A wide range of insects visit mango flowers, but new research has identified which of those are the most effective pollinators.

The project, Securing Pollination for more Productive Agriculture: Guidelines for effective pollinator management and stakeholder adoption, has wrapped up after four years of research running from June 2016 to February 2021.

It saw Australia’s most knowledgeable bee and pollination researchers collaborate to assess the contribution of pollinators to a range of pollination-dependent crops including mango.

The project’s recommendations are aimed at strengthening pollination security and resilience, and optimising yield by identifying the insects that contribute to crop pollination and the way they relate to the landscape.

What’s visiting your crop

The project saw researchers Dr Bryony Willcox and Dr Romina Rader observe and collect insect visitors to mango flowers at key locations in Queensland including nine sites at Mareeba and two sites at Bundaberg.

The mango orchards were visited by 76 insect species including bees, flies, beetles, moths and butterflies.

In Mareeba, flies were the major group of visitors to mango flowers, accounting for a combined total of 62% of visits.

Stingless bees (Tetragonula spp.) were the second-most frequent visitors to mango flowers, accounting for 18% of visits.

Honey bees provided 12% of visits, and other bees including the exotic bee Apis cerana and native solitary bees contributed an additional 3% of visits.

The remaining 5% of visits were derived from beetles (2%), ants (1%), butterflies and moths (1%).

In Bundaberg, the main floral visitor to mango was the rhiniid fly Stomorhina discolor, accounting for 46% of visits.

Honey bees were also frequent visitors, contributing 22% of visits, while stingless bees (Tetragonula spp.), soldier beetles (Cantharidae), hoverflies (Syrphidae) and blow-flies (Calliphoridae) contributed 5% of visits each.

Insect pollinators in multiple crops

Dr Rader said in mango, stingless bees and Stomorhina sp. flies were the most effective at transferring pollen. 

“We also identified species that use multiple crops. When comparing the insect visitors of macadamia, avocado and mango crops at Bundaberg, we found that there was a large overlap in visitors, in particular of locally abundant species groups, such as beetles (Coccinellidae) and stingless bees (Tetragonula spp.),” Dr Rader said.

“The identification of pollinators that provide services across multiple crops can be used to develop pollination management strategies that focus on the resource needs of these wild species.”

Why flowering plants matter

Regardless of the range of crops or regions studied in the project, researchers found what they all have in common is a dependency on the presence of native vegetation and flowering plants in the landscape.

“We found that the proximity and composition of native vegetation influences the abundance and diversity of crop pollinating species,” Dr Rader said.

“In less forested areas, wild pollinator densities are not high enough to provide all the pollination required because, in addition to nectar and pollen, wild pollinator presence depends on the availability of other dietary needs, nesting hollows and water.”

Dr Rader said to enhance the health and diversity of pollinators and ensure that pollination services remain reliable and resilient, floral support in close proximity to the crop should be available nearly year-round.

“Our advice is to plant a wide range of local, easy to grow native species. Planting designs can focus on understorey species, hedgerows or whole area plantings,” she said.

“In addition, diet needs and nesting substrate for volunteer pollinators can be provided in various ways. Decaying vegetation, bundles of sticks with pithy stems and old paddock trees can be used by flies, beetles and cavity nesting bees; Open, compacted well-drained soil can be used by ground nesting bees.