CALIFORNIA
AGRICULTURAL EXTENSION SERVICE
CIRCULAR 62
APRIL, 1932
Pollination of Deciduous Fruits
by Bees
G. L. PHILP and G. H. VANSELL
Cooperative Extension work in Agriculture and Home Economics, College of Agriculture,
University of California, and United States Department of Agriculture cooperating. Distributed
in furtherance of the Acts of Congress of May 8 and June 30, 1914. B. H. Crocheron, Director,
California Agricultural Extension Service.
THE COLLEGE OF AGRICULTURE
UNIVERSITY OF CALIFORNIA
BERKELEY, CALIFORNIA
Digitized by the Internet Archive
in 2011 with funding from
University of California, Davis Libraries
http://www.archive.org/details/pollinationofdec62phil
POLLINATION OF DECIDUOUS FRUITS
BY BEES
G. L. PHILPi and G. H. VANSELL2
INTRODUCTION
Most fruit growers are familiar with investigations and field
studies in cross-pollination. Beekeepers, however, are generally as
unacquainted with the details of fruit pollination as are the fruit
growers with bee problems. This circular attempts to summarize the
results of deciduous fruit pollination studies and to point out some
bee habits and structures, with special reference to the collection and
storage of pollen. Such a paper may perhaps serve as a practical
handbook for reference, especially in the field, and facilitate satis-
factory pollination arrangements between fruitmen and beekeepers.
The pollination data have been prepared by the first author from
material contained in various California Agricultural Experiment
Station publications, most of which are now out of print, and sup-
plemented with unpublished data from the Division of Pomolgy.
The second author has prepared the material on bee habits and
structures.
POLLINATION SUMMARY OF DECIDUOUS FRUITS
Among the causes responsible for nonbearing of deciduous fruits
are lack of vigor in the tree, presence of injurious insects and
diseases, unfavorable weather at blossoming time, winter injury, lack
of pollination, and inability of the pollen to fertilize the ovule. This
discussion will deal only with pollination as a cause of nonbearing,
it being assumed that the orchard is planted in a favorable location
and that the trees are kept in normal vigor and free from serious
insect and disease troubles.
1 Associate in Pomology.
2 Associate in Entomology ; resigned.
4 California Agricultural Extension Service l^'^- 62
The following' definitions may clarify the discussion :
Pollination^: the transfer of pollen to the stigma; or, in a large sense,
the distribution of pollen. Pollination may be accomplished by insects, wind,
gravity, water, artificial methods (in experimental work), and birds.
Pollinizer : a plant (tree) used to furnish pollen. The male parent.
Fertilisation: the union of the male germ cell, contained in the pollen
grain, with the female germ cell or egg in the ovary.
Fruitful: the term applied to a plant that sets and matures fruit.
Unfruitful or barren: terms describing a plant or variety that is unable
to set fruit and mature it.
Fertility: the ability not only to set and mature fruit but to develop
viable seed.
Sterility: the inability to set and mature fruit with viable seed.
Self -fruitful: the term applied to a plant that sets and matures fruit with
its own pollen.
Self -unfruitful or self -barren: terms describing a plant that is unable to
set fruit and mature it with its own pollen.
Inter-fruitful : the term applied to a variety capable of setting and matur-
ing fruit when pollinized with a different variety.
Inter-unfruitful or inter-barren: terms describing a variety not capable of
setting and maturing fruit when pollinized with a different variety.
The reasons for nonbearing, from a pollination standpoint, are
not all known. Some of them, aside from weather conditions, are
incompatibility, imperfection or degeneration of sex organs, slow
growth of the pollen tube, and premature or delayed pollination.
The fruit grower has a pollination problem with almonds, cherries,
plums and prunes, apples, pears, and berries. In general, apricots,
peaches, and walnuts set well with their own pollen and hence
present no difficulties from this standpoint. The J. H. Hale peach,
however, is self -unfruitful and must be interplanted with some other
variety. Recent studies indicate that some varieties of walnuts in
certain years do not mature the staminate and pistillate flowers at
the same time and therefore, under these conditions, cannot pollinate
themselves.
With the fruits having a pollination problem, the grower must
consider the following factors in selecting the pollinizers : coincidence
of bloom, amount of pollen produced, germinability of pollen, com-
mercial value of pollinizer, succession in ripening, and regularity of
production of the pollinizers used. Varieties which do not blossom
at the same time will not cross-pollinate each other.
3 Pollination experiments and investigations include not only the study of
the transfer of pollen but also studies of fruit setting associated with pollen
transfer and fertilization. In any mention of pollination studies and problems,
this broader definition will be intended.
1932]
Pollination of Deciduous Fruits by Bees
Most fruits with showy flowers (fig. 1) require insects to carry the
pollen from flower to flower. Bees are the most important insects
for this work. The grower should therefore have plenty of bees in
the orchard during the blossoming period.
Fig. 1. — Diagram of orange flower in longitudinal section showing location
of typical floral parts. The orange blossom has been used rather than the flower
of a deciduous fruit because it shows the nectary more conspicuously.
The California Agricultural Experiment Station has conducted
pollination experiments with certain fruits. The results may be
summarized as follows :
ALMONDS
The following varieties of almonds are self-unfruitful under
California conditions and hence should not be planted in blocks of
one variety:
Big White Flat
Golden State
King
Nonpareil
California
Harriott
Klondike
Peerless
Drake
I. X. L.
Lewelling
Eeams
Eureka
Jordan
Ne Plus Ultra
Texas
Some varieties of almonds are inter-unfruitful-
following :
Nonpareil with I. X. L.
