The Buzz: Macadamia and cross pollination – does it really increase production?

Reading Time: 4 minutes

Most growers are aware of a large body of work done on the importance of cross pollination for high yields in macadamia, but are unsure on whether it really improves production.

How is cross pollination achieved? Cross pollination requires pollen to be moved between different varieties which may be many metres apart.  Insects are the most effective pollinators because they easily move directly between flowers from different trees even over a distance.

Honey bees are the easiest insect pollinators to manage in South Africa, and because they remain loyal to flowers they work on it makes them excellent pollinators. This means that the bee that forages on macadamia flowers will exclusively forage on them carrying only macadamia pollen, and not a mixture of vegetation pollens.

Although pollen gathering honey bees are more likely to contact the stigma directly and fertilise the flower, both pollen and nectar foragers will pollinate macadamia flowers to improve the nut set. Careful management of hives will ensure the optimal pollination of macadamia.

Hives should be pollen hungry with lots of young brood that requires protein rich pollen for development. A laying queen and enough brood and is therefore essential.

Mike Allsopp of the ARC found in his research project conducted in 2019 that the cross pollination of all the cultivars he tested in the Barberton area (Baumont, A4, A16, 816 and 814) had produced significantly more nuts than those that were not cross pollinated. As a matter of fact, he claims a staggering 600% increase in nut set with cross pollination.

Another interesting fact he pointed out was that honey bees actively collected both nectar and pollen from early bloom, and right until the blooming period ceased with as many as 80% of the colony still working on macadamia towards the end of the season. This means that colonies could actively and effectively pollinate macadamia crops for a long period of time reducing the need to rotate colonies as is needed on some other agricultural crops. This of course makes the pollination cost per hectare significantly cheaper for macadamia farmers than for instance those farming soft fruits and berries.

It is therefore clear: Honey Bees are essential to good macadamia harvests and planting appropriate pollinisers into the orchard to ensure cross pollination is essential to maximise production.

Maximising pollination: Placement of hives should be carefully considered

Here follows are few pointers to take into consideration:

  • Colonies should be spread evenly throughout the orchard in groups of 2-4 hives, to ensure bees visit flowers across the entire orchard.
  • Best placement is slightly above the orchard or at ends of rows will ensure the best coverage.
  • Bees prefer to work down rows so therefore alternating rows of different cultivars that flower at similar times will greatly assist in cross pollination. Alternatively, pollinisers can be planted at intervals down the rows – starting with a polliniser at the ends of the rows.
  • Bees also prefer to forage on racemes that are in the sunlight, so careful pruning of trees to open the canopy can increase the number of flowers they visit.
  • The flowers can only be pollinated when they are fully open, so introduce bees only once there are enough open flowers to feed them to prevent the colony from stopping brood rearing due to lack of food. This can seriously affect their productivity and accordingly your nutset.
  • Studies have shown that approximately 50 bee visits were made per day to each raceme and as individual flowers remain attractive to insects for three days, approximately 150 visits per raceme are required to ensure optimal pollination.
  • Placing hives at least 20 meters away from the orchards are essential to limit spray drift.
  • Placing on stands to protect against Honey Badgers and ants will protect your pollinators.
  • Contrary to popular perception, availability of alternative pollen sources for good colony strength will assist bee health; this could include flowering boundary plants such as African Blue Basil.
  • To maximise pollination and protect bees from drinking pesticide-contaminated water, beekeepers and growers should ensure clean water is always available.
  • Placing hives in dappled shade protects against extreme heat.

Did you know: Bees need both water and shade for optimal health and productivity

If shade isn’t available, it is advised that shade be provided

Why is water and shade important?

Bees need to keep their hive temperature at around 35-36 °C. The Lowveld is hot. So how do they reduce internal hive temperature?

They have to fetch water and place droplets all over the frames inside the hive. Young hive bees then have to fan the droplets to cool the air inside the hive down. If they can’t manage, field bees will help, as constant brood temperature is crucial to prevent the new generation from overheating and dying.

To ensure maximum numbers of bees are working as pollinators, hive temperature should be kept as even as possible. We should think of ways how we can help them to achieve this.

It is after all what they are in your orchards for!

Ensure that you have a Pollination Contract with your beekeeper. Why?

Pollination service contracts are essential to ensure that both growers and beekeepers understand and agree to their roles and responsibilities in at least the following areas:

  • Pesticide applications and schedule
  • Number of frames/health of hives
  • Date and location for hive placement
  • Hive stands to keep colonies safe from ants
  • Accessibility of colonies to beekeepers
  • Safety of the colonies from vandalism
  • Date of hive removal from the orchard

What should be in the contract is laid out in the Pollination Charter that was developed by CropLife. Click Here

Also take note: Beekeepers and farmers responsibility according to the law

The Agricultural Pest Act 36 of 1983 and Control Measures Relating to Honey bees No. R1511 states that:

  • Everyone that owns even one bee hive is required by law to register with Department Agriculture, Land Reform and Rural Development (DALRRD)
  • All hives have to be marked with the registration number of the hive owner received from DALRRD
  • Only registered beekeepers should be allowed by farmers to provide a pollination service.

Please note: Theft and vandalism of bee hives is a growing problem, and it is bound to get worse as bees decline and pollination needs rise. Help to eliminate this by ensuring your pollination service provider is registered, that the hives provided belong to him/her, and that they are clearly marked with his/her registration number. Should this not be the case, please ask for an agreement between the beekeeper and the owner of the hives that prove that the hives are placed with the full knowledge of the owner.

Beekeepers and macadamia farmers should have a mutually beneficial relationship, and the health of the beekeeping sector is of utmost importance for sustained crop production by farmers. It is time to start working together towards sustaining colonies for the future. Watch out for our next edition that explores this in more detail.