are very common about all the orchards and both of them are
heavily worked by bees.
During the course of these investigations every effort has been made to
determine the source of cases of poisoning occurring after and before bloom,
and in most cases we were forced to the conclusion that the former was the
source of the pre-blossom poisoning, while the latter accounted for most post-
blossom cases. In a few cases local orchard weeds, as ground ivy (Nepeta huh r-
acea (L.) Trevisan) or adjacent clover fields, may be responsible; but the
former two are evidently the only two species of plants widely involved in cases
of poisoning. The foregoing does not include those cases of poisoning that may
be due to poisoned water obtained from spray or dust covered grass or herbage
growing beneath treated trees.
Some chemical data relating to this subject were secured in 1931 and 1932.
Samples were taken from dandelion, strawberry blossoms, rhododendron and
ground ivy in sprayed, dusted and untreated orchards. In addition, whole flower
heads of dandelion were removed (with a razor) just above the receptacle. In
other cases, apple stamens just below the anthers were similarly removed. In
the case of the strawberry blossom, the whole flower without the sepals was
taken for analysis. Whole flowers from rhododendron and ground ivy were
employed in the tests.
183
184
TABLE No. 40— ARSENIC, AS METALLIC As, FROM DANDELION AND STRAWBERRY BLOOM AND
STAMENS FROM DUSTED AND SPRAYED ORCHARDS
No.
Date of
collection
Source of
material
Material
used
No. in
sample
Arsenic, as
metallic As.
milligrams p.c
Remarks
19
28/31
27/31
27/31
28/31
27/31
27/31
28/31
27/31
28/31
27/31
28/31
3 /6/32
31/5/32
3/6/32
3/6/32
2/6/32
2/6/32
3/6/32
2/6/32
2/6/32
2/6/32
3/6/32
2/6/32
2/6/32
3/6/32
3/6/32
9/6/32
Check
Dusted orchard.
Sprayed orchard
Check
Dusted orchard
Spraved orchard. . . .
Check
Dusted orchard (1)..
Dusted orchard (2)..
Sprayed orchard (1).
Sprayed orchard (2).
Check
Dandelion heads
Dandelion heads
Dandelion heads
Strawberry bloom.
Strawberry bloom.
Strawberry bloom.
Apple stamens
Apple stamens
Apple stamens
Apple stamens
Apple stamens
Dandelion heads. . .
•0002
•0394
1430
12
12 -0061
(No bloom present)
Sprayed .
Sprayed.
Dusted.
Dandelion heads.
Dandelion heads.
Dandelion heads.
Check..
Check..
Dusted. .
Check..
Sprayed.
Strawberry blossoms
Strawberry blossoms
Strawberry blossoms
Rhododendron bloom
Ground ivy
Check..
Check..
Sprayed.
Apple stamens.
Apple stamens.
Apple stamens.
Dusted.
\pple stamens.
Dusted.
Dusted.
Dusted.
Apple stamens.
Apple stamens.
Apple stamens.
25
0-0007
1-40
0-0078
0-0230
nil
0 0068
0-0228
nil
•0044
•0006
•0009
•0011
Taken from untreated area.
Collected while orchard was
being dusted with sulphur-
lead arsenate (90-10j.
Sprayed with "Wet-tex','
previous day, guaranteed
to contain sulphur, not less
than 56%; lead arsenate,
not less than 18%; other
ingredients, not. over 26%
No rain fell between appli-
cation and cutting of
samples.
Same data as No. 2.
Same data as No. 2.
Same data as No 3.
Same data as No. 3.
All cheek material collected
from unsprayed areas, or
un dusted areas.
Bordeaux 8-35-160 plus 6 lbs.
calcium arsenate used on
May 30.
Bordeaux 4^-25-120 plus 5
lbs. calcium arsenate used
on May 30 and 31.
85-15 sulphur-lead arsenate
used at rate of 60 lbs. per
acre on June 2.
nil
nil
•2150
•0041
•0017
•0021
•0016
Same data as No. 13.
Wettable sulphur containing
6 lbs. of calcium arsenate
to 160 gallon tank.
Lime-sulphur-aluminium
sulphate mixture plus 2 lbs.
calcium arsenate per 100
gals.
85-15 sulphur-lead arsenate
applied previous day fol-
lowed by heavy rain.