Languedoc with Texas
-for example, the
California Agricultueal Extension Service [Cte, 62
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1932]
Pollination of Deciduous Fruits by Bees
Almonds may be classed as early or late in time of blossoming, as
given below. Nonpareil has been given in both lists since it occupies
a position about midway.
Early
Late
Big White Flat
Lewelling
Dickinson
Nonpareil
California
Ne Plus Ultra
Drake
fleams
Harriott
Nonpareil
Eureka
Sellers
I. X. L.
Peerless
Golden State
Texas
Jordan
Princess
Languedoe
King
Silver Shell
Klondike
The accompanying chart, figure 2, gives the average blossoming
dates of certain almond varieties. The date of bloom is dependent
upon many factors, such as soil, season, and location.
With the exception of the above-noted cases of inter-unfruitf ulness,
any variety in either of the above lists may be used in most instances
as a satisfactory pollinizer for any other variety in the same list.
Table 1, compiled from the experiments of Tufts and Philp,^ sum-
marizes the pollination requirements for almonds. Variety names at
the left of the chart indicate the tree, and the names across the top
indicate the pollen used. For example, if pollen from the variety
Drake were used on a tree of the variety California a good set would
result, as indicated by the symbol G in the table.
APPLES
Although this is not a complete list, apple varieties may be segre-
gated according to their pollination requirements as follows:
Self-fruitful
Baldwin
Early Harvest
Grimes Golden
Oldenburg
Wagoner
Wealthy
Yellow Newtown
Yellow Transparent
Self -unfruitful
Arkansas
Arkansas Black
Delicious
Fameuse
Gravenstein
Mcintosh
Northern Spy
Khode Island Greening
Stark
Stayman
Twenty Ounce
White Pearmain
Winesap
Winter Banana
Yellow Bellflower
Doubtful
Ben Davis
Esopus Spitzenburg
Gano
Jonathan
Eome Beauty
Tompkins King
York Imperial
4 Tufts, W. P., and G. L. Philp.
Bui. 346:1-35. 1922.
Almond pollination, California Agr. Exp, Sta.
California Agricultural Extension Service
[Cur,. 62
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1932] Pollination of Deciduous Fruits by Bees 9
The varieties in the self -fruitful list will generally produce larger
crops when cross-pollinated. Under most conditions, however, com-
mercial crops will result when they are planted in solid blocks
(self -pollinated).
The varieties in the unfruitful list are unsafe to plant alone and
should be interplanted with some other variety for cross-pollination.
The varieties in the doubtful list will in some years, under certain
conditions, produce commercial crops. The evidence indicates, how-
ever, that better commercial crops will result if provisions for cross-
pollination are made.
Few cases of inter-unfruitfulness appear among apple varieties.
Winesap, Arkansas, Arkansas Black, and Stayman seem to be inter-
unfruitful and should therefore not be planted together. The Arkan-
sas, Stayman, and Gravenstein are generally unsatisfactory pollen
producers, a fact which makes them undesirable pollinizers for other
varieties. Except for the cases indicated above, varieties which
blossom together will cross-pollinate each other. The Delicious and
Yellow Newtown seem to be the best varieties to, cross-pollinate the
Gravenstein.
CHERRrES
All commercial varieties of sweet cherries are self-unfruitful.
Tests show that the following are self-unfruitful under California
conditions :
Abundance Burbank Mezel
Advance Chapman Napoleon (Royal Ann)
Bing Centennial Pontiac
Black Heart Cleveland Rockport
Black Republican Early Purple Windsor
Black Bigarreau Lambert Wood
Black Tartarian Major Francis
Some varieties of sweet cherry are inter-barren — for example, the
following, under certain conditions :
Bing, Lambert and Napoleon with each other
Rockport with Advance
Early Purple with Rockport
There are, apparently, different strains of certain cherry varieties
or else different varieties so similar as to be indistinguishable. This
condition exists particularly with Black Tartarian, of which there
are at least five strains which vary greatly in their ability to pollinize,
especially the Napoleon. More than one strain of Black Republican,
from a pollination standpoint, exists.
10
California Agricultural Extension Service [C^ir- 62
No entirely satisfactory pollinizer has as yet been determined for
Napoleon. In most cases, however, certain strains of Black Tartarian
and Black Republican yield satisfactory results. Findings in Oregon
show that the long-stemmed Waterhonse variety is a fairly good
pollinizer for Napoleon.
Cherry varieties may be classed as early or late blossoming, as
follows :
Early Late
Advance Burbank Bing Pontiac
Black Heart Chapman Lambert Rockport
Black Eepublican Early Purple Napoleon
Black Tartarian
PERioPorErT-ECTivE Blooai o{- Cuuf\m CuiiRRy Varieties
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Black tartaria;i a
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Black Repwduc/^>n a
PoHr\f\c 4
Bl/iG 4
PiCWOLtOH 4
rockfort 3
Lambert a
•■•■■■■•■■■■■■■■■■.
Fig. 3. — The period of effective bloom of certain cherry varieties, covering a
period in nearly all cases of four years. The number of years averaged is shown
in a separate column for each variety. (From Bui. 385.)
Black Tartarian and Black Republican generally overlap enough
to pollinize most varieties in the second column.
The accompanying chart, figure 3, gives the average period of
effective bloom for certain cherry varieties. The term effective hloom
indicates the length of time the tree is in conspicuous blossom.
