Macadamia nut farmers go batty for birds

Green thinking: Environmentally-friendly control of macadamia nut pests could reduce product costs.

THE macadamia industry could save millions of rands by harnessing bird and bat power to control crop pests.

A collaborative research project between Green Farms Nut Company, four of its suppliers, the macadamia industry body SAMAC and the University of Venda is proving the commercial value to the industry of using bats and birds to control the stinkbugs, moths and nut borers that damage the crop.

The project has been designed and is being managed by the university’s South African Research Chair’s Initiative (SARChI) on Biodiversity Value and Change and results are based on the first year of the project, which covered the 2016 and 2017 macadamia growing seasons.

It is already clear that crop damage is increased when bats and birds are excluded from orchards.

Professor Peter Taylor, SARChI chair and supervisor of the project, said stinkbug damage to macadamia orchards in South Africa was estimated to be between R50- and R100-million per annum.

Economic models suggested current levels of stinkbug damage would double if bat populations in orchards were to become extinct.

Any efforts to retain bat populations, through use of safe pesticides, retaining natural vegetation corridors and bat houses, should be strongly encouraged.

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Green Farm Nut Company development and client manager, Graeme Whyte, said 60 to 80 percent of the damage to kernels delivered for processing in Limpopo and Mpumalanga, was due to stinkbug infestation.

Areas like KwaZulu-Natal were less affected by stinkbug damage but the stinkbug population there was growing. He explained that high levels of stinkbug damage to kernels increased production costs quite dramatically in many ways, including resulting in a slower ultimate flow of product to market, which impacted sales and, therefore, farmers’ profits.

Considering that pest control via bats and birds was free, there was no downside to doing the environmentally responsible thing. All farmers had to do was to place bat boxes in bat-friendly areas and to grow indigenous bush next to their orchards.

On six farms in the project, researchers have put up 48 cages around trees. One set of cages keeps birds and bats from feeding off the insects on and around the trees.

A second set enables both bats and birds to access the insects day and night. The third set of cages is closed in the evenings, to exclude bats and nocturnal birds. And the fourth set is closed in the day time, to exclude birds that are active in the day.

The nuts from the caged trees are then sampled to establish the percentage of damage caused by insects under these controlled conditions.

Researchers are also focusing on feeding patterns of bats and birds, using their droppings to establish which insects they are feeding on in the orchards.

This information will enable farmers to provide the right environment to encourage bird and bat species to develop colonies around their orchards.

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Biological control is expected to reduce the need for farmers to spray their trees, cutting production costs. With less kernel damage, a higher percentage of their crop will be processed for export.

Taken together, the savings on costs and the ability to market more of their crop is expected to make their operations significantly more sustainable.

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  AUTHOR
Judi Davis
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