Same data as No. 13.
Same data as Xo. 13.
Dusted previous day with
sulphur-lead arsenate (90-
10). Heavy rain followed
application.
The fact that samples from both dusted and sprayed orchards show arsenic
present, in quantity likely to cause trouble if gathered by bees, is apparent. The
total arsenic taken from whole dandelion heads was generally greater in the
sprayed than in the dusted orchard, sometimes very much greater. The stamens,
on the other hand, especially the first collection in 1931, sometimes show more
arsenic from the dusted trees. The analysis of the second collection shows a
decidedly smaller quantity of arsenic than the first — this may be duv to the
wind shaking off the sulphur dust, or the uneven dusting. Rain falling after
application evidently removes dust more readily than spray.
The difference in the character of the spray deposit is evidently more
important than the actual amount present. The dust is loosely exposed and
readily gathered by the body hairs and stored in the pollen. The spray forms
a film less readily dislodged and less likely, after drying, to be removed by
bees, except as it becomes dissolved in rain or dewr, when it may be imbibed,
or the film may be softened and lapped up by the bees. This would help to
explain why wre do get serious injury from spray following a rain.
185
: *SXa
186
8. INFLUENCE OF COLONY SIZE AND APIARY SIZE ON BEE
POISONING
Large colonies, because of their greater field force, suffer worse, proportion-
ately, than weak colonies or package bees, as a general rule. Similarly, in large
apiaries our observations indicate, on the whole, greater losses. This may be
because the bees from small apiaries are not obliged to work the whole area
intensively.
9. INFLUENCE OF TIME OF PLACING IN THE ORCHARD
The period for bee poisoning extends from some time before the apple
comes into bloom until some time thereafter, and where poison sprays for apple
maggot are applied it may extend into August. It is frequently more severe
shortly before and shortly after the bloom than during that period, partly
because more spraying or dusting is done at that time and partly because less
bloom is then present and the bees concentrate on bloom growing in and near
the orchards. In most districts, little poison is applied during the period of full
bloom. Some of the early bloom usually gets sprayed, as well as some of the
late bloom. Spraying or dusting during bloom, when practised, is usually though
unfortunately not always, with a fungicide only. Only a small proportion of
growers use poison in the dust during bloom. At this period bloom is abundant
and the bees range widely. Poisoning may occur during bloom as a result of
pre-blossom sprays, especially under certain weather conditions, as already
explained.
The foregoing will clearly indicate that when bees are to be placed in the
orchard for pollinizing purposes, it is advisable, from all standpoints, to do so
only after the early varieties are in bloom, and to remove them before the calyx
application is made. Even this may not avoid injury under all conditions, but
it will, at least, reduce it to a minimum.
10. EVIDENCE OF POISONING AMONG WILD BEES
From the very nature of things, field evidence of poisoning among wild bees
is very hard to obtain. Curiously enough, they may be found nesting in great
numbers in areas where the most severe losses of hive bees have taken place.
Dead brood could rarely be found in the nests, and dead bees never occurred
in large enough numbers in nests to indicate poisoning, though large numbers
may succumb as a result of drowning within the nest. It may be that such
bees never reach the nest, but die in the orchard and so cannot be detected.
The result of analysis of pollen from districts where dusting is generally
practised is therefore of interest.
TABLE No. 41— ARSENIC (As) FOUND IN POLLEN, FROM NESTS OF WILD BEES
Source
Date
Weight
Arsenic
Species
No. 1 — Lakeville
20-6-29
22-6-29
22-6-29
23-6-29
5-7-30
9-7-30
10-7-30
15-7-30
19-7-30
18-7-30
18-7-30
18-7-30
18-7-30
21-7-30
24-7-30
gms.
p.c.
00031
0 0005
0 0019
0 0017
0 0018
0 0002
0 0003
0 0003
0 0026
0 0002
nil
nil
0 0006
nil
0 0002
//. sin Hoc inn
No. 3— Woodville
No. 4 — Lakeville. . .
• •
No. 6— Woodville
-
No. 1 — Long island
01270
10900
1-3830
0-7780
0 0890
2-4454
0 0980
01234
0-4030
0 0747
0-9720
M
No. 2 — Long island
//. cniterus
No. 3 — Long island
II . 8 mi lac in a .
