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Global insect populations have decreased dramatically over the past 50 years. This is mainly due to massive insecticide use and habitat loss caused by intensification of agriculture.
Up to 88 per cent of flowering plants and 75 per cent of commercial crops require insects for pollination, with honeybees and hoverflies most often doing the job.
But with declining numbers of these species, farmers may employ hives of bees to prevent crop yields falling.
Wild honeybees forage within three miles of their nest, and on return they perform the ‘waggle dance’ that advertises the location of productive foraging sites to other bees. Also, odours from scented flowers picked up inside the nest while unloading pollen act as cues to guide nest-mates to specific flowers.
Now scientists have artificially imprinted bees with flower odours in an attempt to improve crop yields*.
In trying to establish long-term memory for flower odours, the scientists offered bees in three separate groups of hives alternative odours: 1) sucrose solution scented with synthetic sunflower odours, 2) sucrose solution scented with jasmine odours, 3) sucrose solution alone. They then relocated the hives to a sunflower plantation and compared the foraging activities of bees exposed to the three solutions.
First, scientists decoded waggle dances to identify sunflower-specific dances. Using this information, they observed bees from hives fed with sunflower odours performing sunflower dances one hour after hive relocation.
Contrastingly, the control bees fed jasmine odours took 2-3 hours and control sucrose-fed bees took 5 hours to perform sunflower dances.
This resulted in the sunflower odour-imprinted bees performing significantly more sunflower-specific waggle dances during the first day of relocation, peaking at 84 per cent increase over control hives; preferentially visiting sunflowers and bringing in more sunflower pollen loads than the control bees.
The scientists then measured the all-important crop yields in five plots containing different sunflower hybrid plants pollinated by sunflower odour-imprinted compared to control bees.
Seed yields in all five plots were highest when pollinated by sunflower odour-fed bees, with increased production up to 60 per cent above control bees.
They conclude that providing bees pre-programmed to forage on specific crops could circumvent wild pollinator shortages and significantly increase crop yields.
*Current Biology 30, 1-7. 2020