Australia: Greater insect diversity may raise avocado yields

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Australia: Greater insect diversity may raise avocado yields

Australian researchers are investigating whether traditional pollination techniques are the 'bee all and end all' when it comes to avocado yields, with results so far showing insect diversity favors the in-demand crop.

A native Australian drone fly. Photo: John Tann, via Wikimedia Commons

A native Australian drone fly. Photo: John Tann, via Wikimedia Commons

With funding from Horticulture Innovation Australia (HIA), Plant & Food Research Australia is carrying out the research with the help of growers around the border areas between South Australia, Victoria and New South Wales.

Lead researcher Brad Howlett said most people assumed honey bees were the best pollinators, but with avocados this may not be the case.

"Some of the orchards with the best yields have very few honey bees, but an amazing diversity of flies, and a close study of their ability to transfer pollen shows many are as effective as bees," Howlett said.

"Avocados are tricky because the flowers not only open as male one day and female the next, but are usually only open a few hours a day – or even open at night if it's cold.

"That can be problematic if you're relying on bees, because they aren't active at night, and don't like cold or rain."

He said the benefit of encouraging populations of various insects during flowering was that each one had a different behavior, so there was a greater chance to them being active at the right times.

The HIA said growers already knew yields could be up to 10 times better if flowers were adequately pollinated, and that planting pollenizer trees amongst the main varieties like Hass could improve cross-pollination by providing a source of pollen.

During the next flowering season researchers hope to investigate how the pollen flows between the varieties, as well as continuing more detailed field surveys into the different species of insects in the crops.

Howlett said the findings could mean the avocado growers lucky enough to have an abundances of fly pollinators were probably somewhat protected from the impact of the Varroa mite, a bee pest that has devastated global honey bee populations and the crops that rely on pollination.

"If flies can do the job just as well and we find them to be widespread, avocados may be one of the few crops that isn't as adversely affected if Varroa enters Australia and wipes out most of the feral honey bees that many growers rely on as their main source of pollination."

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