Art Courtesy of Patricia Joseph.
While it may not be easy to teach bees to perform aerial acrobatics like in Cirque du Soleil shows, training bees to pollinate certain crops to improve agricultural yield has become a promising reality—so much so that it may be the solution to the growing threats facing our highly pollinator-dependent agricultural system.
Pollination is an invaluable service bees and a number of other pollinators provide to the Earth’s ecosystems. Approximately three-fourths of the Earth’s flora and one-third of agricultural crops, depending on the source, are pollination-dependent. This means just about every meal you eat is made possible in some form by pollinators. If they don’t pollinate crops, those crops generally can’t grow. To address the high demand for pollination in steadily expanding agricultural settings, considerable effort has been focused on harnessing pollinators and guiding them to specific crops. While some plans to direct pollinators have been more successful than others, one method in particular has generated a lot of buzz.
“The idea is that conditioning is a very useful procedure. And so, with this in mind, we asked the following question: Is it possible to train social individuals to a specific target crop?” said Walter M. Farina, a professor and insect physiology researcher at the University of Buenos Aires. “Under lab conditions we’ve obtained a really clear cause-and-effect relationship between training bee hives and bee foraging at specific flora. This will have positive outcomes for crop pollination and crop yield.”
Such an approach to increase agricultural crop pollination through “conditioning” bees is referred to as a targeted pollination strategy. This method aims to increase the pollination of particular crops by teaching bees to respond to certain stimuli like aromas that emanate from the target crop naturally. In a study Farina conducted on bees, he and researchers in his lab conditioned honey bees by exploiting their sense of smell, or olfactory discrimination. They did so by pairing a sugar-filled liquid with a synthetically produced scent that mimicked the natural aroma of a particular plant. By creating this aroma-reward pairing, bees were taught to target specified plants, such as almonds and apples. Previously, this aroma-reward conditioning strategy had only been applied to flora and agricultural crops that produce nectar, which is a natural food source many pollinators find delicious. Whether the targeted pollination strategy would hold for flora and crops without the natural reward of nectar was the next question Farina and his group would have to answer.
“The new challenge for us was how to approach other crops, because many of them contain no nectar. For instance, the kiwi fruit crop is not a huge temptation for honey bee colonies because they are nectarless flowers and do not offer an immediate reward for pollinators,” Farina said.
Farina’s group recently published their findings on this topic. In their study, they detailed how utilizing olfactory-conditioned bees to target nectarless crops may be just as feasible as conditioning bees to target nectar-producing flora. The researchers chose kiwi flowers as their nectarless target crop and produced six mimic odors of varying content to simulate the kiwi’s natural odor. Six groups of honey bees were initially conditioned over five trials with sugar-containing liquid scented with one of the six mimic odors.
“This absolute conditioning phase of the honey bees showed the potential of the mimic odors. If the mimic odor that we develop is really good, the bees not only learn during the conditioning phase, but also remember or, we say, generalize,” Farina said. “When we offer the natural fragrances of the male and female flower, the proportion the bees respond to is based on the quality of the mimic odor. From this, we find the best candidate for us to continue conditioning the bees.”
For the group of bees initially conditioned with the synthetic mimic odor named kiwifruit mimic odor (KM), over ninety percent of bees extended their straw-like mouth, called the proboscis, when subsequently presented with the sugarless, natural kiwi-scented liquid. This indicated the similarity between KM and the natural aroma of kiwi flowers. Now that part A of the research was completed, the researchers moved on to part Bee.
During the kiwi flower blooming season, the researchers in Buenos Aires conditioned bees at an orchard with sugar-containing KM. Following the conditioning period, the activity of the hive was quantified based on the number of bees that left the colony and the amount and type of pollen that the foraging bees brought back to the hive.
“In the blooming period of kiwi flowers, there are other blooming flowers containing nectar,” Farina said. The bees would be more attracted to the nectar-containing flora, so the number of bees that go to kiwi flowers will continuously decrease.
“But remember that the colonies of honey bees are around sixty to seventy thousand. With even ten percent or five percent of bee activity at the nectarless kiwi crop, that is a decent amount of activity still,” Farina said. “And when the food or other bioindicators are transferred from one individual to another, this will establish and promote long-term intensive activity onto the target crop throughout the hive.”
Despite the potential benefits of conditioning bees to target nectarless crops, it’s important to note that this strategy does not come without its drawbacks. Yes, conducting longer and more expansive studies involving conditioned bees will help to evaluate the efficacy of the mimic aroma and the potential of the target pollination strategy. And yes, developing synthetic aromas for various nectarless crops that bees are normally unable to distinguish other plants by scent is also a necessity. All of these are valid considerations that must be resolved before the findings from Farina and his lab are actually applied. But perhaps most important to examine when considering the future of this field is the danger that comes to bees when foraging on agricultural land.
“It is important to shorten the period in which bees are conditioned…[in order to] reduce the time bees are exposed to agricultural environments,” Farina said. “The use of agrochemicals and poor biodiversity…[make] these agricultural environments very disturbed and pose risks to honey bee health.”
If the targeted crop strategy is implemented, it is important to be cognizant of the underbelly of pollinator-based agriculture methods. If we aren’t cautious about how we augment the complex environmental systems of our world, we risk disrupting global ecology by debilitating the pollination activity of bees. On the other hand, there is also a possibility of improving agricultural productivity, even for nectarless crops that often go unforaged by pollinators, which provide an invaluable service to flora and to us.