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Pollination
The following
is an excerpt from Agriculture Canada Publication 1899/E,
Producing apples in Eastern and Central Canada. For a full
copy of this report, check the Atlantic Food & Horticulture
Research Center web site.
Pollination is
the transfer of pollen from stamens of one flower to the
pistil of another compatible flower, which initiates seed
formation. There is a positive relation between seed number
and successful competition for available nutrients, resulting
in larger fruit size and an increased probability that the
fruit will remain on the tree until harvest. Seeds are also
associated with increased calcium transport into the fruit,
which is in turn associated with greater firmness, delayed
senescence and a reduced incidence of storage disorders.
Apple trees are
essentially self-infertile, so it is necessary to provide
pollinizers. For a cultivar to be considered a good pollinizer,
it must produce compatible pollen of high germinability
in sufficient quantities and at the appropriate time.
The pollinizer
must bloom at the same time as the main crop cultivar. It
is common practice to plant early blooming cultivars with
others that bloom in early or mid-season, and to plant late
blooming cultivars with those that bloom in mid- or late-season.
The date of full flower, when the greatest proportion of
flowers are ready for crossing, is more important than the
date of first flower in determining overlap.
Wind is not an
effective pollination agent. The presence of bees is needed
to disseminate compatible pollen for satisfactory fruit
set. Wild bee species are seldom present in stable or high
enough numbers to be reliable. This unreliability is unfortunate
because some species, such as bumble bees, are very efficient
pollinators, as they are active under windy or cloudy conditions
and forage indiscriminately over the orchard. In contrast,
honey bees require slightly warmer and calmer conditions.
They also prefer to work flowers of the same species at
one time. Honey bees also generally move to the closest
suitable flowers and will therefore remain within rows rather
than moving from row to row. The use of honey bees is presently
the most practical method of increasing the pollination
force when it is needed.
The following
steps can be taken to improve activity:
Shelter orchards from wind
Plant pollinizers at sufficiently close intervals
within crop rows or grafted into crop trees
Control weeds before introducing bees, as some weeds,
such as dandelions, are more attractive to them than are
apple blossoms
To ensure pollination of the king blossom, the earliest
in a cluster, bring bees into the orchard when the first
blooms are open and leave them until petal fall
Put in place a sufficiently high population of bees,
as a higher concentration of bees encourages each bee to
travel farther between forages
Use at least two to three colonies per hectare in
standard orchards, and five colonies per hectare in high
density plantings or in orchards where fruit set has been
inadequate
Place colonies in groups of five to fifteen at about
120m intervals in areas sheltered from the wind, but if
the bloom is light, distribute them throughout the orchard
So the hives catch the morning sun, place them with
their entrances facing east or south
Avoid using any pesticide sprays during the bloom
period because these can adversely affect bee and pollen
viability
Provide a source of clean water, as casual water
sources within the orchard may be contaminated
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