No. 6 — Centreville
No. 7 — Lakeville
II. smilacina
No. 8 — Centreville
II . arctuitus
No. 9 — Centreville
No. 10 — Centreville
II . smilacina
No. 11 — Centreville
No. 12— Blomidon (Shore)...
No. 13— Welsford
II. smilacince
187
;$• ■
mh'
! ,-,*:;
1 *-;
'♦ ' '
t
■■*&. .
1 ♦*
'p*>j*
♦Vj*
'-
188
The fact that such a large proportion of the pellets, collected at random,
contain measurable amounts of arsenic would lead one to suppose that poison-
ing among wild bees should be common; but if so, it is difficult to demonstrate,
and over the period studied we have not been able to detect any diminution in
the effective population traceable with certainty to this cause. Much more
careful studies over a longer period would be necessary before we could speak
with confidence on this point.
11. SUMMARY OF POISON TESTS
(a) The question of poisoning of bees from poison sprays and dusts used in
orchards is obviously important from the standpoint of their utilization for
pollination purposes. A survey of the situation shows that the hive bee popula-
tion has been greatly depleted during recent years and the evidence points
clearly to the conclusion that this has been directly due to the use of poison
sprays and dusts. With the advent of dusting, many apiaries were completely
wiped out, so that no large commercial apiaries, except those that were removed
during the danger period, remained. The growing practice of using larger
spray outfits, resulting in heavier applications, and a different type of spray
nozzle resulting in greater drift to surrounding vegetation, has increased the
incidence of poisoning from this cause.
(6) The most important fungicides used are (1) lime sulphur in various
combinations using calcium or lead arsenate as a poisoning ingredient; (2)
copper sulphate in the form of Bordeaux mixture or copper-lime dust, to which
one of the foregoing poisons has been added; (3) sulphur dust usually in com-
bination with lead arsenate, and (4) nicotine sulphate in liquid form or in the
form of a " contact dust," with hydrated lime as a filler. Under orchard con-
ditions it would appear that arsenic in the form of lead or calcium arsenate is
the main source of bee poisoning in these mixtures; but even sulphur dust alone
may cause trouble, though not comparable to that caused by arsenicals. Clear
evidence of repulsion from copper sulphate, lime sulphur and nicotine is obtained
from tests under controlled conditions; but under orchard conditions this repul-
sion appears to be temporary and does not prevent serious losses from occurring.
(c) Arsenical poisoning results in partial to complete paralysis and is first
evidenced by "crawlers" appearing in front of the hive; bees come together
in bunches; the abdomen is distended and severe dysentery makes its appear-
ance, followed by death of adult bees. This is soon followed by death of larvae
and pupae. Symptoms of sulphur poisoning are similar but less severe. Clear
cases of copper or nicotine poisoning under field conditions were not obtained.
(d) When the internal arsenic in bees is greater than -00004 mg. of metallic
arsenic per bee, poisoning may be expected, definitely so. when higher than
•0008 mg. is detected.
(e) Field observations, supplemented by chemical analyses of numerous
samples, lead to the following conclusions: —
(i) All sprays containing an arsenical as an ingredient were dangerous
when applied during bloom.
(ii) Only sprays or du^ts containing arsenicals resulted in dead brood.
(iii) The combination causing the most sudden and complete mortality
was sulphur-lead arsenate in dust form.
(iv) In general, less mortality resulted from sprays and dusts containing
copper or nicotine as an ingredient along with the arsenical.
(v) Sulphur dust free from poison may cause death oi bees, but to what
extent this occurs under field conditions is not clear. Evidently it is
much less deadly than arsenicals, besides bein^r less sudden and com-
plete in its action.
189
(vi) Field observations, supplemented by chemical analyses indicated that
the greatest poisoning usually occurs just previous to and just after the
main bloom. Nevertheless, no time during the season from May until
August is completely safe. Sprays for apple maggot applied as late as
August sometimes cause severe poisoning.