Table 2, compiled from the experiments of Tufts and Philp,^
summarizes the results of cherry pollination. In some cases different
results may be secured but in general this information will apply.
5 Tufts, W. P., and G. L. Philp. Pollination of the sweet cherry.
Agr. Exp. Sta. Bui. 385:1-28. 1925.
California
1932]
Pollination of Deciduous Fruits by Bees
11
TABLE 2
Chart Showing Pollination Compatibilities of Sweet Cherries*
Source of pollen
Variety
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F— Fair P— Poor O— No affinity
), with supplementary data prepared by G. L. Philp,
PEARS
Twenty-six varieties of pears have been tested by the Pomology
Division under various California conditions.
Only the Hardy variety has proved to be self -fruitful under all
conditions and during all seasons. Fifteen of these twenty-six
varieties tend, under certain conditions, toward self-fruitfulness.
Bartlett pears are, to a certain extent, self-fruitful under valley
conditions, and, in most instances, self -barren under foothill conditions.
Winter Nelis showed a tendency toward self-unfruitfulness under
all conditions tested.
No cases of inter-barrenness have been found to exist between pear
varieties.
A summary of the pollination results secured by Tufts and Philp^
segregates pear varieties into three groups, as shown in table 3.
6 Tufts, W. P., and G. L. Philp. Pear pollination. California Agr. Exp. Sta.
Bui. 373:1-36. 1923.
12
California Agricultural Extension Service
[Cm. 62
Those varieties in the doubtful list, although setting satisfactory
crops under certain conditions, should for best crops be interplanted
with some other variety.
TABLE 3
Summary of Pollination Eesults with Pears
Self-barren
Self-fruitful
Doubtful
Variety
Years
tested
Variety
Years
tested
Variety
Number
years
self-
fruitful
Number
years
self-
barren
Alencon
2
2
1
1
2
3
1
3
Cornice
4
1
3
3
Angouleme
1
2
5
1
1
2
2
1
1
1
1
1
1
3
1
Bloodgood
Flemish Beauty
Hardy
1
B. S. Fox
Bartlett
2
Comet
Howell
Bosc
1
Forelle
Clapp Favorite
Clairgeau
1
LeConte
2
Madeline
Col. Wilder
2
Winter Nelis
2
Easter
2
Gifford
1
Glou Morceau
Kieffer
1
4
P. Barry
2
Seckel
1
Pears have, in most cases, a comparatively short period of bloom.
The varieties tested may be divided roughly as early and late
blossoming, as follows :
Early
Late
Alencon
Angouleme
An j ou
Bartlett
Bartlett
Clairgeau
Bloodgood
Bosc
Clapp Favorite
Easter
B. S. Fox
Comice
Dana Hovey
Howell
Comet
Glou Morceau
Forelle
Le Conte
Gifford
Winter Bartlett
Kieffer
P. Barry
Hardy
Winter Nelis
Seckel
Col. Wilder
The following varieties, tested under California conditions, have
proved to be successful poUinizers for the Bartlett :
Angouleme
Anjou
Bosc
Clairgeau
Howell
Hardy
Comice
Dana Hovey
Easter
Forelle
Winter Nelis
1932]
Pollination of Deciduous Fruits by Bees
13
PLUMS AND PRUNES
Nearly all Japanese plums are self-unfruitful. Methley, Climax,
Beauty, and Santa Rosa are partially self-fruitful. Like the rest,
however, these four varieties set much better when interplanted for
cross-pollination purposes. The self-barren list of Japanese plums
follows :
Abundance
Duarte
Prize
Amador
El Dorado
Satsuma
Apex
Formosa
Sultan
Becky Smith
Gaviota
Upright
Burbank
Kelsey
Wickson
Combination
Los Gatos
The early Japanese varieties, being usually deficient pollen pro-
ducers, are unreliable for cross-pollination. The late blossoming
varieties are satisfactory pollen producers and may be interplanted
safely. The Japanese varieties may be divided as early or late
blossoming, as follows :
Early
Late
Beauty
Kelsey
Abundance
El Dorado
Combination
Satsuma
Amador
Los Gatos
Formosa
Santa Rosa
Apex
Methley
Gaviota
Wickson
Burbank
Climax
Duarte
Prize
Sultan
Upright
Formosa and Gaviota are apparently inter-barren, or at least
unsafe for planting together. Tragedy is able to pollinate several
Japanese varieties but is not pollinated by them. Table 4, by Allen,"
summarizes the pollination requirements of Japanese plums.
7 Allen, F. W, Plum growing in California. California Ext. Cir. 34:1-65
1929.
14
California Agricultural Extension Service [Cir. 62
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1932]
Pollination of Deciduous Fruits by Bees
15
European plums (including prunes) may be classed as self -barren,
self -fruitful, or doubtful, as follows:
Self -barren
Anita
Burton
Clyman
Diamond
Fellenberg (Italian)
Imperial
Jefferson
President
Robe de Sergeant
Quackenboss
Silver
Standard
Sultan
Tragedy
Washington
Self-fruitful
California Blue
Coates 1418 (Double X)
French
Giant
Sugar
Yellow Egg
Doubtful
Conquest
Grand Duke
Pond (Hungarian)
Stuart
The doubtful list includes varieties which in some years may pro-
duce satisfactory crops with their own pollen but which one should
probably not plant without providing for cross-pollination.
