Evidence of various species of flies feeding on avocado flowers in orchards in Australia
In an Australian study to establish key pollinating species and their efficacy in increasing yields in avocado orchards, flies have come out as good a pollination insect as bees.
Titled, “The Role of Flies as Pollinators of Horticultural Crops: An Australian Case Study with Worldwide Relevance”, scientists from the country’s government departments and various universities found clear evidence in existing literature of effective pollination by flies in a variety of horticultural crops.
The study was headed by Dr David Cook, a research entomologist and adjunct associate professor at the University of Western Australia: Faculty of Science, School of Agriculture and Environment.
Owing to various stresses on honeybee populations worldwide, along with increasing evidence of wild pollinator decline and concerns about inadequate pollination, the study asserts that modern crop production will become increasingly dependent on managed pollinators to improve yields.
“Currently the success of horticultural crops around the world relies mainly on bees as pollinators. In Australia the honeybee, Apis mellifera Linnaeus 1758 (Hymenoptera: Apidae) – an introduced species – is the single most important pollinator in the agricultural sector.
“Given the risks associated with reliance upon a single species, (we believed) it would be prudent to identify other taxa – or species groups – that could be managed to provide crop pollination services,” the scientists say.
While there seems little research into the role of flies as pollinators in macadamia orchards, it seems probable the insect would operate similarly in a planting of flowering macadamia trees as it does in an avocado orchard.
In the study, flies are described as the most diverse groups (of insects) in the world, present in nearly all habitats and biomes, but they have been studied “far less” than bees.
“Flies can be as efficient as, or better than, bees for pollinating some crops, and are often responsible for transporting high pollen loads in both natural and modified systems,” the study says.
Flies from 86 families of Diptera are reported in the study as visiting the flowers of more than 1 100 different species of plants, with numerous fly families known to visit horticultural crops, including Calliphoridae (blow flies), Syrphidae (hover flies), Sarcophagidae (flesh flies), Muscidae (house fly and relatives), Rhiniidae (nose flies), Bibionidae (march flies) Anthomyiidae (flower flies), Bombyliidae (bee flies), Stratiomyidae (soldier
flies), Tachinidae (bristle flies) and Tabanidae (horse flies).
Flies that act as effective pollinators include blow flies (Calliphoridae), hover flies (Syrphidae), flower flies (Anthomyiidae) and, specifically, the house fly, Musca domestica Linnaeus 1758 (Muscidae).
“Our understanding of the role of flies in pollination remains limited, as Diptera are often overlooked in pollination studies and, consequently, their pollination abilities and relevant biological attributes have yet to be exploited,” the scientists say.
The crops targeted for the research included avocado, mango and lychee trees representing “open orchards”, and berries and vegetable seed crops representing both open and protected greenhouse and glasshouse cropping systems.
And the Diptera identified as possible pollinators were assessed against traits which included mouthpart-characteristics, body mass, body length and the amount and location of pilosity (hairiness) on pollen-contacting body parts. Aspects such as food foraging and reproductive behaviour as well as geographical distribution of the species in line with where crops are grown and exist were considered in the study.
Dr David Cook, a research entomologist and adjunct associate professor at the University of Western Australia: Faculty of Science, School of Agriculture and Environment
Interestingly, the study describes the blow fly as a “main crop pollinating insect” alongside both domestic and wild bees. Similarly, the nose fly is considered an important pollinator of horticultural crops in Australia.
Outside Australia, the study says, four companies based in Spain, the Netherlands, Chile and the United States, respectively, produce flies for commercial pollination services, mainly for seed crops such as brassicas, vegetables and fruits.
In Australia, the only known provider of flies as pollinators is Sheldon’s Bait, (www.sheldonsbait.com.au) which advertises that it “can provide ready-to-hatch blow fly pupae for your pollination needs”.
In a paper titled, “A new perspective on insects that are pollinating avocados”, Brad Howlett and David Pattemore from Plant and Food Research Australia conclude that both flies and beetles are pollinators of avocados and “abundant pollination can occur in orchards with abundant diverse flies even when honeybees are scarce”.
And as the study contends, many of the species identified in the Australian context have global distribution and will most likely prove suitable candidates in other localities and regions. “The outlined guide to candidate identification, and the species identified in (the) Australian case review should drive research efforts to further advance our understanding of fly-pollination abilities and the development of optimal application processes for the implementation of such taxa as pollination agents globally,” the study concludes.