(/) Weather conditions have an important bearing on the incidence of
poisoning among bees. Very severe poisoning has been noted even when pre-
vailing conditions are cool and wet, and some of the worst cases have taken place
following brief bursts of fine weather intervening between periods of broken
weather. On the other hand, attempts to secure poisoning by placing a few
hives in an orchard, sprayed or dusted with the most deadly mixtures when the
weather was optimum for flight, have sometimes resulted in failure. Several
factors may account for this: —
(i) Bees after several days confinement greedily seek moisture from
poisoned leaves, petals and poison-covered herbage growing beneath
trees, which analyses show to contain large quantities of arsenic,
(ii) During confinement, supplies are depleted and at the first opportunity
bees are very active in collecting new stores near at hand, resulting in
much poisoned pollen being brought in.
(iii) During periods of weather favourable for flight, poisoned pollen may
be collected but not consumed, and this may be fed upon during periods
of confinement.
(g) The main source of poisoning of bees and brood is evidently pollen,
but, under certain conditions, drop water from sprayed leaves, petals or herbage
growing in the orchard may be a very important factor. Some writers mention
nectar, but our analyses show either no poison in the nectar or only minute
amounts, and the possibility that this may be due to contamination in gather-
ing the sample is not entirely excluded in some cases. Nevertheless, even the
minute quantities detected may be deadly to very young larvae.
(h) It is often assumed that poison applied to the fruit bloom is the chief
or sole cause of loss, but this is not the case. Severe cases of poisoning before
and during bloom are sometimes attributable to poison obtained from dande-
lion bloom growing in or near the orchard. Later cases of poisoning were mainly
traceable to wild radish ; but many other plants may serve as sources of poison-
ing due to the drip or drift of poisoned sprays or dusts.
(i) It was noticed that large colonies and large apiaries often exhibited
the most severe poisoning.
(j) Least trouble was experienced when bees were not placed in the orchards
until the early varieties were in bloom after the application of the " pink " spray
and taken away before the beginning of the " calyx " spray. For reasons
already given, however, this did not eliminate all cases of poisoning, though
it reduced them to a minimum. It is impossible, however, to maintain apiaries
anywhere in the entire fruit belt at any time from May until August, without
incurring some risk of loss.
(k) Samples of pollen taken from the nests of solitary bees showed ponder-
able amounts of arsenic, more than enough to destroy the larvae of hive bees.
Evidence of depletion of the solitary bee population from this cause is difficult
to secure and requires further observation.
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60796—13
INDEX
Acknowledgments, 12-13
Andrena, as pollinators, 24, 92; effect of tem-
perature on activity, 111; constancy of, 133
Andrena carlini Ckll., as pollinator, 94
Andrena ivilkella Kirby, as pollinator, 94
Anthomyids, as pollinators, 92
Apis, as pollinators, 92; constancy of, 133
Apis mellifica L., as pollinator, 92
Apple industry in Nova Scotia, 13-18
Apple scab, see Venturia inaequalis (Cook)
Winter
Apple pollination, experimental studies in,
31-90
Apple varieties, classification of (table), 8;
genetic constitution of, 26-27; chromosome
numbers of (table), 26-27
Arsenic obtained from, bees under cage con-
ditions (table), 169; larvae (table), 169;
summary of results from bees (table), 170;
pupae (table), 170: bees, field samples
(table), 173; pollen (table), 180; nectar
(table), 180; rain water (table), 182; dan-
delion and strawberry (table), 184; pollen
in nest of wild bees (table), 186
Arsenical poisons, effect of. on bees, 164;
effect of, on bees under field conditions, 175
Auchter, E. C, on pollination of Cox Orange,
51; pollination of King, 60
Baldwin, results of other workers, 48; selfing
tests, 48; as female parent, 48; as male
parent, 48; evidence from tented series, 48,
50; summary of results with all varieties,
50; general summary, 50.