There is apparently no inter-unfruitfulness among- Europeon
plums. In some years, however, certain varieties do not set satisfac-
tory crops. In general, varieties blossoming at the same time will
cross-pollinate effectively. Although this is not a complete list, the
following varieties may be grouped together according to the time
of blossoming:
Early
Clyman
Tragedy
Mid-season
Burton
Coates 1418 (Double X)
Diamond
French
Grand Duke
Imperial
Jefferson
Eobe de Sergeant
Sugar
Standard
Stuart
Late
California Blue
Fellenberg (Italian)
Giant
President
Pond (Hungarian)
Quackenboss
Silver
Washington
Yellow Egg
Table 5, by Allen, ^ summarizes the pollination requirements of
■European plums.
8 Allen, F. W. Plum growing in California. California Ext. Cir. 34 : 1-65.
1929.
16
California Agricultural Extension Service
[Cm. 62
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1932] Pollination of Deciduous Fruits by Bees 17
ARRANGEMENT OF POLLINIZERS
In planting" an orchard where poUinizers are required, one should,
if possible, have every sixth and preferably every fourth row a pollin-
izing" variety. For convenience in harvesting it is best to plant two,
four, or six rows of one kind, then two of the pollinizing variety, and
repeat. In some instances it is desirable to have a minimum number
of pollinizers. Under these circumstances, one tree to eight, planted
as every third tree in every third row, is recommended. This arrange-
ment places a pollinizer next to every tree of the main variety in
the orchard.
Certain conditions may make it advisable to graft a pollinizer
into every tree to insure satisfactory cross-pollination. Such an
arrangement will, of course, tend toward confusion in harvesting ;
when the pollination problem is serious, however, the grower can afford
to forget the commercial value of the fruit on the pollinizing branch.
The suggestion given above is primarily for the orchardist whose
mature trees, because of the planting of self or inter-barren varieties,
have failed to fruit. During the years when one is waiting for the
trees grafted over to pollinizing varieties to come into bearing, some
relief may be obtained by cutting off branches of pollinizing varieties,
placing the cut ends into vessels of water, and distributing them
throughout the orchard during the blossom period. Such branches
will live for several days and continue to bloom, forming pollen for
the bees to transfer to the unfruitful varietv.
THE HONEYBEE AS A POLLEN DISTRIBUTOR
The intimate relationship between bee life and plants is well known
to students of nature. Certain bees require pollen and nectar for
sustaining life; the pollen, in the case of the hive bee, is fed, along
with other substances, to the larval forms; while nectar is converted
to honey primarily for adult food. In many cases, the plants require
the pollen from other varieties of the species for the setting of fruit
and seed. Nectar, a weak sugar solution, attracts many insects ; and
its presence in close proximity to the stamens better assures visitation
by the living pollen carriers. The bee wholly depends for existence
upon the plant products — pollen and nectar ; while, on the other hand,
many plants would fail in productivity^ except for the presence of
insects suitable for effecting cross-pollination.
18
California Agricultural Extension Service
[Cm. 62
POLLEN MANIPULATION BY THE BEE
The structures over the body of the worker bee are admirably
designed for the efficient collection and transportation of pollen. In
the first place, the whole body is densely clothed with hairs (fig. 4),
Fig. 4. — The body of the hive bee is completely covered with hair, in which
the pollen grains become entangled. The bee, before it starts its return flight to
the hive, combs the grains into the pollen basket. See figure 7.
which are barbed in such a way that pollen grains of varying size
(figs. 5 and 6) cling to them. The legs, too, bear pollen-manipulating
devices : each front leg, for example, has a notch of the proper diame-
ter for stripping the antennae clean ; the middle and hind legs have
spines, spoon-shaped depressions (called pollen baskets), hair
combers, etc.
The bee partially cleans its body of pollen grains by means of the
combs and other structures. A large ball of pollen is finally formed
in the pollen basket, on the outside of each rear tibia (fig. 7), from
which it is removed after being carried to the hive. Many pollen
grains remain scattered over the bee's body, even after combing, and
it is believed that it is this pollen which effects cross-pollination.
The labor and time expended in collecting a load of pollen are con-
1932]
Pollination of Deciduous Fruits by Bees
19
Fig. 5. — Photograph of femur from a bee 's leg, showing hairs with pollen
grains from some plant. This field bee was caught entering the hive, as it
returned from a collecting trip. These grains come in contact with the viscid
surface of the stigma as the bee pushes into the blossom for nectar or pollen, and
bring about cross-pollination. Also see figure 6.
Fig. 6. — Diagrammatic sketches showing arrangement of barbs on the hairs
of bees. The pollen grains cling on the hair between these barbs. The irregular
spacing of barbs on the hair shaft is an adaptation suited to picking up pollen
grains of varying size and shape. See also figures 5 and 8.
20
California Agricultural Extension Service [Cm- 62
Fig. 7. — Hind legs of hive bee with large mass of pollen in the pollen basket
upon the outside of the tibia. Note the combs on the first tarsal segment. The
parts of the leg are the coxa (a), the trochanter (b), the femur (c), the tibia
(d), and the five tarsal segments (e).
1932]
Pollination of Deciduous Fruits by Bees
21
S
%^
a b ll^ ^
A
^ # ^^P
W*^
«!
Fig. 8. — Photographs of pollen grains, indicating comparative size and shape:
(a) cherry, (b) almond, (c) hollyhock, (d) olive, and (e) date palm. Magnifica-
tion of all, X 250. Also see figures 5 and 6.
22 California Agricultural Extension Service [CiR- 62
siderable: often a bee spends an hour in workings over the anthers
of the blossoms (fig*. 1) before returning to the hive. The different
kinds of pollen (fig. 8) are stored in the cells of the comb until needed
for feeding the bee larvae. Pollens from different plant species are
of various color (white, yellow^, brow^n, blue, red, etc.), a fact which
facilitates their identification in the comb cells.
