You just let them smell the desired search object: According to the principle of training search dogs, bees can also be imprinted on certain crops, scientists report. By adding sunflower-scented food to the hive, they were able to give the insects a liking for the flowers of these plants. The bees then increasingly visited sunflower fields, where they ensured particularly intensive pollination and thus seed production. The concept could potentially also increase the yield of other crops that rely on insect pollination, say the researchers.
There’s pollen and nectar here! Plants convey this message with the colors, shapes and scents of their flowers. They want to attract pollinators, because bees, butterflies and the like ensure that the pollen grains are transmitted during their visits and thus ensure fertilization and seed formation. Many species are particularly dependent on these insect services, including important cultivated plants such as the oil-producing sunflower. If they are not sufficiently visited by pollinators, these plant species will produce fewer fruits or seeds and the yield will decrease.
Because of this, the human-induced decline in insect populations over the past few decades can pose a significant problem for agriculture. In addition to efforts to promote wild pollinator insects, some farmers are also trying to improve pollination by setting up beehives in the area of their crops. As the researchers working with Walter Farina from the University of Buenos Aires explain, their results could now help beneficial insects to perform this function even better – by encouraging them to prefer to fly to the respective cultivated plant.
Can defining fragrances be used?
The basis of the study was the natural ability of bees to memorize worthwhile smells: it is known that insects can learn that a certain flower scent is associated with high pollen and nectar yields. Ultimately, sunflower and the like exude their own special scents as attractants. As part of the study, Farina and his colleagues first produced a fragrance that corresponds to the smell of sunflower blossoms. They then added this substance to sugar solutions that they used to feed the bees in some of the test colonies. In control colonies, on the other hand, feed was used that was scented with jasmine flowers.
The scientists then carried out a series of experiments in the field with the colonies treated in this way. They set up the beehives about 600 meters away from a test field with sunflowers. The researchers used observations of the famous waggle dance as an indication of whether the bees are particularly attracted to these plants by their previous smell. With this behavior, after returning from a successful collection excursion, female workers give their colleagues on the floor flight instructions to the location of the lucrative source of food. Since the location information from the movements during the waggle dance can be decoded quite easily, the researchers were able to record where the bees were sending their colleagues.
Bees with a preference for sunflowers
It turned out that, in contrast to the controls, the position of the sunflower field during the waggle dance was conveyed much earlier and more frequently in the colonies with a sunflower scent. Further investigations confirmed that the bees of these colonies were particularly intense in the sunflower field and that they brought an above-average amount of pollen from these plants back into the hive. The bees of the control colonies, however, also visited other plant populations in the area of the hives more frequently, the scientists report. “We were able to show that honey bees can be conditioned to an odor, so that the odor-guided behavior is influenced,” Farina sums up.
As further investigations showed, the effect was also clearly reflected in the pollination performance and thus in the seed yield of the sunflowers. “Perhaps the most relevant result is that the feed preference for the target plants has been established for so long and intensively that it has led to a significant increase in crop yields,” says Farina. Sunflower fields that were in the range of “trained” bee colonies showed a yield increase of 29 to 57 percent compared to controls, report Farina and his colleagues.
The sunflower already represents an interesting target for the process because of its intensive need for pollination and its agricultural importance, say the scientists. But other pollinator-dependent crops could also benefit. The researchers’ goal is now to develop additional odorous substances to improve the pollination efficiency and productivity of many important agricultural crops. They are currently exploring the potential of the process for almonds, pears and apples, for example.
Source: Cell Press, technical article: Current Biology, doi: 10.1016 / j.cub.2020.08.018