Ballard, W. E., on pollination of Stark, 78
Barclay, R. A., on bees as pollinators, 135
Bees, bumble, discussion of, 93; species list,
94; solitary, species list, 94; discussion of,
94-96; as pollinators under controlled con-
ditions, previous work with, 31; experiments
with, 32-34; influence of nectar secretion
and availability of pollen on activity of, 131-
132
Bee activity, at different diurnal periods re
temperature and humidity (table), 119; in
relation to nectar secretion (graph), 132
Bee colonies, problems in distribution and
number, 140-156; type required for pollina-
tion, 142-148; observation on strength of
different types, 144-148; strength of over-
wintered May 6/31 (table), 145; strength
of over-wintered, during fruit bloom, 146;
types of experimental studies in, 146-148;
method of placing, 154-155; time of placing,
155-156; securing of, 156-157
Bee counter, photo-electric, description of,
119-121
Bee poisoning, list of common poisons, 164;
lethal dosages, 165-166; technique of chemi-
cal tests in, 166-167; repulsion tests, 171;
feeding tests, 171-172
Bee, hives, discussion of, 93; utilization of. as
orchard pollinators, 134-157; historical re-
view, 134-135; experimental use of, 136-
138; when to be used, 140; flight and
concentration of, 148-155; effect of physical
features on flight and concentration, 151;
effect of weather conditions on flight and
concentration, 151; area of activity, 151;
general conclusions, 157
Bees, hive and wild, relative abundance of.
during bloom, 108-109; count (table), 109;
artificial increase and distribution, 109;
comparative effect of climatic factors on,
109-125; effect of temperature on, 111-113;
effect of sunlight and solar radiation on
activity of. 113-117; effect of wind on ac-
tivity of, 117-118; effect of humidity on
activity of, 118; effect of time of day on
activity of, 118-119; effect of climatic factors
on, supplementary data of, 119-125; number
of visits of, 125; pollen gathering habits of.
126-131; comparative constancy of. 132-133;
distribution and concentrations, 133; gen-
eral summary, 133-134
Blenheim, experimental results of other
workers, 76; of selfing tests, 76; as female
parent, 76; as male parent, 76: summary of
all varieties, 77; general summary of, 78;
fruit set of tented vs. untented trees, 78;
effect of various male parents on (fig.), 81
Blenheim, Stark cross, fruitfulness of differ-
ent types of (table), 81
Bloom, effect of condition on bee activity.
149; varietal atractiveness of, 149; effect of
masses of, 150; availability of other bloom,
150; amount available in relation to popula-
tion present, 151-154
Blooming period, of different varieties
(charts), 83
Blossoming and fruiting habits of four stand-
ard varieties (table), 30
Bonnier, G., on area of activity of hive bees,
151
Bochert, A., bee poisoning, 161
Bouquets, use of orchard duster with, 87-88
Bourne, A. I., bee poisoning, 160
Bremus, constancy of, 133; as pollinators, 92
Britton. W. E. and Viereck, H. L., on insects
as pollinators, 91
Bud-moth, see Tmeiocera oceUana Schiff.
Burrell, A. B. and King, G. E., on pollen-
coater, 87
Chironomidae, as pollinators, 93
Chittenden, F. J., pollination of King, 60
Climatic factors, comparative effect of, on hive
and wild bees, 109-125
Coke, J., fertilizing and spraying, 18, 23
Copper, effect of, on bees, 165
Corrie, L. G., pollination of Cox Orange, 51
Cowan, T. W., bees and water, 181
195
196
Cox Orange, results of other workers. 51;
selfing tests. 51; as female parent, 51; as
male parent. 51; evidence from tented
series. 51; summary of results with all
varieties. 53; general summary, 53; fruit-
set of tented vs. untented trees, 78
Crane, J. E.. pollination of Cox Orange, 51
Crane. M. B. and Lawrence, W. J. C, un-
fruitfulness, 24 and 26; generational ster-
ility, 28; incompatibility, 28; pollination of
Cox Orange, 51; pollination of King, 60;
pollination of Blenheim, 76
Crosses, with standard varieties (table), 64;
fruitfulness of different types of (table).