SOME COLLECTING HABITS OF BEES OF VALUE IN
FRUIT POLLINATION
Bees, whether collecting pollen or nectar, usually visit on a par-
ticular trip but one species of plant. Where blossoms are scarce,
the bee may be forced to collect from more than one species; but
such is not the case during fruit blossoming. Some species of plants
are definitely preferred to others. The time of day influences
availability of both nectar and pollen, so that activity shifts from one
plant to another : for example, filaree, in the orchards, is very attrac-
tive during the early morning; but most of the blossoms close by 10
o'clock on sunny days. Apparently some of the fruits secrete nectar
most freely during the night ; bees quickly harvest this in the morning
and then shift to some other plant. During certain seasons, for
example, this change from prunes to mustard is particularly noticeable.
Very often pear blossoms are less attractive than others which are
open at the same time. Bees like apple blossoms particularly : they
will sometimes leave pear for cherry and cherry for apple. In certain
areas, at least, bees visit pear blossoms for pollen only, ignoring the
nectar which is plainly visible. Some recent work indicates a vari-
ation in sugar concentration for various nectars, which may explain
the periodic preference shown by bees for certain flowers.
SPRAYING DETRIMENTAL TO BEES
The problem of spray poisoning is often acute for bees near
orchards where arsenic or nicotine is used on the plants. Not only are
the nectar and pollen of trees contaminated, but those of the covercrop
as well. In addition, bees drink up dew from leaves and thus may
secure a fatal dosage of poison, so that one cannot entirely eliminate
this source of loss even by properly timed spraying-. Wherever cover-
crops occur in orchards, the spray poison problem is particularly
serious. Beekeepers and fruit growers must, in short, cooperate if loss
of bees is to be reduced to a minimum; and the beekeeper should
receive timely warning to move out before spraying operations begin.
1932]
Pollination of Deciduous Fruits by Bees
23
SET OF FRUIT NOT DEPENDENT UPON BEES ALONE
The need for more insects to bring about cross-pollination in areas
of fruit concentration is well recognized by scientific workers and
many orchardists. One must emphasize the fact that a supply of pol-
linating insects alone is not sufficient to cause a commercial set of
fruit, but that other factors, such as favorable weather and suitable
varieties properly planted, are also important. The fact that hive
bees are efficient pollen distributors which can be placed where and
when wanted, needs only to be mentioned.
^^^•••••»
Fig. 9. — A bee comb illustrating the large area occupied by brood during fruit
blossoming time; five to ten combs are necessary. Both sealed (a) and unsealed
brood cells (b) as well as honey (upper left) may be seen. During periods of
low temperature, as often occur during fruit blossoming time, all the bees in a
weak colony may be needed in the hive to keep up the temperature for brood;
therefore, it is only in the case of strong colonies that there are bees available
for field work.
BEEKEEPING A SPECIALTY
The fruit-grower is usually too busy with orchard problems to
become an efficient beekeeper. Bees require considerable attention
throughout the year if they are to be strong in numbers at the end of
winter. Only strong colonies will prove of much value during early
spring, when a large number of bees are required in the hive to main-
tain the brood nest temperature at 95° F (fig. 9). Generally, the most
24 California Agricultural Extension Service [C^R- 62
feasible plan for securing pollinating insects is to rent bees from
highly skilled beekeepers. The importance of an early agreement must
be stressed, because many cases of bee shortage are annually reported
too late for correction.
NUMBER OF BEES REQUIRED FOR POLLINATION
The usual recommendations call for one colony of bees to the acre
of fruit to be pollinated. The condition of the weather so affects
results, however, that often more bees would justify their cost, while at
other times even the prescribed number probably exceeds actual re-
quirements. According to one beekeeper at Oroville, a section near
him has 10,000 acres of prunes and 3,000 acres of pears with a bee
population of only 1,000 colonies (1930). This number of bees must
certainly be inadequate for best results, particularly when the general
insect population, because of weather conditions or other cause, is low.
Table 6 shows the acreage of fruits (exclusive of grapes) and the reg-
istered number of colonies of bees in the counties of California. The
colony figures are primarly from the State Department of Agriculture
registration list for 1929.
TABLE 6
List of California Counties with Fruit Acreage and
Number of Bee Colonies
Bearing fruit Colonies of
County acreage* hees
Alameda 7,708 2,944
Alpine 1 2
Amador 970 48
Butte 21,864 8,449
Calaveras 507 224
Colusa 3,687 6,322
Contra Costa 12,417 3,321
Del Norte 4 71
Eldorado 5,374 662
Fresno 43,911 16,875
Glenn 8,497 5,931
Humboldt 1,665 1,531
Imperial ..- 4,930 19,639
Inyo 1,102 3,640
Kern 8,470 11,142
Kings 13,191 5,911
* These figures do not include grapes.
