Do we need pollinators?
Yes. The separation in time of the male and female phases of a single flower and the nature of avocado pollen has led most observers to believe that a pollen vector or ‘pollinator’ is needed to move pollen from one flower to another.
While there is some speculation on the capacity of a range of small insects (including the hover fly) to act as pollinators, the European honey bee (Figure 8) is by far the most recognised and commonly used pollinator in Western Australia. The honey bee is also the only insect that is commercially farmed and sold for pollination services in Western Australia.
The avocado flower provides both pollen and nectar which will attract the bees, but due to its size, unusual opening sequence and lower sugar concentration in its nectar, it is not preferred by honey bees. In fact the ancestral pollinators of avocados were small stingless wasps and flies. Therefore, while resident populations of feral bees will visit your avocado trees and do pollination work, they will often be attracted more to other plants flowering at the same time, thus limiting their effectiveness.
Bees are known to scout an area and learn where preferred plants are and target these. New bees to an area will not have this knowledge and will target the closest flowers initially, gradually building their knowledge. To maximise pollination of your avocados, it is preferable to bring in fresh hives at the start of flowering (ideally once roughly 10% of flowers have opened). Do not bring in hives too early as the bees will find other flowers to visit (eg. Capeweed, Wild Radish, other wildflowers), and even when the avocado trees begin to flower in earnest, the bees will remain preferential to the first flowers they found when they were moved into the area.
The introduction of bee hives into an orchard for pollination requires some planning. It is preferable to bring in healthy and active hives that are going to be collecting both pollen and nectar. This is usually done through the services of a professional pollination provider, who will condition hives and transport them to your orchard at an agreed time.
As conditioning hives takes time, and flowering can go from 10 to 80% opened in less than a week, you need to plan in advance with your pollination provider.
The placement of the bee hives within the orchard also needs to be considered. They are best placed in small groupings relatively evenly scattered within the blocks flowering, at a rate of two to five hives per hectare. Do not place the hives on the outside of the blocks as the scout bees might find alternative flowers faster and ignore your avocado trees.
Bees are also living insects, so absolute care needs to be taken about the choice and use of any chemical that may be applied to the orchard during flowering. If required, always choose the chemical with the lowest bee toxicity and apply in the evening when bees are less active.
If a bee-toxic chemical is required, you should liaise with the pollination provider about removing the bees for a few days. Thankfully, avocado production in Western Australia requires minimal pesticide use, so it is unlikely to be a common issue.