65; Blenheim and Stark, fruitfulness of
different types of (table), 81
Cross-fruitful, definition, 24
Cross-<pollination, definition, 24; conditions
for, 31
Cross-unfruitful, definition, 24-25
Cruciferae, activity of hive bees on, 151
Darlington, C. D. and Moffet, A. A., chromo-
some behaviour in the apple, 26
Davis, J. J., on bees as pollinators, 135
DeOng. E. R., on the activity of honey bees,
110; on bees as pollinators, 135; on type of
colony for pollination, 143; on number of
colonies per acre of orchard, 152
Detjen, L. R., on morphological sterility, 28
Diptera, on apple bloom, 99
Doane, R. W., bee poisoning, 159
Dyce, E. J., number of blossoms visited In-
bees, 125
Effective population, definition of, 100; esti-
mation of, 100, 102
Einset, O.. on incompatibility. 28; corre-
lation between seed content and weight, 29;
germination of pollen, 42
EristaliSj as pollinator. 92
Earrar, C. L., on bee trapping. 119; on type
of colony for pollination. 145; on method
of securing colonies, 156
Fertilization, definition, 24
Field experiments, with hive bees. 137-138
Filmer, R. 8., on pollen carriers. 128; on type
of colony for pollination, 144
Flies and other insects, as pollinators, 96. 99
Forced draft pollination, results of tests in
(table), 88
Foreword, 11-12
Fox-Wilson, G. F., on insects as pollinators. 92
Fruit belt in Nova Scotia, map of. 13: geo-
graphical position of. 13-15; climate of, 15;
apple varieties grown in. 15-16; quantity
grown in (table), 17; varietal percentage of
total crop in, 17; average yields. 17-18
Fruitful, definition, 24
Fruitfulness, seed content in relation to. 65;
of different types of Blenheim and Stark
crosses (table). 81
Fruiting habits of four standard varieties for
four years, 30
Fruit production, factors other than pollina-
tion affecting, general. 18; climatic factors,
19-22; nutritional factors, 21-22; patho-
logical factors, 22-23
Fruit-set, in proportion to bloom. 29; relation
of, on tree to limb or spur, 86
Fungicide dust, effect of, on bees under field
conditions, 173-174
Gates, B. N\, on the use of bees as pollinators,
134
Golden Russet, results of other workers, 53;
selfing tests, 53; as female parent, 55; as
male parent, 55; summary of results with
all varieties. 55; general summary, 56
Gowan. J. W., pollination of Northern Spy, 63
Gravenstein, results of other workers. 56;
selfing tests, 56; as female parent, 56; as
male parent, 56; evidence from tented
series, 58; general summary, 58; summary
of results with all varieties, 58
Green apple bug, see Lygus communis Knight
Halictus, as pollinators. 24, 92; effect of tem-
perature on activity, 111; constancy, 133
Halictus aicuatus Robt.. as pollinator, 94
Halictus craterus Lov., as pollinator, 94
Halictus lerouxii Le P., as pollinator, 94
Halictus smilacinae Robt., as pollinator, 94
Hand pollination, studies in, 70-72; as an al-
ternative to the use of bouquets, 87
Hedrick, M. P.. effect of temperature on
fruit-set. 19
Hendriekson, A. X., on bees as pollinators. 135
Hilgendorff, O.. and Borchert. A., bee poison-
ing. 160
Hockey. J. F. and Harrison. K. A., carriage
of pollen by wind, 47
Hooper. C. H., pollination of Cox Orange. 51:
insects as pollinators, 92: number of colonies
per acre of orchard, 152
Hewlett, F. S.. nutritional factors. 21; on
g( nerational sterility. 28; on incompatibil-
ity. 28; Baldwin pollination, 48
Humidity, effect of. on bee activity, 118
Hutson, K.. bees as pollinators, 31: on insecl
pollinators. 93; activity of honey bees. 110;
type of colony for pollination. 144: flight
and concentration of bees, 148; method of
placing colonies, 154
Incompatibility, definition. 26; discussion of.
28
Insect pollinators, field studies in. 9 and 91-
157: introduction. 91; general. 91. 100: his-
torical. 91-93; relative value of. 100; method
of study. 100
Inter-fruitfulness. studies in. 7-8: of standard
varieties, studies in. 37-74: of standard
varieties, summary, 69: general results and
conclusions from studies in. 73; chart oi
some standard varieties, 85
King, results of other workers, 58, 60: selfing
tests, 60; as female parent, 60; as male
pa] cut. Oi): evidence fi two tented sei i< -
61; summary of results with all varieties,
(il: general summary, 61
Knowlton. H. E.. effect of temperature on
fruit-set, 19
Kobel. F., chromosome behaviour in the apple.