1932] Pollination of Deciduous Fruits by Bees 25
TABLE 6— Continued
Bearing fruit Colonies of
County acreage* bees
Lake 7,141 120
Lassen 185 981
Los Angeles 71,567 38,389
Madera 9,079 2,010
Marin 633 443
Mariposa 263 67
Mendocino 5,295 1,068
Merced 20,485 8,188
Modoc 434 1,114
Mono 74 100
Monterey 8,823 4,546
Napa 14,528 1,217
Nevada 2,349 199
Orange 49,159 15,742
Placer 30,910 311
Plumas 34 47
Eiverside 39,835 22,585
Sacramento 24,399 5,864
San Benito 15,532 404
San Bernardino 74,055 39,830
San Diego 12,379 30,279
San Francisco 67
San Joaquin 21,308 13,573
San Luis Obispo 5,826 3,438
San Mateo 1,843 188
Santa Barbara 3,197 4,846
Santa Clara 102,617 3,275
Santa Cruz 18,775 538
Shasta 2,173 4,510
Sierra 19 118
Siskiyou 364 1,256
Solano 24,062 2,139
Sonoma 42,994 2,157
Stanislaus 31,343 8,200
Sutter 45,329 4,846
Tehama 8,228 4,728
Trinity 26 163
Tulare 76,377 11,446
Tuolumne 2,071 408
Ventura 11,900 14,873
Yolo - 15,078 3,511
Yuba 9,663 1,031
* These figures do not include grapes.
26 California Agricultural Extension Service [<^R- 62
PLACING THE BEES IN THE ORCHARD
Bees are moved into orchards of this state almost entirely by motor
truck or trailer. The actual move is usually made during- the night.
The entrances of the hives are as a rule closed, before moving, with
some screening device or cloth material. During hot weather a
moving-screen, in place of the hive cover, is essential for ventilation.
The recommendation of one hive to the acre does not mean that one
hive should be located on each acre. Under normal conditions it is
seldom that bees are left in orchards in groups under ten colonies.
The manipulation of single colonies is too difficult, particularly after
rains ; also the increased time and labor required for removal of scat-
tered colonies adds to the expense. Sunshine, wind, temperature,
rain, and other factors outside of the hive affect the flight of bees;
therefore, general recommendations cannot be given relative to the
proper placement of the colonies in the orchard. If the weather is fair
and warm, during fruit-blossom time, bees can undoubtedly fly far
enough to cover 100 acres or more of fruit from one location ; on the
other hand, during a cold wet season flight is very limited. The
absence of fruit or nuts, except within a few rows distant from the bee
location, is occasionally reported following a particularly bad spring.
Under average conditions bees in groups of 10 to 20 colonies, for as
many acres surrounding them, have been found very satisfactory both
to the fruit grower and the beekeeper. Accessible situations along
roadways in the orchards should be chosen, because of mud as well as
the difficulty of driving the trucks among the trees at night.
The bee population as is evident in the table is strikingly low, in
comparison with the fruit acreage, for several of the important fruit
counties in northern California, notably Eldorado, Napa, and Nevada.
Some beemen regularly move bees into these fruit areas on a rental
basis. A factor partly responsible for this low resident bee population
is the presence of the detrimental California buckeye tree. The lack
of a major honey plant also greatly reduces the possibility of profit-
able beekeeping. Undoubtedly the intensive insecticidal spraying
operations practiced in many deciduous fruit areas play a part too in
further reducing the number of bees.
To the southward, on the other hand, the number of colonies of
bees increases greatly in proportion to the fruit acreage requiring pol-
lination. In the upper end of the San Joaquin Valley, for example,
at the present time, bees are rarely rented to the fruit grower for pol-
1932] Pollination of Deciduous Fruits by Bees 27
lination purposes. Beemen are, in fact, very desirous of locating near
deciduous fruit orchards to enable their colonies to build up early in
preparation for the orange honey flow during April. Tulare County
alone has some 33,000 acres of citrus fruits.
COST OF RENTING BEES
The rental price paid by the fruit grower for bees in orchards
depends upon several factors : for example, necessary moving distance,
condition of roads, local rainfall, and supply of bees, coupled with
demand. In a given area, like the Santa Clara Valley, rental possi-
bilities change with time: during the World War, for example, with
the accompanying high price of prunes, many bees were moved in
from the vicinity of Modesto at $5.00 to $7.00 per colony for the blos-
soming period. Now but few bees are taken in — mostly for cherry
orchards, at $2.00 to $2.50 rental. The beekeepers, in fact, find it dif-
ficult to surmount the barriers set up by the sentiment of pear growers
concerning blight. The present rental demand for bees in California
comes largely from almond and plum growers, though the cherry,
apple, and foothill pear growers also rent a good many colonies.
The earlier in the fall a fruit grower can place his order for bees,
the greater the chance for satisfactory accommodation, because after
the orchard becomes muddy, moving is difficult. Experience has
taught beekeepers the unprofitableness of renting colonies at current
prices when expensive moving problems arise. The average rental
price at present is perhaps $2.00. The fruit growers should insist
on good, strong colonies, for these are by far the most efficient in
pollination.
AGRICULTURAL EXTENSION SERVICE CIRCULARS
No.
3.
5.
9.
10.
11.
12.
13.
14.
15.
16.
17.
21.
22.
23.
25.
26.
29.
30.
31.
32.
33.
Feedine: Beef Cattle in California.
Lettuce. (Series on California Crops
and Prices.)
Suggestions on Grapefruit Culture in
Imperial Valley.
Rabbit Raising.
The Home Preparation of Fruit Candy.
Cauliflower Production.
"Wool Production in California.
The Manufacture of Monterey Cheese.
Selection and Care of Electrical Equip-
ment Used in Dairy Manufacturing.
Pork Production in California.
Irrigation of Orchards by Contour Fur-
rows.
Liver Fluke and Stomach Worm of
Sheep.
Bovine Tuberculosis.
Thinning Sugar Beets.
Strawberry Culture in California.
Bush Fruit Culture in California.
The Home Vegetable Garden.
