A number of misconceptions exist regarding Honey bee pollination of crops. Successful pollination is the culmination of good crop husbandry and management and a little bit of luck as well.  A fuller explanation of these matters is provided below:

For many crops good pollination is required to produce fruit of good size with good mineral uptake into the fruit.   For example, in apples there is a good correlation between viable seed numbers and fruit calcium uptake, fruit shape and size.

Role of the bee
The role of the honey bee in pollination is specifically to transfer pollen from one flower to another and, where cross pollination is required, from one variety of a fruit to another variety of the same fruit.  For example, a Fuji apple may be cross pollinated by Royal Gala or visa versa;  neither of these varieties may be satisfactorily pollinated by its own pollen.

Effective hives
Hives need to contain sufficient bees to become an effective pollination unit; approximately 1.5 boxes of bees or more with six frames covered in brood.   This amounts to approximately 35,000 bees as a minimum.  

Like any insect population in early spring, the hive begins to build with bee numbers well under what is likely to be achieved in the height of summer.  Consequently, not all hives are suitable as pollination units in early spring and beekeepers need to manage bee hives to reach minimum accepted bee populations.   It is not unusual to find 30 to 40 percent of apiary hives under strength and unsuitable as effective pollinator units at this time of year.

Two weak hives placed in the orchard will not give the equivalent of one good pollination unit, due to the lack of foraging bees within the hive.   A hive containing 35,000 bees will have a field force of 10,000 to 15,000 bees that will be foraging for pollen and/or nectar.

Cross pollination critical
Bee pollination activity is not quite as simple as many believe.   There is ample evidence that bees tend to work flowers from one variety of a fruit for the day and will only swap to another variety when there is no more pollen or nectar available from the original variety.

The pollination effect and orchard layout is also an important factor for cross pollination.   Research undertaken by the South Australian Department of Agriculture on almond crops showed that in spite of bees being present, no DNA material from the pollinator variety was evident only three trees away from the sample trees.   We see the same effect on fruit set of crops of Black Doris plums and large blocks of isolated apple trees in Hawke’s Bay, where fruit set can be much less than three trees or rows away from the cross pollinator trees or rows.

Other factors
To effect good pollination, a number of factors are important, not just the beehive.

• Guaranteed hives
Obtain pollination hives from beekeepers that can guarantee minimum hive strength.   Pollination hives sourced from beekeepers using independent auditors to check beehive strength should give you confidence that hives meet minimum acceptable pollination standards.

• Timing
Hives should generally be placed into the orchard when 10 to 15 percent of flowers are open, to reduce the possibility of bees moving onto other non target crops for as long as possible.  Some crops are more attractive than others to honey bees.   For example, bees will readily forage willow and raspberries but will less readily forage kiwifruit.  

• Positioning
Hives should be placed in a warm sheltered area that receives early morning sun.   Hives are best placed in groups of several hives rather than scattered singularly throughout the orchard, as this increases foraging competition.   This may greatly improve the pollen mix coming into the hive and also spread pollination within the flowering canopy of the orchard.

• Hives per hectare
It is generally considered that to effect adequate cross pollination, 10 to 15 bees should be observed on flowers or flying into or out of the flowers, over a 30 second period.   Observations should be made randomly throughout the block, not just in one area, and during a warm period of the day.  (Usually 10am to 3pm in spring.)

• Bee foraging pheromones
Bee foraging pheromones such as Bee-Scent® can be used to help with bee foraging within the orchard.  It is still important to have sufficient cross pollination material in the orchard to achieve a satisfactory level of cross pollination for fertilisation of fruit ovules to occur.

• Temperature
Temperature over flowering is also very important.   Prolonged cool conditions not only reduce bee foraging activity, it also slows down the growth of the pollen tube.   In these conditions many of the pollen tubes may die prior to fertilisation occurring.

• Nutrient status
The nutrient status of the tree over flowering is also important.   Trees that have low boron and/or nitrogen levels may produce flowers with a shorter ovule life compared to flowers with sufficient levels.

• Use of chemicals
A number of fungicides and bactericides may kill pollen.   If weather conditions allow, it is better to avoid applying these pesticides over the peak flowering period, or to choose fungicides that are known to have little or no effect on pollen viability.

For more information about the important factors to understand and consider, speak to your Skeltons Technical Advisor.

Contact a Skeltons technical advisor