26; generational sterility. 28; false par-
thenocarpy, 29
Lewis. C. 1. and Vincent, ('. C, pollination of
King. 60
Langstroth, L. 1.. bees and water. 181
Lattimer, L. P., pollination experiments, -1
Lygus communis Knight. 22
197
Lundie, A. E., on the activity of honey bees,
110, 112, 113: on bee flight, 125; bees as
pollinators, 136
MacDaniels. L. H., on flight and concentration
of bees, 148; on varietal preference of bees,
131; on activity of honey bees, 111; fruit-
set, 29; Baldwin pollination, 48; pollination
of Northern Spy, 61; on over-pollination,
86; on hand-pollination, 87
MacDaniels. L. H. and Furr, J. R., destruction
of bloom by fungicides, 23
MacDaniels. L. H. and Heinicke. H. A., on
nutritional factors, 21; on Baldwin polli-
nation, 48
Macoun, W. T., bees as pollinators, 31
Manglesdorf, on incompatibility, 28
Marshall, R. E., et al., on method of securing
colonies, 156
Marshall, R. E., Johnson, H. D. et al., pollina-
tion of Northern Spy, 61; pollination of
Stark, 78; on activity of honey bees, 110;
on methods of placing colonies, 154
Marshall, R. E., Johnson. H. D., Hootman,
H. D. and Wells, H. M., on bees as polli-
nators, 135-136
McCulloch, J. W., on number of blossoms
visited by bees, 126
Mclndoo, H. E., tent experiments in bee
poisoning, 166
Mclndoo. H. E. and Demuth, G. H., on bee
poisoning, 158, 160; on repellent action of
sprays on bees, 165
Merrill, J. H., bee poisoning, 159
Minderhoud, A., on area of activity of hive
bees, 151
Moffet, A. A., chromosome behaviour in the
apple, 26
Morphological sterility, 28
Morris, O. M.. bees as pollinators, 31; Bald-
win pollination, 48; pollination of Gravenr
stein, 56; pollination of King, 60; pollina-
tion of Stark, 78
Mouldy core, occurrence of, 66; occurrence and
cause of, 69
Murneek, A. E., effect of weather on fruit-
set, 19; on type of colony for pollination.
144; on number of colonies per acre of or-
chard, 152; on method of placing colonies,
Museidae, as pollinators, 93
Nebel, B., chromosome behaviour in the apple.
26
Nectar, secretion, and availability of pollen,
influence on bee activity, 131-132; secretion
in relation to bee activity (graph), 132;
as source of bee poisoning, 180
Ncpeta hederacea (L.) Trevisan, as source of
bee poisoning, 182
Nicotine, effect of, on bees, 165; effect of, on
bees under field conditions, 175
Northern Spy, results of other workers, 61,
63; selfing tests, 63; as female parent, 63;
as male parent, 63; evidence from tented
senes,_ 63-64; summary of results with all
varieties, 64; general summary, 64
Nutritional competition, on tented trees
effect of (table), 86
Observation stations, 102, 105
Orchard the planning of, 82-85; suggested
plan for five-variety (fig.), 84; suggested
plan for four-variety (fig.), 85
Orchard duster, velocity of current from in
relation to distance from (table). 89
O'Smia lignaria Say, as pollinator, 92
Overholser, E. L., pollination of Baldwin. 48;
Gravenstein, 56; King, 58
Over-pollination, 86
Park, O. W., on activity of honey bees, 111;
on bee flight, 125
Parker, R. L., on pollen gathering habits of
bees, 126, 128
Parthenocarpy, definition, 26; occurrence of,
29
Phillips, E. F., the activity of honey bees,
110; bees as pollinators, 136; type of colony
for pollination. 144; method of securing
colonies, 156; bees and water, 181
Philp, G. S. and Vansell, G. H., type of colony
for pollination, 143; number of colonies per
acre of orchard, 152; method of placing
colonies, 154; method of securing colonies,
157; bee poisoning, 161
Poisoning of bees, studies in, 158-189; intro-
duction, 158; historical. 158-161; develop-
ment of, 161-163; experiments in, 163-166;
tent experiments in, 166-172; studies from
commercial orchards. 172-178; influence of
weather on, 178-179; sources of (food), 180-
182; sources of (plants), 182, 184; influence
of size of colony and of apiary on, 186; in-
fluence of time of placing in orchard on, 186;
evidence of, amongst wild bees, 186, 188;
summary of poison tests on, 188-189
Pollen, germination of (table), 41-42; germ-
ination, optimum temperature for, 44; inter-
fruitf ulness of, 69; different varieties, diag.