Control of Pocket Gophers and Moles in
California.
Elements of Grape Growing in Cali-
fornia.
Pow^dery Mildew of the Grape and Its
Control in California.
What to do About Bovine Tuberculosis.
Rearing Dairy Heifers Free from Tuber-
culosis and Abortion Disease.
No.
34. Plum Growing in California,
35. Alfalfa Production.
36. Beekeeping for the Beginner in Cali-
fornia.
37. Home and Farm Preparation of Pickles.
3». Alfalfa Varieties and Seed SuRply.
40. Frost Protection in California Orchards.
41. Prune Culture in California.
42. Peach Culture in California.
43. The California Avocado Industry.
44. Bang's Disease (Infectious Abortion).
45. Zinc Chloride Treatment for Pear Blight
Cankers.
46. Clierrv Culture in California.
47. Equipment for the Bulk Handling of
Grain.
48. The Manufacture of Cottage Cheese.
49. Sheep Production in California.
51. Apricot Growing in California.
53. Home Floriculture in California.
54. The Control of Weeds.
55. Growing and Handling Sweet Potatoes
in California.
56. Girdling Grape Vines.
57. Commercial Fertilizers and Soil Fertility
in California.
58. Turkey Raising in California.
59. The 1932 Agricultural Outlook for Cali-
fornia.
STATION PUBLICATIONS AVAILABLE FOE FREE DISTKIBUTION
BULLETINS
No. No.
253. Irrigation and Soil Conditions in the 433.
Sierra Nevada Foothills, California.
263. Size Grades for Ripe Olives.
279. Irrigation of Rice in California. 435.
283. The Olive Insects of California.
310. Plum Pollination.
331. Phylloxera-Resistant Stocks. 439.
343. Cheese Pests and Their Control.
348. Pruning Young Olive Trees.
349. A Study of Sidedraft and Tractor
Hitches.
357. A Self-Mixing Dusting Machine for 440.
Applying Dry Insecticides and Fun-
gicides.
361. Preliminary Yield Tables for Second- 445.
Growth Redwood.
364. Fungicidal Dusts for the Control of 446.
Bunt. 447.
369. Comparison of Woods for Butter Boxes.
370. Factors Influencing the Development 448.
of Internal Browning of the Yellow
Newtown Apple. 449.
3 71. The Relative Cost of Yarding Small
and Large Timber. 450.
373. Pear Pollination.
374. A Survey of Orchard Practices in the
Citrus Industry of Southern Call- 452.
fornia. 454.
379. Walnut Culture in California.
386. Pruning Bearing Deciduous Fruit 455.
Trees.
389. Berseem or Egyptian Clover. 456.
392. Fruit Juice Concentrates.
393. Cron Sequences at Davis. 458.
394. I. Cereal Hay Production in California.
II. Feeding Trials with Cereal Hays. 459.
395. Bark Diseases of Citrus Trees in Cali-
fornia. 462.
396. The Mat Bean. Phaseolus Aconitifolius. 464.
404. The Dehydration of Prunes.
406. Stationary Snray Plants in California. 465.
407. Yield. Stand, and Volume Tables for 466.
White Fir in the California Pine
Region. 467.
408. Alternaria Rot of Lemons. 468.
409. The Digestibility of Certain Fruit By-
products as Determined for Rumi- 469.
nants. Part I. Dried Orange Pulp 470.
and Raisin Pulp.
410. Factors Influencing the Quality of Fresh 471.
Asparagus After It is Harvested.
416. Culture of the Oriental Persimmon in 472.
California. 473.
417. Poultry Feeding: Principles and Prac-
tice^ 474.
418. A Study of Various Rations for Fin-
ishing Range Calves as Baby Beeves.
419. Economic Aspects of the Cantaloupe 475.
Industry. 476.
420. Rice and Rice By-Products as Feeds 477.
for Fattening Swine.
421. Beef Cattle Feeding Trials, 1921-24. 479.
423. Apricots (Series on California Crops
and Prices).
425. Apple Growing in California. 480.
426. Apple Pollination Studies in California.
427. The Value of Orange Pulp for Milk 481.
Production.
428. The Relation of Maturity of California 482.
Plums to Shipping and Dessert 483.
Quality. 484.
431. Raisin By-Products and Bean Screen-
ings as Feeds for Fattening Lambs. 485.
432. Some Economic Problems Involved in 487.
the Pooling of Fruit.
Power Requirements of Electrically
Driven Dairy Manufacturing Equip-
ment.
The Problem of Securing Closer Rela-
tionship between Agricultural Devel-
opment and Irrigation Construction.
The Digestibility of Certain Fruit By-
Products as Determined for Rumi-
nants. Part II, Dried Pineapple
Pulp, Dried Lemon Pulp, and Dried
Olive Pulp.
The Feeding Value of Raisins and
Dairy By-Products for Growing and
Fattening Swine.
Economic Aspects of the Apple In-
dustry.
The Asparagus Industry in California.
A Method of Determining the Clean
Weights of Individual Fleeces of Wool.
Farmers' Purchase Agreement for Deep
Well Pvimps.
Economic Aspects of the Watermelon
Industry.
Irrigation Investigations with Field
Crops at Davis, and at Delhi, Cali-
fornia, 1909-1925.
Economic Aspects of the Pear Industry.
Rice Experiments in Sacramento Val-
ley, 1922-1927.
Reclamation of the Fresno Type of
Black-Alkali Soil.
Yield. Stand and Volume Tables for
Red Fir in California.
