Groundbreaking buzz: the surprising truth about flies

A study commissioned by Hort Innovation and its partners has shown that – rather than bees as might be expected – it’s blow flies that are the chief pollinators of avocados in one of the crop's Aussie growing regions.

Led by Plant & Food Research New Zealand scientist Dr Brad Howlett, the research project focused on the Sunraysia area. It also showed beetles are commonly the secondary pollinators of avocados, despite bee hives regularly featuring in the region's orchards.

Hort Innovation Executive John Lloyd said the research, conducted with input from growers, is groundbreaking.

“Blow flies, along with other fly species and beetles, appear to be very important to the sustainability of avocado fruit production in Sunraysia,” he said.

“These findings give local avocado growers a clear indication of where they should be investing their pollination efforts to get the best possible yields.”

Scientists observed flower-visiting insects throughout the day across 27 orchards near Mildura (11 orchards), Robinvale (six orchards), Renmark (five orchards) and Waikerie (five orchards).

Flies, on average, were the most abundant insects observed across orchards at all four locations, followed by beetles. Waikerie orchards recorded the highest number of honey bees on average but these still represented just 17 per cent of all flower-visiting insects.

Dr Howlett said at least three blow fly species were found capable of transferring similar quantities of pollen, or more, onto flower stigmas than honey bees.

“Across all orchards almost three times as many more blow flies were observed than honey bees,” he said.

“Hover flies were also very common visitors of avocado flowers. Many hover flies actually mimic bees or wasps in their appearance and movements. This can confuse growers into thinking that they have plenty of bees visiting their orchards when in fact they are flies.”

The study demonstrated that hover flies were effective at depositing pollen onto stigmas and outnumbering honey bees by almost three to one.

The research project was funded by Horticulture Innovation Australia with co-investment from Plant & Food Research NZ and the Australian Macadamia Society. Support was also given by Avocados Australia.