showing value of, on standard varieties, 70;
different varieties, graphs showing value of,
on Spy, Blenheim, Stark, and Gravenstein,
71; on Golden Russet, King, Baldwin, and
Cox Orange, 72; temporary provision of,
87; unfruitful, inhibiting effect of, 89-90;
as source of bee poisoning, 180
Pollenrcoater, 87
Pollen-gathering, habits of hive and wild bees,
126-131
Pollen supplies, source of, 156
Pollen tests, method, 40-41; results, 41-47
Pollination, and fertilization, process of, 5-6;
definition of, 24-25; problem of, 6-7 and 25;
results of experiments, 47; tests with Blen-
heim and Stark, 74-82; time necessary for,
140-142; effect of length of exposure on
(table), 141; influence of length of ex-
posure on (table), 142
Pollinator, definition, 24
Pollinizers. arrangement of, 9-10; definition of,
24
Pollinizing bouquets, 87
Price, W. A., bee poisoning, 159
Raphanus Baphanistrum L.. as source of bee
poisoning, 182
Rawes, A. N. and Wilson, G. T., on insects
as pollinators, 92
Root, A. I. and Root, E. R., bee keeping, 181
Roscoe, M. V., acknowledgment unpublished
data, 12; chromosome behaviour in the
apple, 26
198
Ryihin, V. A., chromosome behaviour in the
'apple, 26
Sandsten. E. P., relation of nutrition to qual-
ify of pollen, 22
Sax, K., pollination of Golden Russet, 53; on
bees as pollinators, 135
Scarabaeidae, as pollinators, 93
Seed content, relation to fruit-fulness, 65; re-
lation to weight, 65; morphological abnor-
malties associated with, 68-69
Self-fertile, definition, 25
Self-fruitful, definition, 24
Self-fruitf ulness, seasonal variation in, 90;
due to technique, 90
Self-pollination, definition, 24
Self-sterile, definition, 25
Self-unfruitful, definition, 24
Simmins, S.. on pollen and nectar gathering
habits of bees, 127
Solar radiation apparatus, relative response
of cell and filters of, 113
Sprays, repellent action on bees, 165
Stark, experimental results, of other workers,
78; selling tests, 78; as female parent, 78,
80; as male parent, 80; all varieties, sum-
mary of, 80; general summary of, 80; effect
of various male parents on (fig.), 81
Stark-Blenheim cross, fruitfulness of different
types of (table), 81
Sterility, generational, 28; morphological,
definition. 26; definition, 25; generational,
definition, 26
Sulphur, effect of, on bees, 165
Sulphur dust, effect of, on bees under field
conditions, 174-175
Summary, popular, 5-10
Sunlight and solar radiation, effect on activ-
ity of hive and wild bees, 113-117
Sutton, I., pollination of Cox Orange, 51
Syrphus, as pollinators., 92
Taraxacum officinale Weber, activity of bees
on, 151
Temperature, effect on hive and wild bees,
111-113; relation of hive bee activity in
apple bloom to (table), 111.
Tent experiments, general results of, 34-36;
humidity and temperature records of, 35;
with hive bees, 136-137; results of (table),
136
Tent studies, summary of (table), 36; in in-
terfruitfulness, 69
Tietz, H. M., bee poisoning, 159
Time of day, influenced of, on bee activity,
118-119
Tmetocera ocellana Schiff., 22
Top-working, plan for Blenheim (fig.), 84
Trachandrena, as pollinators, 92
Trifolium, activity of hive bees on, 151
Unfruitf ulness, other causes of, 10; causes of,
26
Vincent, C. C, pollination of Gravenstein. 56
Venturia inaeqnalis (Cook) Winter, 22
Water, as source of bee poisoning, 181-182
Webster, F. M., bee poisoning, 158
Weed, A. C, on bees as pollinators, 134-135
Wellington, Stout et al., pollination of Graven-
stein, 56; pollination of King, 60
Wind, effect on bee activity. 117-118
Wind velocity, inside and outside tent, com-
parison of (table), 89
Woodrow, A. W.. on honey bee activity. Ill;
on types of colony for pollination, 14.1
OTTAWA
J. O. PATENAUDE, ACTING KING'S PRINTER
1933
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