Factors Influencing Percentage Calf
Crop in Range Herds.
Economic Aspects of the Fresh Plum
Industry.
Prune Supply and Price Situation.
Drainage in the Sacramento Valley
Rice Fields.
Curly Top Symptoms of the Sugar Beet.
The Continuous Can Washer for Dairy
Plants.
Oat Varieties in California.
Sterilization of Dairy Utensils with
Humidified Hot Air.
The Solar Heater.
Maturity Standards for Harvesting
Bartlett Pears for Eastern Shipment.
The Use of Sulfur Dioxide in Shipping
Grapes.
Adobe Construction.
Economic Aspects of the Sheep In-
dustry.
Factors Affecting the Cost of Tractor
Logging in the California Pine
Region.
Walnut Supply and Price Situation.
Poultry Houses and Equipment.
Improved Methods of Harvesting Grain
Sorghum.
I. Irrigation Experiments with Peaches
in California. II. Canning Quality
of Irrigated Peaches.
The Use, Value, and Cost of Credit in
Agriculture.
Utilization of Wild Oat Hay for Fat-
tening Yearling Steers.
Substitutes for Wooden Breakpins.
Utilization of Surplus Prunes.
The Effects of Desiccating Winds on
Citrus Trees.
Drying Cut Fruits.
Asparagus (Series on California Crops
and Prices).
BULLETINS— (Corjfinwerf)
No.
488.
489.
490.
491.
492.
493.
494.
495.
496.
497.
498.
499.
500.
501.
502.
503.
504.
Cherries (Series on California Crops
and Prices).
Irrigation Water Requirement Studies
of Citrus and Avocado Trees in San
Diego County, California, 1926 and
1927.
Olive Thinning^ and Other Means of
Increasing Size of Olives.
Yield. Stand, and Volume Tables for
Douglas Fir in California.
Berry Thinning of Grapes.
Fruit Markets in Eastern Asia.
Infectious Bronchitis in Fow^ls.
Milk Cooling on California Dairy
Farms.
Precooling of Fresh Fruits and Tem-
peratures of Refrigerator Cars and
Warehouse Rooms.
A Study of the Shipment of Frei^h
Fruits and Vegetables to the Far East.
Pickling Green Olives.
Air Cleaners for Motor Vehicles.
Dehydration of Grapes.
Marketing California Apples.
Wheat (Series on California Crops
and Prices).
St. Johnswort on Range Lands of
California.
Economic Problems of California Agri-
culture. (A Report to the Governor
of California.)
No.
505. The Snowy Tree Cricket and Other
Insects Injurious to Raspberries.
506. Fruit Spoilage Disease of Figs.
507. Cantaloupe Powdery Mildew in the
Imperial Valley.
508. The Swelling of Canned Prunes.
509. The Biological Control of Mealybugs
Attacking Citrus.
510. Olives (Series on California Crops
and Prices).
511. Diseases of Grain and Their Control.
512. Barley (Series on California Crops
and Prices).
513. An Economic Survey of the Los
Angeles Milk Market.
514. Dairy Products (Series on California
Crops and Prices).
515^ The European Brown Snail in Cali-
fornia.
516. Operations of the Poultry Producers
of Southern California, Inc.
517. Nectar and Pollen Plants of California.
518. The Garden Centipede.
519. Pruning and Thinning Experiments
with Grapes.
520. A Survey of Infectious Laryngotrache-
itis of Fowls.
521. Alfalfa (Series on California Crops
and Prices).
CIRCULARS
No.
115. Grafting Vinifera Vineyards.
178. The Packing of Apples in California.
212. Salvaging Rain-Damaged Prunes.
230. Testing Milk. Cream, and Skim Milk
for Butterfat.
232. Harvesting and Handling California
Cherries for Eastern Shipment.
239. Harvesting and Handling Apricots and
Plums for Eastern Shipment.
240. Harvesting and Handling California
Pears for Eastern Shipment.
241. Harvesting and Handling California
Peaches for Eastern Shipment.
244. Central Wire Bracing for Fruit Trees.
245. Vine Pruning Systems.
248. Some Common Errors in Vine Pruning
and Their Remedies.
249. Replacing Missing Vines.
253. Vineyard Plans.
257. The Small-Seeded Horse Bean (Vicia
faba var. minor).
258. Thinning Deciduous Fruits.
259. Pear By-Products.
261. Sewing Grain Sacks.
262. Cabbage Production in California.
265. Plant Disease and Pest Control.
269. An Orchard Brush Burner.
270. A Farm Septic Tank.
No.
279. The Preparation and Refining of Olive
Oil in Southern Europe.
282, Prevention of Insect Attack on Stored
Grain.
288. Phylloxera Resistant Vineyards.
290. The Tangier Pea.
292. Alkali Soils.
294. Propagation of Deciduous Fruits.
296, Control of the California Ground
Squirrel.
301. Buckeye Poisoning of the Honey Bee.
304. Drainage on the Farm.
305. Liming the Soil.
307. American Foulbrood and Its Control.
308. Cantaloupe Production in California.
310. The Operation ef the Bacteriological
Laboratory for Dairy Plants.
316. Electrical Statistics for California
Farms.
317. Fertilizer Problems and Analysis of
Soils in California.
318. Termites and Termite Damage.
319. Pasteurizing Milk for Calf Feeding.
320. Preservation of gruits and Vegetables
by Freezing Storage.
321. Treatment of Lime-induced Chlorosis
with Iron Salts.
322. An Infectious Brain Disease of Horses
and Mules (Encephalomyelitis).
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